Apnea (literally, "without breath") is the term used when someone stops breathing for very short periods of time, usually 10 to 20 seconds. It's termed "obstructive" when respiratory efforts continue, such as movements of the chest. It's termed "central" when all respiratory effort stops. There is also a mixed version. In children, sleep apnea is almost always obstructive. During the apneic episode, the child will have decreased oxygenation of the blood.
Symptoms of Obstructive Sleep Apnea (OSA) are: snoring, restless/disturbed sleep, frequent partial or total wakenings and daytime mouth breathing. Some children with OSA have odd sleep positions, often with their neck bent backwards, or even in a sitting position. Some children with OSA sweat profusely during sleep. In adults, there is an association of obesity, but that's not a common association in children. Some children will have daytime grumpiness or sleepiness, but it's not common. Some children may have noisy swallowing as well.
Children with Down syndrome (DS) are certainly at risk for OSA. In 1991, one study showed 45% had OSA. This can be caused by several different factors present in DS: the flattened midface, narrowed nasopharyngeal area, low tone of the muscles of the upper airway and enlarged adenoids and/or tonsils.
Why is this important? Well, first, there's the obvious problem of the child not getting enough quality sleep and the behavioral effects that brings. Second, I've mentioned above that during sleep apnea, the oxygenation of the blood decreases. It has been shown that in children with DS and heart disease this low oxygenation causes an increase in the blood pressure in the lungs as the body tries to get more oxygen. This "pulmonary hypertension" can cause the right side of the heart to become enlarged and other cardiac complications can follow. The incidence of death due to OSA is unknown.
If you're unsure if your child has OSA, the way to test is through a sleep study, also called polysomnography. This test is performed overnight in a hospital (though some doctors will do "nap somnography") and consists of continuous monitoring of the oxygen in the blood, as well as monitoring chest wall movements (to assess respiratory efforts) and the flow of air through the nose. Some doctors also measure carbon dioxide in the blood or exhaled air. This is usually performed by otolaryngologists or neonatologists.
The treatment of OSA is usually removal of adenoids and/or tonsils. Various studies have been done on children with DS, and this appears to relieve OSA in most cases. However, it has been estimated that 30 to 40% of children with DS and OSA develop recurrent or persistant OSA even after removal of the tonsils and adenoids. There are several different reasons for this, including a large tongue, blockage of the airway by movement of the tongue during sleep, low muscle tone of the area of the airway just below the throat, and regrowth of the adenoids. When there is some concern regarding the effectiveness of the initial surgery, then post-surgical polysomnography is needed to document the OSA. Some centers are now using a type of MRI that takes sequential pictures of the airway while the child or adult is asleep to evaluate possible causes for persistant or recurrent OSA, and basing further surgery on those results;
In adults and children in whom surgical treatment has failed or was not indicated, one therapy is "continuous positive airway pressure," or CPAP. This is administered by a nasal mask or tube during sleep. The tube/mask administers air with an amount of pressure designed to keep the airway open.
Obstructive sleep apnea-hypopnea (OSAH) is characterized by recurrent episodes of upper airway collapse and obstruction during sleep. These episodes of obstruction are associated with recurrent oxyhemoglobin desaturation and arousals from sleep. Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a term frequently used when this is associated with excessive daytime sleepiness. Despite being a common disease, OSAHS is unrecognized by most primary care physicians in the United States (an estimated 80% of OSAHS cases in the United States are not diagnosed).
Pathophysiology: The upper airway is a compliant tube and is therefore subject to collapse. The majority of patients with OSAHS demonstrate upper airway obstruction, either at the level of the soft palate (nasopharynx) or at the level of the tongue (oropharynx). Recent research indicates that both anatomic and neuromuscular factors are important. Anatomic factors, such as enlarged tonsils, macroglossia, or abnormal positioning of the maxilla and mandible, decrease the cross-sectional area of the upper airway and/or increase the pressure surrounding the airway, both of which predispose the airway to collapse.
Upper airway neuromuscular activity, including reflex activity, decreases with sleep, and this decrease may be more pronounced in patients with OSAHS. Reduced ventilatory motor output to upper airway muscles is believed to be the critical initiating event leading to upper airway obstruction; this effect is most pronounced in patients with an upper airway predisposed to collapse for anatomic reasons.
Central breathing instability has been well established to contribute to the development of central sleep apnea, particularly in patients with severe congestive heart failure .
Frequency:
In the US: OSAHS is a common disease in the United States. Prevalence of OSAHS, as indicated by data from a Wisconsin cohort study (adults aged 30-60 years) is 9-24% for men and 4-9% for women. Estimated prevalence of OSAHS is 2% in women and 4% in men. Similar data have been found in a epidemiologic study from Pennsylvania (Bixler, 1998; Bixler, 2001)
Internationally: The prevalence of OSAHS in non-US populations has only been studied in men and has been found to be as low as 0.3% in England. It is as high as 20-25% in Israel and Australia
; prevalence of OSAHS in Australian men was estimated to be 3%.
Mortality/Morbidity: Retrospective data indicate that mortality rate is higher in patients with an apnea-hypopnea index [AHI] greater than 20 per hour than in those with an AHI less than 20 per hour
Race: The prevalence of sleep apnea in young black people (<25 y) appears to be greater than in white people. Recent evidence indicates that the prevalence in older age groups is similar between black people and white people but the severity of OSAHS is worse in black people (ie, African Americans have higher AHIs).
Sex: The male-to-female ratio in community-based studies is 2-3:1.
Three large epidemiologic studies have demonstrated that the prevalence of OSAHS in women appears to increase after menopause (Bixler, 2001; Shahar, 2003; Young, 2003). In these studies, women taking hormone replacement therapy had a prevalence similar to that of premenopausal women.
Premenopausal women with OSAHS tend to be more obese than men for the same severity of disease. Thin women with symptoms of OSAHS appear to have an increased frequency of craniofacial abnormalities.
Evidence exists that women underreport the symptoms of loud snoring and witnessed apneas, leading to underreferral to sleep centers. This may explain the marked male predominance (approximately 8:1) in sleep-center–based studies.
Age: The prevalence of OSAHS increases with age, with an estimated prevalence as high as 65% in a community sample of people older than 65 years. However, the significance of the incidental finding of OSAHS in elderly persons has been debated
History: Symptoms generally begin insidiously and are often present for years before the patient is referred for evaluation.
Nocturnal symptoms
Snoring, usually loud, habitual, and bothersome to others
Witnessed apneas that often interrupt the snoring and end with a snort
Gasping and choking sensations that arouse the patient from sleep
Restless sleep, with patients often complaining of frequent arousal and tossing/turning during the night
Daytime symptoms
Waking up without feeling refreshed
Morning headache, dry or sore throat
EDS that usually begins during quiet activities (eg, reading, watching television): As the severity worsens, patients begin to feel sleepy during activities that generally require alertness (eg, school, work, driving).
EDS is most frequently assessed by the sleep physician using the Epworth Sleepiness Scale (ESS). This is a questionnaire that asks the patient how frequently they are likely to doze off in 8 frequently encountered situations.
An ESS score greater than 10 is generally considered sleepy. However, a recent study showed that an ESS score of 12 is associated with a greater propensity to fall asleep on the multiple sleep latency test (MSLT), suggesting that 12 would be a better cutoff (Punjabi, 2003).
The ESS does not correlate well with the primary objective measurement of sleepiness, the MSLT (see below) (Chervin, 1999; Benbadis, 1999), in that a higher ESS score does not mean shorter latencies on the MSLT. However, a higher ESS score does mean a greater likelihood of falling asleep on the MSLT (Punjabi, 2003).
ESS is useful in evaluating response to treatment. The ESS score should decrease with effective treatment.
Daytime fatigue/tiredness: Most patients who do not complain of excessive daytime sleepiness will complain of being fatigued, having a lack of energy, or being tired during the day.
Personality changes and problems with memory or concentration
Physical: The physical examination is frequently normal in OSAHS, other than the presence of obesity (defined as a body mass index greater than 28 kg/m2) and hypertension. The upper airway should be evaluated in all patients, particularly in nonobese adults with symptoms consistent with OSAHS. Features associated with the presence of OSAHS are as follows:
Narrowing of the lateral airway walls, which an independent predictor of the presence of OSAHS in men but not women
Enlarged (ie, "kissing") tonsils
Retrognathia or micrognathia
Overjet
Soft palate edema/erythema
High, arched hard palate
Causes:
Risk factors include the following:
Obesity
Age
Male sex
Craniofacial skeletal abnormalities, particularly in nonobese adults and children (see Physical)
Adenotonsillar hypertrophy, particularly in children and young adults
Alcohol use
Lab Studies:
Thyroid-stimulating hormone (TSH) should be obtained in any patient with suspected OSAHS who has other signs and/or symptoms of hypothyroidism.
Arterial blood gases should be measured in patients presenting with cor pulmonale to rule out daytime hypoxemia or hypercapnia.
Other Tests:
Polysomnography (overnight sleep study) is required to diagnose OSAHS. It is preferably performed in a sleep center, where specially trained technicians perform the tests. During polysomnography, multiple body functions are monitored.
Sleep stages (monitored with an EEG, electrooculogram [EOG], and chin electromyogram [EMG])
Heart rhythm (single lead ECG)
Leg movements (anterior tibialis EMG)
Breathing (airflow at nose/mouth, effort, and oxygen saturation)
The breathing pattern is analyzed for the presence of apneas and hypopneas. Standard definitions have been proposed but are still not consistently used by sleep centers (American Academy of Sleep Medicine Task Force, 1999).
Obstructive apnea - Cessation of airflow with persistent respiratory effort (see Image 1)
Central apnea - Cessation of airflow with no respiratory effort (see Image 2)
Mixed apnea - An apnea that begins as a central apnea and ends as an obstructive apnea (see Image 3)
Hypopnea - Definition highly variable between sleep centers; however, according to a recent consensus statement, hypopnea is a 30% or greater reduction in flow associated with a 4% drop in oxygen saturation; many centers also score a hypopnea if a decrease in flow is associated with an arousal (see Images 4-5)
Respiratory event–related arousal - A recently defined event that recognizes cases in which a series of breaths with increasingly negative pleural pressure terminates with an arousal; these cases have no clear decrease in flow that would cause the event to be labeled as an apnea or hypopnea; because this event cannot be scored if the esophageal pressure is not monitored, it is not used by many sleep centers
AHI is derived from the total number of apneas and hypopneas divided by total sleep time
A normal cutoff for AHI has never been defined in an epidemiological study of healthy subjects. Most sleep centers use a cutoff between 5 and 10/hour.
Severity of OSAHS is defined arbitrarily and differs widely between centers. Recent recommendations for cutoffs are as follows:
Mild: AHI = 5-15 per hour
Moderate: AHI = 15-30 per hour
Severe: AHI >30 per hour
Polysomnography is often followed by MSLT. The MSLT is considered an objective measure of EDS.
MSLT consists of 4-5 naps of 20 minutes duration every 2 hours during the day. The latency to sleep onset for each nap is averaged to determine the daytime sleep latency.
Normal daytime sleep latency is greater than 10-15 minutes. OSAHS is generally associated with latencies less than 10 minutes.
The routine use of the MSLT in the evaluation of OSAHS is decreasing as sleep physicians generally treat OSAHS on the basis of the subjective symptoms reported by the patient.
The MSLT is helpful to rule out narcolepsy in patients in whom narcolepsy is a consideration. As opposed to people without narcolepsy, patients with narcolepsy have rapid eye movement (REM) sleep on at least 2 of the 4-5 naps during the day.
Pulmonary function tests should be obtained if any evidence of cor pulmonale is noted or if the nocturnal symptoms are suggestive of nocturnal asthma (patients wake up short of breath, which does not resolve immediately or is associated with wheezing).
Lab Studies:
Thyroid-stimulating hormone (TSH) should be obtained in any patient with suspected OSAHS who has other signs and/or symptoms of hypothyroidism.
Arterial blood gases should be measured in patients presenting with cor pulmonale to rule out daytime hypoxemia or hypercapnia.
Other Tests:
Polysomnography (overnight sleep study) is required to diagnose OSAHS. It is preferably performed in a sleep center, where specially trained technicians perform the tests. During polysomnography, multiple body functions are monitored.
Sleep stages (monitored with an EEG, electrooculogram [EOG], and chin electromyogram [EMG])
Heart rhythm (single lead ECG)
Leg movements (anterior tibialis EMG)
Breathing (airflow at nose/mouth, effort, and oxygen saturation)
The breathing pattern is analyzed for the presence of apneas and hypopneas. Standard definitions have been proposed but are still not consistently used by sleep centers (American Academy of Sleep Medicine Task Force, 1999).
Obstructive apnea - Cessation of airflow with persistent respiratory effort (see Image 1)
Central apnea - Cessation of airflow with no respiratory effort (see Image 2)
Mixed apnea - An apnea that begins as a central apnea and ends as an obstructive apnea (see Image 3)
Hypopnea - Definition highly variable between sleep centers; however, according to a recent consensus statement, hypopnea is a 30% or greater reduction in flow associated with a 4% drop in oxygen saturation; many centers also score a hypopnea if a decrease in flow is associated with an arousal (see Images 4-5)
Respiratory event–related arousal - A recently defined event that recognizes cases in which a series of breaths with increasingly negative pleural pressure terminates with an arousal; these cases have no clear decrease in flow that would cause the event to be labeled as an apnea or hypopnea; because this event cannot be scored if the esophageal pressure is not monitored, it is not used by many sleep centers
AHI is derived from the total number of apneas and hypopneas divided by total sleep time
A normal cutoff for AHI has never been defined in an epidemiological study of healthy subjects. Most sleep centers use a cutoff between 5 and 10/hour.
Severity of OSAHS is defined arbitrarily and differs widely between centers. Recent recommendations for cutoffs are as follows:
Mild: AHI = 5-15 per hour
Moderate: AHI = 15-30 per hour
Severe: AHI >30 per hour
Polysomnography is often followed by MSLT. The MSLT is considered an objective measure of EDS.
MSLT consists of 4-5 naps of 20 minutes duration every 2 hours during the day. The latency to sleep onset for each nap is averaged to determine the daytime sleep latency.
Normal daytime sleep latency is greater than 10-15 minutes. OSAHS is generally associated with latencies less than 10 minutes.
The routine use of the MSLT in the evaluation of OSAHS is decreasing as sleep physicians generally treat OSAHS on the basis of the subjective symptoms reported by the patient.
The MSLT is helpful to rule out narcolepsy in patients in whom narcolepsy is a consideration. As opposed to people without narcolepsy, patients with narcolepsy have rapid eye movement (REM) sleep on at least 2 of the 4-5 naps during the day.
Pulmonary function tests should be obtained if any evidence of cor pulmonale is noted or if the nocturnal symptoms are suggestive of nocturnal asthma (patients wake up short of breath, which does not resolve immediately or is associated with wheezing).
TREATMENT
Medical Care: The treatment of OSAHS partly depends upon the severity of the sleep-disordered breathing. Patients with mild apnea have a wider variety of options, while those with moderate to severe apnea should be treated with nasal CPAP.
Conservative measures include weight loss, avoidance of alcohol for 4-6 hours prior to bedtime, and sleeping on the sides. These measures should be included in the treatment of all patients with OSAHS but should be used exclusively only in patients with very mild apnea whose main complaint is snoring.
Nasal CPAP: CPAP is the most effective treatment for OSAHS, and it has become the standard of care. CPAP works by splinting the upper airway, preventing the soft tissues from collapsing. By this mechanism, it effectively eliminates the apneas and/or hypopneas, decreases the arousals, and normalizes the oxygen saturation (see Image 6).
Most sleep center physicians still titrate the CPAP level during a sleep study. This can be conducted as a second night of study or during the second half of the diagnostic study (this type of study is called split-night polysomnography). Currently, CPAP devices are available that automatically change pressures based on the presence and/or absence of OSAHS. The exact indications for these devices are still being determined.
Recent Medicare guidelines specify criteria for ordering CPAP for patients with OSAHS. All patients with an AHI greater than 15 are considered eligible for CPAP, regardless of symptomatology. For patients with an AHI of 5-14.9, CPAP is indicated only if the patient has one of the following: excessive daytime sleepiness, hypertension, or cardiovascular disease.
CPAP has been shown to improve daytime sleepiness, mood, and cognitive function in people with both mild and moderate apnea. CPAP has also been shown to increase quality of life and decrease health care costs. Some data indicate that CPAP decreases blood pressure, primarily in patients with severe OSAHS (Becker, 2003; Pepperell, 2002; Faccenda, 2001). Evidence also suggests that CPAP may improve left ventricular ejection fraction in patients with congestive heart failure and OSAHS (Kaneko, 2003).
The most common side effects of CPAP are dry mouth, rhinitis, and sinus congestion. These can be treated effectively with humidification and antihistamines and/or nasal steroids.
Unfortunately, compliance is a major problem, with only about 50% of patients using CPAP on a regular basis. However, some evidence indicates that these patients will continue to use CPAP on an indefinite basis.
Oral appliances: These dental devices act by moving the tongue or mandible forward, enlarging the posterior airspace.
Oral appliances have been shown to decrease the AHI in most patients. However, they are most effective for patients with an AHI of less than 40 episodes per hour.
One study has directly compared treatment with CPAP to treatment with oral appliances. In general, scores for sleepiness and quality of life were better with CPAP; however, no differences in objective testing (eg, MSLT) were observed. Patients did not prefer one treatment modality over the other (Engleman, 2002).
In summary, evidence suggests that oral appliances may be appropriate first-line therapy in people with mild apnea and can be used as an alternative therapy for mild-to-moderate OSAHS if the patient does not tolerate CPAP.
Surgical Care: Surgical correction of the upper airway is no longer considered primary therapy. Generally, surgery is recommended only for patients for whom CPAP was unsuccessful, for patients who refuse to consider CPAP, and for those who have very mild (ie, AHI <10) OSAHS. Surgeries include the following:
Uvulopalatopharyngoplasty (UPPP) is resection of the uvula and soft palate. It is effective in about 40% of patients, but predicting which patients will benefit from the procedure is impossible. The new laser-assisted approach should only be used for patients with simple snoring. Long-term, patients with treatment success often present with of recurrence of symptoms.
Craniofacial reconstruction involves advancement of the tongue (ie, geniohyoid advancement with hyoid myotomy [GAHM]) or maxillomandibular bones (ie, maxillomandibular osteotomy [MMO]). These surgeries should be performed only at centers with expertise. Short-term success rates are approximately 70% for GAHM and 95% for MMO. No good long-term studies have been performed to evaluate the success for these surgeries.
Tracheostomy provides definitive correction because it bypasses the obstruction. It is recommended in very severe OSAHS, especially if the patient does not tolerate CPAP or has cor pulmonale.
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