Muscarinic receptor subtypes in the airway

Abstract

To analyze the thermal responses of vascular tissues to the laser ablation, and to evaluate the effects of different media and probe temperatures, we investigated the effects on human cadaveric aorta using the bare-ended probe (BEP) and the metal-tip probe (MTP). In case of use of the BEP, the average laser energy for the perforation of the aortic wall was about 4J in the air, 51 in the blood and 9.6J in the saline. Especially, the average energy for the perforation in the saline needed about twice as much as in the air and blood. Perforation of the aortic wall occurred immediately after lasing. Therefore, we employed angioscope at the time of laser angioplasty to observe the intravascular lesions and to vaporize the plaques with safety. Application of angioscope could reduce the perforation rate, and angioscope was useful for observation of new recanalized by lasing. In case of use of the MTP, it was proved that the changes of tip temperature were obviously different from the size of metal tip, that is, the smaller MTP was more effective on plaques under the same laser energy. Therefore, optimal laser energy for single ablation were from 15J to 25J in 2.0mm tip and from 301 to 40J in 2.5mm tip. And, MTP/vessel diameter ratio below 0.7 should be utilized for preventing excessive thermal damage to the arterial wall. It was important that MTP to be suitable for vessel diameter should be used to laser angioplasty. On the other hand, we recently had an opportunity to use MTP that could be controlled a tip temperature and maintained it for lasing. The effects of thermal ablation were studied about this probe compared with MTP used conventional fashion. The average depth of crater between 500C and 150~C was shallow and there was not so much effective on ablation. The crater depth between 200°C and 300~C increased steadily, but the penetration and perforation of the aortic wall occurred frequently beyond 300C. Additionally, there were no significant differences in effects of thermal ablation between small tips and large tips. So it could be considered that optimal temperature for laser angioplasty ranged between 200C and 300C from the effects of ablation to the arterial wall. In conclusion, in case of use of the BEP, angioscope was available to perform laser angioplasty with safety. The smaller MTP was more effective on atherosclerotic plaques under the same laser energy. MTP/vessel diameter ratio below 0.7 should be utilized for preventing excessive thermal damage to the arterial wall. In case of use of the MTP with thermal feedback control system, optimal temperature for angioplasty ranged between 200C and 300C.