Obstructive sleep apnea syndrome (OSAS) is defined as repeated episodes of obstructive apneas and hypopneas during sleep, frequently followed by transient hemoglobin desaturation (hypoxemia) and unconscious (EEG) arousals.

Snoring, episodes of dyspnea, asphyxia or suffocation and body movements are common between apnoeic events; and can cause sleep fragmentation. Feeling of unrefreshing sleep, exhaustion and daytime sleepiness (which is the most common symptom) can severely impair quality of life of the patients. OSAS is considered as an independent risk factor for development of systemic arterial hypertension and cardiovascular events. Its prevalence, using the most rigid diagnostic criteria, is estimated to be 4% and 2% in middle-aged men and women respectively.
Predisposing factors are obesity, congenital or acquired craniofacial and neck defects, menopause, endocrine abnormalities, whereas smoking and alcohol use can precipitate the disorder.

Diagnostic criteria: A, B plus D or C plus D
A- At least one of the following:

1. Sleepiness, hypersomnolence, exhaustion or insomnia.
2. Arousals with feeling of asphyxiation/ suffocation.
3. Snoring, breathing pauses witnessed by sleep partner.

B- Polysomnography findings:

1. Apnea, hypopnea or RERAs ? 5 per hour of sleep.
2. Recording of respiratory effort during part or the whole event.

C- Polysomnography findings:

1. Apnea, hypopnea or RERAs ? 15 per hour of sleep.
2. Recording of respiratory effort during part or the whole event.

D- The disorder cannot be attributed to other conditions, use of medicines or other substances.

Severity criteria: The criteria of the severity of OSAS are a combination of the severity of daytime sleepiness and the value of apnea-hypopnea index (AHI).

• •    Severity assessment of daytime sleepiness can be subjective and objective. Subjective assessment is obtained with questionnaires. Epworth Sleepiness Scale (ESS) is the most commonly used, which has a range of 0-24 and a minimum normal value of 10.
• •    Apnea - Hypopnea Index (AHI) or Respiratory Disturbance Index (RDI)

1. Mild: 5-15 events per hour.
2. Moderate: 15-30 events per hour.
3. Severe: more than 30 events per hour.

Upper airways resistance syndrome: Individuals previously diagnosed with upper airway resistance syndrome (UARS) are now classified as having OSA by the most recent International Classification of Sleep Disorders. UARS refers to RERAs accompanied by symptoms or signs of disturbed sleep.

Central sleep apnea syndrome: Central sleep apnea syndrome (CSAS) can be idiopathic (eg, primary central sleep apnea [CSA]) or secondary. Examples of secondary CSAS include Cheyne-Stokes breathing, CSA due to high altitude periodic breathing, CSA due to a medical condition, and CSA due to a drug or substance. More than 75 percent of events should be central to qualify for this syndrome category.

Primary central sleep apnea: Primary CSA exists when symptoms or signs of disturbed sleep are accompanied by more than five central apneas plus hypopneas per hour of sleep, and normocarbia during wakefulness.

Cheyne-Stokes breathing: Cheyne-Stokes breathing refers to a cyclic pattern of crescendo-decrescendo tidal volumes and central apneas, hypopneas, or both. It is commonly associated with heart failure or stroke.

Hypoventilation syndromes: Patients with a hypoventilation syndrome generally have mild hypercarbia or elevated serum bicarbonate levels when awake, which worsen during sleep.

References:

1. The International Classification of Sleep Disorders, 2nd edition, Diagnostic and Coding Manual, Hauri, PJ, (Ed), Westchester, American Academy of Sleep Medicine, 2005.
2. Chan J, Edman JC, Koltai PJ. Obstructive sleep apnea in children. Am Fam Physician. 2004 Mar 1;69(5):1147-54. [Medline] 

Created: Jan 29, 2010