Harvey's Garden

Obstructive sleep apnea

Properties2
tags—
aliasesOSA

2 min read

Epidemiology

Etiology

  • Obesity (BMI > 30 kg/m²).
  • Increased neck circumference (>17 inches in M; >16 inches in F).
  • Anatomic narrowing: Tonsillar/adenoid hypertrophy (most common cause in peds), macroglossia (Down syndrome, acromegaly), micrognathia/retrognathia.
  • Systemic dz: Hypothyroidism.
  • Demographics: Older age, male sex.

Pathophysiology

  • Obstruction of the upper airways → apnea → ↓ partial pressure of oxygen in arterial blood (PaO2), ↑ partial pressure of carbon dioxide in arterial blood (PaCO2, also known as hypercapnia), which leads to:
    • ↑ Hypoxic pulmonary vasoconstriction → ↑ pulmonary hypertension → cor pulmonale
    • ↑ Sympathetic activity → secondary hypertension c
    • Respiratory acidosis → renal compensation → increased HCO3− retention and decreased chloride reabsorption

Clinical features

  • History:
    • Daytime somnolence (excessive daytime sleepiness). c
    • Witnessed apneas/gasping/choking episodes during sleep, loud snoring.
    • Morning headaches (due to nocturnal hypercapnia/vasodilation), unrefreshing sleep.
    • Cognitive dysfunction, irritability, nocturia.
  • Physical Examination:
    • Neck circumference >17 inches (men) or >16 inches (women).
    • High Mallampati score (III or IV).
    • Systemic HTN (frequently resistant to multiple agents).
    • Pulmonary hypertension and cor pulmonale
      • edema

Diagnostics

Tip

In OSA, hypercapnia is usually absent when the patient is awake. This fact explains why arterial blood gases would be mostly normal in a patient with OSA. Therefore, this test is not useful for diagnosis.

  • Initial/Screening: STOP-BANG questionnaire, Epworth Sleepiness Scale.
  • Confirmatory/Gold Standard: In-lab Polysomnography (PSG). c
    • Diagnostic Criteria: Apnea-Hypopnea Index (AHI) ≥ 15 events/hr, OR AHI ≥ 5 events/hr with associated symptoms (daytime sleepiness, waking gasping) or comorbidities (HTN, CAD).
  • Alternative: Home Sleep Apnea Testing (HSAT) if high pre-test probability and no significant cardiopulmonary comorbidities.
  • Key Labs: CBC showing secondary erythrocytosis (due to chronic nocturnal hypoxemia), TSH (to rule out hypothyroidism).

Treatment

  • First-Line:
    • Continuous Positive Airway Pressure (CPAP): Most effective treatment. Acts as a pneumatic splint to maintain airway patency.
    • Lifestyle Modifications: Weight loss (most effective non-device intervention), avoidance of alcohol/sedatives, positional therapy (avoiding supine position).
  • Second-Line/Alternative:
    • Oral appliances: Mandibular advancement devices for mild-to-moderate OSA or patients intolerant of CPAP.
    • Surgery: Uvulopalatopharyngoplasty (UPPP) or hypoglossal nerve stimulation in select cases.

Upper airway modification

  • Description: surgical dilatation of the upper airway or neurostimulation of upper airway muscles
  • Procedures
    • Uvulopalatopharyngoplasty: resection of the uvula and redundant retrolingual, soft palate, and tonsillar tissue
    • Other procedures include hypoglossal nerve stimulation, radiofrequency ablation of tongue and/or soft palate tissue, and palatal implants.

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