How is the pathophysio of obstructive sleep apnea?

Pharyngeal muscles relax causing redundancy of soft tissues lining the airway. Snoring, supination may cause tongue displacement narrowing the airway. Most disordered breathing occurs during REM (rapid eye movement) cycle of sleep (all muscles are atonic except diaphragm and extraocular muscles). Could cause arousal or microarousal (repetitive arousal is associated with developing excessive daytime sleepiness and neurocognitive symtoms of OSA (oxyhemoglobin desaturated)