PubMed1983
The variability of quasistatic lung inspiratory and expiratory pressure-volume (P-V) curves has been investigated in 8 young healthy volunteers studied on 4 occasions. The reproducibility of the total lung capacity (TLC) measured by body plethysmography was good, with a mean coefficient of variation of 1.8 +/- 0.9% (SD). The following variables were calculated from the P-V curves: the recoil pressures measured at TLC and 90, 80, 70, 60, and 50% TLC, as well as the compliance at functional residual capacity. For all the variables considered the intraseries variance was similar to the interseries variance so that all the individual results were pooled together. For each variable a coefficient of variation was calculated for each subject, as well as an F ratio to compare the interindividual differences to the intraindividual differences. For the variables obtained from the expiratory P-V curve, the lowest coefficient of variation was found for elastic lung recoil pressure, 90% TLC (6.6 +/- 2.6%, mean +/- SD). The reproducibility of the inspiratory P-V curve was found to be somewhat better than that of the expiratory one, with a coefficient of variation of 3.4 +/- 0.8% at 90% TLC. In absolute terms at that same level, the mean standard error of measurements was 1.2 cm H2O for the expiratory curves and 0.8 cm H2O for the inspiratory ones. It is concluded that in terms of reproducibility the best index of lung elasticity is the recoil pressure measured at 90% TLC and that the inspiratory curve is even better than the expiratory one.