Respiratory system performs functions of ventilation (V), perfusion (Q), and diffusion (DL). All respiratory function tests are based on the measurement of these functions. Spirometry measures the echanical function of the lung, chest wall, and respiratory muscles by assessing the total
volume of air exhaled from a full lung (total lung capacity [TLC]) to an empty lung (residual volume). This volume, the forced vital capacity (FVC) and the forced expiratory volume in the first second of the forceful exhalation (FEV1), should be reproducible to within 0.15 L upon
repeat efforts unless the largest value for either parameter is less than 1 L. Flow-volume loop recording is one of the dynamic ventilatory function tests. This is a safe, simple and reproducible. It is performed routinely in general practice. The shape of the flow-volume loop can differentiate between normal or abnormal lung function. Abnormalities like obstructive or restrictive lung conditions can be differentiated. Although these tests cannot give a pathological
diagnosis and assesses the mechanical functional impairment of various respiratory conditions, but they support other respiratory function tests. Moreover, they are important prognostic indicators of disease process and are commonly used to monitor drug therapy. This review explains the interpretation of flow volume curves in health and disease which will provide an
easy guide for both clinicians and physiologists.
Keywords: Spirometry, FEV1, FVC, Obstructive lung disease, Restrictive lung disease