Interaction of tracheobronchial cough and expiration reflex in the cat.

Cough and expiration reflex (ER) are two fundamental airway defense mechanisms traditionally considered distinct motor behaviors. This study examined their temporal and functional interaction using an anesthetized cat model to elucidate the integrative neural mechanisms that coordinate airway protection. Electromyographic recordings of diaphragm and abdominal muscles were obtained during mechanically induced tracheobronchial cough and laryngeal ER. The ER was evoked in three specific phases of the cough cycle: inspiratory, active expiratory phase, and passive expiratory phase. While ER provocation did not significantly alter the number of coughs, it consistently increased cough diaphragm and abdominal muscles activation and prolonged expiratory durations (total and quiescent) and total cough cycle time. The strongest facilitation of expiratory drive occurred during ER in active expiratory phase, accompanied by increased esophageal pressure amplitudes, suggesting optimized expiratory force generation. These results indicate that the ER does not compete with cough, but exerts a modulatory influence, reinforcing expiratory effort and restructuring cough timing. These findings support a model in which cough and ER operate as cooperative, hierarchically organized airway defenses that dynamically integrate to maximize clearance efficiency. Understanding these reflex interactions may provide new insights into therapeutic strategies to enhance airway protection in patients with impaired cough mechanisms.