FORCED OSCILLATORY RESPIRATORY PARAMETERS FOLLOWING PAPAIN EXPOSURE IN DOGS

Respiratory mechanics were studied in nine intubated dogs before and after exposure to aerosolized papain under conditions known to produce emphysema-like 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 cm H2O. Dynamic compliance during tidal breathing (CTB) was also measured at FRC. After papain exposure CTB and CFO increased by 25% (P < 0.05) at FRC and at +10 cm H2O. 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.