Journal of Applied Physiology, Vol 40, Issue 5 715-719, Copyright © 1976 by American Physiological Society
Factors affecting a single-breath N2 washout phase IV
K. Kaneko
A lung model was constructed to examine the effects of the following
factors on the phase IV of a single-breath N2 washout: the lung's
elasticity change with age, closing pressure (CP), regional volume (Volr)
distribution, pleural pressure, and gradient (Grad). The analysis revealed
1) when the CP was assumed to be + 1.0 cmH2O, predicted changes in closing
capacity (CC) due to alterations in elasticity agreed with previous
experimental results for individuals above 40 yr; for younger age groups,
the predicted values were apparently larger, suggesting the CP may be near
zero; 2) difference in Volr distribution alone caused alterations in CC and
the slope of phase IV; 3) for 1 cmH2O elevation of CP, closing capacity
/total lung capacity (CC/TLC) was predicted to increase about 8%; 4) for
0.1 cmHiO/cm Grad increase, CC/TLC was predicted to rise approximately 7%.
In conclusion, multiple factors affect phase IV.
