Pulmonary function tests in excised dog lungs with small airway obstruction by beads

About 100 beads, 2 mm in diameter were wedged into the small airways of excised dog lungs. Pulmonary function tests were performed in the lungs before and after the obstruction of the small airway with beads. Of the pulmonary function tests performed, lung pressure-volume curve, lung resistance-lung volume relationship, frequency dependency of dynamic compliance, closing volume, and N2 multiwashout curve did not show any significant alteration after small airway obstruction. Only the flow-volume curve at low lung volume showed any significant alteration. This suggests that the flow-volume curve is the most sensitive pulmonary function test in the detection of early obstructive impairment of the small airways.