Preventing ventilator-associated pneumonia via the gut-lung axis: the Shenling Baizhu San hypothesis.

Ventilator-associated pneumonia (VAP) is a common hospital-acquired infection in the intensive care unit (ICU). It is associated with high morbidity and mortality, which are often compounded by patient frailty and disease severity. Despite adherence to antibiotic treatment guidelines, mortality rates remain persistently high. Critical illness disrupts intestinal function and alters epithelial cell dynamics, specifically increasing apoptosis and decreasing proliferation, thereby compromising the homeostasis of the epithelial monolayer. This increased intestinal permeability facilitates the translocation of bacteria and microbial products. Furthermore, impaired intestinal immunity exacerbates systemic inflammation and organ dysfunction. Previous studies indicate that the early onset of severe acquired immunosuppression in ICU patients significantly increases the risk of secondary infections. The gut-lung axis, which involves bidirectional crosstalk between the gastrointestinal and respiratory systems, is closely linked to immune regulation and the progression of lung diseases. We hypothesize that Shenling Baizhu San (SLBZS), a polysaccharide-rich multi-herb formula traditionally used for gastrointestinal disorders, could reduce susceptibility to VAP by reshaping the gut microbiota, enhancing the intestinal mucosal barrier, and modulating the transition from systemic inflammation to critical illness-induced immunoparalysis (CIIP) through microbiota-derived metabolites such as short-chain fatty acids (SCFAs). Validating this hypothesis would provide a novel, integrative therapeutic strategy for managing high-risk VAP patients.