A hand-held, mechanical, breathing-muscle exerciser intended to be used in respiratory therapy to encourage and motivate deep-breathing manoeuvres, typically for the postsurgical treatment and prevention of atelectasis (lung collapse) and to help facilitate airway opening and clearing. It includes an indicator in a housing that rises in relation to patient inspiratory effort, performed via an attached tube and mouthpiece, to determine the maximum volume of gas which can be inspired [i.e., the inspiratory vital capacity (IVC)]. This is a single-patient device designed for use in a medical facility and in the home. This is a reusable device.