Non-invasive lung function tests in rats with progressive papain-induced emphysema

Non-invasive plethysmographic methods for measurement of thoracic gas volume (TGV), airway resistance (Raw) and phase difference (PD) between flow rate at the nose and mean alveolar pressure were adapted for use in anesthetized rats. Thirty-six male Sprague-Dawley rats (200-250 g), were treated in groups of six by a single transoral, intratracheal instillation of 2 mg . kg-1 or 4 mg . kg-1 of papain in saline, or left untreated as controls. Measurements of TGV, Raw, and PD were made before treatment and at 4-day intervals after treatment for 8 or 16 days. TGV increased 65 percent by the fourth day and showed no change beyond the eighth day. Raw (0.4 +/- 0.04 cm H20 . ml-1 . sec) was not different from that of the controls. PD did not change significantly from the pretreatment value (4.7 +/0 0.41 degrees). The TGV, Raw, and PD responses were similar in the 2 mg . kg-1 and 4 mg . kg-1 papain treated rats. The TGV results suggest that the destructive effects of papain on the lungs are complete by the eighth day. The Raw results indicate that the airways are unaffected. The PD data are consistent with theoretical modeling studies for uneven distribution of compliances but neglible inequality of peripheral resistances.