BackgroundOxygenators, as used in cardiopulmonary bypass (CPB) circuits, are components with good air removal properties. However, under some conditions the semipermeable characteristics of hollow fibers allow air to accidentally enter the blood side of the CPB circuit. This may occur when a fluid in motion is stopped suddenly by which the rapid change in momentum may cause a relative negative pressure drop, the so-called hammer effect. The hammer effect is not yet described in literature related to CPB. The aim of this in vitro study was to reproduce the hammer effect.MethodsThe in vitro setup consisted of a CPB circuit with a fully occluded roller pump and one of four test oxygenators. The hammer test was performed by a sudden pump stop. The pressure wave was measured and after the test the residual air present in the oxygenator was forced into the arterial line and measured with a bubble detector.ResultsWe showed that a sudden pump stop could lead to the hammer effect, represented as a relative negative pressure drop in the arterial line. This hammer effect resulted in air release through the semipermeable fibers as we showed in two of the four tested brands of oxygenators.ConclusionsWe conclude that the hammer effect may occur before connection of the CPB system to the patient, and this may result in air release into the arterial blood side of the oxygenator. The hammer effect can be caused by clamping of the tubing in combination with a centrifugal pump, or by suddenly stopping the roller pump. With this study we would like to raise awareness of the hammer effect.

中文翻译：

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泵突然停止可能会导致氧合器中空气释放，“锤子效应”：体外评估

背景 心肺旁路 (CPB) 回路中使用的制氧器是具有良好排气性能的组件。然而，在某些情况下，中空纤维的半渗透特性会使空气意外进入 CPB 回路的血液侧。当运动中的流体突然停止时，可能会发生这种情况，动量的快速变化可能会导致相对负压下降，即所谓的锤子效应。与 CPB 相关的文献中尚未描述锤击效应。这项体外研究的目的是重现锤击效应。方法体外设置由带有完全闭塞滚子泵的 CPB 回路和四个测试氧合器之一组成。锤击测试是通过泵突然停止来进行的。测量压力波，测试后将氧合器中存在的残余空气强制进入动脉管路，并用气泡检测器进行测量。结果我们表明，泵突然停止可能会导致锤击效应，表现为相对负压降在动脉线上。这种锤击效应导致空气通过半透性纤维释放，正如我们在四个测试品牌的氧合器中的两个中所展示的那样。结论我们的结论是，锤击效应可能在 CPB 系统连接到患者之前发生，这可能导致空气释放到患者体内氧合器的动脉血侧。锤击效应可能是由与离心泵结合的管道夹紧或突然停止滚子泵引起的。通过这项研究，我们希望提高人们对锤子效应的认识。