Wilderness Medical Society Clinical Practice Guidelines for the Treatment of Acute Pain in Austere Environments: 2024 Update.

The Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for the management of pain in austere environments. Recommendations are graded based on the quality of supporting evidence as defined by criteria put forth by the American College of Chest Physicians. This is an update of the 2014 version of the "WMS Practice Guidelines for the Treatment of Acute Pain in Remote Environments" published in Wilderness & Environmental Medicine 2014; 25:41-49.

Cardiovascular Disease and Triathlon-Related Deaths in the United Kingdom.

INTRODUCTION: Triathlon is one of the fastest growing sports in the United Kingdom. However, in recent years several deaths have occurred. The intention of this study is to identify these cases and examine the role cardiovascular disease played in these deaths. METHODS: An extensive online search was performed to identify triathlon-related deaths (TRDs) in the United Kingdom and UK citizens who died during or as a result of competing in triathlons abroad. British Triathlon provided the number of participants who took part in UK-based events. Coroners provided information on all those who died. RESULTS: Between 2009 and 2015, 991,186 participants took part in British Triathlon-sanctioned events. Five TRDs in the United Kingdom were identified. The mortality rate was 0.5 per 100,000 participants. Deaths occurred during or after the swim (3), cycle (1), and run (1) events. During the same period, 5 TRDs were identified among UK citizens competing abroad. These deaths occurred during or after the swim (2), cycle (1), and run (2) events. Cardiovascular pathology was cited as a cause or contributing factor in half of the fatalities. Four deaths were referred to a specialist cardiac pathology service for autopsy. CONCLUSIONS: Cardiovascular disease was found to be the most common cause of TRD. Further research is needed to determine the underlying cardiac pathology that triggers TRDs. With this information it may be possible to develop screening tools that can prevent similar fatalities from occurring in the future.

Wilderness Medical Society practice guidelines for the treatment of acute pain in remote environments.

The Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the management of pain in austere environments. Recommendations are graded based on the quality of supporting evidence as defined by criteria put forth by the American College of Chest Physicians.

Wilderness Medical Society practice guidelines for the treatment of acute pain in remote environments: 2014 update.

The Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the management of pain in austere environments. Recommendations are graded on the basis of the quality of supporting evidence as defined by criteria put forth by the American College of Chest Physicians. This is an updated version of the original WMS Practice Guidelines for the Treatment of Acute Pain in Remote Environments published in Wilderness & Environmental Medicine 2014;25(1):41-49.

Sleep disturbance at altitude.

PURPOSE OF REVIEW: The aim is to describe the impact of altitude upon sleep, the physiology that underpins these changes and the therapeutic solutions that are currently in place. RECENT FINDINGS: On ascending to altitude, lowland residents commonly experience some degree of sleep disturbance. Occasionally, this can prove very uncomfortable and impact upon daytime activities. Historically, the underlying cause of sleep disturbance was thought to be due to the effect of periodic breathing. However, recent research has shown that the link between periodic breathing, lighter stages of sleep and arousals is far from convincing. Instead, it appears that hypoxia has a far wider effect upon sleep at altitude than was previously thought. A number of new approaches to the treatment of sleep disturbance at altitude have recently been identified. Whereas some treat the underlying hypoxia through pharmacological or technological means, others seek to address the symptoms of sleep disturbance more directly. SUMMARY: Many of the current approaches to treating sleep disturbance at altitude have been shown to be well tolerated and successful, although few comparisons have been made. Future research is likely to focus upon matching the safest and most successful approach to the individual and their environment.

Raymond Greene: physician, mountaineer, and raconteur.

C. Raymond Greene (1901-1982) was a man of many talents. After graduating from medical school in 1927, he spent a decade in general practice. He subsequently became heavily involved in the emerging specialty of endocrinology and went on to gain considerable recognition in the treatment of thyroid disorders before eventually becoming involved in the world of medical publishing. Aside from Greene's mainstream vocational and intellectual pursuits, from boyhood he nurtured a passionate interest in mountaineering--first in his native Great Britain, and then the European Alps, and ultimately in the high Himalayas. His involvement in landmark climbs, such as the successful Kamet venture in 1931 and Everest attempt in 1933, earned him a place in the pantheon of Himalayan explorers and mountaineers and stimulated Green's interest in high altitude physiology and medicine. He made notable additions to the literature on this subject in publications such as Nature and Journal of Physiology. Apart from his remarkable life achievements in the areas of medicine, mountaineering, and publishing, Greene was perhaps best remembered by those close to him (and by contemporary readers who are devotees of his writing) as a peerless storyteller with a sardonic sense of irony.

Improving sleep at altitude: a comparison of therapies.

OBJECTIVE: This study aimed to compare 3 treatment modalities during sleep at an altitude of 5300 m to identify strategies for reducing the incidence of periodic breathing at high altitude. METHODS: Fifteen trekkers, with identical ascent profiles and no signs or symptoms of altitude illness, served as subjects. All study participants arrived at 5300 m after a gradual ascent from 1300 m. On their second night at 5300 m, subjects were randomly assigned (with a computer-based random assignment procedure) to 1 of 4 different treatment groups: control (n = 4); 1 L/min O(2) via a demand system during sleep (n = 3); 1 L/min O(2)/CO(2) mix (1.5% CO(2)) via a demand system during sleep (n = 4); or 125 mg acetazolamide 30 minutes before bedtime (n = 4). Heart rate, respiration rate, blood oxygen saturation, tidal volume, minute volume, and apnea hypopnea index were measured. RESULTS: Upon comparing the 4 groups, there were no statistically significant differences between the variables. One-way analysis of variance indicated a trend toward statistical significance for SaO(2) between groups (F = 2.9, P = .08), and Tukey Honestly Significant Difference (HSD) post hoc tests indicated a trend in the SaO(2) difference between the 1 L/min oxygen and control groups (P = .07). While 1-way analysis of variance suggested no difference for respiratory rate between groups (F = 2.5, P = .1), Tukey HSD indicated a trend in statistical difference of the respiratory rate between 1 L/min O(2) and 1 L/min O(2)/CO(2) mixture (P = .08). CONCLUSIONS: These statistical trends found between control and treatment groups indicate that further study is warranted.

Oxygen on Everest: the development of modern open-circuit systems for mountaineers.

The use of supplemental oxygen on Mt. Everest is now commonplace. From 1990 to 2006, more than 95% of those summiting the mountain did so using supplemental oxygen at some point during their ascent. The open circuit systems currently in use can be traced back to the device first used by George Finch on Mt. Everest in 1922. Wearing equipment weighing 33 lb (15 kg), Finch and his colleague Geoffrey Bruce set a world altitude record by reaching a height of 27,250 ft (8175 m). However, it would be with a lighter system weighing just 22 lb (10 kg) that Sir Edmund Hillary and Tenzing Norgay made the first ascent of the mountain in 1953. In the years since then considerable improvements in weight, comfort, and efficiency have been made; however, the original "open" principles first used by Finch almost a century ago still remain steadfastly in place.

Heights and haematology: the story of haemoglobin at altitude.

In order to compensate for the low partial pressure of oxygen at altitude, the human body undergoes a number of physiological changes. A vital component in this process is the increase in the concentration of circulating haemoglobin. The role of HIF-1alpha, erythropoietin and red blood cells in this acclimatisation process is described, together with the fall in plasma volume that increases the concentration of haemoglobin in the early stages of hypoxic exposure.

Supplemental oxygen effects on ventilation in acclimatized subjects exercising at 5700 m altitude.

INTRODUCTION: This study examines the effect of supplemental oxygen on acclimatized mountaineers at high altitude during rest and submaximal exercise. METHODS: Three healthy, acclimatized participants undertook nine periods of data collection lasting 10 min each over 2 consecutive days at 5700 m. These occurred at rest and exercise (40 and 80 W), breathing ambient air or supplemental oxygen (2 and 4 L m min') through an open-circuit breathing system. RESULTS: As minute ventilation increased during exercise, the fraction of inspired oxygen (FIO2) fell from 0.31 at rest to 0.23 with 2 L x min(-1) of oxygen and from 0.36 to 0.26 with 4 L x min(-1). Oxygen at both flow rates resulted in a significant increase in the arterial blood saturation of oxygen (SaO2) (Rest: 79% to 96% to 97%; 40 W: 80% to 95% to 97%; 80 W: 76% to 94% to 98%) and reduction in respiratory rate (RR) (Rest: 28 to 22 to 24; 40 W: 36 to 25 to 25; 80 W: 41 to 26 to 26). Tidal volume (VT, ml x s(-1)) was found to increase with the addition of oxygen (Rest: 959 to 844 to 969; 40 W: 1393 to 1834 to 1851; 80 W: 1558 to 2105 to 2215) and resulted in a non-significant reduction in minute ventilation (VE, L) (Rest: 25 to 17 to 21; 40 W: 46 to 45 to 43; 80 W: 61 to 51 to 53). No significant changes in heart rate were observed when oxygen was used (Rest: 78 to 62 to 71; 40 W: 90 to 91 to 96; 80 W: 105 to 102 to 101). CONCLUSION: An open-circuit breathing system may increase SaO2 and reduce RR in acclimatized mountaineers during rest and sub-maximal exercise at 5700 m, though further research is needed to confirm this.

Supplemental oxygen and hyperbaric treatment at high altitude: cardiac and respiratory response.

INTRODUCTION: The most effective treatment for high altitude sickness is prompt descent. However, rapid descent is sometimes impossible and alternative solutions are desirable. Supplemental oxygen at ambient pressure and hyperbaric oxygen in a hyperbaric tent have both been demonstrated to improve symptoms and increase arterial oxygenation (SaO2) in those with high altitude sickness; however, their use in combination has not previously been described in a controlled study. METHODS AND RESULTS: In this feasibility study, the SaO2 of six healthy, well-acclimatized participants rose from 76.5 to 97.5% at 4900 m and 72.5 to 96.0% at 5700 m following the administration of oxygen via a nasal demand circuit (33 ml of oxygen per pulse) inside a hyperbaric tent (107 mmHg above ambient barometric pressure) (p < 0.05). This contrasted with an increase in SaO2 to 89.5% at 4900 m and 86.3% at 5700 m with only supplemental oxygen and an increase in SaO2 to 92.8% (4900 m) and 90.5% (5700 m) with only hyperbaric exposure. In addition, combining treatments also resulted in an increase in tidal volume (29.0 and 31.0%) and minute ventilation (12.0 and 23.0%) together with a fall in heart rate (15.0 and 17.0%) at 4900 and 5700 m, respectively. No significant differences in heart rate, tidal volume, minute ventilation, SaO2, or respiratory rate were seen when hyperbaric treatment and supplemental oxygen were directly compared. CONCLUSIONS: In healthy, well-acclimatized subjects the combination of hyperbaric exposure and supplemental oxygen has a noteworthy effect on physiological parameters at high altitude. Awareness of this knowledge may enhance the treatment of patients with life-threatening high altitude sickness.

Supplemental oxygen and sleep at altitude.

Windsor, Jeremy S., and George W. Rodway. Supplemental oxygen and sleep at altitude. High Alt. Med. Biol. 7:307-311, 2006.--The purpose of this study was to examine the effect supplemental oxygen has on the respiratory and cardiovascular system of a mountaineer during sleep at high altitude by using a novel ambulatory, multisensor, continuous monitoring device. Supplemental oxygen was administered to a healthy subject via a nasal demand system (0, 16.7, 33.3, or 50 mL/sec per pulse dose delivered over 1 sec) during the first three nights of sleep at 4900 and 5700 m. Increases in pulse dose resulted in a consistent rise in Sa(O(2)) and a fall in minute ventilation (p < 0.05). The 50-mL pulse dose resulted in the greatest changes, with an increase in Sa(O(2)) from 68.5% to 81% (p < 0.05) and a fall in minute ventilation from 13.1 to 10.9 L/min (p < 0.05) being noted. Changes in Sa(O(2)) and minute ventilation also coincided with a fall in apnea/hypopnea index (AHI). At 4900 m the AHI fell from 12.5-52.3 (breathing air) to 0-7.5 (50-mL oxygen pulse), whereas at 5700 m a decrease from 49.1-80.4 to 3.5-10.0 was observed. No changes in respiratory rate or heart rate were identified when different pulse doses were compared (p < 0.05). The multisensor monitoring device proved to be a highly effective system, demonstrating marked improvements in Sa(O(2)), tidal volume, and AHI in our participant when supplemental oxygen was administered via a nasal demand system.

The use of closed-circuit oxygen in the Himalayas.

Two days before the first ascent of Mt. Everest in 1953, Tom Bourdillon and Charles Evans climbed to within 90 m of the summit at unprecedented speeds. By breathing pure oxygen from a closed circuit, the pair were able to obtain an enormous physiological advantage. Unfortunately, due to a malfunction in Evans's circuit, the pair abandoned their attempt on the South Summit. For many who used the circuit in the 1930s and 1950s, the device proved too heavy, uncomfortable, and tiring for mountaineering. These factors, together with the wider ethical concerns of using supplemental oxygen at altitude, have meant that closed-circuit oxygen has been ignored for more than 50 years. In this article the authors will attempt to describe the history of this discarded circuit and the experience of those who utilized it.

Do British commercial mountaineering expeditions carry drugs to treat high altitude illnesses?

High altitude commercial expeditions are increasingly popular. As high altitude illnesses are common on ascent to altitude, this study aimed to ascertain whether medications for these conditions were carried by commercial operators who run high altitude expeditions. Despite recommendations, it appears that drugs to treat high altitude illnesses are not routinely carried by commercial operators.

Are UK commercial expeditions complying with wilderness medical society guidelines on ascent rates to altitude?

The incidence of acute mountain sickness can be reduced by ascending slowly to altitude. We compared a recommended ascent rate with those offered by commercial companies to three of the most popular high-altitude destinations in the world. While the majority complied with the recommended ascent rate, ascents on Kilimanjaro did not.