Category Archives: Medicine

Follow Dr. Chris around the world for insight from a physician’s perspective

Altitude Science, Health, High Altitude, Medicine, Surgery

Thin Air, Thick Blood: Increased Risk for Blood Clots After Surgery at Elevations Above 4000 Feet 

Leave a comment

by Colby Baron, PA-S

Moving to higher elevation often has side effects on the body. To many people, these effects are well managed. They may feel a slight shortness of breath while exercising, an occasional headache relieved by a caffeinated drink, or some dry skin. Others are less fortunate. Their symptoms impact their daily lives. Regardless of how visible one’s symptoms may be, every human body must make physiologic internal changes to adapt to living at higher altitudes.  

The body needs oxygen. While air still contains 21% oxygen in a high altitude environment, the density of the molecules is lower. When you arrive at a mountain town like Frisco, in the Rocky Mountains of Colorado with an elevation of 9,000 feet, the body works to pull whatever oxygen it can find into its system. It not only has to breathe harder to do so but creates more red blood cells so that it can be more efficient in transporting more oxygen to all tissues. While this adjustment works, it has its side effects:  more red blood cell vehicles means more traffic along the blood vessel highways. Such blockage makes the blood more viscous and more prone to forming clots. This is not a a “death trap” for all but can have greater consequences for those already at risk of having a serious clotting event. 

Surgery requires patients to remain immobile in recovery and often involves vascular injuries as the tissue is altered. Blood clots can form in these circumstances. This is managed with anti-platelet and anticoagulation drugs. Orthopedic procedures tend to present with the biggest risk. This is especially true when operating on the knee.  Operations closer to the heart have less risk. Arthroscopic rotator cuff procedures typically only have about a 0.3-0.5% chance of causing any thrombotic issues.  The stakes are altered significantly when altitude is factored into the equation. In a recent study in the Journal of Shoulder and Elbow Surgery published by orthopedic surgeons Matthew Cannefax, Michael T. Burrus, David R. Diduch, and Brian C. Werner, arthroscopic rotator cuff repairs done at elevations above 4,000 feet increased the rate of blood clots by 2 – 3 times as much.   Deep vein thromboses, pulmonary embolisms, and other thrombotic complications lead to improved monitoring and follow up with patients post op.  

My own shoulder surgery was at a lower elevation, requiring  strict immobilization of my arm in a sling for 6 weeks straight, even while asleep. Even if I had wanted to remove my sling, my arm felt weak with significant pain every time I stretched my limits even accidentally. The constant restricted position I was forced to be in rarely felt comfortable. Adding the pain and systemic consequences of a blood clot would have emphasized those hardships even more. Frisco pediatrician Dr. Christine Ebert-Santos had shoulder surgery at 9,000 feet with immediate relief of the constant pain she suffered for 9 months and a rapid uncomplicated recovery. The advantages of receiving care in our home community outweighs the very small risk of increased complications from altitude for most mountain residents. 

References

  1. Journal of Shoulder and Elbow Surgery, Cannefax M, Burrus MT, Diduch DR, Werner BC. Increased risk of venous thromboembolism following arthroscopic rotator cuff repair at high altitude. J Shoulder Elbow Surg. 2017;26(7):e207-e213. doi:10.1016/j.jse.2017.03.012  
  1. American Academy of Orthopaedic Surgeons. Venous thromboembolism in orthopedic surgery. Accessed March 27, 2026. https://www.aaos.org  
  1. Journal of Thrombosis and Haemostasis, Imray C, Booth A, Wright A, Bradwell AR. Thrombosis and coagulation at high altitude. J Thromb Haemost. 2010;8(3):499-504. doi:10.1111/j.1538-7836.2009.03700.

Colby Baron is physician assistant student at Rocky Mountain University in Provo, Utah. Ever since having lifesaving brain surgery when he was 15 years old to repair an idiopathic hemorrhagic stroke, Colby has tried to give back to the medical community any way that he can. As an active individual who loves soccer, board sports, skydiving, hiking, camping, and anything one can do outdoors, he lives an active lifestyle. Such a life has created many great memories but has also been the cause of several orthopedic injuries. He has had a broken leg, a dislocated kneecap, a torn meniscus, a torn labrum, and multiple concussions and sprained ankles. After graduating PA school, he hopes to use these past experiences and time spent in the OR assisting orthopedic surgeons with traumatic and pediatric cases to help others emphatically with their musculoskeletal issues. He feels great passion for this and hopes to positively impact patients and providers throughout his career.  

Acclimation, Altitude Science, Athletic Training, Exposure, Health, High Altitude, High Altitude Training & Fitness, Hyperbaric Therapy, Medicine, Mountaineering

Pressure as Prevention: Can Hyperbaric Oxygen Help You Beat Altitude?

Leave a comment

Pictured above is the highest hyperbaric chamber in the world at the Bolivian Naval Station at Lake Titicaca.

If you’ve ever climbed high enough to feel short of breath, dizzy, or just “off,” you’ve likely experienced the effects of high altitude on the human body. Once you get above about 2,500 meters (8,200 feet), the air gets “thinner”—not because oxygen disappears, but because there’s less pressure pushing oxygen into your body. This particular problem is termed hypobaric hypoxia, and it can turn a beautiful mountain adventure into a medical problem quickly.

Why Altitude Hits So Hard

At elevation, your body is forced to adapt fast—and sometimes it isn’t able to keep up. That’s when altitude illness can develop, ranging from mild to life-threatening ailments:

  • Acute Mountain Sickness (AMS): headache, nausea, fatigue
  • High-Altitude Pulmonary Edema (HAPE): fluid in the lungs, causing shortness of breath
  • High-Altitude Cerebral Edema (HACE): brain swelling, confusion, and potentially coma

These aren’t separate diseases so much as a continuum of worsening hypoxia. Most severe cases can start as mild symptoms and can later progress to more severe presentations. The quicker you can recognize the more subtle symptoms, the better you may be in avoding severe illness. 

What’s Happening Inside the Body?

When oxygen levels drop, the body goes into survival mode:

  • Blood vessels in the lungs constrict → raising pressure (risk of HAPE)
  • Blood vessels in the brain become leaky → swelling (risk of HACE)
  • Inflammatory and hormonal systems ramp up → causing AMS symptoms

In short: your body is trying to compensate in response to the change in environment, but sometimes those compensations backfire.

Enter Hyperbaric Oxygen Therapy (HBOT)…

Now imagine flipping the script. Instead of struggling in thin air, what if you could flood your body with oxygen under pressure? That’s exactly what Hyperbaric Oxygen Therapy (HBOT) does. Inside a pressurized chamber, you breathe 100% oxygen, dramatically increasing how much oxygen dissolves into your blood. In a way you have artificially placed yourself in a lower altitude. 

How HBOT Helps at Altitude

HBOT essentially acts like a “simulated descent”—one of the most important treatments for altitude illness.

It can:

  • Boost oxygen levels in your blood and tissues
  • Improve brain function in hypoxic states
  • Reduce inflammation and oxidative stress
  • Potentially stabilize the blood–brain barrier

In wilderness medicine and EMS settings, portable hyperbaric chambers are already used when immediate descent isn’t possible. They can be lifesaving.

But there’s a catch: The benefits are temporary. Once the pressure is removed, symptoms can return if the person is still at altitude where their symptoms first started.

A New Idea: Can HBOT Be Used Before You Climb?

Here’s where things get interesting. Researchers are now exploring whether HBOT could be used not just as treatment—but as preparation.

The concept: preconditioning

The idea is that repeated exposure to hyperbaric oxygen before ascent might “train” the body to handle low-oxygen environments better—similar to acclimatization.

Potential effects include:

  • Activation of hypoxia-response pathways (like HIF)
  • Improved mitochondrial efficiency (better energy use)
  • Increased antioxidant defenses
  • Enhanced microcirculation

In theory, this could mean: fewer symptoms, better performance, and lower risk of severe altitude illness

What Does the Evidence Say?

Early research is promising, but not definitive.

Some studies suggest:

  • Reduced incidence and severity of AMS
  • Better oxygen saturation at altitude
  • Possible protection against brain and lung edema

But there are still big unknowns:

  • What pressure and duration work best?
  • How long before ascent should HBOT be done?
  • Who benefits most—athletes, mountaineers, or everyone?

For now, HBOT preconditioning is an exciting idea—not standard practice.

What About Athletes and High Performers?

Altitude is a major challenge for:

  • Endurance athletes
  • Military personnel
  • Search and rescue teams
  • Mountaineers

Performance drops quickly due to:

  • Lower VO₂ max
  • Faster fatigue
  • Impaired decision-making

HBOT might help by:

  • Improving oxygen efficiency
  • Preserving cognitive function
  • Delaying fatigue

But again—this is still being studied, and access to HBOT can be limited and expensive.

How Does HBOT Compare to Proven Strategies?

Right now, the gold standard hasn’t changed:

  • Gradual ascent → still the most effective prevention
  • Acetazolamide → helps your body acclimate faster
  • Dexamethasone → used in higher-risk situations

HBOT (for prevention) is still catching up in terms of evidence.

Is HBOT Risk-Free?

Not entirely. While generally safe, it can cause: ear or lung barotrauma (due to pressure-related injury), oxygen toxicity (rare but serious), and can lead to increased oxidative stress with overuse. These risks matter more when using HBOT proactively rather than as a rescue therapy.

Where This Is Headed

HBOT sits at a fascinating intersection of performance, medicine, and physiology.

Future research is looking to focus on finding optimal preconditioning protocols like treatment duration and number of set times. Some other areas also include identifying which patient populations would benefit most from this form of treatment and combining HBOT with other strategies like hypoxic training.

Bottom Line…

Hyperbaric oxygen therapy is already a powerful tool for treating severe altitude illness, especially when descent from altitude isn’t immediately possible.

As a preventive strategy, it shows real promise, but it’s not ready to replace the fundamentals.

For now, your best defense at altitude is still:

  • Climb gradually
  • Know the symptoms and have a buddy!
  • Use proven medications when appropriate (like Acetazolamide)

HBOT may one day become part of the toolkit—but for now, it’s a high-potential frontier, not a first-line solution.

References 

Centers for Disease Control and Prevention. (2023). High-altitude travel and altitude illness. https://www.cdc.gov/travel/page/high-altitude-travel

National Center for Biotechnology Information. (2023). High-altitude illness. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK430716/

National Center for Biotechnology Information. (2023). Hyperbaric oxygen therapy. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK459172/

PubMed Central. (2020). Hyperbaric oxygen therapy: Mechanisms and clinical applications. https://www.ncbi.nlm.nih.gov/pmc/articles/PMCPubMed Central. (2018). Pathophysiology, prevention, and treatment of high-altitude illness. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC

Wilderness Medical Society. (2019). Wilderness Medical Society clinical practice guidelines for the prevention and treatment of acute altitude illness. Wilderness & Environmental Medicine, 30(4), S3–S18. https://doi.org/10.1016/j.wem.2019.04.006

Hackett, Peter H., & Roach, Robert C.. (2001). High-altitude illness. New England Journal of Medicine, 345(2), 107–114. https://doi.org/10.1056/NEJM200107123450206

Bärtsch, Peter, & Swenson, Erik R.. (2013). Acute high-altitude illnesses. New England Journal of Medicine, 368(24), 2294–2302. https://doi.org/10.1056/NEJMra1214870

Moon, Richard E.. (2019). Hyperbaric oxygen therapy indications. Undersea & Hyperbaric Medicine, 46(3), 425–430.

Milledge, James S., West, John B., & Schoene, Robert B.. (2013). High altitude medicine and physiology (5th ed.). CRC Press.

Dylan Raulie was born and raised in Colorado Springs, Colorado and went out of state for his undergraduate years at Creighton University in Omaha, Nebraska, trading mountains for cornfields and altitude for attitude … from the wind. He got a Bachelor’s of Science in Emergency Medical Services majoring in sirens, stress, and 2 a.m. calls. After studying and learning about what could go wrong with future patients, he would often times avoid trying to become one on his interscholastic rugby team. He worked as a 911 paramedic in Colorado Springs. Between brutal call volumes, lack of sufficient ambulances on the streets, and extreme variety in patient presentations, no day was the same.  He later earned his Master’s in Biomedical Sciences at Rocky Vista University where he developed into being a better student and lifelong learner, which directly influenced his approach as a medical student. On his days off, he is a part-time grappler (in BJJ), but a full-time adventurer, always in motion—physically and mentally.

High Altitude, Medicine

Trauma Related High-Altitude Pulmonary Edema

Leave a comment

HAPE Poster

This poster was presented at the American Thoracic Society International Conference in San Diego in May of 2018.  As yet unrecognized and unpublished, Trauma HAPE joins other presentations that have been suggested by altitude providers but have not been studied yet including Highlander HAPE, Post Anesthesia HAPE and Reverse HAPE,  where life threatening hypoxia develops after return from altitude.   The blog highaltitudehealth.com functions to raise awareness among other healthcare providers practicing at any altitude about the potential health complications associated with rapid changes in elevation.

Acclimation, Altitude Science, Anesthesia, Health, High Altitude, Medicine, Technology

Anesthesia and Altitude

Leave a comment

by Megan Wilson, NP-S

One of the last things anybody wants to go through is a surgical procedure, especially if you happen to be in the mountains on vacation. Unfortunately, life happens, and whether you’re a visitor to high-altitude or a permanent resident, there is a chance you may need surgical care. 

Anesthesia is a requirement for surgical procedures and there are varying levels of anesthetic available. General anesthesia, often referred to as “going off to sleep”, is where you are completely unconscious and anesthetic gases and medications keep you sedated while a machine breathes for you during your procedure. Monitored anesthesia care (MAC), also known as conscious sedation, is when the anesthesiologist keeps you comfortable with meds, but you are still able to breathe on your own. Medications given for surgery affect your ability to breathe, which is why your vital signs (oxygen levels, blood pressure, heart rate) are monitored through a machine by a doctor. 

How is this different at high altitude?

When you head to higher elevations, barometric pressure decreases and causes partial pressure of oxygen to decrease – this makes oxygen harder to effectively get into your lungs and causes hypoxemia/low oxygen levels (Leissner & Mahmood, 2009). This leads to a condition commonly known as altitude sickness, causing headaches and trouble breathing, and in more serious cases, it can also lead to high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Much like oxygen, anesthetic gases are also affected by barometric pressures, impacting the effectiveness of inhaled anesthetics (Bebic et al., 2021). Additionally, equipment is affected by high altitude – meters on anesthesia machines that monitor gas/oxygen levels tend to under-read at higher elevations (Bebic et al., 2021; Leissner & Mahmood, 2009). Pulse oximetry, which measures your overall oxygen saturation (the percentage of oxygen in your blood) also has limited accuracy at high altitude (Bebic et al., 2021). Providers who practice at higher elevations should be aware of these nuances and treat accordingly. The most important treatment we have to help with the effects of partial pressure at high altitude is supplemental oxygen (Leissner & Mahmood, 2009).  

Unfortunately, there is limited research on the effects of high altitude and anesthesia, and even less on the effects of anesthetic drugs at high altitude vs. sea level (Bebic et al., 2021). With current published data, it is clear that surgical risks increase with elevation. Whether it’s the potential for equipment to malfunction, or novice providers new to high-altitude unaware of the subtleties in treatment, it is critical to be mindful of compromised respiratory status at elevation when considering which anesthetic agents to use for surgery. 

References

Bebic, Z., Brooks Peterson, M., & Polaner, D. M. (2021). Respiratory physiology at high altitude and considerations for pediatric patients. Pediatric Anesthesia, 32(2), 118-125.

https://doi.org/10.1111/pan.14380

Leissner, K. B., & Mahmood, F. U. (2009). Physiology and pathophysiology at high altitude:

Considerations for the anesthesiologist. Journal of Anesthesia, 23(4), 543-553.

https://doi.org/10.1007/s00540-009-0787-7

Altitude Science, Health, Hyperbaric Therapy, Medicine

WHEN OXYGEN IS TOXIC

2 Comments

Why Too Much Oxygen Can Be Deadly: The Hidden Molecular Consequences of Hyperoxia

by Nic Rolph, PA-S

Oxygen keeps us alive—but in excess, it can quietly unravel critical cellular functions. A groundbreaking study by Baik et al. (2023) in Molecular Cell shines a light on why hyperoxia (too much oxygen) is toxic, and reveals a hidden mechanism behind its damaging effects.

The Mystery of Oxygen Toxicity

We’ve long known that both oxygen deprivation (hypoxia) and oxygen overload (hyperoxia) are harmful. While hypoxia research has led to major discoveries like the Nobel Prize-winning work on HIF (Hypoxia-Inducible Factors), hyperoxia has remained less understood—until now.

Baik and colleagues tackled a fundamental biological question: Why is oxygen toxic at the molecular level?

The Culprit: Fragile Iron-Sulfur Proteins

Using a combination of genome-wide CRISPR screening, proteomics, and in vivo experiments, the researchers identified a specific class of proteins highly vulnerable to excess oxygen: iron-sulfur cluster (Fe-S)-containing proteins.

These clusters act like tiny biochemical power stations inside proteins, but they’re extremely sensitive to oxidation. Under hyperoxic conditions, certain Fe-S proteins degrade, compromising several key cellular pathways:

  • Diphthamide synthesis – crucial for accurate protein translation.
  • De novo purine biosynthesis – needed for DNA and RNA building blocks.
  • Nucleotide excision repair (NER) – repairs damaged DNA.
  • Mitochondrial electron transport chain (ETC) – essential for energy production.

A Vicious Cycle of Oxygen Damage

Perhaps the most striking discovery was the feedback loop of cellular damage:

  1. Hyperoxia damages the ETC, lowering oxygen consumption;
  2. this increases local tissue oxygen levels even more,
  3. which leads to more damage—a self-amplifying loop Baik et al. called “cyclic oxygen toxicity.”

This cycle can explain why supplemental oxygen—while lifesaving—is also associated with complications in neonatal care, ICU patients, and chronic diseases.

From Petri Dishes to Lungs

The team validated their findings in human cells, mice, and even primary lung tissue. In a mouse model of hyperoxic lung injury, the same Fe-S proteins degraded rapidly—especially those in the ETC. Mice with preexisting ETC defects (like the Ndufs4 KO model) showed extreme sensitivity, confirming the ETC as the “weakest link” in the oxygen toxicity chain.

Bigger Picture: Aging, Disease, and Therapy

This study suggests that hyperoxia might contribute to a wide range of diseases—from premature infant lung injury and ischemia-reperfusion damage to neurodegenerative and mitochondrial disorders. It also offers a potential explanation for why antioxidant therapies have largely failed: superoxide isn’t the only villain—molecular oxygen itself may be enough to destabilize these proteins.

Rethinking Oxygen Therapy

Given these findings, clinicians may need to rethink how we use oxygen in medical settings. Rather than focusing solely on delivering “more oxygen,” we might need to tailor therapy to a patient’s oxygen-processing capacity—especially in those with mitochondrial or genetic vulnerabilities.

What’s Next?

Future research may explore:

  • Therapeutic hypoxia to interrupt the damage cycle.
  • Genetic screening to identify patients vulnerable to oxygen toxicity.
  • New drugs to stabilize Fe-S proteins in oxidative environments.

Takeaway

Oxygen is life-sustaining—but Baik et al. reveal it’s also a molecular saboteur under the wrong conditions. This landmark study not only explains the elusive biology of oxygen toxicity but opens new doors for safer therapies and deeper understanding of metabolic diseases.

Note from Dr. Christine Ebert-Santos, MD, MPS of Ebert Family Clinic in the Colorado Rocky Mountains at 9000’/2743m: newborns, children with respiratory infections or high altitude pulmonary edema, and people with sleep apnea are advised to use oxygen at high altitude. The level of oxygen saturation achieved with this treatment is well below normal sea-level values, so unlikely to cause any negative effects.

Altitude Science, COVID-19, Doc Talk, Health, High Altitude, Medicine, Pandemic

COVID-19 and Altitude: A discussion about the research with Dr. Isain Zapata

Leave a comment

Early in the pandemic, researchers were eager to learn more about the COVID-19 virus and how it takes shape in different communities. One area of particular interest for some of those researchers was the relationship between COVID-19 and high altitude, as altitude has been shown to impact other chronic diseases like COPD1, lung cancer2, and cardiovascular disease3. However, many of the early studies that were conducted resulted in nonspecific findings or trends in data that could be better explained by different variables than solely altitude. 

For example, one of the preliminary studies conducted in Colombia analyzed positive cases, deaths, and case fatality rates in 70 different municipalities ranging from 1 to 3180m above sea level. What these researchers found was that there was a negative correlation between altitude and COVID-19 case fatality rates4, meaning there were less COVID-19 deaths at higher altitude when compared to those at low altitude. One thing that is mentioned by the researchers is that population density plays an important role in the transmission of this virus4. The researchers concluded that this negative correlation seen between altitude and COVID-19 fatalities could be better explained by the differences in population in the varying locations4. 

Another early study conducted in 2020 looked at around 4 months of data in the U.S and around 2 months of data in Mexico and found that U.S. communities living at >2000m elevation had higher mortality rates than those at <1500m5. In Mexico, individuals <65 years old, the risk of death due to COVID-19 was 36% for those living at >2000m when compared to those living at <1500m5.

We discussed some of these findings with Dr. Isain Zapata, who is one of the authors of the article “Revisiting the COVID-19 fatality rate and altitude associated through a comprehensive analysis”. Which was a study conducted by a group of researchers at Rocky Vista University that further investigated the relationship between altitude and COVID-19 fatalities. Dr. Zapata said that some of their motivation to look further into this relationship was due to the lack of consistency in the conclusions formed by many of the studies conducted early in the pandemic. He hypothesized that there could be a few reasons for these inconsistencies, one being that there is a large discrepancy over what level of elevation is considered “high altitude” and another being that many of the studies published early on were specific to a certain location. Lastly, these studies were solely looking at data from the first few months of the pandemic, when COVID-19 infections were just beginning to take form. 

In their study, this group of researchers looked at COVID-19 fatality data from March 2020 to March 2021 in the mountain region of the western United States, including Montana, Idaho, Wyoming, Nevada, Utah, Colorado, Arizona, and New Mexico. Within each state, they looked at the data specific to each county and then subdivided them into census blocks6. Then determined the weighted average of the block’s altitude and adjusted for population density6. 

They found that in Colorado, Idaho, and Wyoming, communities living at higher altitude had lower COVID-19 fatality rates6. This trend was also observed when they performed a meta-analysis of all of the data from the U.S. Mountain region6. However, when looking at Arizona, Montana, Nevada, and Utah individually, there was not a significant relationship observed between high altitude and COVID-19 mortality6. One of the points discussed by the researchers is that in these states, the discrepancy may be based on the population density6. In Arizona and Nevada, the majority of the population in that state live at lower altitudes6. The researchers also discuss that the size of the state and the number of counties in each state may also play a role in these trends6. 

They also found that in Arizona, Colorado, Idaho, and Wyoming, areas with higher median incomes were associated with lower COVID-19 fatality rates6. 

The researchers observed that in New Mexico, there was a reverse altitude effect, in which, there was higher mortality rates at higher altitudes6. There was also a higher associated risk across the whole mountain region for the Native American population6. One observation that was pointed out in the discussion section of this article, is that New Mexico has one of the highest Native American populations6. In addition, Native Americans have been shown to have higher incidence of developing chronic diseases that are associated with worse COVID-19 fatality rates6. 

So, what does this all of this mean? Overall, in the U.S. western Mountain region, there were fewer Covid-19 deaths for communities living at higher altitude when compared to those living at lower altitude6. This same trend was observed when just looking at the data for Colorado6. 

Another point that was discussed by the researchers is that these implications can likely be explained by both protective physiologic changes that occur at altitude as well as demographic trends6. The demographic trend may be hypothesized to be a result of people who choose to live in areas of higher altitude as they are often seeking more active lifestyles. The results of this study leave room for more research to be conducted on how our bodies physiology changes in order to adapt to life at higher altitudes.  

  1. Andreas Horner et al., “Altitude and COPD Prevalence: Analysis of the Prepocol-Platino-Bold-Epi-Scan Study,” Respiratory Research 18, no. 1 (August 23, 2017), https://doi.org/10.1186/s12931-017-0643-5.
  2. Kamen P. Simeonov and Daniel S. Himmelstein, Lung Cancer Incidence Decreases with Elevation: Evidence for Oxygen as an Inhaled Carcinogen, November 12, 2014, https://doi.org/10.7287/peerj.preprints.587v2.
  3. Martin Burtscher, “Effects of Living at Higher Altitudes on Mortality: A Narrative Review,” Aging and Disease, 2014, https://doi.org/10.14336/ad.2014.0500274.
  4. Eder Cano-Pérez et al., “Negative Correlation between Altitude and Covid-19 Pandemic in Colombia: A Preliminary Report,” The American Journal of Tropical Medicine and Hygiene 103, no. 6 (December 2, 2020): 2347–49, https://doi.org/10.4269/ajtmh.20-1027.
  5. Orison O. Woolcott and Richard N. Bergman, “Mortality Attributed to Covid-19 in High-Altitude Populations,” High Altitude Medicine &amp; Biology 21, no. 4 (December 1, 2020): 409–16, https://doi.org/10.1089/ham.2020.0098.
  6. Carson Bridgman et al., “Revisiting the Covid-19 Fatality Rate and Altitude Association through a Comprehensive Analysis,” Scientific Reports 12, no. 1 (October 27, 2022), https://doi.org/10.1038/s41598-022-21787-z. 
Acclimation, Acetazolamide, Altitude Science, Child Growth & Development, Diamox, Doc Talk, Health, High Altitude, Medicine, Sleep at Altitude

Sharing at the Chateau: 23rd International Hypoxia Symposium in Lake Louise

Leave a comment

I attended the 23rd International Hypoxia Symposium in Lake Louise, Canada to present some of the research on altitude I’ve been conducting in Colorado. The conference has been going on since 1979, and for the past 26  years the organizers have been Robert Roach and Peter Hackett, world-renowned medical researchers from Colorado. Meeting most of the famous altitude researchers from all over the world was an inspiration.  Personal talks and sharing information were equally important to imbibing the latest knowledge about hypoxia and hemoglobin.

A slide is projected onto a screen over the heads of conference participant, depicting statistics showing infant birthweight in mammals decreasing over increasing elevations.
From Jay Storz’s presentation at the 2025 International Hypoxia Symposia in Lake Louise, Canada

Antarctic Icefish: Life Without Hemoglobin, was presented by Kristen O’Brien, expanding the concept of oxygen distribution in living beings and introducing us to varieties of fish we have never heard of. Her talk was followed by our “Mice and Men” guy, Jay Storz (and colleague Graham Scott), who along with Jon Velotta mentioned in our blogpost on the show “This Podcast Will Kill You” collect the large eared deer mice from peaks such as Blue Sky Mountain to study adaptation to hypoxia in their labs. The talk recognized for first prize was on Altitude Headaches, including a discussion of migraines, by Andrew Charles.

Every evening there was a banquet and speaker.  Astronaut Jessica Meir spent 210 days aboard the space station.  She shared a wide range of challenges such as exercising without gravity, choosing a compatible crew, getting boxes of treats from home, and effects of prolonged weightlessness on your eyes and muscles.

A slide projected onto a conference room screen before participants depicts results for six minute walks on and off oxygen.
Silvia Ulrich presented on Pulmonary Circulation of Central Asian Highlanders at the 2025 International Hypoxia Symposium at Lake Louise, Canada.

The research I would like to see duplicated in Summit County was from Kyrgyzstan, where Silvia Ulrich studied the hearts and lungs of the permanent residents at 9000 feet using the six minute walk as one of her tools.  They did not score higher when studied at sea level! She ran tests for pulmonary hypertension, which could be important here.

Of course, there was a talk on Sleep Disordered Breathing (sleep apnea) by Esther Schwarz, something we pay a great deal of attention to in our own clinic in Frisco, Colorado and have several research projects on the improvement we see with supplemental oxygen. The role of mitochondria in cellular function in hypoxia was presented by Dr. Christian Arias-Reyes, a researcher at Seattle Children’s Hospital who is originally from La Páz, Bolivia.  I met him at the Chronic Hypoxia conference in 2019 when he was a graduate student in Quebec and again in La Páz at this year’s conference. 

A line of people pose in front of a cafe with signs and plants hanging above a stone-tiled street lined with buildings
Altitude experts Dr. Zubieta Calleja, Dr. Christian Arias-Reyes, Dr. Michele Samaja and Dr. Christine Ebert-Santos with colleagues of the Hypoxia Symposia in front of a pizzeria in Coroico, Bolivia.

A deep dive into how our neurons react to hypoxia in the brain by releasing nitric oxide to dilate blood vessels and preserve circulation reenforced the counseling I do here in my clinic to parents whose children have breath holding spells or babies with dips in their oxygen on home monitors. Along with all the millions of children and adults living at 12,000 feet in Bolivia, we can witness that hypoxia does not cause brain damage. (Not to be confused with anoxia, a complete lack of oxygen.)

Lastly, Nobel prize winner and fellow pediatrician Gregg Semenza spoke on research to find a blocking compound against HIF- hypoxia inducible factor, as a cure for some cancers. Gregg’s work was described in our blog on the Nobel prize being awarded to scientists working on hypoxia. HIF deserves its own blogpost! More about cancer and hypoxia at altitude from the Chronic Hypoxia Conference in La Páz.

I was selected to give my presentation, “Colorado Kids Are Smaller” to both conferences. I have been working on this for 20 years. You can read more on our blog where it is titled “Mountain Kids Are Smaller”.  My goal is to get a unique growth chart for children under age two at altitude, to save parents and providers anxiety and money trying to get our kids to “be the same” as those at sea level.

The most useful tidbit of information came on the bus ride back to Calgary. Dr Heimo Mairbaurl, PhD shared that a quarter dose of acetazolamide was sufficient for his acute mountain sickness symptom prevention, 62 mg for a guy over 6 feet tall. Although there was a study on a new possible preventive treatment, prochlorperazine, done on Mount Blue Sky last fall, I still swear by the old drug formerly known as “Diamox”.

Accessibility, Acclimation, Altitude Science, Athletic Training, Child Growth & Development, Exposure, Genetics, Health, High Altitude, Medicine, Postural Orthostatic Tachycardia Syndrome (POTS)

Thin Air Making You Lightheaded?

3 Comments

by Joy Plutowski, PA-S2

Feeling lightheaded after going to a high altitude is a key symptom of acute mountain sickness (AMS)—a condition caused by the reduced oxygen available in thin mountain air. AMS often comes with other symptoms like headache, nausea, and fatigue, usually starting after a recent climb to higher elevations.

But what if it’s not just AMS? For people with conditions like postural orthostatic tachycardia syndrome (POTS), which affects blood flow and heart rate, lightheadedness at altitude could be a clue to an underlying issue. While AMS happens because of low oxygen, POTS is tied to a problem with how the nervous system regulates the body. In some cases, going to altitude might even uncover undiagnosed POTS, as symptoms can become more noticeable in these conditions.

Living With POTS

Living with POTS has been a journey of adaptation, requiring constant vigilance and adjustment to manage a complex array of symptoms. Each new environment brings its own challenges, demanding a personalized approach to maintaining stability. My recent clinical rotation in Frisco, Colorado, situated at 9,000 feet above sea level, provided an invaluable opportunity to observe firsthand how altitude influences the physiology of POTS. An overnight stay in Denver for partial acclimatization helped mitigate some initial altitude-related exacerbations, but the first few days at higher elevation were marked by pronounced symptoms, including lightheadedness, tachycardia, and insomnia. Physically demanding activities, such as snowboarding, pushed my body to its limits, resulting in extreme fatigue and heightened tachycardia. Despite these challenges, I observed gradual improvement; by the second week, I had returned to my baseline—if not better than during my time in the heat of Phoenix, Arizona. Interestingly, the colder temperatures of the region seemed to offer symptomatic relief, likely through vasoconstriction that may enhance circulation. These experiences have deepened my understanding of POTS as a highly individualized condition, emphasizing the critical importance of lifestyle modifications, environmental considerations, and a patient-specific approach to management. My journey underscores how adaptability and tailored interventions can significantly improve functionality and quality of life for those navigating the complexities of this syndrome.

What is POTS?

Postural Orthostatic Tachycardia Syndrome (POTS) is a chronic condition characterized by an abnormal increase in heart rate upon standing. It is a form of dysautonomia, involving dysregulation of the autonomic nervous system, which balances the sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) systems. The autonomic nervous system regulates involuntary bodily functions such as heart rate, blood pressure, and digestion. POTS primarily affects women, with symptoms often appearing in their teens or twenties. It is estimated to affect between 1 to 3 million people in the United States, though it is likely underdiagnosed due to lack of awareness. Under normal conditions, standing triggers the body to constrict blood vessels and slightly increase heart rate to counteract gravity’s effects. In POTS, this response is impaired, leading to blood pooling in the lower extremities and reduced blood flow to the brain. The exact cause of POTS is not fully understood, but it is commonly linked to viral infections, autoimmune conditions, genetic predispositions, small fiber neuropathy, impaired norepinephrine regulation, or hypovolemia (low blood volume). Notably, long-COVID, a range of long-term symptoms and conditions resulting from an acute COVID infection, is linked to POTS. Approximately 1% of patients with an acute COVID-19 infection go on to develop orthostatic intolerance (Cheshire, 2024). Studies also show that keeping up with COVID-19 vaccinations can prevent long-COVID.

The hallmark symptom of POTS is an excessive increase in heart rate of over 30 bpm quickly after standing (WP, 2024). Common symptoms include tachycardia, palpitations, dizziness, and fainting (syncope or near-syncope), brain fog, headaches, lightheadedness, and severe fatigue. Less common symptoms include nausea, bloating, abdominal discomfort, shakiness, and exercise intolerance. POTS symptoms are often worsened by factors such as dehydration, heat, prolonged standing, illness, or physical stress. Diagnosing POTS involves a tilt-table test which monitors heart rate and blood pressure during positional changes. Treatment for POTS focuses on improving symptoms and quality of life through lifestyle adjustments. Key components include hydration, increased salt intake, compression garments, graded exercise therapy, and psychological support. Medications such as Fludrocortisone or Midodrine, that both increase blood pressure, may be added if the provider deems it fit. The course of POTS varies widely; some individuals experience significant improvement with treatment, others may have persistent symptoms. Early diagnosis and a multidisciplinary approach can lead to better outcomes.

The Effect of Altitude on the Autonomic Nervous System

Altitude significantly influences the autonomic nervous system due to reduced oxygen levels and atmospheric pressure, which challenge the body’s ability to maintain homeostasis. At higher elevations, the sympathetic nervous system becomes more active, increasing heart rate and blood pressure to compensate for lower oxygen availability. This is because hypoxia alters chemoreceptor and baroreceptor function, leading to increased sympathetic excitation and decreased parasympathetic tone.

During a study at 4300 m, urine norepinephrine levels—a marker of sympathetic activity—peaked 4–6 days after altitude exposure (Mazzeo, 1998). The study compared women in different hormonal phases when exposed to high altitude. The urinary norepinephrine levels heart rates both increased over time in both follicular and luteal phases. The differences between the two were not statistically significant, showing that women experience sympathetic increase at altitude regardless of what phase of their cycle. This was done in comparison to a previous study showing the same findings in men (Mazzeo, 1998). 

A line graph indicating the rise follicular and luteal heart rates in beats per minute as days at altitude increase.
A line graph indicating increasing amounts per 24 hours of urinary norepinephrine.

Other physiological responses include increased ventilation, cardiac output, and heart rate. However, with acclimatization, heart rate and cardiac output typically return to sea-level values within 9–12 days (Hainsworth et al., 2007). Over time, improved oxygen-carrying capacity enhances tolerance to orthostatic stress. All in all, orthostatic tolerance during hypobaric hypoxia involves three mechanisms: cardiovascular control of heart rate and cardiac output, cerebrovascular responses to hypocapnic hypoxia (due to hyperventilation), and elevated sympathetic activity (Blaber et al., 2003). 

For individuals with POTS, altitude-related stresses may exacerbate symptoms. Hypoxia and reduced barometric pressure can worsen fatigue, brain fog, and dizziness by increasing the body’s effort to oxygenate tissues. Reduced oxygen delivery to the brain and tissues may intensify lightheadedness and syncope— which is already common in POTS.

Although acclimatization typically occurs within 1–2 weeks at altitude in healthy individuals, research on acclimatization in POTS patients is limited. Further studies are needed to determine whether individuals with autonomic dysfunction can adapt as effectively as those without.

Living With POTS at Altitude 

Living with POTS at altitude presents unique challenges that require careful management, as patients may find it harder to adapt to the altitude-induced changes in blood oxygenation and pressure regulation. These challenges are compounded by the existing difficulties they face in maintaining autonomic stability. The reduced oxygen levels and increased demands on the cardiovascular system can amplify POTS symptoms, making daily activities more difficult. Patients with POTS generally understand their triggers and have a protocol that was formulated with their provider. Such strategies include staying well-hydrated, using compression garments, increasing salt intake, decreasing alcohol and caffeine consumption, and avoiding sudden changes in posture. Also, gradual exposure to altitude helps the body adapt to the reduced oxygen and barometric pressure, minimizing symptom flares. For individuals with POTS visiting high-altitude environments, strict adherence to their treatment regimen, including lifestyle modifications and potentially pharmacologic interventions, is paramount for managing their condition effectively.

References

Blaber AP, Hartley T, Pretorius PJ (2003) Effect of acute exposure to 3,660 m altitude on orthostatic responses and tolerance. J Appl Physiol 95:591–601

Cheshire WP. (2024) Postural tachycardia syndrome. UpToDate. 

Hainsworth, R., Drinkhill, M. J., & Rivera-Chira, M. (2007). The autonomic nervous system at high altitude. Clinical autonomic research : official journal of the Clinical Autonomic Research Society, 17(1), 13–19

Mazzeo RS, Child A, Butterfield GE, et al. (1998) Catecholamine response during 12  days of high-altitude exposure (4,300 m) in women. J Appl Physiol 84:1151–1157

Joy Plutowski is a second-year PA student born and raised in Arizona. She completed her undergraduate degree in biology at Arizona State University and is now pursuing her master’s at Midwestern University in Glendale, AZ. Before PA school, she worked as a medical scribe for an interventional cardiologist, a field she is interested in pursuing. Currently, she has the wonderful opportunity of completing her pediatrics rotation in Frisco, CO. In her free time, Joy enjoys exploring national parks, playing video games, dancing, and most recently, snowboarding. 

Acclimation, Altitude Science, Backcountry, Backpacking, Health, High Altitude, Huts, Medicine, Mountaineering, Technology

New Use for Existing Technology and HAPE/HACE

Leave a comment

by Kaity Barker-Grasser, FNP

Ultrasound itself is not an unfamiliar technology to most, having been used in obstetrics and gynecology (OB/GYN) for many years. Newer research is now showing that ultrasound imaging may have good applicability in both high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). Pulmonary edema (or fluid in the lungs) is identified as “B-lines” or “comet tails” and is easily distinguishable on ultrasound (Gargani, 2019).

Illustration of the rib cage and clavicle bones indicating different probe positions to scan the lung using Ultrasound, accompanied by two images of lung Ultrasounds where asterisks indicate shadows of the ribs and white arrows indicating the pleural line.
Gargani, 2019

Using ultrasound to measure the diameter of the optic nerve can also assist with a diagnosis of HACE, as an increased diameter indicates increased intercranial pressure from HACE (Shookahi et al., 2020). The advantages of ultrasound over traditional imaging include being highly portable and usable in austere environments (such as back country), no radiation like many other imaging techniques, accurate for diagnosing pulmonary edema and other conditions, and takes little time for providers to master. Ultrasound also has a significant cost savings as the machine itself is relatively inexpensive, does not require special construction like adding lead to an Xray room, and is applicable in many other diagnoses (including kidney disorders, gallbladder disease, pneumonia, trauma, muscular disorders, and gynecological complaints). Ultrasound also has the capability to differentiate types of pulmonary edema, as well as other lung disorders, and generally much faster than a traditional Xray as there is no radiographic lag between clinical onset and ultrasound changes.

Three x-ray images displaying different etiologies of B-lines: cardiogenic pulmonary edema, noncardiogenic pulmonary edema, and pulmonary fibrosis.
Pulmonary Edema on Xray, Mayo Clinic, 2024

Pulmonary Edema on Xray Mayo Clinic, 2024

In HAPE, an increase in the number of B-lines indicates an accumulation of fluid in the lungs. Healthy individuals acclimating to the altitude have been shown to have a physiologic increase in B-lines during the first 4 days of high-altitude exposure as well as pregnant individuals having an increase in their baseline b-line count. Keeping these differences in mind, an increase of B-lines of more than 3 in a lung field, in more than 2 lung fields indicates an increase in extravascular lung water (EVLW) and could support a diagnosis of HAPE. Correlating this with clinical signs and symptoms of altitude sickness (HA, dizziness, fatigue, shortness of breath, nausea/vomiting), as well as HAPE (hypoxia, cough, exercise intolerance) can support a more rapid diagnosis of HAPE as well as assist with deciding need for oxygen and/or altitude descent (Yang et al., 2018; Heldeweg et al., 2022). The provider can also use the ultrasound to monitor resolution of the pulmonary edema to help support decisions to discontinue oxygen or to encourage altitude descent. Those with comorbidities such as heart failure can also be monitored for early signs that their treatment plan is not adequately addressing their EVLW and can receive correction prior to needing hospitalization (Chiu et al., 2022).

Two x-ray images of the chest from the Mayo Clinic labelled cardiogenic and HAPE/noncardiogenic from left to right.

Pulmonary Edema on Xray Mayo Clinic, 2024

HACE, as a disorder including altered mental status, ataxia, headache, loss of consciousness, and seizures, is a serious complication of high altitude. As the symptoms suggest, rapid identification is key to reducing other problems, including death, from HACE. The use of ultrasound is relatively new in assisting with diagnosis, but an increase in optic nerve diameter on ultrasound above 5 millimeters indicates that there is a good chance of brain swelling (or cerebral edema) and subsequent increased intracranial pressure. Identifying this early allows for rapid decision making the descent to a lower altitude or using a more rapid evacuation method (helicopter or rapid ground transport). Increased intracranial pressure can also result from head injury or trauma and thus can be useful in settings where an injury may have occurred. This makes this a tool that could be invaluable in search and rescue operations or for first responders (Shookahi et al., 2020).

Four Ultrasound images of the lungs illustrating use as a densitometer: different ultrasound patterns for different levels of lung aeration. Below the images, a graph indicating lung air content from 100% on the left to 0% on the right.
Gargani, 2019

Keeping these benefits in mind, remember that diagnostic imaging is a support tool and not the complete answer to all health problems. Hopefully soon we will see this tool being used with more frequency to help aid our healthcare providers in determining a more accurate cause of symptoms!

References

Chiu, L., Jairam, M. P., Chow, R., Chiu, N., Shen, M., Alhassan, A., Lo, C.-H., Chen, A., Kennel, P. J., Poterucha, T. J., & Topkara, V. K. (2022). Meta-Analysis of Point-of-Care Lung Ultrasonography Versus Chest Radiography in Adults With Symptoms of Acute Decompensated Heart Failure. The American Journal of Cardiology, 174, 89–95. https://doi.org/10.1016/j.amjcard.2022.03.022

Gargani L. (2019). Ultrasound of the Lungs: More than a Room with a View. Heart Failure Clinics, 15(2), 297–303. https://doi.org/10.1016/j.hfc.2018.12.010

Heldeweg, M. L. A., Smit, M. R., Kramer-Elliott, S. R., Haaksma, M. E., Smit, J. M., Hagens, L. A., Heijnen, N. F. L., Jonkman, A. H., Paulus, F., Schultz, M. J., Girbes, A. R. J., Heunks, L. M. A., Bos, L. D. J., & Tuinman, P. R.. (2022). Lung Ultrasound Signs to Diagnose and Discriminate Interstitial Syndromes in ICU Patients: A Diagnostic Accuracy Study in Two Cohorts*. Critical Care Medicine, 50(11), 1607–1617. https://doi.org/10.1097/ccm.0000000000005620

Mayo Clinic (2024). Pulmonary Edema. Mayo Foundation for Medical Education and Research. Retrieved February 27, 2024 from https://www.mayoclinic.org/diseases-conditions/pulmonary- edema/symptoms-causes/syc-20377009

Shokoohi, H., Pyle, M., Kuhl, E., Loesche, M. A., Goyal, A., LeSaux, M. A., Boniface, K. S., & Taheri, M. R. (2020). Optic Nerve Sheath Diameter Measured by Point-of-Care Ultrasound and MRI. Journal of neuroimaging : official journal of the American Society of Neuroimaging, 30(6), 793–799. https://doi.org/10.1111/jon.12764

Yang, W., Wang, Y., Qiu, Z., Huang, X., Lv, M., Liu, B., Yang, D., Yang, Z., & Xie, T.. (2018). Lung Ultrasound Is Accurate for the Diagnosis of High-Altitude Pulmonary Edema: A Prospective Study. Canadian Respiratory Journal, 2018, 1–9. https://doi.org/10.1155/2018/5804942

Acclimation, Altitude Science, Child Growth & Development, Genetics, Health, High Altitude, Huts, Medicine, Summit Huts

Unveiling the Hidden Risks of Living at High Altitude on our Kidney Health, and What it Might Mean for Your Child

Leave a comment

The hallmark concern for the body living at high altitude is low oxygen. We breathe in less, and thus less is sent throughout our blood stream to our tissues. We are quick to think about how this affects our heart and lungs, but what about our kidneys? What are our kidneys even responsible for?

Kidneys filter, reabsorb, and excrete our blood in the form of urine. They connect our cardiovascular system with our genitourinary system. The flow through the kidneys also helps monitor and adjust our blood pressure. Their importance is truly undervalued. When they receive less oxygen than preferred (hypoxia), they will become injured. Specifically, the glomerulus (term for the filter) will become affected. When this happens, it is not efficient at filtration, and protein will spill out into our urine (proteinuria), a key feature of High Altitude Renal Syndrome (HARS).

Zooming further in below

And even further…

Another issue involves uric acid, the chemical at fault for causing gout. Due to the filter injury sustained from low oxygen, uric acid excretion is affected. It can thus build up in our musculoskeletal system and other tissues. It is famous for causing red, swollen, and painful joints. The enzyme that helps create uric acid (xanthine oxidase) is also turned on by reactive oxygen species during hypoxia. This then causes further uric acid crystal deposition in our body. This can present in patients from adolescent years through adulthood, ranging from fleeting pain to amputations from severe bone infections. We have found that for younger patients, diet plays a lesser part than genetic predisposition and hypoxia.

So how is this treated? We are still researching the best course of action. We can treat with drugs that work by inhibiting the previously specified enzyme: xanthine oxidase. These include oral allopurinol, febuxostat, and even IV pegloticase infusions. But we are primarily focused on prevention and holistic care here, so we would prefer to use supplemental oxygen therapy for those that struggle to maintain oxygen saturations in the healthy ranges. Acetazolamide is also helpful in cases. This medication works to increase our respiratory drive, helping us breathe off CO2 and breathe in more oxygen. Contact us to see what method might be right for you.

This research was brought to us by a stroke of luck. A stranger on an airplane, and a son’s coworker. This stranger happened to be a nephrologist (kidney doctor) who is studying how altitude affects the kidneys. In working with him and his team at University of Colorado Anschutz, the team at Ebert Family Clinic in Frisco, Colorado (9000′) have been ordering broader lab panels (including uric acid) for their patients and seeking those with questionable renal labs. Another patient seen by the Ebert Family Clinic team has been severely impacted by gout. With multiple amputations before the patient’s 30th birthday, this case has motivated the health care team to prevent this from happening to others in their high altitude community.

Screenshot

Carter Odean is a third-year medical student at Rocky Vista University. He was born and raised outside of Denver, Colorado before heading to Gonzaga University in Spokane, Washington where he studied biology and completed research on an invasive bee species there while playing club lacrosse. After graduating in 2019, he then came back to Denver to complete his Master’s in Biomedical Sciences at Regis University. After Regis, he started as a Clinical Research Coordinator at Anschutz Medical campus, working on multiple Diabetes Mellitus Type 2 research trials. He is in the Rural & Wilderness Track which is his favorite part about school. He plans to work as a rural Pediatrician or Family Medicine Physician. In his free time, you can find him dirt biking, fly fishing, skiing, and relaxing with friends and family. 

References

  1. Schoene, R.B. “High altitude renal syndrome: polycythemia, hyperuricemia, microalbuminuria, and hypertension.” High Alt Med Biol. 2002 Spring;3(1):65-73. doi: 10.1089/152702902753639371. PMID: 11949751.
  2. Bigham, A.W., Lee, F.S. “Tibetan and Andean patterns of adaptation to high-altitude hypoxia.” Hum Biol. 2014 Oct;86(4):321-37. doi: 10.3378/027.086.0401. PMID: 25700353; PMCID: PMC4438718.
  3. Beall, C.M., Cavalleri, G.L., Deng, L., et al. “Natural selection on EPAS1 (HIF2α) associated with low hemoglobin concentration in Tibetan highlanders.” Proc Natl Acad Sci U S A. 2010 Mar 9;107(25):11459-64. doi: 10.1073/pnas.1002443107. Epub 2010 Feb 22. PMID: 20176925; PMCID: PMC2895106.
  4. Simonson, T.S., Yang, Y., Huff, C.D., et al. “Genetic evidence for high-altitude adaptation in Tibet.” Science. 2010 Sep 10;329(5987):72-5. doi: 10.1126/science.1189406. PMID: 20616233; PMCID: PMC3490534.
  5. Schoene, R.B., Swenson, E.R. “Cobalt-Induced Chronic Mountain Sickness: Pathophysiological Mechanisms and Genetic Susceptibility.” High Alt Med Biol. 2017 Mar;18(1):1-5. doi: 10.1089/ham.2016.0106. PMID: 28145824.Baillie, J.K., Bates, M.G., Thompson, A.A., et al. “Endogenous urate production augments plasma antioxidant capacity in healthy lowland subjects exposed to high altitude.” Chest. 2007 Dec;132(6):S275. doi: 10.1378/chest.132.6.275. PMID: 18079246.
  6. Yu, K.H., Wu, Y.J., Tseng, W.C., et al. “Risk of end-stage renal disease associated with gout: a nationwide population study.” Arthritis Res Ther. 2012 Jun 27;14(3):R83. doi: 10.1186/ar3818. PMID: 22738152; PMCID: PMC3446515.
  7. Bhat, A., Deshmukh, A., Anand, S., et al. “Acute Myocardial Infarction due to Coronary Artery Embolism in a Patient with Severe Hyperuricemia.” J Assoc Physicians India. 2019 Nov;67(11):90-91. PMID: 31801335.
  8. Khanna, D., Khanna, P.P., Fitzgerald, J.D., et al. “2012 American College of Rheumatology guidelines for management of gout. Part 1: systematic nonpharmacologic and pharmacologic therapeutic approaches to hyperuricemia.” Arthritis Care Res (Hoboken). 2012 Oct;64(10):1431-46. doi: 10.1002/acr.21772. PMID: 23024028.
  9. Schoene, R.B., Swenson, E.R. “Treatment of Cobalt-Induced Chronic Mountain Sickness.” High Alt Med Biol. 2017 Mar;18(1):74-77. doi: 10.1089/ham.2016.0135. PMID: 28145823.
  10. Schoene, R.B., Hackett, P.H., Henderson, W.R., et al. “High Altitude Medicine and Physiology, Fourth Edition.” CRC Press, 2007.
  11. Burtscher, M., Mairer, K., Wille, M., et al. “Risk of acute mountain sickness in tourists ascending to 4360 meters by cable car.” High Alt Med Biol. 2004 Summer;5(2):141-6. doi: 10.1089/1527029041352154. PMID: 15265307.
  12. Baumgartner, R.W., Bärtsch, P. “Chronic mountain sickness and the heart.” Prog Cardiovasc Dis. 2010 May-Jun;52(6):540-9. doi: 10.1016/j.pcad.2010.02.009. PMID: 20417390.