The Japanese journal of physiology
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To investigate the neural mechanism of the expiratory activity of the inspiratory muscles during a cough, EMG of the respiratory muscles were recorded in anesthetized and tracheostomized dogs. A laparoscope was used to minimize injury to the abdominal muscles for implantation of the electrodes into the costal diaphragm. During the expulsive phase of a cough, the diaphragm was active in 7 of 12 dogs and the external intercostal muscle was active in 3 of 6 dogs. ⋯ The onset of expiratory activity of the inspiratory muscles is significantly later than that of expiratory muscles. Continuous activity in the expiratory muscles evoked by airway occlusion, i.e., Hering-Breuer reflex, was suppressed during the inspiratory phase of a cough, but not suppressed during the expulsive phase even when the expiratory activity of the diaphragm was observed. We concluded that the expiratory activity of inspiratory muscles is controlled independently of both expiratory activity of the expiratory muscles and inspiratory activity of the inspiratory muscles.
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This study was designed to clarify the decreased arterial oxygen partial pressure (PaO2) mechanism induced by atrial natriuretic peptide (ANP) infusion. In order to examine the effects of ANP on gas exchange across the normal lungs, ANP was infused to eight anesthetized dogs, ventilated with mixed gases of oxygen and nitrogen. ⋯ ANP increased VA/Q and QS/QT. We conclude that the decrease in PaO2 caused by ANP infusion was mainly due to the increased venous admixture.