D. M. Peterson1, S. M. Black3, S. Bennett3, C. Dumond3, D. Hayes2, R. S. Higgins3, B. A. Whitson3 1The Ohio State University,College Of Medicine,Columbus, OH, USA 2Nationwide Children’s Hospital (Columbus Children’s Hospital),Heart-Lung Transplant,Columbus, OH, USA 3The Ohio State University Wexner Medical Center,Surgery,Columbus, OH, USA
Introduction:
Ex-Vivo lung perfusion (EVLP) is a technique that enables the assessment of donor organs and the possibility of organ resuscitation potentially expand the donor pool. Currently, there is no defined method of assessing total organ edema, a condition that may contribute to primary graft dysfunction, poor gas exchange, and organ failure. We investigated the use of electrical impedance as a non-invasive measurement of extra-vascular water and organ edema in lungs undergoing EVLP.
Methods:
Adult porcine lungs were procured and assessed in an IACUC approved protocol in a fashion similar to clinical practice. There were three perfusion groupings: Steen ®, saline and modified cell culture media (N=6). Standard procurement techniques were used with the pulmonary artery being antegrade flushed in situ. At initiation of EVLP, the flow was increased to 40% of cardiac output with 1.5 Liters of perfusate slowly warmed to 37 ͦ C over 30 minutes. Lungs were ventilated at a tidal volume of 8 ml/kg, PEEP of 5 cmH2O, and respiratory rate of 8 bpm. Peak airway pressure, compliance, impedance, blood gas and extra vascular lung water (EVLW) were evaluated every 60 minutes. EVLW was evaluated using a PiCCO ® catheter in-line with the perfusion circuit. Impedance measurements were taken in the left lower lobe.
Results:
The median pig weight was 40kg. Over the perfusion, lungs with the greatest injury had more significant changes in impedance values compared to those with less injury. Lungs perfused with Steen had less injury when compared to those with saline or modified cell culture media. As expected, impedance decreased in all lungs over time on the perfusion circuit. Decreases in impedance not only correlated with decreases in gas exchange (Delta PaO2/FiO2) but also preceded them alluding to a predictive component of impedance for changes in gas exchange. Decreases in impedance also correlated with decreases in lung compliance. Lungs perfused with Steen showed minimal overall change in impedance (38-134 Ω) compared to those perfused with modified cell culture (1425-1569 Ω) over a 4 hour perfusion period.
Conclusion:
Electrical impedance offers a non-invasive method to measure lung tissue edema in a porcine EVLP model. Correlations between impedance, compliance and Delta PaO2/FiO2 values suggest impedance is a valid method for evaluating in lung edema over time during EVLP. Impedance offers increased sensitivity for lung water and appears to have predictive value for changes in gas exchange before the oxygenation changes. This technique could provide real time evaluation of donor lungs prior to transplantation. Further studies evaluating the use of impedance in other potential donor organs perfused ex vivo warrants investigation.
