What is the flow volume equation used for grafts?

• A. Q = area x avg velocity x 60 sec
• B. Q = circumference x velocity
• C. Q = area x velocity x 3600
• D. Q = area x velocity x 1 second

Answer: (D)

Volumetric flow through a graft is the product of the graft’s cross‑sectional area and the mean velocity of blood through that cross‑section. This gives volume per unit time. If you express the time interval as one second, you obtain flow in milliliters per second (since area in cm² and velocity in cm/s yield cm³/s, which equals mL/s). That’s why the correct form is area × velocity × 1 second. If you wanted per minute or per hour, you’d multiply by 60 or 3600, respectively. The circumference factor isn’t part of the flow equation, so it doesn’t apply here.