The Benedict Excursion: Testing Your Limits at Altitude

In a previous blog, I described preparing for a trip to the Benedict huts above Aspen, Colorado. After over eight hours of skinning uphill in the snow and two hours snowboarding back down, we are all back home, and I’ve finally cleaned all the pistachios and cookie crumbs out of my car. And yes, it took me eight hours to reach the hut.

I’ve been on numerous hut trips in the Colorado Rockies year after year, and it’s safe to say the trek to the Benedict huts (there are two: Fritz and Fabi) is the most challenging, mentally, physically and emotionally. The winter trail descriptions on the 10th Mountain Division Huts Association website did provide some insight into navigating the route. However, we found the descriptions of elevation gains and mileage to be quite different from the route we took: a winter trail marked by blue diamonds and arrows (a pretty standard trail marking practice).

Even following the appropriate trail markers, there is a crossroads where, looking at a map, we could see that the recommended Smugglers Mountain Road trail was significantly longer than the 10th Mountain trail we decided to take. And even after having taken the shorter route, we hiked about two miles farther than the trail directions had described. Having started at Upper Hunter Creek trailhead, we’d expected to arrive in 4.8 miles, but had long passed 6.

The trail description listed an elevation gain of 2130′, but by the time we reached the hut, we’d gained over 2300′. This isn’t a gradual incline, either. It is important for anyone setting out on this trail to know that you will be climbing the grade of a ski hill the entire way.

Our team came from the Colorado high country and San Francisco. We are all fit, athletic and experienced in various kinds of outdoor recreation. After collecting the San Francisco constituency from the Denver airport, we made a point of allowing a full day to acclimate in Frisco, Colorado, at 9000 ft. Blood oxygen levels were quite normal for people coming from sea level, averaging around 90%. Those concerned about nausea and headaches started taking Diamox, and we all made sure to drink plenty of water and prioritize sleep before setting out on the trail the following day.

By the time we arrived at the hut, it was 8 pm, and the sun had just dipped below the mountains. Sore and sunburned in spite of multiple reapplications of sunscreen, the rest of our evening was devoted to self-care, recovery, and refueling. All the food we had painstakingly carried up was certainly worth it. Our epic journey up the mountain had been fueled by nuts, energy bars, stroop waffles, chocolate chip cookies, and a lot of water. So we immediately got to work lighting up fires to melt snow for our water filtering systems and cooking a hearty sausage and tomato pasta.

Classic hut breakfast on a propane stovetop.

We were sure to feed every craving for calories, because we weren’t about to pack it all back down after what we’d just been through to get it up there. Although I’d planned to do some snowboarding, the following day was mostly dedicated to resting, eating, reading, and games. Frittata with bacon, shiitake mushrooms, manchego and peppers (and of course, pancakes) for breakfast; the aforementioned epic sandwiches for lunch, and loco moco’s for dinner. Plenty of chocolate, cookies, coffee, beer and bourbon to close the calorie gap. And constant water intake. I refused nothing.

Epic hut sandwich.

Hut trips require considerable effort, not only for the traverse and recreation outdoors while you’re in residence, but also for basic necessities. With no running water, snow must be collected in the winter to be melted over a fire you have to build, then boiled and/or poured through a filtering system. There is typically a large supply of wood for these fires on hand, but for less-maintained structures, gathering and chopping wood will also claim a lot of calories.

Recovery on a hut trip must be efficient in order for you to enjoy your time there while also preparing for the trek back out. Stretching, hydrating, feeding your cells nutrients, and sleep are what it’s all about. While the rest seem simple enough, choosing foods to replenish your supply of nutrients and treat any ailments or injuries you may have may take some more thought. As I mentioned in the previous blog on Packing for a Spring Hut Trip, the intense physical challenge of these trips requires energy your body can quickly convert from sugars and caffeine, which make chocolate and coffee easy options. For the time I can give my body to rest and recuperate, I want to feed it denser meals with better nutrient-to-calorie ratios, and this is where I look for proteins and carbohydrates that will take my body a longer time to process.

Stuffing our faces with Dr. Chris. See above for sandwich.

My body will use all these nutrients (including fats) even as I sleep as it repairs and replenishes itself. The extremity of long exposure to the elements stresses your brain as well as the rest of your body, and well-hydrated sleep is one of the best things you can do for it.

Alcohol, as you know, dehydrates the body. But a hut trip without beer and whiskey is not something I’ve ever heard of, so I make sure I continue to hydrate with plenty of water as well. The sugar from alcohol, however, may contribute to your store of energy the following day, but there is definitely a threshold where the amount of consumption contributes more to a disabling hangover. I continue to do more research on the matter.

Being so sore the first night, I was a little concerned about being able to move the rest of the trip. As much as I wanted to just lie down, I know stretching is just as vital to healing muscle mass after strenuous activity, and the combination of ample hydration, nutrient intake and stretching gave our bodies the resources to maximize the time we did spend napping and sleeping the next day. I did manage to get out on my split-board for a mini-tour around the site in the afternoon before dinner the second night, but it hadn’t snowed in the area in a while, and the snowpack was very hard after so many days of warm Spring weather.

The hut sits at the top of the mountain we ascended, so the terrain immediately around it doesn’t get much higher. The area is also pretty heavily wooded in all directions, so building a kicker to snowboard off of was out of the question. The party in the Fabi hut next door invited us to some skiing just a 3-mile hike along a ridge away, but none of us felt like adding 6 more miles to what we’d already trekked.


I am glad I made a point of skiing around the hut, though. It was a great way to get my blood and breath moving around my body with fresh nutrients. One of the best parts about going on a hut trip is how efficiently it makes you spend your time. Even time lying down doing nothing is just as valuable as time exercising.

Mountain Kate

We set back out to the trailhead early Easter morning. Two nights and two unforgettable days later. We didn’t get any new snow, so those of us who weren’t on snowshoes were skiing/snowboarding down hard-pack. Con – crete. A two hour ski run sounds amazing. This was like two hours of squats. With a backpack on. So that happened.

But it sure beat the hike up! In retrospect, I’d say we packed appropriately. We might have had some extra food for the way down, but we were fortunate that the weather was sunny and warm, and that no sort of emergency required extra rations. I was almost too warm between the daytime sun, and the wood stove at night. But again, the weather could have been worse, and I would have needed every single layer I’d brought. Not mad about that. In a word, “harrowing” was mentioned more than once while on the trip. But no one had to carry any beer or bourbon back.

The high altitude research team from San Francisco.

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.

Genetics at Altitude: Should pregnant mothers or women who are hoping to conceive sleep on oxygen?

A child in my clinic had a small appendage in front of her ear, called a preauricular tag. I told the mother that I had just returned from a conference where I learned these are more common at high altitude. She replied, “But his father has one also.”

“Yes,” I explained, “There is an interaction between the genes and low oxygen.”     

Birth defects can be increased or decreased by the chronic hypoxia at high altitude. Geneticist Igor Salvatierra from the Hospital Materno-infantil discussed the interaction between oxygen levels and chromosomes at the Chronic Hypoxia conference in La Paz, Bolivia. He focused on a deformity we also see more commonly in Summit County, Colorado at 2800 meters: outer ear deformities – microtia.     Birth defects can be structural, like the outer ear, or functional, such as deafness, and occur in 1 out of 33 infants worldwide. Only 50% of abnormalities can be linked to a specific cause. Club foot is an example of a birth defect that is less common at higher elevations. In contrast, microtia is three times more common, with preauricular tags twice as common as at sea level. This is due to the interaction between genes and the environment.

Research has identified an enzyme called Jarid1B that is affected by hypoxia, including sleep apnea, copy number variation (CNV) and epigenetic factors such as stress and diet. These act on chromosome 1q32.1 to change the coding of proteins involved in the development of ear cartilage very early in fetal development.

At lower altitudes, the hypoxic environment can be caused by sleep apnea. In early pregnancy this could be one of many factors that, if added to the genetic predispostion, could cause a deformity in the fetus. Luckily the fetus is fully formed before the sleep difficulties in late pregnancy.

Should pregnant mothers or women who are hoping to conceive sleep on oxygen?

From what I learned in La Paz, not necessarily. There are factors in our low-oxygen environment that decrease our risk of other diseases.

Acclimatization Vs. Adaptation: Interview with Dr. Alison Brent on “Charting Pediatrics” Podcast

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 Owlet is 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 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, 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!

Packing for a Spring Hut Trip

Another winter has come and gone, and now Spring is in Colorado. Which means Winter will be back a couple more times before the snow all melts.

We’ve organized a team of friends from San Francisco, Denver, and Colorado high country for a backcountry excursion to one of Colorado’s 10th Mountain Division huts. The Benedict huts, our dwelling for two nights tucked into the wilderness outside of Aspen, are almost 6 miles from the trailhead, with an elevation gain of over 2000 ft. : a formidable trek, even for the experienced. And experience in wilderness trekking is one thing, but altitude is a game-changer. We will be well over 8000 ft. long before we reach the huts, so preparation for such an undertaking requires as much attention to mental, physical and physiological condition as much as clothing, gear and rations.

Weather & Conditions

This has everything to do with the weather, so it’s important to be on top of tracking all the resources available to you. At the top of my list in this region is the Colorado Avalanche Information Center. They provide up-to-date reports for high-risk areas around the state according to a comprehensive and easy-to-understand rating system. When considering this information, I always remember that our trek will take us through several types of terrain, and thus, several types of conditions: in and out of trees, varying steepness and exposure (to sun, wind, precipitation, etc.), all kinds of microclimates and environments (wetlands, scree fields).

The Colorado Avalanche Information Center provides no shortage of visuals to aid your risk assessment.

As far as incoming weather patterns are concerned, one of the most popular and reliable forecasts endorsed by people who play outside in Colorado is Open Snow. Founding meteorologist Joel Gratz updates local forecasts regularly, and provides information on what to expect with the outdoor adventurers in mind.

For our upcoming hut trip, it looks like the storm we’re expecting will be warmer and milder than recent systems, with most of it heading toward the northern mountain region. That being said, however, I’m keeping in mind that any projected weather system can be just a few degrees colder, a few inches wetter, and a few miles closer and change conditions dramatically. So let’s talk about how we can anticipate this with …

Gear & Clothing

The Commute

In any season in Colorado, there are essential comforts I always pack to get me to and from any hut that requires a hike, and to keep me happy while I’m enjoying the site. Dead of Winter, Height of Summer alike, the sun and glare is liable to be more intense than anything you’ve ever experienced at sea-level, while at the same time, the temperature and lack of humidity can cool your body significantly, night or day. Depending on how strenuous the commute is or how active you intend to be even after arriving at your destination, you may be constantly shedding, then adding, then shedding, then adding layers, so keep it all very accessible.

For this particular trek, I’ll be in snow gear. Basically anything I’d wear snowboarding: snow pants, outer shell on top, hat, gloves. I want it to be warm and waterproof on the outside. Underneath this shell, I want layers that I can strip down to as soon as I start moving and sweating with a 40 -60 lb. pack on. Unless the storm turns out to be much more intense (in which case, I’ll keep the outer layers on), I expect my skin to be steaming, so I won’t want to be in much more than warm compression tights, a t-shirt, and a light pullover. Your outer shell is for blizzards and water-proofing, so whatever you are stripping down to should be significantly lighter. Also, sunglasses or goggles. The glare from snow is significant. I bring both, because goggles get way too hot while I’m trekking uphill.

Here’s the tricky part: What are you going to wear on your feet? This is where the weather forecast comes in. This time of year, after such a snowy winter, I’m expecting most of the trail to be covered in snow, and the storm moving in is likely to bring more. I will be scoping out the trail pre-storm, which will give me a much better idea of what to expect, but I’m preparing to have snowshoes or a split-board and skins strapped to my snowboard boots. Of course, skis with skins are another alternative. There is a very slim chance most of the snow on the trail will be melted down, in which case I would probably opt for waterproof boots instead, which I would expect to get pretty muddy.

Avalanche Gear

Whether it’s on the commute or while you explore terrain around the hut during your stay, there are some essentials you can pack for the worst-case scenario. I’ve gone into more detail in a previous blog, but standards that I will be keeping on me are a shovel, probe and beacon. But these tools are only a small part of avalanche preparedness. More important than the endless supply of technology you can invest in is knowing what conditions and natural phenomena to be aware of during your trek, and the Colorado Avalanche Information Center is a great place to start familiarizing yourself with these.

Cabin Comforts

There is only one limiting factor to this list, but it is considerable: how much you can carry. For six miles. Uphill. In snow.

Most of the huts in the 10th Mountain Division hut system are equipped with soft mattresses, small pillows, and blankets. The kitchens are stocked with utensils and dishes, there is toilet paper, paper towels, hand sanitizer and dish soap, as well as ample supplies of wood for burning in the wood stoves. So most of your weight will be food and drinks.

I always pack a sleeping bag and extra pillow, because the guaranteed warmth and comfort are worth it when you’ve spent your day being intensely active outdoors. And keep in mind you’ll want warm, dry layers to change into that you haven’t been hiking and sweating in all day. What do you want to be wearing when you’re lounging around the cabin reading, cooking, eating, playing cards, etc.? For me, this looks like socks, long underwear, a pullover and slippers that I can crush into my pack. And then what are you going to throw on when you have to go back outside into the dark cold of night to use the outhouse? Your Colorado uniform: a hoodie.

There won’t be running water, so you can’t expect to shower. When you’re in the wilderness for a long time and need to be discerning about how much weight you carry that isn’t food and water, bathing is of low priority. But for a short trip like this, I don’t mind bringing some form of wet wipes; they’re light-weight and take up very little space. Toothbrush and toothpaste should be obvious, though.

Medication & Acclimation

From climbing Mt. Fuji to Colorado’s 14er’s, I’ve noticed a lot of people bringing pressurized cans of oxygen. High altitude research has taught me just how temporary and unnecessary this trend is. Often, the most effective remedy for altitude sickness is 5 – 10 minutes on oxygen. I’m pretty sure you’ll blow through a whole can of gas-station aerosol oxygen before it does you any lasting good.

Avoid this by giving yourself time to acclimate before you get to extreme elevation. Ebert Family Clinic in Frisco, Colorado, specialists in high altitude research, always recommend keeping track of blood oxygen saturation with a pulse oximeter, and this is something small, inexpensive and very portable. Our team will be spending at least 24 hours at altitude before we embark on the trek to the hut. This way, members from lower elevations will have access to an oxygen concentrator to facilitate acclimation.

Physician and high altitude expert Dr. Christine Ebert-Santos recommends packing the following mediations for hut trips: Acetazolamide, Benadryl, Ibuprofen, an EpiPen, Acetaminophen, and topical antibiotic oinment. Of course, be aware of any allergies to medication in your party. It is also helpful to be aware of what symptoms you may expect to experience, should you start having trouble acclimating, including dizziness, nausea, hyperventilation, and fatigue.

Food & Water

This is where most of the weight you pack in will be. Again, no running water at the hut, so expect to boil all the water you need for drinking if you run out of what you bring. There are lots of compact water purification systems you can easily pack as well. For our six mile trek to the cabin, I will have a Camel Bak and a couple Nalgene-sized thermoses full of water tucked into my pack.

You don’t want to have to cook everything you bring, so snacks you can easily access and eat are essential, especially for the trail. For this particular hike, I expect to burn more calories more quickly than any other average day, so I want lots of nutrients per gram: pistachios, energy bars, jerky … And don’t underestimate the power of sugar and caffeine, this is precisely the kind of work your body acts quickly to convert these nutrients to energy for. And yes, I mean chocolate. (Fruit also contain a lot of valuable sugar, I’m told.)

While we’re at the cabin, we’ll have access to a propane stove, so we’ll be able to cook some hearty meals. Bacon, fruit, yogurt, bagels and cream cheese are all easy breakfast foods to pack. If you are fortunate enough to be on a hut trip with Dr. Chris herself, you will have pancakes at least once. It’s also easy enough to bring fixings for the most epic sandwich you’ve ever had: guacamole, sprouts, turkey, ham, greens, tomatoes, bread; and remember, it’s a good chance to justify all the calories you get from mayonnaise and mustard.

And speaking of calories and sugar, I feel like whiskey and beer were invented to accompany the warmth of a fire in a remote, mountain cabin. The good news is that you are sure to be carrying less out than you did in. The bad news is that hangovers are exacerbated by high altitude, so pay more attention to your consumption than you would at any lower elevation, and be sure to have plenty of drinkable water at hand.

Am I Ready?

Hut trips in Colorado are mentally and physically challenging, even in the best conditions. The more time you give yourself, the better. Know before you go and don’t go alone. And don’t be intimidated. I’ve successfully guided friends from sea-level who don’t consider themselves athletic to destinations well above the tree line without incident.

Always be checking in with your body, your team, and your environment.

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.

Increasing the Altitude to Decrease the Symptoms of Parkinson’s Disease

By Jessica Thomas PA-S

 In May of 2009 Michael J Fox’s “Adventures of an Incurable Optimist” aired on ABC. This special chronicled his decision to battle the effects of his Parkinson’s disease with optimism and hope. During the production of this special he journeyed to the Kingdom of Bhutan. While in Bhutan, Michael J. Fox noted that his symptoms of Parkinson’s disease had almost completely vanished. 

 Bhutan lies between China and India, on top of the Himalayan Mountains. Bhutan is an extremely unique country since it is cut off from the rest of the world and has a desire to keep its culture unaffected by today’s modernization and globalization. Altitudes in Bhutan average 8-9,000 ft above sea level. When Fox’s parkinsonian symptoms decreased, he couldn’t help but wonder about the connection between the increased altitudes and the decrease of his symptoms. 

With more research into the topic it becomes apparent that Michael J. Fox was not the first person with Parkinson’s disease to notice a difference when in the high altitudes. According to Fred Ransdell, author of Shaky Man Walking, he has had two individual experiences where his tremors almost completely vanished. The first takes place whenever he is flying. Mr. Ransdell states that as the plane gains altitude he will remain completely asymptomatic until the plane lands. The second was when he was driving over a mountain pass at 9,000 feet elevation and he states that at that moment he noticed that his tremors were gone. How can this be? 

The first theory for why the increased altitude (>6,000 ft above sea level) decreases symptoms of Parkinson’s disease stems from the pH of our blood. When at higher altitudes we breathe faster and deeper in order to get enough oxygen into our lungs. When we breathe, our body discards carbon dioxide in proportion to oxygen we take in. Knowing this, it is understood that the increase in breathing also causes our body to get rid of more carbon dioxide from our blood which in turn will raise the blood pH making it more alkaline in nature. Naturally our blood is alkaline (approximately a pH of 7.3-7.4), otherwise death would ensue. Acids in our body are generally cell by-products, meaning that when our body is making energy or other necessities to life, they will give off acids. These acids are processed through the lymphatic system. When we have increased acids in our body the lymphatic system can get backed up. The back-up of acids in the body can cause stiffness, pain, and swelling. As the back-up worsens, deeper problems occur that affect the function of the cells and the tissues which can turn off hormone, steroid, and neurotransmitter production. Although this is an oversimplification of the process, it is easy to see that the more acidic the blood is, the more we may see increased symptoms of Parkinson’s disease. Correction of this acidosis is thought to preserve muscle mass in conditions like Parkinson’s and help with coordination. 

The second theory revolves around hypoxia and the main neurotransmitter that Parkinson’s disease effects. A study published in Springer titled Intermittent Hypoxia and Experimental Parkinson’s Disease found a link between hypoxia and the increase of dopamine synthesis. We know that atmospheric pressure reduces with altitude and with that so does the amount of oxygen. The reduction in the partial pressure of inspired oxygen at higher altitudes lowers the oxygen saturation of the blood which leads to hypoxia. But what does this have to do with parkinsonian symptoms? The results of this study revealed that a two-week course of intermittent hypoxia training in patients with Parkinson’s disease increased dopamine synthesis in old and experimental PD animals which restored the asymmetry of DA distribution in the brain. Parkinson’s disease is a progressive disorder that affects dopamine-producing neurons in the brain. When these neurons are destroyed, the production of dopamine severely decreases and we see symptoms such as tremors, slowness, stiffness, and balance problems

The Michael J. Fox Foundation for Parkinson’s Research received a research grant in 2018 to study the effects of altitude on Parkinson’s Disease. The study consists of two individual parts. The first part is a focused survey that asks individuals with Parkinson’s about their best and worst experiences with their symptoms during their travels in the last 2 years. The second part of the study will be an in-depth survey that with capture the travel experiences prospectively. 

Maybe we see the decrease in symptoms because of the hypoxia or maybe it is due to the increased pH of our blood, or maybe it is because of something we have yet to discover. With the new study from the Michael J. Fox Foundation on the horizon, answers to this question may be within our grasps. 

Jessica Thomas is a Physician Assistant student at Des Moines University in Iowa. Following graduation Jessica will be practicing family medicine in small town Iowa with an emphasis on preventative care and pediatrics. Over  the course of the last year she has had the joy of living and working in 6 different states around the country and has experienced many different climates and learned how to care for the ailments that occur in the different regions of the United States. When not at work or studying, you can find her reading on her porch swing, watching Hallmark movies in bed on Sunday afternoons, or spending time with her family and friends. 


F. R. (n.d.). Altitude and Parkinson’s disease. Retrieved from

Altitude in Bhutan. (n.d.). Retrieved April 12, 2019, from

Belikova, M. V., Kolesnikova, E. E., & Serebrovskaya, T. V. (1970, January 01). Intermittent Hypoxia and Experimental Parkinson’s Disease. Retrieved from

Bloem, B. R., & Faber, M. J. (n.d.). Exploring the Effect of Altitude on Parkinson’s Disease. Retrieved April 12, 2019, from

Ma, H., Wang, Y., Wu, J., Luo, P., & Han, B. (2015, September 01). Long-Term Exposure to High Altitude Affects Response Inhibition in the Conflict-monitoring Stage. Retrieved April 12, 2019, from

Parkinson’s and Nutrition. (n.d.). Retrieved from

Schwalfenberg, G. K. (2012). The alkaline diet: Is there evidence that an alkaline pH diet benefits health? Retrieved from

Expected Variations in Nocturnal Oxygen Saturation in Infants: Comparing Needs at Sea Level to High Altitude

What is a normal overnight oxygen saturation for a child? This question is asked frequently by parents who have a child that may be requiring oxygen after evaluation. As healthcare providers working at various altitudes and caring for children, knowing the change in baseline oxygen saturations when at different altitudes is key to educating patients.  There are physiologic changes that result in transient changes in respiratory rate and volume while sleeping which will be discussed before exploring nocturnal oxygen needs at sea level versus needs at high altitude in healthy children. 

To begin, I will define a few terms that may not be familiar, but may be used when discussing oxygen needs. Oxygen saturation is defined as the amount of oxygen bound to hemoglobin in the blood, expressed as a percentage of maximal binding capacity.1 The simplest and most non-invasive way to obtain this information is through a pulse oximeter, which is placed on the patient’s finger, toe, or ear when vital signs are being taken. Oxygen saturation is known as the “5th vital sign” and tells medical providers whether or not a patient is delivering enough oxygen to their body. Hypoxemia is defined as insufficient oxygenation of the blood.2 There are multiple causes of hypoxemia, however we categorize hypoxemia as an oxygen saturation of less than 90 percent on a pulse oximeter. Finally, we use the term desaturation to describe a patient whose oxygen saturation continues to go below expected values.

In healthy, full-term infants, sleeping approximately 16 to 18 out of 24 hours is expected. A majority of their sleep cycle is REM and occurs when they fall asleep, with shorter duration of NREM sleep. As the child’s nervous system matures, there will be predictable changes in their sleep cycle, which will be more similar to a child or an adolescent. In children and adolescents, NREM is entered when they initially fall asleep, and accounts for approximately 75 percent of total sleep time, with alterations every 90 to 100 minutes of REM and NREM. In addition, there is a progressive increase in REM in the final third of the night.3 Understanding these cycles, what occurs during these cycles, and how they change over time are important in understanding the physiological changes (Table 1) that occur while you are sleeping.

  The physiological changes that we are focused on are decreased respiratory rate and decreased respiratory volume, which are seen in NREM and in the phasic stage of REM. In infants, periodic breathing is also an observed pattern of breathing that is expected after the first 48 hours of life until about 6 months of age. Periodic breathing is recurrent central apnea interrupted by breathing efforts. This topic will further be discussed in the high-altitude study, as these episodes are more common at high altitude.4

Table 1: Normal physiologic changes during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep.5

In a study conducted at sea level in Brisbane, Queensland, Australia, 34 healthy term infants were studied at 2 weeks, 3, 6, 12, and 24 months in a prospective longitudinal cohort study. The study mentioned that there was limited data on reference ranges for normal nocturnal oxygen in infants, but that they aimed to develop a cumulative frequency (CF) reference-curve. This curve may be used as a tool to compare a child’s nocturnal oxygen saturation to see if the infant falls within the range for infants that are similar in age (Figure 1). Overall, the median nocturnal saturation was between 98 and 99 percent, for infants living at sea level.6 

In an additional study, conducted at high altitude in Bogotá, Colombia, 122 healthy full-term infants were studied in 4 various groups. These groups were coupled differently and were only monitored until 18 months of age. The groups were <45 days, 3 to 4 months, 6 to 7 months, and 10 to 18 months. In addition to these groups, 50 infants completed three overnight PSG studies and were analyzed as a longitudinal sub-cohort.

In this study, their overall data was presented differently and they also looked at SpO2 during wakefulness and respiratory events, which are more likely to occur at higher altitudes. An interesting finding, that was not present in the study at sea level in patients of similar size, age, and weight, was the increase in total, central, and obstructive apneas. In addition, there were also very high frequency oxygen desaturation events that again are not seen when living at lower altitudes. These events were reported as normal in infants living at high altitude. Overall, the median SpO2 was between 92 and 94 percent at high altitude.7 

To conclude, the median oxygen saturations at sea level were between 98 and 99 percent and between 92 and 94 percent at high-altitude. This said periodic breathing, which is normal until six months of age at any altitude, causes transient desaturations and are more common at high altitude. Apneic events are more commonly seen in infants at altitude, but are considered normal.  These studies have offered reference ranges and tools to better aid clinical judgement when caring for a patient that may require oxygen.

Felicia S.


1. Oxygen saturation. Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. (2003). Retrieved March 23, 2019, from

2. Hypoxemia. The American Heritage® Medical Dictionary. (2007). Retrieved March 23, 2019, from

3. Wise, M., and Glaze, D. (2018). Sleep physiology in children. UpToDate. Retrieved March 23, 2019, from 

4. MacLean, J.E., Fitzgerald, D., & Waters, K. (2015). Developmental changes in sleep and breathing across infancy and childhood. Pediatric Respiratory Reviews, 16(4), 276-284.

5. Hanyang Medical Reviews. 2013 Nov;33(4):190-196.

6. Terrill, P., Dakin, C., Hughes, I., Yuill, M., & Parsley, C. (2015). Nocturnal oxygen saturation profiles of healthy term infants. Archives of Disease in Childhood, 100(1), 18-23. 

7. Duenas-Meza, E., Bazurto-Zapata, M., Gozal, D., Gonzalez-Garcia, M., Duran-Cantolla, J., Torres-Duque, C. (2015) Overnight Polysomnographic Characteristics and Oxygen Saturation of Healthy Infants, 1 to 18 Months of Age, Born and Residing at High Altitude (2,640 Meters). Chest, 148(1), 120-127.

Sleep at Altitude

Reported Sleep Disturbances

Many travelers report a decrease of quality of sleep when traveling from sea-level to high altitudes. Newcomers to altitude typically describe trouble falling asleep and frequent wakings throughout the night.7 One study determined that 46% of 100 Iranian ski tourists reported frequent awakenings and other sleep disturbances such as insomnia during their first night sleeping at 3,500 m.5,7 Another study analyzed data from reports of 305 Chinese soldiers transported from 500 m to 3,700 m in Lhasa and found similar results. Approximately, 32% of the soldiers reported insomnia in the first night at altitude and 74% of 246 workers who were air-lifted to the South Pole at 2,835 m reported difficulty falling and staying asleep throughout the first week.1

Change in Breathing Pattern

Many theories state that the “periodic breathing pattern,” common during sleep at high altitude, is a potential cause of sleep disturbances. Periodic breathing is a form of Cheyne-Stokes respiration and reflects changes in neural signaling due to hypoxia and alkalosis during sleep.4 Hypoxia is a respiratory stimulant while alkalosis is a respiratory depressant.4 This mixed signaling is the source of the altered breathing during non-REM sleep encountered at altitudes over 2500 m. The frequency of periodic breathing during sleep increases as the altitude increases.3,4,7

Decreased Sleep Efficiency 

Compared with sea level, several studies have depicted that sleep at higher altitude is characterized by decreased sleep efficiency, prolonged superficial stages of sleep, and reduced stages of deep sleep.12 The image below is a qualitative representation of sleep structure recorded at sea level and at high altitude. The area encircled by the outer line reflects the time in bed and the area of the shaded inner pie chart the time asleep.7,13 The fractions of superficial stages of sleep are symbolized by “NR1&2,” the fractions of deep non-rapid eye movement sleep are represented by “NR3&4,” and the stages of  rapid eye movement sleep are exemplified by “REM.”

Fig. 1. Depicts a qualitative comparison of sleep quality at sea level vs. altitude > 1,500 m13

Shift in Brain Waves 

Everyone is aware of the importance of quality of sleep when it comes to memory processing. One study has associated a decline in sleep-related memory consolidation with the decrease in slow wave-derived encephalographic measures of neuronal synchronization in healthy subjects observed overnight at high altitude.15  Another study by Stadelmann et al. discovered that quantitative spectral analysis of frontal and central EEG derivations reflected an altitude-dependent decrease in slow wave activity.14

Daytime Performance

A study, analyzing sleep disturbances experienced by lowlanders with obstructive sleep apnea during a stay at 2,590 m, discusses the association between sleep disturbances with poor performance in driving simulator tests.11 Studies performed at altitudes of 3800-3900 have revealed that supplementing with nocturnal oxygen improves daytime performance in neuropsychological tests, increases overall sleep quality, and reduces the occurrence of periodic breathing. 9,10 Although further studies are needed, the stated findings suggest that altitude-related alterations in sleep may negatively affect overall daytime performance.7

Can We Acclimate to High Altitude? 

Over time, research points to some sort of acclimation concerning sleep at high altitude; although research analyzing acclimation is very limited. Studies analyzing altitudes between 4,5559 m to 6,835 m have determined that the frequency of periodic breathing increased with the time spent at high altitude altitude.2,12 Opposingly, in studies at lower altitudes such as 1,650 m, 2,590 m and 3,450 m, periodic breathing decreased from the first to the second night.6,8 These observations suggest that there is an altitude-dependent effect of acclimatization on sleep structure. Interestingly, the same study that determined an increase in periodic breathing with time spent at an altitude of 4,559 also noted a decrease in arousal index and normalization of nocturnal oxygen saturation with increased time spent at high altitude.12 Stadelmann et al. determined that there was a statistically significant increase in the number of sleep cycles at higher altitudes with the longer the stay at altitude.14

Dr. Ebert-Santos’s Decision to Continue the Research

Despite recent advances in our understanding of sleep at high altitude, further research is needed to understand how demographics may alter sleep at high altitude, to determine the process of sleep-acclimatization, and to uncover the characteristics of sleep in local-highlanders.7 Dr. Ebert- Santos continues to be an advocate for the Summit County community regarding the effects of high altitude on health and has decided to pursue a study researching the effects of altitude on oxygen saturation during sleep of adults ranging from the ages 25-65 years old. Stay tuned for her process, her results, and her conclusions! 

Caroline, PA-S


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