1. Patency of the upper airway is critical to respiration, Although ab
out half of patients with the sleep apnoea/hypopnoea syndrome obstruct
their upper airway at the retropalatal level, the respiratory actions
of the palatal muscles have been little studied, We have therefore te
sted the hypothesis that the nasopharyngeal dilator muscle palatogloss
us is activated during inspiration and by negative pressure, 2, Using
intramuscular wire electrodes inserted perorally, we have compared the
response of palatoglossus and genioglossus to breathing, posture chan
ge and airway negative pressure in 10 normal awake subjects before and
after topical anaesthesia, The results are expressed as a percentage
of maximal electromyogram, Data were analysed by repeated-measures ana
lysis of variance, 3, Inspiratory activity was exhibited by both genio
glossus [inspiratory, 10%+/-2% (SEM); expiratory, 6%+/-1%, P=0,001] an
d palatoglossus (inspiratory, 16%+/-5%, expiratory, 10%+/-3%, P=0,016)
, but only genioglossus exhibited increased activity on lying (supine
10%+/-2%, erect 6%+/-1% maximum, P=0.01), 4, One hundred milliseconds
after negative pressure application, activity increased in both geniog
lossus (7%+/-2% and 13%+/-3% respectively, P=0,02) and palatoglossus (
8%+/-2% and 23%+/-6% respectively, P<0,001), After lignocaine surface
anaesthesia to the nose and pharynx both genioglossus and palatoglossu
s still increased their activity in response to negative upper airway
pressure, the extent of the increase being decreased for palatoglossus
(P=0,02) but not for genioglossus. 5, Thus, palatoglossus has respira
tory activity and is activated by negative upper airway pressure.