Pulmonary Stress Index During Ex Vivo Lung Perfusion is Associated with Evlp and Lung Transplant Recipient Outcomes

PurposeDuring ex vivo lung perfusion (EVLP), hourly assessment of ventilator parameters, such as compliance, are used to assess suitability of lungs for transplant. Previous analysis of the pressure-time curve during EVLP suggested the stress index (SI) as an additional marker of tidal recruitment (SI <0.95) and tidal hyperinflation (SI>1.05), which are mechanisms of lung injury caused by mechanical ventilation. Herein, we sought to validate the change of the SI over time during EVLP and its association with EVLP and lung transplant recipient outcome.MethodsFlow, volume and airway pressures were recorded continuously from a Servo-i ventilator during the entire duration of n=50 clinical EVLP cases, of which 32 were accepted for transplant. Breath-by-breath measurements of the SI were extracted during standard EVLP assessment settings (VT= 10 ml/kg donor predicted body weight, delivered with squared flow waveform at 10 breaths/min). We evaluated whether the SI during EVLP and the difference of SI (Δ-SI) above or below its safe threshold (0.95-1.05) predicted EVLP outcome and post-transplant recipient duration of mechanical ventilation.ResultsMedian [min-max] SI during EVLP changed from 1.06 [0.68-1.63] to 1.07 [0.78-1.6] in accepted cases and from 1.2 [0.7-1.7] to 1.3 [0.6-1.6] in declined cases. Δ-SI was significantly higher in lungs declined for transplant compared to those accepted (p<0.01) (Figure a). In EVLP cases accepted for transplant, SI was lower in lungs whose recipients had post-transplant duration of mechanical ventilation of ≤72h compared to those with mechanical ventilation >72h (1.05 [0.8-1.2] vs 1.14 [1-1.6];p<0.05) (Figure b).ConclusionStress index is a novel indicator of lung injury during EVLP that can predict EVLP outcome and short-term outcome of lung transplant recipients. Use of this parameter may guide organ-specific ventilation settings to minimize lung injury from mechanical stress and enhance clinical lung management and decision making during EVLP. During ex vivo lung perfusion (EVLP), hourly assessment of ventilator parameters, such as compliance, are used to assess suitability of lungs for transplant. Previous analysis of the pressure-time curve during EVLP suggested the stress index (SI) as an additional marker of tidal recruitment (SI <0.95) and tidal hyperinflation (SI>1.05), which are mechanisms of lung injury caused by mechanical ventilation. Herein, we sought to validate the change of the SI over time during EVLP and its association with EVLP and lung transplant recipient outcome. Flow, volume and airway pressures were recorded continuously from a Servo-i ventilator during the entire duration of n=50 clinical EVLP cases, of which 32 were accepted for transplant. Breath-by-breath measurements of the SI were extracted during standard EVLP assessment settings (VT= 10 ml/kg donor predicted body weight, delivered with squared flow waveform at 10 breaths/min). We evaluated whether the SI during EVLP and the difference of SI (Δ-SI) above or below its safe threshold (0.95-1.05) predicted EVLP outcome and post-transplant recipient duration of mechanical ventilation. Median [min-max] SI during EVLP changed from 1.06 [0.68-1.63] to 1.07 [0.78-1.6] in accepted cases and from 1.2 [0.7-1.7] to 1.3 [0.6-1.6] in declined cases. Δ-SI was significantly higher in lungs declined for transplant compared to those accepted (p<0.01) (Figure a). In EVLP cases accepted for transplant, SI was lower in lungs whose recipients had post-transplant duration of mechanical ventilation of ≤72h compared to those with mechanical ventilation >72h (1.05 [0.8-1.2] vs 1.14 [1-1.6];p<0.05) (Figure b). Stress index is a novel indicator of lung injury during EVLP that can predict EVLP outcome and short-term outcome of lung transplant recipients. Use of this parameter may guide organ-specific ventilation settings to minimize lung injury from mechanical stress and enhance clinical lung management and decision making during EVLP.