AHI Cut-off for Proceeding to CPAP Titration
Proceed to formal CPAP titration when the diagnostic sleep study demonstrates an AHI ≥15 events/hour, or when AHI ≥5 events/hour in the presence of symptoms (excessive daytime sleepiness, witnessed apneas, nocturnal gasping/choking, morning headaches, nocturia) or cardiovascular/cerebrovascular comorbidities. 1
Primary Thresholds for Titration
The decision to proceed with CPAP titration follows a symptom-stratified approach:
AHI ≥15 events/hour: Proceed to titration regardless of symptom presence, as this threshold defines moderate-to-severe OSA with independent cardiovascular risk 1, 2
AHI 5-14 events/hour (mild OSA): Proceed to titration only when accompanied by:
AHI <5 events/hour: Do not proceed to titration; OSA is not present by standard diagnostic criteria 1, 2
Critical Diagnostic Considerations Before Titration
Hypopnea Scoring Definition Matters
The hypopnea definition used during diagnostic testing directly impacts whether the AHI threshold is met 1:
- AASM-recommended criteria: ≥30% airflow reduction for ≥10 seconds with either ≥3% oxygen desaturation OR EEG arousal 1
- CMS alternative criteria: ≥30% airflow reduction with ≥4% desaturation (no arousal criterion) 1
The CMS 4% desaturation rule can underdiagnose OSA by 36-48% compared to AASM criteria, potentially yielding a median AHI of ~8 events/hour versus ~25 events/hour in the same patient. 1 Verify which scoring criteria were applied before making titration decisions.
Alternative Metric: Respiratory Disturbance Index (RDI)
When the diagnostic study reports RDI instead of AHI 1:
- RDI ≥5 events/hour is diagnostic for OSA and warrants titration consideration using the same symptom-stratified approach
- RDI includes respiratory effort-related arousals (RERAs) and may identify clinically significant disease missed by AHI alone, particularly in lean patients with minimal desaturations 1
Common Pitfalls to Avoid
Symptom Reporting Is Unreliable
78% of patients with confirmed OSA deny common symptoms of snoring and sleepiness 3, and patients with severe OSA (AHI ≥30) often report normal sleepiness scores 3. Therefore:
- Do not exclude patients from titration based solely on absence of reported symptoms when AHI ≥15 1
- For AHI 5-14, actively probe for cardiovascular comorbidities even when symptoms are denied 1, 3
Medicare Coverage Criteria Align with Clinical Thresholds
Medicare authorizes CPAP coverage when 1:
- AHI ≥15 events/hour (any patient)
- OR AHI ≥5 events/hour with documented excessive sleepiness or established cardiovascular disease
This coverage framework mirrors the clinical titration thresholds above.
Auto-Titrating CPAP Without In-Lab Titration
For patients meeting criteria (AHI ≥15 or symptomatic AHI 5-14), auto-CPAP without formal in-lab titration is an acceptable alternative 4, 5:
- Auto-CPAP devices estimate residual AHI with good accuracy: an auto-CPAP AHI cutoff of 6 events/hour differentiates adequately treated patients from those with residual OSA (sensitivity 0.92, specificity 0.90) 4
- However, home auto-CPAP initiation requires systematic follow-up with telemonitoring to optimize adherence and assess residual AHI 3
Severity Classification After Diagnosis
Once the decision to titrate is made, classify severity to guide treatment intensity 1, 2:
- Mild OSA: AHI 5-15 events/hour
- Moderate OSA: AHI 15-30 events/hour
- Severe OSA: AHI ≥30 events/hour