Pathophysiology

OSA is characterized by symptoms that result from the recurrent sleep-associated collapse of the pharyngeal airway and that lead to hypoxemia, hypercapnia, and fluctuations in intrathoracic pressure caused by increased respiratory effort, with arousal from sleep required to reestablish airway patency. When awake, protective mechanisms increase the activity of the pharyngeal dilator muscles; however, during sleep, these mechanisms may fail and result in the collapse of the pharyngeal airway.45,73,120,293,329,346,349,387 This is made worse by nighttime horizontal and supine sleep positioning.^244,256 Frequent locations of pharyngeal collapse include the velopharynx (behind the soft palate), the oropharynx (behind the tongue), or both.²⁴⁰

Schwab and colleagues have documented an increase in adipose hypertrophy within the floor of the mouth, the soft palate, the pharyngeal fat pads, and the lateral pharyngeal walls in many individuals with OSA.³²⁴ In patients with obesity, there is a direct deposition of fat that causes submucosal adipose volume expansion within the pharyngeal walls (thus narrowing the lumen) and the floor of the mouth (thus causing elevation and retro positioning of the tongue), thereby diminishing the actual upper airway breathing space and, in many cases, explaining the greater extraluminal critical closing pressure documented in patients with OSA. Evidence supports the concept that many individuals with OSA have an anatomic predisposition to airway collapse as a result of retrusive jaws and obstructed nasal cavities. An individual’s unique baseline skeletal (i.e., jaw) anatomy may have a dramatic effect on the size (i.e., the luminal diameter) of the upper airway. It is now also appreciated that the variability in upper airway breathing space from one person to the next is influenced by the subject’s developmental or congenital maxillofacial skeletal morphology. Deficient maxillomandibular structural support adds to the environmental causes (i.e., weight gain) that thicken the pharyngeal soft tissues, thereby further narrowing the lumen and diminishing the patency afforded by pharyngeal dilator muscle contraction forces that work to maintain and open the airway. Genetics plays a lesser role in the observed volumes of the tongue, the soft palate, the adenoids, the turbinates, and the tonsillar tissues seen in individuals with OSA. These soft-tissue structures are more likely to be affected by acquired conditions such as weight gain, infections, or allergies. With obesity, there may also be alterations of pharyngeal muscle orientation and function. These factors combine to determine overall upper airway breathing space, pharyngeal muscle function, and, as a consequence, the occurrence of apnea events during sleep.

Schwartz and colleagues measured the critical closing pressures during sleep in individuals with OSA and compared these values to those of controls (i.e., individuals without OSA).³²⁷ Individuals with baseline anatomically “large-volume” airways are less dependent on pharyngeal dilator muscles to maintain airway patency than those with intrinsic “small-volume” anatomic airways. Schwartz and colleagues showed that control subjects (i.e., individuals without OSA) typically have critical closing airway values of less than 0 cm of water, whereas those with severe OSA have values of more than 8 cm of water. Multiple diagnostic modalities (e.g., cephalometric x-rays, computed tomography [CT] scans, acoustic reflection, magnetic resonance imaging) confirm that individuals with OSA generally have “smaller-volume” baseline awake airway lumens as compared with controls.²⁶⁴

According to Fogel and colleagues the pharyngeal muscles of primary importance fall into three groups⁸⁷:

The activity of these muscles is normally increased during inspiration to stiffen and expand (i.e., open) the upper airway. This counteracts the collapsing influences that would otherwise occur with inspiratory negative airway pressure. During expiration, the muscles normally substantially relax while positive pressure is flowing through the respiratory tree. The tensor palatine is an exception in that it must maintain a constant level of tone throughout the respiratory cycle to preserve a patent airway. Fogel and colleagues stated that the activity of the pharyngeal dilator muscles during wakefulness is tightly controlled to maintain pharyngeal patency.⁸⁷ In individuals with an anatomically “small-volume” airway, the activation of this negative-pressure reflex (i.e., feedback mechanism) to increase the function of the pharyngeal muscles must occur to prevent or limit apnea. This reflex has been shown to be diminished in apnea-prone individuals for both the genioglossus and the tensor palatine muscles. An individual’s use of specific medications (e.g., alcohol, sedatives, narcotics) will also negatively influence the reflex arc, thereby causing the relaxation of the muscles and further diminishing airway patency.

At least until the age of 65 years, age is positively correlated with OSA severity as demonstrated by an increase in the AHI.¹⁵² This increase is substantially greater in the presence of baseline maxillomandibular sagittal deficiency. While a person is awake, neuromuscular mechanisms and body position (i.e., standing or sitting up) can positively influence and compensate for the “small-volume” airway. However, the pharyngeal dilator muscles are less able to effectively contract during sleep, which results in the more frequent collapse of the anatomically small breathing space. The ability of the pharyngeal muscles to compensate for and prevent apnea events becomes progressively more difficult with age and in the presence of weight gain.

Frieberg and colleagues hypothesized that a progressive lesion in the afferent and/or efferent nerve pathways caused by repetitive “snoring trauma” may also contribute to the collapsibility and obstruction of the upper airway that is seen in patients with OSA.89–91 Their study evaluated the hypothesis of the presence of a progressive neurogenic lesion in the pharyngeal muscles in patients with longstanding upper airway obstruction. Biopsies of palatopharyngeal muscle were obtained from patients (n = 21) with habitual snoring and degrees of upper airway obstruction and compared with those of non-snoring control subjects (n = 10). The degree of abnormality found was significantly increased in the study patients as compared with control subjects. The results of their research support the hypothesis of a progressive local neurogenic lesion that is caused by the “trauma of snoring” as a possible contributory factor in upper airway collapsibility.

Sleep electroencephalograms (EEGs) of patients with OSA will differ from those of individuals with upper airway resistance syndrome (UARS) and from those of control subjects.117,128 The arousal response of individuals with OSA is delayed, despite the fact that increased respiratory effort is seen during the obstructive phase. This delayed arousal response has been confirmed by differences in the patterns of EEG findings. Guilleminault and colleagues hypothesized that a difference in sensory input may be the responsible factor for the divergent responses to the abnormal breathing patterns that may exist between individuals with UARS and those with OSA.¹²² The authors set out to compare the results of a palatal mucosa two-point discrimination response in normal subjects (n = 15), those with OSA (n = 15), and those with UARS (n = 15). The subjects were matched for age, sex, and body mass index. The 45 subjects were submitted to a two-point discrimination study of the palatal mucosa during wakefulness. Individuals with OSA had a clear impairment of their palatal mucosa sensory input with a significant decrement in two-point discrimination. Interestingly, the subjects with UARS and the normal control subjects responded similarly to each other. The responses seen in individuals with UARS indicate that those individuals are more capable of transmitting sensory inputs than individuals with OSA. This may be at least one factor that explains the difference in arousal response that is been documented in patients with UARS as compared with those with OSA.¹²²

For the individual with OSA, as apnea events become more frequent, hypoxemic and hypercarbic episodes require increased respiratory effort to ultimately achieve arousal from sleep. With awakening from the apnea event, there is a reestablishment of airway patency, and ventilation proceeds. The individual then returns to sleep, and the cycle repeats itself. This repetitive pattern of sleep disruption not only affects the quality of the individual’s life (i.e., behavior derangements), but it also affects their longevity (i.e., pathophysiologic derangements).

The basic anatomic factors that reduce the size of the upper airway include the following:

The term pharynx is used to describe the anatomic region that extends from the esophageal entrance up to the back of the nose. It is further subdivided according to proximity to the nose, mouth, and throat down to the larynx. Together, these pharyngeal structures are involved in critical physiologic functions, including breathing, swallowing, vocalization/speech, and mastication. Each of these functions is potentially influenced by any one of the upper airway anatomic components. The upper airway functions as a continuous cohesive organ; it is commonly defined as the soft-tissue region that is bounded by the nasopharynx superiorly, the epiglottis inferiorly, the maxillomandibular complex anteriorly, and the spinal column posteriorly. The upper airway is somewhat artificially subdivided into the following regions:

An increased body mass index (BMI), which is also known as obesity, is a known risk factor for OSA in children, adolescents, and adults (Fig. 26-1).^{21,88,241,255,337} Peppard and colleagues outlined the cardiovascular risks associated with OSA for weight gain and weight loss.^269,268 Excessive body weight was found to be positively associated with OSA,²⁶² and the stability of the individual’s weight was also found to be an important factor. A 10% weight gain predicted a 32% increase in the AHI.³¹⁹ The same 10% gain in weight also predicted a six-fold increase in the odds of moderate to severe OSA developing. Interestingly, a weight loss of 10% predicted a 26% decrease in the AHI.¹⁶⁹ Unfortunately, studies consistently document that weight loss programs in patients with OSA frequently fail miserably. Any weight loss that the individual is able to initially achieve tends to be temporary.¹⁶⁷

When an individual’s BMI is elevated, the volume of fat in the pharynx and the floor of the mouth also increases. It is estimated that more than 66% of individuals with OSA are obese. On the basis of the latest World Health Organization statistics, it is estimated that there are more than 1.6 billion overweight adults (from a total population of 6.5 billion) and at least 400 million obese individuals (BMI ≥ 25 kg/m²) on Earth.⁷² Obesity has both a genetic and an environmental basis.^{37,63,102,165,237} A review of population studies suggests that heredity accounts for at least 40% of the variance in BMI.^219,286 Studies have demonstrated a strong relationship between the BMIs of biologic parents and their children. Interestingly, no relationship between the BMI of adoptive parents and their adopted children has been documented. The best indirect indicator of excessive fat accumulation in the pharyngeal region and the floor of the mouth is a person’s BMI.

Studies have also documented that relatives of individuals with OSA demonstrate a higher incidence of hypoplastic maxillae and mandibles, longer soft palates, and wider uvulas as compared with matched controls.219,326 This also speaks to the hereditary component of a small pharyngeal airway space and to an individual’s genetic predisposition to OSA.^295,388

There are specific syndromes and conditions that result in severe maxillomandibular skeleton dysmorphology and that also negatively affect the upper airway (e.g., Crouzon syndrome, Apert syndrome, Treacher Collins syndrome, Pierre Robin sequence).17,38,270,271,287,341,354,390 It is documented that more than 50% of individuals with Down syndrome suffer from OSA.⁶⁶ Interestingly, a similar percentage of individuals with Down syndrome are known to have a baseline intrinsic developmental jaw deformity that is characterized primarily by maxillary deficiency. The surgical correction of the maxillofacial deformities associated with these syndromes have been documented to enlarge the upper airway space and to improve and often resolve breathing difficulties, including OSA (see Chapters 27, 28, 30 and 31). The surgical management of velopharyngeal insufficiency (i.e., superiorly based pharyngeal flap or sphincteroplasty) in individuals with a repaired cleft palate is also known to result in OSA in some cases.^{4,39,157,176,187,205,257,258,339,340,343,373,389,396} Interestingly, the non-syndromal developmental dentofacial deformities (e.g., long face growth pattern, short face growth pattern, primary mandibular deficiency, maxillary deficiency with relative mandibular excess, maxillary hypoplasia associated with repaired cleft palate), which affect at least 5% of the general population, also negatively affect the upper airway.²¹² Unfortunately, these more common patterns of jaw disharmony frequently go unrecognized as significant etiologic factors for OSA (Figs. 26-2 and 26-3). It is incumbent on the otolaryngologist, the pulmonologist or sleep specialist, the pediatrician or internist, the orthognathic or maxillofacial surgeon, and the general dentist or orthodontist to understand the fundamental relationship between developmental jaw deformities and upper airway obstruction in each patient who is evaluated.

Not infrequently, the individual with “mandibular prognathism” has undergone a lower jaw set-back treatment to improve the occlusion. Historically, such procedures have been preferred by many clinicians for the treatment of skeletal Class III patterns. However, it is now known that this approach is associated with a risk to the airway size and shape.6,18,41,48,67,68,74,78,84,113,115,171,172,174,314,316,370,386 Demetriades and colleagues confirmed the clinical importance of considering the airway when formulating a treatment plan for the correction of so called “mandibular prognathism.”⁶⁹ They described 26 patients who presented with developmental dentofacial deformities that were characterized by maxillary deficiencies in combination with relative mandibular excesses. Each patient underwent mandibular ramus osteotomies with at least some set-back. The patients were divided into two groups. The Group 1 patients (n = 13) underwent mandibular setback of at least 5 mm without simultaneous Le Fort I osteotomies. The Group 2 patients (n = 13) also underwent a degree of mandibular set-back, but in conjunction with Le Fort I advancement. All study patients (Groups 1 and 2) underwent preoperative and postoperative lateral cephalometric radiography and portable PSG. The preoperative and postoperative radiographs were compared, and any changes that occurred in the position of the hyoid bone, the distance from the posterior nasal spine to the palate, the retrolingual space, and the hypopharyngeal space were measured. The authors confirmed that mandibular retropositioning of at least 5 mm can significantly decrease the posterior airway space and cause mild to moderate OSA. The study also suggested that, when a limited mandibular set-back is carried out in combination with maxillary Le Fort I advancement, significant negative effects on the airway are likely to be prevented.

In summary, anatomic upper airway risk factors for OSA include the following: 1) regional obesity (i.e., increased upper airway submucosal adipose tissue deposition); 2) retrusive maxillomandibular skeleton (e.g., hypoplasia of the maxilla or mandible); 3) alterations in the intranasal cavity (e.g., septal deviations, hypertrophic inferior turbinates, tight nasal aperture, elevated nasal floor, adenoid hypertrophy); 4) enlargement of other critical upper-airway soft-tissue visceral structures (e.g., soft palate, tonsils, tongue); and 5) inadequate pharyngeal muscular tone (i.e., hereditary and environmental factors).320,332,348,378 Each of these head and neck structural aspects predispose individuals to OSA by causing upper-airway narrowing during wakefulness and airway collapse during sleep. When these aspects occur in combination, the risk is greatly exacerbated. There are also specific medical conditions (e.g., myasthenia gravis, Parkinson disease, amyotrophic lateral sclerosis) as well as certain medications and drugs (e.g. alcohol, narcotics, sedatives, muscle relaxants) that are known to negatively affect the neuromotor tone of the chest wall and the pharyngeal musculature and thus predispose an individual to apnea.

Basic Clinical Evaluation

A thorough medical and sleep history should be taken and a physical examination completed. The following information should be especially considered for an individual with known OSA:

It is also recommended that a subjective questionnaire be used to assess for OSA. The Epworth Sleepiness Scale (ESS) is considered the reference standard.86,163,164 The survey assesses the respondent’s propensity for sleep in eight different situations. Although the survey is not perfect, it does provide useful information about the patient’s waking sleepiness.

An airway analysis that is based on CT scan data may also be a useful tool to assess upper airway space. A recent study used three-dimensional computer analysis from cone-beam CT to present normative upper airway size reference data. The collected data confirm that, in humans, the airway size and length increases until the age of 20 years, at which time there is a variable period of stability. After this stable period, the airway at first decreases slowly in size; then, after the age of 50 years, it decreases more rapidly.³²² Li and colleagues demonstrated a correlation between the airway area and the likelihood of OSA.¹⁹⁷ There is a high probability of severe OSA with an airway area of less than 52 mm²; an intermediate probability if the airway is between 52 mm² and 110 mm²; and a low probability if the airway area is more than 110 mm².¹⁹⁰ Cillo and colleagues attempted to correlate specific cephalometric measurements with the AHI in a consecutive series of patients (N = 101) who were documented to have OSA. Unfortunately, no one skeletal or soft-tissue parameter could be linked to OSA.⁵¹ Three-dimensional CT airway analysis has documented quantifiable changes in patients’ oropharynges after specific surgical interventions. This type of imaging may also be used to evaluate changes in the airway after specific medical interventions (e.g., weight loss).⁷⁵

Susarla and colleagues used a case–control study that was designed to analyze the value of the cephalometric upper airway length (UAL) measurement as an indirect predictor of the presence and severity of OSA.360,361 The study group included adults (n = 96) with PSG-documented severe OSA and a control group of adults (n = 56) with skeletal Class II malocclusion without known OSA. Although significant attention has been devoted to describing and measuring upper airway width, little attention has been devoted to measuring UAL. The theory behind this study is that an important component of the airway resistance is the airway length (i.e., the vertical dimension), which is known to be directly correlated with airway resistance per Poiseuille’s law: resistance equals 8 ηL/πr₄ (L = length). The results of the study suggest that the UAL (i.e., the distance between the posterior hard palate and the most superior aspect of the hyoid bone on a line parallel to the long access of the airway) is predictive of the presence of OSA in both men and women. The study results indicate that a cephalometric UAL of 72 mm or more in men and 62 mm in women was diagnostic for OSA with high sensitivity and specificity. It would appear that both a narrow posterior airway space and a long UAL predispose individuals to upper airway obstruction and that both conditions are associated with increased odds of OSA.

A reasonable predictor of OSA is a clinical triad of symptoms that includes loud snoring, apnea witnessed by a bed partner, and excessive daytime sleepiness. When the sleep and daytime history is combined with attended PSG, the patient’s clinical head and neck examination (including instrumentation), and a focused radiographic analysis, then an overall picture of the upper airway anatomy and function can be seen.*

Attended Polysomnography

Overnight PSG conducted in a sleep laboratory remains the reference standard for the diagnosis of central sleep apnea or OSA.92,111,155,180,365 PSG requires the use of several monitoring parameters, including EEG, electrooculography, electromyography, electrocardiography, the microphone measurement of snoring, pulse oximetry, respiratory inductance plethysmography, airflow measurement, and the recording of the body position. PSG primarily evaluates sleep-disordered breathing, sleep architecture, and oxygen desaturations. During PSG, episodes of apnea and hypopnea are determined from a reduction in airflow in combination with oxygen desaturation during a 4- to 8-hour time frame.

It is recommended that all sleep studies for a surgical patient be attended overnight PSG. Parameters reviewed after attended PSG should include the following:

To be most accurate as a diagnostic tool, the PSG study should be current (i.e., within the previous 6 to 12 months) and, if possible, not a split-night study. Split-night studies apply CPAP for the second half of the night and may underestimate the severity of OSA. An alternative to an attended sleep study is a home sleep study. Home sleep studies lack all of the monitoring parameters of an attended overnight PSG. However, advantages of home sleep studies include reduced costs and the ability to perform the sleep study in the patient’s native sleeping environment. Disadvantages include the gathering of fewer sleep parameters and possibly reduced reliability.

Assessment of Apnea Severity

By convention, the severity of OSA is classically determined by the AHI. The term obstructive apnea refers to apnea despite continued respiratory effort. Apnea is defined as the cessation of airflow for at least 10 seconds in an adult or for the equivalent of two breaths in a child. Hypopnea is defined as 1) a substantial reduction in airflow (i.e., >50%); or 2) a moderate reduction in airflow (i.e., <50%) with oxygen desaturation of more than 3%; or 3) EEG evidence of arousal in combination with oxygen desaturation that lasts for at least 10 seconds in an adult or for the equivalent of two breaths in a child. The AHI is a count of the number of apneas and hypopneas per hour of sleep. The respiratory disturbance index (RDI) is also used to describe OSA. The RDI considers the number of apneas, hypopneas, and respiratory-effort–related arousals per hour of sleep. Respiratory-effort–related arousals are EEG arousals that are not associated with clear-cut apnea or hypopnea but rather with slight changes in airflow or respiratory effort.

In adults, an AHI of 5 to 15 is regarded as mild OSA, an AHI of 15 to 30 is considered moderate OSA, and an AHI of 30 or more is severe OSA. (OSA during childhood is discussed later in this chapter.) Interestingly, the reliability of data procured during the sleep study and its interpretation by sleep specialists has not been verified through intra-observational or inter-observational studies.

Characterization of Apnea

Central sleep apnea is characterized by a lack of drive to breathe during sleep that results in insufficient or absent ventilation with compromised gas exchange. This may occur as a result of a number of known neuromuscular disorders, or it may not have a specific cause. OSA occurs when ongoing respiratory efforts are observed during the cessation of airflow within the upper airway. Central sleep apnea, like OSA, is associated with frequent nighttime awakening; excessive daytime sleepiness; and an increased risk of adverse cardiovascular outcomes. Central sleep apnea as classically defined is relatively uncommon (i.e., it is seen in <5% of patients referred to a sleep clinic).

Interestingly, it is recognized that 10% to 20% of individuals with known OSA will fail to respond to successful anatomic surgical expansion of the maxillomandibular complex. Another difficult to explain subgroup of individuals with documented OSA is that group with apparent normal upper airway morphology (i.e., no significant narrowing). Complex sleep apnea is a newly recognized category in the spectrum of sleep apnea syndromes that helps to explain these outliers. According to Susarla and colleagues, complex sleep apnea often presents with morphologic features that are typical of obstructive disease but that are combined with PSG evidence of strongly chemoreflex-modulated sleep breathing.³⁶⁰ Complex sleep apnea is distinguished from other forms of OSA by the following:

Susarla and colleagues believe that a lack of resolution of OSA after successful maxillomandibular advancement surgery may occur if a ventilation control disturbance either remains or is amplified.³⁶⁰ These individuals with chemoreflex-sensitive apnea can be identified, because they are extremely prone to changes in their carbon dioxide levels. It is important to make an accurate diagnosis, because these patients can be expected to require further management of the central component to their apnea. Helpful treatment for this unique subgroup may include the use of nasal oxygen, pharmacologic agents, or positive-pressure–based adaptive ventilation. Affected individuals require continued reassessment and management by a knowledgeable clinical sleep specialist.

Sites of Functional Obstruction

Studies that attempt to localize the site of upper airway obstruction in an individual with moderate to severe OSA have shown that there is rarely a single anatomic site of blockage (see Figs. 26-1 through 26-3). More commonly, multiple sites of upper airway obstruction occur during episodes of hypopnea and apnea. As stated, the potential upper airway sites of obstruction are somewhat artificially grouped as 1) intranasal; 2) retropalatal; and (3) retroglossal. In addition to taking a history and a physical examination, diagnostic studies to further clarify the anatomic levels of obstruction include the Müller maneuver, which is observed during nasoendoscopic instrumentation; lateral cephalometric radiographs taken during end-tidal volume measurement with the Müller maneuver; helical CT; and magnetic resonance imaging.

Manifestations in Children

Snoring and difficulty breathing during sleep are the most common complaints reported by parents of children with OSA.54,249,400 However, in contrast with reports of OSA in adults, excessive daytime somnolence is believed to be less common in children, with only 7% of 10% of pediatric patients with OSA experiencing this symptom. Neurocognitive deficits and behavioral manifestations are more frequent in children and may be the result of the chronic exposure to intermittent hypoxemia and sleep disruption caused by sleep fragmentation. Children with OSA are more likely to present with symptoms of hyperactivity, inattentiveness, poor academic performance, and behavioral problems.^{30,49,60,112,152,166,229,231,253,254,312} Such symptoms are often attributed to attention-deficit/hyperactivity disorder; treatments prescribed for this disorder (e.g., pharmacologic therapy with stimulants) can actually worsen sleep symptoms.

Diagnostic Criteria in Children

Diagnostic criteria for OSA in adults are typically the product of consensus and often include an AHI of 5 or more as documented by nocturnal PSG as well as evidence of disturbed or unrefreshing sleep, daytime sleepiness, or other daytime symptoms.313,382 The rationale for specific AHI diagnostic criteria in children as compared with adults suffers from less available data and heterogeneity across studies. Part of the problem is that few studies have been performed to link specified levels of pediatric OSA with adverse outcomes. At present, an AHI or RDI of as low as 1 event/hour is used to identify children with OSA. Pediatric criteria for scoring AHI or RDI are used until the age of 13 years as a matter of routine. According to the most recent American Sleep Disorder Association guidelines, either the pediatric or adult criteria for OSA may be used for adolescent patients who are between 13 and 18 years old at the discretion of the scoring sleep specialist.^12–16 It is also unclear how many events per hour should be considered significant in the adolescent patient as compared with pediatric and adult patients.⁵

Treatment Considerations in Children

Adenotonsillectomy (T&A) is generally considered to be the standard first-line treatment for a child with OSA who does not have complex medical conditions that would make surgery an unacceptable risk.34,121,124,183,188,220,224,230,232–234,298,317,344,351,355,366,384 A child with OSA should not undergo T&A without receiving a thorough evaluation of the entire upper airway to confirm the actual need for an operation. Nevertheless, the overall cure rate of T&A during childhood is believed to be as high as 82.9%. Studies indicate that, for children with documented OSA and a preoperative RDI of less than 19 events/hour, a T&A will frequently reduce the RDI to less than 5 events/hour. Alternatively, if the preoperative RDI is greater than 19 events/hour, then the T&A has a low probability of reducing the RDI to less than 5 events/hour.³⁵⁵ Other anatomic causes for the child’s OSA should be considered (e.g., maxillomandibular hypoplasia).

A tight nasal inlet is another common cause of upper airway obstruction that may be first recognized during childhood (see Chapter 10). Clinical studies have documented that maxillary arch expansion will improve a tight nasal inlet and thereby decrease nasal airway resistance. Maxillary arch expansion, which is accomplished with the use of a rapid palatal expansion appliance, is commonly carried out during childhood with little morbidity.^{8,27,36,79,399} Unfortunately, rapid palatal expansion will only address the one site of obstruction and in a limited way. No studies have confirmed that this approach alone will be effective for OSA. For children in whom T&A or rapid palatal expansion is required but does not lead to the resolution of OSA, evaluation to confirm the additional sites of obstruction should follow and appropriate interventions considered. The option of the administration of CPAP should be entertained, but the overall long-term adherence rate for CPAP is unknown and felt to be problematic in this population. Skeletal reconstruction is likely to be beneficial in a child with a craniofacial anomaly that is known to obstruct the upper airway and in whom OSA has been documented.^{17,38,53,270,271,287,341,354,390} For example, maxillary advancement in a child with either Apert or Crouzon syndrome and documented OSA has proven value (see Chapter 30). When a small lower jaw with a retro positioned tongue (i.e., some children with Treacher Collins Syndrome or Pierre Robin sequence) is the cause of OSA, then mandibular advancement can also be helpful (see Chapter 19). Developmental jaw deformities (i.e., long face growth pattern, short face growth pattern, and isolated mandibular deficiency) occur frequently in the general population, but they often go unrecognized as causes of OSA in children and teenagers (see Chapters 19, 21, and 23). After a developmental jaw deformity has been recognized in a child, OSA should be ruled out.^126,383 Referral to an orthognathic surgeon familiar with OSA is recommended if the PSG is positive (Figs. 26-4 and 26-5).

Bariatric Surgery

Rasheid and colleagues completed a prospective study in a consecutive series of patients (n = 100) that underwent gastric bypass for the management of obesity to determine the effects of the surgery on OSA.²⁹⁰ Before surgery, all patients underwent PSG. The mean preoperative RDI was 40 ± 4. Thirteen patients had no OSA, 29 had mild OSA, and 58 had moderate to severe OSA. At 6 months after surgery, patients’ BMIs had improved (38 ± 1 kg/m² versus 54 ± 1 kg/m²), and so had their ESS scores (6 ± 1 versus 12 ± 0.1). There were also a significant reductions in minimum desaturations during sleep as well as improvements in sleep efficiency. A shortcoming of the study was its conclusion at just 6 months after surgery.

A study by Pillar and colleagues describes the long-term follow up of patients with regard to both weight loss and upper airway findings after bariatric surgery.²⁷³ At 4 months after surgery, there was a significant improvement in the AI from 45 events/hour to 11 events/hour. Over a 7-year time frame, the AI regressed from a mean of 11 events/hour back up to 24 events/hour; however, the AI remained at a much lower level (24 events/hour) than it was before surgery (45 events/hour). In their report, the effectiveness of bariatric surgery was to reduce the mean BMI from 40 kg/m² (i.e., morbid obesity) to a mean BMI of 35 kg/m² (i.e., obesity) at 7 years after surgery. During the same time frame, the mean AI was reduced from 45 events/hour down to 24 events/hour. Other researchers have also studied the long-term effects of bariatric surgery on patient health.^{52,97,116,134}

Continuous Positive Airway Pressure Option

The use of CPAP for OSA was first reported in 1981. Since its introduction, it has become the reference standard for non-surgical management.43,65,66,71,105,107,114,132,148,159,160,178,181,217,236,267,356,357 With this method, positive pressure can be continuously delivered through a sealed nasal or mouth mask that the patient wears while sleeping. The positive pressure has the potential to pneumatically splint open the whole pharyngeal airway by preventing the soft palate and the tongue from making a seal with the posterior pharyngeal mucosa (i.e., it acts as a counteracting force to the aforementioned collapsing force in the patient with an anatomic predisposition for airway obstruction). The pressure required to achieve this goal is titrated at a sleep laboratory during PSG. CPAP is a sound, evidence-based treatment option that has been shown to be effective when it is used correctly and consistently throughout the night as well as night after night throughout the patient’s life. If CPAP is used in this way, it will decrease daytime sleepiness and therefore likely improve the patient’s mood and quality of life. The discomfort and difficulty associated with the use of CPAP (e.g., drying of the nasal and oral mucous membranes, dislodgment during sleep, noise, inconvenience when transporting the unit, social displeasure, feelings of claustrophobia) makes long-term compliance a clear problem. Even when defining an acceptable CPAP compliance rate of just 4 hours per night for 70% of nights, only a limited percentage of patients (depending on the study reviewed) who consider themselves users of CPAP are adherent. This does not take into account the significant number of those with OSA who either will not consider trying CPAP or those who have tried it but then refuse to use it. Furthermore, this “acceptable compliance rate” represents only approximately 50% of functional sleep time.^{77,252,291,318,385} Sleep medicine clinicians continue to appreciate the complexity of the disorder (i.e., complex chemoreceptor apnea and apnea-related behavioral derangements), and they now acknowledge the inability of a majority of patients to stick with CPAP for the long term, even if they do use it for the short term. Nevertheless, all individuals should be advised of the availability of CPAP and encouraged to consider it.

The American Heart Association/American College of Cardiology Foundation released a position statement about the effects of sleep apnea on cardiovascular disease.¹³³ The organizations summarized published studies that confirmed the moderate and variable effects of CPAP therapy for OSA on blood pressure. They concluded that individuals with more severe OSA, difficult-to-control hypertension, and better CPAP compliance are likely to have more substantial blood pressure reduction with CPAP. They also recommended that, for those hypertensive patients who were either not willing to use CPAP or not compliant, other effective methods of managing OSA should be considered (e.g., MMCA).

A sleep medicine specialist consult is often beneficial for the patient to maximize his or her education about the disease process and its effects (both behavioral and pathophysiologic) and to explore the CPAP option. Likewise, all patients should be advised of potential surgical alternatives that may apply to them. An evaluation by a surgeon who is familiar with current literature and treatment modalities is beneficial to fully explore non-CPAP options. Clearly, not all surgical options have equal success for each patient. A frank discussion with a knowledgeable surgeon regarding the patient’s specific potential benefit-to-risk ratio for each surgical procedure is essential (see discussion to follow).

Oral Appliance Option

The objective of an oral appliance (OA) for the treatment of OSA is to mechanically reposition and hold the mandible in a protruded (forward) location during sleep.²⁵⁹ As the mandible moves forward, so does the tongue. An effective OA must prevent the sealing of the tongue to the posterior pharyngeal mucosa, thereby limiting obstruction at that site.³⁷⁴ The upper airway response to oral appliances varies among individuals. It has been stated that up to 50% of individuals with OSA who use an oral appliance will “respond to some extent.”²¹⁸ Unfortunately, no matter how technically precise the OA is, it can only affect the retroglossal site.^213,325 Most individuals with moderate to severe OSA have obstruction at multiple sites.³⁷⁷