Positive end-expiratory pressure and risk of postoperative pulmonary complications in patients living at high altitudes and undergoing surgery at low altitudes: a single-centre, retrospective observational study in China.

OBJECTIVES: To examine whether a high positive end-expiratory pressure (PEEP ≥5 cmH2O) has a protective effect on the risk of postoperative pulmonary complications (PPCs) in a cohort of patients living at high altitudes and undergoing general anaesthesia. DESIGN: Retrospective, observational study. SETTING: A tertiary hospital in China. PARTICIPANTS: Adult Tibetan patients living at high altitudes (≥3000 m) and who went to the low-altitude plain to undergo non-cardiothoracic surgery under general anaesthesia, from January 2018 to April 2020. MEASUREMENTS: This study included 1905 patients who were divided according to the application of an intraoperative PEEP: low PEEP (<5 cmH2O, including 0 cmH2O) or high PEEP (≥5 cmH2O). The primary outcome was a composite of PPCs within the first 7 postoperative days. The secondary outcomes included reintubation and unplanned intensive care unit (ICU) admission within the first 7 postoperative days and total hospital stays (day). RESULTS: The study included 1032 patients in the low PEEP group and 873 in the high PEEP group. There were no differences in the incidence of PPCs between the high and low PEEP groups (relative risk (RR) 0.913; 95% CI 0.716 to 1.165; p=0.465). After propensity score matching, 643 patients remained in each group, and the incidence of PPCs in the low PEEP group (18.0%) was higher than in the high PEEP group (13.7%; RR 0.720; 95% CI 0.533 to 0.974; p=0.033). There were no differences in the incidence of reintubation, unplanned ICU admission or hospital stays. The risk factors of PPCs derived from multiple regression showed that the application of >5 cmH2O PEEP during intraoperative mechanical ventilation was associated with a significantly lower risk of PPCs in patients from a high altitude (OR=0.725, 95% CI 0.530 to 0.992; p=0.044). CONCLUSIONS: The application of PEEP ≥5 cmH2O during intraoperative mechanical ventilation in patients living at high altitudes and undergoing surgery at low altitudes may be associated with a lower risk of PPCs. Prospective longitudinal studies are needed to further investigate perioperative lung protection ventilation strategies for patients from high altitudes. TRIAL REGISTRATION NUMBER: Chinese Clinical Trial Registry (ChiCTR2100044260).

[In vivo effect of recombined IL-15/Fc fusion protein on EAU].

OBJECTIVE: To test the effect of recombined IL-15/Fc on experimental autoimmune uveitis (EAU) in mice. METHODS: EAU were induced in C57 mice by transferring activated T cells specific to the interphotoreceptor-binding protein (IRBP) 1-20 peptide. The mice were then treated with recombine IL-15/Fc fusion protein or IgG as controls. The severity of EAU were graded on a scale of 0 to 4 with half-point increment based on the type, number, and size of the lesions detected by funduscopic and HE staining. The IRBP1-20 sensitive CD8+T cells were isolated from the IRBP1-20 immune mice with auto-MACS. The in vitro effect of IL-15/Fc fusion protein on the proliferation, differentiation, expansion and production of inflammatory cytokines of the purified IRBP1-20 sensitive CD8+T cells were analyzed with 3HTdR, FACS and ELISA. RESULTS: IL-15/Fc fusion protein inhibited the activation, proliferation, expansion and production of inflammatory cytokines of the IRBP1-20 specific CD8+T cells, down regulated CD44(high)CD62L(low) effect and CD8+ CD62L(low) activated T cell subsets, and consequently decreased the severity of EAU. CONCLUSION: IL-15/Fc fusion proteins decrease the severity of EAU through inhibiting the proliferation, expansion, differentiation and production of inflammatory cytokines of CD8+ T cells.