Gambro Lundia AB v. Baxter Healthcare Corp., 92-C-574.

Decision Date18 August 1995
Docket NumberNo. 92-C-574.,92-C-574.
Citation896 F. Supp. 1522
CourtU.S. District Court — District of Colorado
PartiesGAMBRO LUNDIA AB, Plaintiff, v. BAXTER HEALTHCARE CORPORATION, Defendant.

COPYRIGHT MATERIAL OMITTED

COPYRIGHT MATERIAL OMITTED

Willem G. Schuurman, Austin, TX, for plaintiff.

Timothy J. Malloy, McAndrews, Held & Malloy, Chicago, IL, for defendant.

FINDINGS OF FACT, CONCLUSIONS OF LAW AND ORDER

CARRIGAN, District Judge.

Plaintiff, Gambro Lundia AB (Gambro), a manufacturer of hemodialysis equipment, commenced this action against one of its competitors, Baxter Healthcare Corporation (Baxter). Gambro alleges that certain hemodialysis monitors manufactured by Baxter infringe claim 1 of its United States Patent No. 4,585,552 (the Gambro '552 patent). Baxter has raised a series of affirmative defenses and has asserted a counterclaim seeking declaratory judgments of patent invalidity and unenforceability.

Trial to the court on the liability issues has been completed, and those issues are ripe for decision. Jurisdiction exists under 28 U.S.C. § 1338(a). This memorandum constitutes the court's findings of fact and conclusions of law required by Fed.R.Civ.P. 52(a).

I. BACKGROUND.
A. Background of Hemodialysis Technology.

Hemodialysis systems remove blood contaminants and excess water from a patient's blood when the patient's kidneys are not capable of performing that function adequately.1 Without dialysis, such a patient may die within a short time.

During a typical dialysis treatment, a manmade dialysis solution called dialysate is passed through a device known as a dialyzer, which acts as an artificial kidney. The dialysate is passed on one side of a porous diffusion membrane in the dialyzer. The patient's blood is passed on the other side of the membrane. The difference between the dialysate pressure and that of the patient's blood is called the transmembrane pressure. Toxic molecules and excess water, collectively called ultrafiltrate, diffuse from the patient's blood through the pores in the membrane into the dialysate. Thus the volume of the spent dialysate (as enhanced by the added impurities and water) flowing out of the dialyzer is greater than the volume of fresh dialysate entering the dialyzer. The difference is the ultrafiltrate. The rate at which ultrafiltrate is removed from the patient's blood may be controlled by varying the transmembrane pressure. (See Diagram 1.)

It is medically critical to measure accurately and to control precisely the amount of ultrafiltrate removed from a patient's blood during dialysis. If too much or too little ultrafiltrate is removed, the patient may suffer serious or even fatal consequences.

One method for measuring the amount of ultrafiltrate removed from a patient is to place a first flow sensor at the input to the dialyzer and a second flow sensor at the output from the dialyzer. (See Diagram 2.) The difference between the rate of dialysate flow into the dialyzer and the rate of dialysate flow out of the dialyzer equals the ultrafiltration rate. The total amount of ultrafiltrate removed from the blood may be calculated by multiplying the ultrafiltration rate by the treatment time. This technology and procedure for measuring the amount of ultrafiltrate removed from a patient, known as flowmetric measurement, was well known long before issuance of the patent here in dispute.

B. Development of Gambro's Ultrafiltration Monitor.

In the late 1970's and early 1980's, errors in measuring the ultrafiltrate removed during dialysis were common. Early measurement systems used "weighbeds." These contrivances were used in a process that measured the patient's weight before, during, and after dialysis, then relied on the patient's weight loss to indicate the amount of ultrafiltrate removed from the patient during a treatment. This method of monitoring ultrafiltrate removal proved expensive, cumbersome, and inaccurate. Various researchers working independently during that time period attempted to solve these problems by developing alternate ultrafiltration monitor and control systems.

The first commercially available improvement after weighbeds was developed by Repgreen Limited, a British company. The Repgreen ultrafiltration monitoring system, known as the UFM 1000, was based upon the research of Prof. Michael Sanderson, and was developed under the supervision of Keith Wittingham, Repgreen's chief designer from 1972 until 1979. The UFM 1000, first available in late 1977, incorporated a flowmetric system that utilized two electromagnetic flow sensors to measure the difference between the rates of flow of dialysate flowing into and out of the dialyzer.

To ensure accuracy, the UFM 1000 provided for recalibration of the electromagnetic flow sensors prior to each dialysis treatment. Its recalibration involved inserting a hose between the first and second flow sensors in place of the dialyzer, thus directing an equal flow of clean dialysate through both flow sensors. The flow sensors were then recalibrated to reflect this equal flow, and more accurate measurements of ultrafiltrate were achieved. This procedure was described in a manual that accompanied each UFM 1000.

During 1979, Repgreen was contacted by Gambro in connection with the latter's efforts to develop an accurate ultrafiltration monitor for use with its dialysis machines. After Repgreen was liquidated in July 1979, Gambro purchased certain Repgreen assets, including rights to the UFM 1000 monitor. A version of the UFM 1000 was sold by Gambro as the Gambro UFM 10-1. However Gambro was dissatisfied with the UFM 10-1's monitoring system and attempted to develop an improved monitor. Specifically, Gambro attempted to correct a "drift" in the flow sensors that resulted in the UFM 10-1 monitoring system becoming less accurate as a treatment progressed. This drift was caused by a variety of phenomena, including the fact that contaminants removed from the patient's blood during dialysis collected on the downstream or second flow sensor, significantly affecting its accuracy.

At the time of Gambro's alleged invention, it was well known that pretreatment recalibration of flow sensors was necessary. However, contaminants removed from a patient's blood during dialysis collect on the downstream flow sensor during the course of a single dialysis treatment. Pretreatment recalibration could not address this problem.

No earlier than June 1982, four engineers at Gambro headquarters in Sweden—Bengt-Ake Gummesson, Sven Jonsson, Ulf Mattisson, and Bengt Holmberg — allegedly invented a system whereby measurement inaccuracies that occur during dialysis in the flow sensor downstream from the dialyzer can be rectified. Their alleged invention is disclosed by the Gambro '552 patent here at issue.

Gambro's alleged invention provides for activating valves that direct the clean dialysate's flowpath through the first flow sensor and around the dialyzer then through the second flow sensor. During this recalibration process, the spent dialysate — i.e., dialysate contaminated with ultrafiltrate—is prevented from flowing from the dialyzer through the second flow sensor. Because the same clean dialysate fluid stream passes through both flow sensors, the measured difference in the rate of flow can be used as a reference for subsequent recalibration of the flow sensors. In this way, the flow sensors can be recalibrated, not only before dialysis begins, but also at intervals during the dialysis treatment to adjust for any inaccuracies in the second flow sensor attributable to the accretion of blood impurities on its walls. (See Diagram 3.)

The alleged Gambro invention was the first system designed to correct for errors in ultrafiltration measurement by recalibrating flow sensors during dialysis treatment.

C. Prosecution of the Gambro '552 Patent.

The original foreign patent application for Gambro's alleged invention was filed in Sweden on September 28, 1982. In September 1983, Gambro filed, in the United States, the application that led to the Gambro '552 patent here at issue. The original U.S. application was amended a number of times before issuance, in April 1986, of the Gambro '552 patent under the title: "System for the Measurement of the Difference Between Two Fluid Flows in Separate Ducts."

Arnold Krumholz was the American attorney responsible for prosecution of the Gambro '552 patent application. Gunnar Boberg was Gambro's in-house patent attorney responsible for the prosecution.

D. Baxter's Development of its Allegedly Infringing Products.

A separate company, Extracorporeal, Inc., manufactured dialysis equipment during the 1970's and early 1980's. It introduced the SPS 350 dialysis machine in the late 1970's. At that time, the SPS 350 had no ultrafiltration monitoring capability.

By March 1982, Extracorporeal introduced the DM 358 ultrafiltration monitor for use with the SPS 350. The DM 358 used a flowmetric system incorporating two turbine flow sensors, one upstream and one downstream of the dialyzer, for measuring the ultrafiltration rate.

The DM 358, like the Repgreen UFM 1000, provided for flow sensor recalibration before each dialysis treatment (but not during treatment). Recalibration involved disconnecting the dialysate lines from the dialyzer and attaching them to a shunt, or "sanitize/normalize interlock," thus directing the same flow of clean dialysate through both the first and second flow sensors. The DM 358 could then be recalibrated to compensate for any difference in the flow sensor measurements. Because recalibration required disconnecting the dialyzer, the DM 358 was not designed to be recalibrated while a treatment session was ongoing.

In 1984, Baxter acquired the dialysis equipment division of Extracorporeal, and soon thereafter introduced the DM 458 ultrafiltration monitor. Like the DM 358, the DM 458 was not designed to be recalibrated during ongoing treatment.

Baxter was not satisfied with the accuracy of the DM...

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