Determination of functional residual capacity with 133-xenon radiospirometry. Comparison with body plethysmography and helium spirometry. Effect of body position

This study was undertaken to estimate the accuracy of 133-xenon radiospirometry for determination of FRC in healthy subjects. Forty healthy volunteers, both smokers and non-smokers, were examined. The FRC of each subject was concurrently determined with radiospirometric, He-dilution in closed circuit, and body plethysmographic methods. The radiospirometric and He-dilution measurements were done in supine and in sitting positions, the body plethysmography on sitting subjects, only. The mean FRC measured by radiospirometry (FRCRS) was 0.721 larger than that measured by helium spirometry (FRCHe) in sitting position (P<0.01). In supine position the FRCRS was 0.65 I larger than the FRCHe (p<0.01). The body plethysmography gave FRC (TGV) 0.35 I larger than the FRCHe sitting (P<0.01). The FRCHe and the FRCR≥ in the sitting position were 0.48 and 0.55 I larger than in the supine position (P<0.01), respectively. Trapped air correlated significantly (P<0.01) with the difference FRCRS-FRCHe, when sitting. The result...