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Respiratory changes in abdominal configuration in supine dogs
M Estenne1, G Farkas, A De Troyer
1Respiratory Research Unit, Erasme University Hospital, Brussels School of Medicine, Belgium.
Respiration Physiology
|May 1, 1990
Summary
In supine dogs, expiratory contraction of the transversus abdominis muscle primarily reduces abdominal width, increasing gastric pressure and causing outward abdominal wall motion. This complex interplay shows the abdomen moves with multiple degrees of freedom during breathing.
Area of Science:
- Physiology
- Respiratory Mechanics
- Abdominal Muscle Function
Background:
- Understanding respiratory muscle function is crucial for respiratory mechanics.
- Abdominal muscle activity during breathing has been previously investigated.
- The specific role of the transversus abdominis in supine dogs requires further clarification.
Purpose of the Study:
- To investigate the electromyographic (EMG) activity of abdominal muscles during respiration in supine dogs.
- To correlate abdominal muscle activity with changes in abdominal dimensions (anteroposterior and transverse).
- To elucidate the role of the transversus abdominis in expiratory mechanics.
Main Methods:
- Recorded EMG activity of transversus abdominis, external oblique, and rectus abdominis in eight supine, anesthetized dogs.
- Measured respiratory changes in anteroposterior (AP) and transverse (T) abdominal diameters.
- Manipulated transversus abdominis activation using anesthesia and hyperoxic hypercapnia; denervated triangularis sterni to assess its role.
Main Results:
- Phasic expiratory EMG activity was observed in the transversus abdominis (5/8 dogs) and external oblique (2/8 dogs), but not the rectus abdominis.
- Transversus abdominis activation correlated with decreased abdominal T diameter, increased gastric pressure, and a tendency for increased AP diameter.
- Abdominal configuration changes were independent of triangularis sterni denervation but sensitive to anesthesia levels and hypercapnia.
Conclusions:
- Expiratory transversus abdominis contraction primarily reduces abdominal transverse diameter, increasing intra-abdominal pressure.
- Increased intra-abdominal pressure leads to outward ventral abdominal wall motion, explaining rectus abdominis shortening.
- Supine dogs exhibit multi-degree-of-freedom abdominal motion during resting breathing.