Sinclair A, van Bergen J
Research and Development Section, Health and Welfare Canada, Ottawa, Ontario.
Can J Anaesth. 1992 Jan;39(1):90-4. doi: 10.1007/BF03008682.
A clinical incident involving an undetected disconnection occurred during the use of a CPRAM coaxial breathing circuit. The flow resistance of this circuit was evaluated and compared with that of a Bain circuit to determine the factors involved. A differential pressure transducer was used to monitor the pressure drop across each circuit during simulation of controlled ventilation with a fresh gas flow of 6 L.min-1. An Ohio V5 anaesthesia ventilator was adjusted to different flow rates and tidal volumes and a test lung simulated an airway resistance of 2.7 cm H2O.L-1.sec and a compliance of 0.05 L.cmH2O-1. Absolute pressure at the ventilator was also monitored when the circuit was disconnected from the test lung. The CPRAM circuit displayed a pressure drop from the ventilator to the endotracheal tube of 6.3 cm H2O at 60 L.min-1, about twice that found with the Bain. A disconnection at the tracheal connector produced an absolute pressure at the ventilator of 9.6 cm H2O with the CPRAM and 5.5 cm H2O with the Bain. Since the ventilator low pressure alarm was preset to 9.2 cm H2O, the alarm provided a warning with the Bain but not the CPRAM. The elevated flow resistance of the CPRAM circuit was attributed to a restriction in the flow area at the patient end of the circuit. Capnographs or adjustable low-pressure alarms provide more reliable monitoring for breathing circuit disconnects.
在使用心肺复苏辅助通气（CPRAM）同轴呼吸回路期间发生了一起未被检测到的回路断开的临床事件。对该回路的流动阻力进行了评估，并与贝恩回路的流动阻力进行比较，以确定其中涉及的因素。在以6 L·min⁻¹的新鲜气体流量进行控制通气模拟过程中，使用差压传感器监测每个回路两端的压降。将一台俄亥俄V5麻醉呼吸机调整到不同的流速和潮气量，并用测试肺模拟2.7 cmH₂O·L⁻¹·s的气道阻力和0.05 L·cmH₂O⁻¹的顺应性。当回路与测试肺断开连接时，还监测了呼吸机处的绝对压力。CPRAM回路在60 L·min⁻¹时从呼吸机到气管导管的压降为6.3 cmH₂O，约为贝恩回路压降的两倍。气管连接器处断开连接时，CPRAM回路在呼吸机处产生的绝对压力为9.6 cmH₂O，贝恩回路为5.5 cmH₂O。由于呼吸机低压警报预设为9.2 cmH₂O，该警报在使用贝恩回路时发出了警告，但使用CPRAM回路时未发出警告。CPRAM回路较高的流动阻力归因于回路患者端的流通面积受限。二氧化碳监测仪或可调节的低压警报可为呼吸回路断开提供更可靠的监测。
