A man undergoing whole body<unk> y. A modern body<unk>  using ultrasound A<unk>  is an instrument for measuring changes in volume within an organ or whole body (usually resulting from fluctuations in the amount of blood or air it contains). The word is derived from the Greek "plethysmos" (increasing, enlarging, becoming full), and "graphein" (to write).
Plethysmograph
Pulse oximetry
CO-oximeter
Hyperoxia test
Optoelectronic plethysmography
Sphygmograph
Hemoximetry
Photoplethysmogram