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any device for measuring and recording variations in the volume of an organ, part, or limb.
body plethysmograph a device used in pulmonary function tests to measure parameters such as functional residual capacity (FRC) and lung-thorax compliance (CLT). It consists of a large box in which the subject can be sealed so that volume of the thorax can be determined from pressure changes in the box.
a chamber apparatus surrounding the entire body, commonly used in studies of respiratory function.