PALATOPHARYNGEOUS HAS RESPIRATORY ACTIVITY AND RESPONDS TO NEGATIVE-PRESSURE IN SLEEP APNOEICS

The intrinsic tongue muscle, genioglossus, and soft palatal muscles, t ensor palatini, levator palatini and palatoglossus, are known to exhib it phasic respiratory activity and to respond reflexly to negative pre ssure in man, which may be important in the maintenance of upper airwa y patency, We hypothesized that the palatopharyngeus muscle should als o have respiratory activity and increased activity in response to nega tive upper airway pressure. We have, therefore, examined the palatopha ryngeus and the antagonist muscle, levator palatini in eight awake sle ep apnoea patients, using bipolar electromyography during nose- or mou th-breathing in different postures, and with or without application of negative pressure. Overall, palatopharyngeus and levator palatini dem onstrated phasic respiratory activity, Palatopharyngeus demonstrated i ncreased activity in the supine compared to erect posture. Analysis by route of respiration showed palatopharyngeus to be more active in the supine posture when nose-breathing compared to mouth-breathing. Grade d negative pressure application caused significant increases in palato pharyngeus and levator palatini activity when applied via the mouth. N asal negative pressure application caused a nonsignificant trend to in creasing palatopharyngeus activity with increasing negative pressure c ompared to a significant increase for levator palatini. We conclude th at palatopharyngeus and levator palatini demonstrate respiratory activ ity and reflex activation in response to negative pressure. Palatophar yngens may,therefore, have a role as an upper airway dilator, The diff erential response of palatopharyngeus to oral and nasal negative press ure application may be important in the pathogenesis of sleep apnoea.