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 H(2)O and an oxygen (O) concentration of 0%, 30%, or 100% (P(5)O(0), P(5)O(30), P(5)O(100), P(30)O(0), P(30)O(30) and P(30)O(100) 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 H(2)O resulted in increased partial pressure of arterial oxygen (Pao(2)) 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 H(2)O. The 100% oxygen groups demonstrated a lower Pao(2) and a decreased pulmonary compliance than 30% oxygen groups. More CD8(+) lymphocytes and MHCII(+) APCs were found in the P(5)O(100) group than in the P(5)O(0) and P(5)O(30) groups. CONCLUSION: Alveolar inflation with a pressure of 30 cm H(2)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.
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 H(2)O and an oxygen (O) concentration of 0%, 30%, or 100% (P(5)O(0), P(5)O(30), P(5)O(100), P(30)O(0), P(30)O(30) and P(30)O(100) 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 H(2)O resulted in increased partial pressure of arterial oxygen (Pao(2)) 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 H(2)O. The 100% oxygen groups demonstrated a lower Pao(2) and a decreased pulmonary compliance than 30% oxygen groups. More CD8(+) lymphocytes and MHCII(+) APCs were found in the P(5)O(100) group than in the P(5)O(0) and P(5)O(30) groups. CONCLUSION:Alveolar inflation with a pressure of 30 cm H(2)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.