Sleep-Related Breathing Disorders
Definitions
Obstructive sleep apnea (OSA) is repetitive upper-airway collapse causing apneas/hypopneas with preserved or increased respiratory effort; central sleep apnea (CSA) reflects absent ventilatory drive (no effort). The apnea-hypopnea index (AHI) grades severity: 5-15 mild, 15-30 moderate, >30 severe. Hypopnea scoring depends on the rule used (a ≥30% flow reduction with ≥3% desaturation or an arousal, versus a ≥4% desaturation criterion); know that the definition affects the index. Obesity hypoventilation syndrome combines obesity (BMI ≥30) with daytime hypercapnia (PaCO2 >45 mm Hg) after excluding other causes.
Diagnosis and testing
Home sleep apnea testing is appropriate for adults with high pretest probability of moderate-to-severe OSA without significant cardiopulmonary comorbidity; it is not appropriate for suspected CSA, significant heart failure, or in children. In-laboratory polysomnography is the reference standard and is required when home testing is negative but suspicion remains.
Treatment
Positive airway pressure (CPAP) is first-line for moderate-to-severe OSA and for symptomatic mild OSA; adherence (commonly ≥4 hours/night on most nights) determines benefit. Alternatives include mandibular advancement devices for mild-to-moderate OSA or CPAP intolerance, positional therapy, and weight loss; hypoglossal nerve stimulation is for selected CPAP-intolerant patients. Upper-airway surgery (e.g., uvulopalatopharyngoplasty, maxillomandibular advancement) is reserved for selected cases. Treat CSA by addressing the cause (heart failure, opioids, central depressants); adaptive servo-ventilation is contraindicated in central sleep apnea with predominantly Cheyne-Stokes respiration and ejection fraction ≤45%.
Traps
Do not use home testing to diagnose CSA or pediatric OSA; do not equate AHI with symptom severity; remember that OSA increases cardiovascular and metabolic risk.