The Flow-Volume Loop in Normal Subjects and in Diffuse Lung Disease

¹ Assistant Clinical Professor of Medicine, New Jersey College of Medicine, Newark
² Pulmonary Service and the Cardiopulmonary Laboratory, Hackensack Hospital, Hackensack, New Jersey

The maximum effort flow-volume (MFV) loops of 82 subjects were analyzed along with standard spirometric measurements. Thiry-eight were normal smokers and non-smokers. Nineteen had restrictive disease and 25 had obstructive disease. The means of the maximum expiratory and inspiratory flows at peak, and at 75, 50 and 25 percent VC with their ratios are determined for all groups. The location of PEF in the VC, PEF-MEF₇₅/PEF percent and V/V over midexpiration are also given. MEF₂₅ and MEF₂₅/MIF₂₅ were significantly lower in normal smokers than in nonsmokers. V/V was greater in the restrictive group. PEF occurred at lower lung volumes in restrictive disease and at higher volumes in obstructive disease. The obstructive group had low V/ V's and high PEF-MEF₇₅/PEF percent, both correlating with FEV₁/VC percent (r=.79 and -.81). MEF₂₅/MIF₂₅ correlated with percent decrease in dynamic compliance with increased frequency. Small airways obstruction was found when MEF₂₅/MIF₂₅.3. The flow-volume loop provides a simple and rapid assessment of mechanical derangement of the lung.