Durable, portable, and accurate. The Assess® Peak Flow Meter provides an objective measurement of peak expiratory flow (PEF), a valuable indicator of lung function. Assess enables the nurse to better manage children with asthma. Assess helps asthmatics maintain appropriate medication levels and provide a warning of impending asthma attacks. Single patient use. Low range is 30 - 390 l/min. Full range is 60 - 880 l/min.