Bourgain J L, Desruennes E, Cosset M F, Mamelle G, Belaiche S, Truffa-Bachi J
Service d'Anesthésie, Institut Gustave-Roussy, Villejuif, France.
Br J Anaesth. 1990 Dec;65(6):737-43. doi: 10.1093/bja/65.6.737.
An anaesthetic technique using high frequency jet ventilation has been proposed for direct laryngoscopy, but this may expose the patients to the risk of barotrauma. In order to assess this risk, we have measured end-expiratory airway pressure (EEP) through the injector using two three-way solenoid valves mounted in series. At the end of insufflation the first valve was switched off and the apparatus deadspace connected to atmosphere through a large exit port during an adjustable time (decompression time). Then the second valve was switched off and the injection line connected to a transducer, allowing measurement of EEP through the injector. The accuracy of this measurement was tested against airway pressure measured directly in the trachea (Pt) in a lung model. Provided that the decompression time was long enough (70 ms) and the apparatus deadspace was small (6 ml), the difference between EEP and Pt was less than 1 cm H2O for frequencies up to 5 Hz. A clinical evaluation was performed in 64 patients under general anaesthesia before laryngoscopy. EEP correlated with end-expiratory pulmonary volume above apnoeic FRC inferred from abdominal and thoracic displacements. At jet frequencies up to 5 Hz, the correlations between these two variables were satisfactory (r greater than 0.88), suggesting that EEP is a good indicator of pulmonary overdistension.
有人提出在直接喉镜检查中使用高频喷射通气麻醉技术，但这可能使患者面临气压伤风险。为评估此风险，我们通过串联安装的两个三通电磁阀，利用注射器测量呼气末气道压力（EEP）。在充气结束时，关闭第一个阀门，在可调时间（减压时间）内，装置死腔通过一个大出口与大气相通。然后关闭第二个阀门，将注射管路连接到传感器，从而能够通过注射器测量EEP。在肺模型中，将该测量的准确性与直接在气管中测量的气道压力（Pt）进行了对比测试。如果减压时间足够长（70毫秒）且装置死腔较小（6毫升），则在频率高达5赫兹时，EEP与Pt之间的差异小于1厘米水柱。对64例全身麻醉下进行喉镜检查前的患者进行了临床评估。EEP与根据腹部和胸部位移推断的呼吸暂停功能残气量以上的呼气末肺容积相关。在高达5赫兹的喷射频率下，这两个变量之间的相关性良好（r大于0.88），表明EEP是肺过度扩张的良好指标。
