Differential responses of global airway, terminal airway and tissue
impedances to histamine.
Hantos, Z., F. Pet[acute]ak, A. Adamicza, B. Dar[acute]oczy, and J. J.
Fredberg.
Departments of Medical Informatics and Experimental Surgery, Albert
Szent-Gy[diaeresis]orgyi Medical University, H-6720 Szeged, Hungary;
and Department of Environmental Health, Harvard School of Public
Health, Boston, Massachusetts 02115
APStracts 2:0269A, 1995.
The forced oscillation and alveolar capsule techniques were applied to
determine the input impedance of the lungs (ZL) and the airway
transfer impedances (Ztaw) between 0.2 and 20 Hz, in 6 open-chest
dogs in the control state, during i.v. infusion of histamine at 7
rates between 0.25 and 16 [mu]g/kg/min, and after infusion. In each
condition, the input impedances seen from the alveolar capsules (Zc)
were measured by imposing 2-to-200 Hz oscillations from the capsules
(Davey and Bates: Respir. Physiol. 91: 165-182, 1993). Airway
resistance (Raw) and inertance, and tissue damping (G) and elastance
(H) were derived from the ZL data. For all dogs, histamine
progressively increased Raw and the real part of Ztaw (Rtaw),
reaching at 16 [mu]g/kg/min 241+/-109(SD)% and 370+/-186%,
respectively, of the control values, but caused greater, although
locally highly variable, increases (769+/-716% of the control) in the
real part of Zc extrapolated to zero frequency (Ro). With increasing
dose of histamine, the changes in Ro always preceded those in Raw and
Rtaw, implying that bronchoconstriction developed first in the lung
periphery. It is therefore concluded that the measurement of Zc
offers a sensitive method for the detection of early nonuniform
responses to bronchoconstrictor stimuli which are not yet reflected
by the values of the overall Raw. In half of the cases, significant
increases in G and H occurred before any change in Ro; this suggests
that the mechanisms of airways and parenchymal constrictions may be
unrelated.
Received 24 August 1994; accepted in final form 13 June 1995.
APS Manuscript Number A884-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.