Am. J. Respir. Crit. Care Med., Vol 149, No. 6, 06 1994, 1545-1549.
The effect of aminophylline on the force-length characteristics of the diaphragm
T Wanke, M Merkle, U Zifko, D Formanek, H Lahrmann, W Grisold and H Zwick
Pulmonary Department, Lainz Hospital, Vienna, Austria.
The aim of our study was to evaluate the effect of aminophylline on the
contractile function of the human diaphragm during varying muscle fiber
length. Ten healthy subjects were studied during maximal sniff maneuvers
and bilateral phrenic nerve twitch stimulations, with and without
intravenous infusion of aminophylline in a randomized fashion. The
transdiaphragmatic pressures generated at various baseline lung volumes,
from residual volume to 90% of total lung capacity, were recorded before
and after the induction of diaphragm exhaustion. At all levels of lung
volume, aminophylline did not have an effect on the contractility of the
fresh diaphragm. In the exhausted diaphragm, however, the pressure values,
induced by sniffs and twitch stimulations, were significantly improved by
aminophylline. This positive effect on diaphragm contractility was also
impressive at 60, 75, and 90% of total lung capacity. This indicates that
aminophylline significantly improves the contractile function of the
exhausted human diaphragm, even if the muscle fibers are shorter than
optimal. This effect occurs regardless of the neuronal firing rate, whether
it is low (twitch stimulation) or high (sniff maneuver).
