Which plethysmography method uses a cuff around a limb that is inflated to create a volume change, which is converted to an analog pressure signal for recording?

• A. Volume plethysmography
• B. Photoplethysmography
• C. Impedance plethysmography
• D. Strain gauge plethysmography

Answer: (A)

Volume plethysmography uses a cuff around a limb that is inflated to create a volume change. As the limb’s blood volume fluctuates with the heartbeat, the cuff’s enclosed air experiences pressure changes. The cuff transducer converts those pressure changes into an analog signal that is recorded over time, producing a tracing of pulsatile volume changes. This differs from methods that rely on light absorption (photoplethysmography), electrical impedance (impedance plethysmography), or direct strain measurement of limb circumference (strain gauge plethysmography).