RESUMO
Respiratory mechanics were studied in nine intubated dogs before and after exposure to aerosolized papain under conditions known to produce emphysemalike lesions. Forced oscillatory resistance (RFO), compliance (CFO), and inertance (IFO) were computed from impedance data obtained at transrespiratory pressures of -10, 0 (FRC), +10, and +20 cmHWO. Dynamic compliance during tidal breathing (CTB) was also measured at FRC. After papain exposure CTB and CFO increased by 25% (P less than 0.05) at FRC and at +10 cmH2O. There were no consistent changes in RFO or IFO at FRC. However, RFO showed a greater dependency on transrespiratory pressure, which suggests that the elastic properties of airways may also have been affected by papain. Measurements made in open-chested papain-exposed animals showed that about 17% of total RFO and 20% of total elastance were attributable to the chest wall. Forced oscillatory impedance data are sensitive to experimental changes in lung mechanics and provide useful estimates of standard respiratory parameters.
