Electrical impedance tomography (EIT) for quantification of pulmonary edema in acute lung injury

Abstract

BackgroundAssessment of pulmonary edema is a key factor in monitoring and guidance of therapy in critically ill patients. To date, methods available at the bedside for estimating the physiologic correlate of pulmonary edema, extravascular lung water, often are unreliable or require invasive measurements. The aim of the present study was to develop a novel approach to reliably assess extravascular lung water by making use of the functional imaging capabilities of electrical impedance tomography.MethodsThirty domestic pigs were anesthetized and randomized to three different groups. Group 1 was a sham group with no lung injury. Group 2 had acute lung injury induced by saline lavage. Group 3 had vascular lung injury induced by intravenous injection of oleic acid. A novel, noninvasive technique using changes in thoracic electrical impedance with lateral body rotation was used to measure a new metric, the lung water ratioEIT, which reflects total extravascular lung water. The lung water ratioEIT was compared with postmortem gravimetric lung water analysis and transcardiopulmonary thermodilution measurements.ResultsA significant correlation was found between extravascular lung water as measured by postmortem gravimetric analysis and electrical impedance tomography (r = 0.80; p < 0.05). Significant changes after lung injury were found in groups 2 and 3 in extravascular lung water derived from transcardiopulmonary thermodilution as well as in measurements derived by lung water ratioEIT.ConclusionsExtravascular lung water could be determined noninvasively by assessing characteristic changes observed on electrical impedance tomograms during lateral body rotation. The novel lung water ratioEIT holds promise to become a noninvasive bedside measure of pulmonary edema.

Noninvasive Monitoring of Oxygen and Ventilation

“…Some applications of EIT in both humans and experimental models have highlighted the assessment of regional distribution of ventilation for PEEP titration, [95][96][97] assessing differences between ventilator modes, 98 detection of pneumothorax, 100,101 and quantification of pulmonary edema. 102 Further delineation of these studies is beyond the scope of the present review. Importantly, only a limited number of the investigations have been conducted in pediatric populations.…”

Electrical Impedance Tomography During Mechanical Ventilation

“…47 In an experimental animal model, a novel noninvasive technique using changes in thoracic EIT with lateral body rotation was able to estimate extravascular lung water. 48 This lung water EIT ratio holds promise in assisting clinicians with fluid resuscitation and management while minimizing ventilator-induced lung injury.…”

New biosensors and wearables for cardiorespiratory telemonitoring

“…However, they have a high temporal resolution. They are therefore ideal to monitor imbalance between lung inflation [4] or even potentially pulmonary edema [5]. Recent research suggests that EIT may also be extremely useful at heart beat frequencies, because it may capture directly aortic PTT (pulse transit time) and therefore provide a good surrogate for mean BP (blood pressure) [6], or PWV (pulse wave velocity) enabling the measurement of pulmonary blood pressure [7].…”