The Experimental Study Of Implanting Nitinol Stents To Treat Obstructive Sleep Apnea-hypopnea Syndrome

Objectives To establish a natural model of obstructive sleep apnea-hypopnea syndrome (OSAHS) by feeding Luchuan pigs, and to investigate the therapeutic effect of implanting nitinol stents on Luchuan pigs with OSAHS. Methods (1) After sleep with injection of valium, 10 adult female Luchuan pigs were undergone simple polysomnography, including nasal airflow, snoring, chest and abdominal movements, and oxygen saturation(SaO2). According to the results, pigs were divided into OSAHS group and control group. (2) All pigs were examined with MRI to investigate the upper airway differences between OSAHS and control pigs and locate the sites of obstruction in OSAHS pigs.(3) The shape and size of nitinol stents were determined by the upper airway characteristics of OSAHS pigs. Under fluoroscopical guidance, stents were implanted into the upper airway by using flexible bronchoscopy . Simple polysomnography and flexible bronchoscopic examination were performed to evaluate the therapeutic effect after one and six months operation, respectively. Results (1) Five pigs (50%) were diagnosed as OSAHS. Among them, two pigs were mild OSAHS , two moderate and one severe OSAHS. The apnea-hypopnea index (AHI), time of SaO2 less than 90% to total sleep time (TS90%) andsnoring index (SI) of OSAHS group were significantly higher than those of control group. The mean SaO2 (SaO2 mean )and minimal SaO2(SaO2 min) were much lower than those of control group. (2) The least cross-sectional area and corresponding anteroposterior diameter(AP), transverse diameter (T) of retropalatal(RP) region in OSAHS group were much less than those of control group.But AP/T ratio of RP region in OSAHS group were much higher than that of controls. In the retroglossal (RG) region, the least area and corresponding transverse diameter of OSAHS group were less than those of controls, but anteroposterior diameter and AP/T ratio of two groups showed no significant differences. When sleep apnea happened, MRI showed that the RP region collapsed in all OSAHS pigs .(3) After implantation of nitinol stents, four OSAHS pigs snored much less than before. Because another stent was slightly longer and deeper than what was necessary,it was replaced by a new one after 20 days operation. After one month implantation, AHI and TS 90% in all OSAHS pigs decreased significantly, SaO2 mean and SaO2 min were improved significantly. These results described above were stable after 6 months operation. The postoperative complications were slight. Conclusions (1) Some Luchuan pigs had significantly abnormal upper airway anatomy of pharyngeal narrowness which caused sleep apnea, hypopnea and recurrent episodic hypoxia. They would be a kind of perfectly natural model of OSAHS. (2) In OSAHS pigs with narrowness of retropalatalregion, the treatment of implanting nitinol stents was significantly effective. The procedure of implantation was safe and simple. So it is possible to be wideiy applied to clinical practice.