Volume plethysmography is also known as which of the following?

• A. Pneumo-plethysmography
• B. Air-plethysmography
• C. Volume plethysmography
• D. Displacement plethysmography

Answer: (A)

Pneumo-plethysmography is the term that fits volume plethysmography because this method relies on changes in air volume within a sealed chamber around the patient. As the person breathes, thoracic volume changes cause pressure shifts inside the chamber. Those pressure changes are used to calculate lung volumes (like thoracic gas volume) through the relationship between pressure and volume in a closed system. The "pneumo-" prefix means air, which is exactly what's involved here. Other terms aren’t the standard descriptor for this respiratory-apparatus method, and terms like displacement or volume plethysmography don’t convey the air-displacement, closed-chamber principle as clearly.