No effect of skin temperature on human ventilation response to hypercapnia during light exercise with a normothermic core temperature.

Hyperthermia potentiates the influence of CO(2) on pulmonary ventilation (.V(E)). It remains to be resolved how skin and core temperatures contribute to the elevated exercise ventilation response to CO(2). This study was conducted to assess the influences of mean skin temperature (_T(SK)) and end-tidal PCO(2) (P(ET)CO(2)) on .V(E) during submaximal exercise with a normothermic esophageal temperature (T(ES)). Five males and three females who were 1.76 +/- 0.11 m tall (mean +/- SD), 75.8 +/- 15.6 kg in weight and 22.0 +/- 2.2 years of age performed three 1 h exercise trials in a climatic chamber with the relative humidity (RH) held at 31.5 +/- 9.5% and the ambient temperature (T (AMB)) maintained at one of 25, 30, or 35 degrees C. In each trial, the volunteer breathed eucapnic air for 5 min during a rest period and subsequently cycle ergometer exercised at 50 W until T (ES) stabilized at approximately 37.1 +/- 0.4 degrees C. Once T (ES) stabilized in each trial, the volunteer breathed hypercapnic air twice for approximately 5 min with P(ET)CO(2) elevated by approximately +4 or +7.5 mmHg. The significantly (P < 0.05) different increases of P(ET)CO(2) of +4.20 +/- 0.49 and +7.40 +/- 0.51 mmHg gave proportionately larger increases in .V(E) of 10.9 +/- 3.6 and 15.2 +/- 3.6 L min(-1) (P = 0.001). This hypercapnia-induced hyperventilation was uninfluenced by varying the _T(SK) to three significantly different levels (P < 0.001) of 33.2 +/- 1.2 degrees C, to 34.5 +/- 0.8 degrees C to 36.4 +/- 0.5 degrees C. In conclusion, the results support that skin temperature between approximately 33 and approximately 36 degrees C has neither effect on pulmonary ventilation nor on hypercapnia-induced hyperventilation during a light exercise with a normothermic core temperature.