Journal of Applied Physiology, Vol 66, Issue 2 680-686, Copyright © 1989 by American Physiological Society
Human breathing pattern responses to loading with increased background impedance
A. Harver and J. A. Daubenspeck
Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03756.
We determined the influence of the background level of mechanical impedance
on the respiratory responses to very small mechanical loads, at or below
the threshold for conscious perception. We used a pseudorandom load
application technique to estimate the immediate pattern responses from the
zeroth lag of the cross correlation between the load application sequence
and the respiratory pattern components of tidal volume (VT), inspiratory
and expiratory time (TI and TE), and the instantaneous respiratory
frequency (f), minute ventilation (VI), and mean inspiratory flow (VT/TI).
Elevation of the background resistance served to reduce the TI and TE
responses to small perturbations in resistance from those in the control
background state, which resulted in generally smaller perturbations of f,
VI, and VT/TI. Elevation of the background elastance, however, served to
initiate a TI reduction not seen in the control state but did not
appreciably affect the rest of the pattern responses to the load
perturbations. Thus the neural reflexes involved in breath-by-breath
pattern regulation are modulated by the background level of the respiratory
impedance, as well as by the type and size of the load perturbation.
