Risk Of Acute Mountain Sickness Research Articles

Using modified Fenn diagrams to assess ventilatory acclimatization during ascent to high altitude: Effect of acetazolamide.

High altitude (HA) ascent imposes systemic hypoxia and associated risk of acute mountain sickness. Acute hypoxia elicits a hypoxic ventilatory response (HVR), which is augmented with chronic HA exposure (i.e., ventilatory acclimatization; VA). However, laboratory-based HVR tests lack portability and feasibility in field studies. As an alternative, we aimed to characterize area under the curve (AUC) calculations on Fenn diagrams, modified by plotting portable measurements of end-tidal carbon dioxide ( ) against peripheral oxygen saturation ( ) to characterize and quantify VA during incremental ascent to HA (n=46). Secondarily, these participants were compared with a separate group following the identical ascent profile whilst self-administering a prophylactic oral dose of acetazolamide (Az; 125mg BID; n=20) during ascent. First, morning and measurements were collected on 46 acetazolamide-free (NAz) lowland participants during an incremental ascent over 10days to 5160m in the Nepal Himalaya. AUC was calculated from individually constructed Fenn diagrams, with a trichotomized split on ranked values characterizing the smallest, medium, and largest magnitudes of AUC, representing high (n=15), moderate (n=16), and low (n=15) degrees of acclimatization. After characterizing the range of response magnitudes, we further demonstrated that AUC magnitudes were significantly smaller in the Az group compared to the NAz group (P=0.0021), suggesting improved VA. These results suggest that calculating AUC on modified Fenn diagrams has utility in assessing VA in large groups of trekkers during incremental ascent to HA, due to the associated portability and congruency with known physiology, although this novel analytical method requires further validation in controlled experiments. HIGHLIGHTS: What is the central question of this study? What are the characteristics of a novel methodological approach to assess ventilatory acclimatization (VA) with incremental ascent to high altitude (HA)? What is the main finding and its importance? Area under the curve (AUC) magnitudes calculated from modified Fenn diagrams were significantly smaller in trekkers taking an oral prophylactic dose of acetazolamide compared to an acetazolamide-free group, suggesting improved VA. During incremental HA ascent, quantifying AUC using modified Fenn diagrams is feasible to assess VA in large groups of trekkers with ascent, although this novel analytical method requires further validation in controlled experiments.

Hormonal Contraception and Menstrual Cycle Control at High Altitude: A Scoping Review-UIAA Medical Commission Recommendations.

Horakova, Lenka , Susi Kriemler, Vladimír Študent, Jacqueline Pichler Hefti, David Hillebrandt, Dominique Jean, Kastė Mateikaitė-Pipirienė, Peter Paal, Alison Rosier, Marija Andjelkovic, Beth Beidlemann, Mia Derstine, and Linda E. Keyes. Hormonal contraception and menstrual cycle control at high altitude: a scoping review-UIAA Medical Commission recommendations. High Alt Med Biol. 00:00-00, 2024. Background: Women who use hormonal contraception (HC) may have questions about their use during travel to high altitude. This scoping review summarizes current evidence on the efficacy and safety of HC and cycle control during high-altitude travel. Methods: We performed a scoping review for the International Climbing and Mountaineering Federation (UIAA) Medical Commission series on Women's Health in the Mountains. Pertinent literature from PubMed and Cochrane was identified by keyword search combinations (including contraception) with additional publications found by hand search. Results: We identified 17 studies from 7,165 potentially eligible articles. No articles assessed the efficacy of contraception during a short-term high-altitude sojourn. Current data show no advantage or disadvantage in HC users for acclimatization or acute mountain sickness (AMS). Use of HC during high-altitude travel is common and safe for menses suppression. A potential concern of estrogen-containing HC is the increased thrombotic risk, which theoretically could be compounded in hypobaric hypoxia. Conclusions: Evidence is limited for the interaction of HC and high altitude on performance, thrombosis, and contraceptive efficacy. HC does not affect the risk of AMS. The most efficacious and safest method at high altitude is generally the one women are most familiar with and already using.

Influence of Smoking and Alcohol Habits on Symptoms of Acute Mountain Sickness on Mount Fuji: A Questionnaire Survey-Based Pilot Study.

Horiuchi, Masahiro, Satomi Mitsui, and Tadashi Uno. Influence of smoking and alcohol habits on symptoms of acute mountain sickness on Mount Fuji: a questionnaire survey-based pilot study. High Alt Med Biol 00:000-000, 2024. Background: Acute cigarette smoking or alcohol intake would cause opposing vasculature effects that may influence acute mountain sickness (AMS). The present study aimed to investigate the effects of smoking and alcohol consumption behaviors, and acute smoking and consuming alcohol during ascent on AMS on Mount Fuji. Methods: This questionnaire survey study included 887 participants who climbed Mount Fuji and obtained information regarding sex, age, and smoking and alcohol habits, including behavior during ascent. Results: AMS prevalence was 45% for all participants. A univariate analysis revealed that younger participants (20-29 years) were associated with increased AMS prevalence (effect size [ES] = 0.102, p = 0.057) and severity (ES = 0.18, p = 0.01). A prediction model using multiple logistic regression indicated that several factors influenced AMS risk: younger age (p = 0.001), daily smoking habits (p = 0.021), no smoking (p = 0.033), or alcohol consumption during ascent (p = 0.096). Alcohol consumption during ascent had no effect on the increased AMS risk in younger participants (20-29 years), while alcohol consumption during ascent increased AMS risk for middle-age participants (50-59 years). Conclusion: Younger individuals are more likely to experience AMS. Smoking habits are associated with an increased AMS risk. It may be recommended that middle-aged climbers should ascend without consuming alcohol.

Patterns of Structural Changes in the Fundus Measured by Optical Coherence Tomography Angiography as Potential Markers of Acute Mountain Sickness.

To use optical coherence tomography angiography (OCTA) to assess the pattern of changes in retinal and choroidal blood flow and structure in healthy volunteers who quickly went from sea level to a plateau and to determine the parameters associated with acute mountain sickness (AMS). Forty-five individuals (89 eyes) were examined by OCTA and filled out the AMS questionnaire. One baseline examination was performed on the plain, followed by examinations at days 1, 3, and 5 after entering the plateau. Parameters were self-controlled to explore patterns of change, analyzed for correlation with AMS score, and modeled as a nomogram of AMS risk. On the plateau compared to the plain, vascular morphology showed dilated superficial macular retinal vessels and constricted deeper layers with increased vessel length density and fractal dimension; vessel density increased in all retinal strata and decreased in the choroidal macrovascular layer; and thickness increased except for a decrease in mean retinal thickness in the central macular sulcus. The rate of increase in retinal nerve fiber layer (RNFL) thickness in the inner and outer macular rings correlated with AMS score (r = -0.211). The nomogram showed moderate accuracy (AUC = 0.672) and consistency (C-index = 0.659) in assessing AMS risk. In high-altitude hypoxia, retinal vessels dilate and distort, resulting in increased blood flow density and thickness. Increased RNFL thickness in the paracentral macula may be a marker of low AMS risk. The changes in the retinal structure of the fundus can be used to assess the risk of developing AMS.

Prior History of Mild Coronavirus Disease 2019 Does Not Increase Risk of Acute Mountain Sickness

Prior History of Mild Coronavirus Disease 2019 Does Not Increase Risk of Acute Mountain Sickness

Do cardiopulmonary exercise tests predict summit success and acute mountain sickness? A prospective observational field study at extreme altitude

ObjectiveDuring a high-altitude expedition, the association of cardiopulmonary exercise testing (CPET) parameters with the risk of developing acute mountain sickness (AMS) and the chance of reaching the summit were investigated.MethodsThirty-nine...

Incidence and risk factors of acute mountain sickness in grid construction personnel working at plateau

Objective: To analyze the incidence and risk factors of acute mountain sickness (AMS) in grid construction personnel working at plateau. Methods: A total of 10 956 plateau construction personnel of Ali Network Project from January 1, 2019 to December 31, 2020 were included. Baseline information (including age, sex, body mass index, developmental and nutritional status, relevant clinical indicators, etc.) and follow-up data of AMS were obtained from the medical record of Ali Internet engineering staff medical station. The altitude of the residence place in early life and the working environment were obtained from the website (https://zh-cn.topographic-map.com/legal/). The incidences of overall AMS and its subgroups were calculated, and the Cox proportional hazards model was used to explore the risk factors for AMS. Results: The age of the participants was (36.1±10.5) years old at baseline, and 95.27% (10 438) of them were males. The follow-up time was (17.46±4.23) months. The altitude of the residence place in early-life and working environment were (1 959±937) m and (4 533±233) m, respectively. During the follow-up period, the incidence of AMS was 15.58% (1 707 cases), and the incidence for acute mountain sickness and high altitude pulmonary edema were 15.53% (1 702 cases) and 0.05% (5 cases), respectively. No high altitude cerebral edema patients were found. Cox proportional hazards model showed that the risk of AMS increased by 45% for every 100 m elevation in the altitude of working environment [HR (95%CI): 1.45 (1.41-1.51)]. The higher the altitude for the residence place in early-life, the lower the risk of AMS [HR (95%CI): 0.84 (0.80-0.88)]. Compared with the group with oxygen saturation during 90%-94%, the participants with oxygen saturation<75% [HR (95%CI): 1.67 (1.24-2.23)] at baseline was also associated with increased risk of AMS. Conclusions: The incidence of AMS is relatively low in grid construction workers working on plateau. The risk factors of AMS included higher working altitude, lower altitude of the residence place in early-life and oxygen saturation<75%.

IoT-Enabled Intelligent Dynamic Risk Assessment of Acute Mountain Sickness: The Role of Event-Triggered Signal Processing

The rapid developments in Internet of Medical Things open up new avenues for personalized healthcare. Continuously monitored physiological data can be collected by wearable devices and are transmitted to a remote server for real-time monitoring and diagnosis. This article concerns a risk assessment problem of acute mountain sickness (AMS) with data transmitted according to an event-triggered transmission schedule. An event-triggered signal processing approach is introduced to reconstruct the untransmitted information, based on which, a dynamic SpO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\bf 2}$</tex-math></inline-formula> index (DSI) is further proposed for AMS risk evaluation. The performance of the proposed approach is analyzed through physiological data collected in a proof-of-the-concept study ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> =12). Statistical significant correlation of the DSI with AMS ground truth including Lake Louise score, deep sleep duration, deep sleep ratio, and mean SpO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\bf 2}$</tex-math></inline-formula> during sleep is observed. More importantly, it is observed that the proposed event-triggered signal processing procedure can dramatically reduce the data transmission rate while maintaining the performance of the DSI assessment, through comparison of the DSI obtained using the proposed event-triggered approach with those obtained based on event-triggered raw data and continuously transmitted time-triggered data. The obtained results indicate the feasibility of adopting event-triggered data scheduling and signal processing to achieve AMS risk evaluation using data from wearable devices with limited communication/battery resources.

Sleep loss effects on physiological and cognitive responses to systemic environmental hypoxia.

In the course of their missions or training, alpinists, but also mountain combat forces and mountain security services, professional miners, aircrew, aircraft and glider pilots and helicopter crews are regularly exposed to altitude without oxygen supplementation. At altitude, humans are exposed to systemic environmental hypoxia induced by the decrease in barometric pressure (<1,013hPa) which decreases the inspired partial pressure of oxygen (PIO2), while the oxygen fraction is constant (equal to approximately 20.9%). Effects of altitude on humans occur gradually and depend on the duration of exposure and the altitude level. From 1,500m altitude (response threshold), several adaptive responses offset the effects of hypoxia, involving the respiratory and the cardiovascular systems, and the oxygen transport capacity of the blood. Fatigue and cognitive and sensory disorders are usually observed from 2,500m (threshold of prolonged hypoxia). Above 3,500m (the threshold for disorders), the effects are not completely compensated and maladaptive responses occur and individuals develop altitude headache or acute altitude illness [Acute Mountain Sickness (AMS)]. The magnitude of effects varies considerably between different physiological systems and exhibits significant inter-individual variability. In addition to comorbidities, the factors of vulnerability are still little known. They can be constitutive (genetic) or circumstantial (sleep deprivation, fatigue, speed of ascent.). In particular, sleep loss, a condition that is often encountered in real-life settings, could have an impact on the physiological and cognitive responses to hypoxia. In this review, we report the current state of knowledge on the impact of sleep loss on responses to environmental hypoxia in humans, with the aim of identifying possible consequences for AMS risk and cognition, as well as the value of behavioral and non-pharmacological countermeasures.

Can acute high-altitude sickness be predicted in advance?

In high-altitude environments, the oxygen andair density are decreased, and the temperature and humidity are low. When individuals enter high-altitude areas, they are prone to suffering from acute mountain sickness (AMS) because they cannot tolerate hypoxia. Headache, fatigue, dizziness, and gastrointestinal reactions are the main symptoms of AMS. When these symptoms cannot be effectively alleviated, they can progress to life-threatening high-altitude pulmonary edema or high-altitude cerebral edema. If the risk of AMS can be effectively assessed before people enter high-altitude areas, then the high-risk population can be promptly discouraged from entering the area, or drug intervention can be established in advance to prevent AMS occurrence and avoid serious outcomes. This article reviews recent studies related to the early-warning biological indicators of AMS to provide a new perspective on the prevention of AMS.

Association of Pre-existing Mental Health Conditions with Acute Mountain Sickness at Everest Base Camp.

Hüfner, Katharina, Fabio Caramazza, Evelyn R. Pircher Nöckler, Agnieszka E. Stawinoga, Paolo Fusar-Poli, Sanjeeb S. Bhandari, Buddha Basnyat, Monika Brodmann Maeder, Giacomo Strapazzon, Iztok Tomazin, Ken Zafren, Hermann Brugger, and Barbara Sperner-Unterweger. Association of pre-existing mental health conditions with acute mountain sickness at Everest Base Camp. High Alt Med Biol. 23:338-344, 2022. Background: Mental health disorders are common, but limited data are available regarding the number of people with a past medical history of psychiatric diagnoses going to high altitude (HA). It is also unknown whether mental health conditions are associated with an increased risk of acute mountain sickness (AMS). Methods: We analyzed data from a previous study at Everest Base Camp. Participants self-reported their past medical history and history of substance use and had a brief history taken by a physician. AMS was assessed using the self-reported 2018 Lake Louise AMS Score. Results: Eighty-five participants (66 men and 19 women, age 38 ± 9 years) were included. When questioned by a physician, 28 participants reported prior diagnoses or symptoms compatible with depression (23%), anxiety disorder (6%), post-traumatic stress disorder (1%), and psychosis/psychotic experiences (9%). The prevalence of psychiatric diagnoses in the past medical history was much lower in the self-reported data (2/85) compared to data obtained via physician assessment (28/85). Increased risks of AMS were associated with a past medical history of anxiety disorder (odds ratio [OR] 22.7; confidence interval [95% CI] 2.3-220.6; p < 0.001), depression (OR 3.6; 95% CI 1.2-11.2; p = 0.022), and recreational drug use ever (OR 7.3; 95% CI 1.5-35.5; p = 0.006). Conclusions: Many people who travel to HA have a past medical history of mental health conditions. These individuals have an increased risk of scoring positive for AMS on the Lake Louise Score compared with people without a history of mental health conditions.

Rescue Emergencies Due to High-Altitude Illnesses Are Rare in Switzerland.

Background: Despite a potential high risk of acute mountain sickness (AMS) in the Swiss Alps, there is a lack of analyses concerning its relevance over longer periods. In consequence, the aim of this study is to analyze the prevalence of AMS in comparison to other causes of mountain emergencies in recent years in Switzerland. Material and Methods: Based on the central registry of mountain emergencies of the Swiss Alpine Club (SAC), all cases in the period between 2009 and 2020 were analyzed for AMS including the most severe forms of high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). Emergencies were assessed for the severity of the event with a National Advisory Committee for Aeronautics (NACA) score. Results: From a total of 4596 high-altitude mountaineering emergencies identified in the observational period, a total number of 352 cases of illnesses were detected. Detailed analysis revealed 85 cases of AMS, 5 cases of HAPE, and 1 case of HACE. The average altitude was 3845 ± 540 m. Most cases were in the canton of Valais, especially in the Monte Rosa region and the mountains of the Mischabel group (Täschhorn, Dom, Südlenz, Nadelhorn, Hohberghorn). There were only three deaths related to high-altitude illnesses; all the other events could be identified as moderate to severe but not life-threatening. Discussion: An emergency due to AMS that requires rescue is unlikely in the Swiss Alps. This does not imply that AMS is not a concern. However, the facts that the maximal altitude is relatively low and that fast self-descents often seem possible probably minimize the likelihood that mountaineers with symptoms contact emergency services.

Hypobaric hypoxia deteriorates bone mass and strength in mice.

Mountaineers at high altitude are at increased risk of acute mountain sickness as well as high altitude pulmonary and cerebral edema. A densitometric study in mountaineers has suggested that expeditions at high altitude decrease bone mineral density. Surprisingly, the in vivo skeletal effects of hypobaric hypoxia are largely unknown, and have not been studied using advanced contemporary methods to assess bone microstructure. Eighty-four 22-week-old female mice were divided into seven groups with 12 mice in each group: 1. Baseline; 2. Normobaric, 4weeks; 3. Hypobaric hypoxia, 4weeks; 4. Normobaric, 8weeks; 5. Hypobaric hypoxia, 8weeks; 6. Normobaric, 12weeks; and 7. Hypobaric hypoxia, 12weeks. Hypobaric hypoxia mice were housed in hypobaric chambers at an ambient pressure of 500mbar (5500m altitude), while normobaric mice were housed at sea level atmospheric pressure for 4, 8, or 12weeks, respectively. Hypobaric hypoxia had a profound impact on femoral cortical bone and L4 trabecular bone, while the effect on femoral trabecular bone was less pronounced. Hypobaric hypoxia reduced the bone strength of the femoral mid-diaphysis and L4 at all time-points. At femoral cortical bone, hypobaric hypoxia reduced bone formation through fewer mineralizing surfaces and lower bone formation rate after 2weeks. In addition, bone strength decreased, and C-terminal telopeptide of type I collagen (CTX-I) increased independently of the duration of exposure to simulated high altitude. At L4, hypobaric hypoxia resulted in a substantial reduction in bone volume fraction, trabecular thickness, and trabecular number after 4weeks of exposure. Hypobaric hypoxia reduced bone strength and femoral bone mass, while femoral trabecular bone was much less affected, indicating the skeletal response to hypobaric hypoxia differ between cortical and trabecular bone. These findings provide initial preclinical support for future clinical studies in mountaineers to assess bone status and bone strength after exposure to prolonged high altitude exposure.

Using machine learning to determine the correlation between physiological and environmental parameters and the induction of acute mountain sickness

BackgroundRecent studies on acute mountain sickness (AMS) have used fixed-location and fixed-time measurements of environmental and physiological variable to determine the influence of AMS-associated factors in the human body. This study aims to measure, in real time, environmental conditions and physiological variables of participants in high-altitude regions to develop an AMS risk evaluation model to forecast prospective development of AMS so its onset can be prevented.ResultsThirty-two participants were recruited, namely 25 men and 7 women, and they hiked from Cuifeng Mountain Forest Park parking lot (altitude: 2300 m) to Wuling (altitude: 3275 m). Regression and classification machine learning analyses were performed on physiological and environmental data, and Lake Louise Acute Mountain Sickness Scores (LLS) to establish an algorithm for AMS risk analysis. The individual R2 coefficients of determination between the LLS and the measured altitude, ambient temperature, atmospheric pressure, relative humidity, climbing speed, heart rate, blood oxygen saturation (SpO2), heart rate variability (HRV), were 0.1, 0.23, 0, 0.24, 0, 0.24, 0.27, and 0.35 respectively; incorporating all aforementioned variables, the R2 coefficient is 0.62. The bagged trees classifier achieved favorable classification results, yielding a model sensitivity, specificity, accuracy, and area under receiver operating characteristic curve of 0.999, 0.994, 0.998, and 1, respectively.ConclusionThe experiment results indicate the use of machine learning multivariate analysis have higher AMS prediction accuracies than analyses utilizing single varieties. The developed AMS evaluation model can serve as a reference for the future development of wearable devices capable of providing timely warnings of AMS risks to hikers.

Respiratory alkalinization and posterior cerebral artery dilatation predict acute mountain sickness severity during 10h normobaric hypoxia.

What is the central question of this study? The pathophysiology of acute mountain sickness (AMS), involving the respiratory, renal and cerebrovascular systems, remains poorly understood. How do the early adaptations in these systems during a simulated altitude of 5000m relate to AMS risk? What is the main finding and its importance? The rate of blood alkalosis and cerebral artery dilatation predict AMS severity during the first 10 h of exposure to a simulated altitude of 5000m. Slow metabolic compensation by the kidneys of respiratory alkalosis attributable to a brisk breathing response together with excessive brain blood vessel dilatation might be involved in early development of AMS. The complex pathophysiology of acute mountain sickness (AMS) remains poorly understood and is likely to involve maladaptive responses of the respiratory, renal and cerebrovascular systems to hypoxia. Using stepwise linear regression, we tested the hypothesis that exacerbated respiratory alkalosis, as a result of a brisk ventilatory response, sluggish renal compensation in acute hypoxia and dysregulation of cerebral perfusion predict AMS severity. We assessed the Lake Louise score (LLS, an index of AMS severity), fluid balance, ventilation, venous pH, bicarbonate, sodium and creatinine concentrations, body weight, urinary pH and cerebral blood flow [internal carotid artery (ICA) and vertebral artery (VA) blood flow and diameter], in 27 healthy individuals (13 women) throughout 10h exposures to normobaric normoxia (fraction of inspired O2 = 0.21) and normobaric hypoxia (fraction of inspired O2 = 0.117, simulated 5000m) in a randomized, single-blinded manner. In comparison to normoxia, hypoxia increased the LLS, ventilation, venous and urinary pH, and blood flow and diameter in the ICA and VA, while venous concentrations of both bicarbonate and creatinine were decreased (P<0.001 for all). There were significant correlations between AMS severity and the rates of change in blood pH, sodium concentration and VA diameter and more positive fluid balance (P<0.05). Stepwise regression found increased blood pH [beta coefficient (β) = 0.589, P<0.001] and VA diameter (β = 0.418, P = 0.008) to be significant predictors of AMS severity in our cohort [F(2, 20) = 16.1, R2 = 0.617, P<0.001, n = 24], accounting for 62% of the variance in peak LLS. Using classic regression variable selection, our data implicate the degree of respiratory alkalosis and cerebrovascular dilatation in the early stages of AMS development.

Incidence and Determinants of Acute Mountain Sickness in Mount Kinabalu, Malaysia.

Yang, Su Lan, Nor At'fina Ibrahim, Grazele Jenarun, and Houng Bang Liew. Incidence and determinants of acute mountain sickness in Mount Kinabalu, Malaysia. High Alt Med Biol. 21:265–272, 2020.Background: Acute mountain sickness (AMS) is the most common type of high-altitude sickness. The incidence of AMS varies by mountain location, trail characteristics, and study design. The lack of local epidemiology data has driven us to investigate the incidence and severity of AMS and its associated factors at Mount Kinabalu, Malaysia.Methods: A cohort study was conducted to collect data from climbers after days 1 (3272 m) and 2 (4095 m) of ascent. A self-administered questionnaire was used to explore climbers' demographic and climb characteristics, history of AMS, alcohol exposure, and AMS prevention measures. The Lake Louis score 2018 was used to assess the presence and severity of AMS (cutoff ≥3). Univariate and multivariable logistic regressions were performed to determine the factors associated with the development of AMS on day 2.Results: Data from 345 climbers were analyzed. The incidence of AMS was 23.9% (95% confidence interval [CI] 19.5%–28.7%) and 21.7% (95% CI 17.5%–26.3%) on days 1 and 2, respectively. The majority were mild cases. Experiencing AMS on day 1 (odds ratio [OR] = 12.88; 95% CI 6.71–24.75), alcohol consumption (OR = 3.73; 95% CI 1.66–8.39), receiving guide advice on day 1 (OR = 0.49; 95% CI 0.26–0.93), and age (OR = 0.96; 95% CI 0.93–0.99) were significant determinants of AMS at Mount Kinabalu. Gender, history of AMS, past exposure to high altitude, ascending time, water intake, acetazolamide use, physical fitness, pulse rate, and peripheral capillary oxygen saturation (SpO2) were not associated with AMS at Mount Kinabalu.Conclusion: Future analysis with age strata is required to ascertain the association of age with AMS. Our research has signposted a strong call for collaborative efforts to improve the provision of hiking advice and discourage alcohol sales to mitigate the risk of AMS among Mount Kinabalu climbers.

Pre-acclimation, Training, And Nutrition For 14-day Lightning Summit Of Mt. Everest

Typical acclimatization protocols for summiting Mt. Everest involve sleeping and hiking at successively higher altitudes for more than 45 days. Prolonged exposure to hypoxia on the mountain increases the risk for Acute Mountain Sickness, hypothermia, accidents and non-successful summits. Reducing the time of exposure could decrease this risk and improve summit success. PURPOSE: This study examined the efficacy of a pre-trip acclimation training protocol for completing a novel 14-day rapid ascent of Mt. Everest. METHODS: This was a 12-week case study design examining nutrition, exercise training and hypoxia exposure from a single healthy experienced female mountaineer (Age 33 yrs) preparing to summit Mt. Everest. Pre-post measurements of body composition via DXA, heart rate (HR), SpO2, sleep quality, hematology (hematocrit & hemoglobin), graded exercise test, and nutritional intake values were analyzed. RESULTS: Simulated hypoxia gradually increased from 1800 to 5800 m over the 12 weeks (13.9 ± 0.9 hr/day). Over the 12 week protocol hypoxia tent HR increased from 52 to 64 bpm and SpO2 decreased from 93 to 77%. Lake Louise AMS symptoms were mild at 0.5 ± 0.6 on a scale of 0-3. Blood Hb increased from 13.3 to 17.6 g/dl and Hct from 42.9 to 52.5 % from baseline to summit day. Body mass (61.6 to 52.5 kg), body fat (26.6 to 15.3%), fat free mass (43.2 to 42.7 kg), and fat mass (16.4 to 8.1 kg) decreased over the 12 weeks. Fat utilization increased and carbohydrate utilization and blood lactate decreased across absolute workloads post-acclimation. Average daily energy intake was 1902 ± 18 kcals which consisted of 1.8 ±0.3 CHO g/kg/day, 1.9 ± 0.2 FAT g/kg/day and 2.4 ± 0.2 PRO g/kg/day. In addition, 7 days of intermittent fasting during light exercise days (16-20 hrs) and 25 sessions of post-exercise 20-40 min sauna exposure occurred during the 12-week period. On May 10, 2019 (Day 1) the subject traveled from San Francisco to Everest Base Camp (5200m) (Day 2). The subject spent the next 7 days acclimatizing at altitudes of 5200-7500 m. On May 22, 2019 (Day 12) the subject successfully summited Mt. Everest (8848 m) and arrived back at the airport in Tibet on Day 13, arriving back in San Francisco on May 24th. CONCLUSION: A 12-week pre-acclimation protocol at sea level successfully prepared the subject to summit Mt. Everest in 14 days.

Effect Of Heat Acclimation On Incidence Of Acute Mountain Sickness During Exposure To Hypobaric Hypoxia (3,500 M)

INTRODUCTION: Adaptations gained from heat acclimation (HA) can induce protective responses to a different stressor, such as hypoxia. Rapid ascent to altitude (hypobaric hypoxia, HH) increases the risk for acute mountain sickness (AMS). However, it is unknown whether HA can protect against the development of AMS during exposure to HH. PURPOSE: To determine if prior HA reduces the incidence of AMS during a 30 hour exposure to HH (3,500 m). METHODS: Thirteen unacclimatized healthy men (mean ± SD; age: 21 ± 3 yr; ht: 172 ± 8 cm; wt: 75.1 ± 12.2 kg; sea level VO2peak 42.9 ± 4.6 ml·kg-1·min-1) participated in three study phases consisting of: Phase 1) baseline (pre HA) 30 hour HH exposure (HH1; 3,500 m), Phase 2) 14-day washout period during which volunteers completed an 8-day exercise-HA protocol (treadmill walking: 120 minutes at 5 km·hr-1, 2% grade; 40°C and 40% RH), and Phase 3) post HA 30 hour HH exposure (HH2). During the HA protocol, heart rate (HR) and core temperature (Tc) were recorded throughout exercise. AMS was assessed using the Environmental Symptoms Questionnaire after ~12, ~21, and ~23 hours of exposure during each HH phase. HR and pulse oxygen saturation (SpO2) were measured at rest immediately after assessment of AMS. A t-test was used to assess difference in HR and Tc from Day 1 and Day 8 of HA. For the HH exposures, HR and SpO2 data were analyzed by fitting a mixed effects model as implemented by GraphPad Prism 8.1.2. RESULTS: Heat acclimation was achieved as indicated by a lower Tc (Day 1: 38.1 ± 0.3 vs Day 8: 37.8 ± 0.3 °C; p<0.01) and HR (Day 1: 134 ± 17 vs Day 8: 121 ± 13 bpm; p<0.01) at the end of exercise on Day 8 compared to Day 1. Three of 13 volunteers developed AMS during HH1 but not during HH2. A fourth volunteer only developed AMS during HH2. From HH1 to HH2, resting HR (84 ± 6 vs 83 ± 7 bpm) and SpO2 (87 ± 2 vs 88 ± 2%) were not different (both p >0.05). CONCLUSION: Our results suggest that in unacclimatized individuals, HA may be an effective, though not perfect training strategy for reducing the incidence of AMS during rapid exposure to 3,500 m. Changes in AMS incidence could not be explained by alterations in HR or SpO2. Supported by USAMRDC; author views not official US Army or DoD policy.

A Randomized Controlled Trial of the Lowest Effective Dose of Acetazolamide for Acute Mountain Sickness Prevention

BackgroundAcetazolamide is the most common medication used for acute mountain sickness prevention, with speculation that a reduced dose may be as efficacious as standard dosing with fewer side effects. MethodsThis double-blind, randomized, controlled noninferiority trial compared acetazolamide 62.5 mg twice daily to the standard dose acetazolamide 125 mg twice daily starting the evening prior to ascent from 1240 m (4100 ft) to 3810 m (12,570 ft) over 4 hours. The primary outcome was acute mountain sickness incidence (ie, headache, Lake Louise Questionnaire ≥3, and another symptom). ResultsA total of 106 participants were analyzed, with 51 (48%) randomized to 125 mg and 55 (52%) to 62.5 mg, with a combined acute mountain sickness incidence of 53 (50%) and mean severity of 3 (± 2.1). The 62.5-mg group failed to fall within the prespecified 26% noninferiority margin for acute mountain sickness incidence (62.5 mg = 30 [55%] vs 125 mg = 23 [45%], 95% confidence interval [CI] -11% to 30%). Participants in the 62.5-mg group had a higher risk of acute mountain sickness (odds ratio = 1.5, 95% CI 0.7-3.2) and moderate acute mountain sickness (odds ratio = 1.8, 95% CI 0.6-5.9), with a number needed to harm (NNH) of 9, with a number needed to treat (NNT) in the 125-mg group of 4.8. Increased acute mountain sickness incidence and symptom severity corresponded to lower weight-based and body mass index dosing, with similar side effects between groups. ConclusionAcetazolamide 62.5 mg twice daily failed to demonstrate equal effectiveness to 125 mg twice daily for prevention of acute mountain sickness. With increased risk and no demonstrable symptomatic or physiologic benefits, acetazolamide 62.5 mg twice daily should not be recommended for acute mountain sickness prevention.

Hypertension and Acute Mountain Sickness in Himalayan Trekkers in Nepal: An Observational Cohort Study

A history of preexisting hypertension is common in people participating in mountain activities; however, the relationship between blood pressure (BP), preexisting hypertension, and acute mountain sickness (AMS) is not well studied. We sought to determine these relationships among trekkers in the Everest region of Nepal. This was a prospective observational cohort study of a convenience sample of adult, nonpregnant volunteers trekking in the Everest Base Camp region in Nepal. We recorded Lake Louise Scores for AMS and measured BP at 2860 m, 3400 m, and 4300 m. The primary outcome was AMS. A total of 672 trekkers (including 60 with history of preexisting hypertension) were enrolled at 2860 m. We retained 529 at 3400 m and 363 at 4300 m. At 3400 m, 11% of participants had AMS, and 13% had AMS at 4300 m. We found no relationship between AMS and measured BP values (P>0.05), nor was there any relation of BP to AMS severity as measured by higher Lake Louise Scores (P>0.05). Preexisting hypertension (odds ratio [OR] 0.16; 95% CI 0.025-0.57), male sex (OR 0.59; 95% CI 0.37-0.96), and increased SpO2 (OR 0.93; 95% CI 0.87-0.98) were associated with reduced rates of AMS in multivariate analyses adjusting for known risk factors for AMS. AMS is common in trekkers in Nepal, even at 3400 m. There is no relationship between measured BP and AMS. However, a medical history of hypertension may be associated with a lower risk of AMS. More work is needed to confirm this novel finding.