Approach to respiratory acidosis Quiz: Ace Your Exams

A 43-year-old man is admitted to the intensive care unit following an opiate overdose requiring intubation. The patient is mechanically ventilated and sedated on a propofol and fentanyl infusion. During rounds, the patient appears increasingly cyanotic. The patient has a history of alcoholism and opiate use disorder and does not take any medication daily. Temperature is 37°C (98.6°F), heart rate 115/min, blood pressure 136/68 mmHg, respiratory rate 10/min, and O₂ saturation 93% on 100% FIO₂. The patient is not over-breathing the ventilator. Bilateral breath sounds are present and cardiac examination is within normal limits. The patient has evidence of skin cyanosis. Stat blood gas results are obtained, which show pH 7.27 (reference range: 7.35-7.45) and a pCO₂ 50 mmHg (reference range: 33-45 mmHg). A chest x-ray demonstrates that the endotracheal tube is 2 cm above the carina. Which of the following should be assessed next to help determine the cause of cyanosis and respiratory acidosis in this patient?