Obstructive Sleep Apnea

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OSA: Definition & Pathophysiology - Snore Wars Begins

  • Definition: Recurrent upper airway obstruction during sleep.
    • Apnea: Airflow cessation ≥10s.
    • Hypopnea: Airflow ↓ ≥30% for ≥10s + ≥3% O₂ desat / arousal.
    • RERA: Respiratory Effort-Related Arousal.
  • AHI (Apnea-Hypopnea Index) Severity:
    • Mild: 5-14.9/hr
    • Moderate: 15-29.9/hr
    • Severe: ≥30/hr
  • Pathophysiology: Upper airway collapse (anatomical: retrognathia, tonsillar hypertrophy; non-anatomical: impaired muscle function) → intermittent hypoxia, hypercapnia, sleep fragmentation, ↑sympathetic activity.
    • Sites: Palate, tongue base, lateral pharyngeal walls.
  • Epidemiology: M>F, ↑age, obesity.

Upper airway anatomy in sagittal and axial views

⭐ AHI is calculated as (total apneas + total hypopneas) / total sleep time in hours.

OSA: Risk Factors & Etiology - The Choke Artists

Key predisposing factors narrow the airway:

  • Obesity: Most critical. BMI >30 kg/m², central adiposity, ↑ neck circumference (>43cm M, >40cm F).
  • Anatomic: Male gender, Age >40-65 yrs, craniofacial abnormalities (retrognathia, micrognathia, adenotonsillar hypertrophy - esp. children), family history.
  • Lifestyle/Other: Smoking, alcohol/sedatives (pre-sleep), supine sleep position, nasal obstruction.
  • Associated Conditions: Hypothyroidism, Acromegaly, PCOS. Upper airway anatomy in normal and OSA states

⭐ Obesity is the single most significant modifiable risk factor for OSA.

OSA: Clinical Features & Complications - Night & Day Woes

  • Nocturnal Symptoms:
    • Loud habitual snoring, witnessed apneas/gasps.
    • Choking/gasping awakenings, restless sleep, nocturia.
  • Daytime Symptoms:
    • Excessive Daytime Sleepiness (EDS) - Epworth Scale >10.
    • Morning headaches, fatigue, impaired concentration/memory.
    • Mood disturbances (irritability, depression).
  • Key Complications (Systemic Impact):
    • Cardiovascular: Hypertension (systemic & pulmonary), CAD, MI, Arrhythmias (AF), Stroke, CHF.
    • Metabolic: Insulin resistance, Type 2 DM, Metabolic syndrome.
    • Neurocognitive: Impaired vigilance, ↑MVA risk.
    • Others: GERD, NAFLD.

⭐ Untreated OSA significantly increases the risk of cardiovascular morbidity and mortality.

OSA: Diagnosis - The Sleep Sleuth

  • Screening Tools:
    • Epworth Sleepiness Scale (ESS)
    • STOP-BANG (Snoring, Tired, Observed apnea, Pressure, BMI, Age, Neck, Gender)
    • Berlin Questionnaire
  • Diagnostic Tests:
    • Polysomnography (PSG): Gold standard. In-lab, attended. Monitors EEG, EOG, EMG, ECG, airflow, effort, SaO2.
    • Home Sleep Apnea Testing (HSAT): For high pre-test probability, uncomplicated cases.
  • Key Criteria: Apnea-Hypopnea Index (AHI) / Respiratory Disturbance Index (RDI)
    • Mild: AHI 5-14.9/hr
    • Moderate: AHI 15-29.9/hr
    • Severe: AHI ≥30/hr
  • Other: ENT exam, Cephalometry, Drug-Induced Sleep Endoscopy (DISE) for surgical planning.

⭐ STOP-BANG score: ≥3 indicates high risk of OSA; ≥5 is very high risk.

Polysomnography showing obstructive sleep apnea

OSA: Management - Breathing Easy Again

  • General/Behavioral: Weight loss (target 10%), positional therapy (avoid supine), exercise, avoid alcohol/sedatives pre-bedtime, smoking cessation, manage nasal obstruction.
  • PAP Therapy:
    • CPAP: First-line for moderate-severe OSA.
    • APAP/BiPAP: For CPAP intolerance or comorbid hypoventilation.
  • Oral Appliances (OAs): For mild-moderate OSA or CPAP intolerance. (e.g., MADs).
  • Surgery (Site-specific, selected patients): UPPP, MMA, HGNS. Tracheostomy for refractory severe OSA.

⭐ CPAP adherence is critical: ≥4 hours/night on ≥70% of nights for effectiveness.

Oral appliance for sleep apnea mechanism

High-Yield Points - ⚡ Biggest Takeaways

  • OSA involves recurrent upper airway obstruction during sleep, causing hypoxia and sleep fragmentation.
  • Obesity is the strongest risk factor; others include male gender, ↑age, and large neck circumference.
  • Excessive daytime sleepiness (EDS) is a hallmark symptom; use Epworth Sleepiness Scale for subjective assessment.
  • Polysomnography (PSG) is the gold standard for diagnosis, with AHI ≥5 events/hour being diagnostic.
  • Continuous Positive Airway Pressure (CPAP) is the first-line treatment; weight loss is crucial.
  • Major complications include systemic hypertension, cardiac arrhythmias, stroke, and pulmonary hypertension.
  • The STOP-BANG questionnaire is a common screening tool for OSA risk assessment.

Practice Questions: Obstructive Sleep Apnea

Test your understanding with these related questions

All of the following criteria are required for diagnosis of obesity hypoventilation syndrome except -

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Flashcards: Obstructive Sleep Apnea

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Recurrent tonsillitis is described as:_____ episodes/yr for 3 consecutive years5 episodes/yr for 2 consecutive years or7 episodes in a single year.

TAP TO REVEAL ANSWER

Recurrent tonsillitis is described as:_____ episodes/yr for 3 consecutive years5 episodes/yr for 2 consecutive years or7 episodes in a single year.

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