Effect of exercise testing protocol on the relationship between minute ventilation and carbon dioxide production

The effect of exercise protocol on the slope of the relationship between minute ventilation and carbon dioxide production (deltaVE/deltaVCO2) has not fully been studied. Twenty-five healthy volunteers performed two sessions of incremental bicycle exercise, one with a rapidly increasing staged (RIS: 25W every minute) protocol and another with a slowly increasing staged (SIS: 25W every 3 minutes) protocol to calculate the deltaVE/deltaVCO2. Six of the subjects also participated in sessions of steady state exercise (SSE) test various work rates. The deltaVE/deltaVCO2 was significantly lower when the RIS protocol was used than when the SIS protocol was used (23.3 +/- 2.3 vs. 24.9 +/- 1.8, p < 0.001). Data from the subjects who also underwent SSE sessions revealed that the deltaVE/deltaVCO2 from the SSE protocols was greater than that from the RIS protocol and identical with that from the SIS protocol (125.1 +/- 3.7. 20.6 +/- 1.7, and 24.0 +/- 2.7, respectively, p < 0.05), while arterial partial pressure of carbon dioxide during exercise was not different between the protocols (43.0 +/- 3.3. 39.9 +/- 2.1, and 40.8 +/- 2.6, respectively, n.s.). C ONCLUSIONS: Care must be taken in the interpretation of the values of deltaVE/deltaVCC2, as they are influenced by the difference in exercise protocol.