Patent Application
20140243970
Not Applicable.
Not Applicable.
The present invention relates in general to circulatory assist systems, and, more specifically, to configuring a backup control unit when a primary control unit experiences a fault or is otherwise replaced.
Many types of circulatory assist systems are available for either short term or long term support for patients having cardiovascular disease. For example, a heart pump system known as a left ventricular assist device (LVAD) can provide long term patient support with an implantable pump associated with an externally-worn pump control unit and batteries. The LVAD 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. The DuraHeart® system employs a centrifugal pump with a magnetically levitated impeller to pump blood from the left ventricle to the aorta. An electric motor magnetically coupled to the impeller is driven at a speed appropriate to obtain the desired blood flow through the pump.
A typical cardiac assist system includes a pumping unit, electrical motor (e.g., a brushless DC motor integrated in the pump housing), drive electronics, microprocessor control unit, and an energy source such as rechargeable batteries and/or an AC power conditioning circuit. A portion of the system is implanted during a surgical procedure in which a centrifugal pump is placed in the patient's chest. An inflow conduit is pierced into the left ventricle to supply blood to the pump. One end of an outflow conduit is mechanically fitted to the pump outlet and the other end is surgically attached to the patient's aorta by anastomosis. A percutaneous cable connects to the pump/motor unit, exits the patient through an incision, and connects to the external control unit.
A control system for varying pump speed to achieve a target blood flow based on physiologic conditions is shown in U.S. Pat. No. 7,160,243, issued Jan. 9, 2007, which is incorporated herein by reference in its entirety. A target blood flow rate may be established based on the patient's heart rate so that the physiologic demand is met. The control unit may establish a speed setpoint for the pump motor to achieve the target flow. It is essential to automatically monitor pump performance to ensure that life support functions are maintained.
Each external control unit is customizable according to the physiologic needs of the patient based on patient-unique data that is electronically stored in the control unit. Such parameters may include a nominal pump speed setting, upper and lower speed limits, parameters for calculating pump speed according to physiologic variables of the patient, flow threshold for triggering low flow alarm, and patient information such as name, ID number, hospital name, date of birth, height, weight, surgical data, and more. Unique data may also be stored relating to the implant such as pump flow estimation coefficients and a pump part number and/or serial number for device traceability. The stored data may be used during normal pump operation or may be accessed by other devices such as a hospital console that can be connected to the control unit.
Because of the safety critical nature of the external control unit, a dedicated backup control unit is often configured and kept with or near the patient so that in the event of the occurrence of any serious fault in the primary control unit it can be swapped out with the backup. All the same patient-unique data is pre-stored in the backup control unit so that it can be connected to the implanted portion of the system as soon as the faulted primary control unit is removed. Typically, the backup control unit may be programmed with the required data at the same time as the primary unit, i.e., at the time of surgical implantation at the hospital using the same hardware devices.
In the event that a primary control unit fails and is swapped for an initial backup control unit, the need arises for securing and programming a replacement backup control unit to be used in the event of a fault occurrence with the active unit. The same equipment that programmed the initial backup unit may or may not be readily available for configuring the replacement backup. Manual configuration of the patient-unique data onto a replacement unit would be time consuming and subject to manual errors. The same or a different hospital console unit could read the patient-unique data from one of the original control units and transfer it in the replacement backup unit, or a handheld memory transfer module can be used. However, the presence on such a programming unit of multiple sets of data transmitted to or from different control units raises concerns over the possibility of configuring a backup control unit with an incorrect data set.
In one aspect of the invention, a method is provided for substituting an initial backup control unit for a primary control unit for controlling an implanted pump in a ventricle assist system enhancing blood flow in a patient. In response to a failure of the primary control unit, the initial backup control unit is connected to the implanted pump as a new primary control unit. An interface device is connected to one of the initial backup control unit or the faulted primary control unit. Patient-unique data is downloaded to the interface device to create a transfer data set. The interface device is connected to a replacement backup control unit. The transfer data set is uploaded from the interface device to the replacement backup control unit. The transfer data set on the interface device is modified after uploading to prevent a subsequent uploading from the interface device to another control unit.
Referring to
Control unit 15 further includes internal memory that must be configured with patient-unique and system-unique data to be used for system operation and for providing access for reading the data during subsequent patient care. At or just prior to the time of implantation, controller 16 is connected to a hospital console 20 via a connecting cable 21 for the purpose of programming the data. The data may be manually entered using a human machine interface (HMI) in hospital console 20 (e.g., a touchscreen 22 and manual control elements 23) and/or obtained from a patient database in a separate server 24 connected via a local area network 25.
A substantially identical backup control unit 26 is also connected to hospital console 20 via cable 21 in order to program it with the same patient-unique data and pump-unique data for the implanted pump. Subsequently, backup control unit 26 is kept at the ready in order to substitute it for control unit 15 in the event of an emergency or routine replacement.
In the event that a fault occurs in a primary control unit, it must be replaced with the backup control unit and then a new backup control unit must be obtained and configured. Various protocols can be established for replacing a faulted controller. One preferred scenario proceeds as shown in
Since the patient has had to swap their backup unit for the primary unit, they may no longer have a backup unit readily available. At a first reasonable opportunity, they should restore their backup protection by obtaining a replacement backup control unit 32. Typically, a visit to the hospital or other care center would be required in order to secure the replacement backup and to have it programmed for the patient.
In a third step •, an interface device 33 at the hospital or other care center is connected to one of control unit 30 or control unit 31 in order to propagate the patient-unique and pump-unique data to the new backup. Interface device 33 may be any electronic unit capable of reading and writing data over a cable connection. It may preferably be comprised of the hospital console specifically designed to work together with the control unit. Device 33 could alternatively be a portable, handheld memory unit designed to only perform the function of duplicating the patient and pump data. Upon connection with control unit 30 or 31, interface device 33 downloads the patient-unique/pump-unique data and stores it as a transfer data set. In a fourth step •, the downloaded data set from one of the initial control units is uploaded from interface device 33 to replacement backup control unit 32.
Since interface device 40 is connectable to multiple control units and could potentially have memory contents corresponding to patient and pump data from multiple patients, a potential problem arises in which incorrect data could be copied to a control unit. The present invention provides certain precautions to avoid this potential problem.
The interface device is connected to a replacement backup control unit in step 53. In step 54, the interface device uploads the transfer data set to the replacement control unit, and the replacement unit is held by the patient for possible future use in the event of a fault occurrence in the currently-used control unit (which was formerly the backup unit). Following the upload, the transfer data set on the interface device is modified in step 55 to prevent a subsequent uploading from the interface device to another control unit. In one embodiment, the transfer data set may be erased from the interface device immediately upon a successful upload to the replacement unit. As used herein, erase means to either overwrite the data or make it inaccessible by deleting an entry from a file allocation table, for example. In another embodiment, erasing the transfer data set may occur after a predetermined delay (e.g., 15 minutes) following a successful upload, which would allow a brief interval in which the transfer data set could be propagated to additional devices such as another replacement control unit.
In yet another embodiment, the modification of the transfer data set may be comprised of the appending of a time stamp to the transfer data set. The time stamp preferably indicates a date and time-of-day when the patient and pump data was downloaded from the faulted primary or initial backup control unit. In the event that a time stamp is used, step 54 of
