Alveolar preservation with high inflation pressure and intermediate oxygen concentration reduces ischemia-reperfusion injury of the lung

Background This study investigated the optimal alveolar oxygen concentration and inflation pressure during ischemia that reduces lung ischemia–reperfusion injury (LIRI). Methods Male Sprague-Dawley rats ( n = 66) underwent 150 minutes of left lung ischemia by hilar clamping at an airway inflation pressure (P) of 5 or 30 cm H2 O and an oxygen (O) concentration of 0%, 30%, or 100% (P5 O0 , P5 O30 , P5 O100 , P30 O0 , P30 O30 and P30 O100 groups). Lungs preserved with 0% oxygen were inflated with 100% nitrogen. Measurements of arterial blood gas values, pulmonary compliance, histology, flow cytometry of bronchoalveolar lavage fluid were performed on day 2 postoperatively. Results Inflation with 30 cm H2 O resulted in increased partial pressure of arterial oxygen (Pa o2 ) and lung compliance, decreased diffuse alveolar damage, and less infiltration of CD4+ and CD8+ lymphocytes and major histocompatibility complex class II-positive (MHCII+ ) antigen-presenting cells (APCs) in the left lung on day 2 compared with clamping at an airway inflation pressure of 5 cm H2 O. The 100% oxygen groups demonstrated a lower Pa o2 and a decreased pulmonary compliance than 30% oxygen groups. More CD8+ lymphocytes and MHCII+ APCs were found in the P5 O100 group than in the P5 O0 and P5 O30 groups. Conclusion Alveolar inflation with a pressure of 30 cm H2 O and an oxygen concentration of 30% decreases the severity of LIRI. The protective effect is mainly due to hyperinflation and, to a lesser extent, through oxygen concentration.