Airways are most vulnerable to aspiration during sleep.
Esophago-upper esophageal sphincter, contractile reflex and secondary peristalsis have been proposed to protect the airway.
These responses reflexively contracting the esophago-upper esophageal sphincter and clear the esophagus of refluxate.
Dr Reza Shaker and colleagues from Wisconsin studied contractile reflex and secondary peristalsis elicitation in “awake” state.
The research team also assessed stage II, slow-wave or stage III/IV, and rapid eye movement sleep.
|Arousal and cough preempt contractile reflex and secondary peristalsis|
The team evaluated 13 healthy volunteers in the supine position.
Concurrent esophago-upper esophageal sphincter and esophageal manometry and polysomnography was used to assess the volunteers.
Threshold volume was used to trigger contractile reflex.
The team applied secondary peristalsis and recorded changes in sleep stages during injection of about 3 mL/min water into the proximal esophagus.
The injections were give after sleep stages were confirmed.
Esophago-upper esophageal sphincter pressure progressively declined with deeper stages of sleep.
Threshold volume for contractile reflex and secondary peristalsis elicitation was not significantly different between the stage II and “awake” state.
The researchers noted that threshold volume for contractile reflex and secondary peristalsis elicitation during rapid eye movement sleep were lower than during the stage II and “awake” state.
In addition, the team observed that arousal and cough preempted development of contractile reflex and secondary peristalsis during slow-wave sleep.
Dr Shaker's team concludes, “Contractile reflex/secondary peristalsis can be elicited in stage II and rapid eye movement but is preempted by arousal in slow-wave sleep.”
“Threshold volume for contractile reflex/secondary peristalsis elicitation is significantly lower in rapid eye movement, compared with the stage II and “awake” state.”
“This suggests a heightened sensitivity of these reflexes during rapid eye movement sleep.”
“Although esophago-upper esophageal sphincter pressure progressively declines with deeper stages of sleep, it can still reflexively contract during rapid eye movement sleep, despite generalized hypotonia.”