PROMISING NONPHARMACOLOGICAL APPROACHES TO EMERGENCY ENHANCEMENT OF HUMAN RESISTANCE TO OVERCOOLING

Developing of the Arctic territories ofRussiamakes it expedient to devise safety means for emergency enhancement of professionals’ resistance to overcooling in order to reduce health risks associated with long-term dwelling under Arctic conditions. To develop and test promising means of non-pharmacological interventions suitable for enhancing the hypothermic resistance of subjects at work under cool environmental conditions, we recruited 37 able-bodied male volunteers, which were assigned to two experimental groups. In Group 1 (25 subjects), 10 sessions of cryothermic training (CTT) consisted of placing each subject in a cryochamber at –150±2° C for 2 to 5 minutes. In Group 2 (12 subjects), CTT was supplemented with 10 sessions of normobaric hypoxic preconditioning: 40 minutes of inhaling of a gas mixture containing 15% oxygen. Hypothermic resistance was assessed during the first and the tenth training procedure. The procedures were found to enhance gradually the hypothermic resistance, the outcome being more pronounced in the Group 2. The subjective tolerance to cold was roughly the same in both groups. The mean time of tolerance to hypothermia increased during the tenth vs. the first session by 40% in Group 1 vs. 49% in Group 2. Rectal temperature decrease decelerated by 19% vs. 25%, respectively. Systemic circulation responsiveness to hypothermia decreased by 23–40% vs. 28–50%, respectively. Thus, the combined hypothermic and hypoxic preconditioning is found to be an effective and safe means of non-pharmacological emergency enhancement of tolerance to hypothermia.