Journal of Applied Physiology, Vol 64, Issue 2 511-520, Copyright © 1988 by American Physiological Society
Steady-state response of normal subjects to an inspiratory sinusoidal pressure load
R. Sanii and M. Younes
Department of Medicine, University of Manitoba, Winnipeg, Canada.
Inspiratory duration (TI) increases during inspiratory resistive loading in
conscious humans. To ascertain whether this response is related to the
temporal pattern of pressure perturbation (reaching a peak in early or
midinspiration and declining subsequently) we compared the response of nine
normal subjects to a usual resistor (narrow tube, RES) with their response
when mouth pressure was reduced in a sinusoidal fashion during inspiration
(SIN). Whereas the negative pressure pattern was similar with both loads
(peak negative pressure near midinspiration), there was no relation between
pressure and flow in the case of sinusoidal loading. Each experiment
consisted of two loading periods, 4 min each, and three unloaded periods,
also 4 min each, bracketing the periods of loading. The order of RES and
SIN was randomized. TI during loading was compared with the average TI of
the preceding and following unloaded periods. TI increased 0.74 +/- 0.12
and 0.27 +/- 0.05 (SE) s during RES and SIN, respectively (P less than
0.01). We conclude that the temporal pattern of pressure change during
resistance breathing plays a small role in mediating the TI prolongation.
Coupling between flow and the pressure perturbation appears to be an
important determinant of TI prolongation.
