Flow-volume curves in obstructive and restrictive lung disease

Sample flow-volume curves during a maximal forced expiration in normals and in obstructive and restrictive lung disease. The normal expiratory portion of the flow volume curve is characterized by a rapid rise to the peak flow rate, followed by a nearly linear fall in flow as the patient exhales toward residual volume. With obstructive disease, maximal expiration begins and ends at higher lung volumes and lower flow rates than normal. With restrictive disease, the lung volumes and flow rates are reduced but the flow in relation to lung volume is actually higher than normal.