An investigation to augment cough response in anesthetized dogs

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Firstly we tested the hypothesis that the intrathoracic bronchi constrict during cough. In the tracheostomized dogs, diameter of the fifth-generation bronchus was continuously measured with a balloon-tipped catheter. The bronchus constricted in explosive phase of cough in all the dogs. Then the dogs were vagotomized and the cough was simulated by sequential application of positive and negative airway pressures. The peak explosive flow significantly decreased and airway pressure in the segmental bronchus became smaller when the bronchi were constricted. These findings suggested that bronchial constriction augments cough by moving choke point to proximal airway.In the second study we investigated method to augment cough. Coughing was elicited with mechanical stimulation of tracheal bifurcation using a wire inserted through low neck. When mechanical stimulation of vocal chord was applied concurrently with tracheal stimulation, the parameters of cough strength (mean pleural pressure, mean expiratory flow) increased. The parameters of cough strength also increased when cough was elicited after intravenous aminophylline. We speculated that in the anesthetized dog neural inputs from the upper airway augment cough response.