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
- 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
- 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
- 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
- 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
- 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.
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
- 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
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