Morita S, Saito H, Hayashi T, Goto T, Niimi Y
Department of Anesthesia, Teikyo University Ichihara Hospital.
Masui. 1995 Feb;44(2):210-5.
Since induction of anesthesia using a closed-circuit technique is difficult with most modern anesthesia machines, it is a common clinical practice to convert semiclosed, high-flow anesthesia (SCA) to closed circuit anesthesia (CCA) during the maintenance phase by decreasing the fresh gas flow. The purpose of the current studies was to determine if such changes in the fresh gas flow influence parameters of ventilatory dynamics. The tidal volume, airway pressure, and a ratio of expiratory volume in one second to a tidal volume (EV1.0/VT) were measured in six patients and in a lung simulator during CCA with a fresh gas flow of 200 ml.min-1 and SCA with a flow of 6 l.min-1. The ventilator settings were constant throughout the experiments. Dynamic compliance was calculated as (measured VT)/(peak airway pressure-positive end-expiratory pressure). Both in patients and in a lung simulator, dynamic compliance and EV1.0/VT were higher during CCA as compared to SCA while the tidal volume and airway pressure were lower. It was also suggested that these differences were secondary to differences in the fresh gas flow and not to the circuit situation (closed vs. semiclosed) per se. The results emphasize that the fresh gas flow should be taken into consideration in interpreting the data of ventilatory dynamics during anesthesia. This is especially so during CCA because CCA employs a minimum fresh gas flow.
由于使用闭路技术诱导麻醉对于大多数现代麻醉机来说都很困难,因此在维持阶段通过降低新鲜气体流量将半紧闭高流量麻醉(SCA)转换为紧闭循环麻醉(CCA)是一种常见的临床做法。当前研究的目的是确定新鲜气体流量的这种变化是否会影响通气动力学参数。在6名患者和一个肺模拟器中,分别在新鲜气体流量为200 ml·min⁻¹的CCA期间以及流量为6 l·min⁻¹的SCA期间,测量潮气量、气道压力以及一秒钟呼出量与潮气量的比值(EV1.0/VT)。在整个实验过程中,呼吸机设置保持不变。动态顺应性计算为(测量的VT)/(气道峰压 - 呼气末正压)。在患者和肺模拟器中,与SCA相比,CCA期间的动态顺应性和EV1.0/VT更高,而潮气量和气道压力更低。还表明这些差异是新鲜气体流量差异的继发结果,而非回路情况(紧闭与半紧闭)本身所致。结果强调,在解释麻醉期间通气动力学数据时应考虑新鲜气体流量。在CCA期间尤其如此,因为CCA采用的是最低新鲜气体流量。