Physiological Risk Factors for Severe High-Altitude Illness A Prospective Cohort Study

• Published in: American journal of respiratory and critical care medicine Vol. 185; no. 2; pp. 192 - 198
• Main Authors: Richalet, Jean-Paul, Larmignat, Philippe, Poitrine, Eric, Letournel, Murielle, Canouï-Poitrine, Florence
• Format: Journal Article
• Language: English
• Published: New York, NY American Thoracic Society 15.01.2012
• Subjects: Acetazolamide - administration & dosage; Acute Disease; Adult; Altitude; Altitude Sickness - complications; Altitude Sickness - epidemiology; Altitude Sickness - etiology; Altitude Sickness - physiopathology; Altitude Sickness - prevention & control; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Biological and medical sciences; Blood and lymphatic vessels; Brain Edema - epidemiology; Brain Edema - etiology; Brain Edema - physiopathology; Brain Edema - prevention & control; Cardiology. Vascular system; Cohort Studies; Confidence Intervals; Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous; Diuretics - administration & dosage; Edema; Exercise; Exercise Test; Female; France - epidemiology; Headache - etiology; Humans; Hypertension, Pulmonary - epidemiology; Hypertension, Pulmonary - etiology; Hypertension, Pulmonary - physiopathology; Hypertension, Pulmonary - prevention & control; Hypoxia; Intensive care medicine; Male; Medical sciences; Middle Aged; Migraine; Mountain climbing; Odds Ratio; Oxygen saturation; Physical fitness; Physiology; Prospective Studies; Risk Assessment; Risk Factors; Severity of Illness Index; France; High altitude; Oxygen; Nervous system diseases; Intensive care; Environmental factor; Altitude induced disorder; Lung edema; Cerebral disorder; Acute mountain sickness; Cohort study; high-altitude cerebral edema; high-altitude pulmonary edema; Central nervous system disease; Risk factor; ventilatory response to hypoxia; Hypoxia; Cerebral edema; Resuscitation
• ISSN: 1073-449X; 1535-4970; 1535-4970
• DOI: 10.1164/rccm.201108-1396OC

An increasing number of persons, exposed to high altitude for leisure, sport, or work, may suffer from severe high-altitude illness. To assess, in a large cohort of subjects, the association between physiological parameters and the risk of altitude illness and their discrimination ability in a risk prediction model. A total of 1,326 persons went through a hypoxic exercise test before a sojourn above 4,000 m. They were then monitored up at high altitude and classified as suffering from severe high-altitude illness (SHAI) or not. Analysis was stratified according to acetazolamide use. Severe acute mountain sickness occurred in 314 (23.7%), high-altitude pulmonary edema in 22 (1.7%), and high-altitude cerebral edema in 13 (0.98%) patients. Among nonacetazolamide users (n = 917), main factors independently associated with SHAI were previous history of SHAI (adjusted odds ratios [aOR], 12.82; 95% confidence interval [CI], 6.95-23.66; P < 0.001), ascent greater than 400 m/day (aOR, 5.89; 95% CI, 3.78-9.16; P < 0.001), history of migraine (aOR, 2.28; 95% CI, 1.28-4.07; P = 0.005), ventilatory response to hypoxia at exercise less than 0.78 L/minute/kg (aOR, 6.68; 95% CI, 3.83-11.63; P < 0.001), and desaturation at exercise in hypoxia equal to or greater than 22% (aOR, 2.50; 95% CI, 1.52-4.11; P < 0.001). The last two parameters improved substantially the discrimination ability of the multivariate prediction model (C-statistic rose from 0.81 to 0.88; P < 0.001). Preventive use of acetazolamide reduced the relative risk of SHAI by 44%. In a large population of altitude visitors, chemosensitivity parameters (high desaturation and low ventilatory response to hypoxia at exercise) were independent predictors of severe high-altitude illness. They improved the discrimination ability of a risk prediction model.