A 28-week preterm infant on conventional mechanical ventilation has rising PaCO2 and decreasing tidal volumes on recent blood gases. Outline your step-by-step assessment and the immediate ventilator adjustments or interventions you would consider, including how you would rule out equipment versus patient causes.

First I’d do a rapid bedside assessment within 2–3 minutes: check work of breathing, chest rise, SpO2, heart rate, and auscultate for breath sounds or pneumothorax. I’d note numbers: e.g. PaCO2 rising from 50 to 70 mmHg and Vt dropping from 5 to 3 ml/kg. Simultaneously I’d check the ventilator alarm log and displayed delivered Vt and leak percentage (leak >20% suggests circuit/ETT leak). I’d suction the ETT for secretions and verify tube depth/position. To separate equipment vs patient I’d briefly disconnect to manual ventilation (T-piece) and observe compliance and achieved Vt; if manual breaths restore Vt and CO2, suspect ventilator/circuit problem. If patient-related, options: increase PIP by 2–4 cmH2O or raise target Vt by 1–2 ml/kg (aim 4–6 ml/kg), or increase rate slightly, treat bronchospasm or secretions, and repeat an ABG in 30–60 minutes. I’d call the neonatal consultant and respiratory therapist within 5–10 minutes and get a chest x-ray if tube position or pneumothorax is suspected.