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Specification Is Key to Claim Construction

04-1247
April 08, 2005

Decision icon Decision

Last Month at the Federal Circuit - May 2005

Judges: Bryson (author), Newman, and Dyk

In Nellcor Puritan Bennett, Inc. v. Masimo Corp., No. 04-1247 (Fed. Cir. Apr. 8, 2005), the Federal Circuit vacated a district court’s decision granting SJ of noninfringement, because the district court had erred in its claim construction.

Nellcor Puritan Bennett, Inc. (“Nellcor”) owns U.S. Patent No. 4,934,372 (“the ‘372 patent”), which covers a method and apparatus for determining the oxygen-saturation level in blood by processing the signals received from a pulse oximeter. Claim 1 of the ‘372 patent claims a method for calculating the amount of a blood constituent, in which the aperiodic information is “attenuated and filtered” from the composite signal.

On appeal, Nellcor first contended that the district court had erred in construing the phrase “attenuated and filtered” to mean “reduced and removed.” The Federal Circuit agreed. Finding the ordinary dictionary meaning of the term “filtered” to be consistent with Nellcor’s proposed definition, the Federal Circuit focused its analysis on the specification of the ‘372 patent and observed that the process described in the ‘372 patent does not actually remove data. Rather, the invention covered by the ‘372 patent merely results in the suppression of aperiodic noise relative to the periodic signal. Therefore, the Court concluded that the term “attenuated and filtered” means constantly reducing the level of aperiodic signals, rather than removing unwanted data all together.

The Federal Circuit noted that the district court’s reliance on the ‘372 patent’s prosecution history to support its interpretation of the terms was misplaced because the district court had misconstrued the reasons for applicants’ amendments to the claims.

The Federal Circuit also agreed with Nellcor’s contention that the district court had erred in ruling that the claims require a calculation using the relative minimum only after formation of a composite signal. The Court determined that, based on one embodiment in the ‘372 patent specification, the relative minimum, or the zero frequency, is computed when the average value of the signal is determined. Since the average value of the signal is an essential component in the computation of the composite signal, calculation of the relative minimum necessarily occurs before the formation of the composite signal.