Electrophysiologic latency to the external obliques of the laryngeal cough expiration reflex in humans

Objective: The purpose of this study was to trigger the laryngeal cough expiration reflex using inhaled tartaric acid aerosol and to record the latency between the time of initiation of the laryngeal cough expiration reflex component of the laryngeal cough reflex and the onset of electromyographically recorded responses in the external abdominal oblique in humans. Design: Five male subjects were tested in the seated position, and four latencies were recorded for each subject. The latencies were recorded from laryngeal stimulation to an electromyogram in the muscle belly of the left external abdominal oblique. The time line was activated by a microswitch attached to a breath-activated nebulizer. Data were analyzed using SPSS for mean latency and standard deviation. Results: The mean (standard deviation) latency to the external abdominal oblique muscle was 17.6 +/- 10.6 msec. No adverse events to inhalation were reported. Conclusions: In humans, nebulized tartaric acid stimulates primarily rapid adapting receptors in the supraglottic larynx rather than C-fiber receptors. This receptor location in humans evolved neurologically to protect the airway during speech and swallowing, making the laryngeal cough expiration reflex an inseparable component of the laryngeal cough reflex, thus making it clinically significant when assessing airway protection.