PARTITIONING OF AIRWAY AND RESPIRATORY TISSUE MECHANICAL IMPEDANCES BY BODY PLETHYSMOGRAPHY

We have tested the feasibility of separating the airway (Zaw) and tiss ue (Zti) components of total respiratory input impedance (Zrs,in) in h ealthy subjects by measuring alveolar gas compression by body plethysm ography (Vpl) during pressure oscillations at the airway opening. The forced oscillation setup was placed inside a body plethysmograph, and the subjects rebreathed BTPS gas. Zrs,in and the relationship between Vpl and airway flow (Hpl) were measured from 4 to 29 Hz. Zaw and Zti w ere computed from Zrs,in and Hpl by using the monoalveolar T-network m odel and alveolar gas compliance derived from thoracic gas volume. The data were in good agreement with previous observations: airway and ti ssue resistance exhibited some positive and negative frequency depende nces, respectively; airway reactance was consistent with an inertance of 0.015 +/- 0.003 hPa . s(2) . l(-1) and tissue reactance with an ela stance of 36 +/- 8 hPa/l. The changes seen with varying lung volume, d uring elastic loading of the chest and during bronchoconstriction, wer e mostly in agreement with the expected effects. The data, as well as computer simulation, suggest that the partitioning is unaffected by me chanical inhomogeneity and only moderately affected by airway wall shu nting.