ENDURANCE OF HYPOXIC HYPOXIA AFTER PRELIMINARY BREATHING OF NORMOXIC MIXTURES CONTAINING ARGON OR KRYPTON
The purpose was assessment of the possibility to increase mammal's endurance of hypoxic hypoxia by preconditioning through breathing normoxic gas mixtures (BGM) containing argon or krypton. Preconditioning by krypton-containing BGM one or two hours prior to hypoxia (initial О2 concentration of 20.8 %) increased endurance of oxygen starvation. Preconditioning by argon-containing BGM did not bring this effect. Immediately after hypoxia several animals in both the test and control groups displayed a short-time generalized tremor that grew in the nitrogen – argon – krypton (N2 – Ar – Kr) succession consistently with their narcotic activities. This effect can be ascribed to modification by Ar and Kr of the humoral and neuronal tremor reactions to the hypoxic stress. Testing the preconditioning effect of Kr-containing BGM prior to hypoxia with the initial О2 concentration of 14.6 ± 0.40 % also demonstrated a decrease of minimal endurable О2 concentration although less evident. Effects from normoxic Kr-containing BGM correlates with the time space between preconditioning and hypoxia.