Active expiration and chronic intermittent hypoxia‐induced hypertension: A hypothesis that still breathes!

Reply: The two faces of active expiration: a case of mistaken identity!

“…As such we agree with the central tenet of the letter (Bazilio et al., ), which in effect draws a distinction between the phenomenon of active expiration (manifest as increased respiratory motor drive to abdominal muscles) and that of expiratory‐related sympathetic over‐activity (manifest as enhanced late‐expiratory activity in sympathetic pathways). Both phenomena are driven by the conditional expiratory oscillator of the parafacial respiratory group and typically present co‐incidentally in circumstances of increased ventilatory demand.…”

“…We are very grateful to Bazilio, Moraes, and Machado () for their letter drawing further attention to the topical and important issue of the mechanism(s) of chronic intermittent hypoxia‐induced hypertension. Our colleagues have generated a considerable body of work over the years, contributing, in no small way, to the contemporary understanding of the maladaptive effects of exposure to chronic intermittent hypoxia on cardiorespiratory control.…”

“…In any event, the upshot appears to be that active expiration proves an unreliable index of expiratory‐related sympathetic activity, and as suggested by Bazilio et al. (), recordings of sympathetic nerve activity in CIH‐exposed animals across the sleep–wake cycle are required to directly address the issue.…”