In Resmed Limited et al. v. Fisher & Paykel Healthcare Limited, Case No. IPR2016-01724, the Patent Trial and Appeal Board (PTAB) was presented with a question as to whether several claims of U.S. Patent No. 8,453,641 B2 (hereinafter “the ‘641 patent”) are unpatentable under 35 U.S.C. §103 as obvious over a combination of three references. The ‘641 patent is entitled “Apparatus for Measuring Properties of Gases Supplied to a Patient” and, as provided at column 2, lines 57-62 of the ‘641 patent, its stated purpose is “to measure various properties, for example temperature or humidity, at the end of a gas delivery tube or conduit using sensors mounted on a wire, such as a wire used for heating the gases flow[ing] through the tube or conduit, where the wire resides within the delivery tube or conduit.”

When a combination of prior art references is cited for the purpose of determining that a claim is unpatentable under 35 U.S.C. §103, a showing that a skilled artisan would have been motivated to combine the references in order to achieve the claimed combination is required. The Supreme Court has stated that “a patent composed of several elements is not proved obvious merely by demonstrating that each of its elements was, independently, known in the prior art.” KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 418-19 (2007). Instead, “a range of real-world facts to determine ‘whether there was an apparent reason to combine the known elements in the fashion claimed by the patent at issue'” must be considered. Intercontinental Great Brands LLC v. Kellogg N. Am. Co., 869 F.d 1336, 1344 (Fed. Cir. 2017) (quoting KSR, 550 U.S. at 418).

The critical feature of the challenged claims of the ‘641 patent is the use of a heater wire for heating the conduit and also for carrying electrical signals from measuring sensors. The Petitioner, Resmed, relied on one cited reference, Edirisuriya, as teaching that “the heater wire itself could be used to carry electrical signals from measuring sensors,” although Edirisuriya does not explain how the heater wire can be used to carry electrical signals from a sensor. In response, the Patent Owner argued that a skilled artisan would not have been motivated to combine Edirisuriya with the other two cited references, MR810 and Gradon, because the use of the heater wire to carry electrical signals would have increased complexity and rendered the MR810-Gradon system inoperable. In particular, the Patent Owner argued that a temperature sensor cannot simply be added in series with a heater wire, because the heater wire requires a relatively high electrical current and power dissipation, whereas the temperature sensor requires a relatively low electrical current and power dissipation, and therefore, a simple substitution would lead to self heating.

In its analysis, the PTAB stated that “[w]ith respect to each of the proposed circuit designs that Petitioner contends a skilled artisan would have been aware of to implement the combined teachings, a skilled artisan would have been faced with the real-world fact that there was uncertainty as to the operability of the design,” because the proposed circuit designs “are not based on disclosure in the prior art” – Petitioner’s expert “confirms that he did not locate any prior art references disclosing a circuit design in which the heater wire is utilized to carry electrical signals from measuring sensors” – and because Petitioner did not provide sufficient evidence that any of the proposed circuit designs would be operable in any device.

Conversely, Patent Owner argued that “all three proposed circuit designs would have been inoperable.” In particular, Patent Owner’s expert stated that if the proposed Vishay thermistor was combined with the MR810 apparatus, the power dissipated would exceed the maximum rating of the Vishay thermistor, thereby destroying it, and further, that the Vishay thermistor is not typically used for temperature measurement. Petitioner’s expert agreed that “he would not use the proposed Vishay thermistor in combination with the MR810 heating wire because it would exceed the Vishay thermistor’s power dissipation specification, and that the heater wire and the supply voltage would need to be changed.”

Based on the above, the PTAB found “that the complexity of the proposed circuit designs and the lack of evidence provided by Petitioner describing additional circuitry and control logic that would be necessary to implement such circuitry in the proposed modified designs, which Patent Owner establishes are non-trivial, weigh against a finding of motivation to combine.” As a result, the PTAB held that “the motivation to eliminate an additional or external wire and reduced the number of contacts would have been outweighed by the countervailing real-world reasons not to combine the references,” and that “Petitioner’s challenges rest on impermissible hindsight reconstruction of the disclosure in the ‘641 patent.”

This case illustrates that a challenge to the validity of a patent claim can be effectively countered by the testimony of Patent Owner’s expert that there is no motivation to combine references. In particular, a convincing demonstration that there is uncertainty as to the operability of the proposed combination and/or a showing that practical, real-world considerations tend to weigh against combining the references may be decisive.