Airway dimensions of dog lungs by aerosols: comparison of bolus and single-breath techniques

ABSTRACT Monodisperse aerosols were used to determine airway dimensions as a function of volumetric lung depth in vivo. Two different techniques were compared in anesthetized mechanically ventilated dogs (mean body wt.± SD, 13.6 ± 0.9 kg). Monodisperse di-(2-ethyl-hexyl) sebacate particles (mean aerodynamic diameter±SD, 0.89±0.097 μm) were inhaled as bolus (half-width 8 ml) at 10-85% of the normalized (50% functional residual capacity, FRC) inspired volume (Bolus Technique). Alternatively, the total inspired volume contained the test aerosol, formally representing inspiration of a train of aerosol boluses of infinitesimal small volume (Single-Breath Technique). The particle concentration was continuously recorded at the airway opening by a miniaturized in-line aerosol photometer incorporating a 2 mW laser diode (λ = 820 nm) and a photodiode. The airway diameters determined at a given volumetric lung depth were related to the animal's total lung capacity (TLC) to account for lung volume differences between...