Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.
Institute of Biomedical Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany.
Crit Care. 2021 Jun 3;25(1):192. doi: 10.1186/s13054-021-03615-4.
In acute respiratory distress syndrome (ARDS), non-ventilated perfused regions coexist with non-perfused ventilated regions within lungs. The number of unmatched regions might reflect ARDS severity and affect the risk of ventilation-induced lung injury. Despite pathophysiological relevance, unmatched ventilation and perfusion are not routinely assessed at the bedside. The aims of this study were to quantify unmatched ventilation and perfusion at the bedside by electrical impedance tomography (EIT) investigating their association with mortality in patients with ARDS and to explore the effects of positive end-expiratory pressure (PEEP) on unmatched ventilation and perfusion in subgroups of patients with different ARDS severity based on PaO/FiO and compliance.
Prospective observational study in 50 patients with mild (36%), moderate (46%), and severe (18%) ARDS under clinical ventilation settings. EIT was applied to measure the regional distribution of ventilation and perfusion using central venous bolus of saline 5% during end-inspiratory pause. We defined unmatched units as the percentage of only ventilated units plus the percentage of only perfused units.
Percentage of unmatched units was significantly higher in non-survivors compared to survivors (32[27-47]% vs. 21[17-27]%, p < 0.001). Percentage of unmatched units was an independent predictor of mortality (OR 1.22, 95% CI 1.07-1.39, p = 0.004) with an area under the ROC curve of 0.88 (95% CI 0.79-0.97, p < 0.001). The percentage of ventilation to the ventral region of the lung was higher than the percentage of ventilation to the dorsal region (32 [27-38]% vs. 18 [13-21]%, p < 0.001), while the opposite was true for perfusion (28 [22-38]% vs. 36 [32-44]%, p < 0.001). Higher percentage of only perfused units was correlated with lower dorsal ventilation (r = - 0.486, p < 0.001) and with lower PaO/FiO ratio (r = - 0.293, p = 0.039).
EIT allows bedside assessment of unmatched ventilation and perfusion in mechanically ventilated patients with ARDS. Measurement of unmatched units could identify patients at higher risk of death and could guide personalized treatment.
在急性呼吸窘迫综合征（ARDS）中，肺部存在未通气但有灌注的区域和通气但无灌注的区域共存。不匹配区域的数量可能反映 ARDS 的严重程度，并影响通气引起的肺损伤的风险。尽管具有病理生理学相关性，但在床边通常不评估不匹配的通气和灌注。本研究的目的是通过测量电断层成像（EIT）来量化床边不匹配的通气和灌注，并研究其与 ARDS 患者死亡率的关系，并根据 PaO/FiO 和顺应性，探讨不同 ARDS 严重程度亚组患者中，正呼气末压（PEEP）对不匹配通气和灌注的影响。
前瞻性观察性研究，纳入 50 名接受临床通气治疗的轻度（36%）、中度（46%）和重度（18%）ARDS 患者。在吸气末暂停时使用中心静脉推注 5%生理盐水，通过 EIT 测量通气和灌注的区域分布。我们将仅通气单位和仅灌注单位的百分比定义为不匹配单位。
与存活者相比，非幸存者的不匹配单位百分比明显更高（32[27-47]%比 21[17-27]%，p<0.001）。不匹配单位百分比是死亡率的独立预测因子（OR 1.22，95%CI 1.07-1.39，p=0.004），ROC 曲线下面积为 0.88（95%CI 0.79-0.97，p<0.001）。肺腹侧区域的通气百分比高于背侧区域（32[27-38]%比 18[13-21]%，p<0.001），而灌注则相反（28[22-38]%比 36[32-44]%，p<0.001）。仅灌注单位的百分比与背侧通气降低相关（r=-0.486，p<0.001），与 PaO/FiO 比值降低相关（r=-0.293，p=0.039）。
EIT 可在接受机械通气的 ARDS 患者床边评估不匹配的通气和灌注。不匹配单位的测量可以识别出死亡风险较高的患者，并指导个体化治疗。
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