SI-EVLP Study: STRESS INDEX in Lung Reconditioning

Increase of interest about technique of Ex-Vivo Lung Perfusion (EVLP) has highlighted the need of new approaches to respiratory mechanics monitoring to prevent lung stress in atypical physiological settings.

Airway pressure/time curve (Paw-t) shape analysis at constant flow ventilation (Stress Index, SI) is thought to be predictor of lung stress; so the SI coefficient may therefore identify and quantify mechanical stress during ventilation. (1) In experimental studies, the threshold values for SI that best discriminated lungs with signs of Ventilator Induced Lung Injury ranged between 0.9 and 1.1. (2) During EVLP, the isolated lungs are free from the effect of chest wall impairment and represent the effective response of lung parenchyma to ventilatory setting.

Use of SI monitoring in isolated and perfuse lung reconditioning, may be an useful tool to prevent hyperinflation and opening-closing conditions by titrating optimal protective ventilation As previously reported by our group, in the first trial of lung reconditioning, signs of mechanical stress were detected with Paw-t curve. (3) Therefore we implemented EVLP procedure with continuous stress index analysis to detect and quantify the occurrence of hyperinflation or opening closing condition.

Inclusion criteria

• High risk donor lung, define as:
• the ratio of partial pressure arterial oxygen and fraction of inspired oxygen less than 300
• pulmonary edema
• poor lung deflation or inflation
• blood transfusions exceeding 10 units
• donation after cardiac death as defined by Maastricht category III o IV

Exclusion criteria

• donors lung with established pneumonia
• donors lung with severe mechanical lung injury
• donors lung with gross gastric aspiration