不同呼气末正压的单肺通气患者通气血流失衡的生理学评价和呼吸力学机制

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Physiologic Evaluation of Ventilation Perfusion Mismatch and Respiratory Mechanics at Different Positive End-expiratory Pressure in Patients Undergoing Protective One-lung Ventilation

背景

由于肺分流和肺不张的发生，单肺通气过程中动脉氧合常常受损。使用低潮气量（VT）（5ml/kg理想体重）的肺保护性通气方法会加剧肺不张。本研究旨在确定单肺通气时呼气末正压和小潮气量通气时的联合生理效应。

方  法

收集41例胸外科全麻病人的资料进行分析。在双肺通气和单肺通气PEEP为0cm H₂O时，单肺通气PEEP为5或10cm H₂O时测量肺内分流，V/Q和呼吸力学参数。测量吸入氧浓度、呼吸气体浓度和动脉血气计算肺内分流，V/Q。随机选择PEEP的水平，并在测量前维持15分钟。

结  果

在单肺通气过程中，PEEP从0 cm H2O增加到5 cm H₂O和10 cm H₂O，肺内分流分别下降了5%（0-11）和11%（5-16）（p＜0.001）。PaO2/FiO₂比值只在呼气末正压10 cm H₂O时增加（P＜0.001）。在PEEP为10cm H₂O时，驱动压力从16±3cm H2O降至PEEP为0cm H₂O时的12±3cm H₂O（p＜0.001）。V/Q值没有变化

结  论

在低潮气量单肺通气时，高呼气末正压水平可改善肺功能且不增加V/Q，同时可降低驱动压力。

原始文献摘要

Background: Arterial oxygenation is often impaired during one-lung ventilation, due to both pulmonary shunt and atelectasis. The use of low tidal volume (VT) (5 ml/kg predicted body weight) in the context of a lung-protective approach exacerbates atelectasis. This study sought to determine the combined physiologic effects of positive end-expiratory pressure and low VT during one-lung ventilation.

Methods: Data from 41 patients studied during general anesthesia for thoracic surgery were collected and analyzed. Shunt fraction, high V/Q and respiratory mechanics were measured at positive end-expiratory pressure 0 cm H₂O during bilateral lung ventilation and one-lung ventilation and, subsequently, during one-lung ventilation at 5 or 10 cm H₂O of positive end-expiratory pressure. Shunt fraction and high V/Q were measured using variation of inspired oxygen fraction and measurement of respiratory gas concentration and arterial blood gas. The level of positive end-expiratory pressure was applied in random order and maintained for 15 min before measurements.

Results: During one-lung ventilation, increasing positive end-expiratory pressure from 0 cm H2O to 5cm H₂O and 10 cm H₂O resulted in a shunt fraction decrease of 5% (0 to 11) and 11% (5 to 16), respectively (P<0.001). The PaO2/FIO₂ ratio increased significantly only at a positive end-expiratory pressure of 10 cm H₂O (P < 0.001). Driving pressure decreased from 16±3cm H₂O at a positive end-expiratory pressure of 0 cm H₂O to 12±3cm H₂O at a positive end-expiratory pressure of 10cm H₂O (P < 0.001). The high V/Q ratio did not change.

Conclusions: During low VT one-lung ventilation, high positive end-expiratory pressure levels improve pulmonary function without increasing high V/ Q and reduce driving pressure.

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