During inspiration, which statement about the IVC is true?

During inspiration, which statement about the IVC is true?

• A. IVC expands
• B. IVC diameter remains unchanged
• C. IVC compressed
• D. IVC velocity increases

Answer: (C)

During inspiration, intrathoracic pressure becomes more negative, increasing venous return to the heart and lowering right atrial pressure. The IVC is a compliant vessel, so as more blood is drawn in and the RA pressure drops, the IVC diameter decreases and it appears to collapse on ultrasound. This inspiratory collapse is the correct description. The other ideas don’t fit the typical dynamic: the IVC does not usually expand with inspiration, its diameter often changes rather than staying the same, and Doppler velocity is not the defining feature of this respirational change.

During inspiration, intrathoracic pressure becomes more negative, increasing venous return to the heart and lowering right atrial pressure. The IVC is a compliant vessel, so as more blood is drawn in and the RA pressure drops, the IVC diameter decreases and it appears to collapse on ultrasound. This inspiratory collapse is the correct description. The other ideas don’t fit the typical dynamic: the IVC does not usually expand with inspiration, its diameter often changes rather than staying the same, and Doppler velocity is not the defining feature of this respirational change.