Il. Mortimore et al., EFFECT OF POSTURE, ROUTE OF RESPIRATION, AND NEGATIVE-PRESSURE ON PALATAL MUSCLE-ACTIVITY IN HUMANS, Journal of applied physiology, 79(2), 1995, pp. 448-454
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.