OBJECTIVE  To explore the correlation between early Th1/Th2 immune balance and pulmonary infection in patients with acute respiratory distress syndrome （ARDS） caused by multiple injuries.

METHODS  A total of 90 patients with ARDS caused by multiple injuries, who were treated at the Fifth Clinical Medical School of Henan University of Chinese Medicine from Jan. 2022 to Jun. 2024, were selected as the study subjects. According to the presence of pulmonary infection, they were divided into a pulmonary infection group （n=42） and a non-infection group （n=48）. The Th1/Th2 immune balance status and inflammatory factors interleukin （IL）-1β, IL-2, IL-4, IL-10, interferon γ （IFN-γ） were detected in both groups. A Joint model was constructed to analyze the changes in Th1/Th2 immune balance status and pulmonary infection, and sensitivity analysis of the study results was conducted with the E-value method. The restricted cubic spline regression method was applied to analyze the dose-response relationship between the decline rate of Th1/Th2 immune balance-related inflammatory factor levels and pulmonary infection. A risk prediction model was constructed, and the predictive value of Th1/Th2 immune balance-related inflammatory factors for pulmonary infection was evaluated with the ROC curve.

RESULTS  There were statistically significant differences in the levels of Th1/Th2 immune balance-related inflammatory factors between the pulmonary infection group and the non-infection group after surgery （P＜0.05）. The Th1/Th2 immune balance status changed over time, with significant differences between the two groups, and the immune balance status varied at different times （P＜0.05）. For each longitudinal decrease of one unit in IFN-γ levels, the risk of pulmonary infection increased by 0.836 times. For each longitudinal increase of one unit in IL-1β, IL-2, IL-4 and IL-10 levels, the risk of pulmonary infection increased by 0.624, 0.541, 0.715 and 0.764 times, respectively （P＜0.05）. There was a nonlinear relationship between the decrease in IFN-γ levels, the increase in IL-1β, IL-2, IL-4 and IL-10 levels, and pulmonary infection in patients with ARDS caused by multiple injuries （nonlinear test P＜0.05）. The combined predictive model of the levels of IL-1β, IL-2, IL-4, IL-10 and IFN-γ had a high predictive value for the risk of pulmonary infection （AUC=0.961）.

CONCLUSION When the level of IFN-γ decreases and the levels of IL-1β, IL-2, IL-4 and IL-10 increase in patients with ARDS caused by multiple injuries, the risk of pulmonary infection increases.