Pattern of recovery from diaphragmatic fatigue over 24 hours.
Laghi, Franco, Nausica D'alfonso, Martin J. Tobin.
Division of Pulmonary and Critical Care Medicine, Edward Hines Jr.
Veterans Administration Hospital, and Loyola University of Chicago
Stritch School of Medicine, Hines, Illinois 60141
APStracts 2:0146A, 1995.
The rate of recovery from diaphragmatic fatigue beyond 1 hr is
unknown. To investigate this question, we studied 12 healthy subjects
and measured transdiaphragmatic twitch pressure (Pditw) using
magnetic stimulation of the phrenic nerves. Measurements were
obtained at baseline and following a fatigue protocol consisting of
inspiratory resistive loading in which subjects generated 60% of
maximal transdiaphragmatic pressure until task failure. At baseline
Pditw was 38.9+/-1.1 (SE) cm H2O, and it fell to 25.1+/-0.6 cm H2O at
10 min (p<0.01) after conclusion of the fatigue protocol. Pditw
increased to 27.6+/-0.9, 31.6+/-1.1, and 32.7+/-1.2 cm H2O at 1, 8
and 24 hr, respectively, after conclusion of the fatigue protocol --
the 24 hr value was significantly (p<0.01) lower than baseline. The
nadir in Pditw after the protocol was delayed by 10 min. In separate
experiments, we showed that this delay was probably due to the
development of twitch potentiation as a result of forceful
diaphragmatic contractions during the fatigue protocol. In
conclusion, induction of diaphragmatic fatigue with this experimental
protocol produced a marked decrease in diaphragmatic contractility
that persisted for at least 24 hr.
Received 12 July 1994; accepted in final form 21 March 1995.
APS Manuscript Number A698-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.