is_about respiratory system disorder respiratory system pulmonary function measurement maximal midexpiratory flow rate true Measurement of rate of airflow over the middle half of a FORCED VITAL CAPACITY determination (from the 25 percent level to the 75 percent level). Common abbreviations are MMFR and FEF 25%-75%. Dani Welter MESH:D008450 FEF25-75% respiratory disease biomarker