Sleep Apnea: Classification
Advanced, Organ-Based and Clinical Sciences
The Apnea Hypopnea Index (AHI) stratifies the severity of sleep apnea. Apneas are >90% reduction in airflow for at least 10sec whereas hypopneas are partial obstructions of at least 10sec where thoracoabdominal movement is reduced by 50% or a 30% reduction in airflow measured by nasal pressure transducer.
Polysomnography is the gold standard for measurement of AHIs and diagnosis of sleep apnea. Severity of sleep apnea is classified accordingly:
None/Minimal: AHI < 5 per hour
Mild: AHI ≥ 5, but < 15 per hour
Moderate: AHI ≥ 15, but < 30 per hour
Severe: AHI ≥ 30 per hour
Patients w/ AHI >=5 and concomitant symptoms (daytime sleepiness, hypersomnolence, insomnia, snoring, witnessed breathing pauses, cognitive impairment, waking up gasping for air) or alternatively AHI>=15 regardless of symptoms are positive for a diagnosis of sleep apnea.