Screening and Diagnosis of OSA - AASM Guidelines

1. Overview

2. Diagnostic Criteria for OSA

• Apnea: Complete cessation of airflow for ≥ 10 seconds despite continued respiratory effort (obstructive) or without effort (central)
• Hypopnea (AASM recommended): ≥ 30% reduction in airflow for ≥ 10 seconds, accompanied by either ≥ 3% oxygen desaturation (SpO2) OR a cortical arousal
• Hypopnea (CMS criteria): ≥ 30% reduction in airflow, accompanied by ≥ 4% oxygen desaturation - this is slightly more restrictive than AASM
• RERA (Respiratory Effort-Related Arousal): Flow limitation associated with cortical arousal; included in the Respiratory Disturbance Index (RDI) but not the AHI

OSA vs. CSA distinction: OSA is characterized by obstructive events (>50% of events are obstructive, i.e., airflow absent/reduced with continued respiratory effort). CSA has >50% central apneas/hypopneas with central AHI >5. - Braunwald's Heart Disease, Table 89.1

3. Severity Classification

4. Screening: Who to Test

AASM "Increased Risk" Criteria for Diagnostic Testing

Excessive daytime sleepiness PLUS at least 2 of the following 3:

1. Habitual loud snoring
2. Witnessed apnea, gasping, or choking
3. Diagnosed hypertension

Clinical Screening Tools

• Score ≥ 3: High risk (screened positive - proceed to testing)
• Score 5-8: Suggests moderate-to-severe OSA specifically
• Score 0-2: Low risk

5. Diagnostic Testing: PSG vs. HSAT

Recommendation 1 (STRONG): No Diagnosis by Questionnaire Alone

Recommendation 2 (STRONG): PSG or HSAT for Uncomplicated Patients

• Either PSG or HSAT with a technically adequate device is acceptable

• Significant cardiorespiratory disease
• Potential respiratory muscle weakness (neuromuscular disease)
• Awake hypoventilation or suspected sleep-related hypoventilation
• Chronic opioid use
• History of stroke
• Severe insomnia

Recommendation 3 (STRONG): Negative/Inconclusive HSAT → Get PSG

Recommendation 4 (STRONG): PSG Required for Complex/Comorbid Patients

Recommendation 5 (WEAK): Split-Night Protocol Acceptable

1. Moderate-to-severe OSA observed during ≥ 2 hours of diagnostic recording, AND
2. ≥ 3 hours remain for CPAP titration

6. Polysomnography - Technical Overview

Braunwald's Heart Disease - Figure 89.1: Note absent effort with central apneas vs. persistent thoracoabdominal effort with obstructive apneas; SpO2 nadirs reach 87-88% in obstructive events

HSAT Devices

• Peripheral arterial tonometry (PAT) + oximetry + actigraphy (e.g., WatchPAT)
• Cardiorespiratory channels: airflow + respiratory effort + oximetry + HR
• Some newer devices include a single EEG channel

7. Oximetry Alone: Not Sufficient

• Single-channel measurement - cannot classify event type
• Cannot distinguish apnea from hypopnea from hypoventilation
• Normal oximetry does not exclude OSA

8. Inpatient Screening (AASM 2025 Guideline - New)

• Recommendation 1 (Conditional): For medically hospitalized adults at increased OSA risk, the AASM suggests in-hospital screening as part of a care management pathway incorporating diagnosis and PAP treatment - rather than no screening
• Screening may include validated questionnaires and/or overnight high-resolution pulse oximetry
• Recommendation 4 (Conditional): A discharge management plan should be arranged for at-risk/diagnosed patients to ensure timely outpatient diagnosis and effective OSA management
• Good Practice Statement: For hospitalized patients already on PAP therapy, existing treatment should be continued rather than withheld unless contraindicated

9. Algorithm Summary

Clinical suspicion (snoring, EDS, witnessed apneas, HTN, obesity)
           ↓
Screening questionnaire (STOP-Bang, Berlin, ESS) + clinical assessment
           ↓
Increased risk confirmed?
      ↓ YES
Is patient "uncomplicated"?
   ↓ YES                          ↓ NO (complex comorbidities)
HSAT or PSG                       PSG only
   ↓
HSAT result:
  Positive → Diagnose, treat
  Negative/Inconclusive → Proceed to PSG
   ↓
PSG → AHI interpretation → Severity grading → Treatment

Key References

• AASM 2017 Diagnostic Testing Guideline - Kapur VK et al., J Clin Sleep Med 2017 (primary source for recommendations above)
• Mehra R et al. AASM 2025 inpatient OSA guideline. J Clin Sleep Med 2025 (PMID: 40838698)
• AASM Manual for Scoring Sleep and Associated Events, Version 3, 2023
• Braunwald's Heart Disease, Table 89.1 and Figure 89.1
• Miller's Anesthesia, 10e, Box 54.2 (STOP-Bang)
• Murray & Nadel's Respiratory Medicine - Diagnostic Sleep Testing chapter