Spirometry: a key diagnostic test in pulmonary medicine.

Spirometry is a simple and informative test for evaluating airflow obstruction. Measurements from a forced expiratory maneuver are conventionally displayed as volume vs time (spirogram) and flow vs volume (flow-volume loop) tracings. Spirometric measurements like the forced expiratory volume in 1 second inform about the degree of airflow obstruction, whereas the flow-volume loop helps identify the presence and anatomic location of upper airway obstruction, which may mimic symptoms of obstructive lung disease. As a simple, inexpensive, and informative test, spirometry should be used liberally in assessing patients with respiratory symptoms.