Journal of Applied Physiology, Vol 69, Issue 2 747-755, Copyright © 1990 by American Physiological Society
Measurement of phase I volume breath by breath in spontaneously breathing guinea pigs
T. Gaertner and W. K. Barnikol
Institut fur Physiologie und Pathophysiologie, Johannes Gutenberg-Universitat, Mainz, Federal Republic of Germany.
A new method to determine phase I volume in tracheotomized spontaneously
breathing guinea pigs is presented. Measurements were performed in three
animals weighing 567-896 g. In simultaneous tracings of tidal volume (VT)
and expiratory profiles of endogenous gases (PO2 or PCO2), the phase I
volume of each breath was determined graphically as the volume expired up
to the end of phase I of the expirogram. The mean phase I volume of
different animals ranged from 0.29 to 0.43 ml with an arithmetic dispersion
between 0.014 and 0.021 ml. Spontaneous sighs sometimes with doubling of
the VT caused a significant rise of phase I volume up to 50% of the normal
values. The linear regression curve was calculated for corresponding VT's
and phase I volumes. The VT gradient of the phase I volume as the slope of
this curve ranged from 0.108 to 0.217 ml/ml VT. The results of the new
procedure, which works also with humans and rabbits, are discussed in
respect to improvement of the characterization of the bronchial system.
Compared with the human system, the VT gradient of the guinea pig is four
times greater. By not being affected by disorders in pulmonary gas
exchange, the phase I volume determined as described is a new suitable
quantity to specifically assess actions and reactions of the bronchial
system.
