Journal of Applied Physiology, Vol 48, Issue 6 921-926, Copyright © 1980 by American Physiological Society
Diaphragmatic function in healthy subjects during partial curarization
T. J. Gal and S. K. Goldberg
Diaphragmatic function estimated by transdiaphragmatic pressure (Pdi) was
studied in eight normal subjects during progressive partial paralysis with
d-tubocurarine (dTc). Dynamic Pdi was measured during quiet tidal
breathing, maximum deep inspiration, and 12-s maximum voluntary ventilation
(MVV). Maximum static transdiaphragmatic pressure (Pdimax) was also
measured during maximum static inspiratory efforts at four lung volumes.
The maximum effect of dTc at a cumulative dose of 0.2 mg/kg abolished
head-lift and handgrip ability. Pdimax at functional residual capacity was
decreased to 42% of its control value indicating significant diaphragmatic
weakness at this level of curarization. The weakness had no inpact on quiet
breathing and a moderate effect on maximum inspiration. In either case Pdi
represented an increasing fraction of Pdimax. MVV fell significantly before
the Pdi during the maneuver decreased. This decreased MVV in curarized
subjects reflects upper airway obstruction caused by pharyngeal muscle
weakness and the diminished contribution of the other respiratory muscles
that are important at high levels of ventilatory effort but more sensitive
to effects of dTc.
