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Spirometry results for a patient with asthma: volume–time curves (A), flow–volume loops (B) and data table (C). Obstruction is indicated by the ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (55%); significant reversibility is indicated by the improvement in FEV1 after administration of bronchodilator (0.96 L or 53%). These results are diagnostic for asthma.
