## Facts

- Gambro owned U.S. Patent No. 4,585,552 covering a hemodialysis system that measures the difference between two fluid flows in separate ducts to determine ultrafiltrate removed.
- The patent’s central feature was recalibrating (zeroing) flow sensors during dialysis to correct drift and clogging that made earlier systems increasingly inaccurate.
- Repgreen Limited developed an earlier monitor (UFM 1000) using two sensors calibrated before treatment; its designer, Keith Wittingham, later met with Gambro engineers in 1979.
- After Repgreen went bankrupt, Gambro purchased its hemodialysis technology; Wittingham also prepared a proposal describing an “Auto Zero/Start” concept focused on automatically zeroing before automatically starting dialysis, with an ambiguous reference to a possible independent zero function.
- Baxter manufactured and marketed an ultrafiltration monitoring device; Gambro sued for infringement, and Baxter asserted invalidity and unenforceability based on derivation, prior art, and alleged inequitable conduct.

## Issues

1. Whether clear and convincing evidence showed Gambro derived the complete claimed invention from Wittingham/Repgreen.
2. Whether Repgreen’s system or Wittingham’s proposal anticipated or rendered obvious the claimed in-treatment recalibration system.
3. Whether Gambro committed inequitable conduct before the PTO through nondisclosure or mischaracterization of Wittingham’s work.
4. Whether, under correct claim construction, Baxter’s device infringed the asserted claims.

## Decision

- The Federal Circuit reversed the district court’s judgment that the ’552 patent was invalid, unenforceable, and not infringed.
- The court held the district court misapplied derivation standards and lacked adequate evidentiary support for finding the claimed invention was obtained from Wittingham.
- The court rejected the district court’s anticipation and obviousness analyses because the cited prior art did not clearly disclose the claimed in-treatment recalibration and the analysis did not properly account for the claim limitations.
- The court reversed the inequitable-conduct finding for failure to establish, by clear and convincing evidence, both materiality and intent to deceive.
- The court found errors in claim construction and infringement analysis and remanded for further proceedings consistent with the corrected legal framework.

## Legal Principles

- Derivation requires clear and convincing proof that the patentee obtained the complete conception of the claimed invention from another; generalized ideas or related technology are insufficient.
- Anticipation requires a single prior art reference to disclose every claim element arranged as in the claim.
- Obviousness must be evaluated against the specific claim limitations and technical context; identifying a known problem does not, by itself, establish that a particular claimed solution would have been obvious.
- Inequitable conduct requires clear and convincing proof of both materiality and specific intent to mislead or deceive the PTO.
- Correct claim construction is necessary for reliable validity and infringement determinations; errors in prior-art characterization can distort claim interpretation and the infringement comparison.

## Conclusion

The Federal Circuit reversed because the record and governing standards did not support findings that Gambro’s invention was derived from prior work, anticipated or obvious over the cited technology, or procured through inequitable conduct, and because claim construction and infringement analysis required reconsideration on remand.


Gambro Lundia AB v. Baxter Healthcare Corp., 110 F.3d 1573 (Fed. Cir. 1997)