Sleep Apnea Information*
Sleep apnea (alternatively sleep apnoea) is a sleep disorder in which breathing is interrupted during sleep. It is a kind of dyssomnia.
Obstructive sleep apnea (OSA)
Most people with sleep apnea have obstructive apnea, in which the person stops
breathing during sleep due to airway blockage. Sufferers usually resume
breathing within a few seconds, but periods of as long as sixty seconds are not
uncommon in serious cases. It is more common amongst people who snore, who are
obese, who consume alcohol, or who have anatomical abnormalities of the jaw or
soft palate. However, atypical cases do occur, and the condition should not be
ruled out unilaterally merely because the patient does not fit the profile.
"OSA" is caused by the relaxation of the muscles in the airway during sleep.
Whilst the vast majority of people successfully maintain a patent (open) upper
airway and breathe normally during sleep, a significant number of individuals
are prone to severe narrowing or occlusion of the pharynx, such that breathing
is impeded or even completely obstructed (Mortimore & Douglas, 1997). As the
brain senses a build-up of carbon dioxide, airway muscles are activated which
open the airway, allowing breathing to resume but interrupting deep sleep.
Recurrent airway obstruction gives rise to the obstructive sleep apnoea (OSA)
syndrome, the most common category of sleep-disordered breathing, with 2% of
female and 4% of male subjects meeting the minimal diagnostic criteria for OSA
of at least 10 apneic events per hour. An "event" is characterised by complete
closure of the upper airway for at least 10 seconds, wherein airflow is
prevented despite continued respiratory efforts (American Academy of Sleep
Medicine Task Force, 1999).
Patent airway vs. occluded airway (Bass, 2003)
These recurrent episodes of airway obstruction are associated with asphyxia,
hypertension, depression, and daytime fatigue, since a transient interruption of
the sleep cycle accompanies the restoration of airway patency. Most sufferers
are not aware of these events, and are informed of the symptoms by their sleep
partner. The apneic episodes are thought to account for the clinical sequelę
(symptoms that arise from a particular condition), which include increased
incidence of chronic hypertension, a 700% rise in road traffic accidents,
excessive daytime somnolence (similar, but unrelated to narcolepsy), social and
family disruption, and cardiac arrhythmias and morbidity (Strollo, Jr. & Rogers,
1996). Obstruction of the upper airway may also be a cause of or may contribute
to sudden infant death syndrome (SIDS) (Mathur & Douglas, 1994).
More Books about Sleep Apnea
Diagnosis
In the past, the only way to diagnose the condition was in hospital, using a
camera and other equipment to monitor sleep. With advances in portable
electronics, patients may now use a small device that is strapped to a fingertip
to measure the oxygen content of the blood, a procedure called pulse oximetry.
This is a non-intrusive procedure because only the color of the finger need to
be monitored. Recordings of blood oxygen saturation during sleep indicate the
severity of the problem. The most accurate diagnostic tool, polysomnography, can
confirm the diagnosis and assist the doctor in identifying the type of sleep
apnea present, as listed below.
Excessive daytime sleepiness with no obvious cause, especially if the patient is
overweight, is a primary indicator of possible sleep apnea. Apnea occurs most
often in persons with a neck size of more than 17 inches. Apnea is more common
among males than females, and tends to worsen with age.
Treatment
Physical intervention
The most widely used current therapeutic intervention is positive airway
pressure whereby a breathing machine pumps a controlled stream of air through a
mask worn over the nose, mouth, or both. The additional pressure splints or
holds open the relaxed muscles, just as air in a balloon inflates it. There are
several variants:
(CPAP), or Continuous Positive Airway Pressure, in which a controlled air
compressor generates an airstream at a constant pressure. This pressure is
prescribed by the patient's physician, based on an overnight test or titration.
(BiPAP), or Bilevel Positive Airway Pressure, uses an electronic circuit to
monitor the patient's breathing, and provides two different pressures, a higher
one during inhalation and a lower pressure during exhalation. This system is
more expensive, and is sometimes used with patients who have a higher than
average CPAP pressure and/or who find breathing out against an increased
pressure to be uncomfortable or disruptive to their sleep.
(APAP), or Auto-titrating Positive Airway Pressure, is the most advanced form of
such treatment. An APAP machine incorporates pressure and our vibration sensors
and a computer which continuously monitors the patient's breathing performance.
It adjusts pressure continuously, increasing it when the user is attempting to
breathe but cannot, and decreasing it when the pressure is higher than
necessary.
While the face mask makes some sufferers hesitant to try treatment, many
patients find that the initial difficulty of adapting to the machine is quickly
surpassed by improved, deeper sleep. In addition, the introduction of masks that
resemble a oversized oxygen cannula have been better tolerated by some users.
The vast majority of patients are surprised to find that they tolerate the mask
fairly easily and sleep well while wearing it. Despite their nature as "air
compressors", modern CPAP machines are extremely quiet.
These treatments are often used with accompanying humidification, as some users
experience a drying effect of the airway and mucous membranes. In the United
States, these machines require a prescription. A sleep study is first done to
determine what kind of treatment is needed, and to determine the proper settings
for the nPAP device.
A second type of physical intervention, a dental device, is sometimes prescribed
for mild or moderate sleep apnea sufferers. The device is a mouthguard similar
to those used in sports to protect the teeth. For apnea patients, it is designed
to hold the lower jaw slightly down and forward relative to the natural, relaxed
position. This position holds the tongue further away from the back of the
airway, and may be enough to relieve apnea or improve breathing for some
patients.
Medical (pharmaceutical) treatment
Few drug-based treatments of obstructive sleep apnea are known despite over two
decades of research and tests.
Oral administration of the methylxanthine theophylline (chemically similar to
caffeine) can reduce the number of episodes of apnea, but can also produce side
effects such as palpitations and insomnia. Theophylline is generally ineffective
in adults with OSA, but is sometimes used to treat Central Sleep Apnea (see
below), and infants and children with apnea.
In 2003 and 2004, some neuroactive drugs, particularly a couple of the
modern-generation antidepressants including mirtazapine, have been reported to
reduce incidences of obstructive sleep apnea. As of 2004, these are not yet
frequently prescribed for OSA sufferers.
When other treatments do not completely treat the OSA, drugs are sometimes
prescribed to treat a patient's daytime sleepiness or somnolence. These range
from stimulants such as amphetamines to modern anti-narcoleptic medicines. The
anti-narcoleptic modafinil is seeing increased use in this role as of 2004.
In some cases, weight loss will reduce the number and severity of apnea
episodes.
Neurostimulation
Many researchers believe that OSA is at root a neurological condition, in which
nerves that control the tongue and soft palate fail to sufficiently stimulate
those muscles, leading to over-relaxation and airway blockage. A few experiments
and trial studies have explored the use of pacemakers and similar devices,
programmed to detect breathing effort and deliver gentle electrical stimulation
to the muscles of the tongue.
This is not a common mode of treatment for OSA patients as of 2004, but it is an
active field of research.
Surgical intervention
A number of different surgeries are often tried to improve the size or tone of
the patient's airway. For decades, tracheostomy was the only effective treatment
for sleep apnea. It is used today only in very rare, intractable cases that have
withstood other attempts at treatment. Modern treatments try one or more of
several options, tailored to the patient's needs.
Nasal surgery, including turbinectomy (removal or reduction of a nasal
turbinate), or straightening of the nasal septum, in patients with nasal
obstruction or congestion which reduces airway pressure and complicates OSA.
Tonsilectomy and/or adenoidectomy in an attempt to increase the size of the
airway.
Removal or reduction of parts of the soft palate and some or all of the uvula,
such as uvulopalatopharyngoplasty (UPPP) or laser-assisted palatopharynsoplasty
(LAUP). Modern variants of this procedure sometimes use radiofrequency waves to
heat and remove tissue.
Reduction of the tongue base, either with laser excision or radiofrequency
ablation.
Genioglossus Advancement, in which a small portion of the lower jaw which
attaches to the tongue is moved forward, to pull the tongue away from the back
of the airway.
Hyoid Suspension, in which the hyoid bone in the neck, another attachment point
for tongue muscles, is pulled forward in front of the larynx.
Maxillomandibular advancement (MMA). A more invasive surgery usually only tried
in difficult cases where other surgeries have not relieved the patient's OSA, or
where an abnormal facial structure is suspected as a root cause. In MMA, the
patient's upper and lower jaw are detached from the skull, moved forward, and
reattached with pins and/or plates.
Central apnea
Another, rarer form is central sleep apnea, where a problem in the central
nervous system (particularly the areas of the brainstem responsible for
respiratory drive) interrupts breathing. Overdoses of opiates, such as heroin
and morphine, kill by inducing a severe central apnea; these drugs are thus
called "respiratory depressants". Central sleep apnea is more common at higher
elevations.
A combination of Obstructive and Central Apnea is called Mixed Apnea.
Training apnea
(Training Apnea; informal suggestion for identification)
Noted amongst a minority of active free-divers, this is the case of subjects
performing apnea while sleeping, generally coincident with a related dream. Some
cases have been determined to last until the point at which diaphramatic
contractions occur, and are estimated to be greater than one minute in length.
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