Effect of Oxygen Pre-Breathing on Anoxemia in Albino Rats

Abstract

While engaged in the study of a problem involving the changing erythrocyte counts in the blood of albino rats under low oxygen tensions, 1 it was noted that certain animals withstood the onset of critical anoxemia better than others. This observation, coupled with a report by Hill 2 concerning beneficial effects of oxygen pre-breathing upon aviators, stimulated the present inquiry as to (1) what effect intervals of oxygen pre-breathing might have upon the postponement of critical anoxemia in male and female groups of rats, and (2) what intervals might prove to be most advantageous, if effective at all, for these forms.

This report includes an analysis of the data taken from 4 series of experiments on 5 male and 5 female Wistar strain rats of comparable ages and weights selected from the department colony. Preliminary to the tests here cited, a number of experiments were performed in perfecting apparatus and technics. Each animal was subjected to intervals of pre-breathing of 25, 40, 70, and 130 minutes in a properly arranged chamber which could be exhausted and maintained at any given atmospheric pressure. As a control the same individuals were tested in air. The barometric pressure used was 200 mm Hg, which is equivalent to a partial oxygen pressure of only 42 mm Hg, or the approximate equivalent in altitude of 6 1/2 miles above sea-level. The comparative differences in the time of onset of anoxemia in the different individual rats subjected to various intervals are shown in Table I. It is apparent from the analyses of these data that there are consistently slight differences in the 2 sexes, the females being slightly more resistant as a group than the males, when exposed to critical but not fatal low pressures (Table I).