Objective To explore the effect of airway humidification on lung injury as a result of mechanical ventilation with different tidal volume(VT). Methods Twenty-four male Japanese white rabbits were randomly divided into four groups:low VT with airway humidification group,high VT with airway humidification group,low VT and high VT group without humidification,with 6 rabbits in each group. Mechanical ventilation was started after intubation and lasted for 6 hours. Low VT denoted 8 mL/kg,while high VT was 16 mL/kg,fraction of inspired oxygen (FiO2)denoted 0.40,positive end-expiratory pressure(PEEP)was 0. Temperature at Y piece of circuit in airway humidification groups was monitored and controlled at 40℃. Arterial blood gas analysis,including pH value,arterial partial pressure of oxygen(PaO2),arterial partial pressure of carbon dioxide(PaCO2),lung mechanics indexes, including peak airway pressure(Ppeak)and airway resistance(Raw),and lung compliance was measured at 0,2,4, 6 hours of mechanical ventilation. The levels of tumor necrosis factor-α(TNF-α)and interleukin-8(IL-8)in plasma and bronchoalveolar lavage fluid(BALF)were determined by enzyme linked immunosorbent assay(ELISA). The animals were sacrificed at the end of mechanical ventilation. The wet to dry(W/D)ratio of lung tissues was calculated. Histopathologic changes in the lung tissueies were observed with microscope,and lung injury score was calculated. Scanning and transmission electron microscopies were used to examine the integrity of the airway cilia and the tracheal epithelium. Results Compared with low VT group,pH value in high VT group was significantly increased,PaCO2 was significantly lowered,and no difference in PaO2 was found. Ppeak,Raw,and lung compliance were significantly increased during mechanical ventilation. There were no significant differences in blood gas analysis and lung mechanics indexes between low VT with airway humidification group and low VT group. Compared with high VT group,PaCO2 in high VT with airway humidification group was significantly decreased,Ppeak raised obviously,and no difference in pH value,PaO2,Raw and pulmonary compliance was found. Compared with low VT with airway humidification group,no difference in blood gas analysis(PaCO2,mmHg,1 mmHg=0.133 kPa)was found,but Ppeak(cmH2O,1 cmH2O=0.098 kPa),Raw(cmH2O),and lung compliance(mL/cmH2O)were increased significantly in high VT with airway humidification group(PaCO2 at 2 hours:27.96±4.64 vs. 36.08±2.11,4 hours:28.62±2.93 vs. 34.55±5.50, 6 hours:29.33±2.14 vs. 35.01±5.53;Ppeak at 0 hour:14.34±1.97 vs. 8.84±1.32,2 hours:17.33±0.52 vs. 11.17±2.14,4 hours:17.83±0.98 vs. 12.67±2.06,6 hours:18.67±1.22 vs. 13.50±2.16;Raw at 0 hour:37.36±5.14 vs. 27.05±2.93,2 hours:43.94±6.58 vs. 31.95±3.56,4 hours:48.04±6.07 vs. 35.24±3.50, 6 hours:50.33±6.34 vs. 36.66±3.64;pulmonary compliance at 6 hours:2.28±0.18 vs. 1.86±0.37,all P<0.05). The lung W/D ratio in high VT group was significantly higher than that of the low VT group(6.17±2.14 vs. 3.50±1.52, P<0.05). W/D in high VT with airway humidification group was higher than that of low VT with airway humidification group but without statistically significant difference(5.17±2.14 vs. 3.00±1.10,P>0.05). Microscopic observation showed that cilia were partially detached,adhered and sparse in low VT group,while cilia in high VT group showed serious detachment and lodging. Remaining cilia were sparse,with lodging,and cellular structure was damaged. Lung tissue pathological injury score in the high VT group was significantly higher than that of low VT group(6.17±2.14 vs. 3.50±1.52,P<0.05). Cilia density and cellularity were normal in low VT with airway humidification group,and no difference in lung tissue pathological injury score was found compared with low VT group(3.00±1.10 vs. 3.50±1.52, P>0.05). Cilia were severely detached,adhered and lodging,and cellularity were not obvious in high VT with airway humidification group,and lung tissue pathological injury score was elevated significantly than that of the low VT with airway humidification group but without statistically significant difference(5.17±2.14 vs. 3.00±1.10,P>0.05). TNF-α and IL-8 concentrations showed no change in plasma and BALF in all groups during ventilation,and no significant difference was found among the groups. Conclusions Airway humidification can alleviate pathological lung injury,damage of cilia and cellular structure in trachea caused by mechanical ventilation with low and high VT. High VT with humidification can result in serious pulmonary edema.

Objective: To investigate the serum angiopoietin-Ⅱ (Ang Ⅱ) levels in acute pancreatitis (AP) patients and the relationship between AngⅡ levels and the disease severity of AP based on the new Atlanta classification criteria. Methods: Seventy-seven patients with AP who were treated in the Affiliated Baiyun Hospital of Guizhou Medical University were included in this prospective study. According to the revised Atlanta classification, the modified Mashall scoring system was used to divided patients into AP with the persistent organ failure(POF) group and without POF group, and the CECT was used to divided patients into AP with pancreatic necrosis(PN) group and without PN group. The levels of AP 72 h after admission of two groups were compared with t test, and Spearman analysis was used to analyze the correlation between common severity indicators and Ang Ⅱ. The receiver operating characteristic (ROC) was performed to analyze the area under curve(AUC), sensitivity and specificity of Ang Ⅱ in predicting POF and PN. Results: According to the modified Mashall scoring system, there were 18 patients (23.38%) in POF group and 59 patients (76.62%) in without POF group. According to CECT, 22 patients (28.57%)were in PN group and 55 patients(71.43%) in without PN group. The Ang Ⅱ of the POF and PN groups was significantly higher than those without POF and PN groups (P=0.001, 0.011) on day 1 on admission. The cut-off value was 126.44 μg/L, and the AUC, sensitivity and specificity for predicting POF were 0.739, 83.3% and 68.4%, which was significantly better than that of traditional predictive indicators, such as C-reaction protein (CRP), procalcitonin (PCT), blood urea nitrogen (BUN), bedside index for severity in AP (BISAP) score and Ranson score. When the cut-off value was 130.90 μg/L, the AUC, sensitivity and specificity for predicting PN were 0.703, 77.3% and 73.6%, respectively, which was significantly better than that of all traditional single indicator. The predicted value was less than PCT and CRP 2 or 3 day after admission. In addition, the Ang Ⅱlevel 1 day after admission was closely related to the Ranson score, BISAP score, and PCT level which was commonly used indicators of AP severity. Conclusions Under the new Atlanta classification criteria, Ang Ⅱ is superior to the traditional predictive indicators commonly used for predicting POF, and is a better single biochemical indicator for predicting PN in clinic.