The FlowMakerŽ external controller delivers power to the heart pump, provides the interface for patient control of the pump speed, and monitors system function to alert the patient to potential problems, such as low power or underspeed operation.
The only user-controllable feature of the Jarvik 2000 is the pump speed, set by a dial within the range of 1 to 5. Speed setting 1 is slowest, driving the impeller at 8,000 RPM and producing blood flow of 1-2 liters per minute. Speed setting 5 is fastest, driving the impeller at 12,000 RPM and producing blood flow of 5-7 liters per minute.
On the face of the controller are indicator lights that show when the battery is low or the pump is stopped or operating underspeed. A lighted power indicator scale shows the amount of power used by the pump in real time. The power indicator lights range from 3 to 13 and correspond to the amount of power, in watts, being used at a given instant. Generally, these markers show that more power is used when the pump speed is higher. They may fluctuate in synchrony with the biological heartbeat, however, since even the heart's weakened pumping action varies the load on the Jarvik 2000.