Obstructive Sleep Apnea: Diagnosis

Clinical - Respiratory/Pulmonary

Obstructive Sleep Apnea (OSA) is defined as complete apnea for 10 seconds, five times per hour, associated with a 4% decrease in SaO2 (while sleeping). Hypopnea is a less-severe form of obstruction (50% reduction in airflow, also accompanied by a 4% fall in SaO2). Both OSA and hypopnea require a sleep study for diagnosis. Sleep studies are scored with an apnea/hypopnea index (AHI – mild OSA is 5-15, moderate OSA is 15-30, and severe OSA is > 30 AHI). Moderate/severe OSA is treated with CPAP

OSA can lead to significant comorbidities, including systemic and pulmonary hypertension, LVH, arrhythmias, and cognitive impairment

Obesity is the most important risk factor for OSA, although most patients with OSA are not obese. The STOP and STOP-BANG criteria were developed to assist anesthesiologists in predicting who is at risk for OSA, and both correlated well with polysomnography.

Diagnosis of OSA

  • OSA: complete apnea for 10 seconds, five times per hour, associated with a 4% decrease in SaO2
  • Hypopnea: 50% airflow reduction, 15 times or more per hour, 4% decrease in SaO2
  • Physiologic Effects of OSA: systemic and pulmonic HTN, LVH, arrhythmia, cognitive impairment
  • STOP: Snoring; Tired; Observed Not Breathing; Blood Pressure (2 or more = high risk)
  • STOP-BANG: STOP + BMI > 35, Age > 50, Neck > 40 cm, Male (3 or more = high risk)

Sources

    Miller’s Anesthesia, 7th Edition. p 2092-3, 2711

    Anesthesiology. 2009 Jan;110(1):193; author reply 193-4

    [PubMed: 18431116]

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