Respiration of conscious kittens in acute hypoxia and effect of almitrine bismesylate

Abstract

Respiration was measured noninvasively in conscious kittens at an ambient temperature of 28-32.degree. C. Inspired O2 fraction (FIO2) was reduced abruptly from 0.21-0.12, 0.10 or 0.08 for 5 min on the day of birth and then on days 4, 7, 14 and 28. The ventilatory response to hypoxia was biphasic, as reported previously in anesthetized kittens, with minute ventilation (.ovrhdot.VE) increasing in the 1st min and them falling towards control over the next 4 min. The fall in .ovrhdot.VE was due to a consistent fall in tidal volume, the changes in frequency during the 2nd phase being more variable. The size of the 1st phase of the response increased up to 14 days, but the time at which the peak increase in .ovrhdot.VE occurred was not correlated with age. The degree of the secondary fall in .ovrhdot.VE was similar at each age and at each FIO2 studied. The degree of the biphasic response was significantly reduced after administration of almitrine (2 mg/kg i.p.) on days 1 and 4, but almitrine did not affect the response in older kittens.