An instrument for determining and registering the variations in the size or volume of bodily organs or the limbs; such as, the arms or legs, and hence the variations in the amount of blood in the limb.

A body area that is used to measure lung volume and pressure.

This body plethysmograph device is used for studying alveolar pressures, lung volumes, and airway resistance. The patient sits or reclines in an airtight compartment and breathes normally.

The pressure of the body plethysmograph changes in the alveoli (tiny sac for holding air in the lungs) when it is alternated by the direction of motions in the compartment and are recorded automatically.

An instrument for measuring changes in volume resulting from fluctuations in the amount of blood that is applied to a digit (finger or toe) of the hand or foot in order to measure skin blood flow.

1. An instrument that uses gas-to-tissue ratio to set an alarm or to measure a volume.
2. A technique for determining blood vessel occlusion that determines volumetric changes in a limb by measuring changes in its girth as indicated by changes in the electric impedance of mercury-containing polymeric silicone tubes in a pressure cuff.