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Volume-timing relationships during cough and resistive loading in the cat
1Department of Physiological Sciences, University of Florida, Gainesville 32612, USA. bolserd@mail.vetmed.ufl.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 5, 2000
Summary
Pulmonary volume feedback does not alter cough phase durations. Coughing involves significant volume changes but maintains consistent inspiratory (CTI) and expiratory (CTE) times, suggesting distinct respiratory control mechanisms.
Area of Science:
- Respiratory Physiology
- Neuroscience
- Pulmonary Mechanics
Background:
- Coughing is a vital protective reflex involving complex respiratory muscle coordination.
- The role of pulmonary volume-related feedback in modulating cough phase durations remains incompletely understood.
- Previous research suggests distinct neural control for eupneic breathing versus forceful expiratory events like cough.
Purpose of the Study:
- To investigate the relationship between pulmonary volume changes and the durations of the inspiratory (CTI) and expiratory (CTE) phases during coughing.
- To determine if pulmonary volume-related feedback influences the timing of respiratory phases during a cough reflex.
- To compare respiratory phase durations during eupnea with those during coughing under various loading conditions.
Main Methods:
- Anesthetized cats were used to study the cough reflex induced by mechanical stimulation of the intrathoracic trachea.
- Single-breath inspiratory and expiratory resistive loads were applied during eupneic breathing.
- Measurements included inspiratory volume (VI), expiratory volume (VE), and phase durations (CTI, CTE) during both eupnea and coughing.
Main Results:
- Coughing exhibited large increases in inspiratory volume (VI) and expiratory volume (VE) without altering phase durations (CTI, CTE) compared to eupnea.
- No correlation was found between VI and CTI during coughing.
- A positive slope was observed between VE and CTE for the first or single cough, but not for all coughs, while negative slopes were noted with eupneic times under resistive loading.
Conclusions:
- Pulmonary volume-related feedback does not appear to modulate phase durations during coughing.
- The findings support the hypothesis of separate ventilatory pattern regulation during cough, distinct from eupneic breathing.
- Coughing utilizes a unique control strategy that is not primarily influenced by lung volume feedback for phase timing.
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