Sleep-Disordered Breathing

OSA Fundamentals - Snore Wars Patho

• Sleep-Disordered Breathing (SDB): Spectrum of abnormalities; Obstructive Sleep Apnea (OSA) is most common, featuring recurrent upper airway collapse during sleep leading to ↓ or absent airflow.
• Prevalence (India): Estimated ~4-13.7% in adults.
• Key Risk Factors: 📌 OSA COMICS
  • Obesity: BMI > 30 kg/m²
  • Male gender
  • Age: ↑ risk
  • Craniofacial: Retrognathia, micrognathia, tonsillar/adenoidal hypertrophy
  • Ingestants: Alcohol, sedatives
  • Circumference (Neck): > 17 inches (men), > 16 inches (women)
  • Smoking, Family history
• Pathophysiology: Recurrent upper airway collapse → intermittent hypoxia/hypercapnia → sleep fragmentation → sympathetic activation.

⭐ The most significant modifiable risk factor for OSA is obesity, particularly visceral adiposity.

OSA Diagnosis - Catching Zzz's Clues

• Clinical Features:
  • Nighttime: Loud snoring, witnessed apneas, gasping/choking, nocturia.
  • Daytime: Excessive Daytime Sleepiness (EDS) - assess with Epworth Sleepiness Scale (ESS), morning headaches, poor concentration, mood changes.
• Screening Tools:
  • 📌 STOP-BANG: Snoring, Tired, Observed apnea, Pressure (BP), BMI >35 kg/m$^2$, Age >50yrs, Neck circumference >40cm, Gender (Male). Score ≥3 → high risk.
• Diagnostic Standard: Polysomnography (PSG)
  • Gold standard. Key parameters: Apnea-Hypopnea Index (AHI), Respiratory Disturbance Index (RDI), Oxygen Desaturation Index (ODI), arousal index.
  • Apnea: ≥90% airflow reduction for ≥10s.
  • Hypopnea: ≥30% airflow reduction for ≥10s + ≥3% $O_2$ desaturation or arousal.
• Home Sleep Apnea Testing (HSAT):
  • Indications: High pre-test probability of moderate-severe uncomplicated OSA.
  • Limitations: Cannot rule out OSA if negative; not for complex cases (e.g., CHF, COPD).

⭐ An Epworth Sleepiness Scale (ESS) score >10 suggests clinically significant daytime sleepiness.

AHI Severity Classification (Adults)

OSA Management - Breathing Easy Again

Goals: Normalize AHI/RDI, ↑sleep quality & alertness, ↓symptoms & complications.

• Lifestyle: Weight loss (10% or BMI <25 kg/m²), positional therapy (avoid supine), avoid alcohol/sedatives pre-sleep, smoking cessation.
• PAP Therapy: 📌 PAP Smear (CPAP, APAP, BiPAP).
  • CPAP: 1st line (mod-severe OSA & symptomatic mild). Compliance >4hrs/night on >70% of nights.

  ⭐ CPAP is the gold standard treatment for moderate to severe OSA.

  • APAP/BiPAP: For CPAP intolerance, high pressure needs, or comorbid hypoventilation.
• Oral Appliances: Mandibular advancement devices (MADs), tongue-retaining devices. For mild-moderate OSA or CPAP failure/intolerance.
• Surgical Options: UPPP, MMA, genioglossus advancement, hypoglossal nerve stimulation, tracheostomy. For specific anatomical issues or CPAP failure.
• Pharmacotherapy: Limited role. E.g., modafinil/solriamfetol for residual EDS despite optimal CPAP.
• Complications (Untreated): CV (HTN, CAD, AF, Stroke), Metabolic (T2DM, Insulin Resistance), Neurocognitive (↓Memory, ↑Accidents), NAFLD.

CSA & OHS - Central & Weighty Woes

• Central Sleep Apnea (CSA): No airflow & no respiratory effort (≥10s).
  • Types: Cheyne-Stokes (CHF LVEF ≤45%), high-altitude, drug-induced (e.g., opioids).
  • Dx: PSG shows absent thoracoabdominal effort.
  • Rx: Treat cause, CPAP/BiPAP, ASV (⚠️ HFrEF LVEF ≤45% & predominant CSA).
• Obesity Hypoventilation Syndrome (OHS): BMI ≥30 kg/m², awake PaCO₂ >45 mmHg.
  • Rx: Weight loss (primary), PAP (often BiPAP).

⭐ Adaptive Servo-Ventilation (ASV) is contraindicated in patients with chronic heart failure (LVEF ≤45%) and predominant central sleep apnea due to increased mortality risk (SERVE-HF trial).

High‑Yield Points - ⚡ Biggest Takeaways

• Obstructive Sleep Apnea (OSA): Most common SDB, from recurrent upper airway collapse during sleep.
• Apnea-Hypopnea Index (AHI): Key for diagnosis/severity: Mild (5-15), Moderate (15-30), Severe (>30 events/hr).
• Polysomnography (PSG): Gold standard diagnostic investigation.
• CPAP: First-line treatment for symptomatic moderate-severe OSA.
• Central Sleep Apnea (CSA): Due to impaired central respiratory drive; Cheyne-Stokes respiration is a classic pattern.
• Obesity Hypoventilation Syndrome (OHS): Obesity (BMI ≥30 kg/m²), daytime hypercapnia (PaCO2 >45 mmHg), sleep disordered breathing.
• Untreated OSA significantly increases risk of hypertension, cardiovascular disease, and stroke.