The mountain communities are home to more animals than people in Colorado. Every Spring, we’re likely to see everything from foxes to moose in our yards and on our streets. About a month ago, I watched a juvenile (but plenty large) black bear on an evening walk in front of the houses in our neighborhood, peeking into the garbage bins lined up for pick-up the following morning.
Claire Tinker with her Dachshund Baxter on Bierstadt.
Dogs are natural companions to many up here as well, with plenty of space to run around, smells to sniff, and communities that seem to welcome their company indoors as well as out. Having seen so many of our dog friends on trails all across the state, we’ve wondered how they might be coping with the altitude.
Most recently, we ran into a German short-haired pointer named Moose on an ascent up Mt. Bierstadt, one of Colorado’s 14ers, sitting at 14,060 ft (4285 m). He and his human, Nick, moved to Colorado permanently about a year ago, after a two-week visit turned into several months.
Moose is 13 years old, Nick tells me, “but you have to believe that my dog acts like he’s 6.” Nick and Moose have been enjoying a lot of time outdoors together since moving to Colorado, and Bierstadt was their first 14er together, which they did with some other friends from Louisiana, where they’re from.
“It was awesome. Took [our friends] a long time to summit, but Moose did really well. He liked the breeze and the birds coasting right next to him. It would have been hard without a harness to [lead] him up to the top. He’s 65 lbs. Boulders weren’t too bad for him. Just have to be careful coming down, so he doesn’t slip and break a leg.”
Moose and his Louisiana posse on their way up Mt. Bierstadt.
This is a very legitimate concern. Many hikers have found themselves carrying their canine counterparts: they get tired, the terrain is difficult for them to negotiate or too rough on their bare paws, etc. You definitely don’t want to have your hands full as you ascend or descend a 14er.
Dr. Danielle Jehr, who has been a veterinarian with Frisco Animal Hospital for years after studying and practicing in Nebraska, also recommends waiting to take your puppy on the longer, more strenuous hikes.
Dr. Danielle Jehn with hiking and car ride enthusiasts Libby and Liam.
“Unfortunately, we do not get a chance to discuss this with many owners unless there are new puppy owners. Usually, we just see the aftermath from a hike and help guide them for future incidences. I would love to be able to tell all new puppy owners that activity needs to be limited up until 6-8 months of age while they are experiencing enormous amounts of bone growth. This means no major hikes on uneven surfaces and no 10 mile runs while the owner mountain bikes. We just want the pups to grow normally without complications for them or the owners.”
And as you might have speculated, animals are also prone to certain risks at high altitudes, although, “In general, healthy animals do not function any different at high altitude,” says Dr. Jehn. “Animals and pets with known blood pressure, cardiac or respiratory disease can decompensate at higher altitudes, and we do see this in practice. Just as human hearts have a difficult time at altitude, so do cats, dogs and livestock!”
Ike, about 8 months old, seriously reconsidering his choices on his way up Mt. Bierstadt.
So how do you know if your furry buddy is struggling with acclimation?
“Most often, an owner will call and have a presenting complaint of their pet experiencing exercise intolerance while on a hike or constant panting/lethargy/anorexia since the pet has been up in Summit County. If a dog presents in any type of respiratory distress, we place them on supplemental oxygen, check their heart and lung sounds, heart rate, respiratory rate, blood pressure and ability to oxygenate. We do this by utilizing a tool in the clinic that measures the percentage of oxygen carried in the blood.” Sound familiar? “We always want to see a dog at over 92%. If the dog or cat cannot maintain that or better without being provided oxygen, we need to see other diagnostics for reasons why.
“Common canine ailments we see that are drastically exacerbated by altitude are: cardiac disease (heart murmur, pulmonary hypertension, congestive heart failure), general hypertension, lung disease (asthma, allergic bronchitis) or vascular volume abnormalities (i.e. anemia).”
The most common injuries Dr. Jehn sees, she tells me, are “lacerations and abrasions from the rough terrain. We also see exacerbated lameness after hikes that are too long for our canine friends that are not otherwise used to it (i.e. 14ers).”
Nick and Moose currently live in Boulder, at 5328 ft (1624 m), but they moved there from a house in Bailey, at about 7740 ft (2359 m). I ask Nick if Moose has ever had trouble with the altitude since they moved to Colorado.
“Not at all. Not even when we first got here. He was ready to rock and roll. The only thing he didn’t like was the snow at first. Once he realized there were rabbits and stuff that went in the snow, he was about it.”
Being from Louisiana, one of Moose’s greatest challenges is the relative scarcity of water. Colorado doesn’t have as many lakes and ponds that Moose can cool off in and drink from, so Nick says he’s sure to carry water for him.
Nick also tells me that Moose is a pretty fit dog, and has never experienced any major health complications. He is careful, however, not to work him so hard that he’s limping the following day. I think it’s safe to say that’s something humans are wary of for themselves as well. If you’ve ever hiked a 14er, you already know.
Dr. Chris with grand-dog Ike on their way up Mt. Bierstadt.
Another factor that affects Moose and people alike is exposure. “If there’s no shade or wind, it’s a lot harder on him,” Nick notes. We also relate over the challenge of descending a mountain, when the resistance of gravity is especially stressful on your knees and hips. Nick works for Sacred Genetics, a company that cultivates feminized hemp seeds, who are partners with a company, Verdant Formulas, that specializes in CBD products, utilitzing the relaxing, remedial properties of the oil from cannabis. Among other applications, balms and oils infused with CBD have grown in popularity as a naturopathic treatment for muscle soreness and inflammation. Incidentally, more and more similar products are being marketed for the same afflictions in dogs. Nick tells me it helps with his own post-adventure soreness.
My main takeaway from all this insightful doggo dialogue is that we are all the more similar. It certainly seems like the same precautions apply for avoiding a serious situation outdoors. And don’t forget, if anyone in your party is having trouble on your hike, it is not advisable to continue; you are only as strong as the weakest member of your team, whether that is a dog or a person.
A last bit of advice from Dr. Jehn:
“I would also love to be able to tell all tourists to take it easy on their canine counterparts while visiting us in Summit County as well. Altitude sickness is real for humans and dogs, alike. Accomplishing a crazy hike with your dog should not be the first priority within the first few days at elevation. Dehydration and prior health conditions are real when experiencing altitude. If you know your dog has history of a heart or lung issue, especially, let them take it easy. We want you to enjoy Summit County for everything it has to offer….without the emergency visit!!”
Happy Trails, all you trailhounds and trail … hounds!
Roberto Santos on an epic powder day at the opening of The Beavers lift at Arapahoe Basin ski area.
Roberto Santos is from the remote island of Saipan, in the Commonwealth of the Northern Mariana Islands. He has since lived in Japan and the Hawaiian Islands, and has made Colorado his current home, where he is a web developer, musician, avid outdoorsman and prolific reader. When he is not developing applications and graphics, you can find him performing with the Denver Philharmonic Orchestra, snowboarding Vail or Keystone, soaking in hot springs, or reading non-fiction at a brewery.
Ski America is a company that has organized accommodations and itinerary for international athletes and vacationers at ski areas around Colorado since 1988. The Omori family, Ski America’s founders, lead their clients on tours of Colorado’s most renowned mountains, including Aspen (8,040 ft.), Vail (8,120 ft.), Beaver Creek (8,100 ft.), Copper (9,712 ft.), Keystone (9,280 ft.), Breckenridge (9,600 ft.) and Arapahoe Basin (10,780 ft.).
Ryoko and Jimi Omori
Jimi Omori started Ski America as a tour operator for Japanese skiers and snowboarders. Ryoko joined in 2005, and now Ski America’s service is more than tour operating, assisting from first-time skiers of age 3 to professional racers. With over 30 years of experience guiding amateur skiers and international athletes alike, the Omori’s have made some fascinating observations of how people adjust to the high altitude environment of the Rocky Mountains.
The other day, Ryoko shared some of their valuable insight and experience with me over a cup of tea:
How long do your clients typically stay at altitude?
So we have two different kinds of customers. In November until early December, we have a lot of Japanese racers from Japan. They are high school kids, college students. They stay two to four weeks here, in Frisco or Copper Mountain. Then, from December to April, we have clients from Japan who stay in Vail or Aspen. Most of them are senior skiers, over 60 years old. They stay about a week in Vail or Aspen. Six nights is very average.
How often do you get repeat customers?
Quite a lot. Not all of them come back every year, but more than once. I would say, 70%.
Do you see new customers every year?
Yes.
How do you advertise in Japan?
Word of mouth.
How do you prepare your customers for the altitude?
When I set up the reservation for them, I send them the lodging confirmation and shuttle confirmation, how to get to the Colorado Mountain Express counter at Denver International Airport. With that information, I also send how to get ready for this altitude by e-mail to every customer: Don’t stay up all night before coming over here, don’t overwork before coming here, most importantly, don’t catch a cold before coming over here. That’s the most important thing. And keep yourself hydrated on the flight and on the shuttle. You can always stop at a restroom on the way from the airport to get here. Do not drink a lot [of alcohol] on the flight, and especially on the first night staying here. I encourage them to drink two liters of water a day.
They are so excited to be here, so they tend to forget about the altitude, because there are all the trees, it’s not above the tree line here. In Japan, [this elevation] is way over the tree line. So I always remind them, “You are going to be almost [at the elevation of] Mt. Fuji. So, move slow the first and second day of staying here.”
What about conditioning, physical exercise to prepare? Are they athletic?
They’re pretty much athletic. They’re avid skiers. They ski in Japan regularly. So I do not give them any athletic advice in Japan.
Do they come straight from Denver up to elevation, or do they stay in Denver a certain amount of time?
No. The flight arrives at 12:30 or 1 pm, so it’s very convenient for them to get on the shuttle in the afternoon, and they will be here before 5 or 6.
Do they ski the next day?
Most of them, yes.
What about oxygen or medication? Do you ever tell them to bring ibuprofen or anti-nausea medication?
No. But if anything happens here, I recommend taking [something] for a headache, like Advil.
What is the earliest sign that something might be wrong or that they need medical attention?
Headache. Or sometimes nausea. We had 150 racers last November, and out of 150, I took 5 kids to the clinic for altitude sickness symptoms.
Is it at the beginning of their stay?
Very beginning. [Typically] the second day of skiing. They are okay on the first day. They do not notice anything on the first morning, so they feel, “It’s okay, let’s go skiing!” and spend the day on the mountain, and they have jet-lag, and they can’t sleep well on the second night. And on the second morning most of them notice the symptoms. Those are the Copper clients. And I have 350 guests from Japan staying in Vail and Aspen. Last year, I didn’t see anyone get sick. So it’s only in Summit County, because it’s much higher.
Do you think there are any other correlating factors, like their age or where they’re from?
Age. The racers are from middle school to college, so they’re young. Their hormone level is not stable. And they are staying with their other teammates, apart from their parents, so it could have some emotional factors affecting them, too. But at the same time, the racers have a lot of muscle that needs a lot of oxygen. The higher metabolism that younger kids have [make them] more prone to high altitude sickness. The clients who stay in Vail or Aspen, they are much older, like, 40s, 50s, 60s. And they’re not as athletic as the racers. They do not do any training. So their basic metabolism is low, so I believe they do not need as much oxygen.
Does anyone come from a high elevation in Japan, or is it mostly sea level?
Mostly sea level. Only some of them are from Nozawa, it’s about 1000 m (3,280 ft.), so it’s much lower than Denver.
Nozawa, Japan
Is there a difference between the guests that come from Nozawa and the guests that come from sea level?
No. Whenever I see the doctor in the ER, or the Copper clinic, they always say it’s dehydration. No matter how much we tell them to keep hydrated, it’s not enough.
So what does the ER or clinic often give them besides fluids?
Oxygen. And they say it’s okay to take over-the-counter headache medication.
How long is their visit to the hospital? Is it just a couple hours, or do they stay overnight?
Just a couple of hours, or less than that.
Do they ski the next day?
Most of the time, the doctors say not to ski the next day. We carry a pulse oximeter in our office. We have 20 of them. We do not do this for the Vail clients, because they don’t get altitude sickness. So we only do this for the guests staying in Summit County. When we [check them in], we distribute pulse oximeters, one per room. We encourage them to measure [their oxygen level] every morning. Then, after the doctor’s visit, the doctors say it’s okay if your oxygen level is over 90%, 20 minutes after getting off oxygen.
What’s the lowest you’ve seen the oxygen level on any of your skiers?
38. [He was] 15. He was at the ER. He was transferred to Denver by ambulance. He was there about three nights, and he went back to Japan.
Was that the only time somebody had to go back to sea level?
Yes. But it sounds like he had a heart issue, which we didn’t know [about].
Have you witnessed any other factors that help them acclimate more effectively?
I encourage them to eat carbohydrates instead of getting a lot of oily foods. If you have a lot of french fries, it’s very oily, it will take more time and blood to get to the stomach. So the blood flow doesn’t go through the brain [well].
What about caffeine or other holistic remedies?
No. We have some repeating guests who had … symptoms in past years, and we encourage them to visit a doctor in Japan [who] can prescribe … Diamox. One of the ski coaches [from Japan] … has to be here with his team. He has no choice. And he’s [had] a lot of altitude sickness in the past. So we told him, “You should see a doctor and get Diamox prescribed, and start taking it before leaving Japan,” and it’s been working great.
A young skier shreds her way down a snowy back bowl on a powder day.
Is there a routine that your clients do to prevent feeling this sickness?
Just check blood oxygen level every morning.
Of the clients that come here regularly, do they acclimate quicker each time?
They learn. We always see lower numbers of altitude sickness patients, because they learn what they need to do, like drinking a lot of water and checking their blood oxygen level. And only the numbers can tell. Even if they feel good, if the numbers are bad, if they go skiing, they will have a problem. Especially for the young kids. They [don’t] trust what you say. As the years go by, the coaches will learn, and the kids will learn what they can and what they cannot do.
Is there anything different about the philosophy of treatment in Japan vs. the US?
You know what, we do not have altitude sickness in Japan. Only if you climb up Mt. Fuji, in one day, it could happen, but not everyone does that. The highest elevation of one ski area in Japan is about 2000 m (6,561 ft.). No one has experienced high altitude sickness in Japan.
When I climbed Mt. Fuji, I saw a lot of people with cans of oxygen that you can spray. Do you ever use or recommend that?
No. I don’t think it works. If you breathe it for five minutes, it will work for five minutes. So I guess it’s very effective if a ski racer uses it right before the start [of a race]. I believe some of our Vail clients [have seen] the bottle and have purchased it, but I’ve never heard anything about it, good or bad.
Smiles and high spirits all around
In closing, I asked Ryoko if she’d noticed a change in her own physiology since living at high altitude, to which she replied that she is always impressed by her increased stamina and speed when she steps on a treadmill back at sea level. I asked her if she ever experiences symptoms upon coming back to a high altitude from sea level. “No,” she says, laughing. She doesn’t typically engage in any strenuous activity the first day or two after travelling, “because I’m lazy,” she says.
Roberto Santos is from the remote island of Saipan, in the Commonwealth of the Northern Mariana Islands. He has since lived in Japan and the Hawaiian Islands, and has made Colorado his current home, where he is a web developer, musician, avid outdoorsman and prolific reader. When he is not developing applications and graphics, you can find him performing with the Denver Philharmonic Orchestra, snowboarding Vail or Keystone, soaking in hot springs, or reading non-fiction at a brewery.
Dr. Christine Ebert-Santos recently sat down with Colorado Children’s Hospital’s Pediatric Emergency Medicine physician, Dr. Alison Brent, to share her experience and expertise in high altitude medicine.
After having practiced for decades in the Commonwealth of the Northern Mariana Islands, Dr. Chris opened her own practice in the high mountain community of Frisco, Colorado, where she has spent 20 years servicing natives, transplants and visitors alike. The mountain communities in Colorado are found at elevations higher than any others in North America, and are among the highest in the world. It has become her legacy to contribute to the research and improvement of medical practice in high altitude environments across the globe.
The full podcast episode from Charting Pediatrics can be found on Spotify, Google Play, and the Apple Podcast app.
Dr. Brent: “I know that sometimes in these South American countries, the high altitude illness impact for children can be even greater than what we see in the US.
Dr. Chris: Well, that’s where you get into ‘acclimatization vs. adaptation’. And what doctors in the United States need to know is that, just because a person lives at high altitude in the United States, we may be acclimatized, but we are not adapted, like the natives of La Paz and Nepal. So therefore we don’t have hundreds of generations changing their genetic adaptation to high altitude. We may have 20 years or 40 years. So the risks are still there.
Dr. Brent: Wow, it’s an amazing process. I know that when I moved to Colorado from flat-lander country, I found that there were just huge textbooks on high altitude illness. And it’s fascinating that you’ve taken this over as a very important part of your career.
Dr. Chris: Yes, well we have 5 million tourists every year coming just to Breckenridge, so it’s probably 10 million to Summit County. Plus, we take care of all the children in the surrounding communities, Park county and Lake county, which are higher: over 10,000 ft. So it’s very important to be aware of anything that can come up in both our visitors and our residents.
Dr. Brent: So this very important topic doesn’t just apply to practitioners who might live in Colorado or other mountainous areas. It really applies to practitioners all over the world who have patients who may travel to these areas. And with that in mind, when you have a practitioner and a family who live near sea level and they’re planning a trip to the mountains, how do they start to advise that family on how to get ready for a trip to a high altitude area?
Dr. Chris: I occasionally do get calls from physicians and families who are planning to bring their children, especially if they have a very young infant or a child with special needs. And so, things that I like to tell them are, Number One: If you could travel by wagon, train or mule, you would be best adapted to high altitude, because arriving to high altitude gradually helps your body adapt.
Second best to that is to stop over an intermediate altitude area. Fly into Denver and spend the night there before you come up to the very high altitude areas, especially Summit County. You start to get altitude symptoms around 8,200 ft. or 2500 m, which is the altitude of Vail. If you’re at a lower resort, most of the other resorts in the United States are below 8000 ft., and the risks of altitude illness are not as great. But the rewards of coming to the Colorado Rockies are also greater, because we have seven world-class ski resorts within an hour of where my office is, so it’s definitely worth it. Just arrive, take your time getting up there, relax, try not to do anything too strenuous the first day.
Consider taking Diamox or acetazolamide; the pediatric dose is 5 mg per kg per day, maximum of 125 BID. This has an effect of increasing your ventilatory drive, and definitely decreases the risk of acute mountain sickness when people come to visit the mountains. It’s best to start the day before, but even starting when you get up there works. And if you go to the Hypocrites app, you will find that it is listed for altitude sickness prevention.
Thirty to fifty percent of people visiting the mountains, especially when you fly right in and drive straight up, will experience some symptoms of acute mountain sickness, whether it’s a little nausea or vomiting or headache. So be prepared with some ibuprofen with dose appropriate to the age of the child, and Zofran would be a good thing to have in your pocket, too. It could save you a trip to the ER or doctor’s office. Because we’re just talking about the first 24 to 48 hours. If you could keep everybody in your travel team comfortable, you will have a great vacation.
Now, once you get there, or if you can before you arrive, we tell everybody, “You should have a pulse oximeter.” It’s just a little finger clip. At our office, they cost $17. Walgreens might sell them for $30 or $36. Knowing that oxygen level tells us everything.
You can call me anytime. I give my cell phone to all my patients, because … we need to know when someone’s oxygen is outside the normal range. If it’s below 90, we may want to see that child or even adult, because we do have family nurse practitioners, more urgently. And that is the key piece of information for knowing how sick someone is, and whether they need to be seen within a few hours or can wait until the next day.
Dr. Brent: Do you just prescribe oxygen if their oxygen saturation is low, or do you like to see them as well?
Dr. Chris: We can send oxygen anytime, day or night. We have three oxygen companies, and I can call them up and give them your number and location. I do, of course, want to see anybody that I’m prescribing oxygen for, but I may not have to see them in the middle of the night. Especially if everything sounds classic. My own patients that I’ve already identified as having a risk for Re-entry High Altitude Pulmonary Edema (R-HAPE), we can just set that up, even ahead of time.
Dr. Brent: You know, one of the things that I’ve noticed popping up in the mountains are oxygen bars, where, essentially, people can use an oxygen concentrator at a bar to relieve some of their symptoms. Should we think about preventative maintenance and getting people coming up here set up with oxygen before they come, or do you like to measure the oxygen saturation before you give oxygen? Because people say they just feel better having a little oxygen in the mountains.
Dr. Chris: Definitely the non-prescribed sources of oxygen, such as the canisters that you can buy in every store and the oxygen bars can help you with your headache and nausea. Use that for 10 or 20 minutes, feel better, that may be all you need.
Dr. Brent: And then what about the kids who you might see who have an oxygen saturation less than 90%, you see them in your office. How does the treatment plan roll out from there?
Dr. Chris: So the biggest concern we have is High Altitude Pulmonaryt Edema (HAPE). Now, don’t be scared, this is less than one percent of visitors, and probably between one and two percent of residents. The risk of developing HAPE is increased in anybody who has an inflammatory process going on, such as a cold or influenza. It definitely can occur in the first 24 to 48 hours in visitors, or even up to five days in our resident children who have a cold or some other underlying illness. So we do want them to have a pulse oximeter. This can develop fulminantly so that they’re doing fine for the first 24 hours or the first 4 days of their cold, and then all of a sudden, they kind of gas out, and they’re just lying on the couch and not eating well. Or it can develop very slowly.
So what we like to do if we know their oxygen is low, and whenever we see them in our office the first thing we do after the history and physical is to try an albuterol treatment and inhalation in case there’s some underlying broncho-constriction or asthma component. That would basically be most helpful in families with a history of asthma, or families that tell me they’ve used albuterol … before with that child or personally. It doesn’t usually change their need for oxygen. But it might help their cough.
However, once we do start somebody on oxygen in the office and call the oxygen company to set up a home concentrator, we see them back the next day and parents will tell me their cough was much better using oxygen. So oxygen is the main treatment. We are always thinking, “Could this person have pneumonia? Could this person have asthma?” Because of my experience at sea-level and taking care of very sick kids, if you have somebody with an oxygen level of 79 or 85, and they had asthma, you would certainly know that. You would hear some wheezing, there would be retractions, rails. They’d be in distress. If they had pneumonia, they’re sick, they’re not eating, they have a fever, you hear vocal changes in their respiratory findings. Most of these kids that we see, both the residents and the tourists with HAPE, we often won’t hear anything in their lungs, because children, how often can you get them to take a deep breath. And we often won’t see anything on the x-ray, so I don’t typically do an x-ray until the following day. If they’re not better and the parents are still concerned, we will do an x-ray. Often the x-ray won’t show anything. And this is where I’m hitting my head against the wall, and why it took me nine years to get my first publication. Because high altitude experts and all the pulmonologists are just freaking out that what I’m calling HAPE, or HARP, High Altitude Resident Pulmonary Edema, often does not show changes in the x-ray, and that I don’t do x-rays on all these hypoxic kids I see, because I know they’ll do fine if they just get some oxygen.
Dr. Brent: I love that approach of less is more, so we totally support that at Children’s Colorado. If you think a child has more than acute mountain illness and they actually have some degree of HAPE or HARP, how do you treat them differently?
Dr. Chris: Basically, oxygen. Now when a family arrives for their vacaction, and they’ve got, you know, ten family members in a condo, and one of the kids is sick, you know, we want to have a low threshold treatment. Influenza: we’re gonna put everyone on Tamiflu so that it doesn’t spread. You know, possible strep throat or is there any possible role for anti-biotics, we’ll have a low threshold.
And then we really sell them on the oxygen. You guys don’t have to leave. Your kid will adjust to the oxygen. We have things on our blog on how to keep your two-year-old from taking off their oxygen canula. That can save your whole vacation if you just understand that oxygen is the treatment, that you don’t have to go downhill.
Every once in a while we do have someone sick enough that we will send them down to Denver, directly to the hospital. But a lot of parents will ask me, “Well, what if I just take my kid instead of putting on oxygen, we’ll go down and check into a hotel in Denver?”
I’m not too happy with that, because I [say] you have to be under medical supervision, you have to know that your child’s oxygen is good once you get to Denver. As long as you’re here in the mountains, I’m your physician, you can call me anytime day or night, we can change our plan if it’s not working. If you’re in the condo and you don’t think your child is doing well, we can put your child in the hospital or send them down to a lower altitude if things are not going well.
Dr. Brent: So Chris, a lot of the literature does say that … one of the treatment plans would be to go to lower altitude, but you’re saying they can just stay in the mountains with oxygen and salvage their vacation.
Dr. Chris: Absolutely. We do it many times, every week at our clinic and in the emergency room. They do it every day, I’m sure.
Dr. Brent: Absolutely. Well, often times, when they do get down to see me in the ED, it’s a pretty easy diagnosis of, usually, some variant of acute mountain illness, and often times they’re better when they get to Denver from when they were up in the mountains. They may no longer have an oxygen need. And those kids who are then going to go back up, I hate to change anything that you or another pediatrician may have done, so we usually just keep them on their oxygen, and if the family wants to try going back to salvage their ski vacation, we let them do that.
Dr. Chris: As long as they have a home pulse oximeter, that little finger clip, they will know when they need to call someone.
Dr. Brent: That is wonderful. You mentioned a few of the co-morbidities that you worry about in children who may have an underlying influenza or some reactive airway disease. Are there other conditions, like kids with Down Syndrome or any other special groups that you worry about?
Dr. Chris: Definitely Down Syndrome children are a concern. Of course, I have many Down Syndrome children in my practice, and they do fine. But Down Syndrome children do have airway problems because of their hypotonia. So they’re more likely to need CPAP or have poor oxygenation during sleep. They’re more likely to have pulmonary hypertension or cardiac defects in general. And they also have increased pulmonary vascular reactivity. So … if you’re going to take a vacation and bring your child to altitude, make sure you have a pulse oximeter and that you are watching them very carefully for signs of decreased energy, poor feeding, color, anything that … is concerning that you as a parent are wondering, “This is not normal for them.”
All children, and even adults, when they come to altitude, they do have a decreased appetite. So that can last for months. Also sleep issues. There’s central apnea that is universal when anyone comes to altitude. Sleep is not going to be the same, and it takes a couple weeks for, actually, your sleep to adjust. But if it’s really interfering, and things are just not going well, we should take a look or consider whether that child is doing okay at altitude.
The other children who should not come to altitude are children who have a cardiac shunt with increased blood circulation in the lungs. That could really put them at risk for HAPE, and children with sickle cell disease. That can be really a crisis, even at altitudes as low as Denver, can cause a problem. So you need to be in touch with someone experienced with your condition if you want to travel with those conditions.
I have read in … articles by Peter Hacket and the other altitude experts not to bring children who are less than six weeks old up to altitude. Here’s the issue: you have a family wedding, everyone’s going there, you want to bring your new baby, they’re probably going to do fine. So I would say, just know where your local pediatrician that you can call anytime day or night is, and that baby will probably be fine.
Dr. Brent: Would you say the same for premature infants?
Dr. Chris: Premature infants, they are probably going to be okay. Once again, we have babies who are born in Denver and come home a few days or a few weeks into their early life experience, and we just check their oxygen in the office, or we can send a respiratory therapist from the oxygen company to their house to check their oxygen. And that is the best way to really keep track of what’s going on. Because babies are used to being in a low-oxygen environment. Remember, the uterus, the womb is like Mt. Everest. The oxygen saturation is 40 – 60%. So they don’t tell us that they’re having oxygen problems. They’re not breathing hard, they’re not retracting, they’re not coughing. They’re just mellow, but they may not be feeding well, so we want to check their oxygen by measuring it.
Right now we don’t have inexpensive ways of measuring oxygen in infants less than one year, but I’m sure that’s coming through very soon. The Owletis out there, we haven’t found that really reliable at high altitude. But we will be able to measure babies’ oxygen in our office, and sometimes, we will send families home with one of our infant pulse oximeters if we have concerns, and it’s night-time or weekend, and we can spare that piece of equipment.
Dr. Brent: I know we’ve talked about HAPE. Let’s talk a little bit about HACE, or High Altitude Cerebral Edema, which my understanding is just a part of the spectrum of acute mountain illness where you get some vaso-dilation going on in your brain and this can be even worse. How do you evaluate and then treat patients, especially kids you think may have some HACE?
Dr. Chris: So, diagnosing HACE in children, I don’t even know of a case. Because it mostly occurs above 15,000 to 17,000 ft. That is the flurid adult onset where they have trouble walking, talking, thinking, and you’ve got to get them down the mountain as soon as possible. However, the acute mountain sickness HAPE and HACE spectrum, it’s probably a continuum.
So there’s recently an article in the Journal of High Altitude Medicine and Biology or on the Cerebral Volume. And some people have more or less space around their brain. So does their brain expand under the influence of high carbon dioxide from increased ventilation or low oxygen, and that causes the headache and the nause and the vomiting, and is that an early spectrum of HACE that you can treat with oxygen? Babies who are very fussy, just can’t calm them down, just not eating: are they having a form of Cerebral Edema, that they would feel better with oxygen? We really don’t know, but those are things that there are a lot of research going on and providers should think about when somebody gives us a call or comes through the door with their child.
Dr. Brent: That’s good to know. And I know that you have your own practice here and specialize in taking care of kids, so let’s switch gears a little bit to kids who actually live at altitude. There’s so many problems I know at altitude. I think some of the smallest babies in the country are born in Leadville, CO. So how do you handle some of these kids? What are the problems you see? Is it worth the tradeoff to have a small baby who may not grow so well, but to live in the splendor of Colorado?
Dr. Chris: Well I just came back from the Chronic Hypoxia Conference in La Paz, Bolivia, where there were researchers from sixteen different countries, and one of the things that I learned there is that one reason that newborns can tolerate hypoxia during a difficult birth or resuscitation is because they’re coming from a chronic hypoxia environment. And their metabolism and their chromosomes and mitochondria are all switched on to a low-oxygen environment. And that helps them during the first couple weeks of life. So we actually say that probably the detrimental part of living at high altitude is more than counter-balanced by the increased health that we have, decreased myocardial infarctions, decreased strokes, longer active lives. But specifically in our newborns, they have decreased birth weights of about one ounce per every thousand feet of elevation. So our newborns are more likely to be 5.5 to 6.5 lbs. rather than 7.5 to 8 lbs. And about one third to a half of our newborns go home on oxygen based on pulse oximetry studies in the nursery that are less than 90. The Heart Association or the cardiac screening is not even done in our nursery. We are … the exception of the world, because we would have to do an echo- on every baby that we see. So most of these babies go home on oxygen, but I see them in the office when they’re three or four days old, another half of them their oxygen is fine and we tell the parents, “Okay, you can have them off oxygen, but we’ll check them one more time at two weeks before we have the oxygen company pick up the tanks.” So I very rarely have children, newborns, that are on oxygen for more than two weeks. That being said, nobody really knows what’s normal. If I have a child living at 11,000 ft., should that baby be held to the same standard as the kids in Kremmling at 8,000 ft.? Or in Frisco at 9,000 ft.?
We are planning a newborn oximetry study, and we’re in contact with some of the medical device manufacturers to try and get some equipment loaned, so that we can send this home with parents and find out what is normal, and establish our own normal. My normals are based on 19 years of clinical experience. If a baby meets 89 to 90 in my office during a clinical exam while they’re quiet or sleeping or breast feeding, I will tell the parents they don’t need oxygen.
The concerns we have is if the baby is at home for long period of time with low oxygen, the changes that are supposed to take place in the heart and lungs, such as the closing of the PDA and the decreased muscular lining of the pulmonary arteries may not proceed the way they are supposed to. And that process can take up to four months. So that’s why we don’t want to leave our infants with oxygen below 89 for long periods of time. We’re not worried about a few days or a few hours, the oxygen tank runs dry or the canula falls off. We’re not worried about brain damage.
We certainly know … — I’ve been a pediatrician for 40 years — my first 20 years as a pediatrician where we would have parents who refuse surgery for their cyanotic children, and they’d be going to second grade and you wouldn’t know there was anything wrong with their brain, they’d be blue as could be. So those are the concerns that I must address with all parents, because they are going to be terrified about this.
The next thing that is going to cause an issue with these newborns is the grandma in Florida is going to absolutely freak out that her little grand-baby is on oxygen because nobody else in the world understands our situation. We have 30,000 people living in Summit County with 5,000 in each of the surrounding counties, and another 60,000 in Eagle county. Outside of that, there aren’t any communities in North America at this high elevation. So we are the only ones who really have to deal with this. The rest of the doctors and family members are totally mystified by what we’re doing.
The second thing is, not only are they born a little smaller, but we have twice the number of children who are below the normal percentiles on the WHO and CDC growth charts during the first two years of life. So instaed of three percent, we have seven percent. What that tells me is that the whole growth percentile thing is probably shifted downward. We have just analyzed 30,000 data pieces from growth charts from our clinic and the Community Care Clinic in Summit, with the help of the Minnesota Department of Epidemiology, and we are hoping to publish our own unique high altitude growth charts.
The reason this is important is because when our children come down to see a specialist at Children’s Hospital, they get told that they are not feeding their children, and that their children need to see an endocrinologist and have $2000 worth of tests done. Whereas, after my first five years as an experienced pediatrician working with feeding specialists and OT’s watching these kids grow, I decided these were normal, healthy mountain kids. Very important information.
Dr. Brent: And so, Chris, do these kids eventually catch up by the time they’re 8, 10, 12, 16, adults?
Dr. Chris: They catch up by the time they’re 2.
Dr. Brent: By the time they’re 2, perfect. So they’re not shorter than the rest of the kids in the country.
Dr. Chris: Not at all.
Dr. Brent: Just wanted to make sure. Otherwise you might not have such a huge influx of people coming in to Colorado. Anything else you’re concerned about or have to do anticipatory guidance for for kids born in Colorado?
Dr. Chris: In our population, we also see children who have Re-entry HAPE. So during spring break, they go down to visit grandma in Florida, and when they come back they have a cold, and that night, the mom calls me and says, “Oh, he’s coughing and he sounds really congested.” Well, that’s my clue that probably lungs are filling with fluid and that child needs oxygen. So we want people to be aware of that who do live at altitude.
The other thing that I’m just starting to explore is we had a case of a post-traumatic HAPE, where a student from the mountains was going to school in Denver and was hit by a car and had three broken ribs. He was hospitalized in Lakewood overnight, he had a scalp laceration, he had x-rays and CAT scans that did not show anything in the lungs. So he left the hospital at noon the next day with an O2 sat of 94. By 10 ‘o clock that night, his oxygen was 49. He had rails in both lungs, however the x-ray did not show fluid. The emergency room doctor in Summit diagnosed Re-entry HAPE, he was sent back down to Lakewood. He was on 20 liters of oxygen. He was in the ICU, he had a CT scan, which also read as normal, and by the morning, he was on 4 liters of oxygen.
Now, to me and to that ER doctor, the only thing that this could be is HAPE. However, once again, I can’t get this past the high altitude experts and pulmonologists with normal imaging. So I’m throwing a question out there. We need to be sensitive to and start to discover whether there are cases of post-surgical, post-traumatice HAPE. I hear the stories, and that brings us to the blog.
The blog at highaltitudehealth.com. So as I said, it took me nine years to get my first paper published. However, in the blog, you can publish anecdotal and personal stories of your experience with altitude. And it’s out there for people to read and say, “Oh! Maybe that’s what’s happening to me or to my child. Or maybe I should know about that before I make my trip to altitude. Or maybe I should know about that with these children who are coming down to see me from altitude.”
So I highly recommend that anyone who’s interested or visiting or living at altitude read our blog, highaltitudehealth.com. And you can get some ideas and you can make some comments and give us your ideas. And that can lead to further study and research and help us understand these situations.
Dr. Brent: That is a wonderful resource for everyone, and I would hope that our listeners and our Charting Pediatrics family all over the world listen to this. There are so many children that I see in the ER, and when I mention that I think that they have some kind of acute mountain illness, they look at me like I’ve got a fork coming out of my head. They’ve never heard the concept, and … like, “How can my kid be fussy and not eating and not sleeping, and why …?” And they don’t know that. So I think the more we can get the information out there, that would just be wonderful. So glad you’re doing this. I do think that, personally, I get a little bit of re-entry illness everytime I drive from Denver to Vail. I come down Vail pass, I get a little queasy, I get a little headache, and it takes me … a day or two to get back on track, then I’m right back down to Denver and all my symptoms are gone. So, crazy that after 15 years, I still have my little own issues with altitude in this …
Dr. Chris: Well, I have an interesting anecdote that I haven’t put on the blog yet. I made a presentation to our first line, first-responders, and someone came up to me and said that he works in Denver, so he reverse-commutes. And every time he came home on weekends, he would be sick. His primary care physician in the mountains put him on acetazolamide. And that took care of his symptoms. So he’s kind of on chronic acetazolamide, which we’re seeing more and more that this is a very safe medication that you can take when you need it. It doesn’t have to be before you arrive, it can be after you arrive, it can be five days after you arrive. If you’re not sleeping well, you can try this. The only side effects are tingling in the hands and feet, and a very bad change of taste for carbonated beverages.
Dr. Brent: That could be a good thing. I think, I know when my physician talked to me about Diamox, she had mentioned that some of the side effects are headache and GI distress, which is what I had anyway, and I thought, well, why would I want to take a medicine that the side effects are the same as the disease. But you’re saying you don’t see that very often.
Dr. Chris: I have not seen that at all.
Dr. Brent: Excellent. And no issues with kids either. Do you think that, when I see kids in the ER who have some acute mountain illness that I should be starting Diamox at that low dose? The 5 mg per kg on those kids as well?
Dr. Chris: Yes, it doesn’t hurt. And it’s definitely empowering to parents. Just like, for parents to know that they can call me on my cell phone. For parents to know that there is a medication they can give. They may not need to give it, like we give anti-biotics and say, “Okay, if their ear pain gets worse, start the anti-biotic.” More than half of them will never give that anti-biotic. But having the ability to treat your child, you feel so helpless when people are uncomfortable or sick or suffering around you, but having the ability to give them a very safe medication or call somebody for information can really give them a lot of peace of mind.
Dr. Brent: And so my overall message I’m getting from you is really one of empowerment for families taking care of their kids, that there are so many solutions. They can keep their vacation. But the mainstay is oxygen, and in your back pocket you have a little Diamox, and maybe a little Zofran.
Dr. Chris: Yep. And ibuprofen.
Dr. Brent: And ibuprofen. Excellent. One quick question: Is there ever a role for inhaled steroids if there’s some inflammation going on ? You talked about a trial of albuterol.
Dr. Chris: My families whose children have had recurrent HARPE have told me that they do not feel that adding steroids has helped. Now, that being said, all the kids — and I see 30 – 40 cases per year of mountain resident children who have a hypoxic episode during an illness and have to use home oxygen — if they have more than one episode, we do refer them to the cardiologist that comes quarterly to our office to have an echo- at high altitude to rule out any hidden cardiac shunt that could predispose them. But many of these parents will self-refer to one of the many fine pediatric pulmonologists at National Jewish or Children’s Hospital. And when they go there they will inevitably be told that their child has asthma and needs to be on inhaled steroids. They will be on inhaled steroids for a year, and they will not have any more episodes, which they were not going to have anyways. So, there you go.
Dr. Chris at Children’s Hospital in Denver
Dr. Brent: I love that answer.
This has been such a wonderful talk. In closing, I love to ask this of each of our guests here: What is the most rewarding aspect of your practice?
Dr. Chris: My relationship in the community and with the families is so special, because of the small size of our community. I am able to give my cell phone to the families, and I only get a few calls a week. I might be in my office, suturing up a three-year-old and save them the cost of going to the ER, you know, once a month or every second month. But because of this low-oxygen issue, I just feel that it’s important that we touch bases and have access to understanding what’s going on with both children and adults in our community. And I also have appreciated texting, because it’s less invasive, so it’s something that’s not urgent, like a rash or an eye discharge, my patients will text me or sent me pictures. and we are having a Telehealth app coming into our practice too, so that will make it more HIPA-compliant, and more comprehensive care for the Ebert Family Clinic.
Dr. Brent: Well, hopefully we can get all of you at the Ebert Family Clinic on Tiger Connect, and solve all your problems at once. But, Dr. Ebert-Santos, it has been such a pleasure to have you on the podcast today. Your passion is palpable, what you do has such a wonderful impact on kids and their families, not only in Colorado, but those visitors who can salvage their vacation to our beautiful state because of the the things you do. So on behalf of ChartingPediatrics, thank you, and hopefully we can have you on for a follow-up episode sometime in the near future.
Dr. Chris: Yes, when we finish these research studies on newborn hypoxia and normal oxygen values in adults, we’ll have more to tell you.
Dr. Brent: Well, you are on, and we can’t wait. And until next time, keep on keeping kids safe out there!
You step out of your car at roughly 9,000 feet in Frisco, Colorado, and the first thing you notice isn’t the mountain views –it’s your breath. It comes faster, deeper, almost as if your body knows something you don’t: the air pressure here is lower and each breath delivers ~28% fewer oxygen molecules than at sea level1. This “thin air” triggers the same hypoxic (low-oxygen) stress that Mars settlers will face, where every habitat and spacesuit must carefully control both pressure and oxygen1,2,7,8. On Mars, the atmospheric pressure is less than 1% of that on Earth.
Acclimatization
On your first hike, your heart pounds harder than usual. That’s your body’s rapid response: breathing quickens, heart rate rises, and oxygen delivery ramps up to keep the entire body going1,2,4. Within 24-48 hours, your kidneys release erythropoietin (EPO), signaling the bone marrow to make more red blood cells1,3. This raises hemoglobin levels, enhancing oxygen transport. Over the following weeks, blood volume and hemoglobin continue to rise1,2,4. This is acclimatization –which varies between individuals, an important consideration when selecting crew for long-duration Mars missions.
Sleep and Oxygen
At night, breathing becomes fragile. Many people develop “periodic breathing” –brief pauses that fragment sleep. Summit County residents often experience oxygen dips into the high 80% –lower than the ~90% seen in Denver; and far below the typical 96-98% at sea level1. These dips have real implications: hypoxia combined with sleep disruption can affect mood, stress, and cognitive performance, as seen in Antarctic “winter overs,” where low oxygen and isolation caused up to 20% drop in certain cognitive task speeds and increased mood disturbances. Altitude sleep data are useful for researchers to determine extra nighttime buffers and habitat controls. Predicting and mitigating these person-specific patterns is key for astronaut safety and performance4,5.
From Frisco to the Final Frontier
Frisco, Colorado is not just known for its scenic views. This mountain town serves as a “living laboratory”, allowing researchers to track oxygen saturation, breathing, heart rate, sleep, and exercise tolerance in residents and visitors. These insights can help engineers determine how much oxygen a Mars habitat should provide, and how quickly conditions can safely change after landing1,2,7,8. NASA spacecraft air pressures currently range from 8.2 – 14.7 psi, with oxygen comprising 21-32% of that air; parameters informed in part by high-altitude research7,8. At the 7th Chronic Hypoxia Symposium in La Paz, Bolivia at 12,000 feet elevation (3,640 m) the use of insights from high altitude populations to enable the exploration of Space was discussed. The sponsor and organizers were Drs. Gustavo Zubieta-Calleja and his daughter Natalia Zubieta De Urioste who run the Institute of High Altitude Pulmonology and Pathology there. Presenters and attendees came from 16 countries covering topics ranging from molecular biology to genetics. A presentation on “BioSpaceForming” identifies chronic hypoxia as a “fundamental tool” that “gives humans and other species an advantage on earth and beyond.” Dr Zubieta explained that the space station is engineered to have the barometric pressure (760 mmHg) and oxygen content of sea level. When the astronauts change into their space suits to work outside the ship they experience a pressure drop of over 200 mm Hg in a laborious process of donning the suit. Seeing that millions of inhabitants are healthy at 486 mm HG in Bolivia, he advocates that maintaining lower pressures and lower oxygen levels in the space station would be economical and promote the health of the astronauts. Several altitude scientists see this as a future that “uncouples biology and physics.
(Photo of Dr Gustavo in front of space slide)
Modeling Mars Conditions
Researchers combine data from high-altitude locations, Antarctic stations, Mars-analog habitats like HI-SEAS in Hawaii to build predictive models. These models provide guidelines for when oxygen supplementation or workload adjustments are needed to optimize safety while completing tasks 4-6,9. They also help develop “operations playbooks” for simulating life on Mars10; set habitat air pressure and oxygen guidelines7,8; define spacesuit safety limits4,6,11; and better understand how the human body responds to spaceflight and space living2,5,9,12,13. For example, extravehicular activity (EVA) suits –spacesuits used for work outside the spacecraft –typically operate at ~4.3 psi with 100% oxygen. While this allows astronauts to breathe in low-pressure environments, prolonged use can lead to overheating, dehydration, and higher risk of injuries11.
The gravitational pull is 38% of that on Earth. Solar and the more dangerous Galactic Cosmic Radiation of Alpha particles from distant supernovae is hundreds of times greater than on Earth, due to the lack of a magnetic field or protective atmosphere. A breeze on Mars could barely move a blade of grass. Global dust storms occur every few years and last months, devastating the surface.
At the 9th Chronic Hypoxia and First International Space Physiology Symposium in La Paz, Bolivia in 2025 Dr. Akbar Hussain presented his Craterhab design for accommodations in austere high altitude environments and eventually on Mars.
(PHOTO akbar in front of slide with craterhub)
Astronauts could be acclimatized before embarking on the long journey to distant space in facilities located at 5,000 meters near mines in the Andes.
(Photo of Dr Gustavo in front of space slide)
Limitations
Most high-altitude studies are conducted over weeks to months, while Mars missions could last years and require hundreds of participants to have the skills to be self-sustaining. Due to planetary rotations, travel to Mars is only feasible once every 26 months. Messages from Mars take 7 to 45 minutes to arrive on Earth. Individual differences in acclimatization, long-term cognitive effects, and combined stressors like radiation or microgravity are not fully captured. Longer-duration studies at high-altitudes, combined with simulated Martian habitats and spacesuit trials, are needed to refine safety parameters.
Conclusion
High-altitude research gives scientists a window into human maladaptive and adaptive responses to low-oxygen, low-pressure conditions on Earth, and is directly relevant to anticipating health risks and necessary countermeasures for human habitation on Mars.
References
Ebert-Santos C. High-Altitude Pulmonary Edema in Mountain Community Residents. High Alt Med Biol. 2017 Sep;18(3):278-284. doi: 10.1089/ham.2016.0100. Epub 2017 Aug 28. PMID: 28846035.
Le Roy B, Martin-Krumm C, Pinol N, Dutheil F, Trousselard M. Human challenges to adaptation to extreme professional environments: A systematic review. Neurosci Biobehav Rev. 2023;146:105054. doi:10.1016/j.neubiorev.2023.105054.
Mairesse O, MacDonald-Nethercott E, Neu D, et al. Preparing for Mars: Human sleep and performance during a 13-month stay in Antarctica. Sleep. 2019;42(1). doi:10.1093/sleep/zsy206.
Pagel JI, Choukèr A. Effects of isolation and confinement on humans—Implications for manned space explorations. J Appl Physiol (1985). 2016;120(12):1449-1457. doi:10.1152/japplphysiol.00928.2015.
Dunn Rosenberg J, Jannasch A, Binsted K, Landry S. Biobehavioral and psychosocial stress changes during three 8–12 month spaceflight analog missions with Mars-like conditions of isolation and confinement. Front Physiol. 2022;13:898841. doi:10.3389/fphys.2022.898841.
Waligora JM, Horrigan DJ, Nicogossian A. The physiology of spacecraft and space suit atmosphere selection. Acta Astronaut. 1991;23:171-177. doi:10.1016/0094-5765(91)90116-M.
Morgenthaler GW, Fester DA, Cooley CG. An assessment of habitat pressure, oxygen fraction, and EVA suit design for space operations. Acta Astronaut. 1994;32(1):39-49. doi:10.1016/0094-5765(94)90146-5.
Sarma MS, Shelhamer M. The human biology of spaceflight. Am J Hum Biol. 2024;36(3):e24048. doi:10.1002/ajhb.24048.
Lim DSS, Abercromby AFJ, Kobs Nawotniak SE, et al. The BASALT research program: Designing and developing mission elements in support of human scientific exploration of Mars. Astrobiology. 2019;19(3):245-259. doi:10.1089/ast.2018.1869.
Stirling L, Arezes P, Anderson A. Implications of space suit injury risk for developing computational performance models. Aerosp Med Hum Perform. 2019;90(6):553-565. doi:10.3357/AMHP.5221.2019.
Cassaro A, Pacelli C, Aureli L, et al. Antarctica as a reservoir of planetary analogue environments. Extremophiles. 2021;25(5-6):437-458. doi:10.1007/s00792-021-01245-w.
Fairén AG, Davila AF, Lim D, et al. Astrobiology through the ages of Mars: The study of terrestrial analogues to understand the habitability of Mars. Astrobiology. 2010;10(8):821-843. doi:10.1089/ast.2009.0440.
Akbar Hussain M, Ayaz Hussain M, Mehdi Hussain M, Fatima R, Carretero R, eds. Craterhab Technology: Adapting Martian Habitat Systems to Combat Chronic Hypoxia in High-Altitude Mining in the Andes – A White Paper. Mareekh Dynamics. Published June 3, 2024. Accessed August 15, 2025. https://www.mareekh.com/post/craterhab-technology-adapting-martian-habitat-systems-to-combat-chronic-hypoxia-in-high-altitude-mi
My love for hiking developed during my childhood explorations of the breathtaking landscapes of the Sierra Nevada. As I ventured into the rugged mountains and hiked along scenic trails, I couldn’t help but feel a deep connection with nature. However, my passion for hiking was not without its moments of caution. On several occasions, I witnessed the awe-inspiring yet intimidating power of lightning storms dancing across the vast mountain skies. These encounters instilled in me a profound curiosity about the risks associated with lightning strikes in high-altitude regions.
When I moved to Colorado for PA school, my awareness of the dangers posed by lightning strikes grew even stronger. The dramatic topography and frequent thunderstorms in Colorado amplify the risk for individuals exploring high-altitude areas. It was during my last clinical rotation at a burn unit that I had the opportunity to care for several patients who had been struck by lightning. Witnessing the effects firsthand fueled my determination to educate the public about the actionable steps they can take to stay safe during lightning storms.
Lightning strikes
Lightning possesses an immense amount of energy, with a voltage of over 10 million volts (in comparison, most car batteries measure 12.6 V).1 Additionally, a lightning bolt reaches incredibly high temperatures, reportedly up to 30,000 Kelvin (53540.33 F).1 Lightning injuries occur in different ways, including as direct strikes, side splash, contact injuries, or ground current.
Direct strikes are uncommon, accounting for only 5% of cases, and happen when a person is directly struck by lightning.2
Contact injuries occur when a person touches an object that is struck by lightning. 2
Side splash injuries occur when the current jumps or “splashes” from a nearby object and then follows the path of least resistance to reach the individual. These injuries make up about 1/3 of all lightning related injuries. 2
Ground current is the most prevalent cause of injury, accounting for half of all cases, and occurs when lightning strikes an object or the ground near a person and subsequently travels through the ground to reach the individual. 2
In Colorado, an average of 500,000 lightning flashes hit the ground each year. Based on data since 1980, lightning causes 2 fatalities and 12 injuries per year throughout the state.3According to data since 1980, lightning causes an average of 2 fatalities and 12 injuries annually throughout the state.3 Colorado ranked third in the United States for the number of lightning fatalities between 2005 and 2014, as depicted in Figure 1.
Fig. 1. Lightning fatalities by state. 3
The high number of injuries attributed to lightning in Colorado can be influenced by several factors. One of these factors is the easy access to high elevation terrain, such as 14ers (mountains with a peak elevation of at least 14,000 feet). This accessibility allows inexperienced outdoor enthusiasts to venture into potentially dangerous situations due to their lack of knowledge and preparation.
For instance, individuals who are not familiar with summer weather patterns may embark on a hike above the tree line late in the day, underestimating the risk of a storm forming. This lack of understanding puts them in an exposed and perilous position should adverse weather conditions arise.
Even with thorough preparation and extensive knowledge of weather patterns, it is still possible to find oneself in a situation where you have to weather a storm. Given that a significant proportion of Colorado’s hiking trails are located above the tree line, where appropriate shelter is sparse, hikers are more susceptible to lightning strikes in these exposed areas.
Pathophysiology of Lightning Strike Injuries
The overall ratio of lightning injuries to deaths is 10:1 and there is a 90% chance of sequelae in survivors.4 The primary mechanism of injury in lightning strikes is the passage of electrical current through the body. The high voltage and current can cause tissue damage through several mechanisms, including thermal injury, electrical burns, and mechanical disruption of tissues. The severity of the injury depends on factors such as the voltage and current of the lightning bolt, the duration of contact, and the pathway the current takes through the body.
Lightning strikes can cause various types of injuries, with cardiac and respiratory arrest being the most common fatal complications.5 The path of least resistance determines the flow of electricity through different organs in the body, with nerves being the most conductive, followed by blood, muscles, skin, fat, and bone. 5 When lightning strikes, the electrical surge can induce cardiac arrest and cessation of breathing by affecting the medullary respiratory center. As a result, most patients initially present with asystole and may progress to different types of arrhythmias, commonly ventricular fibrillation. 5
Interestingly, there have been case reports documenting successful resuscitation of lightning strike victims who were initially apneic and pulseless for as long as 15 to 30 minutes. 5This has led to the recommendation that in the immediate aftermath of a lightning strike, individuals who appear to be dead should be prioritized for treatment.
Superficial skin burns are experienced by around 90% of lightning strike victims, but deep burns are less common, occurring in less than 5% of cases. A characteristic skin manifestation of a lightning strike is the Lichtenberg figure, which is considered pathognomonic. Neurological symptoms can also occur, including keraunoparalysis, which is a transient paralysis affecting the lower limbs more than the upper limbs. This paralysis is often accompanied by sensory loss, paleness, vasoconstriction, and hypertension, and is thought to result from overstimulation of the autonomic nervous system, leading to vascular spasm. In most cases, this paralysis resolves within several hours, but in some instances, it may last up to 24 hours or cause permanent neurological damage. 5
Additionally, it is common for lightning strike victims to have a perforated tympanic membrane (eardrum) or develop cataracts immediately following the incident. These injuries to the ear and eyes are associated with the intense energy of the lightning discharge.6
What can hikers do to stay safe?
Preparation
Monitor weather forecasts: Stay updated on weather conditions before engaging in outdoor activities, especially in areas prone to thunderstorms. Pay attention to thunderstorm warnings or watches issued by local authorities. Having a mobile or handheld NOAA Weather Radio All-Hazards (NWR) can also be helpful as it can transmit life-saving weather information at a moment’s notice.
In Colorado most thunderstorms develop after 11 am, so it is best to plan your trip so that you are descending by late morning.7Fig. 2 shows number of lightning fatalities by time of day in Colorado between 1980 and 2020. The vast majority take place after the 11 am threshold.
Fig. 2 Lightning fatalities in Colorado by time of day3
What to Do If Caught in a Storm
If you can hear thunder, you are close enough to be struck by lightning. Lightning can strike up to 25 miles away from the storm. 7 Once you hear thunder, if possible quickly move to a sturdy shelter (substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up). Avoid small shelters, such as picnic pavilions, tents, or sheds. Stay sheltered until at least 30 minutes after you hear the last clap of thunder.
Fig 3. Areas to avoid when sheltering from lightning.
If you are outdoors and cannot reach a suitable shelter, avoid open areas, hilltops, and high places that are more exposed to lightning strikes. Seek lower ground and stay away from tall objects, such as trees, poles, or metal structures. Bodies of water, including lakes, rivers, pools, and even wet ground, are conductive and increase the risk of a lightning strike. Move away from these areas during thunderstorms. Separate group members by at least 20 ft as lightning can jump up to 15 feet between objects.
If a strike is eminent (static electricity causes hair or skin to stand on end, a smell of ozone is detected, a crackling sound is heard nearby), the current recommendation is to assume “lightning position”, pictured in Fig. 4.
Fig. 4. Lightning position8
To potentially reduce the risk of ground current injury from an imminent lightning strike, another strategy is to insulate oneself from the ground. This can be done by sitting on a pack or a rolled foam sleeping pad. However, it’s important to note that this and the lightning position should be considered a strategy of last resort and not relied upon as the primary means of prevention. Maintaining this position for an extended period can be challenging, and it’s crucial to prioritize seeking proper shelter and following established lightning safety guidelines to minimize the overall risk of injury. 5
Case Study
25 YO F presents to the Burn Unit as a transfer from Cheyenne Regional Medical Center s/p lighting strike. Patient (pt) was caught in a thunderstorm on a hike and sheltered under a tall tree. Suddenly, she felt like she was being lifted up into the air and then dropped. Pt had a brief (<5 sec) loss of consciousness (LOC). When she woke up, she was completely numb and couldn’t move any of her extremities. Witness (friend) states the lightning splashed from the tree to the pt. Pt denies hitting her head with the fall. She denies taking blood thinners. She has no past medical history (PMHx) or past surgical history (PSHx).
Physical exam
Neuro: AOX4, No CN deficit on exam, LE paralysis resolved, LE paresthesia improving but still present
HEENT: L ruptured tympanic membrane, hearing loss on L side
CBC, CMP, troponin were all WNL. Serum hCG negative. CK mildly elevated (222)
EKG showed NSR.
CXR, CT brain, and c-spine neg for acute injury
She was admitted to the UC Health burn center for observation with tele. Her lab work and vitals remained stable throughout her hospitalization. She was evaluated by the trauma team with a negative trauma work up. The day of discharge, she was tolerating a regular diet, ambulating and sating well on room air. She was deemed appropriate for discharge home without patient audiology and ophthalmology follow up.
References
1. US Department of Commerce N. Understanding lightning science. National Weather Service. April 16, 2018. Accessed July 8, 2023. https://www.weather.gov/safety/lightning-science-overview.
2. Cooper MA, Holle RL. Mechanisms of lightning injury should affect lightning safety messages. 21st International Lightning Detection Conference. April 19-20, 2010; Orlando, FL.
3. US Department of Commerce N. Colorado Lightning statistics as compared to other states. National Weather Service. March 4, 2020. Accessed July 7, 2023.https://www.weather.gov/pub/Colorado_ltg_ranking.
4. US Department of Commerce N. How dangerous is lightning? National Weather Service. March 12, 2019. Accessed July 8, 2023. https://www.weather.gov/safety/lightning-odds.
5. Chris Davis, MD; Anna Engeln, MD; Eric L. Johnson, MD; Scott E. McIntosh, MD, MPH; Ken Zafren, MD; Arthur A. Islas, MD, MPH; Christopher McStay, MD; William R. Smith, MD; Tracy Cushing, MD, MPH. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Lightning Injuries: 2014 Update. WILDERNESS & ENVIRONMENTAL MEDICINE. 2014; 25, S86–S95
6. Flaherty G, Daly J. When lightning strikes: reducing the risk of injury to high-altitude trekkers during thunderstorms. Academic.oup.com. Accessed July 8, 2023. https://academic.oup.com/jtm/article/23/1/tav007/2635599.
7. NWS Colorado Offices – Boulder G. Colorado Lightning Awareness Week june 19-25, 2022. ArcGIS StoryMaps. June 25, 2022. Accessed July 8, 2023. https://storymaps.arcgis.com/stories/11d021f1b800429a869ead2dc32c0f96.
8. McKay B and K. How to survive A lightning strike: An illustrated guide. The Art of Manliness. April 25, 2022. Accessed July 8, 2023. https://www.artofmanliness.com/skills/outdoor-survival/how-to-survive-a-lightning-strike-an-illustrated-guide/.
Sophia Ruef is a Physician Assistant student at Red Rocks Community College in Arvada, CO. She grew up on the central coast of California and earned her Bachelor of Science degree inBiology with a concentration in anatomy and physiology from Cal Poly San Luis Obispo. She worked as an EMT and a tech in the Bay Area after her undergraduate education. In her free time, she enjoys hiking, backpacking, canyoneering, and spending time with family and friends.
Iron Deficiency without Anemia in Individuals Living at Altitude
Madeline Larson, PA-S2
People living at high altitude typically havehigher hemoglobin levels compared to those at sea level. This physiological adaptation occurs due to the lower oxygen availability at high elevations which stimulates the production of erythropoietin, a hormone that prompts the bone marrow to produce more red blood cells made famous by the Lance Armstrong blood-doping scandal. Hemoglobin, the protein in red blood cells that carries oxygen, thus increases to enhance theblood’s oxygen-carrying capacity. This adaptation helps individuals efficiently transport oxygen to tissues despite the reduced atmospheric pressure. Over time, this increased hemoglobin level helps maintain adequate oxygen delivery to vital organs, supporting overall health and physical performance in the challenging high-altitude environment.
Despite this natural adaptation of increased hemoglobin levels, people living at high altitude are still susceptible to anemia. Chronic exposure to lower oxygen levels can sometimes lead to a condition where the body’s capacity to produce red blood cells is insufficient to meet increased demands. This can be due to various factors, including inadequate dietary iron, vitamin deficiencies, or underlying health conditions that impair red blood cell production or lifespan. Additionally, individuals who move to high altitudes without sufficient acclimatization may experience a temporary drop in hemoglobin levels until their bodies adjust. Addressing anemia in such environments often involves a combination of dietary adjustments, supplementation, and medical interventions to ensure that the red blood cell count remains adequate to maintain optimal oxygen transport and overall health.
In people living at high altitudes, the threshold for diagnosing anemia is often adjusted to account for the lower oxygen levels in the environment. At high altitudes, the normal range for hemoglobin and hematocrit levels can be higherdue to the body’s adaptation to reduced oxygen levels.
For example:
Hemoglobin Threshold: At sea level, anemia is commonly defined as a hemoglobin level below 13.0 grams per deciliter (g/dL) in men and 12.0 g/dL in women. In high-altitude areas, these thresholds might be higher. For instance, at elevations above 2,500 meters (8,200 feet), a hemoglobin level of around 14.0 g/dL in men and 13.0 g/dL in women might be considered the lower limit of normal.
Hematocrit Threshold: Similarly, normal hematocrit levels are adjusted. At sea level, anemia is typically diagnosed with hematocrit levels below 39% in men and 36% in women. At high altitudes, these values might be adjusted to about 42% for men and 40% for women.
These adjustments are necessary because high-altitude residents tend to have higher hemoglobin and hematocrit levels as a physiological response to lower oxygen availability. If someone at high altitude presents with symptoms of anemia but has hemoglobin or hematocrit levels within the high-altitude normal range,further evaluation might be needed to assess their overall health and adapt to the specific altitude.
Understanding Iron Deficiency Without Anemia: What You Need to Know
Iron is an essential mineral that plays a crucial role in various bodily functions, most notably in the production of hemoglobin, which is vital for oxygen transport in the blood. While many people are familiar with iron deficiency anemia, where low iron levels lead to a reduced number of red blood cells, there is another, often overlooked, condition: iron deficiency without anemia. Understanding this condition is important for addressing health issues that can arise even in the absence of anemia.
What is Iron Deficiency Without Anemia?
Iron deficiency without anemia occurs when the body’s iron levels are insufficient, but the quantity of red blood cells and their capacity to carry oxygen remain within normal ranges. Essentially, it’s a state where iron stores are low, but the body has not yet progressed to a point where anemia develops. This can make it a bit tricky to diagnose since standard blood tests for anemia might not immediately show abnormalities.
Symptoms and Effects
The symptoms of iron deficiency without anemia can be subtle and may vary from person to person. Common signs include:
Fatigue and Weakness: Even without anemia, low iron can lead to feelings of tiredness and decreased energy levels. Coaches notice that some competitive athletes benefit from addressing iron deficiency without anemia.
Frequent Headaches: Iron is involved in various enzymatic processes in the body, and a deficiency might contribute to headaches or migraines.
Cold Hands and Feet: Poor circulation or lower iron levels can result in feeling unusually cold.
Brittle Nails and Hair: Iron deficiency can affect the health and strength of nails and hair.
Restless Legs Syndrome: Some people with low iron levels experience uncomfortable sensations in their legs, particularly at night.
Causes of Iron Deficiency Without Anemia
Several factors can contribute to iron deficiency without leading to anemia:
Dietary Intake: Inadequate consumption of iron-rich foods, such as red meat, legumes, and fortified cereals, can lead to low iron levels.
Increased Iron Requirements: Certain life stages and conditions, such as pregnancy, heavy menstrual periods, or intense physical activity, can increase iron needs.
Absorption Issues: Conditions like celiac disease or inflammatory bowel disease can impair iron absorption.
Chronic Inflammation: Chronic illnesses or inflammatory conditions can affect iron metabolism and utilization, even if anemia does not develop.
Diagnosis and Testing
Diagnosing iron deficiency without anemia typically involves a combination of tests and assessments:
Serum Ferritin Levels: Ferritin is a protein that stores iron in the body. Low levels can indicate depleted iron stores, even if anemia is not present.
Serum Iron and Transferrin Saturation: These tests measure the amount of circulating iron and how well it is being transported in the blood.
Complete Blood Count (CBC): While a normal CBC might not show anemia, it can help rule out other conditions.
Treatment and Management
Addressing iron deficiency without anemia often involves dietary and lifestyle changes:
Iron-Rich Diet: Incorporate foods high in iron, such as lean meats, leafy green vegetables, nuts, and seeds. Iron from animal sources (heme iron) is generally more easily absorbed than plant-based iron (non-heme iron).
Vitamin C Intake: Consuming vitamin C-rich foods like oranges, strawberries, and bell peppers can enhance the absorption of non-heme iron.
Iron Supplements: In some cases, a healthcare provider may recommend iron supplements. It’s important to follow dosing instructions carefully, as excessive iron intake can have adverse effects.
Address Underlying Causes: If an underlying condition is contributing to iron deficiency, treating that condition is crucial for resolving the deficiency.
Conclusion
While long-term adaptation to high altitude allows individuals to increase their iron available for erythropoiesis due to higher demand, those who have not adapted or are vulnerable due to exercise or pregnancy, are at risk of depleting their iron stores. Iron deficiency without anemia is a condition that requires attention to prevent potential health issues and improve overall well-being.
Resources & References:
Alkhaldy HY, Hadi RA, Alghamdi KA, Alqahtani SM, Al Jabbar ISH, Al Ghamdi IS, Bakheet OSE, Saleh RAM, Shehata SF, Aziz S. The pattern of iron deficiency with and without anemia among medical college girl students in high altitude southern Saudi Arabia. J Family Med Prim Care. 2020 Sep 30;9(9):5018-5025. doi: 10.4103/jfmpc.jfmpc_730_20. PMID: 33209838; PMCID: PMC7652112.
Kaylee Sarna, Gary M Brittenham, Cynthia M Beall, Detecting anaemia at high altitude, Evolution, Medicine, and Public Health, Volume 2020, Issue 1, 2020, Pages 68–69, https://doi.org/10.1093/emph/eoaa011
You may be surprised to learn that the University of California San Diego has been on the forefront of high altitude and hypoxia research since 1968. I recently attended the 9th Annual Center for Physiologic Genomics of Low Oxygen Summit (CPGLO) led by Tatum Simonson PhD where I gave a short presentation on Growth At Altitude. I met Dr John West who joined the university in 1968 after a Mount Everest research expedition with Sir Edmund Hillary in 1960. He also consulted for NASA serving on the advisory committee for Spacelab. He studied medicine and physiology at the University of Adelaide.
Dr. Chris and Dr. John West
The featured speaker was Isha Jain PhD from the University of San Francisco. Her research on mice shows how chronic hypoxia can mitigate and possibly cure some conditions, such as the devasting condition of mitochondrial disease. Colleen Julian PhD, from the University of Colorado, gave a talk on “Surviving Birth at Altitude: Genetic and Physiologic Insights”.
Other short presentations included a scientist from Florida who spoke of studying waterfowl who migrate at very high altitude as well as diving deep into the water to fish, thus adapted to two very different low oxygen environments. Among the poster presentations were a study on the effects of hypoxia on mitochondrial function in fibroblasts from loggerhead sea turtles presented by B. Gabriela Arango from the University of California Berkeley and a study on sleep apnea in self-identified Latinos.
Gabriela Arango from University of California Berkeley with her sea turtle research poster.
Acknowledging that chronic hypoxia may increase the risk of depression and suicide, the benefits include decreased incidence of obesity and diabetes and lower cholesterol/LDL with decreased or unchanged hypertension. These scientists study animals to help us understand the effects of our environment on our health. At conferences like this, we discuss how what I see as a clinician could be related to their study on the cellular and genomic levels.
Gabriela Arango and Dr. Chris were excited to meet again after both presented at the Hypoxia 2025 conference in Lake Louise, Canada in February
This poster was presented at the American Thoracic Society International Conference in San Diego in May of 2018. As yet unrecognized and unpublished, Trauma HAPE joins other presentations that have been suggested by altitude providers but have not been studied yet including Highlander HAPE, Post Anesthesia HAPE and Reverse HAPE, where life threatening hypoxia develops after return from altitude. The blog highaltitudehealth.com functions to raise awareness among other healthcare providers practicing at any altitude about the potential health complications associated with rapid changes in elevation.
In 2019, he managed to compete in his first Leadville Race Series, which included 50- and 100-mile MTB and trail run courses starting at above 10,000′ and rising to over 12,000′.
This summer, I had the pleasure of catching up with this extraordinary athlete and his wife Sayako, a dietitian and high-altitude runner herself who inspired Yuki to compete as a runner as well as a cyclist. The pair have been spending summers in the Colorado high country every year to train and compete before returning to their home in Japan to continue competing year-round, and between their experience training and racing and nutritional expertise, they make a formidable team.
Six years ago, we were all three of us in our thirties, and when I asked about what has changed about training and acclimating to the altitude since then, there was certainly a consensus about how it hasn’t gotten easier now that we are all in our forties. A significant part of their strategy for success has always been nutrition, and at this elevation, maximizing the delivery of oxygen throughout the body makes a huge difference. In our last interview, Yuki talked about incorporating foods rich in nitrates, which facilitate your body’s production of nitric oxide, like red bell peppers, arugula and beets, and these are still a big part of their diet.
Something they’ve been paying closer attention to lately is iron, also a critical component of blood. It’s dangerous for iron levels to be too high, but it can be a critical supplement for healthy circulation. In the case of long distance runners, blood vessels can take a considerable beating as feet hit ground over and over again for long periods of time. One food in particular that contains a high level of iron is clams. In Japan and the Pacific, asari, also known as Manila clam or Japanese cockle, is a regular part of cuisine and easy to find. Here in the middle of the Rockies, however, Yuki and Sayako have been buying canned clams to supplement their iron.
Every summer, the couple have come to the Colorado Rockies to train and compete. They’re full-time residence is in Tokyo, Japan, so each time they are traveling from sea-level, a dramatic and quick ascent to a high elevation. The decrease in available oxygen in the air at high altitude prompts a response in the body to create more red blood cells in order to carry more oxygen throughout the body. This requires more iron, which is vital for this process.
Additionally, the two athletes are paying special attention to nutrient absorption. Most of their diet is plant-based, and until recently, Yuki has been eating a completely vegan diet. Organic compounds found in plants called tannins and polyphenols — while beneficial — can inhibit your body’s absorption of nutrients you eat by up to 90%. So consuming something with these compounds along with your meal may dramatically decrease the benefits of nutrition in the food you’re eating. Coffee contains these compounds, so Sayako recommends waiting at least an hour after a meal to have a cup of coffee in order to maximize nutrient uptake. Even better, vitamin C can enable greater absorption, so consuming it (even in other foods such as a citrus) with a meal can be very helpful.
“… iron is also necessary for the hypoxia-inducible-factor (HIF) pathway, cellular energy production, myoglobin function (the muscle oxygen acceptor), and thyroid hormone function,” write DeLoughery and DeLoughery in a recent article for the Wilderness Medical Society. “The HIF pathway is the key regulator of the body’s response to hypoxia. Typically, the HIF-1 and HIF-2 proteins are rapidly degraded, but they are stabilized by hypoxic conditions when prolyl hydroxylase, which tags the HIFp roteins for degradation, is inhibited. When stabilized, the HIF proteins function as transcription factors that coordinate the synthesis of various proteins essential for the body’s response to hypoxia. Prolyl hydroxylase requires iron to function, and with a low iron level, this is less effective, leading to an exaggerated response to hypoxia.”
It is also important to note that, as Yuki and Sayako point out, it can take three to four weeks for anyone to experience noticeable results from any change in diet and nutrition. Keeping this in mind, it is advisable to increase iron intake weeks ahead of a trip to a high altitude environment, although further research may be needed to recommend just how much.
References
DeLoughery, MD, Emma P. Emma P. DeLoughery, MD and Thomas G. DeLoughery, MD, “Women, Iron, and Altitude — Path to the Peak”, Wilderness Medical Society 2025.
Diabetes is very prevalent in our society, with around 11% of the population in the United States diagnosed with this disease2. A key diagnostic test used in healthcare is the hemoglobin A1c (HbA1c) blood test. This blood test measures an individual’s average blood sugar over a 3-month period. A value of less than 5.7% is normal, 5.7%-6.4% is pre-diabetic range, and 6.5% and greater is a diagnosis of diabetes1. There are other blood tests that are used in the diagnoses of diabetes including fasting plasma glucose (FPG) and 2-hour postprandial glucose (2-h PG) testing. FPG testing measures blood sugar levels after 8 or more hours of fasting. A FPG value of 126 mg/dl or greater is diagnostic of diabetes. The 2-h PG test is a blood sugar reading 2 hours after eating a meal. A 2-h PG value of 200 mg/dl or higher is diagnostic of diabetes3. Currently the HbA1c blood test is the most used to diagnose diabetes, and many individuals around the world are diagnosed and placed on medications based off HbA1c results alone.
But is this appropriate for individuals living at altitude?
A groundbreaking study completed in mainland China has begun to answer this question for us. Altitudes and Hemoglobin A1c Values: An Analysis Based on Two Nationwide Cross-sectional Studies by Zheng et al was published in 2024. In this study, 95,000 adults were examined by comparing HbA1c, fasting blood glucose, and 2-hour postprandial (after a meal) glucose levels between individuals living above and below 2,500 meters (8,200 feet)4.
A key finding of this study was that individuals living above 2,500 meters had higher HbA1c levels but the same FPG and 2-h PG results as individuals below 2,500 meters4. The individuals at altitude may have HbA1c levels that are falsely elevated. This inaccuracy can lead to an inappropriate diagnosis of diabetes in individuals living at altitude. The researchers explained that oxygen levels at higher elevations are lower, and the body reacts to these low levels by increasing levels of red blood cells and the lifespan of red blood cells. When lifespan is increased, the hemoglobin is exposed to glucose in our blood stream for longer, eliciting a higher HbA1c result despite normal blood sugar levels4.
Another study by Bazo-Alvarez et. al in 2017 sought to evaluate the relationship between HbA1c and FPG among individuals at sea level compared to those at high altitude.
The study analyzed data from 3613 Peruvian adults without diagnosed diabetes from both sea level and high altitude (>3000m). The mean values for hemoglobin, HbA1c, and FPG differed significantly between these populations. The correlation between HbA1c and FPG was quadratic at sea level but linear at high altitude, suggesting different glucose metabolism patterns. Additionally, for an HbA1c value of 48 mmol/mol (6.5%), corresponding mean FPG values were significantly different: 6.6 mmol/l at sea level versus 14.8 mmol/l at high altitude.
These studies show that one-size-fits all screening for diabetes may not work for everyone, especially those living at altitude. Ebert Family Clinic, at 2743m (9000 ft) in the Colorado Rocky Mountains, has been researching the effects of altitude on many aspects of health including examining HbA1c levels in our residents and thus far we have seen elevated HbA1c levels in our otherwise healthy, “thin”, and active patients despite implementing appropriate lifestyle interventions to lower blood sugar. This can lead to unnecessary health anxiety that we hope to avoid by determining if HbA1c will continue to be an appropriate diagnostic tool with our residents living well above 2,500 meters.
References
1. Centers for Disease Control and Prevention. (n.d.-a). A1C test for diabetes and Prediabetes. Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/diabetes-testing/prediabetes-a1c-test.html
2. Centers for Disease Control and Prevention. (n.d.-b). National Diabetes Statistics Report. Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/php/data-research/index.html
3. U.S. Department of Health and Human Services. (n.d.). Diabetes tests & diagnosis – NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis
4. Zheng, R., Xu, Y., Li, M., Wang, L., Lu, J., Wang, T., Xu, M., Zhao, Z., Zheng, J., Dai, M., Zhang, D., Chen, Y., Wang, S., Lin, H., Wang, W., Ning, G., & Bi, Y. (2024). Altitudes and hemoglobin A1C values: An analysis based on two nationwide cross-sectional studies. Diabetes Care, 47(2). https://doi.org/10.2337/dc23-1549
One of the last things anybody wants to go through is a surgical procedure, especially if you happen to be in the mountains on vacation. Unfortunately, life happens, and whether you’re a visitor to high-altitude or a permanent resident, there is a chance you may need surgical care.
Anesthesia is a requirement for surgical procedures and there are varying levels of anesthetic available. General anesthesia, often referred to as “going off to sleep”, is where you are completely unconscious and anesthetic gases and medications keep you sedated while a machine breathes for you during your procedure. Monitored anesthesia care (MAC), also known as conscious sedation, is when the anesthesiologist keeps you comfortable with meds, but you are still able to breathe on your own. Medications given for surgery affect your ability to breathe, which is why your vital signs (oxygen levels, blood pressure, heart rate) are monitored through a machine by a doctor.
How is this different at high altitude?
When you head to higher elevations, barometric pressure decreases and causes partial pressure of oxygen to decrease – this makes oxygen harder to effectively get into your lungs and causes hypoxemia/low oxygen levels (Leissner & Mahmood, 2009). This leads to a condition commonly known as altitude sickness, causing headaches and trouble breathing, and in more serious cases, it can also lead to high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Much like oxygen, anesthetic gases are also affected by barometric pressures, impacting the effectiveness of inhaled anesthetics (Bebic et al., 2021). Additionally, equipment is affected by high altitude – meters on anesthesia machines that monitor gas/oxygen levels tend to under-read at higher elevations (Bebic et al., 2021; Leissner & Mahmood, 2009). Pulse oximetry, which measures your overall oxygen saturation (the percentage of oxygen in your blood) also has limited accuracy at high altitude (Bebic et al., 2021). Providers who practice at higher elevations should be aware of these nuances and treat accordingly. The most important treatment we have to help with the effects of partial pressure at high altitude is supplemental oxygen (Leissner & Mahmood, 2009).
Unfortunately, there is limited research on the effects of high altitude and anesthesia, and even less on the effects of anesthetic drugs at high altitude vs. sea level (Bebic et al., 2021). With current published data, it is clear that surgical risks increase with elevation. Whether it’s the potential for equipment to malfunction, or novice providers new to high-altitude unaware of the subtleties in treatment, it is critical to be mindful of compromised respiratory status at elevation when considering which anesthetic agents to use for surgery.
References
Bebic, Z., Brooks Peterson, M., & Polaner, D. M. (2021). Respiratory physiology at high altitude andconsiderations for pediatric patients. Pediatric Anesthesia, 32(2), 118-125.
Why Too Much Oxygen Can Be Deadly: The Hidden Molecular Consequences of Hyperoxia
by Nic Rolph, PA-S
Oxygen keeps us alive—but in excess, it can quietly unravel critical cellular functions. A groundbreaking study by Baik et al. (2023) in Molecular Cell shines a light on why hyperoxia (too much oxygen) is toxic, and reveals a hidden mechanism behind its damaging effects.
The Mystery of Oxygen Toxicity
We’ve long known that both oxygen deprivation (hypoxia) and oxygen overload (hyperoxia) are harmful. While hypoxia research has led to major discoveries like the Nobel Prize-winning work on HIF (Hypoxia-Inducible Factors), hyperoxia has remained less understood—until now.
Baik and colleagues tackled a fundamental biological question: Why is oxygen toxic at the molecular level?
The Culprit: Fragile Iron-Sulfur Proteins
Using a combination of genome-wide CRISPR screening, proteomics, and in vivo experiments, the researchers identified a specific class of proteins highly vulnerable to excess oxygen: iron-sulfur cluster (Fe-S)-containing proteins.
These clusters act like tiny biochemical power stations inside proteins, but they’re extremely sensitive to oxidation. Under hyperoxic conditions, certain Fe-S proteins degrade, compromising several key cellular pathways:
Diphthamide synthesis – crucial for accurate protein translation.
De novo purine biosynthesis – needed for DNA and RNA building blocks.
Mitochondrial electron transport chain (ETC) – essential for energy production.
A Vicious Cycle of Oxygen Damage
Perhaps the most striking discovery was the feedback loop of cellular damage:
Hyperoxia damages the ETC, lowering oxygen consumption;
this increases local tissue oxygen levels even more,
which leads to more damage—a self-amplifying loop Baik et al. called “cyclic oxygen toxicity.”
This cycle can explain why supplemental oxygen—while lifesaving—is also associated with complications in neonatal care, ICU patients, and chronic diseases.
From Petri Dishes to Lungs
The team validated their findings in human cells, mice, and even primary lung tissue. In a mouse model of hyperoxic lung injury, the same Fe-S proteins degraded rapidly—especially those in the ETC. Mice with preexisting ETC defects (like the Ndufs4 KO model) showed extreme sensitivity, confirming the ETC as the “weakest link” in the oxygen toxicity chain.
Bigger Picture: Aging, Disease, and Therapy
This study suggests that hyperoxia might contribute to a wide range of diseases—from premature infant lung injury and ischemia-reperfusion damage to neurodegenerative and mitochondrial disorders. It also offers a potential explanation for why antioxidant therapies have largely failed: superoxide isn’t the only villain—molecular oxygen itself may be enough to destabilize these proteins.
Rethinking Oxygen Therapy
Given these findings, clinicians may need to rethink how we use oxygen in medical settings. Rather than focusing solely on delivering “more oxygen,” we might need to tailor therapy to a patient’s oxygen-processing capacity—especially in those with mitochondrial or genetic vulnerabilities.
What’s Next?
Future research may explore:
Therapeutic hypoxia to interrupt the damage cycle.
Genetic screening to identify patients vulnerable to oxygen toxicity.
New drugs to stabilize Fe-S proteins in oxidative environments.
Takeaway
Oxygen is life-sustaining—but Baik et al. reveal it’s also a molecular saboteur under the wrong conditions. This landmark study not only explains the elusive biology of oxygen toxicity but opens new doors for safer therapies and deeper understanding of metabolic diseases.
Note from Dr. Christine Ebert-Santos, MD, MPS of Ebert Family Clinic in the Colorado Rocky Mountains at 9000’/2743m: newborns, children with respiratory infections or high altitude pulmonary edema, and people with sleep apnea are advised to use oxygen at high altitude. The level of oxygen saturation achieved with this treatment is well below normal sea-level values, so unlikely to cause any negative effects.
How does the low oxygen environment at altitude affect our ability to exercise? What is the risk for developing harmful changes in the heart and lungs? Does sleep apnea contribute to these risks? Can supplemental oxygen reverse or reduce these risks and increase our exercise ability at altitude?
These important questions have been studied by an international research team conducting tests on residents of the Tien Shan mountain range in Kyrgyzstan, 2500-3500 m (8,200 to 11,482 feet). Dr. Silvia Ulrich presented some of their findings at the Hypoxia 2025 conference in Lake Louise in the Canadian Rocky Mountains this past winter. Using an exercise bike they measured ECG, pulmonary gas exchange and oxygen saturation in healthy highlanders. Participants’ average age was 48 years, 46 % were women, and their average oxygen saturation (SpO2) at rest was 88%. Normal occupations include nomadic herdsmen, hunters and soldiers who usually travel by car or horse, with no prior experience cycling or running. An echocardiogram was performed to assess pulmonary artery pressures (PAP) and right heart function.
Arterial blood gas analysis at baseline showed a normal pH, low oxygen, mildly decreased carbon dioxide and bicarbonate, and higher hemoglobin concentrations. Bicarbonate values were 22-26 moles/L. In Summit county, in the Rocky Mountains of Colorado, with residents living between 2500 to 3300 m bicarbonate values are 17-20 moles/L.
Results showed their peak oxygen uptake, and peak work rate was reduced by one quarter compared to predicted values for lowlanders. Oxygen saturation decreased during exercise. “Exercise limitation was related to an exercise -induced worsening of hypoxemia, high ventilation equivalents for oxygen uptake and carbon dioxide output, a reduced external work efficiency and a lower peak heart rate than predicted for age.” (1) In other words, they had to breathe harder to maintain their oxygen and carbon dioxide at normal values and use more effort for the same musculoskeletal output. Their heart rate did not increase as much as a person from lower altitude doing the same work.
There is little research on exercise capacity in long-term residents at altitude. Most studies focus on athletes or comparing healthy acclimatized men to recent arrivals. The hypoxic environment is a known risk for pulmonary hypertension, which can lead to exercise intolerance and fatigue that is reversible with descent or oxygen use when diagnosed in a timely manner. Sleep apnea with the accompanying hypoxic episodes adds to this risk. Summit County residents show improvement in both systemic and pulmonary hypertension with supplemental oxygen during sleep, according to local health care providers.
Kyrgyzstan residents studied showed a strong correlation between the incidence of sleep apnea with hypoxia (time below 90% SpO2), and abnormal pulmonary artery pressures. Echocardiograms compared 97 highlanders with 76 lowlanders who were asymptomatic. Between 6% and 35% had increased PAP depending on which definition is used.
The research team also evaluated their response to supplemental oxygen at altitude and 760m elevation using the six minute walk test. Although the test subjects reported less shortness of breath and had higher measured oxygen levels they were not able to walk further. Supplemental oxygen did reduce pulmonary artery pressures in those at risk when tested at 3,200 m.
This research was conducted by a crew of scientists who brought all the equipment with them to a basic medical clinic in a village.
Summit County cardiologist Warren Johnson was impressed by the numbers of people with elevated pressures in their lungs. “It could be as high as 30 per cent of adults,” he told local physicians. Symptoms are subtle: decreased exercise tolerance, mild shortness of breath, trouble sleeping, high red blood cell counts. Most people just think they are out of condition or aging.
A study in Spiti Valley India of residents living at 9000-13000 ft found an incidence of three per cent with PH. Dr Johnson suspects this is a highly adapted population with centuries of mountain living.
Diagnosing this condition early with Echocardiogram can prevent serious disability. Treatment is as simple as sleeping on oxygen. These measurements and much more are performed on a daily basis at the St. Anthony Summit Hospital, a 34-bed hospital serving five counties in Colorado, located at 2800 m. A parallel study to establish baseline normal values for the healthy population and identify the risk for pulmonary hypertension in asymptomatic mountain residents would be valuable for health care providers who are frequently asked to counsel residents on the risk of living at altitude.
References
Forrer A, Scheiwiller PM, Mademilov M, Lichtblau M, Sheraliev U, Marazhapov NH, Saxer S, Bader P, Appenzeller P, Aydaralieva S, Muratbekova A, Sooronbaev TM, Ulrich S, Bloch KE, Furian M. Exercise Performance in Central Asian Highlanders: A Cross-Sectional Study. High Alt Med Biol. 2021 Dec;22(4):386-394. doi: 10.1089/ham.2020.0211. Epub 2021 Aug 24. PMID: 34432548.
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