BACKGROUND:Since respiratory dysfunction is the main cause of death in patients with severe acute pancreatitis (SAP),elucidating the critical period of acute pancreatitis-associated lung injury(APALI)is of important clinical value. This study aimed to define the risk period of APALI by a series of studies including a dynamic analysis of total water content,ultrastructure and number of typeⅡalveolar epithelial cells,and reactive oxygen metabolites(ROMs)of lung tissue in a mouse model of SAP,and a clinical analysis of APALI patients. METHODS:ICR mice were selected to establish a SAP model.They were given 7 intraperitoneal injections of cerulein(50μg/kg body weight)at hourly intervals,followed by an intraperitoneal injection of lipopolysaccharide(15 mg/kg body weight).The total water content,ultrastructure, and number of typeⅡalveolar epithelial cells,and ROMs of lung tissue were assessed before(0 hour)and after the establishment of SAP model(6 hours,12 hours,1 day,4 days,and 7 days).In addition,we analyzed the data from 215 patients with APALI(PaO2<60 mmHg)treated at our hospital between January 1998 and December 2006. Statistical analyses were made using the F test.P values less than 0.05 were regarded as statistically significant. RESULTS:The total water content and ultrastructure of typeⅡalveolar epithelial cells(mitochondria and lamellar bodies)of the lung in the SAP mice were significantly altered at 12 hours after the establishment of SAP model,and reached a maximum at 1 to 4 days.The number of typeⅡalveolar epithelial cells and ROMs increased maximally at 1 day after the establishment of the model.Furthermore,clinical results showed that lung injury occurred at a mean of 3.1435±1.0199 days in patients with SAP.These clinical data were almost consistent with the results of the SAP model.CONCLUSION:The risk period for APALI is between the first and fourth day during the course of SAP. BACKGROUND: Since respiratory dysfunction is the main cause of of death in patients with severe acute pancreatitis (SAP), elucidating the critical period of anapry pancreatitis-associated lung injury (APALI) is of important clinical value. This study aimed to define the risk period of APALI by a series of studies including a dynamic analysis of total water content, ultrastructure and number of type II alveolar epithelial cells, and reactive oxygen metabolites (ROMs) of lung tissue in a mouse model of SAP, and a clinical analysis of APALI patients. METHODS: ICR mice were selected to establish a SAP model. They were given 7 intraperitoneal injections of cerulein (50 μg / kg body weight) at hourly intervals, followed by an intraperitoneal injection of lipopolysaccharide (15 mg / kg body weight). The total water content, ultrastructure, and number of type IIalveolar epithelial cells, and ROMs of lung tissue were assessed before (0 hour) and after the establishment of SAP model (6 hours, 12 hours, 1 day, 4 days, and 7 days) .In addition, we analyzed the data from 215 patients with APALI (PaO 2 <60 mmHg) treated at our hospital between January 1998 and December 2006. Statistical analyzes were made using the F test. P values ​​less than 0.05 were treated as statistically significant. RESULTS: The total water content and ultrastructure of type II alveolar epithelial cells (mitochondria and lamellar bodies) of the lung in the SAP mice were significantly altered at 12 hours after the establishment of SAP model, and reached a maximum at 1 to 4 days. Number of type II alveolar epithelial cells and ROMs increased maximally at 1 day after the establishment of the model. Stillrther, clinical results showed that the disease in at law a mean 3.1435 ± 1.0199 days in patients with SAP. The clinical data were almost consistent with the results of the SAP model. CONCLUSION: The risk period for APALI is between the first and fourth day during the course of SAP.