METABOLIC AND VENTILATORY ADJUSTMENTS AND TOLERANCE OF THE BAT PTEROPUS-POLIOCEPHALUS TO ACUTE HYPOXIC STRESS

We have investigated the maximum tolerance and the ventilatory respons es of a bat, P, poliocephalus (PP), to normobaric hypoxic stress. PP c an tolerate inspired PO(2)s (PiO2) down to 30 torr, This bat is one of the most hypoxia-tolerant non-hibernating species of mammals known, a nd has a tolerance which lies within the range of P(i)O(2)s reported f or different birds, Unlike most mammals in its size range, PP maintain s its normoxic oxygen consumption rate even in deep hypoxia, The maxim um hypoxic ventilatory response (HVR), the air convection requirement (V-i/MO(2)), and the lung oxygen extraction (E(L)) ability of PP in de ep hypoxia are all greater than those of other mammals, These and othe r data indicate that PP has a superior mammalian tolerance for hypocap nia, The magnitudes of both the V-i/MO(2) and the E(L) values of PP fa ll between those reported for Pekin ducks at corresponding P(i)O(2)s, and are inferior to the maximum capabilities of bar-headed geese, Thus , the tolerance and ventilatory adjustments of PP to deep hypoxia are intermediate between those of typical non-flying mammals and the most tolerant avian species, and suggest that at least some of this bat's r espiratory adaptations for flight may serve as preadaptations for with standing acute hypoxic stress.