The Design Of NiTi Memory Alloy For Bronchial Occlude And Its Application For Bronchial Occlusion In Experimental Healthy Dogs

Objective The purpose of this experiment is to design a kind of self-expandable and implantable occlusive device for application in interventional bronchial occlusion.It is also to verify the validity,safety and security of the device in animal experiment through its implantating into the dog's bronchus. Material and Method: The First part: The Designs of occlude and its implantating device. (1)Design of the occlusive device:Some quantity of secondary-smelt NiTi alloy was taken after forging and thermal rolling,it was drawn into filament(diameter 0.20mm), then weaved into net like mesh (diameter 1mm),then reprocessed,fixed with a screw and membrane and finally moulded into several variform occlude. (2) Design of the implantating device: Some quantity of 316L stainless steel, perform forging and thermal rolling, drawing filament(diameter 0.4mm and 0.23mm respectively), enlacing and jointing, after that assembling the products into guiding filum, a technical examination was carried out to appraise their physical capability.The second part:Experimental study:Animal experiments were used to screen and observe its validity and security: Under general anesthesia , tracheotomy was performed on the healthy dog,the bronchus was localized using X-ray fluoroscopy fibrobronchoscope and with the help of the implanting equipment, several NiTi alloy occludes were implanted into the target bronchus of the dogs through the biopsy channel in the fibrobronchoscope. Result: The occlude and the implantating device were examined by the Chinese Physic and Biological Products Inspection Bureau .The conclusion was that the products are both met the standard of the Q/SCGL1-2000. Forty-eight occludes were successfully implanted into the bronchi of all the dogs. During the two months observaton period ten of occludes slipped off within one week. At the end of the first three weeks acute inflammation was observed at the implantation sites. After five weeks it developed into chronic inflammation. Fresh mucosa could be observed growing through the net which was totally covered five weeks later. In the first three weeks there were no significant changes in the lung parenchyma of the occluded bronchus. Three weeks later atrophy could be observed there. Five weeks and two months later atrophy couldbe observed more evident. Compensatory emphysema was observed in the neighbouring lung parenchyma. Rupture and necrosis of the occluded bronchial wall were not found. Obstructive pneumonia didn't occur. There were no extrapulmonary pathological changes in the liver, spleen, kidney, heart and brain tissue were observed. Conclusion: Self-expandable occludes possess good histocompatibility with no toxic reaction to the host body. The occoluded bronchi give rise to post-occlusion lung parenchyma atrophy. Self-expanding NiTi shape memory alloy bronchial occlude are safe and effective. In view of its applicability in dogs, possible extension of its use in humans will need to be studied.