Sleep-Disordered Breathing

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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?

Factors and cycle of obstructive sleep apnea

⭐ 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.

Oral appliance for sleep apnea

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.

Practice Questions: Sleep-Disordered Breathing

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