Fig. 6. Polygraph record in one subject at a stable plane of general anesthesia (A –D ) and during recovery (E and F ), showing raw and moving-time-averaged (MTA) genioglossus electromyogram (EMGgg) responses while breathing at the maintenance pressure (A ), during a decrease in mask pressure (Pm) sufficient to cause flow-limitation (B ) or upper airway collapse (C ), during application of a 30-cm H2O square wave of negative pressure (D ), during quiet breathing on arousal from anesthesia (E ), and when asked to voluntarily protrude the tongue (F ).