During inspiration, what happens to upper-extremity venous flow velocity?

• A. Increases
• B. Decreases
• C. Remains unchanged
• D. Becomes absent

Answer: (A)

During inspiration, intrathoracic pressure becomes more negative, which enhances venous return to the heart. This suction effect pulls blood from the upper extremities into the central veins, so the venous flow velocity detected in the upper-extremity veins increases on Doppler. If you think about the pressure gradient driving the flow toward the heart, inspiration increases that gradient, leading to higher velocity. The other options don’t fit the normal phasic response: venous flow isn’t typically reduced, unchanged, or abolished simply due to inspiration.