Altitude medicine

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Bailey, Damian M., Christopher K. Willie, Ryan L. Hoiland, Anthony R. Bain, David B. MacLeod, Maria A. Santoro, Daniel K. DeMasi, Andrea Andrijanic, Tanja Mijacika, Otto F. Barak, Zeljko Dujic, and Philip N. Ainslie. Surviving without oxygen: how low can the human brain go? High Alt Med Biol 18:73-79, 2017.-Hypoxic cerebral vasodilation is a highly conserved physiological response coupling cerebral O2 delivery (CDO2 ) to metabolic demand with increasingly important roles identified for the red blood cell (sensor) and nitric oxide (effector)...

OBJECTIVE: Rapid ascent to altitude can result in the development of high altitude illnesses such as acute mountain sickness (AMS). This study aimed to investigate AMS symptoms in adolescents and study basic cardiopulmonary measurements at altitude. METHODS: Thirty-eight adolescents aged 16 to 19 years flew to 3500 m from 215 m and continued over a 23-day period to ascend to a maximum altitude of 5200 m. Each member of the expedition completed a Lake Louise Self-Assessment Questionnaire (LLSAQ) on a daily basis, and AMS was defined as a score of ≥ 3, with an associated headache...

OBJECTIVE: The purpose of this study was to examine the relationship between acute mountain sickness (AMS) and the fraction of exhaled nitric oxide (Fe(NO)) and carbon monoxide (Fe(CO)) before ascent to high altitude and to evaluate their predictive value for AMS. METHODS: A total of 314 healthy young male recruits were voluntarily enrolled. Before ascent to an elevation of 4300 m, their Fe(NO) and Fe(CO) values, demographic factors, drinking and smoking history, vital capacity, and forced vital capacity were obtained...

OBJECTIVE: Hemodynamic changes in response to the hypoxic environment of high altitude are vascular bed-specific. The aim of the present study was to investigate diameter and blood flow changes in conduit vessels in response to hypobaric hypoxia. METHODS: Eleven healthy subjects ascending Mount Everest to base camp participated in this study. Vessel diameter and blood velocity for brachial, carotid, common femoral, superficial femoral, and deep femoral arteries were measured by portable Doppler ultrasound...

OBJECTIVE: Altitude illness can occur in anyone who ascends to high altitude. Better understanding of altitude illness is associated with a lower incidence of acute mountain sickness (AMS). The purpose of this study is to compare, for the first time, the incidence and understanding of altitude illness between foreign trekkers and indigenous porters in Nepal. METHODS: Interviews and questionnaires were completed at the International Porter Protection Group Rescue Post at Machermo (4470 m)...

OBJECTIVE: To study the effectiveness of ibuprofen versus placebo in preventing acute mountain sickness (AMS) and high altitude headache (HAH). METHODS: Double-blind, randomized, placebo-controlled trial. RESULTS: Two hundred ninety-four healthy Western trekkers were recruited on the Everest approach at 4280 m or 4358 m and randomly assigned to receive either 600 mg of ibuprofen or placebo 3 times daily before and during ascent to 4928 m. One hundred eighty-three of 294 participants completed the trial...

OBJECTIVE: High altitude environments present unique medical treatment challenges. Medical providers often use small portable pulse oximetry devices to help guide their clinical decision making. A significant body of high altitude research is based on the use of these devices to monitor hypoxia, yet there is a paucity of evidence that these devices are accurate in these environments. We studied whether these devices perform accurately and reliably under true mountain conditions. METHODS: Healthy unacclimatized active-duty military volunteers participating in mountain warfare training at 2100 m (6900 feet) above sea level were evaluated with several different pulse oximetry devices while in a cold weather, high altitude field environment and then had arterial blood gases (ABG) drawn using an i-STAT for comparison...

To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for the prevention and treatment of acute mountain sickness (AMS), high altitude cerebral edema (HACE), and high altitude pulmonary edema (HAPE). These guidelines present the main prophylactic and therapeutic modalities for each disorder and provide recommendations for their roles in disease management. Recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians...

OBJECTIVE: Ascent to high altitude leads to a reduction in ambient pressure and a subsequent fall in available oxygen. The resulting hypoxia can lead to elevated pulmonary artery (PA) pressure, capillary stress, and an increase in interstitial fluid. This fluid can be assessed on lung ultrasound (LUS) by the presence of B-lines. We undertook a chamber and field study to assess the impact of high-intensity exercise in hypoxia on the development of pulmonary interstitial edema in healthy lowlanders...

OBJECTIVE: We aimed to ascertain risk factors for acute mountain sickness (AMS) in miners exposed to chronic intermittent high altitude conditions. METHODS: All new hires (2009-2012) for mine employment (4000 m above sea level) were followed up for 12 months after first ascent. Demographics, physiologic data, and cigarette smoking were assessed at preemployment screening. Mine site clinic care for AMS defined incident events. Cox regression analysis estimated risk of AMS associated with smoking and selected covariates...

OBJECTIVE: Exposure to altitude may lead to acute mountain sickness (AMS) in nonacclimatized individuals. We surveyed AMS prevalence and potential risk factors in trekkers crossing a 5400-m pass in Nepal and compared the results with those of 2 similar studies conducted 12 and 24 years earlier. METHODS: In April 2010, 500 surveys were distributed to English-speaking trekkers at 3500 m on their way to 5400 m, of which 332 (66%) surveys were returned complete. Acute mountain sickness was quantified with the Lake Louise Scoring System (LLSS, cutoff ≥3 and ≥5) and the Environmental Statistical Questionnaire III AMS-C score (ESQ-III, cutoff ≥0...

OBJECTIVE: The purpose of this study was to determine whether arterial oxygen saturation (Spo(2)) and heart rate (HR), as measured by a finger pulse oximeter on rapid arrival to 4260 m, could be predictive of acute mountain sickness (AMS) or summit success on a climb to 5640 m. METHODS: Climbers (35.0 ± 10.1 years; 51 men, 5 women) were transported from 2650 m to the Piedra Grande hut at 4260 m on Pico de Orizaba within 2 hours. After a median time of 10 hours at the hut, they climbed toward the summit (5640 m) and returned, with a median trip time of 14 hours...

OBJECTIVE: The purpose of this study was to review the patient characteristics and management of 56 cases of high altitude pulmonary edema at the Pheriche Himalayan Rescue Association Medical Aid Post, and to measure the use of medications in addition to descent and oxygen. METHODS: In a retrospective case series, we reviewed all patients diagnosed clinically with high altitude pulmonary edema during the 2010 Spring and Fall seasons. Nationality, altitude at onset of symptoms, physical examination findings, therapies administered, and evacuation methods were evaluated...

OBJECTIVE: The effect of altitude on brain function is not yet well understood, nor is the influence of height and speed of ascent. Additionally, the relationship between acute mountain sickness (AMS) symptoms and brain function at altitude is unclear. We hypothesized that a deterioration from baseline measures of brain function occurs after rapid, mechanical ascent to 3459 m and would be less pronounced in persons taking acetazolamide. METHODS: In this double blind, randomized, placebo-controlled study, 20 healthy volunteers (14 men, 6 women; mean age [±SD] 43 ± 16 years) were alternately allocated to acetazolamide 250 mg or to placebo, taken every 12 hours commencing 3 days before ascent...

High-altitude pulmonary edema (HAPE) is a life-threatening noncardiogenic form of pulmonary edema (PE) that afflicts susceptible persons after rapid ascent to high altitude above 2500 m. Its pathogenesis is related to increased sympathetic tone, exaggerated hypoxic pulmonary vasoconstriction, uneven hypoxic pulmonary vasoconstriction with overperfusion of some regions of the pulmonary vascular bed, increased pulmonary capillary pressure, stress failure of pulmonary capillaries, and alveolar fluid leak across capillary endothelium resulting in interstitial and alveolar edema...

OBJECTIVE: Acclimatization at natural altitude effectively prevents acute mountain sickness (AMS). It is, however, unknown whether prevention of AMS is also possible by only sleeping in normobaric hypoxia. METHODS: In a placebo-controlled, double-blind study 76 healthy unacclimatized male subjects, aged 18 to 50 years, slept for 14 consecutive nights at either a fractional inspired oxygen (Fio2) of 0.14 to 0.15 (average target altitude 3043 m; treatment group) or 0...

BACKGROUND: High altitude (HA) pulmonary edema (PE) results from complex and misunderstood interactions between adaptation mechanisms. We assessed the occurrence of subclinical PE and brain natriuretic peptide (BNP) levels among nonacclimatized individuals during an expedition on Mount Elbrus (5642 m). METHODS: Seven subjects underwent assessment of vital signs, Lake Louise Score, ultrasound lung comets using handheld echography and circulating BNP using capillary testing at different stages of ascension, in addition to baseline echocardiography...

BACKGROUND: The comet-tail technique of chest ultrasonography has been described for the diagnosis of cardiogenic pulmonary edema. This is the first report describing its use for the diagnosis and monitoring of high-altitude pulmonary edema (HAPE), the leading cause of death from altitude illness. METHODS: Eleven consecutive patients presenting to the Himalayan Rescue Association clinic in Pheriche, Nepal (4,240 m) with a clinical diagnosis of HAPE underwent one to three chest ultrasound examinations using the comet-tail technique to determine the presence of extravascular lung water (EVLW)...

BACKGROUND: Data regarding the effect of high altitude on heart function are sparse and conflicting. We aimed to assess the right and left ventricular responses to altitude-induced hypoxia and the occurrence of subclinical pulmonary edema. METHODS: Echocardiography was performed according to protocol on 14 subjects participating in an expedition in Nepal, at 3 altitude levels: Montreal (30 m), Namche Bazaar (3450 m), and Chukkung (4730 m). Systematic lung ultrasound was performed to detect ultrasound lung comets...