Sarkar Sandip, Hillery Claire, Seifalian Alexander, Hamilton George
Biomaterials & Tissue Engineering Centre (BTEC), Academic Division of Surgical and Interventional Sciences, Royal Free and University College Medical School, University College London, London, United Kingdom.
J Vasc Surg. 2006 Oct;44(4):846-52. doi: 10.1016/j.jvs.2006.07.023.
Because of the low patency rate of currently available vascular bypass grafts, researchers are working towards the development of alternative bypass grafts, ranging from synthetic prostheses to wholly biologic living grafts. The philosophy of measurement required by regulatory agencies such as the United States Food and Drug Administration (FDA) as well as to gain the Conformité Européene (CE) mark is to test above and beyond the limits that would be expected physiologically. The critical parameter of burst pressure is needed for Conformité Européene (CE) mark or United States Food and Drug Administration (FDA) approval before clinical trials can proceed. An accurate measurement of burst pressure in potential porous vascular bypass grafts is, therefore, of utmost importance to ensure adequate strength on implantation in animals and subsequent clinical use. A wide range of methods to measure burst pressure have been used. We tested the burst pressure of a new polyurethane-based nanocomposite vascular prosthesis by using different methods to assess whether the method used affected the results.
Water was infused at flow rates of 0.2, 50, and 100 mL/min through a syringe pump into latex sleeve-lined porous prostheses manufactured from a poly(carbonate-urea)urethane nanocomposite incorporating silsesquioxane. At the lowest infusion rate, the inflation was done with and without a nonporous inner lining sleeve. A pressure transducer was used to record the peak pressure achieved.
Using a nonporous sleeve resulted in a higher burst pressure (428 mm Hg vs 341 mm Hg) at a flow rate of 0.2 mL/min. A lower infusion rate (0.2 mL/min) produced a lower burst pressure than 50 mL/min (428 mm Hg vs 451 mm Hg). No significant difference was found in burst pressure using infusion rates of 50 mL/min and 100 mL/min.
The use of a nonporous sleeve removes the potential weakness presented by the pores themselves. A continuous high infusion rate consistently overestimates burst pressure. These methods may not reflect the physiologic state. Care needs to be taken in interpretation of methodology for burst pressure measurement, and the rate of infusion should be stated in any description of the method.
The poor patency of small-caliber vascular bypass prostheses has stimulated a large body of research into alternative graft materials. This includes synthetic and, more recently, tissue-engineered hybrid products. Acceptance for international standards requires demonstration of a rigorous mechanical testing regimen, including graft strength, which has on the whole involved burst strength measurement. However, the methods used to measure burst strength have varied with respect to apparatus used and rate of graft inflation. We show that these variables lead to markedly different results. In particular, fast infusion rates may overestimate the actual burst pressure, leading to a false sense of security.
由于目前可用的血管旁路移植物通畅率较低，研究人员正在致力于开发替代旁路移植物，范围从合成假体到完全生物活性移植物。美国食品药品监督管理局（FDA）等监管机构要求的测量理念以及获得欧洲合格认证（CE）标志，是要在生理预期极限之上进行测试。在临床试验能够进行之前，欧洲合格认证（CE）标志或美国食品药品监督管理局（FDA）批准需要爆破压力这一关键参数。因此，准确测量潜在多孔血管旁路移植物的爆破压力对于确保在动物体内植入及后续临床使用时具有足够强度至关重要。已经使用了多种测量爆破压力的方法。我们通过使用不同方法测试了一种新型聚氨酯基纳米复合血管假体的爆破压力，以评估所使用的方法是否会影响结果。
通过注射泵以0.2、50和100 mL/min的流速将水注入由包含倍半硅氧烷的聚（碳酸酯 - 脲）聚氨酯纳米复合材料制成的带有乳胶套管内衬的多孔假体中。在最低流速下，分别在有无无孔内衬套管的情况下进行充气。使用压力传感器记录达到的峰值压力。
在流速为0.2 mL/min时，使用无孔套管导致更高的爆破压力（428 mmHg对341 mmHg）。较低的流速（0.2 mL/min）产生的爆破压力低于50 mL/min（428 mmHg对451 mmHg）。在流速为50 mL/min和100 mL/min时，爆破压力未发现显著差异。
使用无孔套管消除了孔隙本身带来的潜在弱点。持续的高流速始终会高估爆破压力。这些方法可能无法反映生理状态。在解释爆破压力测量方法时需要谨慎，并且在任何方法描述中都应说明流速。
小口径血管旁路假体的通畅性差促使了对替代移植物材料的大量研究。这包括合成材料以及最近的组织工程混合产品。国际标准的认可需要证明严格的机械测试方案，包括移植物强度，总体上这涉及爆破强度测量。然而，用于测量爆破强度的方法在所用设备和移植物充气速率方面各不相同。我们表明这些变量会导致明显不同的结果。特别是，快速流速可能会高估实际爆破压力，从而产生虚假的安全感。
