The flow volume loop: normal standards and abnormalities in chronic obstructive pulmonary disease.

The flow-volume loop is a test of ventilatory function in which a graphic recording of maximal flow rates is dispiayed at all lung volumes during a maximal effort forced expiratory and inspiratory vital capacity maneuver. The test is errsy to demonstrate, administer, and analyze. Pulmonary diseases produce characteristic flow-volume loop abnormalities. The visualization of abnormalities and calculation of instantaneous Bow rates at specific lung volumes mdce this test useful in screening for pulmonary disease, assessing the pulmonary effect of drugs, and following progression or regression of pulmonary disease. Normal standards for loop vital capacity, volume expired or inspired to achieve peak flow rate, expiratory and inspiratory peak flow rates, flow rates at 25 percent, 50 percent, and 75 percent of the vital capacity, and prediction equations for these indices are reported. Patterns of abnormality detected in the chronic obstructive pulmonary diseases, bronchial asthma, chronic bronchitis, and pulmonary emphysema are described. Alteration of position from sitting to standing or supine for performance of the test did not significantly alter mean flow-volume loop indices.