BACKGROUND In obese patients, high closing capacity and low functional residual capacity increase the risk for expiratory alveolar collapse. Constant expiratory flow, as provided by the new flow-controlled ventilation (FCV) mode, was shown to improve lung recruitment. We hypothesized that lung aeration and respiratory mechanics improve in obese patients during FCV. METHODS We compared FCV and volume-controlled (VCV) ventilation in 23 obese patients in a randomized crossover setting. Starting with baseline measurements, ventilation settings were kept identical except for the ventilation mode related differences (VCV: inspiration to expiration ratio 1:2 with passive expiration, FCV: inspiration to expiration ratio 1:1 with active, linearized expiration). Primary endpoint of the study was the change of end-expiratory lung volume compared to baseline ventilation. Secondary endpoints were the change of mean lung volume, respiratory mechanics and hemodynamic variables. RESULTS The loss of end-expiratory lung volume and mean lung volume compared to baseline was lower during FCV compared to VCV (end-expiratory lung volume: FCV, - 126 ± 207 ml; VCV, - 316 ± 254 ml; p < 0.001, mean lung volume: FCV, - 108.2 ± 198.6 ml; VCV, - 315.8 ± 252.1 ml; p < 0.001) and at comparable plateau pressure (baseline, 19.6 ± 3.7; VCV, 20.2 ± 3.4; FCV, 20.2 ± 3.8 cmH2O; p = 0.441), mean tracheal pressure was higher (baseline, 13.1 ± 1.1; VCV, 12.9 ± 1.2; FCV, 14.8 ± 2.2 cmH2O; p < 0.001). All other respiratory and hemodynamic variables were comparable between the ventilation modes. CONCLUSIONS This study demonstrates that, compared to VCV, FCV improves regional ventilation distribution of the lung at comparable PEEP, tidal volume, PPlat and ventilation frequency. The increase in end-expiratory lung volume during FCV was probably caused by the increased mean tracheal pressure which can be attributed to the linearized expiratory pressure decline. TRIAL REGISTRATION German Clinical Trials Register: DRKS00014925. Registered 12 July 2018.

中文翻译：

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流量控制通气（FCV）改善了肥胖患者的局部通气-一项随机对照交叉试验。

背景技术在肥胖患者中，高闭合能力和低功能残余能力增加了呼气性肺泡塌陷的风险。由新的流量控制通气（FCV）模式提供的恒定呼气流量可改善肺部募集。我们假设肥胖患者在FCV期间肺通气和呼吸力学改善。方法我们比较了随机交叉设置的23例肥胖患者的FCV和容积控制（VCV）通气。从基线测量开始，除与通气模式相关的差异外，通气设置保持相同（VCV：被动式呼气的吸气与呼气比为1：2，FCV：主动式线性呼气的吸气与呼气比为1：1）。该研究的主要终点是呼气末肺体积与基线通气相比的变化。次要终点是平均肺容量，呼吸力学和血液动力学变量的变化。结果FCV期间的呼气末肺体积损失和平均肺体积与基线相比低于VCV（呼气末肺体积：-FCV，-126±207 ml; VCV，-316±254 ml; p <0.001，平均肺活量：FCV-108.2±198.6 ml; VCV-315.8±252.1 ml; p <0.001），并且在相当的高原压力下（基线，19.6±3.7; VCV，20.2±3.4; FCV，20.2±3.8 cmH2O; p = 0.441），平均气管压力较高（基线，13.1±1.1; VCV，12.9±1.2; FCV，14.8±2.2 cmH2O; p <0.001）。在通气模式之间，所有其他呼吸和血液动力学变量均具有可比性。结论该研究表明，与VCV相比，FCV在可比较的PEEP，潮气量，PPlat和通气频率下改善了肺的局部通气分布。FCV期间呼气末肺体积的增加可能是由于平均气管压力增加所致，这可归因于线性的呼气压力下降。试验注册德国临床试验注册：DRKS00014925。2018年7月12日注册。DRKS00014925。2018年7月12日注册。DRKS00014925。2018年7月12日注册。