As the gateway to Machu Picchu, the city of Cusco, Peru attracts over 3 million tourists from all around the globe each year. With this many people passing through the city, you can imagine why local residents feared the worst when the COVID-19 outbreak began. However, out of a population of approximately 429,000 people, the city has only four COVID-19 related deaths – three tourists who traveled to the area and one native with previous risk factors.
Machu Picchu
Machu Picchu, a UNESCO World Heritage Site, brings 3 million tourists from around the world to the Cusco region of Peru every year.
One death out of 196 confirmed cases for the city makes for a remarkably low fatality rate of 0.5% for the native population. Peru as a whole has a fatality rate closer to 3% with over 6,000 deaths, making it one of Latin America’s most affected countries. Many believe the fatality rate to be even higher as testing has not become widely available in the country.
To understand why Cusco is such an outlier when compared to the rest of the country, there are several factors to take into consideration. One of those factors that researchers haven’t quite been able to figure out, but believe plays a role, is altitude. The Cusco region of Peru sits at 11,152 ft elevation compared to the capital city of Lima that sits at only 512 ft elevation.
Research comparing the high-altitude regions of Tibet, Bolivia, and Ecuador has revealed similar trends. A study completed April 22, 2020 and published in the June 2020 scientific journal “Respiratory Physiology & Neurobiology” indicates that populations living above 9,842 feet elevation reported significantly lower levels of COVID-19 cases than populations living at lower elevations. The research showed the infection rates in the Andes Mountains of Bolivia were one third the infection rates the rest of Bolivia, and the infection rates in the Andes Mountains of Ecuador were one fourth of the rest of Ecuador. In both Bolivia and Ecuador, the areas with the highest concentration of COVID-19 cases were located at an elevation close to sea level.
At an elevation of 11,942 ft, La Paz, Bolivia is the highest capital city in the world.
Why populations living at higher altitudes are experiencing lower infection rates is still not well understood, but there are a few theories at play. It is hypothesized that people living at altitude are able to live in a state of chronic hypoxia, or a state of chronically low oxygen in the blood. Hypoxia is one of the conditions caused by COVID-19, and if a person’s body is already used to low levels of oxygen, their symptoms may not be as severe. There are other environmental considerations at altitude that may shorten the life-span of the COVID-19 virus, including high levels of UV radiation that can kill the virus, low barometric pressure that does not support the weight of the aerosolized droplets that the virus lives in, and dry thin air that does not support the transmission of aerosolized droplets.
However, as intriguing as the effect of altitude on COVID-19 statistics is, it is important to note that there are several other proven factors that come into play when looking at these populations. First, most high-altitude towns and cities tend to be rural. When population density per square mile drops, the rate of transmission of infectious diseases also drops – rural settlements allow for natural social distancing. Second, populations living at higher altitudes have lower rates of obesity and generally have better overall health. Living at high altitude causes a reduction in the hormones that signal hunger, leading to consumption of fewer calories. Additionally, completely normal daily activities in a state of chronic hypoxia due to low levels of available oxygen in the air raises the body’s resting metabolic rate, leading to burning more calories. The healthier a person is prior to contracting an illness, the more likely their body is to be able to fight it off successfully.
Research regarding how altitude affects COVID-19 transmission, infection, and recovery rates is ongoing. It may be too soon to tell exactly why or how altitude comes in to play, but early findings are suggesting that now is a great time to be a resident of the great Rocky Mountains – but then again, when is it not?
Megan Schiers is a 3rd year Physician Assistant student studying at Midwestern University in Glendale, AZ. She graduated from Idaho State University in Pocatello, ID with a Bachelor of Science in Dental Hygiene and worked as a dental hygienist in Strasburg, CO for two years prior to starting PA school. She is passionate about increasing access to healthcare in rural areas and hopes to specialize in emergency medicine or cardiothoracic surgery following graduation this fall. During her six weeks in Frisco, CO, she has enjoyed hiking in the beautiful mountains, camping at Camp Hale Memorial, visiting Maroon Bells, and checking out Black Canyon of the Gunnison National Park.
Last week we were privileged to have a Zoom discussion with two high altitude experts from the Instituto Pulmonar Y Patologia de la Altura (IPPA) founded in La Paz, Bolivia in 1970. Dr Gustavo Zubieta-Calleja and Dr. Natalia Zubieta-DeUrioste answered our questions about their recently published article, Does the Pathogenesis of SAR-CoV-2 Virus Decrease at High Altitude?. They and the seven coauthors presented data comparing COVID cases in high altitude areas of China, Bolivia and Ecuador showing a marked reduction in numbers compared to low altitude areas in the same countries, with dramatic, colorful topographic maps.
Drs. Zubieta-Calleja and Zubieta-DeUrioste and their colleagues theorized four reasons why altitudes above 2500 m could reduce the severity of the corona virus. (Note: Frisco, CO is at 2800 m, Vail 2500 m). As described in their previous paper published in March, the intense UV radiation at altitude as well as the dry environment likely reduce the viability of the virus in the air and on surfaces.
Dr. Zubieta-Calleja on a Zoom chat with Dr. Chris explaining a chart comparing UV exposure in La Paz, Bolivia (top line) and Copenhagen, Denmark (bottom line).
Dr. Chris with Dr. Gustavo Zubieta-Calleja and other altitude experts from the Hypoxia Conference in La Paz on the Camino Chacaltaya, which reaches an elevation of 17,785’/5421 m.
The low barometric pressure causes air particles to be spaced more widely, which would also decrease the viral particles inspired with each breath, reducing the severity and frequency of infections.
Furthermore, residents accustomed to chronic hypoxia may express reduced levels of angiotensin converting enzyme 2 (ACE2) in their lungs and other tissues. This enzyme has been found to be the entry path for the corona virus into cells where it replicates. Finally, the normal adaptation and acclimatization of populations with prolonged residence above 2500 meters may reduce the severity of the disease in individuals, and reduce mortality. This includes increased ventilation, improved arterial oxygen transport, and higher tissue oxygenation mediated by increased red blood cells produced under the influence of erythropoietin, which could be explored as a possible therapy.
Dr. Zubieta-Calleja with statistics reflecting the number of COVID-19 infections at different elevations in Bolivia. Note the most infections occur at a lower elevation.
As we stated in our interview quoted in the Summit Daily News March 17th, none of these factors can be relied upon to protect every individual. Therefore it is important to continue frequent hand washing, wearing masks, social distancing, and avoid touching your face.
Another Spring season in Colorado. The ski resorts have closed early per the COVID-19 protocol, along with most other establishments. Even on the normal schedule, most ski resorts would have been closed for the season by now, bringing more people to the backcountry. But this year seems to have seen an upswing in backcountry activity, where many people are going to stay active while limiting exposure to others. Just over a week ago, a team of 20 search and rescue volunteers rescued a 26-year-old man who had fallen hiking on steep terrain around St. Mary’s Glacier, Colorado. Last year, a total of 10 snowmobilers were killed in the backcountry in avalanche slides. Only one was wearing a beacon.
Backcountry and Avalanche Safety resources, thankfully, are growing more plentiful and accessible, and last winter, we published an article on the basics. Earlier this winter, I spoke with backcountry athlete and web development colleague Dan Beerman, whose experience in the backcountry really broadened as a backpacking guide in New Mexico during the summers 12 years ago, followed by a position as a climbing instructor.
Dan Beerman on the Pacific Crest Trail
When I was a backpacking guide, I was on the search and rescue if I didn’t have a crew … We had a radio, so we were the point of contact for finding and doing extraction. That’s when I learned the most and was exposed to the most. I took my Wilderness First Responder course in 2014, and that was through the Wilderness Medical Institute.
Dan’s also a fellow hut tripper, and we’ve been talking about doing one together (when we’re on the other side of the current pandemic). He’s spent the last two New Year’s in huts, backcountry skiing or snowshoeing tours. This past year, he skied Buffalo Mountain’s Silver Couloir, in the Gore Range, and made an attempt at a couloir on Mt. Torrey’s. And there have got to be some good “couloir” puns out there.
Beerman on Buffalo, Summit County, CO.
I have aspirations to do the Colorado trail quickly, but I don’t know if I wanna do that in a competitive way or just recreationally backpack it. It’s hard to balance summer objectives, or climbing objectives vs. winter backcountry goals vs. alpine mountaineering objectives.
And he makes a great point:
In Colorado, your recreation is so close to becoming high-consequence all of the time! If the weather changes from the trailhead, that could be a really big problem.
I’m familiar. Nothing really teaches you as much or as quickly as getting caught in Colorado’s extreme weather patterns.
Avalanche Safety
Dan took an Avalanche Awareness and Safety class through Colorado Mountain School, held up in Rocky Mountain National Park over two field days after two nights of class in Boulder. His main takeaway:
Check an avalanche conditions snow report daily. Observing the snowpack over the seasonis going to make your confidence on the day of your excursion a lot higher. I’d had no context for why avalanches were happening, where and why it’s dangerous. Having that lens through which to view weather events in terms of avalanche conditions is so valuable. It’s an intuitive thing about paying attention to the weather.
This is my first season getting out at Copper, for example, and they all have that double-black diamond terrain in the back bowls that are labeled ‘EX’ on it. There’s a sign that says, ‘Ski with a partner,’ and I just thought, ‘Oh, shit, that sign should probably be much bigger!’
Beacon, shovel, probe are the mandatory avalanche terrain items — you’re putting other people at risk if you don’t have [them], because even if you observe a slide, you can’t do anything about it. Additionally, if you don’t have a beacon in a slide, others can’t find you. You’re not contributing to a rescue, nor can you be rescued. In Colorado, there’s an increasing awareness for that. I typically will bring that with me all the time, it’s just always in my ski bag. Having some snacks, having some water, those are the kinds of things: you should never not have them.
Beerman in his beacon.
Training
I’ll take the goals of the expedition and plan accordingly. If I’m doing a ski trip, I’ll wanna get out and do hikes with weight or runs where I’m doing elevation several times. I like to do six weeks out, of four weeks of training and two weeks of tapering down.
Nutrition
I tend to be in a constant attempt to gain weight. On the Pacific Crest Trail I tried to gain weight prior, eating a lot of fatty foods, that kind of thing. Jonathan and I came up with this metric: calorie-per-dollar-per-ounce. Lightweight food that’s affordable, easy to ingest, easy to prepare, and you aren’t having to burn a lot to carry that with you to the backcountry.
[On the trail], peanut butter is always a winner. Olive oil is one of the highest calorie-per-ounce [food]. I have literally drank it before, but just add it to everything. I do eat a lot of standard trailmix, it’s easy and accessible. I’m a big fan of pumpkin seed mix or stuff with chocolate in it. I like CLIF bars. I do not like Luna bars because I’ve eaten so many of them. I can’t eat pop tarts anymore because they used to be in the meals that were issued when I was a guide. Snickers bars are a great calorie-per-dollar-per-ounce deal. I eat a Snickers bar or two before bed when I’m sleeping at altitude so my body has calories to stay warm.
I’ll make these mass-gainer complex food supplements. It’s like protein powder, but it also has carbs, like a workout and performance powder. And I would add that to water with coffee, and that would be a breakfast while hiking. There’s a lot of different kinds of powders and mixes you can add, but when you’re in calorie-burning mode, I do recommend this. If you’re hiking 20+ miles in a day or 4000+ feet of elevation in a day, you’re burning greater than 4000 calories, so you really have to eat more than you think you can.
Acclimatization
I wouldn’t say that I had HAPE (high altitude pulmonary edema) or HACE(high altitude cerebral edema) … Definitely, especially when I was younger … I would travel from 4000′ to 10,000′ in a 24-hour period. I’ve actually had search and rescues where someone was having night-terrors or hallucinations [due to HAPE or HACE]. I was a backountry professional for the Boy Scouts at a camp at 10,800′ (one of the first backcountry camps, in New Mexico). I’ve experienced dizziness, nausea, insomnia, weakness of the knees, elevated heart rate … and I’m a runner, I’m in decent shape. But you should acclimatize before setting out on a trip.
Skiing down the Silver Couloir.
One last piece of advice,
Learn the Leave No Trace principles. We live in a state where impact is so concentrated that the more that everybody knows, the more likely it will be there for the next generation.
Dan and his backpacking, backcountry cohorts keep a blog full of breathtaking landscapes and telling captions on CaptainsofUs.com.
There will be plenty of time to escape to the backcountry again after the risks of COVID-19 have subsided. The current time is a good time to start preparing mentally. Know before you go.
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.
A good friend in Hawaii recently sent me a YouTube video referencing Dr. Cameron Kyle-Sidell, a critical care and emergency room physician at Maimonides Medical Center in NYC. Dr. Kyle-Sidell was discussing his findings while working with COVID-19 patients in NYC and compared those findings to altitude sickness. I did a search and found he had posted several videos on social media comparing Acute Respiratory Distress Syndrome (ARDS) in COVID-19 patients to altitude sickness and reconsidering how these patients are treated. Altitude sickness is something I see and treat frequently here in Summit County. Based on the similarities between the two conditions, the same treatment for altitude sickness and high altitude pulmonary edema (HAPE)[1] may be beneficial to COVID-19 patients.
In an interview with Dr. John Whyte, Dr. Kyle-Sidell described the acute ARDS he is seeing in COVID-19 patients as atypical and not responsive to standard treatment, specifically in regards to ventilator use and settings. He describes some of his patients as alert, talking in full sentences, and not complaining of shortness of breath but have oxygen saturation levels in the 70s (John Whyte & Cameron Kyle-Sidell, 2020). Normally, that is not the case when a person has an O2 saturation[2] in the 70s and is in respiratory distress. However, this is not abnormal in patients with altitude sickness and HAPE. There are certain protocols in hospitals regarding when to intubate a person and to put them on a ventilator. According to Dr. Kyle-Sidell, these protocols apparently aren’t always helpful for COVID-19 patients with ARDS, and can at times be harmful.
The similarities between findings with COVID-19 and HAPE are remarkable. These similarities include: hypoxia (low oxygen levels), low CO2 (carbon dioxide) levels, tachypnea (rapid respiratory rate), patchy infiltrates seen on chest x-ray, bilateral ground glass appearing opacities on chest CT, fibrinogen levels/fibrin formation, aveolar compromise[3], decreased Pao2:FiO2 ratios[4], and ARDS in severe disease (Solaimanzadeh, 2020). Noting these similarities may be helpful when approaching treatments for COVID-19. Acetazolamide (Diamox), Nifedipine (Procardia) and Phosphodiesterase inhibitors (Viagra, Cialis etc.) have been used in treating HAPE and could possibly be beneficial in treating COVID-19. For example, Acetazolamide potently decreases the constriction of small vessels in the lungs that contribute to fluid build up (edema) seen in both HAPE and COVID-19 patients (Solaimanzadeh, 2020).
In our house call practice, we treat quite a bit of altitude sickness due to our elevation here in Summit County. During the ski season, we may see 3-4 patients per month that develop HAPE. The majority of the time, these patients can be safely treated and monitored in their residence or hotel room. Treatment for both altitude sickness and HAPE consists of oxygen, usually 2-5 L/min via nasal cannula continuously while sleeping or resting. We also treat our patients with an injection of a steroid, Dexamethasone. We closely monitor them and may repeat the dose of Dexamethasone or prescribe an oral steroid. These patients usually see some improvement by the next day and significant improvement when they descend in altitude. I have read recommendations for and against steroid use with COVID-19. More studies need to be done, which I will be following closely as future recommendations may change how I treat HAPE when there is also a suspicion of COVID-19.
The key to treatment is oxygen! We’ve seen patients with O2 saturation levels in the 40s and 50s and lungs that sound like a “washing machine”, as Dr. Gray, has described it (in a previous Doc Talk article). If we can get their oxygen saturation up into the mid 80s or 90s on 5L/min (of O2) or less via nasal cannula, typically, they can avoid an ambulance ride and emergency room visit. As Dr. Kyle-Sidell notes, many of the COVID-19 patients he sees are talking coherently and not in severe respiratory distress. A friend who is an EMT in New York described a man he recently transported to the hospital, in his 50’s, with presumed COVID-19. He had no respiratory distress, walking and talking coherently, no chronic medical problems but his oxygen saturation was in the 60s. He said they took him to the emergency room and he was intubated and placed on a ventilator. Apparently, this is a common occurrence from what he has seen. I am still amazed when a patient calls, gives me their address and directions to where they are staying and when I arrive, their oxygen levels are in the 40s. It is a very rare occurrence that I need to send a patient to the hospital, which they always appreciate. We monitor our patients very closely until their departure and have them call anytime, day or night, with any changes in condition.
Dr. David Gray, who started our business, has been treating these patients for over 18 years. He states that in a few of the HAPE patients that he has treated, including his own 13-year-old son, he has seen O2 saturations in the 30’s & 40’s. In these few patients, he was only able to get their O2 saturation up to high 60’s, low 70’s, on 5 liters. They were so much improved, clinically, that he accepted those levels. A large dose of Dexamethasone & 12 hours of rest, on nasal oxygen, resulted in marked improvement by the next day, every single time. His rule, as in patients with DKA, is “if the pathology didn’t happen rapidly, you don’t necessarily have to reverse it rapidly.”
Dr. Kyle-Sidell suggests not putting COVID-19 patients on ventilators based solely on numbers (John Whyte & Cameron Kyle-Sidell, 2020). Treating these patients with prone positioning, oxygen via nasal cannula, high flow on a non-rebreather mask or CPAP[5] along with careful monitoring and a little patience may be preferable to a ventilator (John Whyte et al, 2020). If a ventilator is needed, using less pressure to reduce lung damage and higher oxygen levels may prove to increase the likelihood of a better outcome (John Whyte et al, 2020). There is so much to learn about COVID-19 and how to treat it. Treating it as you would with HAPE is certainly something to consider. I appreciate providers who are sharing their personal experiences in treating these patients. As healthcare providers gain more experience treating this virus and share their experiences, protocols will change and I suspect ventilator use as well as the death rate will decrease.
[1] A complication of altitude sickness in where the lungs fill with fluid and small amounts of blood
Danielle Shook MSN, NP-C is a board-certified Family Nurse Practitioner. She has been in nursing for over 27 years. She earned her Master’s Degree at University of Colorado, Colorado Springs through Beth El School of Nursing. Her nursing experience includes 10 years in Obstetrics and 7 years in Hospice home care. She has over 9 years experience as an NP which includes Family Practice at the Air Force Academy, Urgent Care, Acute and after hours care with the Army Premier Clinic as well as house calls.
References
John Whyte, Cameron Kyle-Sidell. Do COVID-19 Vent Protocols Need a Second Look? – Medscape – Apr 06, 2020.
Solaimanzadeh I (March 20, 2020) Acetazolamide, Nifedipine and Phosphodiesterase Inhibitors: Rationale for Their Utilization as Adjunctive Countermeasures in the Treatment of Coronavirus Disease 2019 (COVID-19). Cureus 12(3): e7343. doi:10.7759/cureus.7343
Dr. Peter Lemis is a cardiologist in Summit County, CO. He sat down with us in December to share his experience treating heart patients in the mountains.
Summit County cardiologist Dr. Pete Lemis
I graduated medical school in ‘77, practiced internal medicine in New Rochelle, New York, the first county just north of the Bronx. Then I went to New Hampshire for three years. I was reading the New England Journal and saw an unexpected cardiology opening at Henry Ford Hospital in Detroit. Next I was in Pittsburg for 26 years practicing cardiology. Decided I wanted to retire to Colorado, so I built a vacation home here only to discover I didn’t have to wait to retire to move here, so I came five years ago.
What is it about high altitude and the heart that makes it healthy for heart patients?
Summit is the fifth highest county in the US with the highest population of those counties. The 21 highest are all in Colorado. Lower air pressure means that although there is 21% oxygen in the atmosphere, there are fewer oxygen molecules. So every breath we take is giving us less oxygen, unless we breathe faster and deeper to make up for it, a natural tendency for people. They don’t even think about it. Some people have hypoxia without shortness of breath. Every once in a while, I’ll see a patient who moved to altitude for work or something, and they’re hypoxic. It is probably genetic that some people have a decreased central respiratory drive.
These patients with low oxygen often are ordered to have an echocardiogram. When they first come up here, they usually won’t have pulmonary hypertension. For some, the decreased central respiratory drive develops not when they first move here, but years after they move here. They become more and more hypoxic without having the feeling of shortness of breath. They have the same physiological response that people with hypoxia get. Their pulmonary vessels are still being constricted, which is reversible if diagnosed and treated with oxygen supplementation during the first few years of high altitude living. If not treated they are likely to get scarring of their pulmonary vessels. The length of time for this to develop is different for different people, and is unpredictable.
For example, I had somebody just this week who’s been here about 2 years who has a resting oxygen saturation of about 82% at 60 years old.
We can’t tell who is susceptible to this problem. There are likely some genetic factors involved. Dr. Johnson, who recruited me for my job in Summit County, has been here since 2008. He warned me about the issue of high altitude and hypoxia. Most doctors who are unfamiliar with life at high altitude think you adapt and that’s it. Dr. Johnson said to me, “wait three months and test yourself and your wife with an overnight oximetry to see if there’s hypoxia.” Based on that test I started using nocturnal oxygen and I sleep better when I use it. My wife doesn’t need it. Neither does her mother, who is 90 years old. Neither do my sons.
Awake, we’re able to maintain our oxygen levels, but at night when asleep most people who are here in Summit County have low oxygen. Hence my advice is to get a nocturnal pulse oximetry test. Low oxygen for several hours every night over the years can lead to pulmonary hypertension due to the narrowing of the pulmonary arteries. Then there is the question of what is normal: most high altitude studies were done in La Paz with indigenous, adapted populations as opposed to people living in the mountains of Colorado who have been here years or decades. (See what Dr. Chris has written on her collaboration with physicians and scientists in La Paz, Bolivia.)
We asked Dr. Lemis about arrhythmias at altitude. There are two categories-atrial (from the top chamber) and ventricular (from the bottom chamber).
Studies have shown that cardiac arrhythmias are increased initially, but people become acclimated after about 3 – 5 days and the risk returns to baseline. I don’t think these studies have been conducted over enough time. Hypoxia leads to an increase in arrhythmias. I see a lot of atrial fibrillation and atrial flutter up here; plus, I send three to four patients a month for an electrical procedure to ablate some of the cardiac conduction pathways to get rid of their arrhythmias. Many patients experience relief from atrial arrhythmias when put on nocturnal oxygen.
JB is a 70 year old who has lived at high altitude for 14 years. He experienced atrial fibrillation several times after returning to Summit County from a trip to sea level. He wore a heart monitor for over a month to see how his heart was beating. He felt the atrial fibrillation was related to dehydration and has prevented further episodes, never needing a pacemaker or other treatment. Jim uses a device that monitors his oxygen and heart rate continually while he sleeps, downloading a written report in the morning.
Why do so many people who live up here have bradycardia?
I think because many are athletes. Athletes often have an efficient heart; I see just as many people who have tachycardia because they have low oxygen. Low oxygen causes higher levels of epinephrine. This stimulates their adrenal gland, which can increase their blood pressure. Many people have high blood pressure at high altitude because they have low oxygen. One of my criteria for testing someone for low oxygen at night is if they have high blood pressure.
Many people have central apnea during sleep at altitude caused by the brain’s blunted response to high CO2 and low O2. Similar to obstructive sleep apnea, this central sleep apnea can increase the risk of heart problems. Many people with obstructive sleep apnea here at high altitude need to have oxygen put into their CPAP machine so they get oxygen, rather than just airwith continuous positive airway pressure.
There is less fatal ischemic heart disease up here. People tend to be healthier, more athletic. They’ve moved here for an active lifestyle. There’s less cigarette smoking, more exercise, generally better diet (not always), but people up here still have heart attacks. My impression is more of them survive their heart attacks because of their increased physical activity and healthy lifestyle. They have better collateral flow with more capillaries in the heart. They’re protected to some degree. The corollary to this is the fact that when visitors come here and have heart disease, I don’t think that their cardiologist back at low altitude understands high altitude risks and therefore are unable to provide appropriate medical advice. The same amount of exertion here is much harder on the heart, much more stressful to the heart, than it would be at low altitude. There’s something called a double product when you do an exercise test, related to blood pressure and heart rates. You get the same double product causing the same stress on the heart here as at low altitude, but it takes much less exertion to get to a specific double product.
People who are accustomed to a certain work load at home come up here and try to do the same amount of exertion. If they have coronary artery disease, suddenly there is a middle aged guy with coronary disease having a cardiac ischemic event, perhaps even sudden cardiac death.
Another important point is that people with known heart disease who live at low altitude, if they’re unstable at all, they shouldn’t be up here within three to six weeks of a heart attack. They should be able to pass a stress test at low altitude before coming to high altitude to visit.
Valvular heart disease patients who have not been treated with surgery, who don’t already live up here, shouldn’t come up here from lower altitude. People with heart failure can come up here if the failure is compensated.
For people who have trouble acclimating to high altitude in the short term, Diamox is quite useful. Using oxygen at night helps you acclimate as well. Diamox makes your blood a little acidotic which increases your respiratory drive.
Avoid alcohol when you first come to high altitude. Unfortunately people on vacation don’t do that. Alcohol is a respiratory suppressant. At high altitude the hypoxia and cold promotes diuresis, so people tend to get dehydrated. Anti-inflammatory drugs are useful in treating the acute altitude sickness for some people. During the first two or three days, try not to push your physical activity to the limits. Try to get a good amount of sleep.
I would say that I have way fewer heart failure patients [up here]. Because patients who develop advanced heart failure really do not do well here, so they tend to move away to lower altitude before that happens. I have younger patients as compared with my former Pittsburgh practice. I also have way fewer patients with COPD. Anything that causes chronic respiratory difficulties you will find a lot less of that up here. Plus, I’m working in an environment where there are less consultants.
Back in Pittsburg, two thirds of my practice was taking care of patients in the hospital, so I would deal with patients who would come in with a heart attack, with a heart failure exacerbation, or other acute cardiac problem. Here in Summit County, those severely ill patients get transferred down to Denver, so I provide more in-office preventive or post-illness follow-up than I do care in the hospital. My patients who need advanced procedures (e.g. heart catheters, ablation for arrhythmias), I generally send them down to our sister hospital (St. Anthony in Lakewood).
The cardiac surgeon who will do the bypass surgery usually knows that the patient returning to the mountains will have to be on oxygen for two weeks after surgery.
“Day 10: I walked for maybe an hour up to Camp 3 (19,258’/5870 m) from Camp 2 (18,200’/5547 m). I became the slowest person. I had tunnel vision. It was bad. It took a lot of willpower. I do a good job of not telling people how bad I really feel. After about a mile, I told them I had to stop, and me and Logan turned around. We had that conversation,
‘I don’t think I should go up anymore. It’s not safe for me, and it’s not safe for the group.’
Barely able to move, about an hour above Camp 2.
“The others didn’t go all the way to Camp 3, but continue on a bit more. Angela said she got a headache really bad and couldn’t see out of her right eye. I had already pretty much decided — I was devastated — after two nights and two days of not acclimating. Alejo had a stethoscope and said my left lung was crackling. We thought I might develop some really serious pulmonary edema.”
Keshari Thakali, PhD is an Assistant Professor in the Department of Pediatrics at the University of Arkansas for Medical Sciences in Little Rock, AR. She is a cardiovascular pharmacologist by training and her research laboratory studies how maternal obesity during pregnancy programs cardiovascular disease in offspring. When not at work, you can find her mountain biking, rock climbing, hiking or paddling somewhere in The Natural State. She has a long-term career goal of merging her interests in mountaineering with studying cardiovascular adaptations at high altitude. She has climbed to some of the most extreme elevations in the Rocky Mountains, Andes and Himalayas. Last December, she flew down to Mendoza in Argentina for an ascent up Aconcagua.
Sacred in ancient and contemporary Incan culture, and the highest peak in the Americas, Aconcagua summits at 22,837′ (6960 m). Current statistics show only 30 – 40% of attempted climbs reach the top of this massive mountain in the Andes, in Principal Cordillera in the Mendoza Province of Argentina.
Sunset on Aconcagua from Base Camp.
The day following Keshari’s decision not to summit, she hiked back down to Plaza de Mulas (14,337’/4370 m) from Camp 2, carrying some of her colleague’s gear that he didn’t want to take up to the summit as he continued to ascend. Plaza de Mulas is a large base camp area with plenty of room for tents, available water, and large rocks that provide some protection from the wind as climbers take time to acclimate before continuing their ascent.
“Even though my oxygen [saturation] was low, I was functional. As you go down, everything gets better. The others continued up to Camp 3. They spent one night there, then summited the next day. It took them 12 hours.
“The day the others came back to Plaza de Mulas, I think that’s when everything hit me. I felt like a zombie. I did some bouldering and got so tired I had to sit down and catch my breath often, probably because I had been hypoxic and we were at over 14,000′.
“[The next day] we did the really long hike from Plaza de Mulas all the way to the entrance of the park. It probably took about 8 hours to walk all the way to the park entrance.
“We drove to Mendoza that night. I felt like my body was tired, but my muscles were functioning just fine. It’s hard to describe.”
They had done everything right and had taken every precaution. Each of Keshari’s colleagues boasted significant backgrounds in climbing and mountaineering, their cumulative accomplishments including Mt. Elbrus (18,510’/5642 m), Cotopaxi (19,347’/5897 m) and Denali (20,335’/6198 m), their ages 30 to 65. They weren’t initially planning to hire porters, “but they ended up carrying a lot of our stuff. In the end, it just makes sense to hire these porters to increase your chance of success.”
They gave themselves about two weeks to make the ascent and return. There was ample time for them to stop at each camp and spend time acclimatizing, including day hikes to the nearby peaks of Bonete and Mirador.
“Day 4 [we did an] acclimatization hike to Bonete (16,647’/5074 m), pretty much the same elevation of Camp 1. You look at the mountain and it looks pretty close, but … in mountaineering, you don’t do distances, you do time. Did the hike in mountaineering boots, which were heavy and clunky, but I learned how my boots actually work. You walk differently in these than a shoe with a flexible sole. The last part of the mountain is pretty rocky and it looks like you’re almost to the top, but you still have to walk an hour to the summit. It took about five hours to go up. We were walking slow, I felt fine. From the top of that mountain, looking away from Aconcagua, you can really see Chile and the Chilean Andes.”
Summit of Bonete.
All the way through their first week of climbing, including a day of resting and eating after their hike up Bonete, Keshari was feeling fine.
“Day 8, we made the push to Camp 2 (18,200’/5547 m). None of these hikes made me tired. I was plenty trained. We were carrying packs, but they were still pretty light, packed with stuff for the day. We spent the night at Camp 2, took oxygen mostly at night. [My] first reading at Camp 2 was low. We were at over 18,000′. I thought maybe I’ll just go to sleep and it’ll get better.
Looking down on Camp 2 covered in snow.
“Day 9 was a rest day at Camp 2 because the weather was really bad. All I did was sleep that day. If you’re gonna go to Camp 3, that means you’re gonna do a summit push the next day, because Camp 3 is so high. You’re just struggling to stay healthy. I felt really bad in the tent, but if I went outside to pee or walk around, I felt better. My pulse ox was still pretty low that day. That night, a snow storm blew in and it snowed a lot.” And it was the following day of their ascent to Camp 3 that Keshari made the decision not to summit.
Since returning from her expedition, she’s reflected on some other variables. “I swear I was hyponatremic (an abnormally low concentration of sodium in the blood). We went through four liters of water a day with no salt in the food. I was having these crazy cramps in my abs and my lats and places I don’t typically get them. To me, that has to do with electrolyte imbalance. Next time, I’m taking electrolyte tablets, not just stuff to mix in my water.
“I’m not very structured in my diet. In general I eat pretty clean, but I don’t count calories. I eat vegetables, but I also hate going grocery shopping. I feel like I eat a pretty balanced diet. If I buy meat, I’ll buy a pack of chicken and that’s my meat for a week or two.
“On the mountain, in general, I felt like they fed us way more fiber. In Argentina, they eat a lot of meat. They’re meat-eaters. They didn’t feed us steak on the mountain, but … at Base Camp, I felt like they were overfeeding us. We had pork chops one night, but on the mountain, I felt like it was mainly lentils and noodles. Even though you’re burning calories, how your body absorbs them is different. They really try to limit your salt intake because they’re concerned about having too high blood pressure. At Base Camp, breakfast was always scrambled eggs with bacon and toast. Lunch and dinner were always three course meals starting with a veggie broth soup. They fed us like kings … I brought Clif blocks with caffeine in them for hiking snacks, Lara bars.”
I ask about her main takeaway from it all:
“I think I need more time to acclimate. I don’t know how much more time, but maybe more time at about 16,000′. Maybe take Diamox. Someone suggested I should have been on an inhaled steroid, especially because my asthma is worse in the cold. If I were to go next time, I would want a couple more days at 15,000 – 16,000′. Maybe the Diamox is something I would need to use next time.
“The nerd in me wants to measure pulmonary wedge pressures (via very invasive catheters; you could go through the jugular), nothing practical,” she laughs. “The pulse oximeter is the easiest tool.”
One last thing she’d do differently? One of her colleagues bought a hypoxic generating system from Hypoxico, “which I think puts CO2 back into your system; sleeping high, training low. That might have been the best thing.”
Keshari went sky-diving back in Mendoza the day after returning from their descent. “I was expecting a lot of adrenaline jumping out of an airplane, but there was none. I enjoyed the freefall, but when the parachute went up, I got really nauseous. Maybe I had just been stressed for so long, there was no more adrenaline left. I was like, ‘Where’s the risk involved in this?'”
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.
It has everything to do with how well the body functions at increasing elevation. In Summit County, Colorado, we live at an average elevation of 9000′ (2743 m). Most bodies start a significant physiological response to 8000′ (2438 m). Even healthy athletes experience shortness of breath during certain activities that wouldn’t be noticeable at lower elevations. The body compensates by circulating more oxygen-carrying red blood cells, because there isn’t as much oxygen packed into each breath you take. Heart rate increases, you take quicker breaths, speeding up your ventilation. You are hyperventilating. If you manage well enough for a couple weeks, your body will eventually start creating more red blood cells to circulate more oxygen throughout your body at all times. This process will peak at about three months.
We often get questions about the canisters of oxygen sold at convenience stores, souvenir shops and gas stations across Colorado and whether or not they make any difference. There is a 100% consensus among every physician, athlete, EMT and ski patroller we have ever interviewed that they do not.
Why not? Dr. Chris has been practicing medicine at 9000′ for 20 years in Frisco, CO, so I asked her a couple of the questions that have come up at our clinic and on our blog recently and frequently.
How much oxygen is needed to actually mitigate symptoms of altitude sickness?
For someone with low blood oxygen saturation, our target would be 90% . They should be put on a concentrator or a large tank [of oxygen]. The adult dose is 2 to 4 liters per minute, the pediatric dose can be between 1/4 L per minute and 1 L per minute, 24 hours a day, for up to a week, or until their oxygen saturation can maintain at 90%. Less than that, and usually, it will drop again after 10 minutes off oxygen; and it’ll often be lower when you sleep, too.
What if I bought ten of these canisters of oxygen available at the gas station and breathed all of them in, one after the other. Would that make a difference?
You might get three hours worth of oxygen if you bought ten of those store-bought cans, which might help an altitude sickness-induced headache. But again, your oxygen would likely drop shortly thereafter, and you would be experiencing the same symptoms.
What happens if someone struggling with acclimatization also contracts COVID-19 or another disease with associated respiratory complications?
We don’t know. Their oxygen requirement might be higher. All of us at altitude might be at greater risk than someone living at sea level.
When do you make the decision to send someone to a lower elevation? How low?
If they are having trouble breathing in spite of being on 4 L of oxygen per minute. If they need more than that, we would send them to a lower elevation. Most people are fine going to Denver. By Georgetown (8530’/2600 m, a town between Summit County and Denver), they’ll experience an improvement. It’s above 2500 m where altitude issues become problematic.
Research in recent years, including our own, is revealing many other different variables that may affect an individual’s ability to acclimatize to high elevations, including different hormones, genetics, and muscle mass. We continue to advise anyone traveling to the Colorado mountain region above 7000′ from lower elevations to stay hydrated and well-rested, and time a slow ascent, planning to spend at least 24 hours in Denver, or another comparable lower elevation, before arriving at your final destination.
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.
“I’ve been here 25 years,” Sinclair shares with me over coffee at the Red Buffalo in Silverthorne, Colorado (9035’/2754 m). “Born and raised on the East Coast in Philadelphia.” The software company he had been working for moved him out to Colorado Springs. He hadn’t ever skied in his life until then. Shortly after, “on a whim”, he moved up to Summit County and started working on the mountain as what we used to call “Slope Watch”, the mountain staff often in yellow uniforms monitoring safe skiing and riding on the mountain. After a month, he got really bored, “and I said, ‘How do I get to be a patroller?'”
Sinclair then went to paramedic school to get qualified as an Emergency Medical Technician, then spent 19 years as an EMT and 9 years as a Medic. For the last six years, he’s worked for the ambulance service in Summit County, one of Colorado’s highest counties, with towns at above 9000′. He has also worked as a ski patroller at Copper Mountain, Keystone, and Park City (Utah). This year is the first he hasn’t been patrolling in 18 years. During the summer, he is a wildland fire medic, where he often works with crews that are shipped in from lower elevations, including sea level.
Although he’s decided to take this season off, he still maintains a very active relationship with the outdoors, travelling around the backcountry on expeditions to remote mountain cabins, and has made a recent trip to Taos, New Mexico (6969’/2124 m). He’s witnessed his share of altitude complications.
What are the most common altitude-related complications you see?
You see the families coming up to go skiing … Usually 90% of them are fine. Altitude doesn’t seem to bother them at all – they’re either healthy enough or lucky enough. They get in, they ski, they get out. But there’s that one family or that one couple that just don’t acclimatize. They don’t realize that they don’t acclimatize, and the rest of their group doesn’t realize. A couple of days go by and they think, ‘Geez, I feel awful,’ then they go ski, or do something active, and their condition is exacerbated. Or ‘Geez, I haven’t slept,’. you get that story over and over.
And you’re having this conversation on the hill as a patroller?
Or they’ve called 911 on their way [up to the mountains]. They have no idea. Just no idea. I ask them what they’d had to eat. They had a donut or a pastry or just coffee before the plane ride. I ask themwhen was the last time they peed. You’re trying to find the physiology of what’s happened.
I tell them, ‘You need to sit down or go back to your condo. You need liters of water. You need liters of Gatorade. No fried foods, no alcohol, no coffee. No marijuana. Let your body catch up. Wherever you’re staying, tell them you need a humidifier. Put it in every bedroom, crank it up and leave it on. You’re gonna have trouble sleeping.’
And they never wanna hear it. They never wanna take a day off, but by the time you see them, they’ve taken the day off anyway, because there’s no way they’re getting back up there!
Sinclair also expresses some frustration with the lack of resources provided by the ski industry itself:
How do you educate them? The marketing people don’t want to. Because if they have to spend a day in Denver [to acclimate], that’s one less day up here [at the ski resort]. They don’t want to publicize that [altitude sickness] can happen, that it’s common. People ask, ‘How often does this happen?’ Easily, at any resort in a day, Patrol probably sees 20 – 25 people, whether they called, they walked in, you skied by them and started talking to them. ‘You’re dehydrated. You’re at altitude. It means this …’ The resorts don’t want that many to know, otherwise, you’re gonna go to Utah or California, where it’s lower.
You get such misinformation. ‘At 5000 ft., you have 30% less oxygen.’ No, the partial pressure is less, there is still 21% O2 in the air. You just have to work harder to get the same volume. The real physiology of what’s going on is systemic. [People experiencing altitude sickness] don’t know why they feel like crap. They think it’s because they’ve been drinking too hard.
How do you mitigate their symptoms on the mountain?
We do a lot, but it’s reactive, not proactive. I hate to bash the oxygen canisters, but it’s not doing anything for you. It’s not gonna make you feel better, other than what you’re sucking up. At 10,000′, it’s questionable. We’ll be at the top of Copper [Mountain] giving them two to four liters of oxygen, then they’ll ski down and feel great.
Sinclair refers to the Summit County Stress Test, which was the first I’d heard of it:
You’re 55, you’re 40 – 50 lbs. overweight, and you come up for your daughter’s wedding. You walk over to Keystone [Ski Resort], you take the gondola over, then all of a sudden, you find out you have a heart condition. You find out whatever else you have going on. We’ve done it over and over and over. They go ski, they call us at 3 in the morning, we find out they’ve got a cardiac issue, or they’ve irritated the pulmonary embolism they’ve had for years.
I had a guy last year, at the Stube at Keystone for lunch.
Keystone’s Alpenglow Stube is a reputable restaurant that sits in the resort’s backcountry at 11,444′ (3488 m).
He had some food, alcohol, he’s having a great day. Ski patrol gets a call, ‘Hey, my husband doesn’t feel well.’ This guy looks bad, sitting on the couch, sweating profusely, and he can hardly tell what’s going on. It’s the classic presentation of an inferior heart attack.
‘I don’t have any heart conditions. I saw my cardiologist.’ You saw a cardiologist, but you don’t have any heart conditions?!
And there are a lot we don’t see. People who go home because they think they have the flu.
Have you seen any rare or surprising complications?
We see HAPE (High Altitude Pulmonary Edema) now and again. That seems to be a walk into the hospital where [their blood oxygen saturation is] at 50 – 52. We’re not in the zone to see HACE (High Altitude Cerebral Edema). We’re just not at the altitude.
HACE is more typical above more extreme elevations, above 11,000′. Colorado’s highest peaks are just above 14,000′. Most ski resorts in Colorado are below 12,000′.
I’ve only seen one HAPE case on the hill. In their 50s. You listen to their lungs, and they’re getting wonky. A guy who was reasonably fit, but you look at him and go, ‘Hm, this is bad.’ But he was responsive and talking. Then you start seeing the things like the swaying, getting focused on something else [in the distance]. One of those [situations] where you’re like, ‘Let’s get out of here.’ [We need] tons of oxygen. Again, ‘I didn’t feel good yesterday, but I decided to go skiing today.’ He was sitting at the restaurant at the top of Copper [Mountain].
People do not realize that their diabetes, their asthma, their high blood pressure, things that they commonly manage at home, are exacerbated at 9000′. By the time they realize it, they’re calling 911. At that point, your best bet is to get out of here.
What tools or instruments do you use the most as a paramedic and ski patroller?
Cardiac monitor. It’s got a pulse oximeter. [Also] simple things you ask. ‘Hey, do you know what your blood pressure is?’ I use a stethoscope all the time. Sight and sound. Are they talking to me? Are they having a conversation with me? Are they distracted by what’s happening to them? When was the last time they peed? Was it regular color? Did it smell stronger than usual?
People ask, ‘How much water do I need?’ How much water do you drink in a day? If I’m outside and I’m moving, I probably have 10 liters. If I’m on a roof laying shingles, I probably have 4 or 5 liters before lunch. It’s those little tools. You don’t even have to touch somebody.
Do you have any personal recommendations for facilitating acclimatization at altitude?
Workout, be in shape, go harder than you normally do that month before you get here. Get the cardiovascular system more efficient before you get here. If you have any kind of medical concerns, make an appointment with your doctor and say you’ll be at 10,000′ to sleep. Just ask, ‘What do I need to do?’ The day before you get on the plane, stop drinking coffee and start drinking water. Hydrate before you get here. They humidifier thing. Make sure the place you’re going has one. Find out. Go to Walmart and spend $15 to buy one.
Watch your diet. Just so your body’s not fighting to get rid of fat and crap.
When we’re getting ready for a hut trip, we are mostly vegetarian (although we do eat meat), but we ramp protein up a week prior, pushing more chicken, more red meat. We tend to eat fish normally, but there’s always at least one fish meal at the hut. We don’t do crappy food at the hut. I don’t care if I have to carry another 10 lbs. In addition to going to the gym, go for a skin, go to 11,000 – 12,000′ for a couple hours. Ramp up the altitude work.
What do you eat on the trail?
Pre-cooked sausage, usually some kind of chicken sausage. Cheese. Whole grain tortillas, and if we’re feeling spunky, some kind of hot sauce or pico [de gallo]. For me, it’s just a handful of nuts and raisins. If I feel like something else, I’ll throw in some chocolate or white chocolate. I hate the packaging, the processed foods, the bars. Somebody usually makes granola for on-the-way-out food. And I tend to carry dried fruits. Lots of peaches during Palisade peach season. I used to take a lot of jerky.
A recent topic that comes up alot in altitude research at our clinic is Aging.
I have to work harder to stay at the same place. I’m sitting here and I can feel my right knee. I was at a 15″ [of snow] day in Taos, and I caught something [skiing]. It’s been weeks, and it’s not weak or anything, but I just know. It takes longer. I find I need more sleep. I was a 4 or 5 hour a day guy for a long time. Now I’m at 7. The days I get 8 are awesome. Luckily enough, I’m still healthy, fit. If I’m up at night, it doesn’t shatter my day. Haven’t slept on oxygen yet. Don’t want to find out.
He laughs.
As I get older, I’m adding more supplements: fish oil, glucosamine, glutine (for eye health). My eyes are bad anyway, and I’m constantly standing outside against a big, white mirror (the snow). And I’m cautious of the bill of a hat vs. a full-on brim during the summer. Other than my face, everything’s covered during the winter. The color of the bill on your hat can be way more reflective. A black bill will cut the reflection. Little things.
I’ve rounded out my workouts. They’re more whole-body. I concentrate on cardio. I’m conscious that I’m not as flexible as I was. I’d like to say we’re regularly going to yoga, but at least we’re going.
The gauge for me is you go on a hut trip with our friends in the middle-age category, but we’ll take some younger folks [too]. I kinda monitor who’s doing what – chopping firewood, who’s sitting more than who. It’s not out of pride. I need to realize.
I’m colder. You start to notice. It’s not that your feet are cold, it’s that your calves are cold. I succumbed to boot heaters a few years ago.
Year after year, in every season, visitors from all over the state and all over the world come to Colorado’s high country. For many of them, it’s the highest elevation they’ve ever visited, and often ever will. The dryness, the elevation, the air pressure, the intense sun exposure and the lack of oxygen demand a lot of compensation from the body. Sinclair’s experiences at altitude are consistent across every conversation I’ve had with physicians, athletes and other professionals when it comes to preparing your body to be active at altitude, from getting plenty of water to controlling the speed of your ascent to any elevation above 7000′ to consulting with a specialist regarding any pre-existing cardiac or respiratory conditions to how much oxygen one needs to mitigate symptoms of altitude sickness to decreasing elevation in case of an emergency. Any one of these experts will also tell you that the best ways to prepare your body for altitude is to get plenty of sleep, exercise regularly, and limit foods containing a lot of oil, grease and fat that will demand more from your body.
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.
The population of Summit County, Colorado is projected to grow by 56% between 2010 and 2030. Along with adjacent Park and Lake Counties there are now over 40,000 people living above 2800 meters elevation. This is the largest high altitude population in North America. As opposed to native populations in South America, Africa and Asia who have been residing above 2800 m for centuries, the North American residents are acclimatized but not adapted. Symptoms related to hypobaric hypoxemia are notable above 2500 m. Recognized conditions associated with altitude include central sleep apnea leading to hypoxemia (abnormally low oxygen level in the blood) which activates the sympathetic nervous system. In susceptible persons this can cause systemic and pulmonary hypertension. The incidence of this potentially devastating side effect of mountain living is unknown. In order to better understand the potential side effects of nocturnal oxygen desaturation in healthy individuals, it is beneficial to investigate the normal physiological changes that occur during sleep, which leads to low oxygen levels in all individuals.
When the body enters the sleep state, many of the behavioral mechanisms that are active during wakefulness are blunted, and it’s been found that different sleep stages have varying effects as well. One of the major changes is a diminished response to hypercapnia (high carbon dioxide levels in the blood) and hypoxia. During sleep, the CO2 set point is elevated from 40 mmHg to 45 mmHg, which results in reduced alveolar ventilation. It’s also observed that minute ventilation is reduced, which is due to decreased tidal volumes that is normally compensated for with an increase in breathing frequency during wakefulness. Also, during sleep, there tends to be upper airway narrowing that is normal and there is reduced reflex muscle activation of the pharyngeal dilator muscle. All of the above factors contribute to decreased ventilation during sleep.
A lot of what is understood about the effects of nocturnal hypoxemia is due to extensive studies in individuals with underlying diseases, and these studies are not always conducted at higher altitudes. One such study investigated the effects of nocturnal desaturation (SaO2 < 90% occurring for > 30% of the sleep study) in chronic obstructive pulmonary disease (COPD) patients without a diagnosis of sleep apnea. The authors found higher rates of dyspnea, increasing rates of worsening COPD symptoms, poorer quality of sleep and health-related quality of life. Another such study found that some patients with COPD experience increased transient arterial hypoxemia (TAH) during rapid eye movement (REM) sleep. In this study, the authors observed that the study subjects experienced increased pulmonary vascular resistance (which can lead to pulmonary hypertension) and a few subjects experienced an increase in their cardiac output. The authors found that individuals could experience a decrease in this phenomena by using nighttime oxygen therapy.
Studies, such as above, do not assist in identifying healthy individuals that may need early intervention due to nocturnal hypoxemia at altitude. What about the healthy individuals without underlying diseases? In the study conducted by Gries and Brooks in 1996, the authors collected data from 350 patients. Their recorded average low saturation in the study of 350 subjects was a reported 90.4% lasting an average 2 seconds. This study was conducted at the Rainbow Babies and Children’s Hospital located in Cleveland Ohio, at an elevation of 653 feet (198 m). This is one of the largest studies done to assess normal oxygen levels observed during sleep, and the results, along with results from other studies are displayed in Table 1. As of right now, there is no equivolent study for subjects at elevations like that of Summit County, CO, which is at an average of 9110 feet (2777 m). Aside from the normal physiological changes noted above, the rates of developing underlying central sleep apnea leading to systemic and pulmonary hypertension is unknown. Further, there are no guidelines as to initiating treatment in patients that may be experiencing adverse effects of high altitude nocturnal hypoxemia, because there is a lack of data to establish baseline normal values observed at this elevation. This leads to unnecessary sleep studies, and further involvement of a myriad of healthcare professionals that have no specific guideline to reference when approached by one of these patients.
In order to further our understanding of the effects of high altitude and nocturnal hypoxemia in healthy individuals, like that of Summit County, there has to be preliminary and ongoing research in these individuals. Dr. Chris Ebert-Santos is currently conducting an overnight pulse oximetry study, which aims to recognize which symptoms they may or may not be experiencing, that are related to high altitude or sleep disorders, so that they may receive treatment, feel better, and remain active.
At this moment, initial study results reveal a decreased average low night oxygen saturation from that of the study conducted by Gries and Brooks. In a sample of just 14 individuals, the average low SpOs recorded overnight is at 81.3%, which is 9% lower than that recorded by Gries and Brooks (Graph 1). The study is also revealing a trend in lower night oxygen saturations in individuals that have lived at elevation for a longer period of time (Graph 2). These findings suggest the need to expand and build on the current study being conducted by Dr. Chris and her team at Ebert Family Clinic. If interested, you may apply in-person at Ebert Family Clinic, where you will be required to fill out a health questionnaire on your length of residence at altitude, medical history, and possible symptoms related to high altitude. Your basic vitals will be logged at the appointment. After the first study, you will then be rescheduled in 12 months for a follow-up overnight study to monitor for any changes. Overall, this study is designed to help with an understanding on the potential impact of high altitude on healthy individuals that are acclimated, but not necessarily adapted, to this environment.
Robert Clower is a second year physician assistant student at Red Rocks Community College in Arvada, CO. His undergraduate degree was in Biology, which incorporated both medical health science courses as well as independent research courses in general biology and ecology. While attending school at the University of North Georgia, Robert served in the Army National Guard for a cumulative time in service of 8 years. After completing his undergraduate degree, Robert gained medical experience as an operating room assistant, which included assisting support staff with surgical preparation and patient transport throughout the hospital for surgical appointments. Outside of his studies, Robert enjoys snowboarding, hiking, snowshoeing, exercising and spending time with family and friends.
Sources
Summit County Population Projections: Summit County, CO – Official Website. Summit County Population Projections | Summit County, CO – Official Website. http://www.co.summit.co.us/519/Population-Projections. Accessed March 3, 2020.
Tintinalli JE, Ma OJ, Yealy DM, et al. Tintinallis Emergency Medicine: a Comprehensive Study Guide. New York: McGraw Hill Education; 2020.
Gupta P, Chhabra S. Prevalence, predictors and impact of nocturnal hypoxemia in non-apnoeic patients with COPD. 52 Monitoring Airway Disease. 2015.
Lemos VA, Antunes HKM, Santos RVT, Lira FS, Tufik S, Mello MT. High altitude exposure impairs sleep patterns, mood, and cognitive functions. Psychophysiology. 2012; 49 (9): 1298-1306.
Cingi C, Erkan AN, Rettinger G. Ear, nose, and throat effects of high altitude. European Archives of Oto-Rhino-Laryngology. 2009; 267 (3): 467-471.
High elevation prompts physiologic changes in the body. As elevation increases, oxygen concentration in the air decreases; this is why some people suffer from altitude sickness when travelling to high altitude environments like Summit County, Colorado from a lower elevation. Training and/or living at elevation increases our red blood cell mass in order to compensate for the lower oxygen concentration, thus increasing our oxygen-carrying capacity. Red blood cells are like microscopic rafts that flow down the rivers of our blood vessels, picking up oxygen from our lungs when we breathe and then transporting it to all the muscles and organs that need it to function properly. For athletes, this physiologic concept can be used to their advantage in order to improve their performance. If they can train their blood cells to carry more oxygen by forcing them to grow in a more hypoxic (low-oxygen) environment, then they can have more oxygen available to their muscles to perform in any activity.
There is a modern training model that some athletes have adopted called “Live High, Train Low”. This means that the athlete performs high intensity training sessions at a lower elevation, but maintains general training and living at higher altitude. Your body begins making metabolic changes immediately when exposed to high altitude and hypoxia, but it can take a couple weeks for the maximum effect. Expert Dr. Gustavo Zubieta-Castillo, who spoke in La Paz, Bolivia at the 7th Annual Chronic Hypoxia Conference that Dr. Chris attended in 2019, claims that it takes him about 40 days to build up his hematocrit to be back to functional in La Paz which is situated at nearly 12,000 ft. All in all, the goal of living and/or training high, while including high intensity sessions at lower altitude, is to give your body enough time to build up some acclimatization to the hypoxic environment. Several studies in the last 25 years have taken various groups of athletes and placed them on different training regimens over 4 weeks. Some would live at low altitude and also train low, some trained low and lived high, and others trained high and low while living at high altitude. One study completed in 2008 concluded that athletes who either live high and train low, or live high while training low and high, showed about a 1.4% improvement in sea level endurance performance.
How high is too high, and how low is
too low?
Snowshoeing above 9000 ft., Summit County, Colorado.
It was found in this same study, that there is in fact a “sweet spot” for implementing the “Live High, Train Low” paradigm. If subjects were living lower than 1800 m, there was not a significant improvement in athletic performance. On the other hand, if subjects were living too high, they could not adequately recover from training and therefore did not show improvement because their bodies struggled to keep up with the hypoxic environment. The best elevation to live and/or train at in order to increase RBC (red blood cell) production, RBC mass, and oxygen-carrying capacity is between 2100 m-2800 m, or about 7000 ft-9000 ft.
What does this mean for athletes in Summit County who live high and train high?
Great news! There are still major benefits to those who live and train in Summit Country, as well as for people who visit the mountains and train while they are in town. This is because of a physiologic process called autophagy. Autophagy is described as our cells’ process of degrading old proteins and damaged cell parts. This is a normal process that modulates cell survival, is important for cell renewal, and is also a promoting factor of exercise performance from altitude training.
When exposed to a hypoxic environment, our cells produce adaptive responses that ramp up autophagy and cell renewal elements. These responses include factors that promote skeletal muscle growth, boost skeletal muscle capillary concentration, and enhance coronary arteries (the arteries that feed your heart). Living and training at altitude is good for your heart and it can help build muscle while decreasing body fat mass. It also shows significant increase in cardiac output and strength of your heart stroke.
However, excessive exercise and especially excessive exercise at altitude can prove harmful to our skeletal muscle. It has been observed in male subjects running 20 km that the excessive exercise induces autophagy too much which leads to degradation of muscle protein, damage, and eventual loss of skeletal muscle all together. Therefore, just as there is a sweet spot for altitude training, it is also a good idea to monitor training in order to maximize the benefits of training in a place like beautiful Summit County.
So, how should I be training if I live in Summit County or if I am visiting for some time?
I had the pleasure of speaking with Mary Scheifley about this particular strategy. Mary is the owner of Peak One Fitness, a 24-hour gym in Frisco, Colorado (9000 ft.). She has over 20 years of experience in fitness and athletic training. She competed semi-professionally in mountain bike racing, and continues to bike today as well as cross-country ski, snowboard, weightlift, hike, and anything else that keeps her active. She loves Frisco and has found that being outside and active is almost spiritual. She is passionate about fitness and nutrition, and she works extremely hard to tailor her training regimens to each of her clients based on their individual needs or goals.
Cardio machines at Peak One Fitness, Frisco, Summit County, Colorado
When she trained people in Denver, she typically was running high-intensity aerobic classes. However, here in Frisco, she prefers to focus on strength and only include high-intensity interval training (HIIT) in short spurts. She believes that you don’t need to be over-exerting your body to see a positive response. She has a client who lives near sea level for most of the year where her main training regimen includes Cross Fit. When she comes to Frisco though, she can see a significant decrease in BMI and body fat index in just two months of lower-intensity training. Though frustrated that she cannot run on the treadmill as fast or as long as she can at home, by the end of her stay in Frisco, this client understands that difference of the elevation and appreciates the process that Mary provides for her.
Mary recognizes that fitness is not “one size fits all”. She typically likes to start people out at 80% of their maximum heart rate when exercising, but there are factors that may change this. Her clients that live in Summit County have already been acclimatized to the elevation so she can add a little to their 80% max heart rate because for them, 80% may feel like 70%. On the flip side, if you are visiting from sea level, she may have to decrease your 80% of maximum because of the hypoxia at elevation. Other factors that play a role in how Mary develops her training regimens include age, the client’s goals, their previous fitness level, and their overall reaction to altitude.
I also asked Mary about her experience with competition and professional athletes. Personally, she could tell that her endurance was superior to her competition when she raced at altitude against bikers from Denver. She also noticed that when she was in Denver, the racers there were stronger and bulkier than her. She also has experience training athletes who are preparing for competitions such as the Leadville 100 or who are professional skiers who tell her that it is more beneficial for them to come to altitude about 3 weeks prior to competition in order to prepare rather than just training at lower altitude. This is because their body will better adapt if they give it a little more time before competition while training.
At the end of the day, whether you are training for a competition, or just trying to stay healthy, being at altitude can pose challenges as well as benefits to our bodies. The following are some tips from Mary on maximizing your workouts at altitude without compromising your health and wellness.
Mary’s tips for athletic training and exercising at high altitude:
Increase water intake, even before you come to
elevation. You should be drinking at least 3-4 liters of water per day.
Increase caloric intake. At altitude you are burning
more calories than at sea level, and if you are wanting to train you need to
fuel your body appropriately. Especially increase protein intake.
No alcohol. If you enjoy one drink here and there you
should be fine, but if you are wanting to train at a high level alcohol should
not be on the menu.
Add electrolytes. In addition to increasing water, you
need to make sure you are replenishing your body with the salts it requires.
Take it slow. Maybe start with some yoga or moderate
stretching before moving into running or HIIT classes. You may need to decrease
your level of training by 20%.
Consider spending a night in Denver before heading up
the mountain to Summit County. Dr. Chris has expressed this frequently to
travelers and visitors of Frisco; it gives your body a chance to acclimatize
prior to ascending to 9,000+ feet.
Don’t expect to be at your “home” level of endurance
or fitness. Do not get discouraged if you cannot run your typical 7-minute
mile, or you can’t easily warm up with a set of 10-15 squats. Your body needs
to adjust, and you may need to just take it easy in the altitude. Ultimately,
have fun and enjoy the beautiful outdoors!
Sarah Brzecezk is a 2nd year Physician Assistant student attending Midwestern University in Glendale, Arizona. She graduated from Northern Arizona University in Flagstaff, AZ with a Bachelor’s in Biomedical Sciences and then worked as a medical assistant in Internal Medicine prior to starting PA School. She is passionate about healthy eating and maintaining a physically active lifestyle, and she hopes to specialize in Orthopedics when she graduates this Fall. During her 6 weeks at elevation in Frisco, Colorado, she has enjoyed numerous hikes, two hut trips, yoga classes, and running in the gorgeous outdoors. Her goal as a provider is to help others overcome injury and illness in order to return to physical activity and athletics, enabling them to combat chronic illness and stay healthy for their future years.
References
Zhang, Y., & Chen, N. (2018). Autophagy Is a Promoter for Aerobic Exercise Performance during High Altitude Training. Oxidative medicine and cellular longevity, 2018, 3617508. doi:10.1155/2018/3617508
Brocherie, F., Millet, G. P., Hauser, A., Steiner, T., Rysman, J.,
Wehrlin, J. P. & Girard, O. (2015). “Live High–Train Low and High” Hypoxic
Training Improves Team-Sport Performance. Medicine & Science in Sports
& Exercise, 47(10), 2140–2149. doi: 10.1249/MSS.0000000000000630.
Stray‐Gundersen,
J. and Levine, B.D. (2008), Live high, train low at natural altitude. Scandinavian
Journal of Medicine & Science in Sports, 18: 21-28. doi:10.1111/j.1600-0838.2008.00829.x
