How to manage patients with high Apnea-Hypopnea Index (AHI) despite Continuous Positive Airway Pressure (CPAP) therapy?

Management of High AHI Despite CPAP Therapy

For patients with persistently high Apnea-Hypopnea Index (AHI) despite CPAP therapy, a systematic approach including pressure adjustment, mask optimization, and consideration of alternative positive airway pressure modalities is recommended as the first-line management strategy. 1

Initial Assessment

When faced with high residual AHI despite CPAP therapy:

1. Verify CPAP adherence and usage patterns:

   • Download compliance data to objectively assess usage patterns 1
   • Target minimum usage of >4 hours/night on 70% of nights during a consecutive 30-day period 1
   • Check if patient is using CPAP whenever sleeping (day or night)

2. Evaluate technical factors:

   • Mask fit and leakage: Check for excessive mask leak (thresholds vary by manufacturer) 1, 2
     • ResMed: <24 L/min (nasal), <36 L/min (full face)
     • Fisher & Paykel: <60 L/min (full face)
     • DeVilbiss: <95 L/min (full face)
   • Pressure settings: Inadequate pressure is a common cause of persistent high AHI 2

Pressure Adjustment

Pressure modification is the most effective intervention for improving both compliance and AHI control, increasing CPAP use by >30 minutes per night 2. Consider:

• Increasing pressure in 1-2.5 cm H₂O increments when:
  • ≥2 obstructive apneas are observed in adults
  • ≥1 hypopnea is observed
  • ≥3 minutes of loud/unambiguous snoring is observed 1
• After control of respiratory events is achieved, pressure may be increased by up to 5 cm H₂O to normalize airway resistance 1

Alternative PAP Modalities

If optimizing standard CPAP fails:

1. Bilevel Positive Airway Pressure (BPAP):

   • Consider for patients requiring high CPAP pressures (>15 cm H₂O)
   • Shows better adherence and improved symptom control compared to CPAP in some patients 1

2. Adaptive Servo-Ventilation (ASV):

   • For patients with complex sleep apnea or central sleep apnea components
   • CAUTION: ASV is contraindicated in patients with heart failure with reduced ejection fraction (HFrEF) as it may increase cardiovascular mortality 3

3. Auto-titrating PAP (APAP):

   • May improve comfort by providing variable pressure based on need
   • Be aware that pressure-relief features may reduce efficacy if not properly adjusted 4

Special Considerations

Central Sleep Apnea/Treatment Emergent Central Apnea

For patients developing central apneas after CPAP initiation:

• Consider a backup rate (ST mode) for patients with central hypoventilation or significant central apneas 3
• Starting backup rate should equal or be slightly less than spontaneous sleeping respiratory rate (minimum 10 bpm) 3
• Increase backup rate in 1-2 bpm increments every 10 minutes if goals not attained 3

Obesity Hypoventilation Syndrome (OHS)

For obese patients with persistent hypercapnia:

• Consider arterial blood gas analysis to evaluate for OHS, especially in patients with BMI >35 kg/m² 1
• If OHS is present, BPAP may be more effective than CPAP 3

Supplemental Oxygen

• Add supplemental oxygen if SpO₂ remains <90% for 5+ minutes despite optimized PAP settings 3
• Start at 1 L/minute and increase in 1 L/minute increments every 5 minutes until SpO₂ >90% 3

Additional Interventions

If optimized PAP therapy fails:

1. Mandibular advancement devices:

   • For mild to moderate OSA (AHI <30/h) 1
   • Less effective than CPAP but may be better tolerated

2. Weight loss program:

   • Target 25-30% of actual body weight for obese patients 1
   • Consider bariatric surgery evaluation for patients with BMI >40 kg/m² 1

3. Surgical options:

   • Hypoglossal nerve stimulation for suitable candidates (AHI 15-65/h, BMI <32 kg/m²) 1
   • Maxillomandibular advancement for severe OSA if other therapies fail 1
   • ENT evaluation with drug-induced sleep endoscopy to identify site of obstruction 3

Follow-up and Monitoring

• Schedule follow-up within the first few weeks of any intervention 1
• Use "Effective AHI" to assess true therapy effectiveness, which accounts for both PAP-on and PAP-off periods 5
• Monitor for improvement in daytime sleepiness, blood pressure, and quality of life 1

Common Pitfalls to Avoid

1. Waiting too long to address adherence issues (intervene within first week rather than waiting 30+ days) 1
2. Overlooking mask fit problems, which significantly impact both adherence and efficacy 2
3. Failing to consider pressure-relief features may reduce treatment efficacy 4
4. Not recognizing that patients using PAP <6 hours may have significant residual OSA during non-PAP time 5
5. Overlooking potential OHS in severely obese patients 1

By systematically addressing these factors, most patients with high residual AHI despite CPAP therapy can achieve improved sleep-disordered breathing control and better clinical outcomes.