Obstructive Sleep Apnea

 

• Background

  Aka obstructive sleep apnoea/hypopnea syndrome (OSAHS)

  Pathophysiology

  • Upper airway obstruction leads to episodes of apnoea (≥10 seconds without breathing), usually hundreds in a night. Causes frequent waking, often forgotten by patient, giving saw-tooth pattern of sleep.
  • 90% due to pharyngeal obstruction, resulting from a large neck (especially >40 cm circumference). Common in obesity.
  • Remainder due to retrognathia – a set back mandible – or enlarged tonsils in kids.

  Epidemiology

  • The 3rd commonest respiratory disease after asthma and COPD.
  • Prevalence: 1/30, but rising to 1/4 in those with a BMI >30.

• Signs and symptoms

  • Snoring, gasping, and choking during sleep. Often noticed by partner.
  • Morning headache.
  • Daytime sleepiness. Cognitive or personality changes may also be seen.
  • Apnoeic episodes lead to sympathetic nervous system spikes, causing ↑BP.
  • Kids with OSA due to large tonsils are often hyperactive not sleepy.

• Risk factors

  • Obesity
  • Age
  • Male
  • Alcohol and smoking.
  • Hypothyroidism

• Investigations

  Initial examination:

  • Epworth Sleepiness Scale (ESS) can be used as an initial screen, with a score >10 grounds for referral to a sleep service.
  • Neck circumference and BMI. Also check nasal patency, tongue size, and oropharynx for large tonsils or other obstructions.
  • Metabolic: BP, glucose.

  Polysomnography (PSG) is the standard diagnostic test:

  • Various physiological measures are taken during sleep. Can include EEG, electro-oculogram (EOG), air flow sensors, chest and abdominal movement sensors, pulse oximetry, EMG, and ECG.
  • Can be in hospital ('attended') or at home ('unattended').
  • A more limited form, respiratory PSG – which leaves out the neurophysiology (EEG, EOG, EMG) – is usually sufficient and can be done at home.
  • Calculates the Apnoea-Hypopnea Index (AHI), the number of apnoeas or hypopneas per hour. Alternative is the Respiratory Distress Index (RDI), which also includes respiratory-effort related arousals.
  • Diagnosis of OHA by AHI score: mild ≥5, moderate ≥15, severe >30.

  Other options, if indicated:

  • TFT
  • ABG and lung function tests as there may be co-morbid respiratory disease.
  • Nasolaryngoscopy

• Management

  Lifestyle:

  • Lose weight to below trigger weight.
  • Sleep hygiene: avoid sedatives in the evening including alcohol, and advise sleeping on side.
  • Smoking cessation.
  • Must inform the DVLA if they have OSA and are symptomatic with daytime sleepiness. Can continue to drive if treatment is effective at reducing this.

  Nocturnal continuous positive airway pressure (CPAP):

  • 1st line treatment for symptomatic OSA affecting quality of life. Very effective, reducing symptoms and complications.
  • Can be through nasal or facial mask.
  • Requires initial titration, usually based on response; can be automated with an auto-titrating device (APAP).
  • Requires lots of support in early weeks to help adherence, troubleshoot, and ensure proper use e.g. correct mask fitting.
  • Rhinitis and nasal bridge sores can occur, but can be reduced with better mask fitting.
  • Usually continued life-long.

  Other options:

  • Intra-oral devices (e.g. mandibular advancement devices) can be used in mild OSA with snoring, or a 2nd line if CPAP-intolerant. May only be available through private dentist.
  • Tonsillectomy if large tonsils are the cause.
  • Uvulopalatopharyngoplasty is an option in treatment-resistant OSA, but rarely used.
  • Drugs not routinely recommended, but modafinil may benefit those with daytime sleepiness.

• Complications

  • Sleepiness → car crashes, work accidents.
  • HTN → CVD.
  • Cognitive dysfunction.
  • Insulin resistance and T2 diabetes, as glucose metabolism is disrupted.