ISCHEMIA POTENTIATES THE REFLEX BRONCHODILATION EVOKED BY STATIC MUSCULAR-CONTRACTION IN DOGS

In eleven anesthetized dogs, we found that static contraction of hindlimb muscles that were freely perfused decreased total lung resistance by 0.7 ± 0.1 cm H2O·L-1·sec, whereas static contraction of the same muscles rendered ischemic decreased total lung resistance by 1.5±0.4 cm H2O·L-1·sec (P < 0.025). In ten other dogs, we found that static contraction of freely perfused hindlimb muscles decreased total lung resistance by 0.9 ± 0.2 cm H2O·L-1·sec, whereas dynamic contraction of the same freely perfused muscles decreased total lung resistance by 1.1 ± 0.3 cm H2O·L-1·sec. The difference in the magnitudes of the bronchodilator responses of the two modes of contraction was not significant (P > 0.05). We conclude that a mismatch between blood supply and demand in working skeletal muscle increases the reflex bronchodilator response to static contraction. We also conclude that dynamic contraction evokes a reflex bronchodilation equivalent to that evoked by static contraction provided that the tension produced by the two modes of contraction are equal. © 1990.