Journal of Applied Physiology, Vol 64, Issue 1 31-41, Copyright © 1988 by American Physiological Society
Breathing patterns in anesthetized cats and the concept of minimum respiratory effort
S. C. Luijendijk and J. Milic-Emili
Department of Medical Physiology, State University of Utrecht, The Netherlands.
Theoretical studies dealing with the principle of minimal respiratory
effort usually make use of sinusoidal or saw-tooth-like breathing patterns.
Recent observations in anesthetized cats have shown that the driving
pressure waveform for inspiration can be described by a power function of
time and that most of expiration is passive. This driving pressure
waveform, however, results in breathing patterns that differ from those
described above. For this reason, we have reevaluated in anesthetized cats
the principle of minimal respiratory effort by computing optimal duration
of inspiration (TI) and optimal tidal volume (VT) for different ventilatory
conditions using actual driving pressure waveforms. The results are in
qualitative agreement with the experimental observations; i.e., optimal TI
decreases and optimal VT increases with increasing minute ventilation. On
the average, a good agreement is found between measured and computed values
of TI. In some cats, however, there are substantial differences between
observed and predicted values of TI, which can probably be ascribed to
inaccuracies in the data used in our computations. Despite its limitations,
the present model analysis is more realistic than previous ones because
actual driving pressure waveforms are used together with actual values of
effective inspiratory impedance.
