Extreme altitude induces divergent mass reduction of right and left ventricle in mountain climbers

Mountain climbing at high altitude implies exposure to low levels of oxygen, low temperature, wind, physical and psychological stress, and nutritional insufficiencies. We examined whether right ventricular (RV) and left ventricular (LV) myocardial masses were reversibly altered by exposure to extreme altitude. Magnetic resonance imaging and echocardiography of the heart, dual x‐ray absorptiometry scan of body composition, and blood samples were obtained from ten mountain climbers before departure to Mount Everest or Dhaulagiri (baseline), 13.5 ± 1.5 days after peaking the mountain (post‐hypoxia), and six weeks and six months after expeditions exceeding 8000 meters above sea level. RV mass was unaltered after extreme altitude, in contrast to a reduction in LV mass by 11.8 ± 3.4 g post‐hypoxia (p = 0.001). The reduction in LV mass correlated with a reduction in skeletal muscle mass. After six weeks, LV myocardial mass was restored to baseline values. Extreme altitude induced a reduction in LV end‐diastolic volume (20.8 ± 7.7 ml, p = 0.011) and reduced E’, indicating diastolic dysfunction, which were restored after six weeks follow‐up. Elevated circulating interleukin‐18 after extreme altitude compared to follow‐up levels, might have contributed to reduced muscle mass and diastolic dysfunction. In conclusion, the mass of the RV, possibly exposed to elevated afterload, was not changed after extreme altitude, whereas LV mass was reduced. The reduction in LV mass correlated with reduced skeletal muscle mass, indicating a common denominator, and elevated circulating interleukin‐18 might be a mechanism for reduced muscle mass after extreme altitude.

High Altitude Limits of Living Things

West, John B. High altitude limits of living things. High Alt Med Biol. 22:342-345, 2021.-The tolerance of animals to high altitude is generally limited by the low partial pressure of oxygen (PO₂) in the air. Plant growth at high altitude is also limited but by different mechanisms. This article is a brief survey of the limiting factors of all living things. By a curious coincidence, the highest point on earth, that is Mt. Everest at 8,848 m, appears to be right at the limit of human tolerance to hypoxia. The altitude of the highest permanent human habitation, that is a town, is 5,100 m. This altitude is partly determined by the hypoxia, but also by economic factors. For other terrestrial mammals, birds, and insects, the highest altitudes for permanent habitation apparently belong to field mice (Phyllotis xanthopygus rupestris) and jumping spiders (Euophrys omnisuperstes) at about 6,700 m. Birds have been known to fly as high as 11,000 m although how much they are elevated by atmospheric updrafts is not clear. The record for animals for survival in extreme hypoxia is arguably held by the primitive invertebrate, the tardigrade (Hypsibius dujardini). This has been shown to tolerate the hard vacuum of space where the PO₂ is essentially zero for many days. Less is known about the tolerance of plants to extreme altitude. However, vascular plants have been collected at >6,000 m in the Himalayas, and moss grows even higher. Lichens are very tolerant of severe hypoxia. There is evidence that global warming is increasing the highest altitudes at which plants can survive.

Comparison of Environmental Conditions on Summits of Mount Everest and K2 in Climbing and Midwinter Seasons

(1) Background: Today’s elite alpinists target K2 and Everest in midwinter. This study aimed to asses and compare weather at the summits of both peaks in the climbing season (Everest, May; K2, July) and the midwinter season (January and February). (2) Methods: We assessed environmental conditions using the ERA5 dataset (1979–2019). Analyses examined barometric pressure (BP), temperature (Temp), wind speed (Wind), perceived altitude (Alt), maximal oxygen uptake (VO₂max), vertical climbing speed (Speed), wind chill equivalent temperature (WCT), and facial frostbite time (FFT). (3) Results: Most climbing-season parameters were found to be more severe (p < 0.05) on Everest than on K2: BP (333 ± 1 vs. 347 ± 1 hPa), Alt (8925 ± 20 vs. 8640 ± 20 m), VO₂max (16.2 ± 0.1 vs. 17.8 ± 0.1 ml·kg⁻¹·min⁻¹), Speed (190 ± 2 vs. 223 ± 2 m·h⁻¹), Temp (−26 ± 1 vs. −21 ± 1°C), WCT (−45 ± 2 vs. −37 ± 2 °C), and FFT (6 ± 1 vs. 11 ± 2 min). Wind was found to be similar (16 ± 3 vs. 15 ± 3 m·s⁻¹). Most midwinter parameters were found to be worse (p < 0.05) on Everest vs. K2: BP (324 ± 2 vs. 326 ± 2 hPa), Alt (9134 ± 40 vs. 9095 ± 48 m), VO₂max (15.1 ± 0.2 vs. 15.3 ± 0.3 ml·kg⁻¹·min⁻¹), Speed (165 ± 5 vs. 170 ± 6 m·h⁻¹), Wind (41 ± 6 vs. 27 ± 4 m·s⁻¹), and FFT (<1 min vs. 1 min). Everest’s Temp of −36 ± 2 °C and WCT −66 ± 3 °C were found to be less extreme than K2’s Temp of −45 ± 1 °C and WCT −76 ± 2 °C. (4) Conclusions: Everest presents more extreme conditions in the climbing and midwinter seasons than K2. K2’s 8° higher latitude makes its midwinter BP similar and Temp lower than Everest’s. K2’s midwinter conditions are more severe than Everest’s in the climbing season.

Echocardiographic Assessment of Right Ventricle Dimensions and Function After Exposure to Extreme Altitude: Is an Expedition to 8000 m Hazardous for Right Ventricular Function?

Kurdziel, Marta, Jarosław Wasilewski, Karolina Gierszewska, Anna Kazik, Gracjan Pytel, Jacek Wacławski, Adam Krajewski, Anna Kurek, Lech Poloński, and Mariusz Gąsior. Echocardiographic assessment of right ventricle dimensions and function after exposure to extreme altitude: Is an expedition to 8000 m hazardous for right ventricular function? High Alt Med Biol 18:330-337, 2017.-Although the right ventricle (RV) is under great hypoxic stress at altitude, still little is known what happens to the RV after descent. The aim of this study was to evaluate RV dimensions and function after exposure to extreme altitude. Therefore, echocardiographic examination was performed according to a protocol that focused on the RV in 11 healthy subjects participating in an expedition to K2 (8611 m) or Broad Peak (BP, 8051 m). In comparison to measurements before the expedition, after 7-8 weeks of sojourn above 2300 meters with the aim of climbing K2 and BP, the RV Tei index increased (0.5 ± 0.1 vs. 0.4 ± 0.1; p = 0.028), and RV free wall longitudinal systolic strain (RVFWLSS) decreased (-23.1% ± 2.7% vs. -25.9% ± 2.4%; p = 0.043). Decrease in peak systolic strain and strain rate was observed in the basal and mid segments of the RV free wall (respectively: -24.4% ± 4.4% vs. -30.9% ± 6.5%; -1.4 ± 0.3 s^-1 vs. -1.8 ± 0.3 s^-1; -28.7% ± 3.9% vs. -34% ± 3.3%; -1.5 ± 0.2 s^-1 vs. -1.9 ± 0.3 s^-1; p for all <0.05). The linear RV dimensions, the proximal and distal RV outflow tracks, increased (respectively: 31.3 ± 4 mm vs. 29.2 ± 3 mm, p = 0.025; 27 ± 2.7 mm vs. 24.8 ± 3 mm, p = 0.012). We found that exposure to extreme altitude may cause RV dilatation and a decrease in RV performance. The Tei index and RVFWLSS are sensitive performance indices to detect changes in RV function after the exposure to hypoxic stress. The observed alterations seem to be a manifestation of physiological adaptation to high-altitude condition in healthy individuals.

Pulmonary Embolism Masquerading as High Altitude Pulmonary Edema at High Altitude

Pandey, Prativa, Benu Lohani, and Holly Murphy. Pulmonary embolism masquerading as high altitude pulmonary edema at high altitude. High Alt Med Biol. 17:353-358, 2016.-Pulmonary embolism (PE) at high altitude is a rare entity that can masquerade as or occur in conjunction with high altitude pulmonary edema (HAPE) and can complicate the diagnosis and management. When HAPE cases do not improve rapidly with descent, other diagnoses, including PE, ought to be considered. From 2013 to 2015, we identified eight cases of PE among 303 patients with initial diagnosis of HAPE. Upon further evaluation, five had deep vein thrombosis (DVT). One woman had a contraceptive ring and seven patients had no known thrombotic risks. PE can coexist with or mimic HAPE and should be considered in patients presenting with shortness of breath from high altitude regardless of thrombotic risk.

Ventilatory chemosensitivity, cerebral and muscle oxygenation, and total hemoglobin mass before and after a 72-day mt. Everest expedition

BACKGROUND

We investigated the effects of chronic hypobaric hypoxic acclimatization, performed over the course of a 72-day self-supported Everest expedition, on ventilatory chemosensitivity, arterial saturation, and tissue oxygenation adaptation along with total hemoglobin mass (tHb-mass) in nine experienced climbers (age 37±6 years, [Formula: see text] 55±7 mL·kg(-1)·min(-1)).

METHODS

Exercise-hypoxia tolerance was tested using a constant treadmill exercise of 5.5 km·h(-1) at 3.8% grade (mimicking exertion at altitude) with 3-min steps of progressive normobaric poikilocapnic hypoxia. Breath-by-breath ventilatory responses, Spo2, and cerebral (frontal cortex) and active muscle (vastus lateralis) oxygenation were measured throughout. Acute hypoxic ventilatory response (AHVR) was determined by linear regression slope of ventilation vs. Spo2. PRE and POST (<15 days) expedition, tHb-mass was measured using carbon monoxide-rebreathing.

RESULTS

Post-expedition, exercise-hypoxia tolerance improved (11:32±3:57 to 16:30±2:09 min, p<0.01). AHVR was elevated (1.25±0.33 to 1.63±0.38 L·min(-1.)%(-1) Spo2, p<0.05). Spo2 decreased throughout exercise-hypoxia in both trials, but was preserved at higher values at 4800 m post-expedition. Cerebral oxygenation decreased progressively with increasing exercise-hypoxia in both trials, with a lower level of deoxyhemoglobin POST at 2400, 3500 and 4800 m. Muscle oxygenation also decreased throughout exercise-hypoxia, with similar patterns PRE and POST. No relationship was observed between the slope of AHVR and cerebral or muscle oxygenation either PRE or POST. Absolute tHb-mass response exhibited great individual variation with a nonsignificant 5.4% increasing trend post-expedition (975±154 g PRE and 1025±124 g POST, p=0.17).

CONCLUSIONS

We conclude that adaptation to chronic hypoxia during a climbing expedition to Mt. Everest will increase hypoxic tolerance, AHVR, and cerebral but not muscle oxygenation, as measured during simulated acute hypoxia at sea level. However, tHb-mass did not increase significantly and improvement in cerebral oxygenation was not associated with the change in AHVR.

Hematological changes in an elite climber over 18 years

AIMS

To evaluate the influence of repeated exposure to high altitude over a period of 18 years in an elite climber, red blood cell related parameters were analyzed. Red blood cell levels, hemoglobin concentration, and hematocrit were taken before and after expedition.

RESULTS

The analysis, revealed an average increase of 15% in red blood cell related parameters, and showed a negative correlation (p<0.01) between age and post-expedition results. Furthermore, the first part of the study period was statistically different compared to the second (p<0.01).

CONCLUSION

Exposure to extreme altitudes does lead to an increase in red blood cell parameters in the subject of the present study, as it can be seen from the results. Interestingly, this hematological response to extreme hypobaric hypoxia stimuli was attenuated over time. This however is a case report on an elite climber, and further research is needed in order to determine if such responses can be observed in other populations.

An observational study of personal ultraviolet dosimetry and acute diffuse reflectance skin changes at extreme altitude

OBJECTIVE

To determine the level of UV radiation at extreme altitude and to assess the effect it has on the skin.

METHODS

Fifteen expeditioners and 10 Sherpas were assessed during a climbing expedition on the north side of Mt Everest (8848 m). UV exposure measurement and diffuse skin reflectance spectrophotometry were performed at the beginning and end of the expedition.

RESULTS

Over the course of the expedition, the expeditioners and Sherpas received a median dose of 93.6 (interquartile range [IQR], 61.0-102.8) and 102.5 (IQR, 72.2-117.8) minimal erythemal doses (MEDs) of UV radiation. The maximum dosage exceeded 106 ± 1.4 MEDs. Using reflectance spectrophotometry, expeditioner and Sherpa melanin-hemoglobin increased by 83.6% (IQR, -1.5 to 89.8%) and 24.7% (IQR, -22.4 to 61.5%) for exposed skin, respectively. The amount of subcutaneous lipid-water decreased by a factor of 196.6 (IQR, 52.1-308.4) and 46.7 (IQR, 1.8-1156.5), for expeditioners and Sherpas, respectively.

CONCLUSIONS

This expedition's participants received massive doses of UV radiation during their time at high altitude. In many individuals this was similar to the annual exposure of northern European office-workers (100 MEDs). Diffuse skin reflectance spectroscopy revealed considerable subcutaneous lipid loss, skin dehydration, and increased melanin in keeping with these levels of exposure.

Heart rate variability changes at 2400 m altitude predicts acute mountain sickness on further ascent at 3000-4300 m altitudes

OBJECTIVE

If the body fails to acclimatize at high altitude, acute mountain sickness (AMS) may result. For the early detection of AMS, changes in cardiac autonomic function measured by heart rate variability (HRV) may be more sensitive than clinical symptoms alone. The purpose of this study was to ascertain if the changes in HRV during ascent are related to AMS.

METHODS

We followed Lake Louise Score (LLS), arterial oxygen saturation at rest (R-SpO(2)) and exercise (Ex-SpO(2)) and HRV parameters daily in 36 different healthy climbers ascending from 2400 m to 6300 m altitudes during five different expeditions.

RESULTS

After an ascent to 2400 m, root mean square successive differences, high-frequency power (HF(2 min)) of HRV were 17-51% and Ex-SpO(2) was 3% lower in those climbers who suffered from AMS at 3000 to 4300 m than in those only developing AMS later (≥5000 m) or not at all (all p < 0.01). At the altitude of 2400 m RMSSD(2 min) ≤ 30 ms and Ex-SpO(2) ≤ 91% both had 92% sensitivity for AMS if ascent continued without extra acclimatization days.

CONCLUSIONS

Changes in supine HRV parameters at 2400 m were related to AMS at 3000-4300 m Thus, analyses of HRV could offer potential markers for identifying the climbers at risk for AMS.