High-altitude Trekking Research Articles

Asthma in adventure travelers: a prospective study evaluating the occurrence and risk factors for acute exacerbations.

Exacerbation of asthma during travel to remote regions may lead to devastating consequences. The course of asthma in travelers and the risk factors for disease exacerbation during travel have not been studied. We screened 5835 consecutive travelers and identified 203 patients with asthma. Before travel, all enrollees were assessed for presumed risk factors for asthma exacerbation by means of an interview and an exercise test combined with spirometry. After travel, data regarding travel characteristics and asthma severity were recorded by means of a structured telephone interview. The 203 enrollees visited 56 countries for a median duration of 13 weeks, 147 were engaged in high-altitude trekking, and 88 had asthma attacks. Among these, 40 reported worsening asthma during travel, 32 experienced the worst asthma attack ever, and 11 reported a life-threatening asthma attack. Two independent risk factors for attacks during travel were identified: frequent use (> or = 3 times weekly) of inhaled bronchodilators before travel (relative risk [RR], 3.35; 95% confidence interval [CI], 1.75-6.39) and participation in intensive physical exertion during treks (RR, 2.04; 95% CI, 1.04-3.98). When both risk factors were present, the RR for asthma attacks increased to 5.52 (95% CI, 2.81-10.84). Asthma frequently worsens during travel and should not be ignored as a potentially life-threatening condition requiring pretravel consideration. Asthmatic travelers who frequently use inhaled bronchodilators before travel or participate in intensive trekking during travel are at increased risk to develop asthma attacks. Therapy should be intensified to achieve better disease control; intensive trekking should be discouraged.

Myocardial infarction or high-altitude pulmonary edema?

We report the case of a 60-year-old European man with myocardial infarction at high altitude (4000 m). Myocardial infarction is an uncommonly encountered problem in high-altitude trekking in the Himalayas. The paucity of coronary artery disease at high altitude (hypoxia, exercise, and age not-withstanding) is discussed. Finally, the importance of recognizing disease entities that mimic acute mountain sickness in this environment is emphasized.

Pulmonary ventilatory function decreases in proportion to increasing altitude

The objective of this study was to examine how pulmonary ventilatory function, including response to bronchodilation, is related to altitude during high-altitude trekking. This cohort experiment consisted of multiple spirometric tests before and after bronchodilation in participants at baseline (1624 m) and at different altitudes (3404-4896 m) during a 2-week trek. The setting was in the Himalayas. Eleven men (ages 22-68 years) and eight women (ages 19-42 years) participated. Interventions were at altitudes of 1624 m to 5265 m; albuterol was administered via Rotahaler. Forced vital capacity (FVC) decreased by an average of 3.8% [95% confidence interval (CI) 1.6 to 6.0] per 1000-m altitude increment. Forced expiratory volume in 1 second (FEV1.0) decreased 3.7% (95% CI 1.9 to 5.5) per each 1000-m altitude increment. Maximal midexpiratory flow rate (FEF25-75%) decreased by 3.6% (95% CI 0.9 to 6.3) per each 1000-m altitude increment. Small, postalbuterol flow increases were present at baseline and at altitude. Ventilatory function returned quickly toward baseline upon descent. One trekker developed cough, dyspnea at rest, extreme weakness, rales, tachycardia, and oxygen desaturation to 71%. His ventilatory measurements did not differ significantly (p > 0.32) from the group means. We concluded that changes in some pulmonary ventilatory parameters (FVC, FEV1.0, and FEF25-75%) were proportional to the magnitude of altitude during a high-altitude trek. These were tolerated well and do not seem to relate to acute mountain sickness. A bronchodilator effect was not increased at altitude.

Ambulatory electrocardiographic monitoring at high altitude

High altitude trekking has been associated with hypoxemia, moderate tachycardia and resting electrocardiographic changes. We performed ambulatory electocardiographic monitoring (24 h) on nine men and two women (age range 24 to 64 years) at 4700 m to study a varied population for cardiac rate, rhythm, and possible ischemic effects during physically demanding trekking. Six participants, randomly chosen, were taking pentoxifylline. Sinus tachycardia was sustained particularly in the five older trekkers (mean age 51 years). Their maximum heart rates during trekking averaged 91% of the individual predicted maximum heart rates or 154 beats per minute; their highest mean one hour rates averaged 78% of predicted maximum heart rates or 132 beats per minute. During sleep at 4700 m, the differences between the nadir and the mean rate were significantly (p = .02) greater than at baseline altitude (1524 m). Ambulatory electrocardiographic abnormalities were minimal and no significant drug effects were observed.

MEDICAL CONSIDERATIONS FOR THE PREGNANT TRAVELER

The care of pregnant travelers requires clinical information and skills that are derived from many disciplines. Issues to be considered include the safety of both mother and fetus during commercial air travel, vigorous exercise, scuba diving, and even high-altitude trekking. Immunizations require a balanced approach to the risk of disease versus the risks of vaccine complications. Safe or treated water sources are of paramount importance to prevent unnecessary exposure to antimicrobial and antiparasitic agents during pregnancy. Malaria prophylaxis is made even more difficult by an increasingly widespread resistance of Plasmodium species to chloroquine.

Points from Letters: Hazards of High Altitude Trekking

Points from Letters: Hazards of High Altitude Trekking