Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall info...Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall information only. However, detailed analysis is required to find effects of design parameters on the flow distribution. For this aspect, three-dimensional turbulent flow analysis was performed to assess turbulence model performance and effects of upstream pressure and branch pipe geometry. Three different turbulence models of standard k-e model, realizable k-e model and standard k-co yield similar results, indicating small effects of turbulence models on flow characteristics analysis. Geometric variations include area ratio of main and branch pipes, branch pipe diameter, and connection shape of main and branch pipes. Among these parameters, area ratio and branch diameter and shape show strong effect on flow distribution due to high friction and minor loss. Uniform flow distribution is one of common requirements in the branch piping system and this can be achieved with rather high total loss design.展开更多
目的:探索希氏束-浦肯野传导系统起搏[HPCSP,包括希氏束起搏(HBP)和左束支区域起搏(LBBAP)]联合房室结消融治疗心房颤动(房颤)合并心力衰竭(心衰)的有效性及安全性。方法:在PubMed、Cochrane图书馆、Web of Science、Embase、中国知网...目的:探索希氏束-浦肯野传导系统起搏[HPCSP,包括希氏束起搏(HBP)和左束支区域起搏(LBBAP)]联合房室结消融治疗心房颤动(房颤)合并心力衰竭(心衰)的有效性及安全性。方法:在PubMed、Cochrane图书馆、Web of Science、Embase、中国知网、万方数据库、维普网、中华医学期刊全文数据库检索关于HPCSP联合房室结消融治疗房颤合并心衰患者的研究,检索时间为各数据库建库到2024年7月31日。采用纽卡斯尔-渥太华(NOS)量表对纳入的队列研究进行质量评价,使用Cochrane偏倚风险评价方法评估随机对照研究的质量,并用RevMan 5.4、Stata 15.1软件进行Meta分析。结果:共纳入13项研究,共1071例患者。HPCSP联合房室结消融成功率为93.1%。Meta分析结果显示,在有效性方面,与基线相比,随访时患者的左心室舒张末期内径(LVEDD)[均数差(MD)=-3.11,95%CI:-4.16~-2.06,P<0.00001)]及纽约心脏协会(NYHA)心功能分级(MD=-1.36,95%CI:-1.48~-1.24,P<0.00001)明显改善,左心室射血分数(LVEF)(MD=9.86,95%CI:7.02~12.69,P<0.00001)明显提高,房室结消融后,起搏QRS波时限(QRSd)较基线延长(MD=7.83,95%CI:2.79~12.87,P=0.002);在安全性方面,HPCSP术中及随访时的起搏阈值保持稳定(MD=0.07,95%CI:-0.01~0.15,P=0.11),阻抗较围术期明显下降(MD=-78.84,95%CI:-120.21~-37.47,P=0.0002),并发症发生率为7.9%,心衰再住院率为4.5%,死亡率为5.8%。与双心室起搏相比,HPCSP明显缩短起搏QRSd(MD=-39.08,95%CI:-62.35~-15.80,P=0.001),改善随访LVEF(MD=4.38,95%CI:0.37~8.40,P=0.030),二者LVEDD变化(MD=-9.11,95%CI:-19.93~1.72,P=0.100)差异无统计学意义。随访期间,LBBAP起搏阈值低于HBP(MD=0.61,95%CI:0.23~1.00,P=0.002);LBBAP与HBP终点事件发生率差异无统计学意义(RR=1.47,95%CI:0.83~2.60,P=0.190)。结论:HPCSP联合房室结消融治疗房颤合并心衰有效、安全。HPCSP较双心室起搏可更好的促进心电同步并进一步改善患者心功能,LBBAP起搏参数优于HBP。展开更多
基金Project supported by Changwon National University in 2010
文摘Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall information only. However, detailed analysis is required to find effects of design parameters on the flow distribution. For this aspect, three-dimensional turbulent flow analysis was performed to assess turbulence model performance and effects of upstream pressure and branch pipe geometry. Three different turbulence models of standard k-e model, realizable k-e model and standard k-co yield similar results, indicating small effects of turbulence models on flow characteristics analysis. Geometric variations include area ratio of main and branch pipes, branch pipe diameter, and connection shape of main and branch pipes. Among these parameters, area ratio and branch diameter and shape show strong effect on flow distribution due to high friction and minor loss. Uniform flow distribution is one of common requirements in the branch piping system and this can be achieved with rather high total loss design.
文摘目的:探索希氏束-浦肯野传导系统起搏[HPCSP,包括希氏束起搏(HBP)和左束支区域起搏(LBBAP)]联合房室结消融治疗心房颤动(房颤)合并心力衰竭(心衰)的有效性及安全性。方法:在PubMed、Cochrane图书馆、Web of Science、Embase、中国知网、万方数据库、维普网、中华医学期刊全文数据库检索关于HPCSP联合房室结消融治疗房颤合并心衰患者的研究,检索时间为各数据库建库到2024年7月31日。采用纽卡斯尔-渥太华(NOS)量表对纳入的队列研究进行质量评价,使用Cochrane偏倚风险评价方法评估随机对照研究的质量,并用RevMan 5.4、Stata 15.1软件进行Meta分析。结果:共纳入13项研究,共1071例患者。HPCSP联合房室结消融成功率为93.1%。Meta分析结果显示,在有效性方面,与基线相比,随访时患者的左心室舒张末期内径(LVEDD)[均数差(MD)=-3.11,95%CI:-4.16~-2.06,P<0.00001)]及纽约心脏协会(NYHA)心功能分级(MD=-1.36,95%CI:-1.48~-1.24,P<0.00001)明显改善,左心室射血分数(LVEF)(MD=9.86,95%CI:7.02~12.69,P<0.00001)明显提高,房室结消融后,起搏QRS波时限(QRSd)较基线延长(MD=7.83,95%CI:2.79~12.87,P=0.002);在安全性方面,HPCSP术中及随访时的起搏阈值保持稳定(MD=0.07,95%CI:-0.01~0.15,P=0.11),阻抗较围术期明显下降(MD=-78.84,95%CI:-120.21~-37.47,P=0.0002),并发症发生率为7.9%,心衰再住院率为4.5%,死亡率为5.8%。与双心室起搏相比,HPCSP明显缩短起搏QRSd(MD=-39.08,95%CI:-62.35~-15.80,P=0.001),改善随访LVEF(MD=4.38,95%CI:0.37~8.40,P=0.030),二者LVEDD变化(MD=-9.11,95%CI:-19.93~1.72,P=0.100)差异无统计学意义。随访期间,LBBAP起搏阈值低于HBP(MD=0.61,95%CI:0.23~1.00,P=0.002);LBBAP与HBP终点事件发生率差异无统计学意义(RR=1.47,95%CI:0.83~2.60,P=0.190)。结论:HPCSP联合房室结消融治疗房颤合并心衰有效、安全。HPCSP较双心室起搏可更好的促进心电同步并进一步改善患者心功能,LBBAP起搏参数优于HBP。
