Rapid acclimatization strategies for high-altitude induction

Abstract

High altitude (HA) is defined as elevation above 9,000 ft. At this altitude, most people develop acute mountain sickness (AMS). If untreated, this may lead to high-altitude pulmonary oedema (HAPE) or high-altitude cerebral oedema (HACE), both of which are potentially life-threatening. In emergencies/warlike conditions, rapid deployment of military personnel to high altitude frequently occurs without giving the adequate degree of altitude acclimatization, resulting in acute mountain sickness (AMS). Acclimatization to high altitude is the best strategy to prevent AMS, and this can be achieved by hypoxia preconditioning by the use of interventions like hypoxia mimetics. Efficacy of hypoxia mimetics, viz. cobalt chloride (CoCl 2), ethyl 3, 4-dihydroxybenzoate (EDHB), sphingosine-1-phosphate (S1P) and other pharmacological agent nanocurmin in facilitating acclimatization to high altitude in animal model, has been discussed. An alternative approach to induce acclimatization and reduce incidence of AMS is the use of intermittent hypoxic exposure (IHE). This study was conducted to evaluate the effect of IHE exposure at sea level on incidence of AMS during acute ascent to 3,500 m altitude in Indian military personnel. The army volunteers were divided into two groups, viz. control and experimental. Experimental group of subjects were exposed to intermittent normobaric hypoxia consisting of 12 % FIO 2 (altitude - air equivalent 4,350 m) for 4 h per day for 4 consecutive days. After giving IHT, the subjects were inducted to 3,500 m altitude (Leh) by air and different physiological parameters like AMS score (LLS), pulse arterial oxygen saturation (SaO 2) and ventilatory parameters (V E, VO 2, V T /Ti) were recorded daily. IHE-treated group showed a significant reduction in AMS at HA in comparison to control. IHE may be considered as an alternative approach to induce the altitude acclimatization at low altitude-based soldiers before their deployment to high-altitude operations in emergency-like conditions.