Surgery – Cardiac augmentation
Reexamination Certificate
1999-06-24
2001-10-02
Kamm, William E. (Department: 3762)
Surgery
Cardiac augmentation
Reexamination Certificate
active
06296605
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to drive systems for mechanically assisting the heart and more particularly to a high-pressure inflation system capable of controlling an adjustable pressure pulse applied to a cardiac compression apparatus. The applied pressure pulse can be adjusted with a high degree of accuracy with regard to the plateau pressure.
BACKGROUND OF THE INVENTION
An important life-saving technique for individuals diagnosed with weakened hearts includes mechanically assisting the heart to pump blood. Assistance to the heart ensures an adequate blood pressure for sufficiently supplying blood throughout the body without undue stress on the heart muscle. Typically, a device such as a heart compression apparatus, or cuff, carries out the assistance during invasive surgery. An alternative related application for the apparatus involves cardiopulmonary resuscitation (CPR) techniques to rhythmically squeeze the heart in cases where the heart fails to beat at all.
Those skilled in the art have proposed a variety of devices to successfully carry out the heart compression function to maximize support for the heart and provide reliable and accurate functionality. One such cuff device, disclosed in pending Provisional U.S. patent application Ser. No. 60/028,722, filed on Oct. 18, 1996 and assigned to the assignee of the present invention, carries and supports the heart during invasive surgery while uniformly applying pressure directly to the heart through means of an inflatable liner. The liner is cyclically inflated and deflated by an inflation system to apply pressure to the heart.
Because each heart pumps blood according to a pressure profile unique for each patient, successful cardiac compression on the inflatable liner depends upon the inflation system being controllable to somewhat match the patient's personal cardiac rhythm or pressure profile. An equally important consideration involves the limited duration of the heart's systolic cycle, which provides only about fifty to one-hundred milliseconds within which to establish synchronous compression.
One proposal for pneumatically driving a cardiac compression device, such as an Anstadt cup or intra-aortic balloon, is disclosed in U.S. Pat. No. 4,016,871. The pneumatic drive system is housed within a console and includes a relatively low-pressure compressor coupled in parallel to a pressure regulator and a vacuum regulator. The respective regulators are connected to respective reservoirs having outputs coupled to respective solenoid valves. The solenoid valves are controlled by an electronic sequencer to pass pressurized pulses through an elongated pressure line coupling the console to the cardiac compression device for inflation and deflation thereof.
A second proposal, such as that disclosed in U.S. Pat. No. 5,300,017, describes a driver for a cardiac compression device including an isolator with respective first and second chambers separated by a flexible diaphragm. The first chamber is coupled through respective positive and negative pressure switching valves to respective positive and negative air pressure sources. The second chamber of the isolator communicates directly with the cardiac compression device. The diaphragm responds to positive or negative pressures in the range of about 10 mmHg from the respective sources to decrease or increase the volume within the second chamber, thereby pressurizing or depressurizing the cardiac compression device.
While these proposals appear to work well for their intended applications, they are often disposed several feet from the cardiac compression device. This is typically because of the controlled conditions associated with surgical environments. As a result, the extended length of the pressure line generally requires a relatively large diameter tube to minimize line resistance. The increase in volume, as a consequence, increases the overall flowrate through the system, thereby increasing the component sizes and costs.
What is needed and heretofore previously unavailable is a high-pressure drive system for a cardiac compression device, such as a cuff, that enables reduced component sizes and improved rise-time response. A further need exists for such a system having improved safety features for patient protection. The high-pressure drive system of the present invention satisfies these needs.
SUMMARY OF THE INVENTION
The system of the present invention provides the capability of miniaturizing the components necessary to effect pressure pulses to inflate a heart assistance device. The system also serves to improve inflation performance by reducing rise times for the respective pressure pulses, and maintaining a high level of safety for patients.
To realize the above advantages, in one form the invention comprises a high-pressure inflation system for driving an inflatable heart assistance device. The system includes a fluid source for supplying a fluid at a relatively high pressure and a compression tank plumbed in selective communication with the pneumatic source. The compression tank is operative to store a predetermined volume of the pressurized fluid at approximately the high pressure created by the fluid source. A transfer valve is disposed downstream of the compression tank and is coupled to the heart assistance device. The compression tank and transfer valve are maintained in close proximal relation to the heart assistance device with the transfer valve being responsive to predetermined signals to release the pressurized fluid from the compression tank to fill the heart assistance device and expand the device to compress and assist the heart.
In another form, the invention comprises a transfer valve for switching a load between respective pressurizing and venting states in response to signals generated by a controller. The transfer valve includes respective pressure and venting ports and an output port directly coupled to the load. The output port is alternately coupled to the pressure and venting ports through a spring-biased switching mechanism.
In one embodiment, the invention includes a convenient safety mechanism. The safety mechanism guarantees that the inflated cuff vents to atmosphere in the event of a failure in the drive system. This is accomplished by monitoring the cuff pressure and opening the safety valve when the pressure remains high.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 3465746 (1969-09-01), Guarino
patent: 4016871 (1977-04-01), Schiff
patent: 4648385 (1987-03-01), Oumi et al.
patent: 5059167 (1991-10-01), Lundquist et al.
Baldwin, II R. Mitchell
Levin Howard R.
Michelman Paul C.
Darby & Darby
Kamm William E.
Paramount Capital Investments, LLC
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