Breathing mechanics during exercise with added dead space reflect mechanisms of ventilatory control

Helen E. Wood; Gordon S. Mitchell; Tony G. Babb

doi:10.1016/j.resp.2009.07.001

Breathing mechanics during exercise with added dead space reflect mechanisms of ventilatory control

Helen E. Wood, Gordon S. Mitchell, Tony G. Babb

Research output: Contribution to journal › Article › peer-review

9 Scopus citations

Abstract

Small increases in external dead space (V_D) augment the exercise ventilatory response via a neural mechanism known as short-term modulation (STM). We hypothesized that breathing mechanics would differ during exercise, increased V_D and STM. Men were studied at rest and during cycle exercise (10-50 W) without (Control) and with added V_D (200-600 ml). With added V_D, V_T increased via increased end-inspiratory lung volume (EILV), with no change in end-expiratory lung volume (EELV), indicating recruitment of inspiratory muscles only. With exercise, V_T increased via both decreased EELV and increased EILV, indicating recruitment of both expiratory and inspiratory muscles. A significant interaction between the effects of exercise and V_D on mean inspiratory flow indicated that the augmented exercise ventilatory response with added V_D (i.e. STM) resulted from increased drive to the inspiratory muscles. These results reveal different patterns of respiratory muscle recruitment among experimental conditions. Hence, we conclude that fundamental differences exist in the neural control of ventilatory responses during exercise, increased V_D and STM.

Original language	English (US)
Pages (from-to)	210-217
Number of pages	8
Journal	Respiratory Physiology and Neurobiology
Volume	168
Issue number	3
DOIs	https://doi.org/10.1016/j.resp.2009.07.001
State	Published - Sep 30 2009

Keywords

End-expiratory lung volume
Exercise hyperpnea
Hypercapnia
Lung volumes
Modulation
Plasticity
Respiratory control
Respiratory muscle recruitment

ASJC Scopus subject areas

General Neuroscience
Physiology
Pulmonary and Respiratory Medicine

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10.1016/j.resp.2009.07.001

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title = "Breathing mechanics during exercise with added dead space reflect mechanisms of ventilatory control",

abstract = "Small increases in external dead space (VD) augment the exercise ventilatory response via a neural mechanism known as short-term modulation (STM). We hypothesized that breathing mechanics would differ during exercise, increased VD and STM. Men were studied at rest and during cycle exercise (10-50 W) without (Control) and with added VD (200-600 ml). With added VD, VT increased via increased end-inspiratory lung volume (EILV), with no change in end-expiratory lung volume (EELV), indicating recruitment of inspiratory muscles only. With exercise, VT increased via both decreased EELV and increased EILV, indicating recruitment of both expiratory and inspiratory muscles. A significant interaction between the effects of exercise and VD on mean inspiratory flow indicated that the augmented exercise ventilatory response with added VD (i.e. STM) resulted from increased drive to the inspiratory muscles. These results reveal different patterns of respiratory muscle recruitment among experimental conditions. Hence, we conclude that fundamental differences exist in the neural control of ventilatory responses during exercise, increased VD and STM.",

keywords = "End-expiratory lung volume, Exercise hyperpnea, Hypercapnia, Lung volumes, Modulation, Plasticity, Respiratory control, Respiratory muscle recruitment",

author = "Wood, {Helen E.} and Mitchell, {Gordon S.} and Babb, {Tony G.}",

note = "Funding Information: The authors sincerely thank the subjects who participated in this study, and M. Klocko, K. Ranasinghe, R. MacDougall and R. Harris, who assisted with data collection and analysis. This work was funded by Texas Health Presbyterian Hospital Dallas, the King Charitable Foundation Trust, and the Cain Foundation.",

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AU - Mitchell, Gordon S.

AU - Babb, Tony G.

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PY - 2009/9/30

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N2 - Small increases in external dead space (VD) augment the exercise ventilatory response via a neural mechanism known as short-term modulation (STM). We hypothesized that breathing mechanics would differ during exercise, increased VD and STM. Men were studied at rest and during cycle exercise (10-50 W) without (Control) and with added VD (200-600 ml). With added VD, VT increased via increased end-inspiratory lung volume (EILV), with no change in end-expiratory lung volume (EELV), indicating recruitment of inspiratory muscles only. With exercise, VT increased via both decreased EELV and increased EILV, indicating recruitment of both expiratory and inspiratory muscles. A significant interaction between the effects of exercise and VD on mean inspiratory flow indicated that the augmented exercise ventilatory response with added VD (i.e. STM) resulted from increased drive to the inspiratory muscles. These results reveal different patterns of respiratory muscle recruitment among experimental conditions. Hence, we conclude that fundamental differences exist in the neural control of ventilatory responses during exercise, increased VD and STM.

AB - Small increases in external dead space (VD) augment the exercise ventilatory response via a neural mechanism known as short-term modulation (STM). We hypothesized that breathing mechanics would differ during exercise, increased VD and STM. Men were studied at rest and during cycle exercise (10-50 W) without (Control) and with added VD (200-600 ml). With added VD, VT increased via increased end-inspiratory lung volume (EILV), with no change in end-expiratory lung volume (EELV), indicating recruitment of inspiratory muscles only. With exercise, VT increased via both decreased EELV and increased EILV, indicating recruitment of both expiratory and inspiratory muscles. A significant interaction between the effects of exercise and VD on mean inspiratory flow indicated that the augmented exercise ventilatory response with added VD (i.e. STM) resulted from increased drive to the inspiratory muscles. These results reveal different patterns of respiratory muscle recruitment among experimental conditions. Hence, we conclude that fundamental differences exist in the neural control of ventilatory responses during exercise, increased VD and STM.

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Breathing mechanics during exercise with added dead space reflect mechanisms of ventilatory control

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Keywords

ASJC Scopus subject areas

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