Assessment of respiratory pressure-volume non linearity in rabbits
during mechanical ventilation.
Peslin, R., M. Rotger, R. Farr[acute]e, and D. Navajas.
Lab. Biofisica i Bioenginyeria, Facultat de Medicina, Universitat
de Barcelona, Spain, and Unit[acute]e 14 de Physiopathologie
Respiratoire, Institut National de la Sant[acute]e et de la Recherche
M[acute]edicale. Vandoeuvre-les-Nancy, France
APStracts 2:0553A, 1995.
The volume dependence of respiratory elastance makes it difficult to
recognize actual changes in lung and chest wall elastic properties in
artificially ventilated subjects. We have assessed in six
anesthetized, tracheotomized and paralyzed rabbits if reliable
information on the static pressure-volume (P-V) curve could be
obtained from recordings performed during step variations of the end
-expiratory pressure (EEP), without interrupting mechanical
ventilation. Pressure and flow data recorded during 5 and 10 hPa
positive pressure steps were analyzed in the time domain with a non
-linear model featuring a sigmoid P-V curve, and with a model which,
in addition, accounted for tissue viscoelastic properties. The later
fitted the data substantially better. Both models provided reasonably
reproducible coefficients, but the P-V curves obtained from the 5 and
10 hPa steps were systematically different. When the P-V curves were
used to predict effective elastance (Ers), the best predictor was the
curve derived from the 10 hPa step with the visco-elastic model:
unsigned differences averaged 8.6+/-11.1 %, 26.9+/-36.4 % and 5.5+/
-5.8 % at EEPs of 0, 5 and 10 hPa, respectively. This approach
provides potentially useful, although not highly accurate, estimates
of Ers volume dependence.
Received 3 October 1995; accepted in final form 6 December 1995.
APS Manuscript Number A1068-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95