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FEV1 - Definition


Forced expiratory volume in one second, or FEV1, is a value that corresponds to the volume of air exhaled during the first second of forced exhalation. This is one of the measurements taken in pulmonary function tests, called spirometry, which allows for the analysis of obstructions of the airways. This test requires the patient to inhale a maximum of air and then to exhale it as forcibly and quickly as possible. FEV1 varies depending on the respiratory capacity of the patient and their physiology. By analyzing this capacity, certain pulmonary conditions can be screened for and assessed for severity, notably asthma or chronic obstructive pulmonary disease (COPD). COPD differs from asthma in that the obstruction is reversible in the latter, with improved FEV1 values observed following medicinal treatment by bronchodilators.