Sleep-Disordered Breathing

SDB Spectrum - Defining the Zzz‑vil

Sleep-Disordered Breathing (SDB): Group of disorders with abnormal breathing during sleep.

• Key Terms:
  • Apnea: Airflow stops ≥10s.
    • Obstructive: Effort persists.
    • Central: Effort absent.
  • Hypopnea: Airflow ↓ ≥30% for ≥10s + ≥3% O₂ desat. or arousal.
• Main Types:
  • Obstructive Sleep Apnea (OSA): Repetitive upper airway collapse.
  • Central Sleep Apnea (CSA): ↓/absent ventilatory drive.
  • Obesity Hypoventilation Syndrome (OHS): BMI ≥30 kg/m², daytime PaCO₂ >45 mmHg.

⭐ Apnea-Hypopnea Index (AHI) = (apneas + hypopneas)/hour of sleep. AHI ≥5/hr is diagnostic for OSA.

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OSA: Culprits & Clues - The Choke Hold

• Pathophysiology: The "Choke"
  • Recurrent upper airway collapse during sleep due to:
    • ↓ Pharyngeal muscle tone (e.g., genioglossus).
    • Anatomical narrowing: Enlarged tonsils/adenoids, large tongue base, elongated soft palate/uvula.
    • Inspiratory negative pressure overcoming airway dilator muscle activity.
• Risk Factors: The "Culprits"
  • Obesity (BMI > 30 kg/m²): Strongest risk factor. Neck circumference >17 inches (men), >16 inches (women).
  • Craniofacial abnormalities: Retrognathia, micrognathia, adenotonsillar hypertrophy.
  • Male gender; Increasing age (>40 years).
  • Family history of OSA.
  • Smoking, alcohol, or sedative use (especially before sleep).
  • Endocrine disorders: Hypothyroidism, acromegaly.
• 📌 STOP-BANG Score (≥3 indicates high risk of OSA):
  • Snoring loudly?
  • Tired or fatigued during daytime?
  • Observed apnea during sleep?
  • High blood Pressure?
  • BMI > 35 kg/m²?
  • Age > 50 years?
  • Neck circumference large?
  • Gender male?

⭐ OSA is an independent risk factor for systemic hypertension, often resistant to standard antihypertensive therapy. It also significantly increases risk for arrhythmias (e.g., atrial fibrillation).

Diagnosing SDB - Unmasking the Night

• Clinical Red Flags:
  • Loud Snoring, Witnessed Apneas, Gasping/Choking.
  • Excessive Daytime Sleepiness (EDS): Epworth Sleepiness Scale (ESS) > 10.
  • Morning headaches, fatigue, impaired concentration, nocturia.
  • 📌 STOP-BANG (Snoring, Tired, Observed, Pressure, BMI, Age, Neck, Gender) for screening.
• Diagnostic Pathway:

• Polysomnography (PSG): Gold Standard

  • Comprehensive: EEG (sleep staging), EOG (eye movements), EMG (chin/limbs), ECG (arrhythmias), Airflow, Respiratory Effort (chest/abdomen), SpO2, Snoring.

• Key Indices (events/hr):

  • Apnea-Hypopnea Index (AHI): $AHI = \frac{\text{No. of Apneas} + \text{No. of Hypopneas}}{\text{Total Sleep Time (in hours)}}$.
  • Respiratory Disturbance Index (RDI): AHI + Respiratory Effort-Related Arousals (RERAs).

• SDB Severity (Adults, AHI/RDI):

  • Normal: < 5
  • Mild: 5-14.9
  • Moderate: 15-29.9
  • Severe: ≥ 30

⭐ OSA diagnosis: AHI ≥ 15/hr, OR AHI ≥ 5/hr with SDB symptoms (e.g., EDS, snoring, witnessed apneas) or associated medical/psychiatric disorders (e.g., HTN, CAD, mood disorder).

Managing SDB - Reclaiming Rest

• General Measures (All SDB):
  • Weight loss (target >10% if overweight/obese).
  • Positional therapy (e.g., tennis ball technique).
  • Avoid alcohol & sedatives before sleep.
• Obstructive Sleep Apnea (OSA):
  • CPAP (Continuous Positive Airway Pressure): Mainstay for moderate-severe OSA. Improves AHI, daytime somnolence, QoL.

    ⭐ CPAP is the first-line treatment for symptomatic moderate to severe Obstructive Sleep Apnea (OSA).

  • Oral Appliances (Mandibular Advancement Devices - MADs): Mild-moderate OSA or CPAP intolerance.
  • Surgical: Uvulopalatopharyngoplasty (UPPP), Maxillomandibular Advancement (MMA), bariatric surgery. Tracheostomy (rarely, severe refractory cases).
• Central Sleep Apnea (CSA):
  • Address underlying cause (e.g., heart failure, stroke, high altitude).
  • Positive airway pressure (CPAP, BiPAP), Adaptive Servo-Ventilation (ASV).
  • Oxygen, acetazolamide (limited use).
• Obesity Hypoventilation Syndrome (OHS):
  • Aggressive weight loss.
  • Nocturnal Non-Invasive Ventilation (NIV), usually BiPAP, to correct chronic hypoventilation.

High‑Yield Points - ⚡ Biggest Takeaways

• Obstructive Sleep Apnea (OSA): Most common; recurrent upper airway collapse during sleep.
• Polysomnography (PSG): Gold standard for diagnosis.
• AHI severity based on events/hr: Mild (5-15), Moderate (15-30), Severe (>30).
• CPAP: First-line, most effective therapy for moderate to severe OSA.
• Key risk factors: Obesity (BMI >30), male gender, age, craniofacial abnormalities.
• Central Sleep Apnea (CSA): Characterized by absent respiratory effort (CNS origin).
• Overlap Syndrome (OSA + COPD): Associated with significantly worse prognosis.