Lung Thermography as an Early Predictor of Pulmonary Function in Cellular Ex Vivo Lung Perfusion

Abstract

<h3>Purpose</h3> Infrared thermography is a real-time and non-invasive technique for detecting low temperatures in poorly perfused areas. We hypothesized that the temperature of injured lungs may not increase as rapidly as that of non-injured lungs during the initial 1 h rewarming phase in ex vivo lung perfusion (EVLP). In this study, we investigated the effect of graft thermal changes during the rewarming phase on pulmonary function in cellular EVLP using a porcine lung model. <h3>Methods</h3> Fifteen pigs were divided into three groups: control group (no warm ischemia) or donation after circulatory death groups with 60 or 90 min of warm ischemia (n = 5, each). Thermal images of the lower lobes were continuously recorded from the bottom of organ chamber using infrared thermography. Lungs were perfused according to the Lund protocol. In the initial 1 h, lungs were gradually rewarmed by increasing the flow rate in a stepwise fashion. At 2 h, transplant suitability was decided, and lung tissue samples were collected to measure wet/dry (W/D). <h3>Results</h3> Lung surface temperatures of non-suitable cases (n = 6) were significantly lower than in suitable cases (n = 9) at 8 min (25.1 ± 0.6 vs. 27.8 ± 1.2°C, <i>P</i> < 0.001, cut-off = 26°C, AUC = 1.0, Figure A), while there was no difference between the two groups at 0-4 min and 12-120 min. There was a significant negative correlation between lung surface temperature at 8 min and W/D at 2 h in the lower lobes (R = -0.769, <i>P</i> < 0.001, Figure B). Lung thermography < 26°C at 8 min was significantly associated with a lower PaO₂/FiO₂, higher peak inspiratory pressure, higher lung weight gain, higher shunt ratio at 1 h and higher pulmonary vascular resistance at 8 min (<i>P</i> < 0.05, each). <h3>Conclusion</h3> These data suggest that a lung surface temperature of < 26°C at 8 min was significantly correlated with poor pulmonary function and transplant non-suitability. This finding indicates that lung surface temperature during the rewarming phase can be a good early predictor of pulmonary function in cellular EVLP and might be applicable for clinical EVLP.