Size of Beta Angle in Felw-Volume Loop of Patients with Obstructive Lung Diseases

It is known that spiromentry is the most conventional method to determine pulmonary function. In spirometry, the shape of flow-volume loop is the most helpful finding to evaluate pulmonary dysfunction. Obstruction is best demonstrated by the slope of the descending portln of the exhalation curve. Measurement of fJ-angle is helpful for determination of this slope. fJ-angle is defined by 3 points in flow-volume loop. The first one, the vertex of the angle, is the point of maximum flow in mid vital capacity. The second point is the end of vital capacity on volume axis and the last one is the point of peak flow on the flow axis. In this study, 325 cases, both smoker and non-smoker, were studied. Rsults show thatfJ-angle decreases by increasing age over 30 years. There is no significant difference in size of fJ-angle between smokers smoking less than 20 pack-years and non-smokers. But, size of this angle decreases in smokers smoking more than 20 pack-years. Size of fJ-angle decreases with obstructive diseases but there is no change in it's size in restrictive diseases. Size of fJ-angle decreases when VC, FEV1, FEF25-75 or FEV1/FVC decrease.