Respiratory and Circulatory Vagal Reflexes in Rabbits Exposed to High Explosive Shock Waves

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Abstract
Changes in respiration and heart rate were studied in rabbits which were exposed to high explosive shock waves in a detonation chamber after bilateral cervical vagotomy, or after pulmonary vagal denervation with the innervation of the sinoaortic region and heart left intact. The rapid shallow breathing occurring after the detonation in nondenervated animals was almost completely absent after cervical vagotomy or pulmonary vagal denervation. Sometimes an often very long period of apnea preceded the tachypnea after the detonation in the control animals. In the denervated animals, especially in the pulmonary vagally denervated ones, apnea was rare or of only very short duration. The bradycardia that can be prevented by bilateral cervical vagotomy, was not elicited by reflexes from the lungs, as the heart rate was lowered to the same extent in the lung vagus denervated as in the control animals. A cardiac standstill or severe distortions of the ECG waves during the first 1–3 seconds after the detonation were common in the nondenervated and in the lung vagus denervated animals but were rare in animals in which bilateral cervical vagotomy had been made.