The tone of respiratory muscles in acute changes of circulation induced by acetylcholine.

The role of respiratory muscles in acute changes of circulation and ventilation due to acetylcholine in anaesthetized spontaneously breathing rabbits was investigated. Significant increase of end-expiratory thoracic circumference and insignificant increase of abdominal one was found and was taken as a measure of changed respiratory muscles tone. The authors emphasize the important role of the respiratory muscles in the regulation of the thoracic and the abdominal volume. The increased lung volume is due to the action of the respiratory muscles of thorax and diaphragm. The abdominal muscles and diaphragm may regulate the abdominal volume and play important part in the redistribution of the blood.