Respiratorymiddle twist
A 71-year-old man with severe chronic obstructive pulmonary disease presents with three days of increasing breathlessness and green sputum. On arrival he is drowsy but rousable, with a respiratory rate of 30/min. Arterial blood gas on air: pH 7.31, PaCO₂ 62 mmHg, PaO₂ 50 mmHg, bicarbonate 31 mmol/L. He is given oxygen via a 28% Venturi mask, nebulised salbutamol and ipratropium, oral prednisolone and oral amoxicillin. One hour later he remains drowsy, his respiratory rate is 32/min, oxygen saturation is 90%, and a repeat gas shows pH 7.26, PaCO₂ 74 mmHg, PaO₂ 62 mmHg. He can still follow commands and clear his own secretions.
Which one of the following is the most appropriate next step in management?