Sleep-Disordered Breathing

SDB Spectrum & Definitions - Snore Wars Saga

• SDB (Sleep-Disordered Breathing): Spectrum of disorders; abnormal respiration during sleep.
• Key Definitions:
  • OSA (Obstructive Sleep Apnea): Recurrent upper airway collapse.
  • CSA (Central Sleep Apnea): ↓/absent ventilatory effort.
  • UARS (Upper Airway Resistance Syndrome): Airflow limitation; no frank apnea/hypopnea.
  • OHS (Obesity Hypoventilation Syndrome): Obesity + daytime hypercapnia.

⭐ Apnea-Hypopnea Index (AHI) is the total number of apneas and hypopneas per hour of sleep.

Pathophysiology of OSA - The Choking Point

• OSA: Recurrent upper airway collapse (partial/complete) during sleep → apnea/hypopnea, intermittent hypoxia, hypercapnia, sleep fragmentation.
• Key Factors:
  • Anatomical narrowing: e.g., retrognathia, tonsillar hypertrophy, obesity (fat deposition).
  • Neuromuscular: ↓ pharyngeal dilator muscle activity (e.g., genioglossus) during sleep.
  • Inspiratory negative pressure overcomes airway stability.
• CSA (contrast): Impaired central ventilatory effort, not obstruction.

⭐ The velopharynx (soft palate area) and oropharynx (tongue base area) are the most common sites of airway collapse in OSA.

Clinical Clues & Risks - The Sleepiness Scale

• Symptoms: Loud snoring, witnessed apneas, EDS, morning headaches, nocturnal choking/gasping.
• Signs: Obesity (BMI >30), ↑Neck circ. (>43cm M, >40cm F), Mallampati III/IV, retrognathia.
• Key Risks: Male, Age >50, family Hx, alcohol/sedatives, craniofacial anomalies.
• Screening:
  • ESS (Epworth Sleepiness Scale): Assesses EDS. Score >10 = significant sleepiness.
  • STOP-BANG: (Snoring, Tired, Observed apnea, Pressure, BMI >35, Age >50, Neck, Gender).

    ⭐ STOP-BANG score ≥3 indicates high risk of OSA; Neck circumference >43cm (M) or >40cm (F) is a key risk factor.

Diagnostic Deep Dive - Decoding Sleep Tests

• Polysomnography (PSG): Gold standard (Type I). Comprehensive in-lab evaluation.
  • Monitors multiple channels: EEG, EOG, EMG, ECG, airflow, respiratory effort, SaO2.
  • Key Metrics: AHI, RDI, ODI, SaO2 nadir (lowest O2 saturation).
• Home Sleep Apnea Test (HSAT): Portable (Type III/IV) for suspected moderate-severe uncomplicated OSA.

⭐ Polysomnography (PSG) is gold standard. OSA AHI severity: Mild 5-14.9, Moderate 15-29.9, Severe ≥30 events/hr.

Treatment Blueprints - Breathing Easy Again

• Conservative:
  • Weight loss (target BMI < 25).
  • Positional therapy (non-supine).
  • Avoid alcohol/sedatives pre-sleep.
• Medical Therapy:
  • CPAP: First-line for moderate (AHI 15-30) to severe (AHI >30) OSA.
  • Oral Appliances (MADs): For mild-moderate OSA or CPAP intolerance.
• Surgical Options (if CPAP fails/intolerated or specific anatomy):
  • UPPP (Uvulopalatopharyngoplasty).
  • MMA (Maxillomandibular Advancement) - highly effective.
  • T&A (Adenotonsillectomy) - primary for pediatric OSA.

⭐ CPAP is first-line for moderate-severe OSA; surgical options considered for CPAP failure/intolerance or specific anatomical issues.

High‑Yield Points - ⚡ Biggest Takeaways

• OSA involves recurrent upper airway collapse during sleep, causing hypoxia and fragmented sleep.
• Polysomnography (PSG) is gold standard for diagnosis; severity based on Apnea-Hypopnea Index (AHI).
• AHI: Mild 5-15, Moderate 15-30, Severe >30 events/hour.
• Major risk factors: obesity (BMI >30), male gender, adenotonsillar hypertrophy (children).
• CPAP is first-line for moderate-severe adult OSA; adenotonsillectomy for most children.
• Excessive Daytime Somnolence (EDS) is a key symptom of OSA and significantly impacts quality of life.