Patent Application
20140066689
Not Applicable.
Not Applicable.
The present invention relates in general to a left ventricular assist system (LVAS), and, more specifically, to an integrated controller that houses a main battery and a backup battery.
A heart pump system known as a left ventricular assist system can provide long term patient support with an implantable pump associated with an externally-worn control unit and batteries. The LVAS improves circulation throughout the body by assisting the left side of the heart in pumping blood. One such system is the DuraHeart® LVAS system made by Terumo Heart, Inc., of Ann Arbor, Mich.
A typical LVAS system employs a centrifugal pump implanted in the patient's chest, an inflow conduit coupling the pump inlet to the left ventricle, and an outflow conduit coupling the pump outlet to the aorta. During implantation, one end of the outflow conduit is mechanically fitted to the pump via a connector and the other end is surgically attached to the patient's ascending aorta by anastomosis. The pump is electronically controlled to provide a flow rate from two to eight liters per minute, for example. The controller typically contains a display screen for showing system status. The controller is connectable to a main console to allow a physician to set-up, adjust, and monitor the controller and pump units.
In addition to the controller, the extracorporeal portion of the circulatory support system includes batteries or other power supply. The batteries and controller are needed on a full time basis, so they are typically worn externally by the patient. A control and communication cable is connected between the implanted pump and the electronic controller via an exit site in the patient's skin. Once configured, the controller operates on a standalone basis and the entire system is portable to allow patient mobility.
The goal of the control unit is to autonomously control the pump performance to satisfy the physiologic needs of the patient while maintaining safe and reliable system operation. Since continuous operation is vital, conventional systems have been provided with at least two batteries so that there is backup capacity during mobile use. Typically one or two full-size batteries are installed in the system and carried by the patient. By using multiple main batteries, normal pump operation can continue beyond the charge time of one battery. Moreover, an alternate power source is thereby available during times that a discharged battery is being removed for recharging and replacement by a freshly charged battery. In addition, a lower capacity backup battery has also sometimes been used in conventional systems that is permanently mounted inside the control module and provides power when all other sources fail. The backup battery ensures sufficient power to operate alarms when main battery power may fail, and may also have capacity to run the pump for short periods.
For patient convenience and mobility, it is desirable to minimize the size of the external equipment. This goal can be met with an integrated controller that incorporates the main and backup batteries with all the control electronics. However, the battery combinations employed by conventional systems have not been successfully integrated. Furthermore, a problem involving the internal backup batteries has been that they eventually need to be replaced due to loss of charge-carrying capacity over time, and the control unit must be taken out of service in order to dismantle the controller module to access and replace the internal backup battery.
In one aspect of the invention, an integrated control module is provided for a ventricular assist device. A housing receives a power monitoring/switching circuit, a main receptacle, and a quasi-internal backup receptacle. The main receptacle within the housing receives a main battery. The main receptacle is configured for manual installation and removal of the main battery without requiring any separate tool. The quasi-internal backup receptacle within the housing receives a backup battery having a battery capacity less than the main battery. The backup receptacle includes a locking mechanism that requires use of a separate tool to unlock the locking mechanism for removing the backup battery. The backup battery is installed and removed without disturbing power supplied from a main battery in the main receptacle to the power monitoring/switching circuit.
Referring to
System 20 includes a housing 21 that incorporates an electronic controller (for performing typical controller functions including user interface, alarm, pump control and monitoring, power control and monitoring, etc.), a single main battery which is replaceable by the user, and a backup battery capable of supporting full operation for a short period of time (e.g., 30 minutes). Housing 21 receives a main battery 22 and a backup battery 23. A human machine interface (HMI) 24 includes a display 25 and control push buttons 26. A connector 27 interfaces the integrated control module to the power/communication cable that connects to the implanted pump.
A benefit of the prior art internal backup battery which was housed in an inaccessible location within a control module was that the backup battery was always present and could not be inappropriately or mistakenly removed during times when the control module was in use. However, the control module had to be taken out of service whenever the backup battery needed replacement. To improve product longevity and flexibility, the present invention uses a quasi-internal backup battery as shown in
Backup battery module 35 preferably contains an outer casing for forming a continuous surface with housing 21 when it is installed in receptacle 36. This adds to the impression that backup battery 35 should normally not be removed.
A power connector 41 within backup receptacle 36 meets with power terminals on backup battery 35 (not shown). An additional power connector 42 is provided for coupling the integrated controller to an external source of AC or DC power, such as when the patient is at home, traveling in an automobile, or in a hospital.
The locking mechanism shown in
Another feature of the present invention is an ability to ensure that the backup battery can be removed and reinstalled without disturbing power supplied from a main battery in the main receptacle to a power monitoring/switching circuit installed within the housing. This allows the backup battery to be replaced without taking the controller module out of service. In
Logic block 47 is respectively coupled to the supply terminals of external power sources #1 and #2 and to backup battery 23. Based on the detected state (i.e., presence and/or charge condition) of each potential power source and a predetermined priority for using the different power sources, control logic block 47 activates a corresponding one of FETs S1-S3 to couple the selected power source to power bus 46. A diode 48 couples the output of FET S3 to power bus 46 to prevent recharging of backup battery 23 directly from bus 46. Backup battery 23 is instead recharged using an internal battery charger circuit 49 receiving power from bus 46 via a FET S4. Logic block 47 controls the state of FET S4 such that backup battery 23 is recharged only when an external power source with sufficient capacity is present.
Power from primary power bus 46 is provided to HMI 24 and to a pump control and communication block 50 that interfaces via cable 14 to the implanted pump. In particular, power monitoring/switching circuit 45 is preferably configured to continuously supply power from an installed main battery during times that the backup battery is removed.
