Dynarex Volumetric Incentive Spirometer, 5000mL.The Dynarex Resp-O2 Peak Flow Meter is a hand-held monitoring device that measures Peak Expiratory Flow (PEF), an indication of how fast a patient can forcefully exhale after a full exhalation. This lightweight, durable peak flow meter is designed to help patients track daily changes in their breathing patterns.TheDynarexResp-O2 peak flowmeterisavailableinAdultsize(Standard Range 50-800 L/min)andPediatricsize(Low Range50-300 L/min).