Accuracy of dilution techniques for access flow measurement during hemodialysis
Accuracy of dilution techniques for access flow measurement during hemodialysis
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DOI：
10.1053/ajkd.1998.v31.pm9506688
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发表时间：
1998-03-01
影响因子：
13.2
通讯作者：
Dobson, A
中科院分区：
文献类型：
--
作者：
Krivitski, NM;MacGibbon, D;Dobson, A
目前，通过制造人工再循环，将透析线反转，并使用稀释方法来检测超声速度、电阻抗、光学或热变化，广泛测量通路流量。本研究确定并量化了影响通路流量测量准确性的因素，并提出了减少这些误差的方法。通道流量测量误差的两个主要来源，首先是由指标通过心肺系统再循环（心肺再循环，CPR）的第二次传递引起的，其次是由静脉注射压力引起的静脉线血流量（Qb）和血管通道流量的变化引起的。这些误差从理论上考虑，通过直接测量羊模型中的通道流量，并通过分析临床数据。在通路流量测量中，可以考虑静脉引入指示剂的两种极端情况：缓慢输注，既不干扰静脉线流量，也不干扰通路流量，但增加了指示剂经心肺系统再循环第二次通过的误差；快速注射，使指示剂信号第二次通过的分离变得容易，但使静脉流量和通路流量发生变化。如果没有消除心肺复苏术，则增加到第一次通过指示器的面积的范围可达40%。良好的时间分辨率可以将指标第一次和第二次通过所产生的区域分开。在绵羊实验中，向靠近血管通路的静脉口注射5或10 mt，可使Qb改变20%至40%。动物实验和常规临床透析期间收集的原始数据分析表明，在大多数管道品牌（Baxter, Belco, Gambro, hospital， Medlsystem和National Medical Care）浓度曲线发生变化的关键时刻，将注射部位移至离患者足够远的地方，在静脉泡陷阱之前或进入静脉泡陷阱，将Qb的增加减少到仅约5%。由于Cobe管中静脉泡室的体积较小（Cobe, Centrysystem 3），该品牌的ab增加了约20%。在绵羊实验中，将注射感染部位移至泡器之前也消除了通道流量变化的影响。通道流量测量中20%或更多的额外误差来自使用从泵设置中获取的流量读数，而不是测量的流量。实际流量与泵设置之间的差异可归因于针头尺寸、血管通道条件或泵校准。结果表明，使用双传感器系统可以最大限度地减少问题，该系统可以保持通道再循环与CPR分离所需的精确定时；通过对透析器血流量的精确测量；通过将注射部位移动到静脉泡诱捕器之前，离患者足够远，并纠正与稀释曲线同时存在的静脉线流动的任何剩余偏差。(C) 1998年由国家肾脏基金会，Inc。
Access flow is now widely measured by creating artificial recirculation with the dialysis lines reversed and using dilution methods that sense either ultrasound velocity, electrical impedance, optical, or thermal changes, This study identifies and quantifies factors that influence the accuracy of access flow measurements and recommends ways to reduce these errors. Two major sources of access flow measurement error are identified, arising firstly from the second pass of the indicator by recirculation through the cardiopulmonary system (cardiopulmonary recirculation, CPR), and secondly from changes in venous line blood flow (Qb) and vascular access flow induced by the pressure of venous bolus injections. These errors are considered from theory, by direct measurement of access flow in a sheep model, and by analysis of clinical data. Two extremes for the venous introduction of indicator can be considered in access flow measurements, a slow infusion, which perturbs neither the venous line flow nor access flow but increases the error attributable to the second pass of the indicator by recirculation through cardiopulmonary system, or rapid injection, which eases separation of the second pass of the indicator signal but generates changes in the venous flow and access flow. If CPR is not eliminated, the area added to that of the first pass of indicator ranges up to 40%. Good time resolution could permit the separation of the areas generated by the first and second passage of the indicator. In sheep experiments, injections of 5 or 10 mt into a venous port close to the vascular access caused Qb to change by 20% to 40%. Both the animal experiments and analysis of raw data collected during routine clinical dialysis showed that moving the injection site sufficiently far from the patient, before or into the venous bubble trap, reduced the increase in Qb to only approximately 5% during the critical time when the concentration curve is changing for most tubing brands (Baxter, Belco, Gambro, Hospal, Medlsystem, and National Medical Care). Because of the smaller volume of the venous bubble chamber in Cobe tubing (Cobe, Centrysystem 3), this brand showed approximately a 20% increase in ab. Moving the site of bolus infections to before the bubble trap in the sheep experiments also eliminated the influence of changes in access flow. An additional error in access flow measurement of 20% or more arises from the use of flow reading taken from pump setting rather than a measured flow. The discrepancy between the real flow and pump setting is attributable to needle size, vascular access conditions, or pump calibration. The results show that problems can be minimized by using a dual sensor system that retains the precise timing necessary for separation of access recirculation from CPR; by accurate measurement of dialyzer blood flow; by moving the site of injection to before the venous bubble trap, sufficiently far from the patient, and correcting for any remaining deviations in flow in the venous line concurrent with the dilution curve. (C) 1998 by the National Kidney Foundation, Inc.