Journal of Applied Physiology, Vol 60, Issue 2 630-637, Copyright © 1986 by American Physiological Society
Aerosol deposition and flow limitation in a compliant tube
W. D. Christensen and D. L. Swift
Studies in intact dogs have suggested that aerosol deposition is enhanced
in the proximity of a flow-limiting segment (FLS) formed during cough. The
mechanism for that observation was investigated using a monodisperse
(geometric SD less than or equal to 1.15) fluorescent aerosol produced in a
condensation generator. The aerosol was passed through a compliant tube
(Penrose) that had been mounted vertically in a two-chamber box. The
surrounding pressure (Ps) in the upstream chamber was controlled
independent of the surrounding pressure in the downstream chamber, thus
allowing development of an FLS near the exit of the upstream chamber. At
fixed inlet pressure (P1) and Ps, flow limitation was achieved over a range
of 0.1-0.5 l X s-1 by lowering downstream pressure alone (P2). The
influence of the FLS cross-sectional geometry on the site of peak
deposition was examined because area of an FLS is a function of transmural
pressure (Ptm = Px - Ps). For those constriction geometries that did not
involve opposing wall contact, the deposition distribution was
characterized by a single peak immediately downstream of the constriction.
In the most compressed geometries the peak in deposition was diminished and
shifted further downstream. Total aerosol deposition was found to be
characterized by a dimensionless particle inertia parameter formed as the
ratio of particle stopping distance and the minor radius of the elliptical
tube cross section. The deposition of small particles with an inertial
parameter less than 0.01 was found to be independent of geometry and
constriction velocity.(ABSTRACT TRUNCATED AT 250 WORDS)
