Sleep Apnoea

Definition | Classification | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Sleep apnoea is a sleep disorder characterised by repeated episodes of airway obstruction during sleep, leading to intermittent hypoxia, disrupted sleep, and excessive daytime sleepiness. The most common type is obstructive sleep apnoea (OSA).

Classification

Sleep apnoea is classified into:

  • Obstructive Sleep Apnoea (OSA): due to partial or complete collapse of the upper airway during sleep.
  • Central Sleep Apnoea (CSA): caused by impaired respiratory drive from the brainstem.
  • Mixed Sleep Apnoea: a combination of OSA and CSA.

Aetiology

Common causes include:

  • Anatomical Factors: narrow upper airway, large tonsils, or retrognathia (small jaw).
  • Obesity: excess fat around the neck contributes to airway obstruction.
  • Neurological Conditions: impaired control of respiratory muscles.
  • Alcohol and Sedatives: relax upper airway muscles, worsening obstruction.

Pathophysiology

OSA occurs due to repeated collapse of the upper airway during sleep:

  • Airway obstruction causes episodes of hypoxia and hypercapnia.
  • The brain detects oxygen deprivation and momentarily arouses the patient to restore breathing.
  • Repeated arousals lead to fragmented sleep and excessive daytime sleepiness.
  • Chronic intermittent hypoxia contributes to hypertension and cardiovascular disease.

Risk factors

  • Obesity (BMI >30).
  • Large neck circumference (>17 inches in men, >16 inches in women).
  • Male sex (higher prevalence in men).
  • Smoking and alcohol consumption.
  • Family history of sleep apnoea.
  • Chronic nasal obstruction (e.g., allergic rhinitis).

Signs and symptoms

Nocturnal Symptoms:

  • Loud snoring.
  • Episodes of choking, gasping, or witnessed apnoeas.
  • Frequent awakenings or restless sleep.
  • Nocturia (frequent urination at night).

Daytime Symptoms:

  • Excessive daytime sleepiness (falling asleep while reading, watching TV, or driving).
  • Mood disturbances (irritability, depression, poor concentration).
  • Morning headaches due to nocturnal hypoxia.
  • Reduced libido and erectile dysfunction.

Investigations

  • Epworth Sleepiness Scale (ESS): a questionnaire assessing daytime sleepiness (score >10 suggests OSA).
  • Home Sleep Apnoea Test: overnight pulse oximetry to detect oxygen desaturation events.
  • Polysomnography (Sleep Study):
    • Gold standard for diagnosing OSA.
    • Measures apnoea-hypopnoea index (AHI):
      • Mild: AHI 5–14 events/hour.
      • Moderate: AHI 15–30 events/hour.
      • Severe: AHI >30 events/hour.
  • ABG (Arterial Blood Gas): to assess for daytime hypercapnia in severe cases.

Management

1. Lifestyle Modifications:

  • Weight loss (reduces severity of OSA).
  • Smoking and alcohol cessation.
  • Encourage regular exercise.
  • Sleep position therapy (avoiding supine position).

2. Non-Invasive Therapy:

  • Continuous Positive Airway Pressure (CPAP):
    • First-line treatment for moderate-severe OSA.
    • Maintains airway patency with positive pressure.
  • Mandibular Advancement Device (MAD):
    • For mild OSA or those intolerant to CPAP.
    • Holds the lower jaw forward to keep the airway open.

3. Surgical Options:

  • Uvulopalatopharyngoplasty (UPPP): removes excess tissue from the throat.
  • Maxillomandibular Advancement (MMA): moves the jaw forward to create space in the airway.
  • Tracheostomy: last resort for severe, life-threatening OSA.

Referral

Refer to secondary care in the following scenarios:

  • Sleep Specialist: for confirmation of OSA and consideration of CPAP therapy.
  • ENT Specialist: if there are anatomical airway obstructions requiring surgical intervention.
  • Respiratory Specialist: for severe or complex cases requiring long-term management.
  • Hospital admission:
    • Severe OSA with respiratory failure.
    • Significant daytime somnolence affecting activities such as driving.
 
RespiratorymypanotesSleep Apnoea