Altitude Preexposure Recommendations for Inducing Acclimatization

Abstract

For many low-altitude (<1500 m) residents, their travel itineraries may cause them to ascend rapidly to high (>2400 m) altitudes without having the time to develop an adequate degree of altitude acclimatization. Prior to departing on these trips, low-altitude residents can induce some degree of altitude acclimatization by ascending to moderate (>1500 m) or high altitudes during either continuous or intermittent altitude preexposures. Generally, the degree of altitude acclimatization developed is proportional to the altitude attained and the duration of exposure. The available evidence suggests that continuous residence at 2200 m or higher for 1 to 2 days or daily 1.5- to 4-h exposures to >4000 m induce ventilatory acclimatization. Six days at 2200 m substantially decreases acute mountain sickness (AMS) and improves work performance after rapid ascent to 4300 m. There is evidence that 5 or more days above 3000 m within the last 2 months will significantly decrease AMS during a subsequent rapid ascent to 4500 m. Exercise training during the altitude preexposures may augment improvement in physical performance. The persistence of altitude acclimatization after return to low altitude appears to be proportional to the degree of acclimatization developed. The subsequent ascent to high altitude should be scheduled as soon as possible after the last altitude preexposure.

Serious Altitude Illness in Travelers Who Visited a Pre‐Travel Clinic

“…6,23,24 We found that spending at least one night at moderate altitude was an independent protector of serious altitude illness, which confirms the results of Hackett and Rennie, who found a higher incidence of serious illness in trekkers who flew straight to Lukla at 2,800 m than in those who climbed gradually. 25,26 Although our study confirms the results of MacNutt and colleagues, who found that having been at high altitude previously is associated with a lower incidence of altitude illness, it is not a predictor in itself. 27 The same is true for the recommendation to "climb high and sleep low."…”

Circadian and Sex Differences After Acute High-Altitude Exposure: Are Early Acclimation Responses Improved by Blue Light?

“…In Chile, since December 2012, legislation recognizes disorders resulting from hypobaria and requires companies operating at altitude to provide adequate education and preventive measures for their workers. To mitigate these problems, some strategies have been proposed for high-altitude working facilities, such as 1) the installation of base camps at lower altitudes for sleep and leisure [9][10][11] ; 2) the use of physiological preacclimation strategies, such as hypobaric chambers 12 ; 3) the use of portable canned oxygen for pulse delivery, as used, for example, by visitors to the ALMA telescope site (5050 m); or 4) oxygen enrichment of workplaces. [13][14][15][16] The application of blue light illumination has proved to be a very effective way of improving the regulation of circadian rhythms.…”

Alterations in Carotid Body Morphology and Cellular Mechanism Under the Influence of Intermittent Hypoxia

“…A low number of re-oxygenation cycles per day and moderate hypoxic episodes elicits the beneficial effects beyond pathology and provides protection against hypertension, myocardial injuries, heart arrhythmia and bronchial asthma [19,20]. It helps in activating the surviving mechanisms against acute hypoxic exposure by increasing haemoglobin, erythropoietin production, total red blood cells, exercise time, hypoxic ventilatory responses in healthy human subjects, bone mineral density, respiratory and non respiratory somatic motor recovery following spinal injuries in rats and humans and enhancement of spatial learning and memory without any detectable adverse consequences [21].…”