Reflex response to airway occlusion in human inspiratory muscles when recruited for breathing and posture.

Reflex response to airway occlusion in human inspiratory muscles when recruited for breathing and posture.

J Appl Physiol (1985). 2018 Dec 06;:

Authors: Luu BL, McBain RA, Taylor JL, Gandevia SC, Butler JE

Abstract
Briefly occluding the airway during inspiration produces a short-latency reflex inhibition in human inspiratory muscles. This occlusion reflex seems specific to respiratory muscles; however, it is not known whether the reflex inhibition has a uniform effect across a motoneurone pool when a muscle is recruited concurrently for breathing and posture. In this study, participants were seated and breathed through a mouthpiece that occluded inspiratory airflow for 250 ms at a volume threshold of 0.2 l. The reflex response was measured in the scalene and sternocleidomastoid muscles during (i) a control condition with the head supported in space and the muscles recruited for breathing only, (ii) a postural condition with the head unsupported and the neck flexors recruited for both breathing and to maintain head posture, and (iii) a large-breath condition with the head supported and the volume threshold raised to between 0.8-1.0 l to increase inspiratory muscle activity. When normalized to its pre-occlusion mean, the reflex response in the scalene muscles was not significantly different between the large-breath and control conditions, whereas concomitant recruitment of these muscles for posture control reduced the reflex response by half compared to the control condition. A reflex response occurred in sternocleidomastoid when it contracted phasically as an accessory muscle for inspiration during the large-breath condition. These results indicate that the occlusion reflex does not produce a uniform effect across the motoneurone pool, and that afferent inputs for this reflex most likely act via intersegmental networks of pre-motoneurones rather than at a motoneuronal level.

PMID: 30521426 [PubMed - as supplied by publisher]

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