Electrical Impedance as a Noninvasive Metric of Quality in Allografts Undergoing Normothermic Ex Vivo Lung Perfusion

Abstract

Ex vivo lung perfusion (EVLP) increases the pool of suitable organs for transplant by facilitating assessment and repair at normothermia, thereby improving identification of quality of marginal organs. However, there exists no current objective approach for assessing total organ edema. We sought to evaluate the use of electrical impedance as a metric to assess total organ edema in lungs undergoing EVLP. Adult porcine lungs (40 kg) underwent normothermic EVLP for 4 hours. To induce varying degrees of lung injury, the allografts were perfused with either Steen, a modified cell culture media, or 0.9% normal saline. Physiologic parameters (peak airway pressure and compliance), pulmonary artery and left atrial blood gases, and extravascular lung water measurements were evaluated over time. Wet-to-dry ratios were evaluated postperfusion. Modified Murray scoring was used to calculate lung injury. Impedance values were associated with lung injury scores (p = 0.007). Peak airway pressure (p = 0.01) and PaO2/FiO2 ratios (p = 0.005) were both significantly associated with reduced impedance. Compliance was not associated with impedance (p = 0.07). Wet/dry ratios were significantly associated with impedance and Murray Scoring within perfusion groups of Steen, Saline, and Modified Cell Culture (p = 0.0186, 0.0142, 0.0002, respectively). Electrical impedance offers a noninvasive modality for measuring lung quality as assessed by tissue edema in a porcine model of normothermic EVLP. Further studies evaluating the use of impedance to assess organ edema as a quality marker in human clinical models and abdominal organs undergoing ex vivo perfusion warrant investigation.

Single‐center experience of ex vivo lung perfusion and subsequent lung transplantation

“…At our institution, experienced lung transplant surgeons routinely assess the lung by direct manipulation to detect local edema. Other investigators recently demonstrated the efficacy of gross lung weight or novel imaging applications (e.g., echocardiography, impedance, and hyperspectral camera) to detect such localized edema in an objective manner 12–15 . These methods may provide objective measurements to better define quality during EVLP.…”

Diagnostic and Therapeutic Implications of Ex Vivo Lung Perfusion in Lung Transplantation: Potential Benefits and Inherent Limitations

“…50 Electrical impedance tomography during EVLP has been introduced for assessing lung edema, with the values being inversely correlated with extravascular lung water, peak airway pressure, and lung injury score. 51 Notably, the stress index, a ventilatory parameter derived from the pressure-time curve, demonstrated superiority over lung compliance in identifying injurious mechanical ventilation during EVLP, which was positively correlated with the duration of mechanical ventilation and the length of stay in the ICU and hospital. 52 Therefore, these physical variables might be reasonable for predicting lung function before LTx or short-term posttransplant outcomes.…”

Real-Time Monitoring Using Multiplexed Multi-Electrode Bioelectrical Impedance Spectroscopy for the Stratification of Vascularized Composite Allografts: A Perspective on Predictive Analytics

“…Peterson et al [ 47 ] used bioimpedance to study total organ edema of porcine lungs undergoing normothermic extravascular lung perfusion (EVLP). They used Steen, an asanguinous and hyperosmolar solution, normal saline (0.9%), and cell culture media to determine if bioimpedance was associated with vascular lung water and lung injury severity.…”