Volitional control of reflex cough

Hegland KW, Bolser DC, Davenport PW. Volitional control of reflex cough. J Appl Physiol 113: 39-46, 2012. First published April 5, 2012; doi:10.1152/japplphysiol.01299.2011.-Multiple studies suggest a role for the cerebral cortex in the generation of reflex cough in awake humans. Reflex cough is preceded by detection of an urge to cough; strokes specifically within the cerebral cortex can affect parameters of reflex cough, and reflex cough can be voluntarily suppressed. However, it is not known to what extent healthy, awake humans can volitionally modulate the cough reflex, aside from suppression. The aims of this study were to determine whether conscious humans can volitionally modify their reflexive cough and, if so, to determine what parameters of the cough waveform and corresponding muscle activity can be modified. Twenty adults (18-40 yr, 4 men) volunteered for study participation and gave verbal and written informed consent. Participants were seated and outfitted with a face-ask and pneumotacograph, and two surface EMG electrodes were positioned over expiratory muscles. Capsaicin (200 mu M) was delivered via dosimeter and one-way (inspiratory) valve attached to a side port between the facemask and pneumotachograph. Cough airflow and surface EMG activity were recorded across tasks including 1) baseline, 2) small cough (cough smaller or softer than normal), 3) long cough (cough longer or louder than normal), and 4) not cough (alternative behavior). All participants coughed in response to 200 mu M capsaicin and were able to modify the cough. Variables exhibiting changes include those related to the peak airflow during the expiratory phase. Results demonstrate that it is possible to volitionally modify cough motor output characteristics.