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What is sleep apnea?

Sleep apnea (or sleep apnoea in British English; is a sleep disorder characterized by abnormal pauses in breathing or instances of abnormally low breathing during sleep.

Each pause in breathing, called an apnea, can last from at least ten seconds to minutes, and may occur 5 to 30 times or more an hour.

Similarly, each abnormally low breathing event is called a hypopnea.

Sleep apnea is often diagnosed with an overnight sleep test called a polysomnogram, or "sleep study".

There are three forms of sleep apnea: central (CSA), obstructive (OSA), and complex or mixed sleep apnea (i.e. a combination of central and obstructive) constituting 0.4%, 84% and 15% of cases respectively.

In CSA, breathing is interrupted by a lack of respiratory effort; in OSA, breathing is interrupted by a physical block to airflow despite respiratory effort, and snoring is common.

Regardless of type, an individual with sleep apnea is rarely aware of having difficulty breathing, even upon awakening.

Sleep apnea is recognized as a problem by others witnessing the individual during episodes or is suspected because of its effects on the body (sequelae).

Symptoms may be present for years (or even decades) without identification, during which time the sufferer may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance.

Sleep apnea affects not only adults but some children as well.

As stated by El-Ad, "patients complain about excessive daytime sleepiness (EDS) and impaired alertness".

In other words, common effects of sleep apnea include daytime fatigue, a slower reaction time, and vision problems.

Diagnosis.
The diagnosis of sleep apnea is based on the conjoint evaluation of clinical symptoms (e.g. excessive daytime sleepiness and fatigue) and of the results of a formal sleep study (polysomnography, or reduced channels home based test).

The latter aims at establishing an "objective" diagnosis indicator linked to the quantity of apneic events per hour of sleep (Apnea Hypopnea Index(AHI), or Respiratory Disturbance Index (RDI)), associated to a formal threshold, above which a patient is considered as suffering from sleep apnea, and the severity of their sleep apnea can then be quantified. Mild OSA (Obstructive Sleep Apneas) ranges from 5 to 14.9 events per hour of sleep, moderate OSA falls in the range of 15–29.9 events per hour of sleep, and severe OSA would be a patient having over 30 events per hour of sleep.

Obstructive sleep apnea.

Obstructive sleep apnea (OSA) is the most common category of sleep-disordered breathing.

The muscle tone of the body ordinarily relaxes during sleep, and at the level of the throat the human airway is composed of collapsible walls of soft tissue which can obstruct breathing during sleep.

Mild occasional sleep apnea, such as many people experience during an upper respiratory infection, may not be important, but chronic severe obstructive sleep apnea requires treatment to prevent low blood oxygen (hypoxemia), sleep deprivation, and other complications.

Individuals with low muscle tone and soft tissue around the airway (e.g., because of obesity) and structural features that give rise to a narrowed airway are at high risk for obstructive sleep apnea.

The elderly are more likely to have OSA than young people.

Men are more likely to suffer sleep apnea than women and children are, though it is not uncommon in the last two population groups

The risk of OSA rises with increasing body weight, active smoking and age.

In addition, patients with diabetes or "borderline" diabetes have up to three times the risk of having OSA.

Common symptoms include loud snoring, restless sleep, and sleepiness during the daytime. Diagnostic tests include home oximetry or polysomnography in a sleep clinic.

Some treatments involve lifestyle changes, such as avoiding alcohol or muscle relaxants, losing weight, and quitting smoking.

Snoring is a common finding in people with this syndrome.

Snoring is the turbulent sound of air moving through the back of the mouth, nose, and throat.

Other indicators include (but are not limited to): hypersomnolence, obesity BMI >30, large neck circumference (16 in (410 mm) in women, 17 in (430 mm) in men), enlarged tonsils and large tongue volume, micrognathia, morning headaches, irritability/mood-swings/depression, learning and/or memory difficulties, and sexual dysfunction.

Central sleep apnea.
In pure central sleep apnea or Cheyne–Stokes respiration, the brain's respiratory control centers are imbalanced during sleep.

Blood levels of carbon dioxide, and the neurological feedback mechanism that monitors them, do not react quickly enough to maintain an even respiratory rate, with the entire system cycling between apnea and hyperpnea, even during wakefulness.

The sleeper stops breathing and then starts again. There is no effort made to breathe during the pause in breathing: there are no chest movements and no struggling.

After the episode of apnea, breathing may be faster (hyperpnea) for a period of time, a compensatory mechanism to blow off retained waste gases and absorb more oxygen.

In central sleep apnea, the basic neurological controls for breathing rate malfunction and fail to give the signal to inhale, causing the individual to miss one or more cycles of breathing.

If the pause in breathing is long enough, the percentage of oxygen in the circulation will drop to a lower than normal level (hypoxaemia) and the concentration of carbon dioxide will build to a higher than normal level (hypercapnia).

Normal Respiratory Drive
After exhalation, the blood level of oxygen decreases and that of carbon dioxide increases. Exchange of gases with a lungful of fresh air is necessary to replenish oxygen and rid the bloodstream of built-up carbon dioxide.

Oxygen and carbon dioxide receptors in the blood stream (called chemoreceptors) send nerve impulses to the brain, which then signals reflex opening of the larynx (so that the opening between the vocal cords enlarges) and movements of the rib cage muscles and diaphragm.

These muscles expand the thorax (chest cavity) so that a partial vacuum is made within the lungs and air rushes in to fill it.

Physiologic effects of central apnea.

During central apneas, the central respiratory drive is absent, and the brain does not respond to changing blood levels of the respiratory gases.

No breath is taken despite the normal signals to inhale.

The immediate effects of central sleep apnea on the body depend on how long the failure to breathe endures.

At worst, central sleep apnea may cause sudden death.

Short of death, drops in blood oxygen may trigger seizures, even in the absence of epilepsy. In people with epilepsy, the hypoxia caused by apnea may trigger seizures that had previously been well controlled by medications.

Mixed apnea and complex sleep apnea.
Some people with sleep apnea have a combination of both types.

When obstructive sleep apnea syndrome is severe and longstanding, episodes of central apnea sometimes develop.

The exact mechanism of the loss of central respiratory drive during sleep in OSA is unknown but is most commonly related to acid–base and CO2 feedback malfunctions stemming from heart failure.

There is a constellation of diseases and symptoms relating to body mass, cardiovascular, respiratory, and occasionally, neurological dysfunction that have a synergistic effect in sleep-disordered breathing.

In some cases, a side effect from the lack of sleep is a mild case of Excessive Daytime Sleepiness (EDS) where the subject has had minimal sleep and this extreme fatigue over time takes its toll on the subject.

Research is ongoing, however, at the Harvard Medical School, including adding dead space to positive airway pressure for treatment of complex sleep-disordered breathing.

Treatment.
Treatment often starts with behavioral therapy.

Many patients are told to avoid alcohol, sleeping pills, and other sedatives, which can relax throat muscles, contributing to the collapse of the airway at night.

Possibly owing to changes in pulmonary oxygen stores, sleeping on one's side (as opposed to on one's back) has been found to be helpful for central sleep apnea with Cheyne–Stokes respiration.

Medications.
Medications like acetazolamide lower blood pH and encourage respiration. Low doses of oxygen are also used as a treatment for hypoxia but are discouraged due to side effects.

Oral appliances.
General dentists can fabricate an oral appliance.

The oral appliance, called a mandibular advancement splint, is a custom-made mouthpiece that shifts the lower jaw forward and opens the bite slightly, which opens up the airway.

Oral appliance therapy (OAT) is usually successful in patients with mild to moderate obstructive sleep apnea. OAT is a relatively new treatment option for sleep apnea in the United States, but it is much more common in Canada and Europe.

Continuous positive airway pressure.

For moderate to severe sleep apnea, the most common treatment is the use of a continuous positive airway pressure (CPAP) or automatic positive airway pressure (APAP) device, which 'splints' the patient's airway open during sleep by means of a flow of pressurized air into the throat.

The patient typically wears a plastic facial mask, which is connected by a flexible tube to a small bedside CPAP machine.

The CPAP machine generates the required air pressure to keep the patient's airways open during sleep.

Advanced models may warm or humidify the air and monitor the patient's breathing to ensure proper treatment.

Although CPAP therapy is extremely effective in reducing apneas and less expensive than other treatments, some patients find it extremely uncomfortable.

Many patients refuse to continue the therapy or fail to use their CPAP machines on a nightly basis, especially in the long term.

One way to ensure CPAP therapy remains comfortable and effective for patients is to carefully consider the right CPAP face mask to be used.

CPAP masks come in different shapes, sizes and materials to ensure effective treatment for obstructive sleep apnea. It is important to select the right mask to fit each patient.

It is not clear that CPAP reduces hypertension or cardiovascular events in patients who do not have daytime sleepiness; however, the lack of benefit may be partly due to noncompliance with therapy.

Surgery.
Several surgical procedures are used to treat sleep apnea, although they are normally a second line of treatment for those who reject CPAP treatment or are not helped by it.

Surgical treatment for obstructive sleep apnea needs to be individualized in order to address all anatomical areas of obstruction.

Often, correction of the nasal passages needs to be performed in addition to correction of the oropharynx passage.

Septoplasty and turbinate surgery may improve the nasal airway.

Tonsillectomy and uvulopalatopharyngoplasty (UPPP or UP3) are available to address pharyngeal obstruction.

Base-of-tongue advancement by means of advancing the genial tubercle of the mandible may help with the lower pharynx.

Many other treatments are available, including hyoid bone myotomy and suspension and various radiofrequency technologies.

Other surgery options may attempt to shrink or stiffen excess tissue in the mouth or throat; procedures done at either a doctor's office or a hospital.

Small shots or other treatments, sometimes in a series, are used for shrinkage, while the insertion of a small piece of stiff plastic is used in the case of surgery whose goal is to stiffen tissues.

The Pillar Procedure is a minimally invasive treatment for snoring and obstructive sleep apnea.

This procedure was FDA indicated in 2004. During this procedure, three to six or more Dacron (the material used in permanent sutures) strips are inserted into the soft palate, using a modified syringe and local anesthetic.

While the procedure was initially approved for the insertion of three "pillars" into the soft palate, it was found that there was a significant dosage response to more pillars, with appropriate candidates.

After this brief and virtually painless outpatient operation, which usually lasts no more than 30 minutes, the soft palate is more rigid and snoring and sleep apnea can be reduced.

This procedure addresses one of the most common causes of snoring and sleep apnea vibration or collapse of the soft palate (the soft part of the roof of the mouth).

Several inpatient and outpatient procedures use sedation.

Many drugs and agents used during surgery to relieve pain and to depress consciousness remain in the body at low amounts for hours or even days afterwards.

Surgery on the mouth and throat, as well as dental surgery and procedures, can result in postoperative swelling of the lining of the mouth and other areas that affect the airway.

Even when the surgical procedure is designed to improve the airway, such as tonsillectomy and adenoidectomy or tongue reduction, swelling may negate some of the effects in the immediate postoperative period.

Once the swelling resolves and the palate becomes tightened by postoperative scarring, however, the full benefit of the surgery may be noticed.

Alternative treatments.
Other studies have also suggested that strengthening the muscles around the upper airway may combat sleep apnea.

A 2001 study investigated changes after Tongue Muscle Training (ZMT®) in respiratory parameters during night-time sleep of patients with increased respiratory disease index. 40 sleep apnea patients, which up to this time had been treated with nCPAP, underwent electrostimulation of the suprahyoidal musculature for 5 weeks with a special EMS-device.

The apnea, hypopnea and desaturation indexes were reduced in 26 of the 40 patients (65%) by an average of approximately one half.

A 2005 study in the British Medical Journal found that learning and practicing the didgeridoo helped reduce snoring and sleep apnea as well as daytime sleepiness.

This appears to work by strengthening muscles in the upper airway, thus reducing their tendency to collapse during sleep.

A 2009 study published in the American Journal of Respiratory and Clinical Care Medicine found that patients who practiced a series of tongue and throat exercises for 30 minutes a day showed a marked decline in sleep apnea symptoms after three months. Patients experienced an average of 39% fewer apnea episodes after successfully completing the treatments.


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