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Costal and crural diaphragm function during panting in awake canines
1Notre-Dame Hospital, University of Montreal, Meakins-Christie Laboratories, McGill University, Quebec, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 1, 1994
Summary
During panting for thermal regulation, canine diaphragm muscles show altered activation patterns. Asynchronous shortening of costal and crural segments may improve gas mixing, similar to high-frequency ventilation.
Area of Science:
- Physiology
- Respiratory Mechanics
- Thermal Regulation
Background:
- The activation pattern of major respiratory muscles during natural panting for thermoregulation is not well understood.
- Diaphragm muscle function, specifically its costal and crural segments, plays a crucial role in respiration.
Purpose of the Study:
- To investigate the pattern of activation and function of diaphragm segmental muscles during spontaneous panting in canines.
- To compare diaphragm muscle activity at rest versus during heat-induced panting.
Main Methods:
- Measurements of diaphragm segmental length, shortening, and electromyographic (EMG) activity were taken in five chronically implanted, awake canines.
- Data were collected during spontaneous breathing at rest and during mild dry heat stress causing panting.
Main Results:
- Panting significantly increased minute ventilation and respiratory rate.
- Both costal and crural diaphragm segments showed decreased end-expiratory length and increased end-expiratory EMG during panting.
- Tidal shortening decreased in both segments, with costal shortening occurring during inspiration and crural shortening during expiration, indicating asynchronous function.
Conclusions:
- In awake, spontaneously panting canines, diaphragm costal and crural segments exhibit differential and asynchronous shortening patterns.
- This asynchronous segmental function during panting may enhance intrapulmonary gas mixing, potentially mimicking effects of high-frequency ventilation.