The course of lung inflation alters the central pattern of tracheobronchial cough in cat-The evidence for volume feedback during cough.

ABSTRACT

The effect of volume-related feedback and output airflow resistance on the cough motor pattern was studied in 17 pentobarbital anesthetized spontaneously-breathing cats. Lung inflation during tracheobronchial cough was ventilator controlled and triggered by the diaphragm electromyographic (EMG) signal. Altered lung inflations during cough resulted in modified cough motor drive and temporal features of coughing. When tidal volume was delivered (via the ventilator) there was a significant increase in the inspiratory and expiratory cough drive (esophageal pressures and EMG amplitudes), inspiratory phase duration (CTI), total cough cycle duration, and the duration of all cough related EMGs (Tactive). When the cough volume was delivered (via the ventilator) during the first half of inspiratory period (at CTI/2-early over inflation), there was a significant reduction in the inspiratory and expiratory EMG amplitude, peak inspiratory esophageal pressure, CTI, and the overlap between inspiratory and expiratory EMG activity. Additionally, there was significant increase in the interval between the maximum inspiratory and expiratory EMG activity and the active portion of the expiratory phase (CTE1). Control inflations coughs and control coughs with additional expiratory resistance had increased maximum expiratory esophageal pressure and prolonged CTE1, the duration of cough abdominal activity, and Tactive. There was no significant difference in control coughing and/or control coughing when sham ventilation was employed. In conclusion, modified lung inflations during coughing and/or additional expiratory airflow resistance altered the spatio-temporal features of cough motor pattern via the volume related feedback mechanism similar to that in breathing.