Chemical control of pulmonary ventilation during short-term intermittent activity and recovery

Arterial CO2 pressure (PaCO2) is one of important factors in Chemical mechanism of ventilation (VE) control that its direct or indirect effect on VE or its lack of influence is still under discussion. The purpose of the present study was to investigate the effect of PaCO2 on VE during short-term intermittent activity and during recovery after this activity and to investigate time lag in stimulation of VE by PaCO2.

Ten inactive male subjects performed a short-term intermittent activity (10 sec) with work load of 200 watts that induces condition in which only PaCO2 among all chemical factors is changed. VE and gas exchange data were measured continuously during rest, warming up, activity and recovery periods. PaCO2 was predicted from PETCO2 and tidal volume (VT). Cross correlation was obtained for showing correlation coefficient between VE and predicted PaCO2considering various time lags.

The amount of Predicted PaCO2 was significantly higher than warming up levels from 14 sec to 28 sec during recovery and the amount of VE was significantly higher than warming up levels from 14 sec to 90 sec during recovery (p < 0.05) and the highest correlation coefficient between VE and predicted PaCO2 was obtained in time lag of 7s (r=0.854).

The results of this study indicate that in inactive males PaCO2 stimulate VE during short-term intermittent activity and during recovery after that and there is a time lag of 7 sec in stimulation of VE by PaCO2.