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Diaphragm length adjustments with body position changes in the awake dog
J W Fitting1, P A Easton, R Arnoux
1Hôpital Notre-Dame, Université de Montréal, Quebec, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1989
Summary
Diaphragm function in awake dogs is maintained across different postures. Compensatory abdominal muscle contraction, not increased diaphragm electrical activity, supports breathing when diaphragm length changes.
Area of Science:
- Physiology
- Respiratory Mechanics
- Comparative Anatomy
Background:
- The diaphragm is the primary muscle of inspiration.
- Changes in posture can alter diaphragmatic length and function.
- Understanding compensatory mechanisms is crucial for respiratory health.
Purpose of the Study:
- To investigate diaphragmatic length and shortening in awake dogs across different postures.
- To determine the role of diaphragmatic electrical activity and abdominal muscle contraction in maintaining tidal volume.
Main Methods:
- Sonomicrometry was employed to measure diaphragmatic segments in chronically instrumented dogs.
- Measurements were taken in right lateral decubitus, standing, and sitting positions.
- Diaphragmatic electromyogram (EMG) and abdominal pressure were recorded.
Main Results:
- End-expiratory diaphragm length decreased significantly in the sitting posture compared to decubitus.
- Diaphragmatic tidal shortening remained consistent across all tested postures.
- Abdominal pressure dynamics suggested phasic expiratory abdominal muscle contraction in standing and sitting postures.
Conclusions:
- Diaphragmatic tidal shortening is preserved during resting breathing in various postures in awake dogs.
- Phasic expiratory contraction of abdominal muscles appears to be the primary compensatory mechanism for altered diaphragmatic operational length.
- Increased diaphragmatic EMG activity is not the main compensatory strategy for postural changes affecting diaphragm length.