Flow control method and device
An arterio-venous graft 16 is provided with a constriction device 20 near its arterial end. The constriction device 20 is used to reduce the flow through the AV graft under normal conditions and to relieve the constriction when high flow through the AV graft is required, such as for vascular access for hemodialysis.
1. A device for controlling flow in an AV graft or AV fistula used for vascular access for an extracorporeal circuit, the device comprising:
a) a plurality of actuators capable of applying pressure to a vessel unequally and inwardly in more than two different directions, to provide a reduced flow through the AV graft or AV fistula, when flow through the extracorporeal circuit is not to occur; and
b) an adjuster for changing the degree of constriction, to modify the flow through the AV graft or AV fistula, when flow through the extracorporeal circuit is to occur, the adjuster having a receiver, a motor and a transmission;
wherein the plurality of actuators is configured to apply partial constriction over an elongate portion of the vessel, the vessel having a diameter “D” in an unconstricted state, the elongate portion being constricted having a length “L” and the length “L” being at least twice the diameter “D”.
2. The device according to claim 1 , wherein the vessel is the AV graft.
3. The device according to claim 1 , wherein the motor provides power to drive the plurality of actuators.
4. The device according to claim 1 , further comprising a rotatable member adapted to driving the plurality of actuators.
5. The device according to claim 4 , wherein the rotatable member is a drive shaft of the motor.
6. The device according to claim 1 , further comprising a sensor configured to sense one or more of flow, pressure, or turbulence in the vessel, or pressure applied by the plurality of actuators.
7. The device according to, claim 1 wherein the plurality of actuators are arranged to provide constriction in at least four different directions.
8. The device according to claim 1 , further comprising an adhesive for adhering the plurality of actuators to the AV graft or AV fistula.
9. The device according to claim 1 , further comprising a turbulence measuring device.
10. The device according to claim 1 , further comprising a flow measuring device.
11. The device of claim 10 wherein the flow measuring device comprises a Doppler device.
12. The device of claim 10 wherein the flow measuring device comprises an electromagnetic flow sensor configured to detect a voltage generated by an externally applied magnetic field, the externally applied magnetic field applied to the AV graft or AV fistula.
13. The device of claim 1 wherein the receiver comprises a converter for converting radio frequency energy into energy for powering the motor.
14. The device of claim 1 further comprising:
c) an antenna for receiving signals sent telemetrically from an external control device;
d) the receiver being coupled to the antenna for delivering electrical power in response to the signals received by the antenna; and
e) the motor being coupled to the receiver and coupled to the plurality of actuators, the motor configured to change the degree of constriction applied by the plurality of actuators in response to the electrical power delivered by the receiver.
15. The implantable device of claim 14 wherein the implantable device is located inside a patient's body and the external control device is located outside the patient's body.