Risk Determinants of Acute Mountain Sickness and Summit Success on a 6-Day Ascent of Mount Kilimanjaro (5895 m)

Pushing Scuba to New Heights: Approach, Decompression, and Logistical Considerations for High-Altitude Diving

There is interest among technical, expedition, commercial, and military divers in expanding diving operations to high altitude. However, altitude diving presents unique challenges including acclimatization, increased decompression sickness (DCS) risk, and logistical and equipment considerations. Divers must plan altitude acclimatization strategies conservatively to reduce risk of acute mountain sickness and dehydration before diving. Several methods of augmenting sea level diving tables to be used at altitude have been theorized and tested both in simulated dives and high-altitude expeditions. With proper acclimatization, augmentation of standard diving tables, equipment, and safety planning, diving at high altitude may be performed in many contexts safely while minimizing risk of DCS or injury.

Altitude illnesses

Millions of people visit high-altitude regions annually and more than 80 million live permanently above 2,500 m. Acute high-altitude exposure can trigger high-altitude illnesses (HAIs), including acute mountain sickness (AMS), high-altitude cerebral oedema (HACE) and high-altitude pulmonary oedema (HAPE). Chronic mountain sickness (CMS) can affect high-altitude resident populations worldwide. The prevalence of acute HAIs varies according to acclimatization status, rate of ascent and individual susceptibility. AMS, characterized by headache, nausea, dizziness and fatigue, is usually benign and self-limiting, and has been linked to hypoxia-induced cerebral blood volume increases, inflammation and related trigeminovascular system activation. Disruption of the blood-brain barrier leads to HACE, characterized by altered mental status and ataxia, and increased pulmonary capillary pressure, and related stress failure induces HAPE, characterized by dyspnoea, cough and exercise intolerance. Both conditions are progressive and life-threatening, requiring immediate medical intervention. Treatment includes supplemental oxygen and descent with appropriate pharmacological therapy. Preventive measures include slow ascent, pre-acclimatization and, in some instances, medications. CMS is characterized by excessive erythrocytosis and related clinical symptoms. In severe CMS, temporary or permanent relocation to low altitude is recommended. Future research should focus on more objective diagnostic tools to enable prompt treatment, improved identification of individual susceptibilities and effective acclimatization and prevention options.

Acute Mountain Sickness and High Altitude Cerebral Edema in Women: A Scoping Review-UIAA Medical Commission Recommendations

Derstine, Mia, Dominique Jean, Beth A. Beidleman, Jacqueline Pichler Hefti, David Hillebrandt, Lenka Horakova, Susi Kriemler, Kasté Mateikaité-Pipiriené, Peter Paal, Alison Rosier, Marija Andjelkovic, and Linda E. Keyes. Acute mountain sickness and high altitude cerebral edema in women: A scoping review-UIAA Medical Commission recommendations. High Alt Med Biol. 24:259-267, 2023. Background: Acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) are illnesses associated with rapid ascent to altitudes over 2,500 m in unacclimatized lowlanders. The aim of this scoping review is to summarize the current knowledge on sex differences in the epidemiology, pathophysiology, symptomatology, and treatment of AMS and HACE, especially in women. Methods and Results: The UIAA Medical Commission convened an international author team to review women's health issues at high altitude and to publish updated recommendations. Pertinent literature from PubMed and Cochrane was identified by keyword search combinations (including AMS, HACE, and high altitude), with additional publications found by hand search. The primary search focus was for articles assessing lowland women sojourning at high altitude. Results: The literature search yielded 7,165 articles, 37 of which were ultimately included. The majority of publications included did not find women at increased risk for AMS or HACE. There was extremely limited sex-specific data on risk factors or treatment. Conclusions: There is a limited amount of data on female-specific findings regarding AMS and HACE, with most publications addressing only prevalence or incidence with regard to sex. As such, general prevention and treatment strategies for AMS and HACE should be used regardless of sex.

Incidence and predictors of severe altitude illness symptoms in Mt. Kilimanjaro hikers: a prospective cohort study

BACKGROUND

Each year several Mt. Kilimanjaro hikers die due to altitude illness (AI) although urgent descent is technically easily possible. The objectives of this study were to determine the incidence and predictors of severe altitude illness (SAI) symptoms and of summit success in Mt. Kilimanjaro hikers, and the measures taken when AI symptoms develop.

METHODS

A prospective observational cohort study in Mt. Kilimanjaro hikers was conducted from December 2019 until March 2020. Participants were asked to complete a questionnaire at the entrance gate and one at the descend gate. A multivariate logistic regression was performed to study the relations between the variables.

RESULTS

A total of 1237 recreational hikers and 266 porters or guides were included. The incidence of severe symptoms was 8.6% in recreational hikers and 1.5% in porters and guides. One percent (1.1%) of hikers was hospitalized due to SAI. A history of SAI, young age, summit failure and lack of clear advice predicted the development of severe symptoms. Uhuru peak was reached by 87.9% of the hikers. Absence of severe symptoms, acetazolamide prophylaxis, climbing higher in daytime, young age and climbing in more days predicted summit success. The majority climbed further despite the presence of mild or severe symptoms. The only measure taken in case of mild symptoms that was associated with a lower incidence of severe symptoms was not climbing further.

CONCLUSION

The incidence of SAI symptoms in Mt. Kilimanjaro hikers was observed to be high. However, how hikers reacted during symptoms was not appropriate. Therefore, travel health counsellors should emphasize even more that hikers do not ascend higher until mild symptoms have resolved and that it is vital to descend immediately when severe symptoms develop. In addition, they can be informed on the measures, which improved summit success.

Training and certification in first responder care among mountaineering practitioners in east Africa

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In mountaineering, within East Africa, medical care may be very far away from the emergency scenes, and hence the tier one emergency care system may be offered by the mountaineering practitioners.

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There is limited research in the first responder care programmes in the mountaineering wilderness environments in Africa.

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Competency in first responder care through training and certification is part of safety promotion, a factor that can offer more confidence and appeal to tourists towards participation in mountaineering activities in Africa.

Introduction

Mountaineering activities have potential risks for injuries and illnesses. Extreme weather conditions, high altitude, limited resources and accessibility to transport and definitive medical services calls for mountaineering practitioners to be well prepared through training and certification in first responder care. This is useful in cases when they have an injured climber and need to offer support in the tier-one emergency system care before accessing further care in a medical facility. The study sought to establish the first responder care training status of mountaineering practitioners and the associations of mountaineering practitioners’ first responder care training levels and gender, age, years of work experience, and designation.

Methods

The study used cross-sectional analytical research design with a purposive sample of one hundred and thirty six (136) mountaineering practitioners in East Africa. Snowball sampling procedure was used to identify the respondents since there were no records indicating the population size or specific location of these mountaineering practitioners. A self-administrated questionnaire was used to collect data on whether they were trained or not; status of their up-to-date certification; institutions where they did their training and recertification; and their training levels in first responder care, which would cover the aim of the study.

Results

Majority of mountaineering practitioners (91.2%) had received some form of training. However, 47.1% had received training in basic first aid, which did not involve mountain related components. Outdoor practitioners’ up-to-date training was dependent on their age (p = 0.005), and years of work experience (p= 0.014).

Discussion

There is need for mountaineering practitioners to have standardized minimum training in wilderness specific first responder care. The study recommends that the training and recertification should be undertaken on a regular basis by the mountaineering practitioners in East Africa.

Poor Knowledge of Acute Mountain Sickness in Latin American Medical Students

INTRODUCTION

Acute altitude exposure is a common event in Latin America that can result in mild to severe altitude illness. Medical students from some Latin American countries receive little information on this topic. Our aim was to determine the knowledge and incidence of acute mountain sickness (AMS), as well as the methods used to prevent AMS among medical students attending the Pan-American Student Meeting in Cusco, Peru, a city at high altitude (3400 m).

METHODS

We conducted a cross-sectional study on medical students attending a conference. Participants completed a questionnaire on the day of registration that collected demographic data and investigated students' knowledge of AMS, its prophylaxis, and their personal experience of symptoms.

RESULTS

A total of 840 students attended the meeting. Two hundred eighty-eight returned surveys, 51 from high altitude locations. Respondent age was 23±3 y (mean±SD), and 72% were female. Thirty-two percent had basic knowledge about symptoms of AMS. Headache was recognized as a symptom by 79%. Knowledge of AMS prophylaxis was reported by 70%. Coca leaf products and dimenhydrinate were mentioned by 30 and 16%, respectively, whereas acetazolamide was recognized by only 10% of participants. AMS incidence was 42%. Prophylactic measures were adopted by 47% of the participants in our study. Thirty-six percent used dimenhydrinate and 27% used coca tea. Less than 1% used acetazolamide as recommended.

CONCLUSIONS

We found poor knowledge of AMS and effective prophylaxis among medical students from several South American countries traveling to 3400 m.

Preliminary Evidence-Based Method of Medical Kit Design for Wilderness Expeditions Modeled by a High-Altitude Expedition to Mount Kilimanjaro

BACKGROUND

Wilderness expeditions require extensive planning and the correct medical supplies to ensure clinical care is possible in the event of illness or injury. There are gaps in the literature regarding evidence-based methods for medical kit design.

OBJECTIVES

This report describes a preliminary method for predicting medical events to determine medical supply requirements for a wilderness expedition. The performance of this method was evaluated using data from the 2017 Equal Playing Field (EPF) expedition to Mount Kilimanjaro.

METHODS

Eight reports documenting medical events during wilderness expeditions were reviewed. Incidence data were consolidated into a new dataset, and a subset of data from adventure race expeditions (ARS) was created. The cumulative incidence of medical events was then predicted for the 9-day EPF expedition. The medical supply list was determined based on indication. The effectiveness of the full dataset and ARS to predict the cumulative incidence of medical events by category during the EPF expedition was evaluated using regression analysis.

RESULTS

The ARS predicted a higher incidence rate of medical events than the full dataset did but underestimated the EPF expedition incidence rate. The full dataset was a weak predictor of the cumulative incidence of medical events by category during the EPF expedition, while the ARS was a strong predictor. The finalized medical kit overestimated all nonreusable supplies.

CONCLUSIONS

The medical kit created using this method managed all medical events in the field. This report demonstrates the potential utility of using a tailored, evidence-based approach to design a medical kit for wilderness expeditions.

Older Age as a Predictive Risk Factor for Acute Mountain Sickness

BACKGROUND

Older populations are increasing and comprise a substantial portion of high-altitude travelers. Aging physiology may influence susceptibility to acute mountain sickness, though prior research remains inconclusive. The goal of this study was to investigate the relationship between increasing age and acute mountain sickness.

METHODS

This study was a pooled analysis of 5 prospective randomized controlled trials conducted at White Mountain, California from 2010, 2016-2019 with identical 4-hour rapid ascent from 1242 m to overnight sojourn at 3810 m. Acute mountain sickness was defined by the 2018 Lake Louise Questionnaire criteria.

RESULTS

There were 491 participants analyzed, 234 (48%) diagnosed with acute mountain sickness and 71 (14%) with moderate acute mountain sickness. Mean age was 37 years (±13). There was no significant correlation between Lake Louise Questionnaire severity and age (r = -0.02; 95% confidence interval [CI], -0.11-0.07, P = .7), 40-year-old dichotomy (t = -0.6; 95% CI, -0.53-0.28, P = .6), or decade of life (P = .4). Logistic regression found no increased odds of acute mountain sickness for increasing age by decade of life (odds ratio [OR] 1.0; 95% CI, 0.97-1.0) or 40-year-old dichotomy (OR 1.4; 95% CI, 0.97-2.1). A history of acute mountain sickness increased odds of acute mountain sickness (OR 3.2; 95% CI, 1.5-7.7).

CONCLUSIONS

Older age was not associated with incidence nor severity of acute mountain sickness. A history of altitude illness increased odds of acute mountain sickness and should be used for pre-ascent risk stratification.

Altitude-Related Disorders on Mount Kilimanjaro, Tanzania: Two-Year Survey in a Local Referral Center

INTRODUCTION

A significant number of climbers on Mount Kilimanjaro are affected by altitude-related disorders. The aim of this study was to determine the main causes of morbidity and mortality in a representative cohort of climbers based on local hospital records.

METHODS

We conducted a 2-y retrospective chart review of all patients presenting to the main referral hospital in the region after a climb on Mount Kilimanjaro, including all relevant records and referrals for postmortem studies.

RESULTS

We identified 62 climbers who presented to the hospital: 47 inpatients and 15 outpatients. Fifty-six presented with high altitude illness, which included acute mountain sickness (n=8; 14%), high altitude pulmonary edema (HAPE) (n=30; 54%), high altitude cerebral edema (HACE) (n=7; 12%), and combined HAPE/HACE (n=11; 20%). The mean altitude of symptom onset ranged from 4600±750 m for HAPE to 5000±430 m for HAPE/HACE. The vast majority of inpatients (n=41; 87%) were improved on discharge. Twenty-one deceased climbers, most having died while climbing (n=17; 81%), underwent postmortem evaluation. Causes of death were HAPE (n=16; 76%), HAPE/HACE (n=3; 14%), trauma (1), and cardiopulmonary (1).

CONCLUSIONS

HAPE was the main cause of death during climbing as well as for hospital admissions. The vast majority of climbers who presented to hospital made a full recovery.

Does age have an impact on acute mountain sickness? A systematic review

Acute mountain sickness (AMS) is the most common form of illness at high altitude; however, it is still unclear whether age is a protective factor or a risk factor for the development of AMS in travellers. In recent decades, the number of travellers aged 60 years or older is increasing. Thus, the care of older travellers is a long-standing issue in travel medicine. This study aims to systematically review the current state of knowledge related to the effect of old age on the risk of AMS. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used, and the following databases were consulted: PubMed/Medline, Embase, Europe PubMed Central (EuropePMC), World Health Organization Library Database (WHOLIS) and Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS). The search yielded a total of 532 articles, of which 25 met the inclusion criteria, corresponding to 26 reports. Although the approaches, methods and quality were heterogeneous among the included studies, 12 reported a negative correlation between AMS prevalence and age, 11 detected no relationship and three papers indicated that the age of AMS subjects was significantly higher than controls. Despite these differences, old age does not seem to be a contraindication for travelling at high altitude. Thus, the presented synthesis will be useful for health professionals in travel medicine to better tailor their appropriate care for older adults who travel to destinations at high altitude.

Early adjustments in mitochondrial structure and function in skeletal muscle to high altitude: design and rationale of the first study from the Kilimanjaro Biobank

The physiological acclimatisation and adaptation processes in skeletal muscle at high altitude are of high medical and social relevance not only to understand limitations in physical performance at high altitude but also to understand the consequences of hypoxemia and tissue hypoxia in critically ill patients. Of particular importance in these processes are the alterations in content and function of mitochondria and myoglobin. The majority of studies on oxygen delivery to the tissues and utilisation by the cellular metabolism at high altitude were performed after prolonged stay at high altitude and in altitude-adapted highlanders. However, these studies do not provide insight in the sequence of events during the physiological acclimatisation and adaptation processes. Therefore, it is important to identify the early alterations in structure and function of the major determinants of the oxygen transport via myoglobin and oxygen utilisation by the mitochondria in skeletal muscle at high altitude. To achieve this goal, it is of interest to collect, analyse and compare quadriceps muscle biopsies and venous blood samples of climbers, guides and porters before and after climbing Mount Kilimanjaro and in participants of the Kilimanjaro Marathon before and after the run. The samples will be carefully documented and stored in the Kilimanjaro Biobank and will be made available to other research groups.

New metric of hypoxic dose predicts altitude acclimatization status following various ascent profiles

Medical personnel need practical guidelines on how to construct high altitude ascents to induce altitude acclimatization and avoid acute mountain sickness (AMS) following the first night of sleep at high altitude. Using multiple logistic regression and a comprehensive database, we developed a quantitative prediction model using ascent profile as the independent variable and altitude acclimatization status as the dependent variable from 188 volunteers (147 men, 41 women) who underwent various ascent profiles to 4 km. The accumulated altitude exposure (AAE), a new metric of hypoxic dose, was defined as the ascent profile and was calculated by multiplying the altitude elevation (km) by the number of days (d) at that altitude prior to ascent to 4 km. Altitude acclimatization status was defined as the likely presence or absence of AMS after ~24 h of exposure at 4 km. AMS was assessed using the Cerebral Factor Score (AMS-C) from the Environmental Symptoms Questionnaire and deemed present if AMS-C was ≥0.7. Other predictor variables included in the model were age and body mass index (BMI). Sex, race, and smoking status were considered in model development but eliminated due to inadequate numbers in each of the ascent profiles. The AAE (km·d) significantly (P < 0.0001) predicted AMS in the model. For every 1 km·d increase in AAE, the odds of getting sick decreased by 41.3%. Equivalently, for every 1 km·d decrease in AAE, the odds of getting sick increased by 70.4%. Age and BMI were not significant predictors. The model demonstrated excellent discrimination (AUC = 0.83 (95% CI = 0.79-0.91) and calibration (Hosmer-Lemeshow = 0.11). The model provides a priori estimates of altitude acclimatization status resulting from the use of various rapid, staged, and graded ascent profiles.

Mountain neurology

Mountain climbers may develop specific illnesses that largely depend on the altitude reached and the rate of ascent. The popularity of travel to high altitude destinations, extreme tourist activities and mountain climbing means that neurologists in low-altitude countries are increasingly likely to encounter neurological problems and disorders in people exposed to high altitude. Additionally, they may have to advise patients with pre-existing neurological conditions on the risks of ascent to altitude. This article focuses on neurological-related high-altitude illnesses: acute mountain sickness and high-altitude cerebral oedema, as well as high-altitude retinopathy and other neurological disorders. This overview combines current understood pathogenesis with the experience of managing altitude-related illness at the foot of Mount Kilimanjaro in northern Tanzania, the tallest free-standing mountain in the world.

Does This Patient Have Acute Mountain Sickness?: The Rational Clinical Examination Systematic Review

IMPORTANCE

Acute mountain sickness (AMS) affects more than 25% of individuals ascending to 3500 m (11 500 ft) and more than 50% of those above 6000 m (19 700 ft). AMS may progress from nonspecific symptoms to life-threatening high-altitude cerebral edema in less than 1% of patients. It is not clear how to best diagnose AMS.

OBJECTIVE

To systematically review studies assessing the accuracy of AMS diagnostic instruments, including the visual analog scale (VAS) score, which quantifies the overall feeling of sickness at altitude (VAS[O]; various thresholds), Acute Mountain Sickness-Cerebral score (AMS-C; ≥0.7 indicates AMS), and the clinical functional score (CFS; ≥2 indicates AMS) compared with the Lake Louise Questionnaire Score (LLQS; score of ≥5).

DATA EXTRACTION AND SYNTHESIS

Searches of MEDLINE and EMBASE from inception to May 2017 identified 1245 publications of which 91 were suitable for prevalence analysis (66 944 participants) and 14 compared at least 2 instruments (1858 participants) using a score of 5 or greater on the LLQS as a reference standard. To determine the prevalence of AMS for establishing the pretest probability of AMS, a random-effects meta-regression was performed based on the reported prevalence of AMS as a function of altitude.

MAIN OUTCOMES AND MEASURES

AMS prevalence, likelihood ratios (LRs), sensitivity, and specificity of screening instruments.

RESULTS

The final analysis included 91 articles (comprising 66 944 study participants). Altitude predicted AMS and accounted for 28% of heterogeneity between studies. For each 1000-m (3300-ft) increase in altitude above 2500 m (8200 ft), AMS prevalence increased 13% (95% CI, 9.5%-17%). Testing characteristics were similar for VAS(O), AMS-C, and CFS vs a score of 5 or greater on the LLQS (positive LRs: range, 3.2-8.2; P = .22 for comparisons; specificity range, 67%-92%; negative LRs: range, 0.30-0.36; P = .50 for comparisons; sensitivity range, 67%-82%). The CFS asks a single question: "overall if you had any symptoms, how did they affect your activity (ordinal scale 0-3)?" For CFS, moderate to severe reduction in daily activities had a positive LR of 3.2 (95% CI, 1.4-7.2) and specificity of 67% (95% CI, 37%-97%); no reduction to mild reduction in activities had a negative LR of 0.30 (95% CI, 0.22-0.39) and sensitivity of 82% (95% CI, 77%-87%).

CONCLUSIONS AND RELEVANCE

The prevalence of acute mountain sickness increases with higher altitudes. The visual analog scale for the overall feeling of sickness at altitude, Acute Mountain Sickness-Cerebral, and clinical functional score perform similarly to the Lake Louise Questionnaire Score using a score of 5 or greater as a reference standard. In clinical and travel settings, the clinical functional score is the simplest instrument to use. Clinicians evaluating high-altitude travelers who report moderate to severe limitations in activities of daily living (clinical functional score ≥2) should use the Lake Louise Questionnaire Score to assess the severity of acute mountain sickness.

Incidence and severity of acute mountain sickness and associated symptoms in children trekking on Xue Mountain, Taiwan

BACKGROUND

Acute mountain sickness (AMS) occurs in non-acclimatized people after an acute ascent to an altitude of 2,500 m or higher. The aim of this study was to examine the incidence and severity of AMS and associated symptoms in children.

METHODS

The prospective observational study included 197 healthy, non-acclimatized 11 and 12-year-old children trekking the round-trip from the trailhead to the summit of Xue Mountain, Taiwan (2,179 m to 3,886 m) over 3 days. AMS was evaluated at Qika Hut (2,460 m) on Day 1, at Sanliujiu Hut on Day 2 (3,100 m), and at the same altitude (3,100 m) after reaching the summit on Day 3. We used the Lake Louise Score (LLS) to diagnose AMS and record daily AMS-associated symptoms. We gave acetazolamide to children with mild to moderate AMS. Dexamethasone was reserved for individuals suffering from severe AMS. Acetaminophen was administrated to children with headache, and metoclopramide for those with nausea or vomiting.

RESULTS

There were 197 subjects eligible for analysis. The overall incidence of AMS was 40.6%, which was higher in males and in subjects with a higher body mass index (BMI) (p < 0.05). The prevalence of AMS on Day 1 was 5.6%, which was significantly lower than that on Day 2 (29.4%) and Day 3 (23.4%). The mean LLS of all subjects was 1.77 ± 2.08. The overall incidence of severe AMS (LLS ≥ 5) was 12.5%. The mean LLS of the AMS group (3.02 ± 2.46) was significantly higher than that of the non-AMS group (0.92 ± 1.16, p < 0.001). Among the AMS group, the mean LLS was 1.00 ± 1.55 on Day 1, 4.09 ± 1.97 on Day 2, and 3.98 ± 2.42 on Day 3. The most common symptom was sleep disturbance followed by dizziness, and headache. The prevalence of headache was 46.2% on Day 2 at 3,100 m, and 31.3% on Day 3 at the same altitude after climbing the summit (3,886 m). Males experienced significantly more headache and fatigue than females (p < 0.05). The LLS and prevalence of all AMS symptoms were significantly higher in the AMS than the non-AMS group (p < 0.05).

CONCLUSIONS

The AMS incidence among children trekking to Xue Mountain was 40.6%. AMS is common and mostly manifests as mild symptoms. Gender (male) and a higher BMI could be considered two independent risk factors of higher AMS incidence. Sleep disturbance is the most common symptom, and the lower prevalence of headache on Day 3 may be due to the effects of medication and/or acclimatization.