The best portable oxygen concentrator in its class with Zen-O pulse and continuous oxygen delivery modes for active patients requiring oxygen therapy. Which (RRT) With breath sensing accuracy and Zen-0 therapy response rate Features automatically adapts to patient requirements. • Portable oxygen concentrator supplies the patient with up to 2 liters of oxygen per minute according to needs. • Unlike other devices that supply a fixed amount of oxygen. Zen-O automatically increases the amount of oxygen delivered if the patient's respiratory rate increases.