Wrist SP BioTech, LLC v. Masimo Corporation

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Wrist SP Biotech, LLC (Delaware)
  • Defendant: Masimo Corporation (Delaware)
  • Plaintiff’s Counsel: Ramey LLP
• Case Identification: 6:23-cv-00632, W.D. Tex., 08/25/2023
• Venue Allegations: Venue is alleged to be proper in the Western District of Texas because the defendant is said to conduct continuous and systematic business in the district, including making the accused products available for sale, advertising to residents, and hiring employees.
• Core Dispute: Plaintiff alleges that Defendant’s neonatal pulse oximeter sensor infringes a patent directed to a pulse oximeter sensor designed for placement on the ulnar (outer) edge of the palm.
• Technical Context: The technology relates to non-invasive biotelemetry, specifically pulse oximetry, a common medical procedure for monitoring blood oxygen saturation levels.
• Key Procedural History: The complaint does not reference any prior litigation, inter partes review (IPR) proceedings, or licensing history related to the patent-in-suit.

Case Timeline

Date	Event
2013-05-20	'015 Patent Priority Date
2022-05-17	'015 Patent Issue Date
2023-08-25	Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

• Patent Identification: U.S. Patent No. 11,331,015, "Pulse oximeter sensor," issued May 17, 2022.
• The Invention Explained:
  • Problem Addressed: The patent asserts that conventional pulse oximeters, typically clipped to a fingertip, suffer from signal inaccuracies caused by patient movement ('015 Patent, col. 1:52-55). Even sensors placed on the wrist are described as being susceptible to signal disruption from wrist flexion and the gripping motion of fingers ('015 Patent, col. 2:6-12).
  • The Patented Solution: To solve this, the invention proposes a pulse oximeter sensor assembly specifically designed for attachment to the "ulnar edge of the palm" ('015 Patent, Abstract). This anatomical location is identified as being "relatively free from motions that interfere with the sensor signals" ('015 Patent, col. 2:7-9). The sensor assembly comprises a light emitter and a detector housed in an elongate body, which is secured to the hand using a layered structure of films and adhesives, as depicted in figures such as FIG. 10, to ensure stable placement ('015 Patent, col. 2:13-22, col. 11:50-63).
  • Technical Importance: This design sought to improve the reliability of pulse oximetry data by moving the sensor from traditionally used, motion-prone sites to a more anatomically stable location on the hand, thereby reducing motion-related artifacts in the readings ('015 Patent, col. 2:6-12).
• Key Claims at a Glance:
  • The complaint asserts independent claim 1 ('Compl. ¶18).
  • The essential elements of independent claim 1, a method claim, include:
    • Attaching a specific pulse oximetry sensor assembly to the "ulnar edge of a palm."
    • The sensor assembly must comprise an "elongate body" containing a light source and a detector.
    • The detector must include an "interference shield" which itself comprises a "copper foil" and a "Faraday cage window."
    • The assembly must include a "skin-contacting film" made of elastomeric material with specific openings for the light source and detector.
    • The assembly must include an "insulating tape" that covers the top surface of the elongate body.
    • The assembly must include a "cover film" made of elastomeric material that has a "transparent window" for visualizing placement.
    • Transmitting signals from the detector to a signal processing unit.
    • Reading output data from the signal processing unit.
  • The complaint reserves the right to assert additional claims ('Compl. ¶18).

III. The Accused Instrumentality

• Product Identification: Masimo's LNCS-NEO-L-3 Pulse Oximeter ('Compl. ¶16).
• Functionality and Market Context: The complaint itself provides minimal technical detail about the accused product's operation, identifying it by name and providing a hyperlink to an external document ('Compl. ¶16). This external document suggests the LNCS-NEO-L-3 is a disposable pulse oximetry sensor intended for use with neonates, for example in screening for congenital heart defects ('Compl. ¶16). The complaint alleges that these products are developed, manufactured, and sold by the Defendant for use in the United States, including within the Western District of Texas ('Compl. ¶¶2, 4).

IV. Analysis of Infringement Allegations

The complaint states that claim charts are attached as Exhibit B; however, this exhibit was not included with the filed complaint document ('Compl. ¶24). The complaint’s narrative allegations are limited to a conclusory statement that the Accused Products infringe at least claim 1 of the ’015 Patent ('Compl. ¶18). Without the claim charts, a detailed analysis of the infringement theory is not possible.

No probative visual evidence provided in complaint.

• Identified Points of Contention: Based on the claim language and the nature of the accused product, the infringement analysis may focus on several key questions:
  • Structural Questions: A primary issue for the court may be whether the physical construction of the accused LNCS-NEO-L-3 sensor meets the highly specific structural limitations of claim 1. For instance, does the Masimo sensor contain an "interference shield" that includes both a "copper foil" and a "Faraday cage window" as distinct components? Does its construction map onto the claim's requirements for separate "skin-contacting film," "insulating tape," and "cover film" layers, each with their own recited features?
  • Locational Questions: As claim 1 is a method claim, infringement requires the sensor to be attached to the "ulnar edge of a palm." A central factual dispute may arise over the intended and actual placement of the accused neonatal sensor. The court will need to consider what evidence exists, such as Defendant's product manuals or standard medical practice, to show that the sensor is used at the specific anatomical location required by the claim, as opposed to other locations on a neonate's hand or foot.

V. Key Claim Terms for Construction

• The Term: "ulnar edge of a palm"

• Context and Importance: This term defines the specific anatomical location for the patented method and is central to the invention's purported novelty. Its construction will determine the geographic scope of the claim on the surface of the hand.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The specification describes the invention as a sensor for attachment to the "lower half of the palm or the ulnar edge of the palm" ('015 Patent, Abstract), and shows various possible placements in this general vicinity (e.g., '015 Patent, Figs. 10-12). This could support an interpretation covering a region, not just a precise line.
  • Evidence for a Narrower Interpretation: Figure 14 and its accompanying description detail a placement relative to specific underlying bones, stating the sensor "lies opposed to the fifth metacarpal 5MC with some overlap of the fourth metacarpal, 4MC, and the hamate H, triquetrum T, lunate L and pisiform P carpal bones" ('015 Patent, col. 4:1-4). This language could be used to argue for a more constrained definition tied to specific skeletal landmarks.

• The Term: "interference shield...comprising: a copper foil; and a Faraday cage window"

• Context and Importance: This limitation recites a detailed, multi-part structure for protecting the sensor's detector. Proving infringement will require showing the accused product contains this exact structure. Practitioners may focus on this term because its specificity presents a high bar for the plaintiff to prove literal infringement.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: A party might argue that any radiofrequency shield made of copper material that incorporates a mesh or opening to allow light to pass to the detector should be considered a "copper foil" with a "Faraday cage window," focusing on the function over the precise form.
  • Evidence for a Narrower Interpretation: The patent depicts the shield (515) and its "Faraday cage window" (515F) as distinct features of a specific embodiment ('015 Patent, col. 10:50-58; Fig. 6). A party could argue that the claim requires two structurally distinct elements—the foil shield itself and a separate, identifiable "window"—and that a simple mesh integrated into a piece of foil would not suffice.

VI. Other Allegations

• Indirect Infringement: The complaint alleges that Defendant induces infringement by its customers and contributorily infringes by supplying a material part of the invention that is not a staple article of commerce ('Compl. ¶19). The pleading offers a general factual basis, alleging that Defendant "supplies the technology that allows its customers to infringe," but does not point to specific user manuals, instructions, or marketing materials that would direct an infringing use ('Compl. ¶19).
• Willful Infringement: The complaint alleges that Defendant "made no attempt to design around the claims" and "did not have a reasonable basis for believing that the claims of the ‘015 Patent were invalid" ('Compl. ¶¶20-21). While the term "willful" is not used, these allegations, along with a request for a finding of an exceptional case under 35 U.S.C. § 285, form a basis for a future willfulness claim ('Compl. p. 7, ¶E). The complaint does not allege any facts supporting pre-suit knowledge of the patent by the Defendant.

VII. Analyst’s Conclusion: Key Questions for the Case

The resolution of this dispute will likely depend on the court's determination of two central issues:

• A core issue will be one of structural correspondence: does the physical construction of the accused Masimo neonatal sensor, a mass-market disposable product, embody the highly detailed, multi-component assembly recited in claim 1, including the specific two-part interference shield, the distinct layered films, and the insulating tape?
• A key evidentiary question will be one of intended use: what evidence demonstrates that the accused sensor is instructed to be, or in practice is, attached to the specific "ulnar edge of a palm" as required by the asserted method claim, particularly given its design for neonatal patients where alternative placements (e.g., a foot) are common?