Pulmonary Function Test designed to perform all respiratory gas volume and flow measurements needed for diagnosis of basic pulmonary functions. These instruments measure quiet breathing, determining tidal volume, and trace deep inspirations, evaluating variables such as the maximum volume of gas that can be expired from the lungs (i.e., expiratory vital capacity [EVC]) and the maximum volume of gas that can be inspired into the lungs (i.e., inspiratory vital capacity [IVC]). The IVC test may be performed under static conditions (e.g., to determine the vital capacity) or as a dynamic test using maximum effort against time (e.g., to determine forced expiratory volume [FEV]). Diagnostic spirometers consist of a mechanical or electromechanical device with a computerized unit to process the data, volume and/or flow sensors, a display, and a graph recorder. Some instruments can also determine other parameters, such as oxygen intake and carbon dioxide expiration, either for both lungs simultaneously or for each one independently. These spirometers are intended to assess pulmonary status, to monitor diseases, and/or to evaluate treatment effectiveness and/or disability; they cannot determine lung volume, residual pulmonary, or total lung capacity. Instruments combining spirometry and pulse oximetry capabilities are also available.