text: 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).
option_0: Plethysmograph
option_1: Peak flow meter
option_2: Pulse oximetry
option_3: CO2 sensor
option_4: Cardiotocograph
option_5: Pulse pressure
option_6: Arterial blood gas
option_7: Sphygmomanometer