ELECTRICALLY-ACTIVATED DILATOR MUSCLES REDUCE PHARYNGEAL RESISTANCE IN ANESTHETIZED DOGS WITH UPPER AIRWAY-OBSTRUCTION

There is current controversy as to whether electrical stimulation of u pper airway musculature can be used us a beneficial treatment modality in patients with obstructive sleep apnoea syndrome, Increased upper a irway (UAW) muscle activity decreases UAW resistance (Ruaw) in isolate d UAW of dogs. In the present study, we evaluated the effect of UAW mu scle contraction on UAW patency in anaesthetized dogs in vivo breathin g spontaneously through partially and completely obstructed UAW. Airfl ow and supraglottic pressure were measured to obtain Ruaw. Ruaw could be regulated by inhalation of a rubber balloon implanted transcutaneou sly in the pharyngeal submucosa to produce partial or complete obstruc tion. Wire electrodes were implanted bilaterally into the genioglossus (GG), geniohyoid (GH), sternothyroid (ST), and sternohyoid (SH) muscl es Tar electrical stimulation (ES), and into the alae nasi for electro myographic (EMG) recording, Three levels of electrical stimulation wer e delivered to each muscle before and during partial or complete UAW o bstruction. Genioglossus and geniohyoid stimulation both resulted in a significant reduction in Ruaw, which was most pronounced during parti al obstruction, reducing Ruaw from 54+/-11 to 14+/-3 and from 74+/-12 to 31+/-5 cmH(2)O . L(-1). s, respectively. At low voltage, stimulatio n of the genioglossus was more effective than stimulation of the genio hyoid in reducing Ruaw, Furthermore, electrical stimulation of the gen ioglossus but not of the geniohyoid released total obstruction. In con trast, electrical stimulation of the sternohyoid and sternothyroid pro duced no significant change in Ruaw. These findings demonstrate that s elective UAW dilatory muscle contraction in spontaneously breathing an aesthetized dogs reduces Ruaw in the presence of UAW obstruction and r eleases UAW occlusion, with the genioglossus being the most effective muscle. This favours further attempts to investigate the benefits of e lectrical stimulation of selected upper airway muscles in the treatmen t of obstructive sleep apnoea syndrome.