Sleep-Related Breathing Disorders

What is sleep apnea?

Apnea refers to a pause in breathing during which no air can get to the lungs. In adults, an apnea must be 10 seconds (or longer) in order to be considered clinically significant and included in the sleep report. There are two types of sleep apnea: central and obstructive. There are also mixed apneas, characterized by a period of central apnea followed by a period of obstructive apnea in one event.

Central apnea refers to the simultaneous absence of airflow and a pause in respiratory effort.

Central sleep apnea syndrome (CSAS) is a rare condition characterized by central apneas or hypopneas. Several factors such as infectious, tumoral or inflammatory diseases can affect the brainstem and cause CSAS.

CSAS can occur with Cheyne-Stokes Breathing Pattern. It is usually associated with increased ventilatory response to carbon dioxide, which in turn induces respiratory and sleep instability. It is often cause by chronic heart failure.

Obstructive apnea refers to the simultaneous absence of airflow and the maintenance of respiratory movements. Apnea is considered obstructive when the obstruction occurs in the upper airways (pharynx) or tongue. Obstructive apnea is the most common, affecting 5-7% of the general population.

Obstructive sleep apnea syndrome (OSAS) is a term used to define the signs (craniofacial malformation, obesity) and symptoms (morning headaches, excessive daytime sleepiness, slowing of daytime functioning) caused by the presence of repeated apneas and hypopneas. These events may be accompanied by microarousals, which will awaken your brain and regularize your breathing, but will greatly disturb your sleep. This is called sleep fragmentation and is expressed as a change in the sleep architecture: increase in light sleep (non-REM sleep, stages 1, 2) and decrease in deep sleep (non-REM sleep, stage 3). There is a sufficient quantity (amount of time) of sleep but a lack of quality (depth). Apneas and hypopneas may also be accompanied by hypoxemia. Hypoxemia is a risk factor for cardiovascular (hypertension, ischemia) and metabolic (glucose intolerance, elevated glycemia, diabetes) disorders.

NOTE: A symptomatic patient who does not satisfy the clinical criteria for OSAS may suffer from upper airway resistance syndrome (UARS). UARS is a proposed condition for patient with partial narrowing of the upper airways without apnea, hypopnea or oxygen desaturation. It causes an increased effort in breathing and ends with a microarousal: Respiratory Effort-Related Arousal (RERA). The main symptom of UARS is excessive daytime sleepiness. The ICSD-II recommends that UARS be included as part of OSAS and not considered as a separate entity.

The diagnosis of OSAS therefore requires a polysomnography (PSG) to detect sleep disorders that could cause similar symptoms (as UARS) or related sleep disorders, such as snoring, insomnia, sleep-related movement disorders, periodic limb movements, parasomnias, etc. To grade the severity of the OSAS, the number of apneas and hypopneas per hour of sleep is reported as the apnea-hypopnea index (AHI). An AHI above five is considered pathological; however, a sleep specialist will look at both the index and the data collected during the clinical interview (history of the disorder, signs, symptoms, treatments already started, etc.) before making a diagnosis.

Signs of OSAS in adults

Unrestful sleep
Excessive daytime sleepiness
Attention and memory problems (including alertness and concentration)
Mood disorders (depression and anxiety)
Cardiovascular dysfunctions (heart failure, high blood pressure and nocturnal atrial fibrillation)
Metabolic dysfunctions (glucose intolerance, diabetes)
Decreased sex drive
Relationship problems

Apnea in children

Children with OSAS basically present with apneas that last an average of two breaths or more, with or without microarousals. Their sleep architecture is generally normal, with no sleep fragmentation. Hypoxemia is often severe, and arrhythmia and enuresis are often present.

Usually, tonsils are at the root of obstructive episodes in children with OSAS. Maxillofacial abnormalities are also observed. Excessive daytime sleepiness may also be present, especially in older children or teenagers with OSAS. For younger children with OSAS, excessive daytime sleepiness is mostly expressed by an attention-deficit hyperactivity disorder or aggressiveness, as one would see in children of the same age with no breathing disorder but sleep deprived. OSAS occurs in 2% of young children; however, the prevalence is unknown in older children and teenagers. Moreover, the diagnosis of OSAS requires a polysomnographic (PSG) recording of the sleep. Adentonsillectomy is the most common treatment for OSAS in children.
Signs of OSAS in children

Morning headaches
ADHD (attention-deficit hyperactivity disorder) or aggressive behaviour and sometimes excessive daytime sleepiness
Metabolic dysfunctions
A slow rate of growth (reduction in the production of the growth hormone

How is apnea treated?

A PSG is always used to diagnose sleep apneas. This test evaluates the number and severity of apneas and shows related events (leg movements, pulse, arousals, etc). There are several treatments for eliminating or reducing sleep apneas:

1. Change of habits or lifestyle. According to the physician’s recommendations, physical exercise could be integrated into the daily routine to control weight, but also to improve mood and heart health, two factors that are affected by sleep apnea. Moreover, it is crucial that special attention be paid to certain drinks or habits, such as tobacco, alcohol, coffee, and exercise. Sleep hygiene measures should be instituted. Sleeping on one’s side may help some patients greatly improve their condition by allowing the soft tissues (back of the throat) to open up and thus facilitate the passage of air.

2. Positive airway pressure (PAP). PAP treatment is the most effective and easiest way to treat sleep apneas. The machine delivers compressed air via a flexible hose to a nasal cannula or nose mask. The air keeps the upper airways (pharynx) open, preventing apneas. The amount of air pressure needed is different for each person. A polysomnography, during which the person receives PAP treatment as he/she sleeps, will help your physician to determine the right level for you.

NOTE: Effectively treating sleep apnea with PAP therapy may result in disorders of arousal (primary parasomnias during non-REM sleep), which are presumably associated with deep Non-REM sleep rebounds.

3. Oral appliance. An oral appliance that moves the lower jaw forward, opening up the back of the throat. Oral appliances are sometimes less effective than PAP machines, but some patients find them easier to tolerate.

4. Surgery. Surgery, the most effective treatment for snoring, may be recommended to treat severe cases of sleep apnea. However, it has its limitations: maxillomandibular advancement (MMA), for people with facies anomalies, has a high success rate but long term effects are yet to be confirmed. For children, tonsillar hypertrophy is the leading cause of sleep apnea and must be treated with a tonsillectomy, which has a very high rate of effectiveness.


Consult your physician or dentist for more information on sleep apnea treatments.


American Academy of Sleep Medicine. International Classification of Sleep Disorders: Diagnostic and Coding Manual. 2nd ed. Rochester, 2005.

American Academy of Sleep Medicine. “Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research; The Report of an American Academy of Sleep Medicine task force.” Sleep. 22 (1999): 667-689.

Phillips, B and Kryger, MH. “Management of Obstructive Sleep Apnea/Hypopnea Syndrome: Overview.” Principles and Practice of Sleep Medicine. 4th ed. Edited by MH Kryger, T. Roth and Dement WC. 2005.