A synopsis of AFP's " Causes and Evaluation of Chronic Dyspnea"

Causes and Evaluation of Chronic Dyspnea
STEVEN A. WAHLS, MD, Oregon Health & Science University, Portland, Oregon
Am Fam Physician. 2012 Jul 15;86(2):173-180.
http://www.aafp.org/afp/2012/0715/p173.pdf

      Breathing is regulated by chemoreceptors in the brain and vascular system, mechanoreceptors in the chest wall and diaphragm, and vagal receptors in the pulmonary system. Chronic dyspnea is a shortness of breath lasting at least one month. It is subjective and varying in intensity. Causes of dyspnea include asthma, congestive heart failure, myocardial ischemia, COPD, interstitial lung disease, pneumonia, and psychogenic disorders. 
     Clinical presentation alone is sufficient information to allow the clinician to make a correct diagnosis in more than half of the cases. Patients with asthma present with chest tightness. Those with heart failure may have shortness of breath on exertion, a sensation of suffocation, or "air hunger".  Patients having sputum production with cough and dyspnea should may need spirometry.  A questionnaire will ask how often is mucus produced with cough, how often are chest sounds audible, how often is there dypnea on exertion, age, and smoking history. Patients with intermittent dyspnea may be suffering from reflux or aspiration. Fever may be associated infection, inflammation, or malignancy.
     Physical exam can give other clues to support the diagnosis. Paradoxical pulse may suggest asthma or COPD. JVD may suggest CHF. A pleural rub may indicate effusion. Murmurs may indicate an ASD or a valve problem. A chest X ray and ECG can be considered if there are signs of heart failure. Spirometry can be performed to diagnose a restrictive or obstructive lung disease. BNP and N-terminal pro-BNP can be drawn do distinguish between cardiac and pulmonary causes of dyspnea.
    Pulmonary function tests have a role in dyspnea diagnosis. TLC is reduced in restrictive disease, but normal or elevated in obstructive disorders . V/Q scanning can rule out thrombosis. In the case of sarcoidosis, fungal infections, or interstitial diseases, lavage or biopsy can be done.