Journal of Applied Physiology, Vol 38, Issue 1 39-43, Copyright © 1975 by American Physiological Society
Effect of added elastances on the first loaded breath in man
L. D. Pengelly, J. Greener, I. Bowmer, A. Luterman and J. Milic-Emili
Tidal volume together with end-inspiratory pressure was measured in four
seated healthy men, during normal breathing and during single inspirations
taken from a series of rigid containers which provided added elastances
(range: 5-70 cmH2O/l). Experiments were performed both during quiet
breathing and during ventilation increased by added dead space. Added
elastic loads always resulted in a decreased tidal volume. This decrease
was partly compensated by increased pressure developed by the inspiratory
muscles; being more so with greater added elastance, control ventilation,
or both. Analysis of our results indicates that the load-compensatory
response may be attributed to changes in mechanical impedance of the
ventilatory pump, due to the mechanical arrangement and the intrinsic
properties of the inspiratory muscles (force-length and force-velocity
relationships), changes in respiratory frequency with increasing
ventilation, and to vagally mediated load compensation.
