Acute respiratory failure, part 2: Differential diagnosis and management

The chest radiograph plays an essential role in the evaluation of acute respiratory failure. The presence of patchy or diffuse infiltrates may suggest pneumonia, atelectasis, or pulmonary edema, while the absence of diffuse infiltrates may be consistent with an exacerbation of chronic obstructive pulmonary disease, pulmonary embolism, or microatelectasis. When evaluating a patient in whom pneumonia is suspected, keep in mind that the pattern of diffuse pulmonary infiltrates, severe hypoxemia, and marked dyspnea is nonspecific and may, for example, be caused by left ventricular failure. Management generally consists of supportive therapy, supplemental oxygen, and correction of the underlying primary pathology. If a patient requires a very high fraction of inspired oxygen (FIO₂), consider implementing either noninvasive ventilation, with continuous positive airway pressure or bilevel positive airway pressure, or mechanical ventilation. This will lower the FIO₂ and reduce the risks of atelectasis and oxygen toxicity.