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Respiratory muscle response to flail chest
M Cappello1, C Yuehua, A De Troyer
1Laboratory of Cardiorespiratory Physiology, Brussels School of Medicine, Belgium.
Summary
Flail chest in dogs increases external intercostal muscle activity due to heightened muscle spindle activation. Preventing rib displacement during inspiration did not alter this increased muscle activity.
Area of Science:
- Physiology
- Respiratory Mechanics
- Surgical Research
Background:
- Flail chest causes paradoxical rib motion and increased inspiratory muscle activity.
- Previous work suggested increased spindle afferent activity contributes to this.
- The precise mechanism requires further investigation.
Purpose of the Study:
- To test the hypothesis that increased external intercostal muscle activity in flail chest is due to heightened muscle spindle afferent activity.
- To investigate the role of rib displacement in this response.
Main Methods:
- Surgically induced flail chest in 29 supine anesthetized dogs.
- Recorded muscle activity in various respiratory muscles.
- Manipulated rib connectivity to alter mechanical constraints.
Main Results:
- Flail chest increased inspiratory activity in external intercostals and levator costae in the affected segment.
- Muscle lengthening, not shortening, occurred during inspiration in the flail segment.
- Preventing rib lengthening abolished the increased muscle activity.
Conclusions:
- Increased external intercostal muscle activity in flail chest is primarily driven by muscle spindle activation.
- Mechanical factors related to rib displacement are crucial for this response.