Why We Need the Journal of Interactive Advertising

There is disclosed an incentive spirometer for measuring, as desired, the inspiratory breathing capacity and/or the expiratory breathing capacity including a freely floating piston positioned within a chamber. The piston is responsive to an inspired breath inhaled from one end of the chamber and also responsive to an exhaled breath introduced into the other end of the chamber. A novel rolling seal is provided which causes extremely minute friction losses during movement and which effectively seals the area between the external perimeter of the piston and the internal surface of the chamber.