Am. J. Respir. Crit. Care Med., Vol 155, No. 1, 01 1997, 181-185.
Broxaterol increases force output of fatigued canine diaphragm more than salbutamol
E Derom, G Gayan-Ramirez, G Gurrieri, V de Bock and M Decramer
Respiratory Muscle Research Unit, Laboratory of Pneumology, Katholieke Universiteit Leuven, Belgium.
We previously demonstrated that broxaterol enhanced recovery of fatigued
canine diaphragm. The aim of this study was to compare the inotropic
effects of salbutamol and broxaterol on fatigued canine diaphragm.
Low-frequency fatigue was induced in 14 mongrel dogs by electrophrenic
stimulation, which was continued until transdiaphragmatic pressure (Pdi) at
20 Hz was reduced by 50% or for 1 h. After stabilization of fatigue, the
animals received a bolus (18.5 microg/kg) of either broxaterol or
salbutamol, followed by a continuous infusion (0.43 microg/kg/min). A
second bolus of 74.0 microg/kg, followed by a continuous infusion of 1.72
microg/kg/min, was given after 90 min. Both drugs significantly increased
twitch Pdi. Twitch Pdi measured 90 min after the first and second doses of
broxaterol increased by 28 +/- 23% and 42 +/- 34%, respectively, whereas
the salbutamol-induced increase was clearly smaller (9 +/- 10% and 17 +/-
15%, respectively). Broxaterol increased Pdi at 20 Hz by 25 +/- 28% with
the first dose and by 29 +/- 21% with the second dose. In contrast,
salbutamol did not alter Pdi at 20 Hz. Neither drug affected Pdi at 100 Hz.
We conclude that broxaterol promoted recovery of low- frequency fatigue of
the canine diaphragm in vivo in a dose-dependent manner, whereas salbutamol
only minimally improved force production by the fatigued diaphragm.
