Alveolar gas pressure changes with resistive loads in man.

Respiratory responses to a single breath during which a resistive load was applied were studied in 8 conscious subjects. There was an increase in inspiratory time (TI), an increase in end-tidal PCO2 (PETCO2) and a decrease in end-tidal PO2 (PETO2) on the resisted breath. 12 subjects were given a single inspiration of a mixture of air containing increased CO2 and reduced O2. This gas mixture induced changes in PETCO2 and PETO2 approximately double those seen with the resistive loads. There was no change in tidal volume (VT), TI or expiratory time during the first breath. During the following breath there was a small increase in TI and VT. The results indicate that although resistive loading may cause changes in PETCO2 and PETO2, these changes are unlikely to contribute to the respiratory responses during the first loaded breath.