Respiration restitution in rats following its termination in immersion hypothermia.

Rats were cooled in water until attaining profound hypothermia and respiratory arrest. After removal from water, 0.5% solution of Na2EDTA was administered intravenously. This led to a drop of blood [Ca2+] by 20-30% from the baseline and promoted recovery of respiration following its arrest lasting 10.3±1.4 min. By the 30th minute of Na2EDTA administration, respiration rate increased to 32.3±5.2 cycles per minute and respiration amplitude reached 68±4% of the baseline level. This effect was observed without special warming of the rats. It was concluded that the period during which the organism maintains viability in respiration arrest and disturbances in respiratory center are still reversible is prolonged under conditions of profound hypothermia.