Journal of Applied Physiology, Vol 60, Issue 5 1482-1492, Copyright © 1986 by American Physiological Society
Steady-state response of quadriplegic subjects to inspiratory resistive load
V. Im Hof, H. Dubo, V. Daniels and M. Younes
Normal subjects preserve tidal volume (VT) in the face of added inspiratory
resistance by increasing maximal amplitude and duration of the rising phase
of respiratory driving pressure (DP) and by changing the shape of this
phase to one that is more concave to the time axis. To explore the possible
role of chest wall afferents in mediating these responses, we determined
averaged DP in eight quadriplegic subjects during steady-state unloaded
breathing and while breathing through an inspiratory resistance (8.5 cmH2O
X 1(-1) X s). As with normal subjects, quadriplegics preserved VT (loaded
VT = 106% control) by utilizing all three mechanisms. However, prolongation
of the inspiratory duration derived from the DP waveform (+22% vs. +42%)
and shape response were significantly less in the quadriplegic subjects.
Shape response was completely absent in subjects with C4 lesions. The
results provide strong evidence that respiratory muscle spindles are
responsible for shape response and that changes in afferent feedback from
the chest wall play an important role in mediating inspiratory
prolongation.
