To analyze the predictive efficacy of lower respiratory secretory leukocyte protease inhibitor (SLPI) on the 28-day survival of severe pneumonia (SP) patients with respiratory failure (RF) treated by non-invasive ventilation (NIV).

Eighty-two SP patients with RF treated by NIV from Shaoxing 7th People's Hospital and Shaoxing People's Hospital between April 2021 and April 2023 were divided into a death group (25 cases) and a survival group (57 cases) according to their 28-day survival. The general clinical data and SLPI levels of lower respiratory tract secretions were compared between the two groups. A logistic regression model was used to analyze the influencing factors on the 28-day survival of SP patients with RF treated by NIV, and the predictive efficacy of each influencing factor on the 28-day survival of SP patients with RF was analyzed by a receiver operating characteristic (ROC) curve.

Compared with the survival group, patients in the death group were older [62 (43, 75) years vs. 64 (52, 78) years, Z = 3.044, P = 0.003], the proportion of severe RF [26.32% (15/57) vs. 52.00% (13/25), χ² = 5.098, P = 0.024], pathogen species ≥ 2 [35.09% (20/57) vs. 60.00% (15/25), χ² = 4.408, P = 0.036] and acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) score [17 (10, 21) vs. 20 (13, 23), Z = 3.140, P = 0.002] were significantly increased, and the oxygenation index [(325 ± 60) mmHg vs. (284 ± 32) mmHg, t = 3.284, P = 0.002] and SLPI levels [(843 ± 102) μg/L vs. (735 ± 93) μg/L, t = 4.524, P < 0.001] were obviously decreased. Logistic regression model analysis showed that the age [odds ratio (OR) = 2.240, 95% confidence interval (CI) (1.340, 3.745), P = 0.002], pathogen species ≥ 2 [OR = 2.804, 95%CI (1.447, 5.434), P = 0.002] and APACHEⅡ score [OR = 2.598, 95%CI (1.268, 5.324), P = 0.009] were risk factors for 28-day survival in SP patients with RF treated by NIV, and the oxygenation index [OR = 0.582, 95%CI (0.383, 0.883), P = 0.011] and SLPI [OR = 0.507, 95%CI (0.281, 0.917), P = 0.019] were the protective factors. The ROC curve showed that the best cutoff value for SLPI to predict 28-day survival in SP patients with RF treated by NIV was 806.50 μg/L, with the area under the curve (AUC) of 0.788 [95%CI (0.684, 0.871), P < 0.001], and its AUC was much higher than that of age, pathogen species ≥ 2, APACHEⅡ score and oxygenation index (Z = 1.989, P = 0.047; Z = 2.629, P = 0.009; Z = 2.231, P = 0.026; Z = 2.438, P = 0.015).

The SLPI of lower respiratory tract secretions is a protective factor for 28-day survival in SP patients with RF treated by NIV, and is effective in predicting their survival.