Am. J. Respir. Crit. Care Med., Vol 149, No. 5, May 1994, 1227-1234.
Aminophylline and respiratory muscle interaction in normal humans
M Gorini, R Duranti, G Misuri, T Valenza, A Spinelli, P Goti, F Gigliotti and G Scano
Respiratory Research Unit, Fondazione Pro Juventute Don C. Gnocchi, Monte Oriolo, Universita di Firenze, Italy.
The effects of intravenous infusion of aminophylline on respiratory muscle
interaction were examined in seven normal subjects breathing at rest. Rib
cage (RC-Ap) and abdominal (AB-Ap) volume displacements, pleural (Ppl),
gastric (Pg), and transdiaphragmatic (Pdi) pressure swings, and
electromyographic activity of the diaphragm (Edi) and the parasternal (Eps)
muscles were measured under control and during infusion of either
aminophylline or placebo in a double-blind randomized manner. Compared with
placebo, aminophylline induced an increase in ventilation (p < 0.01)
that was mainly accounted for by an increase in tidal volume (p = 0.01).
Aminophylline induced a significant and similar increase in RC-Ap and AB-Ap
as associated with increased Ppl and Pg swings (p = 0.002, and p < 0.01,
respectively). On the contrary, no changes in end-expiratory RC and AB
volume and in Ppl and Pg at end-expiration were observed, indicating that
expiratory muscles did not contribute to the increase in tidal volume. Edi
and Eps increased significantly with aminophylline, whereas Pdi/Edi ratio
remained unchanged. We conclude that in normal humans breathing at rest:
(1) aminophylline increases ventilation, promoting larger tidal volume; (2)
this effect is due to increased neural drive to inspiratory muscles; (3)
aminophylline does not promote any appreciable expiratory muscle
recruitment and distortion in the pattern of chest wall motion.
