Differentiate central venous pressure from mean circulatory pressure.

• A. CVP is the pressure in the thoracic veins near the right atrium; MCP is the hypothetical average pressure across the circulation when flow ceases.
• B. CVP is the mean pressure in the arterial system; MCP is the mean venous pressure.
• C. CVP is LV diastolic pressure; MCP is right atrial pressure.
• D. CVP and MCP are identical.

Answer: (A)

Central venous pressure is the pressure in the central venous system as it approaches the right atrium, reflecting the filling pressure of the right heart and the current venous return. Mean circulatory pressure is a theoretical, uniform pressure across the entire circulation if there were no blood flow (heart stopped). These are different because CVP is a local, real-time measure near the right atrium, while MCP is a global, hypothetical pressure that sets the driving force for venous return when flow ceases. The correct description captures CVP as the thoracic venous pressure near the right atrium and MCP as the hypothetical average pressure across the circulation if flow were zero.