Obstructive Sleep Apnea

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.

⭐ 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.

⭐ 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.

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.

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.