Title

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

Document Type

Journal Article

PubMed ID

30521426

Publisher

American Physiological Society

School

School of Medical and Health Sciences

Comments

Originally published as: Luu, B. L., McBain, R. A., Taylor, J. L., Gandevia, S. C., & Butler, J. E. (2019). Reflex response to airway occlusion in human inspiratory muscles when recruited for breathing and posture. Journal of Applied Physiology, 126(1), 132-140. Original article available here

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 motoneuron 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 liters. The reflex response was measured in the scalene and sternocleidomastoid muscles during 1) a control condition with the head supported in space and the muscles recruited for breathing only, 2) a postural condition with the head unsupported and the neck flexors recruited for both breathing and to maintain head posture, and 3) a large-breath condition with the head supported and the volume threshold raised to between 0.8 and 1.0 liters to increase inspiratory muscle activity. When normalized to its preocclusion 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 with 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 motoneuron pool and that afferent inputs for this reflex most likely act via intersegmental networks of premotoneurons rather than at a motoneuronal level. © 2019 the American Physiological Society

DOI

10.1152/japplphysiol.00841.2018

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