Incentive spirometer

DETAILED DESCRIPTION In accordance with the present invention, there is provided an improved spirometer having the capability of providing excellent accurate readings of a pulmonary function.
As was stated, the spirometer is of the closed circuit type and utilizes a movable piston fitted within a closed cylinder provided with suitable ports.
In one form of use the patient inspires a breath from a port means at the end of the cylinder and causes the piston to move a distance in proportion to the patient's ability to inspire.
In another form of use of the invention the patient's expired breath is introduced into the other end portion of the cylinder which also causes the piston to move a distance in proportion to the patient's tidal volume.
A unique seal is provided between the outer perimeter of the movable piston and the interior of the cylinder in order to prevent any leakage therebetween.
The seal is characterized by low friction or hysteresis during movement, and has substantially no memory, yet it has sufficient pneumatic stiffness to resist stretching or expanding throughout the expected pressure range.
Also, the problem of seal blow-out is virtually eliminated.
Additionally, the rolling seal having a U-shaped configuration permits a substantial length of travel of the piston to insure accurate measurements therefrom and prevents bouncing or other adverse effects from external environment.