The characterization of dyspnea matters enormously for diagnosis. Onset matters: sudden onset suggests pneumothorax, pulmonary embolism, or acute coronary syndrome. Gradual onset over days to weeks suggests heart failure exacerbation, COPD or asthma progression, or anemia. Chronic dyspnea on exertion that has been gradually worsening suggests underlying cardiopulmonary disease that deserves formal evaluation.
The most common causes of dyspnea in primary care are: asthma, COPD, heart failure, pulmonary embolism, pneumonia, anemia, anxiety and panic disorder, and deconditioning. Asthma and panic disorder can be clinically indistinguishable in an acute episode — both produce bronchospasm, air hunger, and tachycardia. Proper diagnosis requires pulmonary function testing and clinical history, not empirical treatment.
Concerning features that warrant urgent evaluation: dyspnea at rest, orthopnea (dyspnea when lying flat — classic for heart failure), paroxysmal nocturnal dyspnea (awakening at night with breathlessness), dyspnea with pleuritic chest pain (pulmonary embolism), dyspnea after prolonged immobility or recent surgery (PE), dyspnea with hemoptysis, or dyspnea with signs of systemic illness. These features significantly raise the pre-test probability of serious pathology.
The diagnostic workup begins with oxygen saturation (O2 sat <95% at rest warrants immediate evaluation), chest X-ray, ECG, and CBC and BMP. BNP or NT-proBNP screens for heart failure. D-dimer and CT pulmonary angiography evaluate for pulmonary embolism. Spirometry is essential for diagnosing obstructive or restrictive lung disease — it is underused in primary care despite its diagnostic power.