Influence of sequential breath-holding on the slope of phase III
Bélanger, J.; Cormier, Y.
Bulletin Europeen de Physiopathologie Respiratoire 17(1): 65-74
1981
ISSN/ISBN: 0395-3890 PMID: 7470686 Document Number: 174776
Many factors contribute to the slope of phase III of the single-breath N2 test (SB-N2). By its effect on N2 concentrations, alveolar O2 exchange may be responsible for a fraction of this slope. Slope of phase III is steeper when expiratory time is prolonged. The effect of 2 sequential breath-holding periods of 20 s each was studied in 10 healthy young men, by SB-N2 and a reverse technique (SB-R). A sudden increase (mean 1.27%) in the expired N2 concentration was observed after each breath-holding period. Closing volume remained the same in all tests, but the slope of phase IV decreased by 44% in SB-N2A (SB-N2 with breath-holding) and increased by 55% in SB-RA. Expiratory vital capacity was significantly less after breath-holding. Apparently, gas exchange during expiration is partly responsible for the slope of phase III.