Hypoxic responses in resting hyperthermic humans

This thesis investigated the interaction between steady state hypoxia and passive hyperthermia on human ventilation and the influence of the PETCO2 on this interaction. On one of two days males twice breathed 12% oxygen for 20 min while either normothermic or hyperthermic with PETCO2 clamped -1 mm Hg above resting (iHVR). On the other day the same tests were performed except P&02 was uncontrolled (pHVR). Hyperthermia increased euoxic ventilation compared to normothermia (plO.OO1). During iHVR ventilation increased more during hyperthermia than normothermia (p=0.002), but not during pHVR (p=0.98). Heart rates at conclusion of pHVR compared to iHVR were greater for normothermia (p=0.05) and hyperthermia (p=0.004). Therefore during pHVR the decreasing P&02 levels blunt the ventilatory response to hypoxia more than hyperthermia augments it as seen during iHVR. Also pHVR increases cardiovascular responses to hypoxia more than iHVR. An end tidal forcing system was developed to control PETC02.