Unmatched ventilation and perfusion measured by electrical impedance tomography predicts the outcome of ARDS

Abstract

Background 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 PaO2/FiO2 and compliance. Methods 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. Results 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 PaO2/FiO2 ratio (r = − 0.293, p = 0.039). Conclusions 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.

Three broad classifications of acute respiratory failure etiologies based on regional ventilation and perfusion by electrical impedance tomography: a hypothesis-generating study

“…Functional changes in ventilation and perfusion are complicated and variable in different lung lesions. Correlation between PaO 2 /FiO 2 and EIT parameters were weak, which coincided with a recent study from Spinelli et al [ 45 ]. They found a weak negative correlation between the percentage of only perfused units and PaO 2 /FiO 2 ratio ( r = − 0.293, P = 0.039) in ARDS patients.…”

Lung Perfusion Assessment by Bedside Electrical Impedance Tomography in Critically Ill Patients

“…The slope analysis was validated against PET in animal studies (Borges et al, 2012;Bluth et al, 2019). Several recent publications on lung perfusion using EIT and saline bolus injections in human subjects adopted the slope analysis (He et al, 2020a,b;Mauri et al, 2020;Spinelli et al, 2021). A high slope in the lung regional time-impedance curves obtained following a saline injection indicates a high accumulation of saline, which also reflects a high lung blood perfusion.…”

“…The experimental and clinical studies using the saline bolus EIT method to visually assess lung perfusion are summarized in Tables 2-4 (Frerichs et al, 2002;Borges et al, 2012;Nguyen et al, 2013Nguyen et al, , 2015Reinius et al, 2015;Hentze et al, 2018;Bluth et al, 2019;Grassi et al, 2020;He et al, 2020aHe et al, ,b,c, 2021bMauri et al, 2020;Safaee Fakhr et al, 2020;Kircher et al, 2021;Spinelli et al, 2021;Yuan et al, 2021). The administration of saline boluses, data analyses, precision, and cutoff values differ among…”

Designing a bench for testing medically and technically an information and measuring system for multi-frequency electrical impedance tomography of human lungs

“…Currently, the problem of long-term monitoring of the functional state of human lungs is one of the most important areas of respiratory support for patients. Among them, the possibility of long-term bedside monitoring of the breathing process in the pre-and postoperative period, including patients connected to devices of artificial ventilation of lungs (AVL) [4][5][6], is of great clinical importance.…”

“…Study [5] briefly summarizes the current state of the EIT for visualization of ventilation and perfusion. The authors measuring system of multi-frequency electric impedance tomography (IMS MF EIT) of human lungs, was proposed and manufactured.…”