Mechanical output impedance of the lung determined from cardiogenic oscillations.
Bijaoui, Eve, Pierre F. Baconnier, and Jason H. T. Bates.
Meakins-Christie Laboratories, McGill University, Montreal, Quebec, H2X 2P2,
Canada; TIMC IMAG Laboratory, UMR CNRS 5525, Grenoble, France; and Vermont
Lung Center, Department of Medicine, University of Vermont, Burlington, Vermont
APStracts 8:0268A, 2001.
The beating heart naturally oscillates the lung because of the close juxtaposition, between
these organs producing cardiogenic oscillations in flow that can be measured at the
mouth when the glottis is open. Correspondingly, if the mouth is occluded, the same
phenomenon produces cardiogenic pressure oscillations that can be measured just distal
to the site of occlusion. The Fourier-domain ratio of these oscillations in pressure and
flow constitutes what we call cardiogenic respiratory impedance (Zc). We calculated Zc
between about 1.5 and 10 Hz in relaxed normal subjects at functional residual capacity
with open glottis. Zc was insensitive to heart rate changes induced by exercise and had an
imaginary part close to zero at all frequencies investigated. Its real part was similar to or
smaller than resistance determined by the forced oscillation technique. We speculate that
Zc measures the flow resistance of the central and upper airways of the lung. Zc may be
useful as a means of obtaining information about lung mechanics without the need for an
external source of flow perturbations.
Received 2 November 2000; accepted in final form 16 April 2001
APS Manuscript Number A1026-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 18 June 2001