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

Hyperthermia potentiates the influence of CO2 on pulmonary ventilation ((V) over dot(E)). It remains to be resolved how skin and core temperatures contribute to the elevated exercise ventilation response to CO2. This study was conducted to assess the influences of mean skin temperature ((T) over bar (SK)) and end- tidal PCO2 (PETCO2) on (V) over dot(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 similar to 37.1 +/- 0.4 degrees C. Once T-ES stabilized in each trial, the volunteer breathed hypercapnic air twice for similar to 5 min with PETCO2 elevated by approximately +4 or +7.5 mmHg. The significantly (P < 0.05) different increases of PETCO2 of +4.20 +/- 0.49 and +7.40 +/- 0.51 mmHg gave proportionately larger increases in (V) over dot(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)over bar>(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 similar to 33 and similar to 36 degrees C has neither effect on pulmonary ventilation nor on hypercapnia-induced hyperventilation during a light exercise with a normothermic core temperature.