Sleep-disordered breathing (SDB) encompasses a spectrum of conditions including obstructive sleep apnea (OSA, the most common, affecting 10-30% of adults with significant under-recognition), central sleep apnea (CSA), sleep-related hypoventilation (obesity hypoventilation, neuromuscular disease), Cheyne-Stokes breathing (heart failure), and treatment-emergent CSA. Diagnostic testing is essential because clinical symptoms (excessive daytime sleepiness, snoring, witnessed apnea, fatigue, morning headache) lack specificity. The American Academy of Sleep Medicine (AASM) classifies sleep studies by complexity: type I—attended in-laboratory PSG (most comprehensive); type II—comprehensive portable PSG (rarely used); type III—portable monitor measuring airflow, respiratory effort, and oxygen saturation (home sleep apnea test); type IV—single or dual channel monitors (usually inadequate for diagnosis).
Polysomnography (PSG) is the gold standard, performed in accredited sleep laboratory with technologist attendance overnight, recording: electroencephalogram (EEG, 6 channels per AASM), electrooculogram (EOG, 2 channels), submental and tibial electromyogram (EMG), electrocardiogram (ECG), nasal pressure transducer, oronasal thermal sensor (CPAP titration), respiratory inductance plethysmography (chest and abdominal effort), pulse oximetry, body position sensor, snoring microphone, video recording. Scoring follows AASM criteria with apnea (≥90% airflow drop ≥10 sec), hypopnea (≥30% drop with ≥3% desaturation or arousal), and respiratory effort-related arousal (RERA). Apnea-hypopnea index (AHI) classifies OSA: 5-14 mild, 15-29 moderate, ≥30 severe. PSG also evaluates sleep architecture (REM/NREM staging, sleep efficiency), arousals, periodic limb movements, and parasomnias.
Home sleep apnea testing (HSAT, type III device with 4-7 channels) is increasingly used for adults with high pre-test probability of moderate-severe OSA without significant comorbidities (heart failure, COPD, neuromuscular disease, severe insomnia, suspected non-OSA disorders). HSAT advantages: home environment, lower cost, faster access. Limitations: cannot stage sleep (uses recording time vs sleep time, may underestimate AHI by ~30%), cannot diagnose central sleep apnea reliably, cannot detect parasomnias or other sleep disorders, requires patient self-application. Negative HSAT in symptomatic patient should be followed by attended PSG. Indications for in-lab PSG over HSAT: suspected CSA, complex sleep disorders, severe insomnia, moderate-severe cardiopulmonary disease, neuromuscular disease, suspected nocturnal hypoventilation, pediatric patients, failed CPAP titration. Special studies: split-night PSG (diagnostic first half, CPAP titration second half if AHI severe by 2 hours); CPAP titration PSG; multiple sleep latency test (MSLT) for narcolepsy; maintenance of wakefulness test (MWT) for safety-critical occupations. Treatment of confirmed OSA: weight loss, positional therapy (avoid supine), continuous positive airway pressure (CPAP) gold standard, auto-PAP, bilevel PAP for hypoventilation, mandibular advancement device for mild-moderate OSA, hypoglossal nerve stimulator (Inspire) for moderate-severe with positional dependence, soft palate/tonsil/maxillomandibular advancement surgery for selected, adaptive servo-ventilation for treatment-emergent CSA without low EF (contraindicated in HFrEF EF <45%).