Why does Inspire (Upper Airway Stimulation) therapy have a different failure threshold than Continuous Positive Airway Pressure (CPAP) therapy for obstructive sleep apnea?

Different Failure Thresholds for Inspire vs. CPAP in Obstructive Sleep Apnea

The different failure threshold for Inspire (Upper Airway Stimulation) compared to CPAP exists because Inspire is specifically positioned as a second-line therapy for patients who have already failed or cannot tolerate CPAP therapy, rather than as a first-line treatment option.

Rationale for Different Thresholds

CPAP as First-Line Therapy

• CPAP remains the gold standard first-line treatment for OSA based on extensive evidence showing its effectiveness in reducing the apnea-hypopnea index (AHI) and improving symptoms 1
• The European Respiratory Society (ERS) guideline makes a conditional recommendation that CPAP should be used over mandibular advancement devices (MADs) due to its superior ability to reduce AHI, particularly in severe OSA 1
• CPAP has been extensively studied with demonstrated efficacy in improving oxygen saturation, reducing arousals, and potentially improving cardiovascular outcomes 2

Inspire as Second-Line Therapy

• The ERS guideline specifically positions hypoglossal nerve stimulation (HNS/Inspire) as a second-line treatment with a "conditional recommendation against HNS as a first-line treatment for OSA patients in general" 1
• The guideline states that HNS "can be used in symptomatic OSA patients who have failed or have not tolerated CPAP treatment" 1
• This positioning creates an inherent difference in failure thresholds, as Inspire is only considered after CPAP has already been attempted and failed

Clinical Implications of Different Thresholds

CPAP Failure Definition

• CPAP failure is typically defined by:
  1. Inability to tolerate the device (mask discomfort, claustrophobia)
  2. Inadequate adherence (typically <4 hours per night for 70% of nights)
  3. Persistent symptoms despite adequate usage
  4. Persistent oxygen desaturations despite optimal pressure settings 3

Inspire Eligibility Criteria

• Inspire therapy is specifically indicated for patients who:
  1. Have moderate to severe OSA (AHI 15-65 events/hour)
  2. Have failed or cannot tolerate CPAP
  3. Meet specific anatomical criteria based on drug-induced sleep endoscopy 1
  4. The indication should follow the inclusion criteria of the STAR trial 1

Evidence Supporting Different Thresholds

Effectiveness Considerations

• CPAP has demonstrated superior AHI reduction compared to other therapies when properly used 1, 2
• However, CPAP adherence is a significant challenge, with compliance rates of 60-70% in real-world settings 4
• Inspire therapy has shown high adherence rates (86% at 12 months) but comes with different risks including infection (34.2%), neuropraxia (15.1%), and hematoma/seroma (11.6%) 5

Practical Implementation

• The different threshold acknowledges the reality that many patients cannot tolerate CPAP despite its theoretical effectiveness
• By positioning Inspire as a second-line therapy, healthcare systems can:
  1. Attempt the most effective and cost-efficient therapy first (CPAP)
  2. Reserve more invasive and costly interventions for those who truly need them
  3. Ensure appropriate patient selection for surgical interventions

Potential Pitfalls in Clinical Practice

Avoiding Premature CPAP Abandonment

• Before declaring CPAP failure, clinicians should ensure:
  1. All mask types and interfaces have been tried (nasal, full-face, nasal pillows)
  2. Pressure settings have been optimized (fixed CPAP vs. auto-CPAP)
  3. Humidification has been appropriately adjusted
  4. Patient education and support have been provided 6

Appropriate Patient Selection for Inspire

• Not all CPAP failures are candidates for Inspire therapy
• Careful anatomical assessment is required to identify suitable candidates
• Patients should understand the risks of surgical complications and device malfunctions that may require reoperation (42.3% of adverse events) 5

Conclusion

The different failure threshold between Inspire and CPAP reflects their distinct positions in the treatment algorithm for OSA. CPAP remains the first-line therapy due to its non-invasive nature and proven efficacy when used properly, while Inspire is reserved for patients who cannot succeed with CPAP despite optimal efforts. This sequential approach ensures that patients receive appropriate escalation of therapy based on their individual response to treatment.