Flow-controlled ventilation (FCV) allows expiratory flow control, reducing the collapse of the airways during expiration. The performance of FCV during one-lung ventilation (OLV) under intravascular normo- and hypovolaemia is currently unknown. In this explorative study, we hypothesised that OLV with FCV improves PaO2 and reduces mechanical power compared to volume-controlled ventilation (VCV). Sixteen juvenile pigs were randomly assigned to one of two groups: (1) intravascular normovolaemia (n = 8) and (2) intravascular hypovolaemia (n = 8). To mimic inflammation due to major thoracic surgery, a thoracotomy was performed, and 0.5 μg/kg/h lipopolysaccharides from Escherichia coli continuously administered intravenously. Animals were randomly assigned to OLV with one of two sequences (60 min per mode): (1) VCV–FCV or (2) FCV–VCV. Variables of gas exchange, haemodynamics and respiratory signals were collected 20, 40 and 60 min after initiation of OLV with each mechanical ventilation mode. The distribution of ventilation was determined using electrical impedance tomography (EIT). Oxygenation did not differ significantly between modes (P = 0.881). In the normovolaemia group, the corrected expired minute volume (P = 0.022) and positive end-expiratory pressure (PEEP) were lower during FCV than VCV. The minute volume (P ≤ 0.001), respiratory rate (P ≤ 0.001), total PEEP (P ≤ 0.001), resistance of the respiratory system (P ≤ 0.001), mechanical power (P ≤ 0.001) and resistive mechanical power (P ≤ 0.001) were lower during FCV than VCV irrespective of the volaemia status. The distribution of ventilation did not differ between both ventilation modes (P = 0.103). In a model of OLV in normo- and hypovolemic pigs, mechanical power was lower during FCV compared to VCV, without significant differences in oxygenation. Furthermore, the efficacy of ventilation was higher during FCV compared to VCV during normovolaemia.

中文翻译：

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流量与容量控制的单肺通气对猪气体交换和呼吸系统力学的比较影响

流量控制通气 (FCV) 允许呼气流量控制，减少呼气期间气道的塌陷。目前尚不清楚在血管内血容量正常和血容量不足的情况下单肺通气 (OLV) 期间 FCV 的性能。在这项探索性研究中，我们假设与容量控制通气 (VCV) 相比，带有 FCV 的 OLV 可改善 PaO2 并降低机械功率。16 只幼猪被随机分配到两组之一：(1) 血管内血容量正常 (n = 8) 和 (2) 血管内血容量不足 (n = 8)。为了模拟大胸手术引起的炎症，进行了开胸手术，并持续静脉内给予 0.5 μg/kg/h 来自大肠杆菌的脂多糖。动物被随机分配到 OLV 与两个序列之一（每个模式 60 分钟）：（1）VCV-FCV 或（2）FCV-VCV。在每种机械通气模式下开始 OLV 后 20、40 和 60 分钟收集气体交换、血液动力学和呼吸信号的变量。使用电阻抗断层扫描 (EIT) 确定通气分布。不同模式之间的氧合没有显着差异（P = 0.881）。在正常血容量组中，FCV 期间校正的呼气分钟通气量 (P = 0.022) 和呼气末正压 (PEEP) 低于 VCV。分钟容积（P≤0.001）、呼吸频率（P≤0.001）、总PEEP（P≤0.001）、呼吸系统阻力（P≤0.001）、机械功率（P≤0.001）和阻力机械功率（P≤0.001） 0.001) 在 FCV 期间低于 VCV，无论血容量状态如何。两种通风模式之间的通风分布没有差异（P = 0.103）。在血容量正常和血容量不足的猪的 OLV 模型中，与 VCV 相比，FCV 期间的机械功率较低，氧合没有显着差异。此外，与正常血容量期间的 VCV 相比，FCV 期间的通气效率更高。