Obstructive sleep apnea

Obstructive Sleep Apnea

Sleep apnea flow model

Sleep Apnea Los Angeles

Depiction of a Sleep Apnea patient using a CPAP machine

Obstructive sleep apnea (OSA) is the most common type of sleep apnea, characterized by repeated episodes of complete or partial obstructions of the upper airway during sleep, despite the effort to breathe, and is usually associated with a reduction in blood oxygen saturation. In the Obstructive Sleep Apnea-Hypopnea Syndrome, the episodes of decreased breathing are called "hypopnea," and its definition requires a ≥30% drop in flow for 10 seconds or longer, associated with ≥3% oxygen desaturation. The episodes of breathing cessations are called "apneas" (literally, "without breath"), and to be defined, a ≥90% drop in flow for 10 seconds or longer must be assessed and associated with ≥3% oxygen desaturation or an arousal.

Classification

In the third edition of the International Classification of Sleep Disorders (ICSD-3), Obstructive Sleep Apnea is classified among the Sleep-Related Breathing Disorders and is divided into two categories, namely adult OSA and pediatric OSA.

Differentiated from central sleep apnea

Obstructive Sleep Apnea is differentiated from Central Sleep Apnea (CSA), characterized by changes in the respiratory cycle during sleep but without the effort to breathe during the apnea.

Respiratory effort

The respiratory effort must then be assessed to correctly classify the apnea as obstructive, given the specificity of the diaphragmatic activity in this condition: the inspiratory effort is continued or increased through the entire episode of absent airflow. When hypopneas are present alongside apneas, the term Obstructive Sleep Apnea-Hypopnea is used, and when it is associated with daytime sleepiness and other daytime symptoms, it is called Obstructive Sleep Apnea-Hypopnea Syndrome. To be categorized as Obstructive, the hypopnea must meet one or more of the following symptoms: (1) snoring during the event, (2) increased oronasal flow flattening, and/or (3) thoraco-abdominal paradoxical respiration during the event. If none of them are present during the event, it is categorized as central hypopnea.

Not self-aware

Individuals with OSA are rarely aware of difficulty breathing, even upon awakening. It is often recognized as a problem by others who observe the individual during episodes or is suspected because of its effects on the body. OSA is commonly accompanied by snoring. The terms obstructive sleep apnea syndrome or obstructive sleep apnea–hypopnea syndrome are used to refer to OSA when it is associated with symptoms during the daytime (e.g., excessive daytime sleepiness, decreased cognitive functions). Symptoms may be present for years or even decades without identification, during which time the individual may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance. Individuals who generally sleep alone are often unaware of the condition, without a regular bed-partner to notice and make them aware of the signs.

As the muscle tone of the body ordinarily relaxes during sleep, and the airway at the throat is composed of walls of soft tissue, which can collapse, it is not surprising that breathing can be obstructed during sleep. Although a minor degree of OSA is considered to be within the bounds of normal sleep, and many individuals experience episodes of OSA at some point in life, a small percentage of people have chronic, severe OSA.

Many people experience episodes of OSA for only a short period. This can be the result of an upper respiratory infection that causes nasal congestion, along with swelling of the throat or tonsillitis that temporarily produces very enlarged tonsils. The Epstein-Barr virus, for example, is known to be able to dramatically increase the size of lymphoid tissue during acute infection, and OSA is fairly common in acute cases of severe infectious mononucleosis. Temporary spells of OSA syndrome may also occur in individuals who are under the influence of a drug (such as alcohol) that may relax their body tone excessively and interfere with normal arousal from sleep mechanisms.

Diagnosis of OSA

Diagnosis of OSA is often based on a combination of patient history and tests, which can be lab- or home-based. These tests range, in decreasing order of cost, complexity and tethering of the patient (number and type of channels of data recorded), from lab-attended full polysomnography ("sleep study") down to single-channel home recording. Reimbursement rules vary among countries.

The diagnosis of OSA syndrome is made when the patient shows recurrent episodes of partial and complete collapse of the upper airway during sleep, resulting in hypopnea and apneas – hypopnea being the reduction of airflow and apnea its complete cessation, both despite active efforts to breathe. To define the severity of the condition, the Apnea-Hypopnea Index (AHI) or the Respiratory Disturbance Index (RDI) are used. While the AHI measures the mean number of apneas and hypopneas per hour of sleep, the RDI adds to this measure the respiratory effort-related arousals (RERAs). The OSA syndrome is thus diagnosed if AHI > 5 episodes per hour and results in daytime sleepiness and fatigue, or when RDI ≥ 15 independently of the symptoms. Daytime sleepiness can be assessed with the Epworth Sleepiness Scale (ESS), a self-reported questionnaire on the propensity to fall asleep or doze off during daytime. Screening tools for OSA itself comprise the STOP questionnaire, the Berlin questionnaire, and the STOP-BANG questionnaire.

Criteria

According to the International Classification of Sleep Disorders, there are 4 types of criteria. The first one concerns sleep - excessive sleepiness, nonrestorative sleep, fatigue, or insomnia symptoms. The second and third criteria are about respiration - waking with breath holding, gasping, or choking; snoring, breathing interruptions or both during sleep. The last criterion revolves around medical issues as hypertension, coronary artery disease, stroke, heart failure, atrial fibrillation, type 2 diabetes mellitus, mood disorder or cognitive impairment. Two levels of severity are distinguished, the first one is determined by a polysomnography or home sleep apnea test demonstrating 5 or more predominantly obstructive respiratory events per hour of sleep and the higher levels are determined by 15 or more events. If the events are present less than 5 times per hour, no obstructive sleep apnea is diagnosed.

Polysomnography

• AHI Rating
• <5 Normal
• 5-15 Mild
• 15-30 Moderate
• >30 Severe

Polysomnography in diagnosing OSA characterizes the pauses in breathing. As in central apnea, pauses are followed by a relative decrease in blood oxygen and an increase in the blood carbon dioxide. Whereas in central sleep apnea the body's motions of breathing stop, in OSA the chest not only continues to make the movements of inhalation, but the movements typically become even more pronounced. Monitors for airflow at the nose and mouth demonstrate that efforts to breathe are not only present but that they are often exaggerated. The chest muscles and diaphragm contract and the entire body may thrash and struggle.

An "event" can be either an apnea, characterized by complete cessation of airflow for at least 10 seconds, or a hypopnea in which airflow decreases by 50 percent for 10 seconds or decreases by 30 percent if there is an associated decrease in the oxygen saturation or an arousal from sleep. To grade the severity of sleep apnea, the number of events per hour is reported as the apnea-hypopnea index (AHI). An AHI of less than 5 is considered normal. An AHI of 5-15 is mild; 15-30 is moderate and more than 30 events per hour characterizes severe sleep apnea.

Home Oximetry

In patients who are at high likelihood of having OSA, a randomized controlled trial found that home oximetry (a non-invasive method of monitoring blood oxygenation) may be adequate and easier to obtain than formal polysomnography. High probability patients were identified by an Epworth Sleepiness Scale (ESS) score of 10 or greater and a Sleep Apnea Clinical Score (SACS) of 15 or greater. Home oximetry, however, does not measure apneic events or respiratory event-related arousals and thus does not produce an AHI value.

Home Sleep Study

A home sleep study, also known as a home sleep apnea test (HSAT), is a simplified sleep test used to diagnose obstructive sleep apnea (OSA) in the comfort of a patient's own home. This test is often recommended for individuals with a high likelihood of having moderate to severe OSA and without other significant medical conditions or sleep disorders.

During a home sleep study, the patient is provided with a portable monitoring device that measures various parameters, including airflow, respiratory effort, blood oxygen levels, and sometimes heart rate. The device typically consists of a small unit with sensors and belts that are attached to the body as instructed. The patient then sleeps with the device overnight, recording data related to their sleep and breathing patterns.

After the test is completed, the device is returned to the healthcare provider or sleep center for data analysis. A sleep specialist will review the recorded data and determine if OSA is present and, if so, the severity of the condition based on the Apnea-Hypopnea Index (AHI).

Treatment and Management

Treatment for OSA depends on the severity of the condition and the presence of any underlying health issues. Lifestyle changes, such as weight loss, avoiding alcohol and sedatives, and changing sleep positions, may help alleviate mild cases of OSA. For moderate to severe cases, treatments may include:

• Continuous Positive Airway Pressure (CPAP): CPAP is a common and effective treatment for OSA. It involves wearing a mask over the nose and/or mouth during sleep, which delivers a constant stream of air to keep the airway open.
• Oral Appliances: Oral devices, also known as dental appliances or mandibular advancement devices, can help to maintain an open airway during sleep. These devices reposition the lower jaw and tongue forward, preventing the airway from collapsing.
• Surgery: In some cases, surgery may be recommended to treat OSA. Surgical options include uvulopalatopharyngoplasty (UPPP), tonsillectomy, adenoidectomy, or genioglossus advancement. The type of surgery will depend on the specific cause of the airway obstruction.
• Positional Therapy: For some individuals, OSA occurs primarily when sleeping in a specific position (e.g., on the back). Positional therapy involves using devices or techniques to help maintain a side-sleeping position during the night.
• Hypoglossal Nerve Stimulation: This is a relatively new treatment for OSA, which involves the implantation of a device that stimulates the hypoglossal nerve, causing the tongue to move forward and helping to maintain an open airway during sleep.
• Proper diagnosis and treatment of OSA can lead to improved sleep quality, reduced daytime sleepiness, and a decreased risk of associated health problems, such as high blood pressure, heart disease, and stroke. It is important for individuals who suspect they may have OSA to consult with a healthcare professional for evaluation and appropriate treatment.

See also

• Congenital central hypoventilation syndrome
• Obesity hypoventilation syndrome
• Periodic breathing
• Respiratory disturbance index (RDI)
• Upper airway resistance syndrome

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