Airflow limitation and control of end-expiratory lung volume during exercise

To test the hypothesis that the presence of airflow limitation (AFL) influences the control of end-expiratory lung volume (EELV) during exercise, 11 subjects with normal lung function, performed submaximal exercise (SM) on a cycle ergometer, with and without AFL. AFL was achieved during exercise by increasing the density of the air via a hyperbaric chamber, compressed to a depth of 3 atm (3 ATA; with AFL). Five subjects achieved AFL during SM exercise at 3 ATA while the remaining six subjects did not achieve AFL. SM exercise was performed with the same apparatus in the hyperbaric chamber at sea level pressure with none of the subjects achieving AFL (SL; no-AFL). EELV (% of TLC, BTPS), was significantly larger during exercise at 3 ATA than during exercise at SL for the AFL group (SL = 44 +/- 6%; 3 ATA-AFL = 51 +/- 9%, P < 0.05; but, was not for the no-AFL group (SL = 46 +/- 6%; 3 ATA-no AFL = 46 +/- 7%). End inspiratory lung volume was significantly elevated during exercise at 3 ATA compared with SL in the AFL group (SL = 80 +/- 6%; 3 ATA-AFL = 86 +/- 6%; P = 0.01) but not in the no-AFL group (SL = 82 +/- 4%; 3 ATA-no AFL = 84 +/- 4%). Tidal volume and ventilation were not different for any condition. These data suggest that the occurrence of AFL influences the control of EELV.