EFFECT OF BREATHING, PRESSURE AND POSTURE ON PALATOGLOSSAL AND GENIOGLOSSAL TONE

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.