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The Frisco Score: A New Tool for Diagnosing HAPE

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by Madison Palmiero, PA-S

While HAPE may be a run-of-the-mill diagnosis for providers with years of experience practicing at altitude, it can be less straightforward for those who are unfamiliar with the condition. There are currently three recognized categories of HAPE. Classic HAPE (C-HAPE)  occurs when someone who resides at low altitude travels to high altitude and develops pulmonary edema. Re-entry HAPE (R-HAPE) occurs when high altitude residents travel to low altitude, then return to high altitude. High-altitude resident pulmonary edema (HARPE) occurs in high altitude residents without a change in altitude. HARPE is often brought on by an upper respiratory tract infection. 

HAPE and pneumonia can have similar presentations including shortness of breath, cough, fatigue, and malaise. Patients with either condition may have decreased oxygen saturation levels and abnormal findings on chest radiography. In response to this phenomena, Dr. Chris Ebert-Santos of Ebert Family Clinic in Frisco, Colorado (9000′) and Sean Finnegan, PA-C set out to develop a scoring system to differentiate the two diagnoses. If providers could easily differentiate between pneumonia and HAPE, this would shorten the time from presentation to diagnosis and would avoid unnecessary antibiotic use.

Dr. Chris and Sean Finnegan, PA-C summarized their research findings into a scoring system named the “Frisco Score”. They analyzed data from St. Anthony Summit Medical Center and associated clinics at or above ~2,760 meters above sea level from January 1, 2018 to May 30, 2023. The study looked at patients under the age of 19 who presented with hypoxemia or other respiratory concerns and had a chest x-ray performed and oxygen saturation measured. The final case review consisted of 138 total patients with 77 diagnosed with HAPE, 38 diagnosed with pneumonia, and 23 diagnosed with concomitant HAPE and pneumonia. Variables found to have no significance included gender, age, heart rate, and temperature. Variables with significance included respiratory rate, number of days ill, oxygen saturation, and chest x-ray findings. These significant variables were used to develop the Frisco Score. They do include a disclaimer that these findings are preliminary results on a small data set. Thus, as of yet, the Frisco Score should not be used on its own to make a diagnosis, but rather should be used as a clinical tool in differentiating conditions with similar presentations. 

Oxygen saturation varied greatly between patients with HAPE and those with pneumonia. Patients diagnosed with HAPE had an average oxygen saturation of 74% and those with pneumonia had an average of 92%. 

Patients who were diagnosed with HAPE had a higher average respiratory rate compared to those diagnosed with pneumonia.

 In patients diagnosed with HAPE, the duration of illness, or number of days ill, was shorter than those diagnosed with pneumonia. 

In comparison of chest x-rays, patients with HAPE were more likely to have diffuse findings and patients with pneumonia were more likely to have focal findings. 

Overall, there were no variables associated with a concomitant diagnosis of pneumonia and HAPE.

The asphalt road in the foreground leads past a sign for Common Spirit St. Anthony Summit Hospital just before the shelter over the entrance to a building labeled "ambulance" with deep green conifer forests stretching halfway up tall grey rocky mountains in the backgroundl.

In summary, patients diagnosed with HAPE had decreased oxygen saturation, increased respiratory rate, and diffuse findings on chest x-ray; while patients diagnosed with pneumonia had a longer duration of illness and focal findings on chest x-ray. The Frisco Score takes these variables into account to help differentiate a diagnosis of HAPE in children. Dr. Chris and Sean Finnegan, PA-C are currently presenting their findings at the 8th World Congress on Mountain and Wilderness Medicine in Snowbird, Utah. They hope that in the near future, the Frisco Score will be used to facilitate the diagnosis of HAPE by providers in high altitude communities state-wide.

References

1. Ebert-Santos, C. (2017). High-Altitude Pulmonary Edema in Mountain Community Residents. High Altitude Medicine & Biology, 18 (3), 278-284. https://doi.org/10.1089/ham.2016.0100

2. Ebert-Santos, C., Finnegan, S. (2024). Differentiating Pneumonia & HAPE in Children.

Accessibility, Acclimation, Backpacking, Doc Talk, Health, High Altitude

The High Altitude Doc Visits Norway

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Founder of Ebert Family Clinic in Frisco, Colorado at 9000′, Christine Ebert-Santos, MD, MPS spent a part of her Spring 2024 backpacking across Norway:

At 2,469m (8,100 feet), Galdhøpiggen mountain in Norway is not high enough to cause altitude sickness for most people. The 300 mountain peaks over 2000m make Norway a popular destination for downhill skiing and snowboarding, as well as Nordic skiing. The long days of sunshine at this latitude allow skiing in swimsuits and summer clothes in the spring.

Norway also has the largest glacier in Europe, Jostedalsbreem. Briksdalbreen is a finger of this glacier that is a short hike in the Jostedalsbreem National Park. There are 1,600 glaciers covering one percent of Norway. Several have resorts advertising summer skiing for the whole family.

View of a backseat passenger of a driver and front seat passenger looking over a navigation screen out toward a tunnel extending beyond the car windshield before them.

 

There are 900 tunnels in Norway, including the longest tunnel in the world. Compared to Eisenhower Tunnel in Colorado at 11,112 feet elevation and 1.67 miles long, Laerdal tunnel, opened in 2000, is 15 miles long with pullouts featuring colored lighting to imitate the sunrise. Some of these tunnels, like the one between the airport and downtown Oslo, go as deep as 958 feet underwater. All have phones and excellent cell phone reception. In fact, we experienced excellent reception everywhere in Norway despite the mountains and tunnels, in contrast to my sister’s house in Centennial, Colorado and many parts of Colorado.

A bright-orange-beaked puffin sits in grass amidst stones with its bright orange feet sticking out from under its black wings and white-feathered breast.

 Our last night in Norway was special. We drove two hours over narrow roads, through tunnels, over one lane bridges to Ronde Island. With a population of 150, the island is a famous bird sanctuary. We arrived just in time to see the puffins return to their nests at 8 pm.  These colorful birds spend their lifespan of 30-40 years flying over the ocean, sleeping on the waves, returning to land once a year with the same mate.

An aerial view of large, snow-capped mountains over a town down in the valley of a deep fjord with blue, sunny skies with billowy, bright clouds.

The fact that Norway provides such amazing access to even this tiny town tells me how much they respect individuals. They have an average lifespan of 83 years (76 years in the USA), universal health care, one year paid leave for parents with a new baby, universal pensions, free education through college, daycare for less than $15/day, and much more. How much do they pay in taxes, you might ask? Less than what we pay when you consider the cost of health insurance, day care, school loans, with 60% of Americans who do not have anything saved for retirement.

Acclimation, Altitude Science, Asthma, Child Growth & Development, COVID-19, Doc Talk, Exposure, Genetics, Health, High Altitude, Medicine, Mountaineering, Pandemic, Sleep at Altitude, Technology

Can I Ever Go Back Up To High Altitude Again? – Recurrence Risk of HAPE & HARPE

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by Taylor Kligerman, PA-S

Can I ever return to high altitude? Do I need to move down to a lower elevation?

Disease processes often differ at high altitudes. Some conditions have only been known to occur at high elevations. Most of the resources cited in this blog refer to ‘high altitude’ being at or above 2,500 meters or 8,200 feet.

Ebert Family Clinic in Frisco, Colorado is at 9,075 ft. Many areas in the immediate vicinity are over 10,000′, with some patients living above 11,000′. Two of the more common conditions seen in patients at Ebert Family Clinic are high altitude pulmonary edema (HAPE) and high altitude resident pulmonary edema (HARPE), similar conditions that affect slightly different populations in this region of the Colorado Rocky Mountains.

In “classic” HAPE, a visitor may come from a low-altitude area to Frisco on a trip to ski with friends. On the first or second day, the person notices a nagging cough. They might wonder if they caught a virus on the plane ride to Denver. The cough is usually followed by shortness of breath that begins to make daily tasks overwhelmingly difficult. One of the dangerous aspects of HAPE is a gradual onset leading patients to believe their symptoms are caused by something else. A similar phenomenon is seen in re-entry HAPE, where a resident of a high altitude location travels to low altitude for a trip and upon return experiences these same symptoms [1].

In HARPE, a person living and working here in Frisco may be getting ill or slowly recovering from a viral illness and notices a worsening cough and fatigue. These cases are even more insidious, going unrecognized, and so treatment is sought very late. Dr. Christine Ebert-Santos and her team at Ebert Family Clinic hypothesize that while residents have adequately acclimated to the high-altitude environment, the additional lowering of blood oxygen due to a respiratory illness with inflammation may be the inciting event in these cases.

In both cases, symptoms are difficult to confidently identify as a serious illness versus an upper respiratory infection, or simply difficulty adjusting to altitude. For this reason, Dr. Chris recommends that everyone staying overnight at high altitude obtain a pulse oximeter. Many people became familiar with the use of these instruments during the COVID-19 pandemic. The pulse oximeter measures what percent of your blood is carrying oxygen. At high altitude, a healthy level of oxygenation is typically ≥90%. This is an easy way to both identify potential HAPE/HARPE, as well as reassure patients they are safely coping with the high-altitude environment [2].

HAPE and HARPE are both a direct result of hypobaric hypoxia, a lack of oxygen availability at altitude due to decreased atmospheric pressures. At certain levels of hypoxia, we observe a breakdown in the walls between blood vessels and the structures in lungs responsible for oxygenating blood. The process is still not totally understood, but some causes of this breakdown include an inadequate increase in breathing rates, reduced blood delivered to the lungs, reduced fluid being cleared from the lungs, and excessive constriction of blood vessels throughout the body. These processes cause fluid accumulation throughout the lungs in the areas responsible for gas exchange making it harder to oxygenate the blood [3].

We do know that genetics play a significant role in a person’s risk of developing HAPE/HARPE. Studies have proposed many different genes that may contribute, but research has not, so far, given healthcare providers a clear picture of which patients are most at-risk. Studies have shown that those at higher risk of pulmonary hypertension (high blood pressure in the blood vessels of your lungs), are more likely to develop HAPE [4]. This includes some types of congenital heart defects [5,6]. High blood pressures in the lungs reach a tipping point and appear to be the first event in this process. However, while elevated blood pressures in the lungs are essential for HAPE/HARPE, this by itself, does not cause the condition. The other ingredient necessary for HAPE/HARPE to develop is uneven tightening of the blood vessels in the lungs. When blood vessels are constricted locally, the blood flow is shifted mainly to the more open vessels, and this is where we primarily see fluid leakage. As the blood-oxygen barrier is broken down in these areas, we may also see hemorrhage in the air sacs of the lungs [3].

One observation healthcare providers and scientists have observed is that HAPE/HARPE can be rapidly reversed by either descending from altitude or using supplemental oxygen. Both strategies increase the availability of oxygen in the lungs, reducing the pressure on the lungs’ blood vessels by vasodilation, quickly improving the integrity of the blood-oxygen barrier.

In a preliminary review of over 100 cases of emergency room patients in Frisco diagnosed with hypoxemia (low blood oxygen content) Dr. Chris and her team have begun to see trends that suggest the availability of at-home oxygen markedly reduces the risk of a trip to the hospital. This demonstrates that patients with both at-home pulse oximeters and supplemental oxygen have the capability to notice possible symptoms of HAPE, assess their blood oxygen content, and apply supplemental oxygen if needed. This stops the development of HAPE/HARPE before damage is done in the lungs. In the case of many of our patients, these at-home supplies prevent emergencies and allow patients time to schedule an appointment with their primary care provider to better evaluate symptoms.

Additionally, Dr. Chris and her team have observed that patients with histories of asthma, cancer, pneumonia, and previous HAPE/HARPE are often better educated and alert to these early signs of hypoxia and begin treatment earlier on in the course of HAPE/HARPE, reducing the relative incidence identified by medical facilities. There are many reasons to seek emergent care such as low oxygen with a fever. Patients with other existing diseases causing chronically low oxygen such as chronic lung disease may not be appropriately treated with  supplemental oxygen, although this is a very small portion of the population. Discussions with healthcare providers on the appropriate prevention plan for each patient will help educate and prevent emergency care visits in both residents and visitors.

A young child with short brown hair and glasses with dark, round frames wears a nasal canula for oxygen.

Studies of larger populations have yet to be published. A review of the case reports in smaller populations suggests that the previously estimated recurrence rate of 60-80% is exaggerated. This is a significant finding as healthcare providers have relied on this recurrence rate to make recommendations to their patients who have been diagnosed with HAPE. A review of 21 cases of children in Colorado diagnosed with HAPE reported that 42% experienced at least one recurrence [7]. This study was conducted by voluntary completion of a survey by the patients (or their families) which could lead to significant participation bias affecting the results. Patients more impacted by HAPE are more likely to complete these surveys. Another study looking at three cases of gradual re-ascent following an uncomplicated HAPE diagnosis showed no evidence of recurrence. The paper also suggested there may be some remodeling of the lung anatomy after an episode of HAPE that helps protect a patient from reoccurrence [8]. Similar suggestions of remodeling have been proposed through evidence of altitude being a protective factor in preventing death as demonstrated by fatality reports from COVID-19[9].

Without larger studies and selection of participants to eliminate other variables like preexisting diseases, we are left to speculate on the true rate of reoccurrence based on the limited information we have. Strategies to reduce the risk of HAPE/HARPE such as access to supplemental oxygen, pulse oximeters, and prescription medications [10] are the best way to prevent HAPE/HARPE. Research should also continue to seek evidence of individuals most at risk for developing HAPE/HARPE [11].

A woman with reddish-brown, straight hair just below her shoulders, wears a white coat over a mustard-colored shirt, smiling.

Taylor Kligerman is a third-year medical student at Rocky Vista University with plans to complete a residency in emergency medicine. She was born and raised in Flossmoor, IL, and became interested in medicine following her first medical mission trip to Gonaïves, Haiti in 2010. Taylor has extensive experience in wilderness and remote emergency medicine. Before starting medical school, she was certified as a wilderness EMT and gained experience in remote areas of Canada and Western North Carolina on whitewater expeditions and as a volunteer with local search and rescue. Her personal interests include camping, skiing, and all paddle sports.

References

  1. Ucrós S, Aparicio C, Castro-Rodriguez JA, Ivy D. High altitude pulmonary edema in children: A systematic review. Pediatr Pulmonol. 2023;58(4):1059-1067. doi:10.1002/ppul.26294
  2. Deweber K, Scorza K. Return to activity at altitude after high-altitude illness. Sports Health. 2010;2(4):291-300. doi:10.1177/1941738110373065
  3. Bärtsch P. High altitude pulmonary edema. Med Sci Sports Exerc. 1999;31(1 Suppl):S23-S27. doi:10.1097/00005768-199901001-00004
  4. Eichstaedt C, Benjamin N, Grünig E. Genetics of pulmonary hypertension and high-altitude pulmonary edema. J Appl Physiol. 2020;128:1432
  5. Das BB, Wolfe RR, Chan K, Larsen GL, Reeves JT, Ivy D. High-Altitude Pulmonary Edema in Children with Underlying Cardiopulmonary Disorders and Pulmonary Hypertension Living at Altitude. Arch Pediatr Adolesc Med. 2004;158(12):1170–1176. doi:10.1001/archpedi.158.12.1170
  6. Liptzin DR, Abman SH, Giesenhagen A, Ivy DD. An Approach to Children with Pulmonary Edema at High Altitude. High Alt Med Biol. 2018;19(1):91-98. doi:10.1089/ham.2017.0096
  7. Kelly TD, Meier M, Weinman JP, Ivy D, Brinton JT, Liptzin DR. High-Altitude Pulmonary Edema in Colorado Children: A Cross-Sectional Survey and Retrospective Review. High Alt Med Biol. 2022;23(2):119-124. doi:10.1089/ham.2021.0121
  8. Litch JA, Bishop RA. Reascent following resolution of high altitude pulmonary edema (HAPE). High Alt Med Biol. 2001;2(1):53-55. doi:10.1089/152702901750067927
  9. Gerken J, Zapata D, Kuivinen D, Zapata I. Comorbidities, sociodemographic factors, and determinants of health on COVID-19 fatalities in the United States. Front Public Health. 2022;10:993662. Published 2022 Nov 3. doi:10.3389/fpubh.2022.993662
  10. Luks A, Swenson E, Bärtsch P. Acute high-altitude sickness. European Respiratory Review. 2017;26: 160096; DOI: 10.1183/16000617.0096-2016
  11. Dehnert C, Grünig E, Mereles D, von Lennep N, Bärtsch P. Identification of individuals susceptible to high-altitude pulmonary oedema at low altitude. European Respiratory Journal 2005;25(3):545-551; DOI: 10.1183/09031936.05.00070404
Accessibility, Acclimation, Altitude Science, Asthma, Child Growth & Development, Doc Talk, Exposure, Genetics, Health, High Altitude, Medicine

Hypoxia in the Emergency Department: Preliminary Analysis of Data from the Highest Atitude Population in North America & Children with Hypoxia

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Hypoxia is a common presentation at the emergency department for the St Anthony Summit Medical Center, located at 2800 meters above sea level (msl) in Colorado. Children under 18 are brought in with respiratory symptoms, trauma, congenital heart and lung abnormalities, and high altitude pulmonary edema (HAPE). Many complain of shortness of breath and/or cough and are found to be hypoxic, defined as an oxygen saturation below 89% on room air for this elevation. Patients who live at altitude may perform home pulse oximetry and arrive for treatment and diagnosis of known hypoxia. Extensive and ongoing analysis of the data from children found to be hypoxic in the emergency department raises many questions, including how residents vs nonresidents present, how often  these cases are preceded by febrile illness and what chief complaint is most frequently cited. 

Understanding the presentation of hypoxia in children at altitude can help ensure that healthcare providers are following a comprehensive approach with awareness of the overlapping symptoms of HAPE, pneumonia and asthma. Below is a graphic summary of 36 cases illustrating the clinical, social and geographic factors contributing to hypoxia at altitude in residents and visitors. A further analysis of over 200 children with hypoxia presenting to the emergency room at 9000 feet is underway including x-ray findings.

The graphs below were created by the author, using data extracted directly from a review of patient charts (specifically, those of children presenting to the local hospital in Summit County, Colorado (9000 feet) with hypoxia).

Graphs 1-4 show chief complaints of cough (CC) and shortness of breath (SOB) compared by age and by residence (residence includes altitudes above 2100 msl, the front range (a high altitude region of the Rocky Mountains running north-south between Casper, Wyoming and Pueblo, Colorado) averaging 1500 msl, and out of the state of Colorado) 

A graph of age with blue bars Description automatically generated
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Graphs 5-6 show presence of fever by residence and by age 

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Graphs 7-8 show presence of asthma by residence and by age 

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Graphs 9 and 10 show lowest oxygen by age at admission and lowest O2 organized by days spent in the county (residents are excluded from this data). 

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A graph with blue dots Description automatically generated

Erin Snyder is a new graduate physician assistant who graduated this fall after spending her final rotation in Frisco with the Ebert clinic. She is now working in pediatric hematology at Children’s Hospital Colorado. And her free time she enjoys skiing, hiking and spending time with her cat Charlie.

Acclimation, Altitude Science, Asthma, Athletic Training, Child Growth & Development, Doc Talk, Exposure, Health, High Altitude, High Altitude Training & Fitness, Medicine, Mountaineering

Doc Talk: Physician Altitude Experts on High Altitude Pulmonary Edema (HAPE)

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One of our students recently came across a comprehensive publication on high altitude pulmonary edema (HAPE) on reputable point-of-care clinical resource UpToDate.com1, citing Christine Ebert-Santos, MD, MPS, the founder of highaltitudehealth.com.

Emergency medicine physician at Aspen Valley Hospital and medical director for Mountain Rescue Aspen since 1997 Dr. Scott A. Gallagher2 and emergency physician and altitude research pioneer Dr. Peter Hackett3 introduce the resource warning, “Anyone who travels to high altitude, whether a recreational hiker, skier, mountain climber, soldier, or worker, is at risk of developing high-altitude illness.”

Ebert-Santos’s (known affectionately to her patients and mountain community as “Dr. Chris”) own research is referenced in the article’s discussion of epidemiology and risk factors noting an additional category of HAPE among “children living at altitude who develop pulmonary edema with respiratory infection but without change in altitude,”4 whereas the two other recognized categories (classic HAPE and re-entry HAPE) typically happen in response to a change in altitude.

The article continues with figures illustrating how ascending too quickly or too much can dramatically increase risk: “HAPE generally occurs above 2500 meters (8000 feet) and is uncommon below 3000 meters (10,000 feet) … The risk depends upon individual susceptibility, altitude attained, rate of ascent, and time spent at high altitude. in those without a history of HAPE, the incidence is 0.2 percent with ascent to 4500 meters (14,800 feet) over four days but 6 percept when ascent occurs over one to two days. In those with a history of HAPE, recurrence is 60 percent with an ascent to 4500 meters over two days. At 5500 meters (18,000 feet), the incidence ranges between 2 and 15 percent, again depending upon rate of ascent.”

Dr. Chris discusses her experience treating her pediatric patients at high altitude in more depth in an interview with pediatric emergency medicine physician Dr. Alison Brent from Colorado Children’s Hospital for the podcast Charting Pediatrics.

Dr. Gallagher and Dr. Hackett’s article is available on UpToDate with a subscription.

References

  1. https://www.uptodate.com/contents/high-altitude-pulmonary-edema?source=autocomplete&index=0~1&search=HAPE ↩︎
  2. https://www.aspenhospital.org/people/scott-a-gallagher-md/ ↩︎
  3. https://www.highaltitudedoctor.org/dr-peter-hackett ↩︎
  4. Ebert-Santos, C. High-Altitude Pulmonary Edema in Mountain Community Residents. High Alt Med Biol 2017; 18:278. ↩︎
Acclimation, Altitude Science, Athletic Training, Backpacking, Child Growth & Development, Doc Talk, Exposure, Health, High Altitude, High Altitude Training & Fitness, Medicine, Mountaineering

Interview with Dr. Christine Ebert-Santos on High Altitude Pulmonary Edema

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by Cody Jones, Summit Daily News

“‘The first sign is usually a cough,’ Ebert-Santos said. ‘Followed by shortness of breath with any effort — even just walking — and fatigue. You just want to lie on the couch.’

If left untreated the early warning signs of high altitude pulmonary edema can rapidly progress into having fluid build up in the lungs, which will then lead to a patient’s oxygen saturation levels rapidly decreasing. If the individual does not seek treatment quickly, the condition can be fatal.”

Read the whole article here.

Acclimation, Altitude Science, Doc Talk, Genetics, Health, High Altitude

RED FLAGS AT ALTITUDE: When Your Doctor Tells You Your Labs AreNormal But the Results in the Patient Portal Are Flagged

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It comes as no surprise that living at altitude can take some adjustment. Travelers visiting just for a quick ski trip recognize  immediately, sometimes even at Denver International Airport when first arriving at Colorado’s Mile High City at 5280 feet, that the air is “thinner” than where they might have journeyed from. That thinner air we all feel is due to our altitude living at 9,075 feet (2) here in Frisco, CO. Our bodies can feel the atmospheric changes even if we do not recognize them ourselves. As a point of reference, on the rather extreme side, the “death zone” that comes to mind when thinking of the behemoth Mount Everest, is any elevation of 26,247 feet and above (3), a  zone we might not be as familiar with is the deterioration zone which begins at a mere 15,000 feet (3). In this zone, the symptoms are variable, but  common manifestations are lethargy, weight loss, poor appetite, and irritability (4). Altitude experts identify 8,000 feet as the elevation where  symptoms such as headaches and pulmonary edema are more likely to manifest. The good and bad effects of altitude are proportional to the elevation and variable between individuals. For all of you ‘fourteener’ fanatics out there, including myself, this comes as a reminder that we are closer than we think to detrimental elevation in our atmosphere. With this  frame of reference fresh in our minds, let us take a closer look at how living in at the elevation of Frisco, Colorado at 9000 feet or the neighboring towns can affect our health. 

Mountain residents who have blood tests done commonly see “red flags” next to some lab values. In particular, the complete blood count, commonly referred to as CBC. To most of us, those red flags are an alarming indicator that something must be terribly awry but au contraire,  there is an explanation why we need not worry. For those of us living at altitude, there is a reduced atmospheric pressure, so although the fraction of oxygen in the air is still 21%, the molecules are further apart. Fewer oxygen molecules enter our lungs and bloodstream  delivering less oxygen to our tissues(5). Remember now, we are not living on top of Mount Everest, so we are not in any danger, because our bodies are doing behind-the-scenes work for us! Our bodies are adapting by increasing the amount of red blood cells, which carry oxygen in our blood, throughout our bodies so that every organ is being supplied with the good stuff! This is exactly why athletes come here to train, to get their bodies to produce more red blood cells so they can perform at their absolute best. After three months of life in the mountains, nearly everyone has elevated red blood cells, hemoglobin, hematocrit, and red cell indices such as the MCV, (mean corpuscular volume), MCHC (mean corpuscular hemoglobin content) and MCH (mean corpuscular hemoglobin). A “normal” hemoglobin in a man who lived for years in the mountains was a signal to his doctor that the patient was anemic and in fact turned out to have colon cancer.

A more immediate response to the low oxygen environment at altitude is an increase in respiratory rate. In an interview with physician experts on altitude Dr. Elizabeth Winfield and Dr. Erik Swenson on May 30, 2023, both think this is the reason there is often a red flag for the carbon dioxide (CO2) as low, usually 17 to 19 with 20 being normal.  Because this affects the acid base balance, the serum chloride ( Cl) may be slightly elevated, 107 to 108 instead of 106. Dr. Winfield also explains to her patients that fasting for labs may cause mild dehydration leading to a slightly higher BUN, blood urea nitrogen, a marker of kidney function.  Another physiological response to altitude is a lower plasma volume, which may cause slight elevation in the serum protein and albumin.

So when you doctor calls you and tells you your labs are normal, ask them to drill down and explain the red flags.  If you find out something new, please put a comment on our blog and share with the world! Few health care providers really understand all the changes in the human body living in hypobaric hypoxic (low pressure, low oxygen) environments.

References 

1. Image. https://ichef.bbci.co.uk/news/624/cpsprodpb/960F/production/_83851483_c0249925-red_blood_cells,_illustration-spl.jpg. 

2. Town of Frisco Colorado. (2023). Maps. https://www.friscogov.com/your-government/maps/. 

3. Lankford, H. V. (2021). The death zone: Lessons from history. Wilderness & Environmental Medicine, 32(1), pp. 114-120. https://doi.org/10.1016/j.wem.2020.09.002. 

4. West, J. C. (2013). Case law update. Legal liability in emergency medicine and risk management considerations. Journal of healthcare risk management: the journal of the American Society for Healthcare Risk Management, 33(1), pp. 53-60. 

5. Cabrales, P., Govender, K. and Williams, A.T. (2020), What determines blood viscosity at the highest city in the world?. J Physiol, 598: 3817-3818. https://doi.org/10.1113/JP280206

6. Image. https://cdn.allsummitcounty.com/images/content/5717_13913_Frisco_Colorado_Main_Street_lg.jpg

Acclimation, Altitude Science, Doc Talk, Health, High Altitude

Ileus at Altitude: When Your Gut Blows Up Like a Potato Chip Bag

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Myasthenia Gravis (MG) is a condition caused by the production of antibodies that block acetylcholine receptors. This blockade of neuromuscular signaling results in rapid muscular fatigue and weakness. Increased activity tends to worsen muscular issues which usually resolve with rest. Prominent symptoms of MG include drooping eyelids, double vision — OMG (ocular myasthenia gravis)– difficulty swallowing, slurred speech, and shortness of breath. Generally, muscles in the face and throat are considered to be the most commonly impacted by Myasthenia Gravis. However, this condition can affect any muscle group throughout the body (1). Gastrointestinal (GI) manifestations such as abdominal pain, recurrent vomiting, and constipation have been reported by individuals with MG. A case presenting to the Summit Medical Center located at 9,100 feet illustrates an unusually severe manifestation:

A road covered in tire tracks through white snow passes by a blue and red sign for St. Anthony Summit Medical Center and its emergency room, in front of dark green conifer trees that stand out against a snowy mist that settles over a pine-forested mountain background.
St. Anthony Summit Medical Center on Peak One Drive in Frisco, Summit County, Colorado, at the foot of Peak One of the Ten Mile Range, enshrouded in snowy mist.

A 70 year old woman was brought to the emergency department (ED) with severe abdominal and chest pain, concerned that she had a dissecting aortic aneurysm. She reported three previous episodes of severe  pain in the 2 weeks leading up to the ED visit, all starting in the afternoon, increasing to prostration by 5 pm and resolving with bed rest. Past medical history was significant for myasthenia gravis for which she took azathioprine 100 mg BID (twice daily). Two months previously she had a flare with ptosis and double vision, treated with prednisone 40 mg daily. 

Laboratory tests were normal. Imaging showed distended loops of bowel consistent with ileus. She was treated with pain medication and symptoms resolved.

The patient continued to have episodes once or twice a month, including another ED visit, precipitated by treatment with duoneb, which has  anticholinergic activity, a tonic water drink, and guaifenesin, both antimuscarinic substances that interact with the cholinergic receptors in the viscera.. Taking pyridostigmine, a cholinesterase inhibitor, led to resolution within 2 hours, marked by “sparkly” sensations in her arms and legs and reactivation of bowel sounds with flatus. 

An x-ray of a torso showing marked intestinal distention.
CT scan of patient with intestines diffusely distended with bowel gas.

Until recently, GI symptoms were considered rare in myasthenia gravis. Then a case study in 2001 demonstrated that gastric dysmotility was a common feature among individuals with Myasthenia Gravis (2). Among all the motility dysfunction reported, gastroparesis was found to be a common autonomic feature in MG patients (2). Gastroparesis is the slowing or stopping of movement in the GI tract resulting in delayed gastric emptying. Further research demonstrated that intestinal pseudo-obstruction was considered to be one of the most common GI manifestations of individuals with MG(3,4,5).

In 2007 it was demonstrated that receptors in gut muscles were structurally similar to skeletal muscle receptors, indicating that GI motility could be highly impacted by the presence or lack of acetylcholine (6). Considering that antibody production in Myasthenia Gravis Individuals can decrease acetylcholine binding to receptors, the presence of GI symptoms among other autonomic dysfunction symptoms suggests inadequate treatment which can result in a poor prognosis for these individuals (7). 

What was previously considered a rare symptom within a rare condition, is now being proposed as an early identification tool. Taking into account receptor similarity,  GI symptoms can be used as early indicators of myasthenia gravis, specifically gastrointestinal dysmotility (8). The case study showed that MG developed less than a decade after the initial onset of gastrointestinal dysmotility symptoms (8). There is a clear need to identify GI symptoms earlier in MG individuals. This will allow for better treatment and improved long-term health outcomes for these individuals. 

At altitude, the low barometric pressure causes gaseous distension in normal individuals producing increased flatus (see blog on HAFE). Combined with MG, GI manifestations can be even more severe. Medical providers treating residents of  high altitude communities should consider MG in the differential of patients with abdominal complaints and treat recognized MG patients with anticholinesterase medications to control symptoms. None of this patient’s providers were aware of this manifestation of MG, including the neurologist who specializes in MG, the gastroenterologist who performed an  upper endoscopy and colonoscopy, the ED staff, the radiologist and the primary care provider. Patients with MG and their providers need to be aware of medications that interact with the cholinergic receptors in all parts of the body and screen for these as possible precipitators of symptoms outside the classic description of the disease.

Submitted by Ana Campos, PA-S.

References 

1. (NHS) https://www.nhs.uk/conditions/myasthenia-gravis/ 

2. Vernino S, et al. Myasthenia gravis with autoimmune autonomic neuropathy. Auton Neurosci. 2001;88(3):187–192.

3. Pande R, Leis AA. Myasthenia gravis, thymoma, intestinal pseudo-obstruction, and neuronal nicotinic acetylcholine receptor antibody. Muscle Nerve 1999;22:1600-1602

4. Musthafa CP, Moosa A, Chandrashekharan PA, Nandakumar R, Narayanan AV, Balakrishnan V. Intestinal pseudo-obstruction as initial presentation of thymoma. Indian J Gastroenterol 2006;25:264-265. 

5. Seretis C, Seretis F, Gemenetzis G, Gourgiotis S, Lagoudianakis E, Pappas A, Keramidaris D, Salemis N. Adhesive ileus complicating recurrent intestinal pseudo-obstruction in a patient with myasthenia gravis. Case Rep Gastroenterol. 2012 

6. Mandl, P, Kiss, JP. Role of presynaptic nicotinic acetylcholine receptors in the regulation of gastrointestinal motility. Brain Res Bull. 2007;72:194–200 

7. Putri Aaliyah. Autonomic Dysfunciton. Gastroparesis as autonomic manifestation of myasthenia Gravis: A rare case report. Clinical Neurophysiology. 132: 94-95, 2021 8. Alnajjar, S., Idiaquez Rios, J., Fathi, D., Liu, G., & Bril, V. (2022). Gastrointestinal Dysmotility as the First Manifestation of Myasthenia Gravis. Canadian Journal of Neurological Sciences, 1-2.

8. Alnajjar, S., Idiaquez Rios, J., Fathi, D., Liu, G., & Bril, V. (2022). Gastrointestinal Dysmotility as the First Manifestation of Myasthenia Gravis. Canadian Journal of Neurological Sciences, 1-2.

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Re-Entry HAPE: Leading Cause of Critical Illness in Mountain Teens

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Health care providers and people who live at altitude often believe that living in the mountains protects from altitude related illness. And yes, there are many ways the body acclimatizes over days, weeks, months, and years, as addressed in previous blog entries. However, as a physician who has practiced in high altitude communities for over 20 years, my personal observation that we are still at risk for serious complications was reenforced by a recent publication by Dr. Santiago Ucrós at the Universidad de los Andes School of Medicine in Santa Fe de Bogotá, Colombia. His article, High altitude pulmonary edema in children: a systemic review, was published in the journal Pediatric Pulmonology in August 2022. He included 35 studies reporting 210 cases, ages 0-18 years, from 12 countries.

A chart titled "HAPE in Children" illustrates cases of high altitude pulmonary edema by country.

Consistent with our experience in Colorado, the most common ages were 6-10 years and second most common 11-15 years. I have not seen or read any reports of adults affected. Cases included two deaths, which I have also seen here.

I receive reports on any of my patients seen in urgent or emergency care. Accidents, avalanches, and suicide attempts are what we think of first needing emergency care in the mountains. However, the most common critical condition is Reentry HAPE. This is a form of pulmonary edema that can occur in children who are returning from a trip to lower altitude. Think visiting Grandma during school break.  Dr. Ucrós’ review also confirms that all presentations of HAPE (classic, as in visitors, reentry, and HARPE, resident children with no history of recent travel) are more common in males by a 2.6 to 1 ratio. Analysis of time spent at lower altitude before the episode showed a range of 1.6 to 30 days with a mean of 11.3 days. Mean time between arrival and onset of symptoms for all types of HAPE was 16.7 hours. The minimum altitude change reported in a HAPE case was 520 meters (1700 feet), which is the difference between Frisco, CO (Summit County) and Kremmling, CO (Grand County, the next county over). A new form of HAPE in high altitude residents who travel to higher altitude was designated HL-HAPE in this review.  A case report will be featured in an upcoming blog interview with a Summit County resident who traveled to Mt. Kilimanjaro.

As with all cases of HAPE, the victims develop a cough, sound congested as the fluid builds up in their lungs, have fatigue, exercise intolerance, with rapid onset over hours of exposure to altitude, usually above 8000 ft or 2500m. Oxygen saturations in this paper ranged from 55 to 79%. My patients have been as low at 39% in the emergency room.  Children presenting earlier or with milder cases come to the office with oxygen saturations in the 80’s. An underlying infection such as a cold or influenza is nearly always present and considered a contributing factor. Everyone living or visiting altitude should have an inexpensive pulse oximeter which can measure oxygen on a finger. Access to oxygen and immediate treatment for values under 89 can be life-saving.

The recurrence rate for all types of HAPE is about 20%. Most children never have another episode, but some have multiple. Preventive measures include slower return to altitude, such as a night in Denver, acetazolamide prescription taken two days before and two days after, and using oxygen for 24-48 hours on arrival. Most families learn to anticipate, prevent, or treat early and don’t need to see a health care provider after the first episode.

On January 26, 2023 I met with Dr. Ucrós and other high altitude scientists including Dr. Christina Eichstaedt, genetics expert at the University of Heidelberg in Germany, Dr. Deborah Liptzen, pediatric pulmonologist, and Dr. Dunbar Ivy, pediatric cardiologist, both from the University of Colorado and Children’s Hospital of Colorado, and Jose Antonio Castro-Rodríguez MD, PhD from the Pontifica Universidad Católica in Santiago de Chile.

We discussed possible genetic susceptibility to HAPE and hypoxia in newborns at altitude with plans to conduct studies in Bogotá and Summit County, Colorado.

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Going Home to the Mountains Can Be Dangerous: Re-Entry HAPE (High Altitude Pulmonary Edema)

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Louie was excited to get out on the slopes after spending Thanksgiving with family in Vermont. He got tired early and felt his breathing was harder than usual, leaving early to go home and rest. As a competitive skier he thought that was strange. But he was getting over a cold. He could not have imagined that in 24 hours he would be in the emergency room, fighting for his life.

Louie experienced a dangerous condition, set off by altitude, and inflammation from his “cold”, that caused his lungs to fill with fluid.  His oxygen saturation was 54 % instead of the normal 92, he had been vomiting and feeling very weak and short of breath. His blood tests showed dehydration, hypoxemia and acute kidney injury. His chest x-ray looked like a snowstorm. He was transferred to Children’s Hospital in Denver and admitted to the intensive care unit.

The diagnosis of Re-entry HAPE was confirmed by echocardiogram showing increased pressures in his lungs. He improved rapidly with oxygen and low altitude.

Re-entry HAPE is not rare, affecting several Summit County children every year.  Many do not come to medical attention because after their first episode parents carefully monitor their oxygen and have a concentrator available in their home when they return from travel. 

Medical providers may not be aware of this risk, expecting that children living at altitude are acclimatized. (See previous blog entry on Acclimatization vs. Adaptation, April 17, 2019) Re-entry HAPE seems to occur mostly in children between the ages of 4 and 15. Inflammation, such as a viral respiratory infection, seems to play a role.  Trauma may also predispose a returning resident to Re-entry HAPE, as described in our blog post from February 5, 2018, Re-entry HAPE in High Altitude Residents.

Louie agreed to share his story on our blog to help educate medical personnel and families living in the mountains about this dangerous condition. Further research will help define who is at risk.  The University of Heidelberg recently published an article on the genetics of pulmonary hypertension (HARPE is the New HAPE) and is interested in testing families here who have had more than one person affected by HAPE.