Obstructive Sleep Apnea

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What is Obstructive Sleep Apnea?

Obstructive Sleep Apnea (OSA), also referred to as Obstructive Sleep Apnea Syndrome or Obstructive sleep apnea-hypopnea (OSAH), is a condition that is characterized by repetitive cessations of breathing during sleep in spite of persistent efforts to breathe in. It is the most commonly occurring form of sleep apnea.

Obstructive Sleep Apnea ICD-9 Code

The ICD-9 code for OSA is 327.23.

Obstructive Sleep Apnea Epidemiology

It is the most common sleep disorder related to difficulty in breathing. Although occurring in various areas throughout the world, it has a higher prevalence in western countries. During mid-90s, around 6% to 7% of men and 3% to 4% of women were believed to be affected by this disorder.

Obstructive Sleep Apnea Causes

An obstruction of the upper airway is the main cause for this syndrome and the condition is generally associated with reduction in the blood oxygen saturation. The pauses in breathing are known as apneas, which means “without breath,” and they generally last for about 20-40 seconds. Individuals having OSA are rarely aware that they are having breathing-related difficulties, even when they are awake. However, people around OSA-affected individuals can recognize this as a problem by witnessing them during such episodes or by noticing the effects of these apneas on the patients’ bodies. This syndrome is also commonly followed by snoring. Obstructive sleep apnea can be normal, mild, moderate or chronic and severe, based on the degree of intensity.

The following causes are believed to be responsible for most cases of OSA:

  • Decreased muscle tone
  • Old age (premature or natural)
  • Brain injury (permanent or temporary)
  • Structural features which give rise to narrowed airway
  • An increase in soft tissue around airway (occasionally due to obesity)

A decrease in the muscle tone may occur due to alcohol or drugs, or it can occur due to neurological problems or some other disorders. Certain individuals might have more than one of the above-mentioned issues. According to a theory, long-term snoring can give rise to local nerve lesions within the pharynx in the same way as prolonged exposure to vibrations might give rise to nerve lesions in the other areas of the body.

Certain craniofacial syndromes may give rise to abnormal facial features. Some of these syndromes are genetic, while others develop due to unknown causes. Such conditions may involve the nose, the mouth and jaw, as well as the resting muscle tone and increase the risks for OSA. A condition known as Down syndrome may lead to the development of low muscle tone, a narrow nasopharynx as well as a large tongue, which greatly increases the chances of obstructive sleep apnea. In fact, more than 50% of people having Down syndrome eventually get affected by this sleep disorder. Other factors include obesity, adenoids and enlarged tonsils. In cases of certain other craniofacial conditions, the abnormal features associated with them may even improve the airway. However, corrective surgeries to rectify such craniofacial problems may increase the risks of development of OSA. An example of such a craniofacial condition includes cleft palate. Other craniofacial difficulties include Pierre Robin sequence and Treacher Collins syndrome.

Obstructive sleep apnea may also develop as a major post-operative complication of pharyngeal flap surgery which is used to treat velopharyngeal inadequacy (VPI). Surgical treatment for curing Velopalatal insufficiency may also give rise to this sleep disorder.

Obstructive Sleep Apnea Risk Factors

A number of factors can increase the risk of development of this syndrome. One of this is old age, which is frequently accompanied by a muscular as well as neurological loss of the muscle tone of upper airway. Reduced muscle tone can also be temporarily caused by alcoholic drinks, sedative medications and chemical depressants. Permanent premature loss of muscle tone in upper airway can occur due to neuromuscular disorders, traumatic brain injury, or a lack of adherence to chemical and/or speech-therapy treatments. People having reduced muscle tone, an increase in soft tissues around the airway as well as structural features giving rise to narrowed airway are more prone to develop this sleep disorder. Men having increased mass around torso and neck make up a vulnerable group especially during the middle ages or later. Women are more inclined to develop OSA during pregnancy.

Obstructive sleep apnea may also have a genetic aspect to it, with more people having a family history of this condition getting affected by it. Habits such as smoking can also increase the risk of development of this condition. Consuming alcohol, sedatives, or other sleep-inducing medications can also act as potent risk factors because most of these substances also act as muscle relaxants. People with hypertension, chronic nasal congestion, and diabetes forms a high risk group for this disorder. The condition can also develop in individuals suffering from severe infectious mononucleosis caused by the Epstein-Barr virus.

Obstructive Sleep Apnea Pathophysiology

Normal sleep/wake cycle in the adult population can be divided into three states:

  • Rapid eye movement (REM) sleep
  • Non-REM (NREM) sleep
  • Consciousness

The NREM sleep can be further divided into Stage 1, 2 and 3. The stage 3 of non-REM is the deepest stage which is needed for attaining the physically restorative influence of sleep. It is also the stage where the human growth hormone is released in pre-adolescents. The non-REM Stage 2 and the REM together make up 70% of the total sleep time of an average person, and are essentially associated with the mental recovery as well as maintenance of the individual. During REM sleep, the muscle tone of throat and neck and most of the skeletal muscles are almost entirely attenuated, which allows the tongue and the soft palate/oropharynx to completely relax. In sleep apnea patients, it also impedes flow of air that may differ in degrees, ranging from light snoring to a complete collapse. If the airflow gets reduced to a state where the levels of blood oxygen fall or the effort to breathe is great, the neurological mechanisms elicit a sudden disruption of sleep known as a neurological arousal. Such arousals rarely lead to complete awakening, but may weaken the restorative effects of sleep. This leads to sleep deprivation caused by repetitive disruption and continuation of sleep activity. Interruption of sleep during the stage 3, or the slow-wave sleep as well as in the REM sleep stage can greatly interfere with the normal growth patterns, the healing abilities, and immune response, mainly in children or young adults.

Obstructive Sleep Apnea Symptoms

The most common signs and symptoms of OSA include:

  • Anxiety
  • Insomnia
  • Irritability
  • Depression
  • Mood swings
  • Forgetfulness
  • Restless sleep
  • Heavy night sweats
  • Decreased sex drive
  • Morning headaches
  • Unexplained weight gain
  • Difficulty in concentration
  • Unexplained daytime sleepiness
  • Increased urination and nocturia
  • Increased heart rate and blood pressure
  • Sore throat or dry mouth upon awakening
  • Frequent instances of heartburn or gastroesophageal reflux disease
  • Loud snoring, accompanied by periods of silence that are followed by gasps

Adults with OSA frequently suffer from obesity, especially gaining heaviness around the neck and face. However, many adults having normal BMIs (body mass indices) have reduced muscle tone leading to sleep apnea and airway collapse. Excessive daytime sleepiness is the hallmark of OSA in adults. Individuals having severe long-standing OSA might fall asleep for short periods during daytime provided they get any opportunity to rest or sit. This tendency can be quite dramatic, even occurring during conversations at social gatherings. Absence of oxygen or hypoxia can cause changes in neurons of hippocampus and right frontal cortex. Hippocampal atrophy can also occur in some extreme cases. Some individuals have been found to have problems with mental manipulation of non-verbal information as well as in executive function.

Although excessive sleepiness or hypersomnolence can also be noticed in children, it is not typical of all young children affected by sleep apnea. Signs of overexhaustion or hyperactivity may be observed in children and toddlers (pediatric cases) with OSA. Poor growth is observed in these children due to intense breathing which leads to faster burning of calories as well as obstruction of nose and throat which makes consumption of food a physically uncomfortable experience. Learning difficulties and memory deficits can also be observed in these children, leading to low IQ scores. Other symptoms may include bedwetting, drooling or choking and teeth grinding.

Obstructive Sleep Apnea Diagnosis

OSA is diagnosed by taking into consideration the medical history of patients as well as conducting lab or home-based tests.

Polysomnography

In this test, the activities of the heart, brain and lungs, breathing patterns, leg and arm movements as well as the blood oxygen levels of OSA patients are monitored as they sleep. It may involve an Electroencephalogram (EEG), 2 electro-oculograms (EOGs) and an Electromyogram. At the end of this diagnostic test, the total number of apnea/hypopnea episodes recorded per hour is presented as apnea-hypopnea index or AHI. The results of this test are interpreted in the following manner:

  • AHI less than 5 – Normal sleep apnea
  • AHI between 5 and 15 – Mild sleep apnea
  • AHI between 15 and 30 – Moderate sleep apnea
  • AHI greater than 30 – Severe sleep apnea

Home Oximetry Test

A home Oximetry test is a non-invasive technique of monitoring one’s blood oxygenation which can be easier to acquire than a formal polysomnography. Patients scoring 10 or more in an Epworth Sleepiness Scale (ESS) and/or 15 or more in a Sleep Apnea Clinical Score (SACS) are considered to be affected by OSA. The Oximetry test does not measure respiratory arousals or apneic events and so doesn’t give an AHI value.

Other tests may include:

  • Nasolaryngoscopy
  • Arterial blood gases
  • Thyroid function tests

Obstructive Sleep Apnea Differential Diagnosis

A number of conditions show signs and symptoms similar to that of Obstructive Sleep Apnea (OSA). Hence, while determining the presence of OSA, doctors should differentiate it from such similar disorders in order to determine the best treatment plan. The differential diagnoses of OSA include conditions such as:

  • Asthma
  • Depression
  • Narcolepsy
  • Parkinsonism
  • Drug reactions
  • Simple snoring
  • Hypothyroidism
  • Central Sleep Apnea
  • Dystrophica myotonica
  • Idiopathic hypersomnia
  • Nocturnal panic attacks
  • Chronic insufficient sleep
  • Gastroesophageal reflux disease
  • Periodic limb movement disorder
  • Dyspnea caused by pulmonary edema
  • Chronic obstructive pulmonary disease
  • Non-obstructive alveolar hypoventilation
  • Obstructive sleep apnea-hypopnea syndrome
  • Previous instances of encephalitis or head injury
  • Obesity-hypoventilation syndrome or Pickwickian syndrome

Obstructive Sleep Apnea Treatment

OSA can be treated in a number of ways, depending on the medical history of patients, severity of the condition as well as the specific cause responsible for the obstruction.

Physical intervention

Positive airway pressure is the most prevalently used method of therapeutic intervention in which a breathing machine is employed to pump a controlled mass of air through the mask that is worn over the mouth, nose, or both. The additional pressure holds open or splints the relaxed muscles. There are numerous variants to these:

Continuous positive airway pressure or CPAP

In this method, a computer-controlled airflow generator gives out an airstream at constant pressure, which is prescribed by the doctor based on the results of an overnight test or a titration. Newer CPAP models allow more comfort and compliance for patients. CPAP is by far the most prevalently used treatment method for OSA.

Variable positive airway pressure or VPAP

This variant is also referred to as BiPAP or bilevel. It makes use of an electronic circuit for monitoring a patient’s breathing, and produces 2 different pressures – a higher pressure during inhalation as well as a lower one during exhalation. This is a more expensive option, and is often used for patients having other co-existing respiratory problems or who feel uncomfortable to breathe out against increased pressure.

Automatic positive airway pressure or APAP

APAP machines are connected to a computer and pressure sensors to continuously monitor the breathing performance of patients. These adjust the pressure continuously, thereby increasing it when a patient is trying to breathe but cannot and reducing it when pressure is more than necessary.

Another method of physical intervention is sometimes used for patients of moderate or mild sleep apnea. The mandibular advancement splint (MAS) includes a mouthguard that is similar to the ones that are used as a teeth-protecting device in sports. It helps in holding slightly down and forward the lower jaw compared to its natural position which may allow improving breathing in some apnea patients. Oral appliance therapy is also sometimes used despite its side effects, and continues to be popular due to being user friendly.

Pharmaceuticals

Although currently there are no such effective medication-based treatments for OSA that bears FDA approval, treatment with mirtazapine has shown some promise in some studies. Oral doses of theophylline, a methylxanthine drug has been proven effective to reduce the spells of apnea, but is also known to produce side effects like insomnia and heart palpitations. Drugs such as amphetamines and anti-narcoleptic medications are sometimes prescribed to cure the symptoms of somnolence or daytime sleepiness. Loss of weight can be brought about by medications, which can greatly reduce the frequency and intensity of the apnea episodes.

Neurostimulation

Some researchers are of the opinion that OSA occurs due to some neurological difficulty. Experimens have been carried out to study the effectiveness of using pacemakers and other devices that may encourage neurostimulation. This form of treatment is still under active research.

Surgery

Numerous surgical procedures are used to treat OSA. These include:

  • Tonsillectomy
  • Tracheostomy
  • Adenoidectomy
  • Hyoid suspension
  • Genioglossus advancement
  • Uvulopalatopharyngoplasty (UPPP)
  • Laser-assisted uvulopalatoplasty (LAUP)
  • Maxillomandibular advancement (MMA)
  • Nasal surgery, such as turbinectomy and/or straightening of nasal septum
  • Reduction of tongue base, either by using radiofrequency ablation or laser excision

Compression Stockings

Research has shown that use of compression stockings has been able to reduce number of apnea and hypopnea.

Oropharyngeal Muscle Exercises

Performing oropharyngeal muscle exercises like playing the didgeridoo can improve the symptoms of apnea by exercising the muscles of the throat and removing hypotonicity.

Positional Treatments

People might also benefit from lying or sleeping at 30° elevation of upper body or even higher, like in a recliner. This helps to prevent gravitational collapse of airway. Patients are also recommended to try out lateral positions as a treatment for OSA.

Behavioral Interventions

OSA patients are also recommended to avoid intake of alcohol in the evenings, give up smoking as well as trying to lose weight as these behavioral measures can greatly accentuate the chances of an individual for recovering from this sleep disorder.

Obstructive Sleep Apnea Complications

OSA patients can experience the following health complications:

  • Stroke
  • Asthma
  • Obesity
  • Diabetes
  • Weight gain
  • Clinical depression
  • High blood pressure
  • Ocular (eye) problems
  • Metabolic disturbances
  • Psychological problems
  • Cardiovascular diseases
  • Complications related to surgery and medications

Obstructive Sleep Apnea Prognosis

The prognosis for OSA following a regular treatment on a short term is good. Long-term outcome for the condition is not known due to a lack of sufficient data. Death can sometimes occur from the complications that might occur from this sleep disorder. Generally the outcome of treatment for Obstructive sleep apnea is mostly positive, and sufferers tend to live a healthy, well-rounded life.

References:

http://en.wikipedia.org/wiki/Obstructive_sleep_apnea

http://www.patient.co.uk/doctor/obstructive-sleep-apnoea

http://www.mayoclinic.com/health/obstructive-sleep-apnea/DS00968

http://www.nhlbi.nih.gov/health/health-topics/topics/sleepapnea/

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