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Dr. Chris’s HAPE Cheat Sheet

Inflammation and altitude can cause low oxygen. Inflammation is commonly caused by viral infections such as colds or influenza, but can occasionally occur with bacterial infections such as strep throat or pneumonia. Low oxygen, or hypoxia, is the result of fluid collecting in the air sacs of the lungs, called pulmonary edema.

There are three types of high altitude pulmonary edema (HAPE).

  1. Classic HAPE, recognized for over a century. occurs in visitors to altitudes above 8000 ft (2500m) beginning during the first 48 hours after arrival. Symptoms include cough, congestion, trouble breathing, and fatigue, all worse with activity.
  2. Re-entry HAPE occurs in people who are living at altitude, travel to lower altitude, and develop symptoms during the first 48 hours after returning home
  3. High Altitude Resident Pulmonary Edema (HARPE) is a recently recognized illness that occurs mostly in children who have an underlying respiratory illness and live at altitude, with no recent history of travel. They have oxygen levels below 89 and lower but do not appear toxic. They are fatigued but rarely have increased work of breathing.
Parents are often worried their children won’t wear a canula for oxygen, but they don’t typically mind.

Treatment of HAPE is oxygen. There may also be signs of asthma or pneumonia which are treated with bronchodilators and antibiotics. Most people with pneumonia at altitude do NOT have hypoxia. All three types of HAPE can reoccur, but typically not with every arrival at altitude or viral illness. Many of these patients are told they have pneumonia again and again, or severe asthma, and are treated with inhalers and steroids. Usually, this adds nothing to their recovery.

A chest x-ray may show typical infiltrates seen with pulmonary edema, but in mild or early cases, can look normal. There is no blood test for HAPE. Oxygen should be used continuously at a rate that raises the oxygen saturation into the 90’s. Length of treatment may be as short as 2 days or as long as ten days

Most importantly, owning a pulse oximeter and measuring oxygen levels in anyone at altitude with symptoms of cough, congestion, fatigue and trouble breathing with exertion can keep people out of the ER and ICU. HAPE can rapidly progress to respiratory failure and death if not recognized and treated expediently.

Section House in December: Moose Country

Section House sits at 11,481′ (3499 m), on Boreas Pass, just south of Breckenridge, Colorado. It isn’t the highest hut in the Summit Huts system, but its unique location and history is what makes it one of the most challenging.

Many of the huts in the Summit and 10th Mountain Division systems sit on a hillside, below tree line, which provides a significant amount of weather mitigation. Section House is right at the tree line, on the pass, which means any wind and weather will likely be funneled right into you. And because you are in one of the highest counties in the United States, weather is highly variable.

I’ve done this hut in a blizzard before, arriving to find the padlock on the front door was frozen shut. That may have been the most I’d ever despaired in my life up until then.

Even in great weather, however, the temperature alone is a liability. When we set out from the trailhead this time, it was sunny and relatively balmy for December, in the 30’s (Fahrenheit). But the temperature in the shade can be several degrees lower, and as the sun sets below the Ten Mile Range, the temperature starts to drop by the tens of degrees really quickly.

The Stats

Distance: a little over 6 miles; GPS and some maps may differ by tenths of a mile. If you tell your friends 6, they may resent you.

Timing: the same hike has taken me a couple hours with no weight on my back besides water, on well-packed snow. This time, it took over an hour a mile, including frequent breaks, thanks to all the weight I was carrying and pulling. Additionally, we constantly had to redistribute weight among sleds and backpacks to relieve shoulders and keep sleds from tipping over. If you decide to pull a sled, keep the weight low and as evenly distributed as possible. The other very limiting factor was the last half of the trail was covered in at least a couple feet of unpacked, fresh powder. Our lead was breaking trail in snowshoes.

While the grade going back down to the trailhead isn’t steep enough to keep momentum without skating, it is significantly easier and faster, and took us half the time even after waiting for moose to safely cross our path.

Elevation gain: about 1100′.

Capacity: 12 people.

Packing

I’ve pulled a sled both times I’ve done this hut. I don’t regret it, but it is challenging at best in calm weather. Unless you are going for more than a couple nights, I’d recommend packing everything into a backpack.

Because the elevation gain is so gradual, the challenge with weight is the distance. Pack your weight so it will still be comfortable on your shoulders after three miles. The advantage of pulling a sled was having less weight on my shoulders, but after several miles, even minimal weight can dig into your muscles.

The only source of water around this hut is the snow you melt, which is why it isn’t open in the Summer season. Water purifying filters are the quickest way to refill all your containers at the hut, but you will want plenty of water for the hike in alone. Running out of water on the trail is dangerous. An added risk: when the sun went down on us after the first three hours in, the water in our CamelBak nozzles started freezing if we weren’t regularly sipping on them.

Bring a sleeping bag. Most huts I’ve been to have blankets and pillows on the mattresses, but this one does not. This is also one of the oldest and coldest cabins; built in 1882, it takes hours to heat up by wood stove, especially if no one has been in it recently.

Moose

Now forget all the advice I just gave you and center your whole packing strategy around how you plan to evade a charging moose.

This region is moose country: high, high meadows filled with willowy wetlands. They don’t care how cold it is. In the dead of night, one of us opened the front door to use the outhouse and a young bull was standing right in front. On the trail back, two different parties ran into a moose and her calf right on the trail. They are not in the way. You are on their trail.

But seriously, pack to be prepared for your comfort and sustenance on the trail and at the hut. The only thing you can do about the moose is give them a lot of space while avoiding any confrontational, jerky movements that may suggest any predatory intent. If moose perceive a threat, they are liable to charge, male or female. If they charge, drop everything weighing you down and pray-run (praying while running).

When we ran into the moose on the trail, we stayed over 50 meters away and just waited while the moose wandered further off our path. As soon as they were about 50 meters off our path, we proceeded with caution. But we waited for over 30 minutes, and would have waited longer if we needed to.

Skis vs. Skins vs. Snowshoes

This was the most highly contested logistical conversation among our party. In the end, four of us were on cross country skis (without skins), one was on skis with skins, one was on a split-board with skins, and one was on snowshoes.

This really depends on the conditions. Two weeks prior, three of us hiked the trail in boots, on well-packed snow after days of warm, dry weather. Days before we left for the trip, however, a series of storms blew several feet of snow in, which changed everything. Boots alone were definitely not an option.

Most people, who aren’t hiking to the hut, will stop and turn around at the halfway mark where historical Baker’s Tank stands. This means the trail up until that point will reliably be pretty packed down. Because of the recent snow, however, no one could be sure what conditions would be like for the second half of the trail.

Freshly-broken trail through fresh snow past the midway point to Section House.

Sure enough, Baker’s Tank to the hut was unbroken trail through deep, soft snow. Our lead, on snowshoes, was cursing all the way to the hut as he carved the path for the rest of us. But in deep snow, snowshoes are sometimes the most comfortable option for an ascent, especially if you are inexperienced on skis and skins.

The advantage to skinning up on a split-board or downhill skis is the width of the blades. They are wider than cross country skis, which makes balancing the extra weight more comfortable and stable.

On a packed track, cross country skis were relatively comfortable, if narrow. The boots are more similar to normal footwear, so are more flexible and comfortable than ski or snowboard boots. Price was also a determining factor: renting skis or a split-board can cost upwards of $45 per day at most rental shops. We found cross country skis for $10 per day at Wild Ernest Sports, above Silverthorne, and they worked well. One thing about cross country ski boots, however, is that they aren’t as well-insulated as downhill ski or snowboard boots. Trekking through deep snow in them requires much better waterproofing and insulation than we were prepared with.

Jupiter rising in the dusk on the way up to Section House.

As for skins, although the trail grade is very gradual, there is enough of a grade at times that you will be thankful for the traction that skins provide. So unless you’re on cross country blades, you’ll want some skins.

Altitude & Acclimatization

One advantage of carrying all the weight we did was that it forced us to make a slower ascent and take frequent breaks. These are two things you can do to minimize the affects of the altitude on any ascent. In our party, all but one of us have lived at an altitude over 7,000′ for at least one year. Most of us have lived over 9,000′ for several years. But this was the first hut trip over 10,000′ for three of us, one of whom flew in two days before from sea level.

Fortunately, no one in the group experienced any severe symptoms of acute mountain illness, and I credit that to our meticulous supervision of each person’s blood oxygen saturation as well as our slow ascent. The first night we were at the hut, the lowest oxygen saturation we saw was 85%, but most were between 85 and 90%, which, at over 11,000′ is not surprising. If some slow, deep breaths hadn’t brought oxygen levels up, I would have been more concerned.

Hitting kickers behind Section House.

As seems to be tradition on our expeditions, we arrived well after dark. But these days, sunset is at 4:30 pm. Luckily, the weather was calm, and the trail is quite obvious. Our biggest concern after dark was the tremendous drop in temperature. With no cloud cover and a recent cold front, it was well below freezing, and the only thing that kept us from freezing was the constant movement, which kept us progressing forward.

Ken’s Hut, next to Section House.

By the time we had all made it to the hut and built up a fire warm enough to kick our boots off, our socks were steaming in spite of how cold our extremities were. It took well into the night to heat up the hut, and we all spent the first night sleeping around the wood stove. Yes, it took seven hours for the last of us to make it to the front door of Section House, but the spring trip to the Benedict Huts outside of Aspen was still loads more difficult — and we didn’t even pull any sleds! The next day was windless, sunny, clear, and warmer outside than it was inside, which allowed us to get back out on our skis and snowboards to enjoy the backcountry without weight on our backs.

robert-ebert-santos

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.

Increased Risks of Orthopedic Surgery at Altitude

With orthopedic surgeries becoming more common at higher altitudes, it is important that we understand the increased risks of surgery at higher elevations. Patients locally (Eagle, Summit, Pitkin, Grand, Lake and other high-altitude counties in Colorado) and those that travel from all over the world to undergo surgery by our orthopedic surgeons are at an increased risk for complications post-surgery. Patients that have surgery at a lower altitude and return to higher elevations post-surgery are also at higher risk for post-operative complications. These risks are higher for everyone having surgery at altitude regardless if you live at higher elevations or are from sea level.

High altitude is defined as 8-12,000 feet. However, increased surgical risks are seen starting at 4000 feet. There are no differences for increased risk if you are acclimated to the altitude (live here) or are visiting. The increased risk of surgery at high altitude is the same for all.

High altitude increases the coagulation state of blood (clotting ability) and hyperventilation (breathe out more than you breathe in), and oxygen saturation of blood and tissues is 10% lower at high altitude compared to low altitudes, leading to a hypoxic state. The hyperventilation state promotes the hypercoagulable state which causes the immune system to respond with a pro-inflammatory state. Acclimation does occur, we adapt, are able to breathe easier and function normally as our bodies make more red blood cells to compensate for the lower available oxygen in the air. However, the hypercoagulability of blood remains, because the hyperventilation state is sustained at high elevations (even if you live here). At high elevations there are physiological differences in pulmonary circulation (blood through the lungs), heart function, and fluid imbalances which induce dehydration that accompanies blood changes contributing to the increased risk of surgery at high elevations.

Risk factors for blood clots from orthopedic surgery for the general population include: decreased mobility or sitting around more, length of surgery (greater than 4 hours increases blood clot risk), joint replacements, smoking, diabetes, and other illnesses.

In general, there is a 40-60% chance of a blood clot following knee or hip replacement surgery. At altitude that risk doubles. There is a 3.8 times greater risk of thromboembolism (blood clots) for knee surgeries at high elevations. Total shoulder replacement surgery also demonstrates a 2-times greater risk of pulmonary embolism at altitude or 39.5%, compared to a 15% chance at sea-level. For rotator cuff repair of the shoulder, there is also an increased risk for blood clots. There is a 1.4-times greater risk for pulmonary embolism (blood clot in the lungs) for lumbar fusions at high altitude. Higher elevation is an independent risk factor for blood clots which lasts up to 90 days post orthopedic surgery.

Anesthesia at high altitude has its own risk. The sustained hyperventilation state at high altitude also leaves the patient more vulnerable to hypoxia and pulmonary edema with anesthesia. These risks can be minimized, however remain elevated for surgeries requiring general anesthesia above 4000 feet.

For patients returning to high altitude following surgery at lower elevations, there exists multiple risks due to hypercoagulable state, increased inflammatory response, and hyperventilation that higher elevations induce. Acclimatization to high altitude is lost within 2 days of being at a lower elevation and can take 3-4 months to achieve again. In as little as 2 hours after arriving at high altitude, the body initiates the above changes and this puts the post-operative patient returning to altitude at risk for a multitude of complications: dehydration, thromboembolisms, hypoxia, atelectasis, and pulmonary edema.

I recently spoke with a patient that grew up in Leadville (10,151 feet) and lives in Summit County (average of 7947 feet). She underwent hip surgery (twice) in Denver. Upon returning to Summit County, she developed high altitude pulmonary edema (HAPE) both times. When she underwent an ankle surgery in Edwards, the surgeon prophylactically treated her for high altitude sickness given her previous history. She did not develop HAPE, but was hypoxic and required oxygen therapy following surgery for a few days. She is a prime example that even those living their entire lives at altitude are susceptible to these increased risks from surgery.

These risks can be minimized by drinking plenty of fluids, using compression socks (TED hose) or sequential compression devices (SCDs), blood thinners (aspirin, Eliquis, or the like), doing ankle pumps and glute squeezes, and getting up and walking around every 1.5-2 hours for 10-15 minutes, all of which help decrease the likelihood that patients will experience blood clots following orthopedic surgeries.

To reduce respiratory or lung related complications it is important to do deep breathing exercises or incorporate the use of an inspirometer post-surgery, use supplemental oxygen if necessary, as well as continue to do these exercises after returning from a lower elevation for at least 2-3 weeks.

High altitude is an independent risk factor for orthopedic surgery complications. However, these increased risks have been seen in trauma patients and other surgical patients as well. The hyperventilation state, hypercoagulability, and elevated inflammatory response are not isolated to orthopedic patients, but exists in everyone living at and visiting higher elevations.

— Jessica Guthrie, BSN, RN

References

Cancienne, J., Diduch, D., & Werner, B. (2017). High altitude is an independent risk factor for postoperative symptomatic venous thromboembolism after knee arthroscopy: A matched case-control study of Medicare patients. Arthroscopy: The Journal of Arthroscopic and Related Surgery 33(2). https://dx.doi.org/10.1016/j.artho.2016.07.031

Damodar, D., Donnally, C., Sheu, J., Law, T., Roche, M., & Hernandez, V. (2018). High altitude an independent risk factor for venous thromboembolisms after total hip arthroplasty. Journal of Arthroplasty 33(8), 2627-2630. https://doi.org/10.1016/j.arth.2018.03.045

Damodar, D., Vakharia, R., Vakharia, A., Sheu, J., Donnally, C., Levy, J., Kaplan, L., & Munoz, J. (2018). A Higher altitude is an independent risk factor for venous thromboembolisms following total shoulder arthroplasty. Journal of Orthopedics 15(4). https://doi.org/10.1016/j.jor.2018.09.003

Donnally, C., Vakharia, A., Sheu, J., Vakharia, R., Damodar, D., Shenoy, K., & Gjolaj, J. (2019). High altitude is an independent risk factor for developing pulmonary embolism, but not a deep vein thrombosis following a 1 to 2 level lumbar fusion. Global Spine Journal 9(7) 729-734. https://doi.org/10.1177/2192568219828349

Tyson, J., Bjerke, B., Genuario, J., & Noonan, T. (2016). Thromboembolic events after arthroscopic knee surgery: Increased risk at high elevation. Arthroscopy: The Journal of Arthroscopic and Related Surgery 32(11), 2350-2354. https://dx.doi.org/10.1016/j.arthro.2016.04.008

Wani, Z. & Sharma, M. (2017). High altitude and anesthesia. Journal of Cardiac Critical Care 1(1), 30-33. https://doi.org/10.1055;s-0037-1604203

Doc Talk: The Art of Saving Vacations

In 1986, Dr. David Gray was asked to join a team of rafters on an exploration of the Yangtze River in China. Their goal, simple: to reach the undiscovered source of the Yangtze river and raft all the way down. Although simple is quite the understatement. The Yangtze River is the 3rd longest river in the world, and the source of the river is at approximately 19,000 feet (5791 m) above sea level. 

Dr. Gray, a young physician at the time, agreed to join the mission after being told by the mission frontman, Ken Warren, that “we want you there for trauma”. Dr. Gray, however, had an inkling that the high elevation could present some interesting challenges. He consulted with two pulmonologists, but at the time, understanding of treatment at high altitude was limited–he got little advice. With eagerness and reassurance that he would “have the final say on all things medical”, he began the mission. 

The team was comprised of an eclectic group of gentlemen. From 4 Chinese Olympic athletes, to a camera man from National Geographic, the crew set forth to uncharted territory. The took a bus up the first 14,000 ft, and they learned quickly about the effects of altitude. “Everyone was sick. I’m treating headaches with narcotics, treating vomiting with phenadrine, and guess what I had for pulmonary edema: lasix!” Despite the chaos, everybody improved and the crew trudged forward. 

In their slow ascent, there came a point when the snow was nearly six feet deep — vehicles were no longer an option. The rest of the mission would be on foot. On foot, with yaks carrying their gear, the crew moved up the glacier to what they presumed was the source of the river. The photographer from National Geographic, David Schippe, had not been doing well. As the mission progressed, Dr. Gray could hear crackles in the base of his lungs through a stethoscope and sent him down to receive medical attention. This was a case of  high altitude pulmonary edema (HAPE); he was diagnosed with pneumonia.

The rest of the crew reached the presumed source, “Tigers Leak Gorge”, which turned out to be one of the many Yangtze tributaries. On their decent down on “duckies”(blow-up rafts), they stopped at base camp and found David Schippe, the photographer that was supposed to have headed back to receive medical care. Their next checkpoint was at 11,000 ft; it was 600 miles away and they had no choice but to continue down with Schippe alongside. 

Unfortunately, this would be David Schippe’s last journey. “On the second day, Schippe started coughing; he gets very sick, and is put on IV. I said, ‘we need the helicopter,’ but there was no helicopter; that was all a lie. [Ken] had a short-wave radio, but he used the money for the emergency helicopter to pay his mortgage.” Dr. Gray, feeling the weight of this terrible deception, knew this would be the end of Schippe’s life.

We buried him on the river.

Dr. Gray distinctly remembers Ken Warren, the expedition leader’s announcement of their crew member’s death.

He said, ‘Dave’s dead. Suck it up, or you could be next.’

That was confirmation to Dr. Gray that this mission was not being run with any regard for crew safety. When they got to their checkpoint, Dr. Gray said “adios”. 

And so went Dr. Gray’s introduction to Altitude Medicine.

Fast forward to today, in a local brewery, Dr. Gray, equipped with the wisdom of 20 years of practice in Summit County, Colorado, after 25 years of Emergency Medicine in Corpus Christi, Texas, shares some of the essential knowledge for working in the hypoxic conditions of high altitude. An advocate for accessible and affordable health care, much of his practice involves bringing his medical services straight to his patients.

Has anything changed about what you put in your medical bag since you first started doing mobile health care?

No. I had a select group of medications I use that cover almost everything. I get an antibiotic prescription, so I can hand them their ZPak (my “go-to” medication).  I carry ventil, decadron, nubain (a synthetic narcotic) — it has some narcotic antagonist effects, so you have to be careful if you put someone on opioids on it, because it’ll put them in immediate withdrawal — Benadryl, and epinephrine.

First case of HAPE in Summit County?

He was from Scotland or somewhere in the British Isles. I sent him to the hospital, he gets in the ambulance, spends two days in the ICU in Denver, and $30K later, they send him back up!

Dr. Chris mentions that even physicians in Denver aren’t always familiar with high altitude care, and can order extensive testing for symptoms that are classic presentations of high altitude pulmonary edema. 

I got a guy from Austin; he was in his late 40’s. He had pulmonary edema, and  his O2 sats were maybe in the 70s. I said, ‘you need to go to the hospital, get out of the altitude, and go to Denver.’ He said, ‘I don’t want to leave my family, do I have to leave?’

I told him, ‘I’m going to work with you, but you have got to do everything I say. I’ll be back in the morning to give you another dose of decadron and you don’t get to sue me if this doesn’t end well.’

I see him the next day, give him another shot of decadron. He was one of the first people I allowed to stay at altitude. I wouldn’t leave anybody with that treatment if I couldn’t get him up to the high 70s.

Dr. Gray typically puts these patients on oxygen full-time at approximately 5 liters, monitors them closely, and finds patients’ oxygen saturations will typically go up into the 90’s.

I got confident with what I was doing.

He also makes a point that it’s essential to re-check vitals in these patients and to pay attention to symptoms. Too often, patients present with an acceptable oxygen saturation, around 93, and end up coming back hypoxic:

The oxygen can present normal initially because patients are hyperventilating! The respiratory muscles cannot maintain that work of breathing, and later, their oxygenation will drop! 

Dr. Gray and his own family have had their own experience with re-entry HAPE, as well:

We were back in Texas for a few weeks. I took them to the [alpine slide] back in Breckenridge, and Dillon (Dr. Gray’s son), who always got headaches, comes up to the car and throws up a bunch of red vomit. I told his sister, ‘Please tell me he drank a red soda before this.’ (He had.) Then we go home and he’s just feeling bad. I just figured, it’s his headache, or it’s a viral bug, then luckily, I put him in bed with me. At about 10 pm that night, he was coughing so much it was keeping me up. I put a stethoscope on him, and it was like a washing machine! His oxygen was 38!

I put him on five liters of oxygen and he quit coughing. The cough reflex was there because the lungs were trying to do anything to get more oxygen!

It’s not that the pulmonary edema was getting better quickly, necessarily; it took about three days for him to get better.

It ain’t about water; it’s diet.”

What I believe happens when you come two miles in the sky as abruptly as people do: most Americans are dehydrated anyways. When they get here, the body goes into defense mode. It shunts blood and oxygen into your heart and kidneys and consequently … away from your stomach. Then, they (visitors) eat restaurant portion meals and greasy steaks on vacation. That’s why vomiting is sometimes the primary symptom. 

What I tell people is if you stop in a restaurant on your way up here, choose high carb, low fat, low protein meals — carbs are easy to transport through the system. Choose smartly, eat half of what they put on your plate, and take the rest home. The last meal should be at 5 pm. 

Also, alcohol is a mild diuretic at best! The real issue is that it’s a respiratory depressant! If you need to drink on this trip, drink in the morning!

Who gets acute mountain sickness? 

Young fit males. They come up here with a resting pulse of 52 beats per minute. A well-exercised person can’t get their heart rate up to counteract hypoxia. Then they ignore their symptoms because that’s what athletes do. As for athletes, I’ve given up on that. They go 100%, and they are not going to hold back.  

Another point that Dr. Gray emphasized was the seasonal factors: 

We see a marked difference in acute mountain sickness in Winter and Summer. You are by necessity in a hyper-metabolic state in the cold. Your body is working hard using oxygen to stay warm.  Plus, people are overusing muscles they haven’t used all year. In the summer, they come up in cars and ‘meander’ up. In the winter, they fly and ascend within hours. [Ages ago], you didn’t see any altitude sickness because they came on donkeys! Very slowly! 

And if you’re not sick by day two, you probably won’t be.

By the age of 50:

Everyone who lives here should sleep on oxygen. If you haven’t been here for generations, you need to be on night time supplemental oxygen. The only exception to this is in COPD patients due to oxygen deprivation driving respiration and CO2 retention.

I tell full-time residents, ‘you need an oxygen concentrator.’ It’s a night time problem. During the day, you’re ventilating. At night, you go into a somnolent state and your breathing goes down.

Muscles are healthier when you use them, that goes for the heart too. We (Summit county residents) are hyper-dynamic, cardiac-wise. If you supplement with oxygen at night, you keep the process of pulmonary hypertension from developing. 

Advice to the Traveler

Diamox: it changes your acid base chemistry, acidifying your serum, which, essentially, turns you into your own ventilator. Some people are aware of their increased respiratory depth and it may bother them. 125 mg twice a day, beginning two days before travel. Any dose greater than that will just increase side effects. 

The Water Issue: you can’t make up for chronic dehydration during the day. The biggest loss of fluid from the human body is insensible loss – moisturizing the air you breathe! Altitude also produces diarrhesis, as well as a lot of intestinal gas. The poor bacteria in your GI are also hypoxic.

Talking Altitude Medicine with Dr. David Gray

Dr. Gray opened his own practice in Breckenridge, CO caring primarily for travelers. With the motto “We save vacations,” he expresses a true passion for the demographics of the population and practice at high altitude. He developed his practice by networking closely with local ski industry workers, from lifties to ski shop employees, and provides fee for service immediate care to his patients. 

Autumn Luger is a physician assistant student at Des Moines University. She grew up in the small town of Bloomfield, Nebraska where the population of cattle vastly outnumbered humans. From there, she moved on to study biology and chemistry and eventually receive her bachelor’s degree at the University of Sioux Falls in South Dakota. She enjoys leisurely running, competitive sports, hikes in beautiful locations, attempting to bake, thrift shopping, and expressing creativity through art. Since being in Summit County, she has discovered some new interests as well: snowshoeing, hot yoga, and moonlit hikes.

Doc Talk: Nutrition & Oxygen as Preventative Medicine

Dr. C. Louis Perrinjaquet has been practicing in Summit County, Colorado’s mountain communities since the 80’s, when he first arrived as a medical student. He currently practices at High Country Health Care, bringing with him a wealth of experience in holistic and homeopathic philosophy, such as transcendental meditation and Ayurvedic medicine, as well.

This past week, Dr. Chris managed to sit him down over a cup of coffee in Breckenridge to talk Altitude Medicine. And not a moment too soon, as PJ is already on his way back to Sudan for his 11th trip, one of many countries where he has continued to provide medical resources for weeks at a time. He’s also done similar work in the Honduras, Uganda, Gambia, Nepal, and even found himself out in the remote Pacific, on Vanuatu, an experience overlapping Dr. Chris’s own experience spending decades as a physician in the Commonwealth of the Northern Mariana Islands.

Experience is everything when it comes to High Altitude Health. I asked PJ if there was any such thing as a “dream team” of specialists he would consult when it came to practicing in the high country: more than any particular field, he would prefer physicians with the long-served, active experience that Dr. Chris has in the mountain communities.

Complications at altitude aren’t always so straight-forward. Doc PJ sometimes refers to the more complex cases he’s seen as “bad luck”, “Not in a superstitious way,” he explains, but in “a combination of factors that are more complex than we understand,” not least of all genetics and hormones.

At this elevation (the town of Breckenridge is at 9600’/2926 m), he’s seen all cases of High Altitude Pulmonary Edema (HAPE): chronic, recurring and re-entry. The re-entry HAPE he sees is mostly in children, or after surgery or trauma, which Dr. Chris speculates may be a form of re-entry HAPE.

He’s seen one case of High Altitude Cerebral Edema (HACE), a condition more commonly seen in expeditions to even more extreme elevations (see our previous article, Altitude and the Brain). In this case, “a lady from Japan came in with an awful headache, to Urgent Care at the base of Peak 9 … she lapsed into a coma, we intubated her, then flew her out.”

How common are these issues in residents?

It’s probably a genetic susceptibility. More men come down with HAPE at altitude, or estrogen-deficient women. Estrogen may protect against this. When I first moved up here, we used to have a couple people die of HAPE every year! The classic story is male visitors up here drink on the town after a day of skiing, don’t feel well, think it’s a cold, and wake up dead. A relatively small number of the population up here has been here for decades. Most move here for only 5 – 10 years; even kids [from Summit County] go to college elsewhere, then move away.

In addition to hypoxia, severe weather and climate are also associated with extreme elevation. Do you observe any adverse physiological responses to the cold or dryness, etc. at this elevation?

Chronic cold injury probably takes off a few capillaries every time you’re a little too cold.

At this, Dr. Chris chimes in, “People who have lived here a long time may have more trouble keeping their hands and feet warm.”

Do you have any advice for athletes, or regarding recreation at altitude?

Don’t be an athlete up here very long. Don’t get injured. You can train yourself to perform a certain task, but that might not be healthy for you [in the long term]. Really long endurance athletes – that might not be good for your health, long-term. I see chronic fatigue often, they kinda hit a wall after years: joint issues, joint replacement, …

We’re observing a relatively recent trend with many high altitude and endurance athletes subscribing to a sustainable, plant-based diet. We’ve also encountered a lot of athletes consuming vegetables and supplements rich in nitrates to assist with their acclimatization. Do you have any experience with or thoughts on these techniques?

Eat a lot of fruits and vegetables, not a lot of simple carbohydrates, not a lot of refined grains. Eat whole grains. I’ve been vegan for a while; it’s been an evolving alternative diet.

Do you ever recommend any other holistic or homeopathic approaches to altitude-associated conditions, healing or nutrition?

Why don’t you get some sleep? Eat better? Don’t drink? Pay attention to your oxygen? Sleep with air? … If you’re over 50 and plan to be here a while, you might sleep on oxygen. I can’t imagine chronic hypoxia would benefit anyone moving here over 50. It may stimulate formation of collateral circulation in the heart, but we’re probably hypoxic enough during the day. It might benefit athletes that want to stimulate those enzymes in their bodies, but even that would be at a moderated level, not at 10,000 ft.

We’re onto something here: Dr. Chris has seen a lot of benefits in some of her patients sleeping on oxygen. If you haven’t already heard, Ebert Family Clinic is currently deep in the middle of a nocturnal pulse oximeter study, where subjects spend one night with a pulse oximeter on their finger to track oxygen levels as they sleep. This will provide more data on whether certain individuals or demographics may benefit from sleeping on oxygen.

In the case of pulmonary hypertension, probably 50% of people who get an electrocardiogram may experience relief from being on air at night. Decreased exercise tolerance when you’re over 50 might be a good case for a recommendation. I don’t think we ever have ‘too much oxygen’ up here; ‘great levels of oxygen at night’ are about 94%. Humans evolved maintaining oxygen day and night [in the 90s], same with sodium, potassium, etc., at a fairly narrow tolerance.

Are there any myths about altitude you find you frequently have to clarify or dispel?

Little cans of oxygen! it’s predatory marketing! It’s so annoying! We’re littering the earth and taking people’s money for ‘air’! Just take some deep breaths, do some yoga for a few minutes … sitting for 30 minutes at an oxygen bar might help. There’s no way to store oxygen in your body, so within 15 minutes, it’s out, but the effects might last, but it gives a false sense of security. 

Also,

IV fluids! DRINK WATER! Or go to a place where you can get real medical care. Most vitamin mixtures, or ‘mineral mojo’, is not real. First of all, don’t get drunk! Drink way less. Dr. Rosen, a geriatric psychiatrist, sees a lot of older guys with MCI (mild cognitive impairment), they’ve had a few concussions, have a drink a day and have lived at altitude for a while. He sees more of these guys here than at low altitude. It’s part of my pitch for guys to sleep on oxygen and minimize alcohol. We don’t have the science to take one or two drinks a week away, but just add oxygen.

Do you have to change the way you prescribe medications due to altitude? Has anything else changed about your practice after moving to altitude?

I don’t [prescribe] steroids as much. Even if it’s rare, I don’t think [steroids] are as benign as other doctors. I avoid antibiotics if possible.

Do you yourself engage in any form of recreation at altitude? How has the altitude played a role in your own experience of this?

I didn’t exercise much until I was 40. [Now] I trail run in the summer, which I think is better than road running (‘cave man’ didn’t have completely flat pavement to run on for miles and miles). In the winter, I skin up the mountain almost every morning; [also] mountain biking. 

Ease in to exercise gradually. Exercise half an hour to an hour a day, but do something every day, even if it’s 10 minutes. And don’t get injured.

Doc PJ also has a handout he most often refers his patients and visitors at High Country Health to, here.

robert-ebert-santos

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.

High Country Healthcare’s Guide to Altitude and Acclimatization

Welcome to Summit County! At the high elevations of the Colorado Mountains, everyone is affected by altitude to some degree. As you go to higher altitudes, the barometric pressure decreases, the air is thinner and less oxygen is available. The air is also dryer and the ultraviolet rays from the sun are stronger. At elevations of 8,000 plus feet your body responds by breathing faster and more deeply, resulting in shortness of breath, especially on exertion. Many people develop mild symptoms of headache, nausea, trouble sleeping, and unusual tiredness, which we call acute mountain sickness or AMS. These symptoms usually go away in a day or two. If symptoms are severe, persist or worse, you should consult a doctor. A short visit to a physician may save the rest of your vacation.

A more serious condition is called high altitude pulmonary edema or HAPE. This condition is recognized by a wet cough, increasing shortness of breath, and the feeling of fluid building up in your lungs. Other symptoms may include disorientation or confusion. If you feel any of these symptoms developing you need to seek medical attention immediately. HAPE is easy to treat but can be life threatening if left unattended.

The effects of high altitude can be decreased by following these recommendations:

  • Increase Fluid Intake – drink two or three times more fluid than usual, water and juices are best; adequate hydration is the key to preventing altitude illness. You should drink enough fluids to urinate approximately every two hours.
  • Avoid alcohol and minimize caffeine on your day of arrival and one to two days thereafter; be very careful if consuming alcohol, and remember, at this altitude, you may be much more sensitive to the effects of alcohol and sedatives (caffeine and alcohol are dehydrating).
  • Decrease salt intake – salt causes your body to retain fluid (edema), which increases the severity of altitude illness.
  • Eat frequent small meals high in carbohydrates, low in fat, and low in protein.
  • Moderate physical activity and get plenty of rest.
  • Medications and oxygen can help you feel much better. Diamox is a prescription drug which prevents the unpleasant symptoms for many people. Recent experience suggests that a small dose of Diamox suffices: 125 mgs in the morning before you arrive at altitude, again that evening, and each morning and night for two days after arrival. It is generally a well tolerated medicine with few side effects. It should not be taken by anyone who is allergic to the sulfa class of medicines. Some people may experience a tingling sensation in their fingers, toes and around their mouth. You may also notice a subtle change in your sense of taste; especially carbonated beverages may taste flat. As with any medication, take only as directed and discuss any potential side effects with your physician.
  • Studies have shown that spending 1 -2 nights at a modest altitude of 5000 – 6000 feet decreases symptoms when you go higher.
  • The effects of the sun are also much stronger at high altitudes, even in cold weather! Be sure to use sunscreen of at least SPF 15 to avoid sunburn.
  • Have fun and enjoy the mountains!

**This was taken from a handout provided by Dr. C. Louis Perrinjaquet at High Country Healthcare in Summit County, Colorado.**

Sickle Cell Anemia at Altitude: a Case Report

Martin, a 27-year-old African American male, presents to a rural mountain hospital with complaints of left upper quadrant abdominal pain. Martin arrived at altitude (9,400 feet) two days ago from Oklahoma City after a 12-hour drive. Shortly after arriving to his condo in the mountains, Martin developed a dull aching pain to his left upper quadrant. The pain is constant but radiates to his L flank intermittently. Martin tried snowboarding today but had to end his day early because the pain became too severe. Martin cannot identify any aggravating or relieving factors and states that ibuprofen “didn’t even touch the pain.” Martin denies associated nausea, vomiting, diarrhea, constipation, urinary symptoms, fevers, chills, enlarged lymph nodes, or fatigue. His medical history is significant sickle cell trait without active disease. He has a negative surgical history, takes no daily medications, and has no known allergies. *

Differential diagnoses considered include kidney stones, pancreatitis, gastritis, diverticulitis, splenic enlargement, an infarcted spleen, or mononucleosis. Laboratory tests ordered include a complete blood count, reticulocyte count (indicator of immature red blood cells production), lactate dehydrogenase (an indicator of red blood cell destruction), haptoglobin (a binding protein that binds free hemoglobin after red blood cell destruction), a complete metabolic panel, and a urine analysis. A CT scan of the abdomen with contrast was also ordered and performed. 

Martin’s results showed an elevated white blood cell count, sickled cells on his blood smear, mildly elevated reticulocyte count and lactate dehydrogenase, low haptoglobin, and an elevated bilirubin. The remainder of his blood work was unremarkable. The CT scan showed a 40% infarction of his spleen. Martin was treated with oxygen, fluids, and IV pain medication and was promptly transferred to a larger hospital at lower elevation. 

What caused all of this to happen? 

Sickle cell anemia (SCA) is a mutation of the HBB gene that affects the development of normal hemoglobin, the major oxygen transporting protein in the body. SCA is an autosomal recessive genetic disorder which means that two copies of the abnormal gene have to be passed on from both parents in order for the disease to be active in the offspring. So, in other words, if both parents are carriers of the abnormal gene, their offspring have a 25% chance of developing the active disease and a 50% chance of becoming carriers themselves. 

http://www.healthnucleus

The hemoglobin protein is made up of four subunits, 2 alpha-globin and 2 beta-globin. Sickle cell carriers will have a mutation of one of the beta-globin units, resulting in no clinical manifestations of the disease. These individuals live normal lives and are virtually unaffected by the mutation, as seen in Martin’s case. Individuals with active disease will have a mutation in both of the beta-globin subunits, creating sickling of their red blood cells. Sickling of red blood cells makes them less flexible in maneuvering through the vasculature, ultimately resulting in a blockage of blood flow to various tissues in the body. This is cause of severe pain that many individuals experience when in crisis. Sickled cells are also more prone to destruction leading to an anemic state and are inefficient oxygen transporters. 

https://www.flickr.com/photos/nihgov/27669979993

The sickle cell mutation is typically found in certain ethnic groups which is thought to be related to the protective quality of sickled cells from the development of Malaria. The ethnic groups most likely to be affected include African Americans, Sub-Saharan Africans, Latinos, Indians, Individuals from Mediterranean descent, and those from the Caribbean. 

But if Martin was a carrier without active disease, why did he develop sickle cell anemia?

Individuals with the sickle cell trait can cause their cells to sickle under extreme stress including during strenuous exercise, severe dehydration, and when at high altitude. The resulting consequence is the manifestation of all of the symptoms of active disease. Although Martin had never had any symptoms related to his sickle cell trait, he was now in full sickle cell crisis that required immediate intervention. 

What are the implications? 

Individuals from any of the ethnic groups listed above should be tested for the sickle cell trait to ensure they are not carriers. A carrier must exercise extreme caution in ascending to high altitude, should stay well hydrated, and avoid strenuous exercise to prevent the development of a sickle cell crisis. 

*Case scenario is not based on any individual patient rather a compilation of varying presentations seen in the emergency department. 

Liya is 3rd year Doctor of Nursing Practice Student attending North Dakota State University. She lives in Breckenridge, Colorado and works as a registered nurse in the Emergency department. Liya was born in Latvia and moved to the United States in 1991 with her family. She grew up in the Washington, DC area until she moved to Colorado in 2012.  She is passionate about helping immigrant families and other underserved individuals gain access to basic healthcare services. She hopes to work in Family Medicine in a federally qualified health center in the Denver metro or surrounding areas. In her spare time, Liya enjoys hiking, snowboarding, biking, and camping. 

References

Adewoyin A. S. (2015). Management of sickle cell disease: A review for physician education in Nigeria (sub-Saharan Africa). Anemia, 2015. doi:10.1155/2015/791498

American Society of Hematology. (n.d). Sickle cell trait. Retrieved from https://www.hematology.org/Patients/Anemia/Sickle-Cell-Trait.aspx

Mayo Clinic. (2018). Sickle cell anemia. Retrieved from https://www.mayoclinic.org/diseases-conditions/sickle-cellanemia/symptoms causes/syc-20355876

U.S National Library of Medicine. (2019). Sickle cell disease. Retrieved from https://ghr.nlm.nih.gov/condition/sickle-celldisease#inheritance

Yale, S.H,, Nagib, N., & Guthrie, T. (2000). Approach to the vasoocclusive crisis in adults with sickle cell disease. American Family Physicians, 61(5), 1349-1356. Retrieved from https://www.aafp.org/afp/2000/0301/p1349.html

Open Call for Interviews on Parkinson’s at Altitude

Earlier this year, our students published some articles on Parkinson’s disease at altitude. One was an account of patients experiencing some relief from their symptoms at high altitude, and another involved a local couple in our region of the Rockies.

We’ve since received a lot of attention to these articles specifically and would like to hear from more people who have any feedback to share about their experience at altitude with Parkinson’s disease.

Feel free to send us an e-mail – admin@ebertfamilyclinic.com

The Legacy of the Mountain Guru: Prof. Dr. Gustavo Zubieta-Castillo

We’ve published a series of accounts from Dr. Chris’s recent attendance at the 7th Annual Chronic Hypoxia conference in La Paz, Bolivia , conducted by Dr. Gustavo Zubieta-Castillo. He is one of the world’s leading experts of altitude medicine and Dr. Chris’s collaboration and contact with him has added literally phenomenal insight into our own high altitude research.

Dr. Chris “en Teleférico” with fellow altitude researchers Vanessa Moncada, Diana Alcantara Zapata, Dzhunusova G. S., Oscar Murillo, and Alex Murillo. Photo courtesty of Dr. Zubieta-Castillo.

There is something literarily romantic about the scientists who are compelled to remind you, “I’m not crazy!” Dr. Zubieta-Castillo has held soccer games at 6,542 m (21,463′), proving the remarkable adaptability of the human body. He maintains a high altitude training lab, called the Chacaltaya Pyramid, at 5,250 m (17,224′). In his recent video (below), he illustrates the connection between longevity and elevation, where citizens of the highest cities in South America live to be well over 100.

It’s notable that a city known for its wine at 2,790 m (9,153′), called Chuquisaca, boasts some of the oldest residents. Not surprisingly, our research has led us to some speculation on the relationship between alcohol and the body at altitude. Additionally affirming is Dr. Zubieta-Castillo’s father, nicknamed “El Guru de la Montaña”, who began his legacy of altitude research and medicine by examining the hearts of dogs at altitude (sound familiar? See our article on Dogs at Altitude), as well as Dr. Zubieta-Castillo’s own testament that asthma can be and has been treated by altitude (see Asthma at Altitude).

His latest correspondence with Dr. Chris and their mutual colleagues reads like letters written by history’s greatest scientists, beginning,

Dear Colleague Scientists:

The 7th Chronic Hypoxia Symposium, thanks to your outstanding participation was a great success !! We shared great scientific, friendship and enthusiasm from 16 countries, along with travel and conferences in fascinating environments, all at high altitude.

The letter ends with an invitation to all colleagues to contribute their own research to the first chronic hypoxia-dedicated issue in a top medical journal, so be on the lookout for Dr. Chris’s contribution (which we will be sure to share here).

The video below is a fascinating look into some of Dr. Zubieta-Castillo’s latest research, including his theories and recommendations on conditioning humans in space with hypoxia, a dissertation that was initially dismissed as irrelevant, then subsequently published. Enjoy!

robert-ebert-santos

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.

Closer to the Sun: The Dermatological Benefits and Consequences of Living at High Altitude

As many of us know, high-altitude living goes hand-in-hand with a multitude of outdoor activities like biking, hiking, and skiing. But with all that outdoor activity comes an insidious risk: radiation from the sun. According to an article interviewing Kim Guthke PA-C, a Physician Assistant working in Dermatology in Boulder, CO, “living at a higher elevation exposes us to approximately 25 percent more ultraviolet radiation when compared to sea level” (Guthke 2018). This means that with all the outdoor activities we enjoy, we must also be proactive about protecting our skin from high altitude sun and the increased risks of long-term skin issues it brings. 

Using thick UV-protectant clothing, sunglasses, and sunscreen (and reapplying it) are great ways to protect our skin from the sun. However, some new research has argued that we are actually hurting our health by staying away from the sun. In a revelational article from Outside magazine called “Is Sunscreen the New Margarine?”, Rowan Jacobsen uncovered a novel study claiming only the sun can provide the vitamin D we need. He claims that we are trying and failing to supply vitamin D with pills alone, and the pills just aren’t good enough. Vitamin D is a vitamin required for calcium absorption whose levels, if low, can increase one’s risk of “cancer, diabetes, obesity, osteoporosis, heart attack, stroke, depression, cognitive impairment, autoimmune conditions, and more” (Jacobsen 2019). Thus healthcare workers have concluded that supplementing it will obviously decrease the risk of these diseases. 

Jacobsen reports that multiple different studies have proven that supplementation of vitamin D just isn’t enough to lower that risk. The studies reported that even if supplementation raised vitamin D levels, the general health of the patient did not improve. There was no correlation between high supplemented vitamin D levels and overall health.

So, why was this?

Jacobson claims that vitamin D is actually just a marker for overall health. In other words, raising vitamin D by artificial supplementation does not make one healthier; rather, to raise one’s vitamin D level one must live a healthy lifestyle outside in the sun. Jacobsen states, “…what made the people with high vitamin D levels so healthy was not the vitamin itself. … Their vitamin D levels were high because they were getting plenty of exposure to the thing that was really responsible for their good health — that big orange ball shining down from above” (Jacobsen 2019). 

Soaking up the Vitamin D on Lake Dillon.

So, what are the implications of this study? Does this mean we all need to stop using sunscreen in order to absorb the most natural form of vitamin D and subsequently decrease our risk of dangerous diseases? Well, yes and no.

Yes, in that the best way to absorb vitamin D is from the sun and sunscreen does inhibit that absorption.

No, in that one day of playing at the beach and getting horribly sunburnt is not going to raise your vitamin D levels enough to benefit your health.

Unfortunately, the answer is quite complicated. I believe the implication of this new information is that we all need to start getting outside every day, exercising, enjoying the mountain air, and absorbing small amounts of sunlight each day, rather than just enjoying a single session of baking our skin to blisters. Living at high-altitude, I hypothesize that we don’t need as much time to absorb the same amount of beneficial sunlight as we would at sea level, so I feel there is still a need for sunscreen and protective clothing, if outside for an extended period. We should all try to absorb the sun’s rays daily, but we need to do it in a healthy way.

Cooling down on the way up Uneva Peak off Vail pass.

I encourage everyone to read Jacobson’s article, as it has points both for and against protection from the UV rays of the sun. In the meantime, there is one point Jacobson makes that I would like to argue. 

In his article, Jacobsen admits that increasing sun exposure does increase the rate of skin cancer, but then claims this is ‘okay’ because, “Skin cancer kills surprisingly few people: less than 3 per 100,000 in the U.S. each year … People don’t realize this because several different diseases are lumped together under the term ‘skin cancer.’ The most common by far are basal-cell carcinomas (BCCs) and squamous-cell carcinomas (SCCs), which are almost never fatal” (Jacobsen 2019). The reason I’m disagreeing with this point is due to my direct experience with the “non-fatal” skin cancers. I spent 12 months working with a board-certified dermatological surgeon performing Mohs micrographic surgery, a delicate and precise surgical procedure to remove said cancers from the face, ears, scalp, fingers and toes. Although it’s true BCCs and SCCs are rarely fatal, they can cause significant damage to one’s image. Depending on the location and size of the cancer, a “non-fatal” SCC in-situ has the potential to cause extensive disfigurement of the face, ears, or eyes. I strongly believe this is not something to take lightly, and I fear that saying skin cancer is non-fatal creates a false sense of security. This can be especially dangerous in high-altitude where the sun’s rays are exceptionally stronger than the majority of the US. 

All in all, I do believe that the sun is incredibly beneficial to our health, though in moderate portions. Living in the Colorado mountains gives us more opportunities to enjoy the mountain air, along with the sun, and allows us to lead healthier lives in general. I don’t think I’m going to stop using sunscreen in the near future, but I do know I won’t be so afraid of the sun anymore. I definitely won’t be letting the sun keep me from enjoying my time here in Colorado!

Delaney Schara is a Physician Assistant student at Des Moines University in Des Moines, Iowa. She hails from Fergus Falls, Minnesota, and obtained her undergraduate degree in Chemistry at Augustana University in Sioux Falls, South Dakota. Delaney gained valuable experience in medicine by working as a medical scribe in Dermatology prior to beginning PA school. After completing her pediatrics rotation with Dr. Chris, Delaney will have rotations in multiple Midwestern states before her graduation in June 2020. Delaney is an avid musician who loves singing in choir, playing the flute, and playing acoustic guitar. She also enjoys tasting new blends of tea, exploring rural communities, and spending time with loved ones. 

References

Guthke, Kim. “Sun Protection at Higher Altitudes.” Boulder Medical Center, 29 August 

2018, www.bouldermedicalcenter.com/sun-protection-at-higher-altitudes/

Jacobsen, Rowan. “Is Sunscreen the New Margarine.” Outside Online, 6 June 2019

www.outsideonline.com/2380751/sunscreen-sun-exposure-skin-cancer-science?utm_source=pocket&utm_medium=email&utm_campaign=pockethits