Determination of cerebral and neck subcutaneous tissue PO2 with 3 and 4 +Gz in M. mulatta

Four male and four female, fully conscious, M. mulatta were exposed twice each to diphasic accelerations of 3 or 4 +Gz (3 min) with a 10-min, 1-G intersession. One polarographic electrode was inserted intracortically and another one into neck subcutaneous tissue. With the first of two 3 or 4 +Gz exposures, cerebral PO2 fell from 15.11 to 5.73 and 2.92 torr, respectively; subcutaneous PO2 fell from 27.6 to 7.72 and 4.8 torr, respectively. Cerebral tissue exhibits post-G hyperoxia, related to initial stress intensity; even after the 10-min intersession, it is capable of mitigating the O2 desaturation effect of the second stress. Cerebral and subcutaneous tissue oxygen desaturation with G onset are comparable, but re-oxygenation in the latter tissue is apparently inertia-ridden and a simple relationship between the overall responses of cerebral and subcutaneous PO2 to +Gz acceleration could not be demonstrated.