Partitioning of airway and respiratory tissue mechanical impedances by body plethysmography

Peslin, R., and C. Duvivier. Partitioning of airway andrespiratory tissue mechanical impedances by body plethysmography. J. Appl. Physiol. 84(2): 553-561, 1998.We have tested the feasibility of separating the airway (Zaw)and tissue (Zti) components of total respiratory input impedance(Zrs,in) in healthy subjects by measuring alveolar gas compression bybody plethysmography (Vpl) during pressure oscillations at the airwayopening. The forced oscillation setup was placed inside a bodyplethysmograph, and the subjects rebreathedBTPS gas. Zrs,in and the relationship between Vpl and airway flow (Hpl) were measured from 4 to 29 Hz. Zawand Zti were computed from Zrs,in and Hpl by using the monoalveolar T-network model and alveolar gas compliance derived from thoracic gasvolume. The data were in good agreement with previous observations: airway and tissue resistance exhibited some positive and negative frequency dependences, respectively; airway reactance was consistent with an inertance of 0.015 ± 0.003 hPa · s² · l¹and tissue reactance with an elastance of 36 ± 8 hPa/l. The changes seen with varying lung volume, during elastic loading of the chest andduring bronchoconstriction, were mostly in agreement with the expectedeffects. The data, as well as computer simulation, suggest that thepartitioning is unaffected by mechanical inhomogeneity and onlymoderately affected by airway wall shunting.