Site of deposition and factors affecting clearance of aerosolized solute from canine lungs

Abstract

The influence of several factors on lung solute clearance were determined using aerosolized 99mTc-diethylenetriaminepentaacetate. A jet nebulizer-plate separator-balloon system was used to generate particles with an activity median aerodynamic diameter of 1.1 .mu.m, administered the aerosol in a standard fashion, and determined clearance half times (t1/2) with a .gamma.-scintillation camera. The following serial studies were performed in 5 anesthetized, paralyzed, intubated, mechanically ventilated dogs: control, with ventilatory frequency (f) = 15 breaths/min and tidal volume (VT) = 15 ml/kg during solute clearance; repeat control, for reproducibility; increased frequency, with f = 25 breaths/min and VT = 10 ml/kg; positive end-expiratory pressure (PEEP) of 10 cmH2O; unilateral pulmonary arterial occlusion (PAO); and bronchial arterial occlusion (BAO). Control t1/2 was 25 .+-. 5 min and did not change in the repeat control, increased frequency, or BAO experiments. PEEP markedly decreased t1/2 to 13 .+-. 3 min (P < 0.01), and PAO increased it to 37 .+-. 6 min (P < 0.05). Clearance from the lungs by this method is uninfluenced by increased frequency, increases markedly with PEEP, and depends on pulmonary, not bronchial, blood flow.