[Reaction of the external respiration system to a hypercapnic stimulus in rabbits under increased pressure]

In 10 unanesthetized rabbits exposed to normoxic (PIO2 = 0.2 kgs/cm2) helio-oxygen medium under pressure 40 kgs/cm2, changes of the respiration parameters (frequency, Vt, V, ITP) depending on the CO2 tension in the blood were studied with the aid of the recurrent respiration technique. The animals both in hyperbaric and in normal conditions (air), when breathing from the sack up to 7 min, revealed a linear increase in V due to an increase of the CO2 tension in the blood, but the lung ventilation increment decreased by the 12th min. In the helio-oxygen mixture under hyperbaric conditions the V relative increment was lesser and its decrease by the 12th min was more obvious than in ordinary air under the atmospheric pressure.