Respiratory transfer impedance between 8 and 384 hz in guinea pigs
before and after bronchial challenge.
Sobh, Jamil F., Craig M. Lilly, Jeffrey M. Drazen, Andrew C. Jackson.
Respiratory Research Laboratory, Biomedical Engineering Department,
Boston University, Boston, MA. 02215, Combined Program in Pulmonary
and Critical Care Medicine, Department of Medicine, Brigham and
Women's Hospital, and Harvard Medical School, Boston, MA. 02115
APStracts 3:0455A, 1996.
We report a forced oscillatory technique for noninvasively measuring
respiratory transfer impedance (Ztr) between 8 and 384 Hz in guinea
pigs. This technique uses a device consisting of two chambers, one
surrounding the animal's head that is used as a plethysmograph to
measured flow through the airway opening , and the other which
surrounds the animal's body and is used to apply pressure
oscillations to the body surface (Pbs). Ztr was measured in
spontaneously breathing awake guinea pigs, and while anesthetized in
normal and methacholine challenged conditions. An 8-element model
consisting of an airway compartment separated from a tissue
compartment by a shunt gas compression compartment was fit to the
data. Anesthesia increased central airway resistance (Rcaw),
peripheral airway resistance (Rpaw), and bronchial airway wall
compliance (Cb) by 13%, 31% by 44%, respectively, whereas decreased
Ct by 37%. Compared to the unanesthetized condition, the methacholine
challenge (20[mu]g/kg) resulted in an increase in Rcaw and Rpaw (69%
and 319%, respectively) and a decrease in Cb and Ct (37% and 79%,
respectively). This technique is capable of measuring Ztr in
anesthetized and awake guinea pigs. Analysis of these data with this
8-element model provides reasonable estimates of airway and tissue
parameters.
Received 21 February 1996; accepted in final form 17 September
1996.
APS Manuscript Number A167-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996