Beyond static cold storage: active hypothermic lung preservation at 10°C using perfusion and CPAP in a porcine model

Background: Lung preservation remains fundamentally passive, relying on static cold storage at 4°C, which is limited by non-uniform cooling, lack of ventilation, and restricted ischemic tolerance. Although storage at 10°C improves mitochondrial preservation, it remains a static approach. We propose a shift toward controlled hypothermic organ support by combining continuous vascular perfusion and airway stabilization at 10°C.
Methods: In a porcine model (n=8), lungs were assigned to active hypothermic preservation at 10°C with continuous Steen® perfusion and CPAP (n=4) or conventional static cold storage at 4°C (n=4). The active system used a closed circuit (1500 mL Steen® solution) perfused at 5–10% of estimated cardiac output (mean flow 0.278 ± 0.01 L/min), with continuous CPAP (3 cmH₂O above pulmonary arterial pressure). Lungs were assessed up to 12 hours using histology, weight variation, hemodynamics, thermal profiling, and biomarker analysis (cf-mtDNA, TNF-α, IL-6).
Results: Active hypothermic preservation was feasible in all cases without technical failure. After 12 hours, 75% (3/4) of lungs in the active group preserved normal alveolar architecture (Grade 1), whereas all lungs in the static group (4/4) showed severe structural damage (Grade 3) after 6 hours (p<0.05).
The system maintained stable perfusion (mean pulmonary arterial pressure 9.16 ± 1.04 mmHg; pulmonary vascular resistance 7.12 ± 2.52 WU, excluding one outlier), supporting sustained vascular integrity during prolonged preservation.
Active preservation enabled controlled core-to-periphery cooling, with low arterial-to-venous temperature gradients (3.14 ± 1.20°C) and minimal external-to-airway gradients (0.49 ± 1.05°C), indicating effective thermal homogeneity across compartments.
Lungs in the active group showed an increase in weight (+24% ± 14.7) compared to dehydration in the static group (−4.75% ± 1.58; p=0.029), without corresponding histological evidence of severe alveolar edema, suggesting preserved alveolar patency despite fluid shifts.
Mitochondrial DNA levels remained stable over time (25.3,  30.9, 27.2 copies/µL), and inflammatory markers showed no consistent activation pattern.
Conclusions: We introduce a novel active hypothermic lung preservation platform integrating perfusion and ventilation at 10°C. This approach is feasible, achieves controlled and homogeneous cooling, and preserves lung structure during prolonged ischemia. By addressing key limitations of static storage, it may represent a transition from passive preservation to controlled hypothermic organ support. Further studies including functional validation and comparative models are warranted.