John Unterborn, MD

ABSTRACT: Indications for pulmonary function tests (PFTs) have widened substantially, ranging from screening smokers for early lung disease to determining the diagnosis and prognosis of pulmonary conditions. Current indications also include screening for drug-induced lung toxicity and preoperative screening for lung resection surgery. In the workup of respiratory symptoms, such as dyspnea, cough, and wheezing, PFTs can identify obstructive or restrictive patterns that may suggest a diagnosis such as asthma or interstitial lung disease. The ratio of FEV1 to forced vital capacity is very sensitive to the presence of airflow limitation, although bronchoprovocation testing may be needed to diagnose asthma, especially in patients with mild intermittent disease. Measurements of lung volumes and carbon monoxide-diffusing capacity (DLCO) provide crucial information in selected patients. For example, a reduced DLCO may be a sign of more advanced disease, such as emphysema or pulmonary hypertension.Since the first description of the spirometer by John Hutchinson in the late 1800s, pulmonary function tests (PFTs) have expanded to include spirometry; lung volumes; carbon monoxide-diffusing capacity (DLCO) (transfer factor); respiratory muscle performance; and exercise and functional testing, such as the 6-minute walk test (6MWT) and cardiopulmonary exercise testing (CPET).