Sepsis is a systemic inflammatory response syndrome triggered by infection, and it is a common critical illness in clinical practice, often leading to multiple organ dysfunction. Among these, acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are among the most severe complications. The mortality rate of sepsis-related lung injury is extremely high, reaching 30% - 50%. The existing treatment methods are unable to effectively reduce the high mortality rate of sepsis-related lung injury, and there are no specific treatment measures targeting lung injury itself. Dysbiosis of the intestinal flora plays an important role in the occurrence and development of sepsis-related lung injury. Fecal microbiota transplantation (FMT), as an effective means of regulating the intestinal flora, has shown certain therapeutic potential in some clinical studies. However, current research on FMT for treating sepsis-related lung injury is still in its infancy, and its mechanism is not yet fully clear. The clinical efficacy and safety also lack high-quality evidence support. Therefore, conducting this project's research will provide theoretical basis for targeted microecological treatment of sepsis-related lung injury; establishing a new strategy of combined microbiota transplantation technology for treating patients with sepsis ALI, and providing new ideas and methods for clinical treatment.

Although certain research progress has been made in the pathogenesis and treatment of sepsis-related lung injury, many unresolved issues still exist. The existing treatment methods are unable to effectively reduce the high mortality rate of sepsis-related lung injury, and there are no specific treatment measures targeting the lung injury itself. Dysbiosis of the intestinal flora plays an important role in the occurrence and development of sepsis-related lung injury, and FMT, as an effective means of regulating the intestinal flora, has shown certain therapeutic potential in animal experiments and some clinical studies. However, current research on FMT for treating sepsis-related lung injury is still in its infancy, and its mechanism is not yet fully clear, and there is a lack of high-quality evidence to support its clinical efficacy and safety. Therefore, conducting this project's research is of great necessity. Through this project's research, it is expected to analyze the microbial-metabolism-immune regulatory network in the gut-lung axis, providing theoretical basis for targeted microecological treatment of sepsis-related lung injury; establish a new strategy for treating sepsis ALI patients using combined microbiota transplantation technology, and provide new ideas and methods for clinical treatment.

Inclusion Criteria:

• Age ≥ 18 years;
• Clear or suspected infection + SOFA score ≥ 2 points, and PaO₂/FiO₂ ≤ 300 mmHg;
• Capable of taking in nutrients (able to eat independently or receive enteral nutrition);
• Voluntarily participate in this trial and sign the informed consent form.

Exclusion Criteria:

• Indications for exclusion from FMT (Fecal Microbiota Transplantation) include massive gastrointestinal bleeding, intestinal obstruction, organic intestinal disorders, and severe damage to intestinal mucosa;
• Individuals with severe immune deficiencies, such as those with AIDS, leukemia, and those using immunosuppressive drugs;
• Pregnant women and lactating women;
• Those who cannot undergo nasal-intestinal catheterization or other transplantation methods;
• Patients who cannot cooperate to complete the study; Other situations where the researchers determine that a patient is not suitable for participating in the clinical trial.