Direct lung ultrasonography as a complementary intraoperative tool for lobar graft assessment in lobar lung transplantation

Background: Lobar lung transplantation (LLTx) is an important strategy for addressing donor shortage and donor-recipient size mismatch, particularly in pediatric and small-sized recipients. However, when donor lung injury is heterogeneous, graft selection remains challenging because conventional donor assessment is primarily based on whole-lung information or subjective intraoperative judgment. The aim of this study was to evaluate the associations among multiple intraoperative donor lung assessment methods, including direct lung ultrasonography, and early post-transplant graft outcomes in a large-animal LLTx model. Methods: A swine model of aspiration-induced heterogeneous donor lung injury was established in male Yorkshire pigs. During donor procurement, the left upper lobe was assessed using chest radiography, visual inspection, palpation, deflation testing, differential pulmonary vein blood gas (DPVBG) analysis, local airway carbon dioxide measurement, and direct lung ultrasonography. The left upper lobe was then transplanted into a smaller recipient pig and reperfused for 4 hours. Associations between pretransplant assessments and graft outcomes after 4 hours of reperfusion, including pulmonary venous oxygenation, lung injury score (LIS), and wet-to-dry weight ratio, were analyzed using Spearman’s rank correlation. Results: Nine left upper lobar transplantations were completed successfully, and all recipients survived to the end of the 4-hour reperfusion period. Direct lung ultrasonography and deflation testing both showed strong associations with oxygenation (r s =−0.9356, P<0.001; and r s =−0.9354, P=0.002, respectively) and LIS (r s =0.9611, P<0.001; and r s =0.9433, P=0.002, respectively), whereas chest radiography, visual inspection, palpation, and DPVBG showed more variable associations. Local airway carbon dioxide measurement was not strongly associated with early graft function. In a representative heterogeneous-injury case, chest radiography suggested diffuse impairment, whereas ultrasonography demonstrated milder findings in the upper lobe than in the lower lobe, and the transplanted upper lobe achieved favorable oxygenation after transplantation. Conclusions: Direct lung ultrasonography provides standardized regional intraoperative imaging information that may complement conventional graft assessment in LLTx. Rather than replacing established clinical judgment, this approach may support more informed lobar graft selection when donor lung injury is heterogeneous.