| Sleep apnea Classification and external resources |
|
| ICD-10 | G47.3 |
|---|---|
| ICD-9 | 780.57 |
| eMedicine | ped/2114 |
| MeSH | D012891 |
Sleep apnea is a sleep disorder characterized by pauses in breathing during sleep. The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The International Statistical Classification of Diseases and Related Health Problems 10th Revision ( ICD -10) is a coding of diseases and signs symptoms abnormal findings G00-G99 - Diseases of the Nervous system (G00-G09 Inflammatory diseases of the Central nervous system ( Bacterial meningitis The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Breathing takes Oxygen in and Carbon dioxide out of the body Aerobic Organisms require oxygen to create energy via respiration, in Sleep is a Natural state of bodily rest observed throughout the animal kingdom Each episode, called apneas (Greek: άπνοια (ápnoia), from α- (a-), privative, πνέειν (pnéein), to breathe), lasts long enough so that one or more breaths are missed, and occurs repeatedly throughout sleep. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly A privative, named from Latin privare, "to deprive" is a particle that negates or inverts the value of the stem The standard definition of any apneic event includes a minimum 10 second interval between breaths, with either a neurological arousal (a 3-second or greater shift in EEG frequency, measured at C3, C4, O1, or O2), a blood oxygen desaturation of 3-4% or greater, or both arousal and desaturation. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Sleep apnea is diagnosed with an overnight sleep test called a polysomnogram. Polysomnogram (PSG is a multi-channel ("poly" recording ("gram" during sleep ("somno" resulting from a sleep test Polysomnography.
Clinically significant levels of sleep apnea are defined as five or more episodes per hour of any type of apnea (from the polysomnogram). There are three distinct forms of sleep apnea: central, obstructive, and complex (complex is a combination of central and obstructive) making up 0. 4%, 84% and 15% of cases respectively. [1] Breathing is interrupted by the lack of effort in central sleep apnea; in obstructive sleep apnea, breathing is interrupted by a physical block to airflow despite effort. In mixed sleep apnea, there is a transition from central to obstructive features during the events themselves.
Regardless of type, the 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). A sequela, (sɨˈkwiːlə plural sequelæ) is a Pathological condition resulting from a Disease, Injury, or other trauma. Symptoms may be present for years, 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.
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The first reports of what is now called obstructive sleep apnea, in the medical literature date only from 1965, when it was independently described by French and German investigator Tyeneshia Dow. However, the clinical picture of this condition has long been recognized as a character trait, without an understanding of the disease process. The term “Pickwickian syndrome” that is sometimes used for the syndrome, was coined by the famous early 20th Century physician, William Osler, who must have been a reader of Charles Dickens. The obesity hypoventilation syndrome, also known as Pickwickian syndrome, is the combination of Obesity ( Body mass index above 30 kg/m2 Sir William Osler 1st Baronet ( July 12, 1849 &ndash December 29, 1919 Age 70 was a Canadian Physician. The description of Joe, "the fat boy" in Dickens's novel, The Pickwick Papers, is an accurate clinical picture of adult obstructive sleep apnea syndrome. The Posthumous Papers of the Pickwick Club, better known as The Pickwick Papers, is the first novel by Charles Dickens.
The early reports of obstructive sleep apnea in the medical literature described individuals who were very severely affected, often presenting with severe hypoxemia, hypercapnia and congestive heart failure. Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply Tracheostomy was the recommended treatment and, though it could be life-saving, post-operative complications in the stoma were frequent in these very obese and short-necked individuals. Tracheotomy and tracheostomy are Surgical procedures on the neck to open a direct airway through an incision in the trachea (the windpipe In Medicine, a stoma (Greek - pl stomata is an opening either natural or surgically created (artificial which connects a portion of the body cavity to the outside
The management of obstructive sleep apnea was revolutionized with the introduction of continuous positive airway pressure (CPAP), first described in 1981 by Colin Sullivan and associates in Sydney, Australia. Sydney (ˈsɪdniː is the most populous city in Australia, with a Metropolitan area population of approximately 4 For a topic outline on this subject see List of basic Australia topics. The first models were bulky and noisy but the design was rapidly improved and by the late 1980s CPAP was widely adopted. The availability of an effective treatment stimulated an aggressive search for affected individuals and led to the establishment of hundreds of specialized clinics dedicated to the diagnosis and treatment of sleep disorders. A sleep disorder (somnipathy is a medical disorder of the Sleep patterns of a person or animal Though many types of sleep problems are recognized, the vast majority of patients attending these centers have sleep disordered breathing.
Obstructive sleep apnea (OSA) is the most common category of sleep-disordered breathing. Obstructive sleep apnea (OSA is a common Sleep apnea caused by obstruction of the airway Since the muscle tone of the body ordinarily relaxes during sleep, and since, at the level of the throat, the human airway is composed of collapsible walls of soft tissue, it is easy to understand why breathing can be obstructed 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 sleep deprivation and other complications. Upper respiratory tract infections, ( URTI or URI) are the illnesses caused by an acute Infection which involves the upper Respiratory tract: Sleep deprivation is a general lack of the necessary amount of Sleep. The most serious complication is a severe form of congestive heart failure called cor pulmonale. Cor pulmonale is a change in structure and function of the Right ventricle of the heart as a result of a respiratory disorder
Individuals with low muscle tone and soft tissue around the airway (e. g. , due to 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 typical sleep apnea sufferers than women and children, although it is not uncommon in these.
Common symptoms include loud snoring, restless sleep, and sleepiness during the daytime. Snoring is the vibration of respiratory structures and the resulting sound due to obstructed air movement during Breathing while Sleeping In some cases the sound Diagnostic tests include home oximetry or polysomnography in a sleep clinic. Pulse oximetry is a non-invasive method allowing the monitoring of the Oxygenation of a patient's Hemoglobin.
Some treatments involve lifestyle changes, such as avoiding alcohol or muscle relaxants, losing weight, and quitting smoking. Many people benefit from sleeping at a 30 degree elevation of the upper body[2] or higher, as if in a recliner. A recliner is an Armchair that reclines when the occupant lowers the chair's back and raises its front Doing so helps prevent the gravitational collapse of the airway. Lateral positions (sleeping on a side), as opposed to supine positions (sleeping on the back), are also recommended as a treatment for sleep apnea,[3][4][5] largely because the gravitaional component is smaller than in the lateral position. The supine position is a position of the body; lying down with the Face up as opposed to the Prone position, which is face down Some people benefit from various kinds of oral appliances to keep the airway open during sleep. A mandibular splint or mandibular advancement splint is a device worn in the Mouth that is used to treat Obstructive sleep apnea and Snoring "Breathing machines" like the continuous positive airway pressure (CPAP) may help. There are also surgical procedures to remove and tighten tissue and widen the airway.
This section summarizes the clinical picture and consequences of obstructive sleep apnea syndrome.
As already mentioned, snoring is almost a uniform finding in an individual with this syndrome, but many people snore without having apnea. Snoring is the turbulent sound of air moving through the back of the mouth, nose and throat. The loudness of the snoring is not indicative of the severity of obstruction, however. If the upper airways are tremendously obstructed, there may not be enough air movement to make much sound. Even the loudest snoring does not mean that an individual has sleep apnea syndrome. The sign that is most suggestive of sleep apneas occurs if snoring stops. If it does, along with breath, while the persons' chest and body tries to breathe - that is literally a description of an event in obstructive sleep apnea syndrome. When breathing starts again, there is typically a deep gasp, and then the resumption of snoring.
Sometimes, elevated arterial pressure (commonly called high blood pressure) is a sequela of obstructive sleep apnea syndrome. Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the Blood pressure is chronically elevated [6] When high blood pressure is caused by OSA, it is distinctive in that, unlike most cases of high blood pressure (so-called essential hypertension), the readings do not drop significantly when the individual is sleeping. Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the Blood pressure is chronically elevated [7] Stroke is associated with obstructive sleep apnea. A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain [8] Sleep apnea sufferers also have a 30% higher risk of heart attack or premature death than those unaffected. [9]
In pure central sleep apnea or Cheyne-Stokes respiration, the brain's respiratory control centers are imbalanced during sleep. Cheyne-Stokes respiration (also known as periodic breathing) is an abnormal pattern of Breathing characterized by oscillation of ventilation between Apnea Blood levels of carbon dioxide, and the neurological feedback mechanism that monitors it does 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.
While sleeping, a normal individual is "at rest", as far as cardiovascular workload is concerned. Breathing is regular in a healthy person during sleep, and oxygen levels and carbon dioxide levels in the bloodstream stay fairly constant. The respiratory drive is so strong that even conscious efforts to hold one's breath do not overcome it. Any sudden drop in oxygen or excess of carbon dioxide (even if tiny) strongly stimulates the brain's respiratory centers to breathe. In central sleep apnea, the basic neurological controls for breathing rate malfunctions and fails 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 (hypoxia) and the concentration of carbon dioxide will build to a higher than normal level (hypercapnia). Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is In turn, these conditions of hypoxia and hypercapnia will trigger additional effects on the body. Brain cells need constant oxygen to live; and, if the level of blood oxygen goes low enough for long enough, the consequences of brain damage and even death will occur. Fortunately, central sleep apnea is more often a chronic condition that causes much milder effects than sudden death. The exact effects of the condition will depend on how severe the apnea is, and the individual characteristics of the person having the apnea. Several examples are discussed below, and more about the nature of the condition is presented in the section on Clinical Details.
In any person, hypoxia and hypercapnia have certain common effects on the body. The heart rate will increase, unless there are such severe co-existing problems with the heart muscle itself or the autonomic nervous system that makes this compensatory increase impossible. The more translucent areas of the body will show a bluish or dusky cast from cyanosis, which is the change in hue that occurs due to lack of oxygen in the blood ("turning blue"). Cyanosis is a blue coloration of the Skin and mucous membranes due to the presence of deoxygenated Hemoglobin in Blood vessels near the skin surface Overdoses of drugs that are respiratory depressants (such as heroin, and other opiates) kill by damping the activity of the brain's respiratory control centers. In central sleep apnea, the effects of sleep alone can remove the brains' mandate for the body to breathe. Even in severe cases of central sleep apnea, the effects almost always result in pauses that make breathing irregular, rather than cause the total cessation of breathing.
| AHI | Rating |
|---|---|
| <5 | Normal |
| 5-15 | Mild |
| 15-30 | Moderate |
| >30 | Severe |
Polysomnography of sleep apnea shows pauses in breathing that are followed by drops in blood oxygen and increases in blood carbon dioxide. See also Polysomnogram Polysomnography or PSG is a multi-parametric test used in the study of Sleep; the test result is called a In adults, a pause must last 10 seconds to be scored as an apnea. However in young children, who normally breathe at a much faster rate than adults, the pause may be many seconds shorter and still be considered apnea. The cessation of airflow in central sleep apnea has an association with no physical attempts to breathe. On polysomnograms, there is an absence of rib cage and abdominal movements while airflow ceases at the nose and lips. Obstructive sleep apnea show pauses in breathing for at least 10 seconds causing a decrease in blood oxygen and associates with physical attempts to breathe.
Hypopneas in adults are defined as a 50% reduction in air flow for more than 10 s, followed by a 4% desaturation, and/or arousal. The Apnea- Hypopnea Index (AHI) is expressed as the number of apneas and hypopneas per hour of sleep.
Any individual, no matter how healthy, who is given enough of a central respiratory depressant drug will develop apnea on a central basis. Generally, drugs that are central respiratory depressants also have sedative effects, and so the individual taking a toxic dose of such a drug is likely to be asleep, or at least in an altered state of consciousness, when breathing becomes irregular. In Medicine, hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate ( hypo means "below" to perform needed Sedation is a Medical procedure involving the administration of Sedative drugs generally to facilitate a medical procedure with Local anaesthesia. Alcohol is such a central respiratory depressant in large doses, so are opiates, barbiturates, benzodiazepines, and many other tranquilizers. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon An opioid is a chemical Substance that has a Morphine -like action in the body Barbiturates are drugs that act as central nervous system Depressants and by virtue of this they produce a wide spectrum of effects from mild Sedation The benzodiazepines (pronounced, often abbreviated to "benzos") are a class of Psychoactive drugs with varying Hypnotic A sedative, or more specifically a sedative-hypnotic, is a substance that depresses the Central nervous system (CNS resulting in calmness relaxation sleepiness Some individuals have abnormalities that predispose them to central sleep apnea. The treatment for the condition depends on its specific cause.
Similarly, in any person who has some form of sleep apnea (including obstructive sleep apnea), breathing irregularities during sleep can be dangerously aggravated by taking one of these drugs. Quantities that are normally considered safe may cause the person with chronic sleep apnea to stop breathing altogether. Should these individuals have general anesthesia, for example, they require prolonged monitoring after initial recovery, as compared to a person with no history of sleep apnea, because apnea is likely to occur with even low levels of the drugs in their system.
Premature infants with immature brains and reflex systems are at high risk for central sleep apnea syndrome, even if these babies are otherwise healthy. Premature birth (also known as preterm birth) is the Birth of a Baby before the standard period of Pregnancy is completed Fortunately, those premature babies who have the syndrome will generally outgrow it as they mature, providing they receive careful enough monitoring and supportive care during infancy to survive. Because of the propensity toward apnea, medications that can cause respiratory drive depression are either not given to premature infants, or given under careful monitoring, with equipment for resuscitation immediately available. Such precautions are routinely taken for premature infants after general anesthesia. Caffeine has been found to help reduce apnea in preterm infants and to aid in care after general anesthesia. Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic In modern medical practice general anaesthesia ( AmE: anesthesia) is a state of total unconsciousness resulting from General anaesthetic drugs [10]
Sudden infant death syndrome is sometimes theorized to be attributable to sleep apnea. Sudden infant death syndrome (SIDS is a syndrome marked by the symptoms of sudden and unexplained death of an apparently healthy Infant aged one month to one year
Congenital Central Hypoventilation Syndrome: This rare, inborn condition involves a specific gene, PHOX2B. Ondine's Curse, also called congenital central hypoventilation syndrome ( CCHS) or primary alveolar hypoventilation, is a respiratory disorder that PHOX2B is a human Gene located on chromosome 4. It codes for a Homeodomain transcription factor This homeobox gene guides maturation of the autonomic nervous system, and loss-of-function mutations lead to the failure of the brain to effectively control breathing during sleep in patients with the syndrome. There may be a pattern of recognizable facial features among individuals affected with this syndrome. [11]
Once almost uniformly fatal, congenital hypoventilation ("abnormally low ventilation") syndrome is now treatable. The children who have it must have tracheotomies and access to mechanical ventilation on respirators while sleeping, but most do not need to use a respirator while awake. Tracheotomy and tracheostomy are Surgical procedures on the neck to open a direct airway through an incision in the trachea (the windpipe A respirator is a device designed to protect the wearer from inhaling harmful Dusts fumes vapors and/or Gases Respirators come in a wide range of types and sizes The use of a diaphragmatic pacemaker may offer an alternative for some patients. A diaphragmatic pacemaker, in Medicine, is a surgically-implanted device used to help patients breathe following complications from spinal cord injuries When pacemakers have enabled some children to sleep without the use of a mechanical respirator, reported cases still required the tracheotomy to remain in place, because the vocal cords did not move apart with inhalation. This form of central sleep apnea has been called Ondine's curse. Ondine's Curse, also called congenital central hypoventilation syndrome ( CCHS) or primary alveolar hypoventilation, is a respiratory disorder that Now that some children with the syndrome have grown up, there is particular need for their avoidance of adolescent behaviors, such as alcohol use, which can easily be lethal. [12]
Adults suffering from congestive heart failure are at risk for a form of central sleep apnea called Cheyne-Stokes respiration. Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply Cheyne-Stokes respiration (also known as periodic breathing) is an abnormal pattern of Breathing characterized by oscillation of ventilation between Apnea This is periodic breathing with recurrent episodes of apnea alternating with episodes of rapid breathing. In those who have it, Cheyne-Stokes respirations occur while both awake and asleep. There is good evidence that replacement of the failed heart (heart transplant) cures central apnea in these patients. Heart transplantation or cardiac transplantation, is a surgical transplant procedure performed on patients with end-stage Heart failure or severe Coronary The use of some medications that are respiratory stimulants decrease the severity of apnea in some patients. A respiratory stimulant is a drug which acts to increase the action of the Respiratory system.
1) Macey PM. Macey KE. Woo MA. Keens TG. Harper RM. Aberrant neural responses to cold pressor challenges in congenital central hypoventilation syndrome. [see comment]. [Journal Article] Pediatric Research. 57(4):500-9, 2005 Apr.
2) Bradley TD. Floras JS. Sleep apnea and heart failure: Part II: central sleep apnea. [Review] [55 refs] [Journal Article. Review] Circulation. 107(13):1822-6, 2003 April 8.
3) Mansfield DR. Solin P. Roebuck T. Bergin P. Kaye DM. Naughton MT. The effect of successful heart transplant treatment of heart failure on central sleep apnea. [see comment]. [Journal Article] Chest. 124(5):1675-81, 2003 Nov.
4)Javaheri S. Acetazolamide improves central sleep apnea in heart failure: a double-blind, prospective study. [Clinical Trial. Journal Article. Randomized Controlled Trial] American Journal of Respiratory & Critical Care Medicine. 173(2):234-7, 2006 Jan 15.
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. Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply 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. The presence of central sleep apnea without an obstructive component is a common result of chronic opiate use (or abuse), due to the characteristic respiratory depression caused by large doses of narcotics. For other uses see Opiate (disambiguation, or for the class of drugs see Opioid.
Complex sleep apnea has recently been described by researchers as a novel presentation of sleep apnea. Patients with complex sleep apnea exhibit OSA, but upon application of positive airway pressure, the patient exhibits persistent central sleep apnea. This central apnea is most commonly noted while on CPAP therapy, after the obstructive component has been eliminated. This has long been seen in sleep laboratories, and has historically been managed either by CPAP or BiLevel therapy. Adaptive servo-ventilation modes of therapy have been introduced to attempt to manage this complex sleep apnea. Studies have demonstrated marginally superior performance of the adaptive servo ventilators in treating Cheyne-Stokes breathing, however, no longitudinal studies have yet been published, nor have any results been generated which suggest any differential outcomes versus standard CPAP therapy. At the AARC 2006 in Las Vegas, NV, researchers reported successful treatment of hundreds of patients on Adapt SV therapy, however these results have not been reported in peer reviewed publications as of July, 2007.
An important finding by Dernaika, et al. , (Chest 2007, 132) suggests that transient central apnea produced during CPAP titration (the so called "complex sleep apnea") is ". . . transient and self-limited. " The central apneas may in fact be secondary to sleep fragmentation during the titration process. As of July 2007, there has been no alternate convincing evidence produced that these central sleep apnea events associated with CPAP therapy for obstructive sleep apnea are of any significant pathophysiologic import.
The most common treatment and arguably the most consistently effective treatment for sleep apnea is the use of a continous positive airway pressure (CPAP) device[13] , which 'splints' the patient's airway open during sleep by means of a flow of pressurized air into the throat.
In addition to CPAP, a dentist specializing in sleep disorders can prescribe Oral Appliance Therapy (OAT). The oral appliance is a custom made mouthpiece that shifts the lower jaw forward which opens up the airway. 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.
CPAP and OAT are effective only for obstructive sleep apnea, not for central or mixed cases.
For unknown reasons, possibly due to changes in pulmonary oxygen stores,[14] sleeping in the lateral position has been found to be helpful for central sleep apnea (CSA).
Medications like Acetazolamide[15][16] lower blood pH and encourage respiration. Acetazolamide, sold under the trade name Diamox, is a Carbonic anhydrase inhibitor that is used to treat Glaucoma, Epileptic seizures Benign pH is the measure of the acidity or alkalinity of a Solution. Low doses of oxygen are also used as a treatment for hypoxia but are discouraged due to side effects. [17][18][19]
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. The didgeridoo (also known as a didjeridu or didge) is a wind instrument of the Indigenous Australians of northern Australia. This appears to work by strengthening muscles in the upper airway, thus reducing their tendency to collapse during sleep. . [20]
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. In an individual with either central, obstructive or mixed sleep apnea, these low doses may be enough to cause life-threatening irregularities in breathing.
Use of analgesics and sedatives in these patients postoperatively should therefore be minimized or avoided.
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.
Individuals with sleep apnea generally require more intensive monitoring after surgery for these reasons.