Abstract摘要
Study objective
Comparison of flow-controlled ventilation (FCV) to standard of pressure-controlled ventilation (PCV) in thoracic surgery procedures requiring one-lung ventilation.
研究目的
比较流量控制通气（FCV）与标准压力控制通气（PCV）在需要单肺通气的胸部手术程序中的效果。
Design
Prospective, non-blinded, randomized, controlled trial.
设计
前瞻性、非盲、随机、对照试验。
Setting
Operating theater at a university hospital, Austria.
设置
奥地利一所大学医院的手术室。
Patients
Patients scheduled for elective, thoracic surgery.
患者
计划进行选择性胸部手术的患者。
Interventions
Participants received ventilation randomly either with FCV or PCV per-protocol for the duration of anesthesia.
干预措施
参与者在麻醉期间随机接受FCV或PCV通气，按照协议进行。
Measurements
The primary endpoint was oxygenation assessed by paO2 / FiO2 ratio 30 min after the start of OLV. Secondary endpoints included the required minute volume for CO2 removal, applied mechanical power and incidence of postoperative pulmonary complications.
测量
主要终点是开始单肺通气（OLV）后30分钟通过paO2 / FiO2比率评估的氧合情况。次要终点包括为二氧化碳清除所需的分钟通气量、应用的机械功率以及术后肺部并发症的发生率。
Main results
A total of 46 patients were enrolled and 43 included in the primary analysis. The primary endpoint paO2 / FiO2 ratio was significantly higher in the FCV group (n = 21) compared to the control group (PCV n = 22) (187 vs 136 mmHg, MD 39 (95 % CI 1 to 75); p = 0.047). The required respiratory minute volume to obtain comparable mild hypercapnia during OLV was significantly lower in FCV (3.0 vs 4.5 l/min, MD -1.3 (95 % CI -1.9 to −0.8); p < 0.001). The applied mechanical power was also significantly lower (3.5 versus 7.6 J/min, MD -3.8 (95 % CI -5.3 to −2.7); p < 0.001).
主要结果
共有46名患者被纳入研究，43名患者纳入主要分析。FCV组（n = 21）的主要终点paO2 / FiO2比率显著高于对照组（PCV n = 22）（187 vs 136毫米汞柱，MD 39（95% CI 1至75）；p = 0.047）。在OLV期间获得相似轻度高碳酸血症所需的呼吸分钟通气量在FCV中显著较低（3.0 vs 4.5 l/min，MD -1.3（95% CI -1.9至−0.8）；p < 0.001）。应用的机械功率也显著较低（3.5 vs 7.6 J/min，MD -3.8（95% CI -5.3至−2.7）；p < 0.001）。
Conclusions
In this single-center randomized controlled trial, flow-controlled ventilation improved gas exchange parameters in terms of oxygenation and carbon dioxide removal during one-lung ventilation in patients undergoing thoracic surgery and reduced the mechanical impact of artificial ventilation.
Primary outcome timepoint
The primary outcome measure (paO2 / FiO2 ratio after 30 min of OLV) was significantly higher in the intervention group (187 versus 136 mmHg, MD 39 (95 % CI 1 to 75); p = 0.047) at comparable paCO2 values. Therefore, in accordance with the study protocol, the FiO2 in the FCV group could be further reduced at this point to achieve the same paO2 target of 75–120 mmHg (Table 2). Evaluation of respiratory parameters revealed comparable pressure settings (PEEP, Ppeak and ΔP) in the control and intervention group (Table 2) after correction of FCV values for the pressure gradient related to continuous gas flow and resistance as described in the Method section. [16,17] The applied VT's were higher in the FCV group (7.4 versus 5.1 ml/kg, MD 2.2 (95 % CI 1.7 to 2.9); p < 0.001), whereas the respiratory rate was lower (7 versus 14 /min, MD -7 (95 % CI -8 to − 6); p < 0.001). Also, minute volume was lower in the FCV group (3.0 versus 4.5 l/min, MD -1.3 (95 % CI -1.9 to − 0.8); p < 0.001). Calculation of MP resulted in lower values for FCV (3.5 versus 7.6 J/min, MD -3.8 (95 % CI -5.3 to − 2.7); p < 0.001). The heart rate was found to be higher in FCV (76 versus 63 /min, MD 10 (95% CI 4 to 17); p = 0.005), whereas MAP and CVP were comparable in both groups.
主要结果时间点
主要结果指标（OLV后30分钟的paO2/FiO2比率）在干预组中显著更高（187对比136毫米汞柱，平均差异39（95%置信区间1至75）；p = 0.047），在可比的paCO2值下。因此，按照研究方案，此时可以在FCV组进一步降低FiO2，以达到相同的paO2目标75-120毫米汞柱（表2）。对呼吸参数的评估显示，在校正FCV值以反映连续气流和阻力相关的压力梯度后（如方法部分所述），对照组和干预组的压力设置（PEEP、Ppeak和ΔP）是可比的（表2）。[16,17] FCV组应用的VT更高（7.4对比5.1毫升/公斤，平均差异2.2（95%置信区间1.7至2.9）；p < 0.001），而呼吸频率更低（7对比14次/分钟，平均差异-7（95%置信区间-8至-6）；p < 0.001）。此外，FCV组的分钟通气量也较低（3.0对比4.5升/分钟，平均差异-1.3（95%置信区间-1.9至-0.8）；p < 0.001）。计算MP结果显示FCV组的值较低（3.5对比7.6焦耳/分钟，平均差异-3.8（95%置信区间-5.3至-2.7）；p < 0.001）。心率在FCV组中被发现更高（76对比63次/分钟，平均差异10（95%置信区间4至17）；p = 0.005），而MAP和CVP在两组中是可比的。
3.2. Course of parameters
During TLV in both the supine and lateral position, the paO2 / FiO2 ratio and paCO2 levels were comparable in both groups (Fig. 3), despite the use of a lower FiO2 in FCV (35 versus 46 %, MD -11 (95 % CI -15 to −7); p < 0.001). Compliance-guided PEEP values were similar in PCV and FCV, but Ppeak was higher in FCV after titration (15.8 versus 14.2 cmH2O, MD 1.6 (95 % CI 0.5 to 2.6); p = 0.006). In FCV, ΔP was higher (9.9 versus 9.0 cmH2O, MD 0.9 (95 % CI 0.1 to 1.7); p = 0.037) and VT greater (10.0 versus 7.1 ml/kg, MD 2.9 (95 % CI 2.3 to 3.5); p < 0.001). The respiratory rate was lower in the FCV group (7.8 versus 12.1 /min; MD − 4.3 (95 % CI -5.1 to − 3.4); p < 0.001) as well as the minute volume (4.2 versus 5.3 l/min, MD -1.1 (95 % CI -1.5 to − 0.7); p < 0.001),
leading to a lower applied mechanical power (4.9 versus 7.5 J/min, MD -2.6 (95 % CI -3.3 to − 1.8); p < 0.001) compared to the PCV group. The heart rate was higher in FCV (71 versus 62 /min, MD 8 (95 % CI 2 to 15); p = 0.016), whereas mean arterial pressure and central venous pressuredid not significantly differ between groups during TLV. Application of a linear mixed-effects model for the OLV phase revealed an overall paO2 / FiO2 value of 200 mmHg for the FCV group compared to 161 mmHg for the PCV group, (MD 38, (95 % CI -1 to 77); p = 0.061). However, oxygenation increased over time in FCV leading to statistically significantly higher values after 30 and 60 min (Table 2, Fig. 3A). All other outcome parameters for the OLV phase can be found in Table 2.
3.2. 参数变化过程
在仰卧位和侧卧位的TLV期间，两组的paO2 / FiO2比率和paCO2水平相当（图3），尽管FCV组使用了较低的FiO2（35%对比46%，平均差异-11（95%置信区间-15到-7）；p < 0.001）。在PCV和FCV中，顺应性指导的PEEP值相似，但在滴定后FCV的Ppeak更高（15.8对比14.2 cmH2O，平均差异1.6（95%置信区间0.5到2.6）；p = 0.006）。在FCV中，ΔP更高（9.9对比9.0 cmH2O，平均差异0.9（95%置信区间0.1到1.7）；p = 0.037），VT更大（10.0对比7.1 ml/kg，平均差异2.9（95%置信区间2.3到3.5）；p < 0.001）。FCV组的呼吸频率更低（7.8对比12.1次/分钟；平均差异-4.3（95%置信区间-5.1到-3.4）；p < 0.001），分钟通气量也更低（4.2对比5.3 l/min，平均差异-1.1（95%置信区间-1.5到-0.7）；p < 0.001），导致应用的机械功率低于PCV组（4.9对比7.5 J/min，平均差异-2.6（95%置信区间-3.3到-1.8）；p < 0.001）。FCV组的心率更高（71对比62次/分钟，平均差异8（95%置信区间2到15）；p = 0.016），而平均动脉压和中心静脉压在TLV期间两组间没有显著差异。对OLV阶段应用线性混合效应模型显示，FCV组的总体paO2 / FiO2值为200 mmHg，而PCV组为161 mmHg，（平均差异38，（95%置信区间-1到77）；p = 0.061）。然而，FCV组的氧合随着时间增加，在30分钟和60分钟后达到统计学上显著更高的值（表2，图3A）。OLV阶段的所有其他结果参数可以在表2中找到。
3.3. Postoperative outcome parameters
Measurement of cytokine serum levels showed comparable values in both groups (Table S1, supplemental appendix). The incidence of postoperative pulmonary complications after lung surgery did not differ significantly between FCV and PCV (19.5 versus 31.8 %; p = 0.488), neither did length of PACU and hospital stay.
3.3. 术后结果参数
测量细胞因子血清水平显示两组的值相当（表S1，补充附录）。肺部手术后肺部并发症的发生率在FCV和PCV之间没有显著差异（19.5%对比31.8%；p = 0.488），PACU停留时间和住院时间也是如此。
