Journal of Applied Physiology, Vol 39, Issue 4 541-547, Copyright © 1975 by American Physiological Society
Effective respiratory system elastance during positive-pressure breathing in supine man
W. T. Josenhans, T. A. Peacocke and G. Schaller
Two healthy males relaxing supine on a ballistobed were mechanically
ventilated at positive end-expiratory pressures (PEEP) from 0 to 19 cmH2O.
Pressures at the airway opening, middle esophagus, and stomach were
monitored, together with tidal volume (VT) and ballistobed displacement.
The effective elastance (i.e., sum of active and passive components) of the
respiratory system (E'rs) and its components--abdominal muscle (E'ab),
diaphragm (E'di), and rib cage (E'rc)--were calculated. With increasing
PEEP, lung compliance increased slightly, E'rc and E'di decreased linearly,
and E'ab increased linearly. The combined effective elastance of abdomen
and diaphragm (E'ab+di) first decreased and then increased again. The
abdomen-diaphragm contribution to VT during mechanical ventilation was
approximately half that of spontaneous breathing.
