Rapidpoint

Baseline (BL) arterial blood samples were taken 24 hours before anaesthesia by direct puncture of the carotid artery and analysed immediately for oxygen and carbon dioxide tensions (PaO₂ and PaCO₂ respectively) (Rapidpoint, Siemens, Germany).
A narrow circumferential strip of hair was clipped around the thorax directly caudal to the scapula (5^th- 6^th intercostal space) to aid consistent positioning of the electrical impedance belt. Electrically non-conductive ultrasound gel was applied to the clipped area and an EIT belt was placed under slight tension around the thorax. The belt was made of an elastic rubber tube on which 32 stainless steel contacts of 1 cm² were mounted equidistantly with the 1^st and 32^nd electrode being placed ventrally over the sternum. A surcingle was placed over the EIT belt to ensure all electrodes were in firm contact with the skin.
EIT measurements were performed for a period of 2 minutes or longer if at least 4 consecutive breaths without any artefacts (due to gross movement or muscle fasciculations) had not been recorded within this time, with the horse standing quietly and breathing regularly.

All data were recorded and stored with institutional approval (UHN REB#11-0170-AE). Our EVLP technique has been previously described^{1 (link)–5 (link)}. Briefly, lung assessments are made hourly and data are derived from an ICU-grade ventilator, pressure monitors and perfusate samples collected from the EVLP circuit. Additional features were extracted from the donor chart at the time of EVLP. Biochemical and oxygenation data were generated using a blood gas analyzer (RAPIDPoint, Siemens Healthcare, Germany). ∆pO₂ and ∆pCO₂ measurements were calculated as the venous-arterial difference in oxygenation and carbon dioxide partial pressure in perfusate solution, respectively. Protein measurements (i.e., IL-6, IL-8, IL-10, IL-1β) were completed by ELISA (Ella by Protein Simple Inc., San Jose, CA, USA and TORdx LUNG by SQI Diagnostics Inc., Toronto, ON, Canada). A summary of EVLP parameters is provided in Supplementary Table 6 and Supplementary Table 7. Primary Graft Dysfunction (PGD) grades were assigned in accordance with the International Society for Heart and Lung Transplantation working group 2016 definition^{36 (link)}.