EFFECTS OF HYPERTHERMIA ON HYPOXIC VENTILATORY RESPONSE IN NORMAL MAN

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 89  (3) , 564-572
Abstract
Increased body temperature stimulates hyperventilation in man but little is known about its effects on ventilatory responsiveness to hypoxia. The effects of hyperthermia were studied on hypoxic ventilatory response (HVR), hypercapnic ventilatory response (HCVR) and O2 consumption (.ovrhdot.VO2). Six fasting subjects had these variables measured under basal conditions and at 2 levels of hyperthermia. Hypoxic ventilatory response was measured as the shape parameter A of the .ovrhdot.VE/PAO2 [alveolar O2 tension] curves. Since hyperthermia produces hyperventilation and, therefore, hypocapnia, HVR was measured at the hyperthermic (hypocapnic) alveolar CO2 tension (PACO2) and at the basal (normothermic) PACO2. Hypoxic ventilatory response (A) increased when measured at basal PACO2 levels, from 113 .+-. 8.8 (SEM [standard error of the mean]) to 189 .+-. 21.8 at +0.7.degree. C and 240 .+-. 34.0 at +1.40.degree. C. (P < 0.005). HVR measured during hyperthermic hypocapnia also increased at each temperature level but did not reach statistical significance (P = 0.1). Hypercapnic ventilatory response, as measured by the slope S of .ovrhdot.VE/PACO2 lines, increased significantly at each temperature elevation (P < 0.025). Raising body temperature causes a significant augmentation og ventilatory responses to hypoxia (during normothermic PACO2 conditions) and to hypercapnia.

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