The CD4⁺/CD8⁺ ratio is independently associated with severe acute lung injury

Objective: To investigate the association between the CD4⁺/CD8⁺ T-cell ratio and severe acute lung injury (ALI). Methods: Following the 2012 Berlin Definition of severe ALI, 31 patients with severe ALI admitted to the Department of Critical Care Medicine at the First Affiliated Hospital of Chongqing Medical University from June 2022 to October 2023 were enrolled as the study subjects (severe ALI group). while 147 non-severe ALI patients served as the control group during the same period. Clinical data were collected, and the serum CD4⁺/CD8⁺ T-cell ratio were analyzed using flow cytometry. The CD4⁺/CD8⁺ T-cell ratio levels were compared between the severe and the non-severe ALI groups. Linear relationships between the CD4⁺/CD8⁺ T-cell ratio and severe ALI were established through restricted cubic spline modeling, and multivariate logistic regression was employed to analyze their association. Results: Patients with severe ALI had significantly higher APACHE II scores, SOFA scores, serum lactate levels, and CD4⁺/CD8⁺ T-cell ratios than the non-severe group, while the absolute lymphocyte count was significantly lower (all P < 0.05). The proportion of patients receiving invasive mechanical ventilation and ECMO was significantly higher in the severe group. Multivariate logistic regression showed that, in addition to the SOFA score (OR = 1.21, P = 0.015) and oxygenation mode (OR = 1.54, P = 0.045), the CD4⁺/CD8⁺ ratio was independently associated with severe ALI (OR = 1.40, P = 0.019). Restricted cubic spline analysis confirmed a linear relationship between the CD4⁺/CD8⁺ ratio and disease severity (non-linear P = 0.757). After further correction of the use of vasopressors and corticosteroids, the increase in the CD4⁺/CD8⁺ ratio increased the risk of severe lung injury by 1.45 times (OR = 1.45, 95% CI: 1.07–1.94, P _adj = 0.015). Conclusion: The CD4⁺/CD8⁺ T-cell ratio is an independent risk factor for severe ALI.