The ideal spirometer offers so little resistance to the movement of air to and from the subject’s lungs that it does not affect the subject’s respiratory movements. As a teaching device, this spirometer has a number of important extra features:
• Double channel air line valve for open/closed circuit work that connects subject to atmosphere while regulating his/her breathing and becoming accustomed to apparatus. When the valve is turned and the line is connected to the Spirometer, it is possible to determine the exact moment the test starts.
• 600 ml transparent canister can be placed in or out of circuit and can hold color-indicating absorbent.
The Spirometer is equipped with a low inertia potentiometer which provides resistance changes as a function of volume changes. This transducer is activated by the movement of the bell and is powered by two 1-1/2 volt batteries supplied. The 300 mV signal produced is suitable for recording.
The Spirometer housing is made of heavy plastic 6.5 mm (1/4 in) thick. It measures, H x W x D, 300 x 375 x 375 mm (12 x 15 x 15 in) overall. This Spirometer is supplied complete with tubing, mouthpiece, nose clip and a battery powered transducer with cable. It is also supplied with three cartridge pens and a pen arm for kymograph recording.