A COPD patient on 3 L oxygen becomes increasingly somnolent. ABG: pH 7.30, PaCO2 72, HCO₃ 34. What is the priority action?

The arterial blood gas values presented — pH 7.30, PaCO2 72 mmHg, and HCO3 34 mEq/L — indicate acute-on-chronic respiratory acidosis with partial metabolic compensation. The elevated bicarbonate suggests a pre-existing chronic hypercapnia state, and the falling pH combined with a PaCO2 of 72 confirms acute decompensation. The patient's somnolence signals CO2 narcosis, indicating the patient can no longer protect or adequately ventilate his airway. The priority action is to prepare for ventilatory support — whether non-invasive positive pressure ventilation (BiPAP) or intubation — because the patient is at imminent risk of respiratory arrest. Increasing oxygen to 6 L/min is dangerous in a COPD patient who relies on hypoxic drive; high-flow oxygen can worsen hypercapnia and hasten respiratory failure. Morphine further suppresses respiratory drive and is contraindicated. Encouraging deep breathing is insufficient for a patient who is already somnolent and in acute respiratory failure — a passive intervention cannot compensate for the level of decompensation indicated by these values. Only ventilatory support addresses the underlying inability to ventilate adequately.