On-line laser-photometric monitoring of aerosol deposition in
ventilated rabbit lungs.
Schmehl, Th, J. Gebhart, H. Sch[umlaut]utte, A. Scharmann, and W.
Seeger.
Department of Internal Medicine, Justus-Liebig-University Giessen,
Klinikstrasse 36, D-35385 Giessen; I. Physikalisches Institut,
Justus-Liebig-University Giessen, Heinrich-Buff-Ring 16, D-35392
Giessen, and GSF-Forschungszentrum f[umlaut]ur Umwelt und Gesundheit,
Paul-Ehrlich-Strasse 20, D-60596 Frankfurt a. M.
APStracts 2:0419A, 1995.
A photometric technique was developed for on-line measurement of
aerosol deposition in isolated, ventilated and perfused rabbit lungs.
A jet nebulizer was used for aerosolization of saline (hygroscopic
particles) and di-2-ethylhexyl sebacate (non-hygroscopic particles).
Aerosol concentration (laser photometer, constructed for measurements
in rabbit lungs) and flow rate (commercial pneumotachograph) were
continuously monitored at the inlet of the tracheal cannula.
Computer-assisted data processing allowed the breath-by-breath
calculation of inhaled and exhaled aerosol mass, thus providing the
deposition fraction. When using hygroscopic particles, however, this
approach was hampered by the humidity-induced particle growth in the
airways, leading to an overestimation of the aerosol concentration in
exhaled air. This effect was corrected by an algorithm using a
'particle growth factor' derived breath-by-breath from the photometer
signal. To test the reliability of this approach, saline particles
carrying 99mTc label were aerosolized into rabbit lungs with the use
of various ventilator settings, and the aerosol deposition was
assessed in parallel by photometry and by radioactivity detection
over the lung and over a trap in the exhaled air circuit.
Superimposable curves of cumulative aerosol deposition, with changes
in kinetics dependent on the ventilator mode, were obtained. For a
given ventilator setting, absolute values of the deposition fraction
were 0.32?+/-?0.04 (radiotracer quantification) and 0.36?+/-?0.04
(photometry) (mean +/- SD; n=4). We conclude that the presented
laser-photometric technique allows reliable on-line monitoring of the
deposition of both non-hygroscopic and hygroscopic aerosol particles
in ventilated lungs.
Received 5 January 1995; accepted in final form 15 August 1995.
APS Manuscript Number A14-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95