Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a disorder characterized by recurrent obstruction of the upper airway during sleep, causing hypoxia and fragmented sleep. Obstructive sleep apnea is due to a partial or complete collapse of the upper airway and is associated with snoring, restlessness, sleep interruption, and daytime somnolence. The diagnosis relies on medical history, and polysomnography can confirm the diagnosis. Management includes lifestyle changes, methods of positive airway pressure, and surgical intervention.

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Epidemiology and Classification


  • Most common sleep-related breathing disorder
  • Incidence of approximately 20%–30% in men and 10%–15% in women (note that rates are similar between men and post-menopausal women)
  • Prevalence increases with age with a plateau after the seventh decade.
  • Obesity (body mass index [BMI] > 30) correlates strongly with obstructive sleep apnea (OSA).
  • African Americans are more likely to develop OSA independent of age and BMI.
  • Global prevalence more than doubled from 1990 to 2010 (may relate to increased detection and/or increased rates of obesity)


  • Sleep apnea:
    • Repeated cessation of breathing for > 10 seconds during sleep
    • Results in sleep interruption, fatigue, and daytime sleepiness 
  • Obstructive sleep apnea:
    • Flaccid soft tissues obstruct airway, leading to hypoventilation during sleep
  • Central sleep apnea (CSA):
    • Airflow limitation and/or ventilation problem mediated by aberrant central nervous system
    • May be hyper- or hypoventilation 
  • Mixed sleep apnea:
    • Combination of both OSA and CSA
  • Obesity hypoventilation syndrome (OHS):
    • Extra adipose tissue in obese individuals leads to hypoventilation while awake.
    • Also known as Pickwickian syndrome

Risk Factors and Pathophysiology

Risk factors

  • Obesity:
    • Condition of metabolic or nutritional nature
    • Characterized by accumulation of excess body fat
    • Assessed by BMI, ≥ 30 is considered obese
  • Congenital or acquired craniofacial abnormalities: 
    • Abnormalities of the jaw (micrognathia or retrognathia)
    • Tonsillar hyperplasia
    • Macroglossia
    • Neck circumference > 43 cm (17 in.)
    • Previous airway surgery
    • Nasal polyps (benign lesions of the nasal mucosa that typically present with postnasal drip and nasal obstruction; usually due to chronic inflammation) or septal deviation
    • Hypertrophied pharyngeal muscles
  • Advanced age: increased incidence > 65 years
  • Alcohol consumption before sleep
  • Use of sedatives
  • Acromegaly: excess production of growth hormone by the pituitary gland
  • Hypothyroidism:
    • Deficiency of T3 and T4 hormones
    • Clinical features of hypothyroidism are primarily due to the accumulation of matrix substances and a decreased metabolic rate.
  • Poor muscle tone due to brain injury or neuromuscular disease


  • Sleep results in loss of the wakefulness drive to breathe, decreased motor output to respiratory muscles, decreased upper airway (UA) size, increased UA resistance. 
    • Leads to apneic and hypopneic episodes in susceptible individuals
  • Apneic and hypopneic episodes → increased arterial carbon dioxide (CO2) levels (hypercapnia) → stimulates respiratory efforts against the narrowed upper airway until the individual is awakened
    • Hypercapnia → respiratory acidosis
    • Increased respiratory efforts are achieved by sympathetic effects → secondary tachycardia and hypertension
    • Reduced airflow results in pulmonary hypoxia which triggers pulmonary vasoconstriction (Euler-Liljestrand mechanism) → pulmonary hypertension → cor pulmonale
Obstructive sleep apnea

Illustration of the obstruction of ventilation. Note how the collapse of the pharyngeal muscles and backward placement of the tongue prevent the passage of air.

Image: “Illustration of obstruction of ventilation” by Habib M’henni. License: Public Domain, edited by Lecturio.

Clinical Presentation

  • Often, the patient is unaware of their symptoms and is brought in by their spouse or sleep partner.
  • Symptoms may include:
    • Nocturnal restlessness 
    • Vivid, strange, or threatening dreams 
    • Interrupted sleep, frequent awakenings
    • Snoring, choking, or gasping while asleep
    • Nocturia
    • Diminished ability to concentrate
    • Cognitive deficits
    • Irritability and other changes in mood
    • Morning headaches
    • Daytime sleepiness


  • Suspicion is raised based on a thorough history, including information from bed partner/spouse. A common questionnaire to estimate pretest probability of OSA is:
      • Do you Snore loud enough to be heard through closed doors, or your bed partner elbows you for snoring at night?
      • Do you often feel Tired, fatigued, or sleepy during the day?
      • Has anyone Observed you stop breathing, or choking/gasping during your sleep?
      • Do you have or are you being treated for high blood Pressure?
      • BMI > 35 kg/m2
      • Age older than 50 years?
      • Neck size large: male > 17 inch shirt collar and female > 16 inch shirt collar
      • Gender: male?
    • Low risk of OSA: Yes to 0–2 questions
    • Intermediate risk of OSA: Yes to 3–4 questions
    • High risk of OSA: Yes to 5–8 questions
  • Polysomnography (PSG): gold-standard diagnostic test for OSA
    • Patient is monitored on video overnight while hooked up to electrocardiogram (ECG), electroencephalogram (EEG), pulse oximetry, and nasal prongs to assess snoring, sleep architecture, and physiologic changes during sleep. 
    • The severity of OSA can be determined from the Apnea/Hypopnea index (AHI), which is calculated as the number of apneic episodes per hour of sleep during a sleep study.
      • AHI > 5 = mild OSA
      • AHI > 15 = moderate OSA
      • AHI > 30 = severe OSA
    • If EEG monitoring is used, then the arousal index (AI) can be calculated as the number of arousals per hour of sleep.


Conservative management

Improving modifiable risk factors:

  • Weight loss 
  • Cessation of consumption of sedatives/alcohol
  • Oral appliances or splints during sleep to prevent airway collapse/obstruction

Positive airway pressure devices

  • Continuous positive airway pressure (CPAP): most effective treatment method
    • Noninvasive ventilation that uses positive air pressure to keep airways open
    • Improves restlessness, snoring, cognition, daytime somnolence and quality of life
    • Low adherence rate
  • Bilevel positive airway pressure (BiPAP): provides a higher pressure during inhalation and a lower one during exhalation
Obstructive sleep apnea CPAP

A continuous positive airway machine worn by a sleeping patient with obstructive sleep apnea. Notice how this would cause a low adherence rate due to the bulkiness of the mask and noise of the machine.

Image: “CPAP” by PruebasBMA . License: CC BY-SA 3.0


  • Resection of nasal polyps 
  • Nasal septal deviation correction
  • Reduction of enlarged tonsils or hypertrophied inferior turbinates
  • Uvulopalatopharyngoplasty: resection of uvula, soft palate, tonsils, and excess oropharyngeal tissue
  • Maxillomandibular advancement for patients with retrognathia or micrognathia
  • Tracheotomy: only used in severe refractory life-threatening OSA
  • Bariatric surgery

Clinical Relevance

Possible complications of obstructive sleep apnea:

  • Hypertension: condition defined as a systolic blood pressure ≥ 130 mm Hg and/or a diastolic blood pressure ≥ 80 mm Hg
  • Stroke: acute neurological condition characterized by an impairment in the arterial blood supply to brain tissue. Usually due to a focal vascular cause, such as an embolism or the rupture of an aneurysm 
  • Dementia: term used to group diseases and conditions characterized by a decline in memory, language, problem-solving, and other executive functioning skills
  • Pulmonary hypertension: condition of chronically elevated mean pulmonary arterial pressure ≥ 20 mm Hg
  • Cor pulmonale: also known as right-sided heart failure, a condition characterized by an alteration in the structure and function of the right ventricle of the heart due to a primary disorder of the respiratory system
  • Respiratory failure: insufficient levels of oxygen in the systemic bloodstream, due to inadequate oxygenation of blood or inadequate ventilation or both
  • Cardiac disorders:
    • Arrhythmia: abnormality in the rate or rhythm of the heartbeat
    • Myocardial infarction: ischemic damage to the myocardium, which occurs when blood flow is reduced or completely obstructed to a part of the heart
    • Sudden cardiac death: sudden, unexpected death as a result of cardiac arrest. This occurs within 1 hour of symptom onset. Usually caused by acute coronary syndrome

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