Category Archives: Acclimation

What happens to your body’s physiology when you move between low and high elevations?

RSV: The Higher the Altitude, the Higher the Risk

Respiratory syncytial virus, RSV, is a common disease that predominantly affects infants and children throughout the world. Symptoms include mild fever, runny nose, coughing, and wheezing (CDC, 2021 and is the leading cause of bronchiolitis and pneumonia in children under the age of 1 in the United States. Because of this high risk of lower respiratory symptoms RSV is also the leading cause of hospitalizations within this age group (Sanofi Pasteur, 2021). Testing for RSV is quick and easy. Children under the age of 5 can be tested for RSV with a nasal swab and rRT-PCR test, similar to COVID-19 home tests (CDC, 2021) available at clinics and emergency rooms. . Unfortunately, preventing the spread of RSV and keeping these hospitalization rates to a minimum is more difficult at higher elevations.

One of our patients during admission after being diagnosed with RSV earlier in the day.

Higher elevations affect the body in many ways. The human body physiologically adapts within seconds of exposure to higher altitudes. Respiratory rate increases in order to compensate for the lower amount of oxygen circulating within the body (Scott, 2018). Within days to weeks, the body begins to acclimate to the higher altitude and this hypoxic state by maintaining this increased ventilation rate and increasing the amount of hemoglobin in the body (Scott, 2018). Due to the combination of effects on ventilation and oxygenation, managing respiratory infections like RSV becomes more difficult.

  The correlation between rates of RSV and higher altitudes has been studied more in recent years. It is hypothesized that the physiological changes that the body undergoes at higher altitude predisposes children to respiratory illnesses including RSV (Shi et al., 2015). In one study done in Colorado, the incidence of RSV within the population was higher than those at moderate and lower elevation areas. The rates of hospitalization increased 25% with children under the age of 1 and up to 53% with children between 1 and 4 (Choudhuri et al, 2006). Data shows that as altitude increases, the incidence of RSV increases, with elevations over 2500m considered as a modest predictor of RSV-related hospitalizations. The incidence of morbidity associated with RSV increases with higher elevation as well (Wu et al., 2015). This increased morbidity is attributed to the thick secretions that is caused by the virus. Since infants breathe through their nose until age 3, this collection of mucus causes respiratory issues including pauses in breathing with cyanosis called apnea. With studies showing the increased incidence, hospitalizations, and morbidity of RSV at higher altitudes, diagnoses of RSV should not be downplayed in children living at high altitudes.

Photo of the same patient as above on home oxygen after being discharged from the hospital.

It is important for providers and parents to be aware of the higher risk for more severe disease progression faced by children who reside at higher altitudes. Parents should recognize the symptoms of RSV and practice proper handwashing techniques to prevent the further spread of this disease within the community. Health care providers within these high-altitude areas should consider additional interventions and treatments such as home oxygen or nasal suctioning which may be beneficial to preventing hospitalizations due to RSV. Dr. Chris advises parents with older children in daycare or preschool to consider keeping them home during RSV season (November-April) when they have a new baby in the house. Although it is imperative to properly diagnose and treat RSV to avoid hospitalizations, obtaining a chest x-ray and treating with medications like albuterol or steroids is unnecessary. Ultimately, although RSV is a benign disease to most, in areas of higher elevation, it must be taken seriously order to prevent unfavorable outcomes.

References

Centers for Disease Control and Prevention. (2021, September 24). Symptoms and care of RSV (respiratory syncytial virus). Centers for Disease Control and Prevention. Retrieved April 28, 2022, from https://www.cdc.gov/rsv/about/symptoms.html 

Choudhuri, J. A., Ogden, L. G., Ruttenber, A. J., Thomas, D. S., Todd, J. K., & Simoes, E. A. (2006). Effect of altitude on hospitalizations for respiratory syncytial virus infection. Pediatrics, 117(2), 349–356. https://doi.org/10.1542/peds.2004-2795

Sanofi Pasteur. (2021). Rethink RSV. Retrieved April 28, 2022, from https://www.rethinkrsv.com/

Scott, B. (2018, June 13). How does altitude affect the body? Murdoch University. Retrieved April 28, 2022, from https://www.murdoch.edu.au/news/articles/opinion-how-does-altitude-affect-the-body#:~:text=Many%20people%20who%20ascend%20to,lethargy%2C%20dizziness%20and%20disturbed%20sleep 

 Shi, T., Balsells, E., Wastnedge, E., Singleton, R., Rasmussen, Z. A., Zar, H. J., Rath, B. A., Madhi, S. A., Campbell, S., Vaccari, L. C., Bulkow, L. R., Thomas, E. D., Barnett, W., Hoppe, C., Campbell, H., & Nair, H. (2015). Risk factors for respiratory syncytial virus associated with acute lower respiratory infection in children under five years: Systematic review and meta-analysis. Journal of iglobal health, 5(2), 020416. https://doi.org/10.7189/jogh.05.020416

Wu, A., Budge, P. J., Williams, J., Griffin, M. R., Edwards, K. M., Johnson, M., Zhu, Y., Hartinger, S., Verastegui, H., Gil, A. I., Lanata, C. F., & Grijalva, C. G. (2015). Incidence and Risk Factors for Respiratory Syncytial Virus and Human Metapneumovirus Infections among Children in the Remote Highlands of Peru. PloS one, 10(6), e0130233. https://doi.org/10.1371/journal.pone.0130233

Claire Marasigan is a 2nd year PA student currently studying at Midwestern University in Glendale, Arizona. Claire has lived her entire life in Arizona and went to Grand Canyon University for her undergraduate degree in Biology. Prior to PA school, she was a medical scribe trainer at St. Joseph’s Hospital in Phoenix. In her free time, she loves to cook, try new restaurants with friends, and play with her dog, Koji. 

Kids Living at Altitude are Built Different: How Phenotypic Variations in Pediatric Patients Born at Altitude Help Them Compensate for Their Hypoxic Environment

One of the phenomena I experienced while caring for pediatric patients in Summit County was the image of a [1] child with an oxygen saturation of 83% who wasn’t in any respiratory distress. This got me thinking: do adaptations in children exposed to chronic hypoxia at altitude prepare them to encounter an episode of acute hypoxia?

It turns out this phenomenon has been studied previously. Children permanently residing at high altitudes exhibit phenotypic variations to help them adapt to their chronically hypoxic environment. According to de Meer, K., et al., for those children living at altitudes greater than 3000m above sea level since gametogenesis, the opportunities for phenotypic plasticity are particularly excellent.

These changes in phenotypic expression have led to both theorized and proven physiologic differences in oxygen uptake, transport, systemic circulation, and consumption, allowing them to overcome the effects of chronic high-altitude hypoxia.

The lower partial pressure of oxygen causes high-altitude hypoxia to those who are visiting from lower altitudes. With less oxygen in the air, increased respiratory effort would be required to maintain the same oxygen levels as those children living at sea level. However, children living at altitude have physiologic increases in ventilation, lung compliance, and pulmonary diffusion, which help negate the need for augmented respiratory effort.

To conserve respiratory rate, increases in lung compliance and tidal volume have been observed in children living at altitude. In one study by Mortola, J. P., et al., lung compliance and tidal volume remained increased even while participants were on 100% supplemental oxygen.      This suggests that this is a permanent physiological adaptation in kids living at altitude.2

Additionally, children living at altitude are more efficient at delivering oxygen to their tissues. An increase in pulmonary diffusion capacity facilitates this improved efficiency. Pulmonary diffusion capacity is determined by the surface area available for diffusion. Assuming all other anatomic variables are the same in highlanders and lowlanders[2] , this increased capacity can only be explained by an increase in the number and size of alveoli.1 To study this possibility, researchers compared the lung volumes and chest dimensions of children exposed to chronic hypoxia at altitude since birth to those of children living at sea level and found that lung volumes and chest dimensions of children residing at altitude indeed were greater.

Despite this opportunity for increased oxygen uptake by the lungs of children living at altitude, the partial pressure of oxygen in their blood is still substantially lower. This decrease in arterial blood oxygen concentration that is associated with hypoxia encourages the kidneys to release erythropoietin, which subsequently stimulates the production of erythrocytes contributing to an increased erythrocyte and hemoglobin concentration in children living at altitude. Elevated hemoglobin concentration leads to a relative increase in arterial oxygen saturation, which compensates for the lower availability of oxygen at altitude.1

Despite the witnessed phenomenon of the ability of children living at altitude to adapt to acute hypoxia, it is still debated whether chronic hypoxemia in this population results in decreased oxygen consumption. New research has concluded that previously observed decreases in oxygen metabolism in newborns at altitude are reactions to acute stress and hypoxia and should not be considered an effect of chronic exposure to hypoxia.1 In other words, the ability of children living at altitude to decrease ventilation during an episode of acute hypoxia is due to a decrease in tissue metabolism only during that event of respiratory stress.

Like most things in life, these advantages do not come without consequences. Humans exposed to chronic hypoxia are prone to pulmonary hypertension; in fact, phenotypic, physiological changes in tidal volume and lung diffusion that improve oxygen uptake contribute to pulmonary hypertension. However, unlike children who develop pulmonary hypertension unrelated to altitude, highland children often present with a less severe clinical picture and fewer irreversible complications.1

Children born and residing at altitude offer a window into a world of medical phenomena that are little understood. The more we know about the physiological differences in this population, the better we can serve them as clinicians.

References

  1. de Meer, K., et al. “Physical Adaptation of Children to Life at High Altitude.” European Journal of Pediatrics, vol. 154, no. 4, Apr. 1995, pp. 263–72. Springer Link, https://doi.org/10.1007/BF01957359.
  2. Mortola, J. P., et al. “Compliance of the Respiratory System in Infants Born at High Altitude.” The American Review of Respiratory Disease, vol. 142, no. 1, July 1990, pp. 43–48. PubMed, https://doi.org/10.1164/ajrccm/142.1.43.

Lauren Thompson is a second-year Physician Assistant Student at Drexel University in Philadelphia. She is here all the way from sunny sea level, Florida, where she got her degree in Psychology with a minor in Biology from Florida State University. She is currently completing her clinical rotation, which has taken her all over the country with her feline and canine companions, Duke and Remi. Before PA school, Lauren worked as a Certified Nursing Assistant at a local hospital and a Medical Assistant at a pediatric specialty clinic. Outside of medicine, Lauren enjoys traveling, spending time with her animals, singing karaoke, playing disc golf, and taking in all of what mother nature has to offer, whether it’s hiking, skiing, diving, or enjoying the beach.

Sleep at High Altitude

Have you thought of what it would be like living in the mountains year-round? Medical professionals find it is important to look at what living at high elevations can do to the human body. One activity heavily affected is sleep. As mentioned in previous blog posts, visitors often have trouble falling asleep, staying asleep, and feeling rested in the morning. A recent study published in Physiological Reports measured the effects of sleeping patterns at high elevation. The participants experienced a simulated elevation inside a hyperbaric chamber. This mimicked sleeping at elevations of 3000 meters (9,842 feet) and 4050 meters (13,287 ft) for one night and then sleeping at sea level for several nights to establish a baseline for the research participants. Participants exercised for 3 hours in the hyperbaric chamber allowing researchers to observe how the lower oxygen concentrations affected their ability to perform strenuous tasks. The group that slept in a simulated 4050 meter environment had an increased heart rate that was 28% higher and an oxygen saturation 15% lower than the 3000 meter participants. When comparing sleep itself, the group at 4050 meters had 50% more awakening events throughout each night. This goes along with previous research on this blog that states that people who sleep at high altitude complain of insomnia and frequent awakening when first arriving at high elevation.

These numbers increase even more dramatically when compared to participants at sea level. Related symptoms reported during this study showed the incidence of acute mountain sickness occurred in 10% of the participants at a simulated 3000 meters, increasing to 90% at 4050 meters. As mentioned, the average heart rate increases and oxygen saturation decreases as the elevation increases. The baseline heart rate at sea level was 62 beats per minute, increasing to 80 at 3000 meters and 93 at 4050 meters. Ideally health care providers aim to oxygenate vital organs by keeping the oxygen saturation level between 92-100%. The lower the oxygen level the harder it is to keep organs properly profused. Age, health status, and place of residence are taken into consideration when examining study reports. Oxygen saturation at sea level was 98% decreasing to 92% at 3000 meters and 84% at 4050 meters.

As mentioned in a previous post by Dr. Neale Lange, sleeping at high altitudes can be hard due to the frequent awakenings and nocturnal hypoxia caused by the low oxygen levels at higher elevation. This study reiterates these findings with the results of the average oxygen saturation at 3000 meters being around 92%. Dr. Lange also found that sleep apnea was often more prominent and had more negative effects on the human body in environments that were lower in oxygen. This study agrees with that statement finding that people with sleep apnea had twice the hourly awakenings compared to those at higher elevation that did not have sleep apnea. Dr. Lange also pointed out that the contribution of hypobaric atmosphere to symptoms at altitude as opposed to pure hypoxemia is unknown. Frisco, Colorado is at an elevation of 2800 meters. Ongoing research at Ebert Family Clinic including residents and visitors along with laboratory studies such as this one can guide decisions about interventions and treatment to improve sleep and help us enjoy our time in the mountains.

References

  1. Figueiredo PS, Sils IV, Staab JE, Fulco CS, Muza SR, Beidleman BA. Acute mountain sickness and sleep disturbances differentially influence cognition and mood during rapid ascent to 3000 and 4050 m. Physiological Reports. 2022;10(3). doi:10.14814/phy2.15175
  2. Blog post: HOW DO YOU DEFINE A GOOD NIGHT’S SLEEP?:AN INTRODUCTION TO THE SLEEPIMAGE RING, AN INTERVIEW WITH DR. NEALE LANGE

Casey Weibel is a 2nd year student at Drexel University, born and raised in Pittsburgh, Pennsylvania. He went to Gannon University for his undergrad and got a degree in biology.  Before PA school, Casey was an EMT.  He enjoys hiking and kayaking and is a big sports fan. 

Dad, put your clothes on! Unique presentations of altitude illness, a Discussion with EMS director Thomas Resignolo

After his father-in-law arrived in the mountains, Thomas noticed later that night he seemed intoxicated despite not seeing him drink alcohol. Thomas woke up the next morning to see him reading the paper in nothing but black socks and a black tie. Thomas knew right away he wasn’t drunk, he had high altitude cerebral edema (HACE). HACE is a complication of acute mountain sickness (AMS). HACE can occur from increased pressure in the blood vessels in the brain, leading to fluid leakage and swelling (edema). This increased vessel pressure can result from the lower atmospheric pressure at high altitude1. Breathing in lower atmospheric pressure gives you less oxygen molecules per breath. Thomas estimates that EMS in Summit County see one case of HACE a year. EMS look for two hallmark signs of HACE, altered mentation and ataxia. When EMS arrive to a patient with altered mentation, they have the patient walk heel-to-toe to evaluate for ataxia. If ataxia is present, immediate descent is necessary. Rapid descent is necessary because HACE can progress rapidly. Years ago, Thomas had a patient walk into the emergency department and die within 10 minutes after arrival. Unlike high altitude pulmonary edema (HAPE), descent is the only cure for HACE.

HAPE is a more common complication of AMS. Similar to HACE, edema occurs from the high pressure inside pulmonary blood vessels pushing fluid into the lungs. The high pressure is caused by a rapid vasoconstriction response to hypoxia or low oxygen partial pressures. Luckily, HAPE has a simple treatment, oxygen. Therefore, visitors with HAPE do not need to descend to lower altitude as with HACE. HAPE is much harder to recognize than HACE and EMS is well trained in how to recognize it. Often, headache is the only symptom2. Thomas explains the HAPE protocol for EMS: In the first 20 seconds of arriving, an oxygen saturation is obtained; they obtain vitals in the next two minutes and then start high flow oxygen if the saturation is below 89%; they then listen to the lungs for signs of fluid. EMS does not treat HACE or HAPE with any medications since descent and oxygen are the effective treatments.

So, who is prone to AMS?

Unfortunately, better physical fitness does not protect you from AMS. Thomas reports that athletes with resting heart rates of 40 or below have a difficult time acclimating. Younger age also doesn’t mean easier acclimation. According to Thomas, the best age for acclimation is late 30s/early 40s. Surprisingly, previous hypoxia can help acclimation to high altitude. For example, Thomas reports that smokers have an easier time acclimating because their body is used to having the vasoconstriction response to hypoxia and breathing faster and deeper to get adequate oxygen intake.

But don’t worry, your conditioning wasn’t for nothing. A healthy diet and regular exercise prevents heart disease. Thomas estimates there are about 12 acute MI’s on the ski hill each year. These patients usually have to be transported to Denver for a stent to be placed. Exacerbation of coronary artery disease (CAD) is so common that EMS refers to altitude travel as the “altitude stress test.” This mimics a cardiac stress test in those with CAD, producing chest pain that wasn’t present at lower altitude.

Those with sickle cell disease are at risk of developing sickle cell crisis when traveling to high altitude. The lower atmospheric pressure allows the normal red blood cells to lose their integrity and become sickle. Thomas reports that EMS encounters this every couple months in patients (usually of Mediterranean descent) that present with diffuse abdominal pain with no obvious cause. This pain results from the sickle cells aggregating together and causing an occlusion. The occlusion leads to tissue hypoxia and ischemia3. These patients are transported to the hospital for treatment.

How can mountain tourists avoid AMS?

Thomas’s first recommendation is to take a staggered stop for one night at an elevation of 5,000-6,000ft, like Denver. When arriving to altitude, take it easy the first 3 days: don’t drink alcohol and do light activity. Save the long hike for the end of the trip. Also avoid substances that blunt the respiratory system like alcohol, opioids, benzodiazepines, etc. Prepare by hydrating the week before and keep drinking plenty of water while on the trip. If you have had a previous episode of AMS, you can speak to your medical provider about prophylactic medication to take before arriving at high altitude.

References

1. Hackett PH, Dietz TE. Travel Medicine. Fourth ed. Edinburgh: Elsevier; 2019. https://www-clinicalkey-com.ezproxy2.library.drexel.edu/#!/content/book/3-s2.0-B9780323546966000422?scrollTo=%23hl0000521. Accessed November 22, 2021.

2. Schafermeyer, R. W. DynaMed. Acute Altitude Illnesses. EBSCO Information Services. https://www.dynamed.com/condition/acute-altitude-illnesses. Accessed November 19, 2021.

3. Sheehan VA, Gordeuk VR, Kutlar A. Disorders of Hemoglobin Structure: Sickle Cell Anemia and Related Abnormalities. In: Kaushansky K, Prchal JT, Burns LJ, Lichtman MA, Levi M, Linch DC. eds. Williams Hematology, 10e. McGraw Hill; 2021. Accessed November 23, 2021. https://accessmedicine-mhmedical-com.ezproxy2.library.drexel.edu/content.aspx?bookid=2962&sectionid=252529206

Samantha Fredrickson is currently a student in Drexel University’s Physician Assistant program.

How do you define a good night’s sleep? : An Introduction to the SleepImage Ring, An Interview with Dr. Neale Lange

Dr. Neale Lange is a leader in sleep medicine who started his medical training in South Africa and now practices Pulmonary and Sleep Medicine for UCHealth in Denver.

Sleep plays a crucial role in cognitive behavior and physical well-being but is often times taken for granted. As Dr. Neale Lange puts it, many people have been taught or trained to devalue sleep in an effort to maximize the time awake to study, get caught up on work, or complete other tasks1. However, research over the years has demonstrated that the toll sleep deprivation plays on the body is significant. Sleep deprivation can lead to impairment in memory, cognition, and emotion, and can lead to chronic medical conditions such as diabetes, heart disease and cancer2. It is also thought that sleep deprivation and hypoxemia are associated with white matter disease in the brain and deep slow wave sleep, is what fixes it4.

Furthermore, Dr. Lange states that sleeping at altitude carries its own risks. Sleeping at altitude, where there is less oxygen in the air, can cause overall poor sleep quality, increased awakenings, frequent arousals, marked nocturnal hypoxia and periodic breathing.. Additionally, sleeping at altitude can negatively impact our sleep architecture, increasing the amount of light sleep and decreasing the amount of deep slow-wave and REM sleep which plays a key role in memory creation, retention and emotional control and personal behavior3.

In hopes to defining a person’s sleep at altitude, Dr. Lange started a sleep lab in Summit County at St. Anthony Summit Hospital, which, as he put it, “opened a can of worms” when he saw how sick and complicated patients sleep apnea cases were. Time and time again, he saw that when patients who were struggling with sleep apnea were given 2L of supplemental oxygen by nasal cannula, the apnea improved. Additionally, those patients with sleep apnea who descended around 4,000 ft to Denver have improved saturations but may still have sleep apnea. His facility study included baseline tests at two hours without oxygen and then two hours with oxygen while a person slept. He found that although the apnea improved in many, improvements in sleep itself did not always follow.

This left him with the question of: How do we measure “good sleep?” Well, as he states, it is not that simple. Though the obvious answer may be to turn to medications to determine good sleep, this can be misleading. Medications have an amnestic effect on people because when they wake up in the morning, if their memory is blank, they feel that they have had a good night’s rest. But in reality, this is subjective. The true data collected during sleep is objective, so to answer his question of measuring sleep, he turns to a tool of cardiopulmonary coupling (CPC). This tool, called a SleepImage Ring, looks similar to an Apple Watch and is worn around a patient’s finger throughout the night. Using Bluetooth technology, data is collected and transferred through a smartphone for analysis, providing the patient with a vast amount of data about their sleep.

The SleepImage System is the only FDA approved medical grade technology with the simplicity of a consumer device on the market for use in both children and adults. It is intended for use by a healthcare professional to establish a patient’s sleep quality and aid in evaluation and clinical diagnosis of sleep disorders and sleep disordered breathing, or SDB. It uses CPC technology which is “based on calculations and spectral analysis of cardiovascular- and respiratory data” collected during sleep using continuous “normal sinus rhythm ECG- or PLETH (Plethysmogram from a PPG sensor) signal as the only input requirement.” The output metrics from the SleepImage System include “sleep duration (SD), total sleep time (TST), wake after sleep onset (WASO) and sleep quality (SQI) and sleep disordered breathing (SDB) related output metrics that include an Oxygen Desaturation Index (ODI), an Apnea Hypopnea Index (sAHI), a Respiratory Disturbance Index (sRDI), Central Sleep Apnea Index and the Sleep Apnea Indicator (SAI) that is derived from Cyclic Variation in Heart Rate (CVHR)6. With a PLETH signal including saturations, the SDB data conforms with the American Academy of Sleep Medicine AHI scoring and severity definitions.” Additionally, we can determine how long a patient spends in various sleep stages, including stable, unstable and REM sleep, determine apnea events, and autonomic nervous system activity. The data is generated and presented on the SleepImage Quality Report (shown below). The ring and report are designed as such where you can do individualized, precise sleep medicine. It is true when Dr. Lange says “the devil is in the details” referring to the vast amount of information that can be analyzed from this device during one night of sleep.

Currently, the gold standard to monitoring and diagnosing sleep disorders is polysomnography, also known as a sleep study, which records certain body functions as you sleep to determine brain activity, oxygen, heart rate, breathing, as well as eye and leg movements5. It can detect types of sleep apnea; however, this comprehensive test is typically done during an overnight stay in a hospital or other sleep center, which presents a disadvantage. The disadvantage to polysomnography is that it takes people out of their natural sleeping environment, is costly, and time consuming, which deter a large portion of people from partaking in sleep studies.

Dr. Neale Lange explains that this device can change the way we look at our sleep and may provide better insight into a person’s sleep on a greater scale due to the ease of wearing the device over multiple nights, compared to spending one night in a sleep lab for a study. A study done on 65,000 users indicated that there is added benefit to multi-night testing as compared to single night testing. Testing for sleep apnea on only one night has been shown to vary from night to night, indicating that single night testing potentially misclassifies 20% of people7. This device provides the ease of multi-night testing for patients, which is a significant advantage and increases accurate diagnosis of sleep disordered breathing. To Dr. Lange, “it is about individualized patient care” and evaluating “the person sitting in front of [him]” which makes this device so valuable. Dr. Lange states that, “living at altitude is a particular challenge, and if people are thinking ahead,” instead of wondering, “how long do I want to live at altitude,” a better question would be, “how can I invest in brain wellness.”

In summary, sleep deprivation, especially at altitude, is an important focus that people should not overlook. At Ebert Family Clinic in Frisco, one of the most important questions asked is, “how did you (or your child) sleep last night?” Now, with the SleepImage Ring, we can objectively evaluate our patient’s sleep which can aid in the diagnosis and management of various conditions.

References

  1. South African Dental Association. (2021, November 25). The sleep disorder spectrum: Mouth breathing to Osa – Dr Neale Lange (WEB126). YouTube. Retrieved December 5, 2021, from https://www.youtube.com/watch?v=agZruGNfFNI
  2. Irish, L. A., Kline, C. E., Gunn, H. E., Buysse, D. J., & Hall, M. H. (2015). The role of sleep hygiene in promoting public health: A review of empirical evidence. Sleep medicine reviews, 22, 23–36. https://doi.org/10.1016/j.smrv.2014.10.001
  3. Wickramasinghe, H., & Anholm, J. D. (1999). Sleep and Breathing at High Altitude. Sleep & breathing = Schlaf & Atmung, 3(3), 89–102. https://doi.org/10.1007/s11325-999-0089-1
  4. Voldsbekk, I., Groote, I., Zak, N., Roelfs, D., Geier, O., Due-Tønnessen, P., Løkken, L. L., Strømstad, M., Blakstvedt, T. Y., Kuiper, Y. S., Elvsåshagen, T., Westlye, L. T., Bjørnerud, A., & Maximov, I. I. (2021). Sleep and sleep deprivation differentially alter white matter microstructure: A mixed model design utilizing advanced diffusion modelling. NeuroImage, 226, 117540. https://doi.org/10.1016/j.neuroimage.2020.117540
  5. Mayo Foundation for Medical Education and Research. (2020, December 1). Polysomnography (Sleep Study). Mayo Clinic. Retrieved December 25, 2021, from https://www.mayoclinic.org/tests-procedures/polysomnography/about/pac-20394877#:~:text=Polysomnography%2C%20also%20called%20a%20sleep,leg%20movements%20during%20the%20study.
  6. MyCardio LLC. (2021, November 24). Introduction to sleepimage®. Retrieved December 10, 2021, from https://sleepimage.com/wp-content/uploads/Introduction-to-SleepImage.pdf
  7. Lechat, B., Naik, G., Reynolds, A., Aishah, A., Scott, H., Loffler, K. A., Vakulin, A., Escourrou, P., McEvoy, R. D., Adams, R. J., Catcheside, P. G., & Eckert, D. J. (2021). Multi-night Prevalence, Variability, and Diagnostic Misclassification of Obstructive Sleep Apnea. American journal of respiratory and critical care medicine, 10.1164/rccm.202107-1761OC. Advance online publication. https://doi.org/10.1164/rccm.202107-1761OC

Catherine Atkinson is a second-year Physician Assistant student at Red Rocks Community College in Arvada, CO. She was born and raised in Colorado where she has lived her entire life. She received her undergraduate degree in integrative physiology from The University of Colorado- Boulder. Prior to PA school, she was an ophthalmic technician at Colorado Retina Associates. In her free time, she loves cooking, skiing, playing golf and spending time with her family and friends. 

How to Stay Healthy During Your Holidays at High Altitude

Acute Altitude Illness affects about 7.4% of travelers to mountain resort areas, including Frisco, Colorado which sits at an altitude of about 2800 meters. Dr. Kendrick Adnan, MD, MSPH is an emergency medicine physician associated with Vail Health. Dr. Adnan often sees visitors to Vail and other popular ski and vacation areas in Summit County that are experiencing Acute Altitude Illness. I sat down with Dr. Adnan, and we discussed the treatment of Acute Altitude Illness as well as signs, symptoms, risk factors, and prevention of Acute Altitude Illness.

What causes Acute Altitude Illness?

  • Acute Altitude Illness develops when the body responds to hypoxia, a low level of oxygen in the blood. Areas of high altitude have a lower concentration of oxygen in the air than lower altitudes, which makes your body work harder to put oxygen in your blood. Your body responds to the lower oxygen concentration by increasing how often and how deeply you breathe. This causes a decrease in carbon dioxide and increase in tpH in the blood. Your heart, lungs, blood vessels, and kidneys all respond to the low pH in your blood, which can cause the signs and symptoms of Acute Altitude Illness.
  • Some people will experience severe forms of Acute Altitude Illness called High-Altitude Pulmonary Edema or High-Altitude Cerebral Edema. These are life-threatening conditions that can cause death in both adults and children if not treated promptly by a medical professional.

What are the signs and symptoms of Acute Altitude Illness in adults?

  • Headache
  • Nausea
  • Vomiting
  • Decreased appetite
  • Fatigue
  • Shortness of breath on exertion
  • Decreased exercise tolerance
  • Chest tightness
  • Hypoxia

What are the signs and symptoms of Acute Altitude Illness in children?

  • Fussiness
  • Poor feeding
  • Pale or blue-tinged skin
  • Sleeping too much or too little

What is the treatment for Acute Altitude Illness (AAI)?

The best treatment for AAI is supplemental oxygen through a nasal cannula and descent to a lower elevation. You will need to visit a healthcare provider, clinic, or hospital to get supplemental oxygen if your oxygen level drops below 89%. Visitors to high-altitude areas may be hesitant to abandon their vacation plans in order to descend to a lower altitude. A healthcare provider may be able to prescribe medications to help you recover from AAI. However, if your low oxygen level does not improve with supplemental oxygen and medication, it is important to descend to an area of lower altitude.

Studies show that acetazolamide, dexamethasone, and tadalafil are medications that can potentially treat Acute Altitude Illness and/or High-Altitude Pulmonary Edema. A healthcare provider may prescribe these medications for you if appropriate.

What increases the chance that I will experience Acute Altitude Illness?

  • Traveling by airplane from low altitude to high altitude.
  • Being a resident of low altitude
  • Past episode of Acute Altitude Illness
  • Physical exertion at high altitude, especially in colder temperatures

What can be done to prevent Acute Altitude Illness and High-Altitude Pulmonary Edema?

  • A slower ascent will decrease your risk of AAI. Dr. Adnan recommends spending the night in Denver after air travel if you are planning to visit a high-altitude area.
  • Avoid strenuous exercise like skiing, hiking, and mountain biking for 48-72 hours after arrival to a high-altitude area.
  • Buy a pulse oximeter to check your oxygen level. A level above 89% is normal at high-altitude and does not require treatment.
  • Ask your healthcare provider about taking Diamox (acetazolamide) for 2-3 days before you arrive at a high-altitude destination. You will need a prescription for this medication.
  • Avoid medications that decrease your respiratory rate like opiates, sleeping medications, benzodiazepines, and barbiturates.

References

Schafermeyer, R. W. DynaMed. Acute Altitude Illnesses. EBSCO Information Services. https://www.dynamed.com/condition/acute-altitude-illnesses. Accessed November 19, 2021. Simancas-Racines D, Arevalo-Rodriguez I, Osorio D, Franco JVA, Xu Y, Hidalgo R. Interventions for treating acute high altitude illness. Cochrane Database of Systematic Reviews 2018, Issue 6. Art. No.: CD009567. DOI: 10.1002/14651858.CD009567.pub2. Accessed 03 November 2021.

Sasha Scott is a physician assistant student at Drexel University in Philadelphia, PA. She is originally from Indianapolis, IN and attended Purdue University for undergrad. Sasha enjoys running, cross stitching, cooking, and exploring Philadelphia when she is not studying!

Wound Healing at High Altitude: Hyperbaric Therapy, A Patient’s firsthand experience with post-surgical wound healing in Summit County

The nuances of wound healing at high altitude is a topic that has already been explored on this platform (see Eric Meiklejohn’s “Wound Care at Altitude”). Identifying the impact that impaired oxygen delivery can have on healing time, tissue regeneration, and infection rates offers great insight into the roles health care providers can assume to support our high-altitude patients. For this interview, I was able to speak directly with  a Summit County resident who had firsthand experience with these processes.

I’ve heard a bit about your experiences with wound healing at high altitudes I will ask some preliminary questions,. This entire experience was more of a marathon than a sprint. How long have you been living at this altitude, and how old were you at the time of your procedure? I’d lived at high altitude for over twenty-six years before I was diagnosed with breast cancer. I was Fifty-three when I had my surgery. I was in great shape, exercising regularly, and eating really well.

Tell me about your procedure: Well, the initial procedure was in January 2018 down in Denver. I had a bilateral mastectomy done to remove the cancerous tissue, and bilateral expanders were inserted during that surgery so that down the line I could have implants placed. Within the first week we started noticing some necrotic changes to my incisions, and that they were not healing well. The expanders were inflated with air, and it was thought that my traveling back to high altitude from Denver could have increased the pressure inside them.  By the end of week one I went back in to see my doctor, who deflated my expanders pretty significantly.

Have you ever been diagnosed with a medical condition that could affect wound healing, such as Diabetes or Hypertension? No. Breast Cancer was my first real medical diagnosis.

Had you ever had surgery while living at this altitude before? And if so, what was the outcome? Yes, I’d had surgery for an umbilical hernia and that went very well. No complications at all, everything healed just fine. I’d also had tendon damage in my right hand after a fall, and I recovered really well after that surgery at this same altitude.

Regarding healing after your mastectomies, describe the anticipated wound healing time and wound care directions. The time estimate for  recovery was four weeks. I was to rest for two weeks, increase activity slightly for the second two weeks with minimal physical therapy, then by the end of that fourth week the projection was that I would be mostly recovered. I was given strict precautions against heavy lifting, restricting arm movements, and not driving. For wound care I was doing daily dressing changes, not submerging the area in water, and applying Silvadene cream twice daily.

Following the removal of the expanders, what was the rest of the healing process like? Over the next two months I cared for my wounds at home. They were open and oozing, and over time the daily dressing changes and medication applications became quite taxing, both physically and emotionally. It took a lot out of me, and really interfered with my day-to-day life…not to mention the pain. On March 9th, 2018 I underwent an incision revision and resection procedure for the necrotic tissue. At that point my breast tissue had manifested itself as far as which parts were healthy and which would die, so they went in and resected the areas that were not viable. On the left side I lost most of the top surface of the breast, including the entire nipple area. Two weeks after that, I had a [chemo therapy] port placed in my arm  so I could begin treatments, but that incision also had a difficult time healing. That eventually led to a one month delay in my chemo therapy.

In March and April the incisions on the right breast eventually healed, but because of all the tissue loss and necrosis on the left side those wounds did not heal. There was still a lot of drainage from that breast and it was mostly still open so I had to keep the bandage on. By early May (after this wound had been open for 5 straight months) my doctor and I started seeing more signs of infection to that breast, so around May 12th of 2018 he called me in for an emergency procedure and I had the expander completely removed from my left breast. I continued chemo and eventually that left side began to heal in the absence of the expander.

During this time, from March until I finished chemo in August, the port site never healed. The whole reason behind having the port placed was so it could heal over and I could go back to a normal life between chemo sessions. But instead I walked around with a bandage for those six months because my port site remained open. I had Her2 positive cancer, so after my six months of chemo I needed to continue taking Herceptin for one additional year. I opted to have the port removed after six months and had an IV placed every three weeks for my treatments. It was very hard on my veins, but I felt I had no choice.

In late August, with the port out and the left expander out, the last of my open wounds really started healing. I started looking at what I could do to help my tissue heal even better- my thought was that when this is all done and I am all well healed I would like to have my expanders placed and inflated again, but I don’t want to have to go backwards through this process. I did all this research, and that’s where I learned about hyperbaric therapy. That changed everything for me.

What did you learn about Hyperbaric therapy, and what was your experience with it? I did a lot of independent research online and came up with two options that I wanted to discuss with my doctor. The first was a topical option for applying oxygen directly to the wound, which was a very complicated and involved process -and the second was hyperbaric therapy.

I discussed this with my oncologist who was very familiar with hyperbaric chamber treatment centers in Denver, and who wrote me a referral to be evaluated at the one in Presbyterian St. Luke’s Medical Center. I was evaluated by their team, showed them all the photos I had been taking throughout this entire ordeal, and they seemed hopeful that they would be able to help me. I really wish I’d gone there sooner.

My plan was to use this to help me recuperate a little bit so I could give the expander one more shot on the left side. After having the left expander placed, the second phase of my plan was to get another course of hyperbaric therapy to aid in recovering from that procedure. It was eventually prescribed and accepted by insurance, who approved 27 hyperbaric sessions following my surgery.

I underwent the left expander placement in February of 2019, observed the same restrictions, and had identical at-home wound care as my initial surgery in January 2018, but with the addition of hyperbaric therapy my results were night and day. The day after surgery I started hyperbaric, and in so much less pain. I was off all pain medications within 48hours. I was able to get out, walk, function in my daily life, and the tissue healed really well. It was amazing! I felt great, had tons of energy, and it was just a completely different experience. It was nothing short of miraculous.

What was your hyperbaric chamber treatment like? It was five days a week in Denver. Being there was for me a huge learning experience. There were people there being treated for diabetic wounds, hearing loss, adjunct therapy for various types of cancer, joint and tendon disease, tissue necrosis, concussions, head trauma, and so many other things. I hadn’t known that this therapy could be utilized in all these different areas.

After your successful left expander placement, how was your transition to breast implants? Months after the left expander was reinserted, I did transition to breast implants (summer 2019) but even then, I insisted on post operative hyperbaric therapy. I was only approved for ten sessions that time, but the results were the same. Rapid healing time, noticeable decrease in pain after starting therapy, and the ability to function throughout the day. Of all the factors that played a role in this process for you, what variable would you most want to adjust? Honestly, I just wish I’d started hyperbaric therapy sooner. If there was a way to get providers who work with high altitude dwellers to recommend hyperbaric treatment as a part of their primary or secondary treatment course, that’s the one thing I would change.Well, I am very happy to know that despite the difficulty you experienced in this process, you are now three years post op, well healed, and satisfied with your results. Thank you again for sharing your story. My pleasure. If my sharing can help someone else find hyperbaric therapy or open them up to alternative methods of treatment sooner so as not to have to experience what I went through in those first few months, then it was all worth it.

Janell Malcolm is a second year Physician Assistant student in the Red Rocks PA Program in Arvada, Co. A Jamaica native, she loves the ocean, tropical fruit, and 100 degree weather. You will likely find her spending her free time with family or reading/re-reading Jane Eyre. Her personal and career goals are geared towards providing adequate medical care to underserved communities. Special interests post graduation: Labor & Delivery, General Surgery.

Effects of High Altitude on Brain Metabolism & Concussion Information

Changes in altitude have many effects on the physiology of the human body and even metabolism. Some people exposed to high altitude develop acute or chronic mountain sickness due to hypoxia with a spectrum of symptoms including neurocognitive decline of performance and impacting brain function. Head truma at altitude is more likely to lead to brain injury or concussion than those at low altitude.

Imaging with PET/CT using FDG-18 has been used to measure brain metabolism in both human and mice subjects. This type of imaging scans the accumulation of a glucose analog in tissue, specifically the brain in this case. This allows determination of which regions have high or low uptake in metabolism in comparison to a brain at baseline at sea level.

In 2017, mice were studied by being placed in a hypobaric chamber to stimulate hypoxic conditions similar at 5000 meters. Conditions were placed to minimize brown adipose tissue uptake and imaging was performed 45 minutes after an estimated 0.5 mCi FDG injection. After appropriate processing, the results showed an increase in glucose metabolism in the cerebellum and medulla of the mice exposed to high altitude conditions compared to those at baseline. Additionally, certain cortical regions had lower metabolism than baseline mice, and lower cardiac uptake as well. It is thought that the brain’s acclimation response to high altitude.

Images courtesy of Jaiswal S., et al. JNM 2017.

Another study using mice as subjects compared brain metabolism at high altitude after a traumatic brain injury (TBI) to determine if hypoxia alters glucose uptake. A total of 32 mice were imaged at sea level (baseline) and again after 12 weeks exposure at 5000m (hypobaric stimulation), and again after a repetitive closed injury. An SUV (standard uptake value) was compared in each set of images to determine a change in glucose metabolism. 

This study showed a significant increase in FDG uptake in the medulla, cerebellum, and pons, and a decreased uptake in the corpus callosum, cortex, midbrain, and thalamus. A TBI affects glucose metabolism in the brain by decreasing cortical uptake in both high altitude and sea level. This study showed that high altitude affects the brain by making it more susceptible to repeated concussions than mice at sea level.

A third study employed PET/CT imaging to assess regional cerebral glucose metabolism rates in six US Marines before and after a rigorous training period from sea level to high altitude conditions ranging from 10,000-20,000 ft. It was thought that other conditions would be relatively stable as the military has similar regimens for their members. After comparing imaging performed at baseline sea level and after two months of high-altitude exposure, it was clear that brain metabolism changed. There was a decrease in glucose metabolism in three frontal regions, left occipital, and right thalamus. Right and left cerebellum showed an increase in glucose uptake and metabolism.

Red and orange coloring signifies greater FDG-18 uptake which correlates to increased glucose metabolism. The post imaging signifies decreased uptake and hypometabolism of certain brain regions as mentioned previously. Image courtesy of Hochachka PW., et al. AJP, 1999.

The data from these three studies clearly show high altitude exposure with hypoxia changes the way our brain tissue metabolism functions. Studies show Sherpas, native to the Himalayas are the most well adapted high-altitude humans.  Their brain metabolism is the same of that of “low-landers”. Conversely, the Quechuas who are native to the Andes of South America still show small amounts of hypometabolism in their brain. As mentioned previously, it is unknown how long it takes for humans to fully acclimate regarding brain metabolism.

These studies indicate the need for more research regarding brain metabolism and function.  Glucose metabolism is crucial for proper functioning of the brain, its neurons, and other regulatory functions. This brings into question what type of impact high altitude may have on the cognitive functions of the brain in people who move or even live at high altitude. Additionally, the fact that the human brain is more prone to injury or developing a concussion, safety should be a consideration for those involved in high impact sports at high altitude.

References

1.      Jaiswal S, Cramer N, Scott J, Meyer C, Xu X, Whiting K, Hoy A, Galdzicki Z, Dardzinski B.  [18F] FDG PET to study the effect of simulated high altitude on regional brain activity in mice. Journal of Nuclear Medicine May 2017, 58 (supplement 1) 1246.  https://jnm.snmjournals.org/content/58/supplement_1/1246

2.      Jaiswal S, Knutsen A, Pan H, Cramer N, Xu X, Dardzinski B, Galdzicki Z, Allison N, Haight T. FDG PET study showing the effect of high altitude and traumatic brain injury on regional glucose uptake in mice.  Journal of Nuclear Medicine May 2019, 60 (supplement 1) 180. https://jnm.snmjournals.org/content/60/supplement_1/180

3.      Hochachka PW, Clark CM, Matheson GO, et al. Effects on regional brain metabolism of high-altitude hypoxia: a study of six US marines. Am J Physiol. 1999;277(1):R314-R319. doi:10.1152/ajpregu.1999.277.1.R314.  https://pubmed.ncbi.nlm.nih.gov/10409288/

Roberta Grabocka is a second-year physician assistant student at Red Rocks Community College’s PA Program in Arvada, Colorado. Roberta attended Stony Brook University in Long Island, NY for her degree in Health Science and received a post-baccalaureate degree in Nuclear Medicine Technology. She practiced for 3 years as a Nuclear Medicine Technologist in multiple hospitals. This included working in oncological, cardiac, and general nuclear settings performing a variety of studies from PET/CTs, myocardial perfusion imaging, HIDAs, V/Qs, etc. Roberta decided to pursue a career as a Physician Assistant to expand her scope of practice and further her medical knowledge. In her free time, she likes to explore local culture and travel.

High-Altitude Pregnancy: An Overview of the Research Being Conducted by Dr. Lorna G. Moore and Colleagues

*All figures and graphs seen in this post came directly from a presentation by Dr. Lorna G Moore from the Department of Obstetrics & Gynecology, University of Colorado School of Medicine on September 15, 2021 at Saint Anthony Summit Hospital

It is well known that women living at high altitudes often give birth to infants of lower birth weight than those living at sea level due in part to intrauterine growth restriction (IUGR). However, causes of fetal growth restriction at high altitude are not well understood. Dr. Lorna G Moore and her colleagues have found high altitude (>8,000ft) such as that of Summit County, Colorado provide a natural laboratory for studying the physiological mechanisms sustaining fetal growth and identifying new therapies for treating pregnancy disorders.1 In this article, I will be reviewing their findings on fetal growth and uteroplacental blood flow at high altitude, whether activation of an enzyme called adenosine monophosphate kinase (AMPK) is protective, and whether hypoxia directly or indirectly reduces fetal growth.

A baby’s birth weight is the single greatest predictor of infant mortality. Preterm birth and low birth weight were the second leading causes of infant mortality in 2018 according to the CDC.2 While infants born at high altitude in Colorado have, on average, lower birth weights, multigenerational populations of Andeans and Tibetans are relatively protected from altitude-associated birth-weight reductions. Studies completed over the last 25 years in regions of the world where populations have lived at high altitude for many millennia (i.e., Andeans, Tibetans, and Ethiopians) provide “evidence for genetic adaptation to high altitude” that have been linked to improved  “distribution of blood flow to vital organs and the efficiency of O2 utilization ”.

Uterine artery blood flow is crucial for reproductive success as it provides the necessary blood flow to the placenta and the fetus to meet their metabolic demands. Uterine artery blood flow increases 60-fold at low altitude but has a lesser increase in high-altitude newcomers in Colorado or elsewhere.1 In contrast, a normal pregnancy rise in uterine artery blood flow occurs in Andeans and Tibetans (Ethiopians have not been studied). 

A major factor responsible for increasing uterine artery blood flow is an increase in the diameter of the main uterine artery. Of 63 genes identified as having been acted upon by natural selection, an allele called “TT” for the gene PRKAA1 which codes for the portion of AMPK involved in that enzyme’s activation is more common in Andeans and is associated both with greater uterine artery diameter and increased birth weight at high altitude.1,4 Activation of AMPK causes the uterine artery to dilate, which Dr. Moore and colleagues hypothesized would increase uterine artery blood flow and thereby help maintain birth weight. At low altitude, one of the key factors responsible for raising uterine artery blood is increased production of the vasodilator, nitric oxide (NO), in the uterine artery. Their studies showed that nitric-oxide induced vasodilation fails to occur at high altitude but, interestingly, uterine artery vasodilation in response to AMPK activation is increased, suggesting that “AMPK activation may be compensatory for the lesser NO-induced vasodilation and helps maintain fetal growth”.4 To test this idea, they used a drug called AICAR to activate AMPK in mice that were kept in simulated sea level (SL) or high altitude (HA) conditions during pregnancy. Mice that were given AICAR at high altitude showed an increase in uterine artery diameter, blood flow, and the percent of cardiac output directed to the uterine circulation (UtA flow/cardiac output).1,6

They also found that AICAR restored approximately half of the altitude-associated reduction in fetal weight.1

Their current studies are trying to figure out how a reduction in uterine artery blood flow reduces fetal growth. Their and other persons’ data suggest that lower blood flow is not solely responsible. Since AMPK is not only a vasodilator but also (and best known as) a “metabolic sensor”, Dr Moore and colleagues think that AMPK may be playing a crucial role in linking blood flow to metabolism factors at high altitude. They are planning to continue studies examining the metabolic factors involved in pregnancy and how they act to affect vasoreactivity and fetal growth.1

References

  1. Moore LG. Using studies at high altitude (HA) to identify the causes and ultimately new treatments for pregnancy disorders. lecture presented at the: September 9, 2021. 
  2. Infant mortality. Centers for Disease Control and Prevention. https://www.cdc.gov/reproductivehealth/maternalinfanthealth/infantmortality.htm. Published September 8, 2021. Accessed September 28, 2021. 
  3. Moore LG. Measuring high-altitude adaptation. J Appl Physiol (1985). 2017;123(5):1371-1385. doi:10.1152/japplphysiol.00321.2017
  4. Skeffington KL, Higgins JS, Mahmoud AD, et al. Hypoxia, AMPK activation and uterine artery vasoreactivity. J Physiol. 2016;594(5):1357-1369. doi:10.1113/JP270995
  5. Lorca RA, Lane SL, Bales ES, et al. High Altitude Reduces NO-Dependent Myometrial Artery Vasodilator Response During Pregnancy. Hypertension. 2019;73(6):1319-1326. doi:10.1161/HYPERTENSIONAHA.119.12641
  6. Lane SL, Houck JA, Doyle AS, et al. AMP-activated protein kinase activator AICAR attenuates hypoxia-induced murine fetal growth restriction in part by improving uterine artery blood flow. J Physiol. 2020;598(18):4093-4105. doi:10.1113/JP279341

Zoe Heller is a second year Physician Assistant student from Red Rocks Community College in Arvada, CO. She was born and raised in colorful Colorado and received her undergraduate degree in biological sciences at the University of Colorado Denver. Prior to PA school she worked as a professional research assistant at the Barbara Davis Center and a medical assistant at Denver Endocrinology, Diabetes and Thyroid Center. When she’s not in clinic or studying, you can find her hiking, skiing, or sitting by a campfire at her mountain property “Coolsville” with her husband and two pups, Timber and Willa.

The Nobel Prize: Hypoxia studies Won in 2019!

The Nobel prizes are announced this month. Alfred Nobel invented dynamite in 1866. Within 30 years, Nobel made a large fortune from his invention. He demonstrated his passion for literature and science by creating a yearly prize to discoveries most beneficial to humankind. The five prize categories include physics, chemistry, medicine (physiology), literature and peace. The Nobel prize nominations are made by university professors, national assemblies, state governments, and international courts. The prize is awarded yearly to individuals who have discovered a new paradigm or a paradigm shift within their field. The prize recipients are declared on the first Monday of October of every year and the award is presented by the Nobel assembly on November 10th, the anniversary of Alfred Nobel’s death. The Nobel prize consists of a gold medal, a diploma of recognition of achievement, and a cash prize in the amount of $1 million U.S. dollars. 

There is no limit to the number of nominations that can be made or the number of times that an individual can be nominated. There were 400 candidates nominated in the field of medicine in 2019, all of which inspired, challenged, and demonstrated greatness in their field. In 2019 the Nobel Prize in Medicine honored three scientists for their discovery of the human body’s ability to adapt to low oxygen environments. 

Hypoxia is a state of which oxygen supply is insufficient for normal life functions, experienced by the human body at high altitude. Tissues and cells require a range of oxygen in order to survive. Oxygen is required by mitochondria, in all cells, to convert food into useable energy. “Otto Warburg, the recipient of the 1931 Nobel Prize in Physiology or Medicine, revealed that this conversion is an enzymatic process.” At low oxygen environments, as experienced at high altitude, the body must adapt in order to maintain basic cellular function. There are several mechanisms in the human body that increase oxygen concentration including breathing rate, regulated by the carotid body, increased heart rate, stimulated by the vagus nerve, and increased production of red blood cells (RBCs)  through the bone marrow, regulated by the kidney. 

The carotid body is a chemoreceptor near the carotid artery that detects oxygen, carbon dioxide and pH levels in the blood. At low oxygen, the carotid body relays an afferent (ingoing) signal to the the brain via the glossopharyngeal nerve. The medullary center in the brain then sends an efferent (outgoing) signal that increases the respiratory rate to maximize oxygen delivery to the brain. The carotid sinus is a baroreceptor near the aorta of the heart which senses changes in pressure. As pressure increases in the atmosphere, experienced at high altitude, the carotid sinus sends a signal along the vagus nerve to the brain which then increases the heart rate. “The 1938 Nobel Prize in Physiology or Medicine was awarded to Corneille Heymans for discoveries showing how blood oxygen sensing via the carotid body controls our respiratory rate by communicating directly with the brain.”

At low oxygen environments, the kidney increases production of erythropoietin, which stimulates RBC generation in the bone marrow,  called erythropoiesis, resulting in higher oxygen delivery to the brain and skeletal muscles needed at high altitude. Erythropoiesis was discovered in the early 20th century, however oxygen’s role in the process was not completely understood. The cell’s ability to sense and adapt to oxygen availability was discovered and explained by three scientists, William G. Kaelin Jr., Sir Peter J. Ratcliffe and Gregg L. Semenza. 

2019 Nobel Prize, Physiology: 

Thanks to the work of Dr. Gregg L. Semenza and Sir Peter J. Ratcliffe, we now understand that the oxygen sensing mechanism that stimulates erythropoieten is present in all tissues, not just the kidney. Semenza conducted research on liver cells using gene-modified mice and found that a specific protein binds to an individual gene (the EPO gene), dependent upon oxygen availability. Semenza named the binding protein the Hypoxia-Inducible-Factor (HIF). The HIF protein was found to compose two transcription factors, HIF-1alpha and ARNT. In 1995, Semenza published his findings of the HIF protein. His work explained that when the body is at high oxygen environments, there is very little HIF-1alpha present within cells. At high oxygen availability, HIF-1alpha is rapidly degraded by a proteasome within cells. The degradation is signaled by a protein called ubiquitin which binds to HIF-1alpha at high oxygen, flagging HIF-1alpha for degradation by the proteasome. This process was recognized by the 2004 Nobel Prize in Chemistry, Aaron Ciechanover, Avram Hershko and Irwin Rose. 

The mechanism by which ubiquitin binds, causing the degradation of HIF-1alpha at high oxygen environments was explained by the work of William Kaelin, Jr. who conducted research on von Hippel-Lidau’s (VHL) disease. The VHL gene mutation causes an increased risk of cancer. Kaelin showed that the VHL gene encodes a protein that prevents the onset of cancer and was involved in controlling responses to hypoxia. VHL is part of a complex that labels proteins with ubiquitin. Ratcliffe discovered the physical interaction of the VHL gene with HIF-1alpha, causing degradation of the HIF-1alpha at normal oxygen levels. 

At hypoxic environments, HIF-1α is protected from degradation and accumulates in the nucleus, where it associates with ARNT and binds to specific DNA sequences (HRE) in hypoxia-regulated genes (1). At normal oxygen levels, HIF-1α is rapidly degraded by the proteasome (2). Oxygen regulates the degradation process by the addition of hydroxyl groups (OH) to HIF-1α (3). The VHL protein can then recognize and form a complex with HIF-1α leading to its degradation in an oxygen-dependent manner (4). 


At hypoxic environments, HIF-1α is protected from degradation and accumulates in the nucleus, where it associates with ARNT and binds to specific DNA sequences (HRE) in hypoxia-regulated genes (1). At normal oxygen levels, HIF-1α is rapidly degraded by the proteasome (2). Oxygen regulates the degradation process by the addition of hydroxyl groups (OH) to HIF-1α (3). The VHL protein can then recognize and form a complex with HIF-1α leading to its degradation in an oxygen-dependent manner (4).

Kaelin and Ratcliffe’s research identified how oxygen levels regulate the interaction between VHL and HIF-1alpha. Their work demonstrated that at normal oxygen levels, hydroxyl groups are added to specific positions within HIF-1alpha, causing modification of the protein and allowing VHL to recognize and bind to HIF-1alpha, leading to degradation of the protein complex.  At high altitude, cells produce a greater amount of the HIF-1alpha protein which binds to the EPO gene, up-regulating the production of erythropoietin hormone, stimulating RBC production. Together, Semenza, Kaelin, and Ratcliffe explained the oxygen sensing mechanism.