EFFECT OF POSTURE, ROUTE OF RESPIRATION, AND NEGATIVE-PRESSURE ON PALATAL MUSCLE-ACTIVITY IN HUMANS

Sleep apnea is worse in the supine posture and is associated with retr opalatal airway narrowing or occlusion. We have, therefore, examined t he effects of posture, negative pressure, and route of respiration on palatal muscle activity in 13 nonsnoring awake male subjects by using electromyography. Electromyographic activity of the levator palatini a nd palatoglossus was expressed as a percentage of maximum activity. Bo th the levator palatini (P = 0.002) and palatoglossus (P = 0.002) exhi bited phasic inspiratory activity. Overall, posture did not affect the levator palatini (F = 1.58; P = 0.23) or palatoglossus (F = 0.98; P = 0.34) activity, but, analysis by route of respiration showed the pala toglossus to be more active when the subjects were nose breathing supi ne (F = 6.64; P < 0.02). Levator palatini activity was lower when nose breathing was compared with mouth breathing in both the erect and sup ine postures (F = 6.67; P < 0.02). Nose breathing with the mouth held open caused an increase in palatoglossal activity (P = 0.04). Negative -pressure application (0 to -12.5 cmH(2)O) caused significant increase s in levator palatini (P < 0.001) and palatoglossus (P < 0.001) activi ty, 100 ms after pressure stimulus, irrespective of route. However, th e palatoglossus required significantly greater negative pressures to c ause activation when applied via the nose compared with the mouth (P < 0.05). These observations indicate that the levator palatini and pala tglossus have respiratory activity and are reflexly activated by negat ive pressure.