Which of the following stayed constant throughout this activity?

Which of the following stayed constant throughout this activity?

• A. Stroke volume
• B. Flow rate
• C. Pressure gradient
• D. Pump speed

Answer: (A)

Stroke volume is the amount of fluid ejected with each beat. In many cardiovascular dynamics labs, the pump acts as a fixed-displacement device, so the volume moved per stroke stays the same regardless of how fast the pump is driven or how the load changes. As you vary the pump speed to simulate different heart rates, the per-beat amount remains constant, while the overall flow rate (volume per time) changes because flow rate depends on both stroke volume and heart rate. The pressure gradient across the circuit will also change with flow and resistance. The pump speed itself is the adjustable variable you control, so it does not stay constant. Therefore, the stroke volume stays constant throughout the activity.

Stroke volume is the amount of fluid ejected with each beat. In many cardiovascular dynamics labs, the pump acts as a fixed-displacement device, so the volume moved per stroke stays the same regardless of how fast the pump is driven or how the load changes. As you vary the pump speed to simulate different heart rates, the per-beat amount remains constant, while the overall flow rate (volume per time) changes because flow rate depends on both stroke volume and heart rate. The pressure gradient across the circuit will also change with flow and resistance. The pump speed itself is the adjustable variable you control, so it does not stay constant. Therefore, the stroke volume stays constant throughout the activity.