Common lung conditions: acute dyspnea.

Dyspnea is a subjective experience of breathing discomfort; patients experience qualitatively distinct sensations that vary in intensity. Acute dyspnea might be secondary to an acute problem, or it might be an exacerbation of an existing disease (eg, asthma, chronic obstructive pulmonary disease, heart failure). It also accompanies a variety of illnesses at the end of life. New information has changed differentiation between respiratory and cardiovascular etiologies of acute dyspnea, as well as rapid diagnosis of pulmonary embolism. Management of acute dyspnea from hypercapnic failure also has changed. Patients presenting with dyspnea most commonly have underlying cardiovascular and/or respiratory etiologies, and differentiating between the two can be challenging. B-type natriuretic peptide (BNP) and N-terminal proB-type natriuretic peptide (NT-proBNP) are elevated when ventricular wall tension increases (eg, during a heart failure exacerbation). BNP and NT-proBNP are most useful for identifying patients with dyspnea who do not have heart failure. A BNP level less than 50 pg/mL has a negative predictive value of 96%, effectively ruling out heart failure; a serum BNP level less than 100 pg/mL has a negative likelihood ratio of 0.11. Patients with pulmonary embolism often present with dyspnea, and this condition needs to be diagnosed and managed expeditiously. When pulmonary embolism is suspected, use a clinical decision rule (eg, the Wells rule, the Geneva rule) to establish the probability of this condition. For patients with a low probability, obtain a D-dimer test; if the D-dimer result is negative, monitor the patient. A positive D-dimer result requires further investigation. For patients with intermediate or high probability, obtain computed tomography pulmonary angiography for a definitive diagnosis. Patients who have dyspnea from a chronic obstructive pulmonary disease exacerbation can experience hypercapnic failure. As an adjunct to usual medical treatment, noninvasive positive pressure ventilation decreases the need for mechanical ventilation and is particularly useful in patients who have chosen not to be resuscitated with intubation.