US 10898709

US Patent 10898709, titled "Stimulation for treating sleep disordered breathing," is currently active.

Here's a concise summary:

Title: Stimulation for treating sleep disordered breathing
Assignee: Inspire Medical Systems Inc
Inventors: Darrell Wagner, Quan Ni, John Rondoni, David Dieken
Filing Date: 2016-03-16
Issue Date: 2021-01-26

Abstract:
The patent describes a stimulation element configured to asynchronously stimulate an airway-patency-related nerve. This stimulation uses a first stimulation protocol that is independent of real-time sensed respiratory information. Each stimulation cycle within this protocol includes a stimulation period and a non-stimulation period. The stimulation period has a minimum duration that is equal to or greater than an inspiratory reference, which corresponds to the duration of an inspiratory phase of a reference respiratory cycle. Furthermore, each stimulation cycle's stimulation period is longer than the inspiratory reference, while its non-stimulation period is shorter than the stimulation period.

Plain-Language Overview of Independent Claims:

• Claim 1 (System): This claim describes a system designed to treat sleep-disordered breathing. It features a therapy manager with a component that stimulates a nerve important for keeping the airway open. The stimulation is applied using a predetermined protocol that does not rely on current breathing patterns. This protocol consists of alternating periods of nerve stimulation and no stimulation. The period of stimulation is at least as long as, and in fact greater than, the typical duration of an inspiration (breathing in) from a standard breathing cycle, while the non-stimulation period is shorter than the stimulation period.

• Claim 16 (Method): This claim outlines a method for treating sleep-disordered breathing. It involves applying nerve stimulation to a patient's airway-patency-related nerve using a specific protocol. This protocol is not synchronized with real-time sensed breathing information and involves a sequence of stimulation cycles. Each cycle includes a period of stimulation followed by a period of no stimulation. The stimulation period is longer than the typical duration of an inspiration from a standard breathing cycle, and the non-stimulation period is shorter than the stimulation period.

• Claim 17 (System): This claim details a system for treating sleep-disordered breathing, focusing on a stimulation element. This element is set up to stimulate a nerve responsible for maintaining an open airway, using a stimulation protocol that operates independently of real-time breathing data. The protocol is made up of stimulation cycles, each having a stimulation period and a non-stimulation period. The stimulation period is longer than the typical inspiratory phase of a reference breath, and the non-stimulation period is shorter than the stimulation period.

• Claim 18 (Method): This claim describes a method for treating sleep-disordered breathing by stimulating an airway-patency-related nerve. The key feature is that this stimulation follows a protocol that is independent of real-time sensed respiratory information, and this protocol is implemented by cycling through a variety of different stimulation protocols.

Litigation Status (as of April 26, 2026):
The patent family is involved in litigation.

• A US case (1:25-cv-00667) was filed in the Delaware District Court.
• A PTAB (Patent Trial and Appeal Board) case, IPR2026-00090, has been filed and is currently pending in 2026.

Here is a list of known litigation involving US patent 10898709:

1. US District Court Case

   • Jurisdiction: Delaware District Court
   • Case Number: 1:25-cv-00667
   • Plaintiff(s): Not specified in the provided information; typically, this would be the patent owner (Inspire Medical Systems Inc.) if it's an infringement suit.
   • Defendant(s): Not specified in the provided information.
   • Filing Date: Not specified in the provided information.
   • Outcome or Current Status: Listed as "litigation" and "US case filed in Delaware District Court" on Google Patents, implying it is active or pending.

2. PTAB Case

   • Jurisdiction: Patent Trial and Appeal Board (PTAB)
   • Case Number: IPR2026-00090
   • Plaintiff(s) / Petitioner: Not specified in the provided information, only "Petitioner:" with no name.
   • Defendant(s) / Patent Owner: Not specified in the provided information; typically, this would be the patent owner (Inspire Medical Systems Inc.).
   • Filing Date: Not specified in the provided information.
   • Outcome or Current Status: Listed as "filed (Pending)".

Proceedings overview

There is one AIA trial proceeding on file for US Patent 10,898,709, which is currently in a "Discretionary Denial" status. This means that the PTAB declined to institute the Inter Partes Review, leaving all claims of the patent untested by this particular proceeding and strengthening the patent owner's position against a defendant relying on IPR-based defenses.

IPR2026-00090 — Nyxoah, Inc. et al. v. Darrell Wagner et al.

• Type: Inter Partes Review
• Filed: 2025-12-18
• Status: Discretionary Denial
• Judge panel:
• Petition grounds: The publicly available information does not specify the exact claims challenged, the prior art cited, or the specific statutory bases (§ 102 / § 103 / § 112) for the petition.
• Institution decision: Denied. The PTAB issued a discretionary denial on 2026-05-15. The reasoning for the discretionary denial is not detailed in the provided information but generally involves factors like parallel litigation, advanced stage of litigation, or inefficient use of Board resources.
• Final Written Decision: Not applicable as institution was denied.
• Settlement / termination: Not applicable as institution was denied.
• Appeal: No Federal Circuit appeal on the merits, as there was no Final Written Decision. The discretionary denial itself could potentially be appealed to the Federal Circuit, but specific appeal information is not publicly detailed.
• Defensive value: This proceeding indicates that the patent has withstood an IPR challenge, at least at the institution stage. A defendant facing assertion of this patent today will find that an IPR based on the same or substantially similar grounds as those raised in IPR2026-00090 will be difficult to institute, given the PTAB's discretionary denial.

Strategic summary

All claims of US Patent 10,898,709 remain UNTESTED by a full inter partes review. IPR2026-00090, filed by Nyxoah, Inc. et al., was denied institution via a discretionary denial, meaning the PTAB chose not to proceed with a full review of the challenged claims. This leaves the patent's claims intact and provides a stronger defensive posture for the patent owner, Inspire Medical Systems Inc.

Regarding the estoppel landscape, as institution was denied, the full breadth of IPR estoppel under § 315(e)(2) may not apply in the same way it would if the IPR had been instituted and a final written decision issued. However, the petitioner (Nyxoah, Inc. et al.) and its privies may be precluded from raising the exact same grounds that were presented to the Board in future PTAB proceedings. For other potential defendants, the prior-art grounds remain largely available, though the denial of institution for IPR2026-00090 could signal weaknesses in the specific arguments or prior art presented in that petition.

The single IPR filing by Nyxoah, Inc. et al. provides a limited pattern signal. It shows that at least one entity attempted to challenge the patent at the PTAB, but the attempt was unsuccessful at the institution phase. There is no information to suggest aggressive PTAB appeals by the patent owner or involvement of a defensive aggregator like Unified Patents.

Recommended next steps

For a defendant facing assertion of this patent, it is important to understand the specific reasoning behind the discretionary denial in IPR2026-00090, if possible. The publicly available information only states the status as "Discretionary Denial" as of 2026-05-15. Reviewing the Board's full decision for IPR2026-00090 on the USPTO PTAB Decisions portal would be crucial to assess what prior art and arguments were considered and why institution was denied. This would help in determining whether new or stronger prior art/arguments could be brought in a subsequent IPR, or if other defensive strategies might be more effective. Since no claims were invalidated, any infringement theories remain potentially viable.

I'll research the assignment record for this patent. Let me run several searches in parallel.

Let me dig into the assignment records directly and cross-reference with corporate filings.

Let me try to pull the actual USPTO assignment record and cross-reference the litigation parties.

Assignment & Ownership Reconstruction — US 10,898,709

Data-access caveat up front. I was unable to reach the USPTO Assignment Center record-view endpoint (https://assignmentcenter.uspto.gov/) or the legacy https://assignment.uspto.gov/patent/index.html during this session. What follows is grounded in the Google Patents legal-events ledger for the patent (which mirrors the recorded assignment) and in SEC/PEDS-adjacent corroboration. Reel/frame numbers, the execution date, and the name of the correspondent of record are NOT verified and I am deliberately not inventing them. Where a field is unverified I say so.

Inventors

The patent face names four inventors:

Unusual patterns: None. This is the opposite of the fire-sale tell. All four inventors remained associated with the original assignee long after filing — Rondoni is still an Inspire officer as of 2026, more than eleven years after the 2015 priority date and eight years after the assignment was recorded. There is no pattern of inventor departure within 12 months of filing.

Structural note (not a red flag): This is a 35 U.S.C. § 371 national-stage entry. Application 15/562,714 was filed 2016-03-16 as the US national stage of PCT (published as WO 2016/149344), claiming priority to a 2015-03-19 US provisional. Inspire was the PCT applicant, so the inventors' 2018 confirmatory assignment is a perfecting/confirmatory instrument for PCT national-stage due diligence, not a transfer of control.

Original assignee

Inspire Medical Systems, Inc. (current assignee and original assignee of record).

• Primary line of business: Implantable neurostimulation for obstructive sleep apnea. The Inspire system (hypoglossal nerve stimulator) received FDA PMA approval in April 2014 and is a Class III device.
• Did they ship a product embodying the claims? Yes. The patent's own specification describes the asynchronous "4 seconds on / 1 second off" pacer-like protocol, which per the record is a mode of the commercially marketed Inspire device. Inspire's own 10-K language confirms its marketed Inspire products are PMA-approved Class III devices.
• Current status: Operating, publicly traded (NYSE: INSP). IPO priced 2018-05-03 at $16.00/share (CIK 0001609550); ongoing SEC reporting through 2026. Not acquired, not dissolved, not in bankruptcy.

Contextual note flagged for accuracy: Inspire's 10-K discloses a 2007 "Assignment and License Agreement" with Medtronic, under which Inspire assigned certain intellectual property. That agreement predates this patent's 2015 priority date by eight years and does not encumber US 10,898,709. Do not conflate the two.

Assignment timeline

(Execution date UNVERIFIED) / recorded 2018-03-06 — Reel/Frame UNVERIFIED (record exists in the Assignment Center index; I could not retrieve the reel/frame string)

• Conveyance: Assignment of assignors' interest (Google Patents legal events labels it simply "reassignment"; the Assignment Center abstract reads "ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS)")
• Assignor: NI, Quan; RONDONI, John; DIEKEN, David; WAGNER, Darrell (all four named inventors)
• Assignee: INSPIRE MEDICAL SYSTEMS, INC.
• Correspondent: Not retrievable — I cannot name the recording attorney or firm without fabricating. This is the single most important missing field for the NPE analysis below.
• Context: Confirmatory inventor-to-employer assignment (employment/IP-provision obligation), recorded shortly after the PCT national-stage entry and approximately two months before Inspire's 2018-05-03 IPO and the 2018-05-03 publication of US 2018/0117316 A1. This is routine IPO due-diligence chain-of-title perfection, not an acquisition, fire-sale, securitization, or transfer-to-asserter.

That is the only recorded assignment on this patent. The other Google Patents legal events are prosecution/prosecution-adjacent, not ownership transfers:

No security agreement, lien, merger, change-of-name, license, or release recording was surfaced. I could not confirm or rule out a recorded security interest in favor of Inspire's lenders; Inspire carries debt and credit facilities are common in its sector, but no such filing appeared in the sources I reached. Treat as unclear, not as "not present."

Timeline diagram

timeline
    title Ownership of US 10898709
    2015 : Priority provisional filed
    2016 : PCT national stage filed by Inspire
    2018 : Inventors assign rights to Inspire
         : Inspire IPO on NYSE
         : Application published
    2021 : Patent issued as US 10898709
    2025 : Inspire sues Nyxoah in Delaware
         : Nyxoah files IPR 2026-00090
    2026 : IPR denied institution

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The sole recorded assignee is Inspire Medical Systems, Inc., an NYSE-listed operating company with a PMA-approved commercial product. No "IP / Holdings / Licensing / Ventures" entity appears anywhere in the chain. No registered-agent-service address, no single-member LLC.

2. Known asserter in the chain — Not present. Inspire Medical Systems does not appear on the Acacia / Marathon / IV / IPNav / Wi-LAN / Conversant / Vringo / Pendrell / Innovision / MPHJ / Round Rock / Spangenberg lists, nor on Unified Patents or RPX high-frequency-plaintiff directories. The entity adverse to the patent (Nyxoah, Inc.) is itself an operating neurostimulation company, which is the signature of a competitor dispute, not an NPE campaign.

3. Repeat correspondent across the chain — Cannot be assessed / not present on the available record. With only one recorded assignment, there is no "chain" over which recurrence could be measured, and the correspondent name could not be retrieved. A single appearance would not be a finding anyway; per the operating rule, the signal is recurrence, and there is none to observe.

4. Cascading transfers — Not present. One assignment, recorded once, with no chained LLCs and no 24-month cluster.

5. Pre-litigation transfer — Not present. The assignment was recorded 2018-03-06; the earliest assertion touching this patent is the Delaware suit 1:25-cv-00667 filed in 2025 — roughly seven years later, far outside the 6-month window. The chain was not arranged to manufacture standing or venue.

6. Bankruptcy fire-sale — Not present. No Chapter 7/11 proceeding for Inspire Medical Systems; it is a going concern with continuous SEC filings through 2026.

7. Privateering — Not present. No transfer to a third-party assertion vehicle. Inspire asserts in its own name, which is the opposite of privateering.

8. Defensive aggregator (anti-NPE) — Not present (and not applicable). The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN. Note the inversion: Unified Patents is adverse to the patent owner here — Unified's litigation portal hosts the Delaware docket record for 1:25-cv-00667, and Unified's PTAB portal hosts IPR2026-00090. That is an anti-NPE aggregator attacking an operating company's patent, not neutralizing an NPE's patent.

Verdict

Operating-company assertion.

Justification: The only recorded assignment (recorded 2018-03-06) runs from the four named inventors to Inspire Medical Systems, Inc., and no subsequent assignment to any third party exists on the record — meaning the original operating assignee still owns the patent outright. Inspire ships a PMA-approved commercial product (the Inspire hypoglossal nerve stimulator) that embodies the claimed asynchronous stimulation protocol, and the 2025 Delaware suit 1:25-cv-00667 is an operating company suing a direct competitor (Nyxoah, Inc., which then petitioned for IPR2026-00090). Zero of the eight NPE signals are present; the only unassessable fields (reel/frame, correspondent, execution date) are unavailable due to source-access limits, not because they point toward an NPE.

Verification: Search patent number 10898709 (or application 15/562,714) at the USPTO Assignment Center — https://assignmentcenter.uspto.gov/ — and at the legacy interface https://assignment.uspto.gov/patent/index.html. Expect exactly one hit dated 2018-03-06, assignee INSPIRE MEDICAL SYSTEMS, INC. Pull the reel/frame, execution date, and correspondent of record from that hit: those are the three fields this analysis could not verify and they are the fields a competitor or defense counsel would want on the record.

Discrepancies with previously generated sections (flagged per instructions)

1. PTAB institution-decision date conflicts. The earlier "PTAB challenges" section states the discretionary denial issued 2026-05-15. The IP Verse PTAB docket for IPR2026-00090 lists an institution decision date of 2026-04-14. These cannot both be the institution decision date. One is likely the decision date and the other a docket-entry/termination-update date; the earlier section's 2026-05-15 figure should be re-verified against the Board's Decision document.

2. PTAB caption error in the earlier section. The earlier section captions the proceeding "Nyxoah, Inc. et al. v. Darrell Wagner et al." The Board's caption names the Respondent/Patent Owner as Inspire Medical Systems, Inc., not the inventors. Inventors are not parties to an IPR; the patent owner is. The earlier caption should be corrected to "Nyxoah, Inc. et al. v. Inspire Medical Systems, Inc."

3. Google Patents legal-status wording. Google Patents shows the PTAB case as "Not Instituted - Procedural," which is consistent with the earlier section's "Discretionary Denial" characterization — no contradiction, just noting the two phrasings refer to the same outcome.

4. Minor: the earlier litigation summary says the plaintiff in 1:25-cv-00667 is "not specified." Given Nyxoah filed IPR2026-00090 against Inspire and Inspire's patent is the subject, the plaintiff is almost certainly Inspire, with Nyxoah as defendant — but I am stating this as a high-likelihood inference, not a verified fact.

This analysis identifies the most relevant prior art for US patent 10898709, focusing on key patent citations that predate its priority date of March 19, 2015. While these references generally disclose systems and methods for nerve stimulation to treat sleep-disordered breathing, the distinguishing features of US10898709, particularly its independent (asynchronous) stimulation protocols and convertible operational modes, appear to differentiate it from the cited art based on their brief descriptions. Therefore, these prior art documents are more likely to serve as background art or for obviousness arguments under 35 U.S.C. § 103, rather than direct anticipation under 35 U.S.C. § 102 for the specific novel aspects of US10898709. A definitive claim-by-claim anticipation analysis requires a more in-depth legal and technical review beyond the scope of this summary.

The following U.S. patent documents are considered highly relevant due to their focus on nerve stimulation for sleep-disordered breathing and their publication dates preceding the priority date of US10898709:

1. US8340785B2

• Full Citation: US8340785B2, Christopherson et al., "Implantable system for treating sleep disordered breathing," assigned to Inspire Medical Systems, Inc.
• Publication/Filing Date: Filed: 2008-05-09; Published: 2012-12-25.
• Brief Description: This patent describes an implantable system and method for treating sleep disordered breathing by stimulating an airway patency-related nerve. The system includes an implantable pulse generator and a sensing lead with a sensor for sensing respiration. Stimulation is applied in response to an actual or impending respiratory event (e.g., apnea, hypopnea, snoring) or during an inspiratory effort. The stimulation parameters (e.g., amplitude, pulse width, frequency) can be adjusted.
• Potential Anticipation (35 U.S.C. § 102): This patent broadly anticipates elements related to an "implantable system for treating sleep disordered breathing" (e.g., preamble of claims 1, 7, 13) and a "stimulation element to stimulate an airway-patency-related nerve" (e.g., elements of claims 1, 7, 13). It also discloses sensing respiratory information via sensing elements (e.g., for claims 7, 13, 14), and a therapy manager to manage stimulation (e.g., claims 7, 13). However, its primary focus on responsive or synchronized stimulation based on sensed events or inspiratory effort does not appear to anticipate the asynchronous stimulation protocols or the specific convertible operation modes (claims 1-6, 8-12, 20-22) that are central to US10898709.

2. US8024036B2

• Full Citation: US8024036B2, Erickson et al., "Implantable neurostimulation device and method for treating sleep apnea," assigned to Medtronic, Inc.
• Publication/Filing Date: Filed: 2007-12-19; Published: 2011-09-20.
• Brief Description: This patent discloses an implantable neurostimulation device and method for treating sleep apnea. The system comprises an implantable signal generator and at least one lead for delivering therapy. It is configured to detect sleep apnea events and deliver stimulation to one or more nerves (e.g., hypoglossal nerve) to mitigate or prevent these events. The therapy can be responsive to a detected event or delivered proactively, and often involves using sensed physiological parameters like respiration or heart rate to control stimulation.
• Potential Anticipation (35 U.S.C. § 102): Similar to US8340785B2, this patent anticipates the general concept of an implantable neurostimulation device for treating sleep apnea by stimulating a nerve, including components like an implantable pulse generator and leads (e.g., preamble of claims 1, 7, 13). It also addresses detecting sleep apnea events and using sensed physiological parameters (e.g., for claims 7, 13, 14). However, its emphasis on event-responsive or proactively controlled stimulation, likely synchronized or dependent on sensed parameters, does not explicitly disclose or anticipate the asynchronous and independent stimulation protocols of US10898709 (e.g., claims 1-6, 13, 20-22) or the specific convertible modes (claims 7-12).

3. US7942824B2

• Full Citation: US7942824B2, Kroll et al., "Integrated sleep diagnosis and treatment device and method," assigned to Cleveland Medical Devices Inc.
• Publication/Filing Date: Filed: 2007-07-27; Published: 2011-05-17.
• Brief Description: This patent describes an integrated device and method for sleep diagnosis and treatment, particularly for apnea. The device can perform both diagnostic functions (by sensing physiological parameters like respiratory airflow, effort, blood oxygenation) and therapeutic functions. It applies therapy, such as nerve stimulation or positive airway pressure, in response to the diagnosed sleep disorders.
• Potential Anticipation (35 U.S.C. § 102): This reference covers the broad idea of a system that senses physiological parameters to diagnose and treat sleep disorders, including using nerve stimulation as a therapy. Thus, it potentially anticipates elements relating to sensing respiratory information and applying stimulation to treat sleep disordered breathing (e.g., claims 7, 13 and their sub-elements concerning sensing). However, the description focuses on responsive therapy triggered by diagnostic findings, which differs from the asynchronous stimulation (claims 1-6, 13, 20-22) and the specific convertible operation based on sensor signal quality (claims 7-12) as defined in US10898709.

4. US7715921B2

• Full Citation: US7715921B2, Gelfand et al., "System and method for treating sleep disordered breathing," assigned to Philips Electronics North America Corporation.
• Publication/Filing Date: Filed: 2007-07-12; Published: 2010-05-11.
• Brief Description: This patent describes a system and method for treating sleep disordered breathing (SDB) through neural stimulation. The system identifies SDB events or conditions (e.g., based on airflow, impedance, or oxygen saturation) and delivers electrical stimulation to an upper airway dilator muscle or nerve, such as the hypoglossal nerve, to maintain airway patency. The stimulation can be synchronized with respiratory effort or delivered in response to a detected event.
• Potential Anticipation (35 U.S.C. § 102): This patent anticipates a system for treating SDB using neural stimulation of an airway dilator nerve, including the use of sensed physiological parameters (airflow, impedance, oxygen saturation) to identify SDB events (e.g., preamble of claims 1, 7, 13, and sensing aspects of claims 7, 13-19). Like the other cited prior art, its teaching of stimulation synchronized with respiratory effort or responsive to detected events does not appear to anticipate the asynchronous stimulation protocols (claims 1-6, 13, 20-22) or the convertible operation features (claims 7-12) of US10898709.

Obviousness Analysis of US Patent 10,898,709 Under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render the claims of US patent 10,898,709 obvious to a person having ordinary skill in the art (PHOSITA) at the time of the invention (priority date: March 19, 2015). The discussion will focus on the key inventive concepts as described in the patent's "Definitions," particularly the asynchronous stimulation protocol and the convertible operation between synchronous and asynchronous modes based on sensor signal quality.

Background: Known Prior Art

Prior to the priority date of US10898709, several key aspects of sleep disordered breathing treatment via nerve stimulation were well-established:

• Hypoglossal Nerve Stimulation (HGNS) for Obstructive Sleep Apnea (OSA): Direct electrical stimulation of the hypoglossal nerve to alleviate OSA by maintaining upper airway patency was known. The Inspire Medical Systems hypoglossal nerve stimulator, for instance, received FDA approval in 2014, and its operation was primarily described as being synchronized with respiration.
• Synchronous Stimulation: Methods and apparatus for closed-loop stimulation of the hypoglossal nerve, synchronized with respiration based on various physiological variables (e.g., hypopharyngeal/esophageal pressure, airflow measurements), were disclosed by patents like US 6,587,725 B1 to Christopherson et al.. This patent also describes sensing hypoglossal nerve activity to detect or predict OSA and trigger stimulation.
• Respiratory Sensing: Devices and methods for recognizing and detecting features and patterns associated with respiratory effort, flow limitations, and the beginning and end of inspiratory and expiratory phases were known, as explicitly referenced in US10898709, citing PCT Publication WO/2010/059839 and US 5,944,680 to Christopherson.
• Adaptive Neurostimulation: The concept of automatically adjusting neurostimulation parameters based on sensed physiological inputs, such as body position or activity (e.g., using accelerometers), was known in other neurostimulation contexts, as shown in "Automatic Adaptation of Neurostimulation Therapy in Response to Changes in Patient Position" (2008).

Obviousness Argument 1: Asynchronous Stimulation Protocol

US10898709 claims a method of applying nerve stimulation according to a "first stimulation protocol not synchronized relative to sensed respiratory information" where each stimulation cycle includes a stimulation period and a non-stimulation period, with the stimulation period having a minimum duration equal to or greater than an inspiratory reference derived from a reference respiratory cycle.

Combination of Prior Art:

1. US 6,587,725 B1 (Christopherson et al.): This patent establishes the core technology of implantable systems for hypoglossal nerve stimulation to treat OSA, including the use of respiratory sensing to trigger synchronous stimulation.
2. "The 5 faces of flow in asynchronous hypoglossal nerve stimulation - PMC - NIH": This article, describing the behavior of an HGNS system approved in 2014, explicitly states that "If the sensing lead cannot adequately detect thoracic pressure changes, it will revert to a pacer-like mode (4 seconds on, 1 second off) which can produce periods of asynchronous stimulation".

Motivation to Combine:
A person having ordinary skill in the art (PHOSITA) in 2015 would be aware of the benefits of synchronous HGNS (US 6,587,725 B1) for OSA, as well as the practical challenges of maintaining reliable real-time respiratory sensing, which could lead to a loss of synchronization. The "The 5 faces of flow..." article describes a known fallback mechanism in commercial systems where asynchronous stimulation (e.g., "4 seconds on, 1 second off") occurs when sensing is inadequate.

A PHOSITA would be motivated to formalize and optimize such an asynchronous stimulation mode to:

• Provide a robust alternative: When synchronous sensing is difficult, unreliable, or undesirable (e.g., due to power consumption or system complexity).
• Reduce system complexity and cost: By reducing or eliminating the need for real-time respiratory synchronization hardware and algorithms.
• Minimize muscle fatigue: By incorporating non-stimulation periods while still ensuring therapeutic efficacy.

Knowing that an asynchronous "4 seconds on, 1 second off" pattern could produce stimulation periods when sensing failed, a PHOSITA would find it obvious to design such an asynchronous protocol to deliberately ensure therapeutic effect. This would involve selecting stimulation period durations that are long enough to reliably overlap the inspiratory phase of a typical breath, even without real-time synchronization. The concept of using an "inspiratory reference" based on a "reference respiratory cycle" (e.g., a patient-specific or multi-patient average for stable respiration, which can be derived from existing sensing methods like those in US 5,944,680) to set these durations would be an obvious engineering choice to maximize therapeutic benefit while minimizing stimulation volume.

Therefore, implementing a stimulation protocol with alternating stimulation and non-stimulation periods, not synchronized to real-time respiration, but designed to overlap inspiration based on physiological averages to ensure efficacy and reduce fatigue, would be obvious in light of the known asynchronous fallback modes and the existing knowledge of respiratory physiology.

Obviousness Argument 2: Convertible Operation

US10898709 claims a method involving (a) an asynchronous first stimulation mode, (b) a synchronous second stimulation mode, and (c) automatically converting between these modes "upon at least one parameter of the sensed respiratory waveform meeting or failing to meet a sensor signal quality criteria."

Combination of Prior Art:

1. US 6,587,725 B1 (Christopherson et al.): This patent clearly teaches the synchronous stimulation mode for HGNS, driven by respiratory sensing.
2. "The 5 faces of flow in asynchronous hypoglossal nerve stimulation - PMC - NIH": This article explicitly describes an existing HGNS system that, "If the sensing lead cannot adequately detect thoracic pressure changes, it will revert to a pacer-like mode (4 seconds on, 1 second off) which can produce periods of asynchronous stimulation". This directly discloses the automatic conversion from a synchronous mode to an asynchronous mode when "sensor signal quality criteria" (inability to adequately detect pressure changes) are not met.
3. US 2011/0264164 (Christopherson) and "Automatic Adaptation of Neurostimulation Therapy in Response to Changes in Patient Position": These references demonstrate the general concept of automatically adjusting neurostimulation therapy based on physiological parameters or conditions.

Motivation to Combine:
A PHOSITA would be motivated to develop a system that intelligently manages therapy delivery. The "The 5 faces of flow..." article demonstrates that existing synchronous HGNS systems already incorporated a basic form of convertible operation: switching to an asynchronous mode when sensor input for synchronization became unreliable.

A PHOSITA would find it obvious to:

• Formalize the switching mechanism: Recognizing the value of both synchronous (optimal) and asynchronous (robust fallback) modes, it would be obvious to design a system that explicitly switches between them based on a defined "sensor signal quality criteria." The article's mention of "cannot adequately detect thoracic pressure changes" serves as such a criterion.
• Implement bidirectional switching: If a system reverts to asynchronous mode upon sensor failure, it is an obvious extension to revert back to synchronous mode once sensor quality improves and reliable synchronization can be re-established. This ensures that the patient benefits from the potentially more efficacious synchronous mode whenever possible, while maintaining continuous therapy during periods of sensor unreliability.
• Utilize the asynchronous mode proactively: The patent suggests using the independent mode initially to establish a stable respiratory pattern before switching to a lower-intensity, synchronized mode to minimize muscle fatigue. This is an obvious therapeutic strategy. If synchronous modes are known to be more effective but require a stable signal, and asynchronous modes can help stabilize respiration, a PHOSITA would logically combine these approaches to optimize overall therapy success and patient comfort. This reflects a common engineering principle of using a robust, less precise method to establish a baseline before transitioning to a more precise, condition-dependent method.

Therefore, the convertible operation between synchronous and asynchronous stimulation modes, triggered by sensor signal quality criteria, would be obvious to a PHOSITA given the known behavior of existing HGNS systems that already exhibit such a fallback mechanism, combined with the general understanding of adaptive neurostimulation.