Sleep-Disordered Breathing

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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. Non-obstructed vs. obstructed airway in sleep apnea

⭐ 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)

SeverityAHI (events/hr)
Normal<5
Mild5-14
Moderate15-29
Severe30

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. CPAP device components
  • 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).
FeatureOSACSAOHS
Effort during apneaPresent (paradoxical)AbsentVariable (often present if OSA coexists)
Awake PaCO₂NormalLow/Normal>45 mmHg
Common Assoc.Obesity, craniofacialCHF, stroke, opioidsObesity

⭐ 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.

Practice Questions: Sleep-Disordered Breathing

Test your understanding with these related questions

A 56-year-old woman with diabetes, hypertension, and hyperlipidemia is found to have an A1C of 11 despite her best attempts at diet and faithfully taking her metformin and glyburide. She reports severe fatigue and sleepiness in the daytime, which has limited her ability to exercise. On examination, she is obese, has a full appearing posterior pharynx, clear lungs, a normal heart examination, and trace bilateral edema. Her TSH is 2.0 m/L (normal). Before adding another oral agent or switching to insulin, what is the best next step?

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Flashcards: Sleep-Disordered Breathing

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_____ is associated with loss of orexin from lateral hypothalamus.

TAP TO REVEAL ANSWER

_____ is associated with loss of orexin from lateral hypothalamus.

Narcolepsy

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