Addressing for the first time the issue of whether a claim limitation requiring a temperature “within” a recited range includes minor fluctuations outside that range, the U.S. Court of Appeals for the Federal Circuit upheld the district court’s construction and grant of summary judgment of literal infringement. Lexion Medical, LLC. v. Northgate Technologies, Inc., Case Nos. 09-1494, 04-5705 (Fed. Cir., Apr. 22, 2011) (Rader, J.).

The asserted claims were directed to a method of heating gas before it enters a patient during a laparoscopic procedure. The claim at issue contains the following limitation: “having a temperature within 2°C of the predetermined temperature.” The district court found that this limitation did “not require that the temperature range always be within 2°C of the predetermined temperature” because the specification of the asserted patent “discloses that temperatures ‘will, at times, fluctuate outside the four-degree range.’” Because in the accused method the temperature was “almost always” within the claimed 2°C of the predetermined range, the district court granted Lexion Medical summary judgment of literal infringement. Northgate appealed.

The Federal Circuit upheld the district court’s construction and grant of summary judgment of literal infringement. The Federal Circuit explained that other limitations within the claim support the district court’s finding that the claimed invention includes minor fluctuations in temperature outside of the claimed range. The other claim limitations include “sensing the temperature” of the gas, and “actuating the heat means” if the gas temperature is outside of the claimed range. Because these limitations imply that the gas temperature will fluctuate at times, the claimed 2°C range must include some tolerance for this fluctuation. Also, the specification discloses that when the gas passes into the patient, it has a temperature “at least within about 2°C of the predetermined temperature.” As such, the Federal Circuit explained that the specification “discloses that the temperature will at times fluctuate outside of the range.” The Federal Circuit then stated that the term “within,” read in light of the specification and claim language, would tolerate minor fluctuations outside of the recited range. The Federal Circuit held that the phrase “within 2°C of the predetermined temperature” means “within 2°C of the predetermined temperature, subject to minor fluctuations.”

The Federal Circuit next upheld the district court’s finding that there was “no material disputes” of the fact that the accused method “heats and maintains gas as a ‘predetermined temperature’ within the claimed range, allowing for minor fluctuations.” Thus, the Federal Circuit upheld the court’s grant of summary judgment of literal infringement.