A63-year-old man with chronic bronchitis presents to the emergency department with worsening shortness of breath. He is dyspneic, his respiratory rate is 32/min, and he has peripheral cyanosis. A chest examination reveals increased anteroposterior diameter and scattered rhonchi, but no wheezes or evidence of consolidation. His ABG determinations on room air are pH of 7.36, arterial oxygen pressure (PaO2) of 40 mmHg, and PaCO2 of 47 mmHg. He is given oxygen by face mask while awaiting a CXR. His respiratory rate falls to 12/min,but his ABGs on oxygen are now pH of 7.31, PaO2 of 62 mmHg, and PaCO2 of 58 mmHg. Which of the following is the most appropriate next step in the management of this patient?
- repeat the ABG
- initiate mechanical ventilation
- obtain a CXR
- check the oxygen delivery system
- decrease the fraction of inspired oxygen (FIO2)
Answer(s): E
Explanation:
Patients with advanced chronic obstructive pulmonary disease (COPD) are at risk for development of acute respiratory failure. Common precipitants are infections, increased secretions, and superimposed bronchospasm. Oxygen therapy is effective in reversing the hypoxemia associated with respiratory failure.
Arisk of such therapy peculiar to patients with
COPD is worsening hypercapnia. Affected patients are thought to have lost their respiratory center's sensitivity to hypercapnia, so that their primary stimulus to breathe is hypoxemia. When the hypoxemia is corrected, they may lose their stimulus to breathe and develop carbon dioxide narcosis with worsening acidosis, confusion, stupor, and eventually coma. Because of this, the usual approach is to begin with a low fraction of inspired oxygen (FIO2) and increase gradually. Serial ABGs are obtained to ensure that as PaO2 improves,