Ventilator-associated pneumonia (VAP) is a common and serious infection in critically ill patients receiving mechanical ventilation in intensive care units (ICUs). One of the key diagnostic criteria for VAP is the presence of a new or progressive infiltrate on chest X-ray; however, interpretation of bedside chest radiographs is often challenging and subject to inter-observer variability.

This retrospective observational study aims to evaluate the role of artificial intelligence (AI) in the assessment of chest X-rays in patients with VAP. Chest radiographs obtained before and at the time of VAP diagnosis will be analyzed using a deep learning-based AI tool (Chester the AI Radiology Assistant), and changes in "infiltration" and "pneumonia" probability scores will be assessed.

AI-based findings will be compared with clinical decisions and independent radiologist evaluations regarding the presence of new infiltrates. The study aims to determine the level of agreement between these approaches and to explore whether AI-based analysis can support a more objective and standardized interpretation of chest radiographs in the diagnosis of VAP.

Inclusion Criteria:

• Adult patients (≥18 years)
• Admission to the anesthesia intensive care unit
• Requirement of invasive mechanical ventilation for at least 48 hours
• Clinical diagnosis of ventilator-associated pneumonia (VAP) based on institutional criteria
• Availability of at least one chest X-ray prior to VAP diagnosis and one chest X-ray at the time of diagnosis
• Availability of digital chest radiographs in the PACS system suitable for analysis

Exclusion Criteria:

• Age <18 years
• Absence of accessible digital chest radiographs
• Chest radiographs with severe technical limitations preventing evaluation
• Chest radiographs that could not be processed by the AI system (no score generated)
• Presence of extensive pre-existing infiltrative lung disease preventing reliable assessment of new infiltrates
• Missing key clinical data (e.g., VAP diagnosis date, mechanical ventilation duration)

The study population consists of adult patients admitted to a tertiary care anesthesia intensive care unit who required invasive mechanical ventilation and received a clinical diagnosis of ventilator-associated pneumonia (VAP). Patients were identified retrospectively through hospital electronic medical records and infection control committee databases. This cohort represents a critically ill ICU population with high disease severity and diverse comorbid conditions.