Objective:To investigate the influence of high frequency oscillatory ventilation combined with ulinastatin on serum inflammatory factors, blood gas indexes and endothelial function in patients with respiratory distress after smoke inhalation lung injury.Methods:Sixty-two patients with acute respiratory distress syndrome induced by smoke inhalation lung injury from January 2016 to January 2019 in the 910th Hospital of the PLA Joint Service Support Unit were enrolled.With a prospective cohort study, the patients were divided into control group (31 cases) and observation group (31 cases) according to the random number table.The control group were treated with high-frequency oscillatory ventilation.The observation group was given intravenous ulinastatin treatment on the basis of the control group, 3×105 U/time, dissolved in 50 ml of normal saline, once every 8 hours.Acute physiology and chronic health evaluation (APACHE) Ⅱ score was performed before intervention and 48 hours after intervention.Serum interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-α(TNF-α), nitric oxide, endothelin-1 were detected by enzyme-linked immunosorbent assay. Arterial blood oxygen partial pressure (PaO 2), arterial partial pressure of carbon dioxide (PaCO 2), oxygenation index were measured by blood gas analyzer. The Extra-vascular lung water index (EVLWI), pulmonary vascular permeability index (PVPI) were recorded by pulse indicator continuous cardiac output monitoring.The occurrence of adverse reactions were recorded. Results:The IL-6 ((66.8±15.2) ng/L), IL-8 ((70.3±10.4) ng/L, TNF-α ((24.6±3.5) ng/L) of the observation group after treatment 48 hours were lower than before treatment ((89.3±21.0) ng/L, (288.4±33.5) ng/L, (101.3±9.0) ng/L), the difference was statistically significant(t value was 5.704, 21.215, 30.281, repectively, all P<0.05), and the observation group were significantly lower than the control group((90.4±22.4) ng/L, (162.4±16.6) ng/L, (62.3±4.4) ng/L), the difference was statistically significant(t value was 4.906, 12.324, 19.252, repectively, all P<0.05). After 48 h of intervention in the control group and the observation group after 48 h of intervention, the oxygenation index ((208.5±55.4) mmHg and (315.3±49.8) mmHg), PaO 2 ((101.6±12.4) mmHg and (118.8±10.3) mmHg) of the control group and the observation group after 48 hours of intervention were significantly higher than before intervention((114.8±24.6) mmHg and(112.3±20.5) mmHg, (70.6±10.5) mmHg and(70.3±10.2) mmHg)(t value was 15.663 and 22.387, 11.216 and 16.214, repectively, all P<0.05, the PaCO 2 ((44.7±7.4) mmHg and (39.3±4.8) mmHg), EVLWI ((12.42±3.66) ml/kg and (9.70±2.33) ml/kg), PVPI (2.34±0.48 and 1.82±0.35) significantly lower than before intervention((47.8±5.6) mmHg and(48.3±6.5) mmHg, (16.58±4.05) ml/kg and (16.60±4.10) ml/kg, 2.86±0.55 and 2.90±0.53), ( t value was 3.655 and 7.372, 3.516 and 6.521, 3.571 and 8.024, repectively, all P<0.05), the oxygenation index , PaO 2 in the observation group after intervention were significantly higher than those in the control group, P<0.05, while PaCO 2, EVLWI and PVPI in the observation group were significantly lower than the control group, t value was 7.106, 4.213, 4.037, 7.122, 3.976, repectively, all P<0.05.The nitric oxide((76.65±30.25) μmol/L and (54.15±20.36) μmol/L), endothelin ((58.32±20.26) ng/L and (42.23±21.15) ng/L), APACHE Ⅱ score ((10.05±2.84) points and (7.14±2.74) points) of the control group and the observation group after 48 h intervention were significantly lower than before intervention ((90.30±33.33) μmol/L and(89.62±34.64) μmol/L, (71.64±28.35)ng/L and (70.36±26.56)ng/L, (23.46±4.13)points and(23.60±4.20)points), ( t value was 3.761 and 8.063, 4.031 and 7.376, 6.193 and 11.531, repectively, all P<0.05). The nitric oxide, The endothelin and APACHE Ⅱ scores in observation group after 48 h intervention were significantly lower than those of the control group ( t value was 3.759, 3.515, 3.715, repectively, all P<0.05). There were no adverse drug reactions occurred during the treatment in both groups. Conclusion:High frequency oscillatory ventilation combined with ulinastatin in the treatment of respiratory distress after smoke inhalation lung injury can inhibit the excessive release of inflammatory mediators and improve vascular endothelial function, thereby reducing capillary leakage, reducing EVLWI and increasing oxygenation index.