Manthous C A, Schmidt G A
Department of Medicine, University of Chicago, IL.
Crit Care Med. 1994 Nov;22(11):1792-5.
Heat and moisture exchangers (or "nose" humidifiers) are commonly used to aid in the humidification of inspired gases of mechanically ventilated patients. These devices add resistance to the ventilator circuit that has heretofore not been quantified in critically ill patients. Accordingly, we determined the resistive pressures associated with new and old (but < 24 hrs in the circuit) humidifiers in 23 critically ill, mechanically ventilated patients.
Prospective study.
Adult medical and surgical intensive care units at a university center.
Twenty-three critically ill, mechanically ventilated patients using a condenser humidifier between the wye and the endotracheal tube.
Peak and plateau airway pressures were determined with the humidifier in place. These measurements were repeated without the humidifier, then after insertion of a fresh humidifier into the circuit. In five patients, measurements were repeated after humidifiers had remained in place for a full 24 hrs.
The new humidifiers increased the resistive pressure of the ventilator circuit by 4.8 +/- 2.6 cm H2O compared with no humidifier (p < .01) and had a mean resistance of 4.2 +/- 1.5 cm H2O/L/sec. Old humidifiers increased resistive pressure by 6.3 +/- 3.6 cm H2O compared with no humidifier (p < .01) and had a mean resistance of 5.1 +/- 1.8 cm H2O/L/sec. The resistive pressure doubled from 3.4 +/- 1.2 to 7.0 +/- 1.8 cm H2O (p < .01) in five patients in whom the humidifiers were left in the ventilator circuit for a full 24 hrs.
The humidifier adds a significant resistance to the ventilator circuit which may lead to incorrect assessment of respiratory system mechanics, to inappropriate therapy (e.g., bronchodilators), or to difficulty in weaning from mechanical ventilation.
热湿交换器（或“鼻”加湿器）常用于辅助机械通气患者吸入气体的湿化。这些装置会给呼吸机回路增加阻力，而此前在重症患者中尚未对该阻力进行量化。因此，我们测定了23例重症机械通气患者使用新的和使用时间较短（<24小时）的加湿器时相关的阻力压力。
前瞻性研究。
大学中心的成人内科和外科重症监护病房。
23例使用冷凝器加湿器且位于Y形管和气管内导管之间的重症机械通气患者。
在安装加湿器的情况下测定气道峰压和平台压。在未安装加湿器时重复这些测量，然后在回路中插入新的加湿器后再次重复测量。在5例患者中，加湿器在回路中放置满24小时后再次重复测量。
与未使用加湿器相比，新的加湿器使呼吸机回路的阻力压力增加了4.8±2.6 cmH₂O（p<0.01），平均阻力为4.2±1.5 cmH₂O/L/秒。与未使用加湿器相比，使用时间较短的加湿器使阻力压力增加了6.3±3.6 cmH₂O（p<0.01），平均阻力为5.1±1.8 cmH₂O/L/秒。在5例加湿器在呼吸机回路中放置满24小时的患者中，阻力压力从3.4±1.2 cmH₂O翻倍至7.0±1.8 cmH₂O（p<0.01）。
加湿器会给呼吸机回路增加显著阻力，这可能导致对呼吸系统力学的评估错误、治疗不当（如使用支气管扩张剂）或机械通气撤机困难。
