The term FEF stands for the forced expiratory flow and refers to the amount of fluid which passes through an organ at a specific time point. FEF 200-1200 refers to the maximal expiratory flow and represents the rate of airflow at forced vital capacity. It is one of the tests used to measure and estimate the pulmonary function. A 50-year-old male who is 6 feet 1 inch should be approximately 554 L/min.