| Apnea | Adult: ≥90% drop in airflow from baseline lasting ≥10 seconds* Children: ≥90% reduction of airflow from the pre-event baseline for ≥2 breaths with respiratory effort throughout this period | ||
| Hypopnea | Adult: abnormal respiratory event lasting at least 10 seconds with ≥30% reduction in thoracoabdominal movement or airflow compared with baseline, and with at least a 4% oxygen desaturation18 Children: ≥30% reduction of nasal airflow from the pre-event baseline for at least 2 breaths, and with at least a 3% oxygen desaturation | ||
| AHI | Number of apneas plus hypopneas per hour of sleep Based on the AHI, the severity of OSA is classified as follows7,19: | ||
| OSA severity | Adult criteria (AHI/hour)† | Pediatric criteria (AHI/hour) | |
|---|---|---|---|
| None/minimal | <5 | 0 | |
| Mild | 5–14 | 1–5 | |
| Moderate | 15–29 | 6–10 | |
| Severe | ≥30 | >10 | |
| Oxygen Desaturation Index | Hourly average number of desaturation episodes, defined as ≥4% decrease in saturation from the average saturation in the preceding 120 seconds, and lasting >10 seconds | ||
| Central apnea | Reduction in flow is mainly caused by a reduction in ventilatory effort | ||
| Obstructive apnea | Reduction in airflow is mainly caused by increased upper airway resistance | ||
| OSA syndrome | Adults: AHI score ≥15 events/hour or ≥5 events/hour with symptoms (such as daytime somnolence, fatigue, and cognitive impairment; or cardiovascular comorbid conditions, such as hypertension, ischemic heart disease, or prior stroke)‡ Children: disorder of breathing during sleep characterized by prolonged partial upper airway obstruction and/or intermittent complete obstruction (obstructive apnea) that disrupts normal ventilation during sleep and normal sleep patterns, accompanied by symptoms or signs§ | ||
↵* The American Academy of Sleep Medicine (AASM) definition; Centers for Medicare & Medicaid Services (CMS) uses cessation of airflow.
↵† Most studies use these criteria. Because of a lack of a uniform definition of obstructive sleep apnea (OSA) severity, the American Society of Anesthesiologists' latest guideline on perioperative management of OSA uses the terms mild, moderate, and severe “as defined by the laboratory where the sleep study was performed.” If overall severity is not indicated by the sleep laboratory, they classify OSA severity from Apnea-Hypopnea Index (AHI) as none (0–5), mild (6–20), moderate (21–40), severe (>40).7
↵‡ Criteria for OSA diagnosis of both AASM and the CMS.19
Also see Berry et al.20
↵§ As listed in Table 2, right column, “Symptoms and Signs of Pediatric OSAS.”16