| Objective: The enlarged tongue soft palate and uvula are deemed as one of the important factors of obstructive sleep apnea syndrome (OSAS). The purpose of this study is to observe the effects of microwave coagulation therapy (MCT) on skeletal muscle and the reactions of skeletal muscle to MCT, such as histological, volumetric and functional changes, and to find out the possibility of MCT to treating OSAS.Material and methods:The experiment included four sections:Part I Choosing working power and time: Tibialis anterior muscles of 12 New Zealand rabbits were exposed wholly and inserted with the antenna of 2450MHz microwave instrument. Microwave coagulation were performed with 50w 70w and l00w separately and conducted at 10s, 20s , 30s respectively. Then coagulation areas were assessed by the temperature , the scope and histological observation. Part II Histological observation of ablated muscle after MCT: Tibialis anterior muscles of 25 New Zealand rabbits were exposed and coagulated on 70w-20s at 6 points with 1cm interval. The rabbits were sacrificed at 1 hour, 24 hours, 48 hours, 1 week and 2 months after MCT. The specimens of coagulation areas were prepared and histological observation was performed.Part HI Preliminary study of apoptosis of ablated muscle: Tibialis anterior muscles of 5 New Zealand rabbits were exposed and coagulated on 70w-20s at 3 points with 1cm interval. 3mm outer tissue of coagulation areas were cutted off in 0,4,8,12,24 hours after MCT. The quantity of apoptotic cells was evaluated by Flow Cytometry(FCM).Part IV The volumetric and functional changes of ablated muscle :One side of tibialis anterior muscle of 20 New Zealand rabbits were exposed and coagulated on 70w-20s at 6 points with 1cm interval. The rabbits were sacrificed at 24 hours 48 hours 1 week and 2 months after MCT. The volumes of the ablated tibialis anterior muscles were measured and compared to the one on the other side. Electricitic physiology observations were conducted in five rabbits on the ablated muscle at 2 months after MCT before being sacrificed.Results:Part I :The temperature by 50w for 30s was 45±, 70w for 10s was48±,70w for 20s was 58±,70w for 30s was 67± and l00w for10s was 64±. But only at 70w20s, the highest temperature and lowesttemperature were between 45-70±. The diameter of coagulated areacreated at 70w20s was 0.75cm.Part II :There was obvious verge between coagulated and normal tissues.The ablated area included tissue fixation and coagulation necrosis. Inhigh-powered magnification, four zones were existed just as theapplication zone, the central zone, the transition zone and the referencezone. Demarcation zone appeared 24h after exposure, fibrosisencapsulation occurred after 7 days, and replacement with a fine cicatrixafter 2 months.Part IHiApoptosis appeared around MCT site. The highest percentage ofapoptotic cells was 45.94%, appeared 8 hours after MCT.Part IV: The volume of ablated muscle increased slightly at 24 hours,and stilled increased nearly 20% at 48 hours after MCT. It decreased 1week and 23.6% volumetric loss in 2 months. There was no apparentdifference in electrophysiologic observation.Conclusions:The results showed that MCT at 70w-20s created temperature between 45± -70± and was good for soft tissue ablation. Apoptotic cells will be induced around the coagulation areas. Coagulation tissue will be replaced with a fine cicatrix gradually. The volumetric reduction of the skeleton muscle will be 23.6% and muscle function can be preserved. The prospect of MCT for OS AS is worth studying.
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