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Chapter 9: Hypercarbic Respiratory Failure

A 63-year-old man is brought to the emergency department (ED) with a 3-day history of increasing dyspnea and increasing sputum production. He is a former cigarette smoker, 2 packs per day for 40 years, and quit 5 years ago. At baseline, he is short of breath on climbing 1 flight of stairs, and uses supplemental oxygen with sleep at 2 L/min. Medications include a long-acting anticholinergic drug and occasional use of a short acting β agonist. He has been given 2 L/min nasal oxygen in the ambulance.

On physical exam, he is lethargic but arousable and able to follow simple commands. Respiratory rate is 16 breaths/min. Chest exam reveals increased anterioposterior (AP) diameter, low diaphragms, very decreased breath sounds, and no wheezing. His chest x-ray shows hyperinflation but no obvious infiltrate, and his lateral chest x-ray suggests right ventricular enlargement. Arterial blood gas shows pH of 7.32, PCO2 of 69 mmHg, and PO2 of 44 mmHg. Which of the following is your first step?

A. Intubation and mechanical ventilation

B. Noninvasive ventilation

C. Supplemental oxygen using a venturi mask

D. Computed tomography (CT) scan of the chest with CT angiogram

C. Supplemental oxygen using a venturi mask

Neither intubation (choice A) nor noninvasive ventilation (choice B) is immediately mandatory. The patient is lethargic but responsive, and his arterial blood gas is consistent with mostly chronic hypoventilation. His pH is relatively normal despite significant hypercapnia. A CT scan of the chest looking for pulmonary embolism may often be useful, but would not be part of the initial orders (choice D).

Oxygen administration is always appropriate for a patient who is severely hypoxemic. Although this can worsen hypercarbia, efforts need to be made to maintain oxygen saturation above about 92%, or a PaO2 above 55 mmHg. It is thought that the mechanism of hypercarbia with oxygen therapy is actually worsening ventilation perfusion mismatch rather than reduction in ventilatory drive. If hypercapnia worsens or the patient’s mental status worsens, ventilation may be required.

A 63-year-old man is brought to the emergency department (ED) with a 3-day history of increasing dyspnea and increasing sputum production. He is a former cigarette smoker, 2 packs per day for 40 years, and quit 5 years ago. At baseline, he is short of breath on climbing 1 flight of stairs, and uses supplemental oxygen with sleep at 2 L/min. Medications include a long-acting anticholinergic drug and occasional use of a short acting β agonist. He has been given 2 L/min nasal oxygen in the ambulance.

On physical exam, he is lethargic ...

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