Editorial Potential protective mechanism of arousal in obstructive sleep apnea Naomi Deacon, Atul Malhotra Department of Medicine, Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, La Jolla, California, USA Correspondence to: Naomi Deacon, PhD. 9300 Campus Point Drive #7381, La Jolla, CA 92037-7381, USA. Email:
[email protected]. Submitted Jul 01, 2016. Accepted for publication Jul 02, 2016. doi: 10.21037/jtd.2016.07.43 View this article at: http://dx.doi.org/10.21037/jtd.2016.07.43 Obstructive sleep apnea (OSA) pathophysiology is thought increase the magnitude of post-occlusion hyperventilation to be due to the interaction of traits including airway (and consequently hypocapnia) due both to arousal associated anatomy and neuromuscular control which vary between sympathetic activation and the state dependent differences individuals. These traits include a low arousal threshold in eupneic CO2 and sensitivity. This theory is based on (wake easily from sleep), upper airway gain (how effectively the founding work by Iber and colleagues in 1986 (7) activation of upper airway dilator muscles improves who studied tracheostomized OSA patients following ventilation), loop gain (stability of the negative feedback experimental tracheal occlusion during stable NREM sleep. chemoreflex control system) and upper airway collapsibility They found that tracheal occlusion yielded arousal and (anatomical predisposition to passive airway collapse) (1). pharyngeal opening which resulted in hyperventilation and While deficits in these traits and how they interact varies hypocapnia, followed by a reduction in minute ventilation between individuals, generally mechanisms that increase and prolongation of expiratory time. The magnitude of activation of upper airway dilator muscles are considered to hypocapnia correlated with expiratory prolongation and help protect the airway from collapse.