The effect of bupivacaine aerosol on the activity of pulmonary stretch and 'irritant' receptors.

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Abstract
Experiments were done on anesthetized, paralysed and artificially ventilated cats. Vagal single afferent fibers showing discharges in phase with respiration were isolated in the neck. Two types of fibers were studied at different tidal volumes: showing slowly adapting discharges from the pulmonary stretch receptors; showing rapidly adapting discharges from the lung irritant receptors. The effect of bupivacaine aerosol, administered by positive pressure inflations, was recorded on the pattern of fiber discharge. The pulmonary stretch fibers were further classified into low-threshold and higher-threshold fibers according to the standard criteria. Bupivacaine aerosol blocked activity in all the low-threshold and in the majority of the higher-threshold fibers. Of the rapidly adapting fibers, bupivacaine completely blocked activity at some tidal volumes and markedly reduced it at most others. The fiber activity data are presented. Although bupivacaine aerosol markedly reduced impulse activity in all 3 types of fibers, the data suggest that there is a small difference in the ease with which low-threshold fibers and higher-threshold and irritant fibers are affected. The reasons for this difference in the behavior are not understood.