Sleep Disorders in Adults
Sleep disorders are prevalent in American society. The National Commission on Sleep Disorders Research estimates that almost 20% of adults suffer from chronic sleep disorders and that an additional 10% suffer from intermittent sleep disorders. Sleep disorders have been linked to over 100,000 automobile accidents yearly with nearly 1500 fatalities and 75,000 injuries annually. They may also be responsible for up to 30% of commercial truck driving accidents. It has been estimated that chronic sleep deprivation costs $15 billion annually in direct medical expenses and an estimated $70 billion in lost productivity.
Although there are many disorders of sleep, this chapter deals specifically with sleep-disordered breathing because it is referable to the otolaryngologist.
Sleep is a reversible physiologic and behavioral state that manifests as decreased awareness and reaction to external stimuli. Normal sleep architecture comprises two distinct phases: NREM (non-rapid eye movement) sleep which comprises 75–80% of sleep and occurs in four stages (Stages I–IV), whereas REM (rapid eye movement) sleep which comprises 20–25% of sleep and occurs in two stages. In a normal adult, these two phases of sleep occur in semiregular cycles, which last approximately 90–120 minutes and occur three to four times per night.
In the normal adult male, Stage I (N1) sleep, which is considered the transition to sleep, occupies 2–5% of sleep and is characterized by an increase in theta waves and a decrease in alpha waves on an electroencephalogram (EEG). Stage I sleep is also marked by a decrease in awareness and in muscle tone. Stage II (N2) sleep occupies 45–55% of sleep and is characterized by K-complexes and spindles on EEG as well as decreases in muscle tone and awareness. Stage II sleep is considered by most authorities to be the “true” onset of sleep. Stages III and IV (N3) sleep comprise deep sleep, and it occurs predominantly in the first third of the night. The hallmark of deep sleep is the abundance of delta waves on EEG. Stage III sleep occupies 3–8% of sleep, and Stage IV sleep occupies 10–15% of sleep. Stages III and IV are widely considered the most restful stages of sleep. With increasing age, deep sleep progressively occupies less and less of total sleep time.
The remaining portion of sleep is composed of REM sleep, which is divided into tonic and phasic stages. During the tonic stage, the EEG becomes asynchronous and muscles lose tone. The phasic stage of REM sleep is characterized by rapid eye movements as well as erratic cardiac and respiratory patterns.
Derangements in sleep are categorized by the American Sleep Disorders Association in the International Classification of Sleep Disorders (ICSD), which arranged sleep disorders into four categories: dyssomnias, parasomnias, sleep disorders associated with medical-psychiatric disorders, and proposed sleep disorders (Table 41–1).
| Category | Subtype | Examples |
|---|---|---|
| Dyssomnia |
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| Parasomnia |
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| Medical-psychiatric disorders |
|
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| Proposed | Sleep hyperhidrosis, sleep-related laryngospasm |
The term apnea refers to a period of at least 10 seconds during which air flow is absent by nose or mouth. Apnea may be obstructive or central in origin. A hypopnea is a decrease in airflow to 10–70% of baseline for more than 10 seconds, associated with arousals or desaturation by at least 3%. The apnea hypopnea index (AHI) is the number of apneas and hypopneas per hour of sleep time and is based on a minimum of 2 hours of sleep. Many have debated the significance of this index because it does not reflect the absolute number of apneas and/or hypopneas, the duration of such events, or the distribution of such events during sleep. Some authors use the respiratory disturbance index (RDI), which is the AHI + arousal index, to help correlate with patient symptomatology.
Obstructive sleep apnea (OSA) is present when the AHI is ≥5 events/h. It is further classified as mild (5–15 events/h), moderate (15–30 events/h), and severe (>30 events/h). The obstructive sleep apnea syndrome (OSAS) is diagnosed when the AHI is >15 and the patient has nighttime and daytime symptoms.
The obesity hypoventilation syndrome is the most clinically severe form of sleep-disordered breathing and is characterized by chronic alveolar hypoventilation, obesity, daytime hypercapnia (PaCO2 > 45 mm Hg). It frequently becomes manifest with pulmonary hypertension and right heart failure.
American Sleep Disorders Association. The International Classification of Sleep Disorders Diagnosis & Coding Manual. American Academy of Sleep Medicine, 2001. (Lists and explains the various sleep disorders.)
National Commission on Sleep Disorders Research. Wake up America: A National Sleep Alert. Government Printing Office, 1993. (Offers facts and findings regarding sleep deprivation and its effects on citizens.)
- History of habitual snoring, excessive daytime sleepiness, or witnessed apneas.
- Neck size > 17 inches in males or > 15 inches in females and/or body mass index (BMI) > 27 kg/m2.
- Definitive evidence of OSA by polysomnography.
OSA is a disorder characterized by loud, habitual snoring and the repetitive obstruction of the upper airway during sleep, resulting in prolonged intervals of hypoxia and fragmented sleep. As a result, patients with OSA suffer from excessive daytime sleepiness, enuresis, poor work performance, and erectile dysfunction. The long-term sequelae are severe and can include accidents, hypertension, ischemic heart disease, cardiac arrhythmias, and stroke.
Large cohort studies have demonstrated that OSA is common: almost 25% of adult men 20–60 years old and 9% of adult women 20–60 years have an AHI > 5 events/h. It was further found that 4% of adult men and 2% of adult women had OSA syndrome with an AHI > 15 and both daytime and nighttime symptoms. Despite its prevalence, it is estimated that almost 85% of people with OSA remain undiagnosed.
The pathogenesis of OSA is multifactorial, and it is widely accepted that OSA lies somewhere on a continuum of sleep-disordered breathing (Figure 41–1) that begins with snoring and ends with obesity hypoventilation syndrome. Determining what causes a person to be susceptible to the conditions on the continuum is one of the goals of treatment.
Air moving through the upper airway encounters resistance in transit to the lungs, and in the apneic person, this resistance is increased. This new resistance increases the load on the respiratory musculature, which is required to overcome upper airway resistance with higher negative inspiratory pressures. The negative inspiratory pressure narrows the upper airway in an incremental fashion until, theoretically, the airway collapses. Soft tissue compliance, redundant upper air way mucosa, and pharyngeal dilator muscle tone are all presumed to play an important role. Clinically, this translates to progressive vibration and collapse of the upper aerodigestive soft tissue structures, causing snoring and obstruction of air flow.
The nose and nasal cavity appear to play less crucial roles in the pathogenesis of OSA. Over half of the normal resistance in the upper airway is generated at the internal nasal valve, and obstruction at this point narrows this inlet and increases upper airway resistance. Septal deviation and other causes of nasal obstruction may play a role in the pathogenesis of sleep-disordered breathing, and patients with allergic rhinitis have an increased risk for developing sleep-disordered breathing because of significant turbinate or mucosal swelling. However, these features are not believed to play significant roles in the average patient with OSA.
A number of risk factors for OSA have been identified. Obesity is one of them. A threefold increase in the prevalence of OSA occurs with 1 standard deviation increase in BMI above normal. Results from one study demonstrate a positive correlation between AHI severity and both the BMI and the circumference of a patient’s neck. Although men represented 47.2% of the study cohort, 71% of the participants with an AHI > 30 were men, indicating that men disproportionately represent those with OSA.
Although whites and blacks appear to be evenly represented as AHI severity increases, Native Americans appear to be disproportionately represented in groups with higher AHI. In addition to weight, neck circumference, sex, and race, other factors such as genetic syndromes (discussed later) and endocrine factors have also been implicated OSA. Patients with growth hormone abnormalities, specifically acromegaly, may develop OSA as a consequence of changes in craniofacial structure and upper airway collapsibility.
The most common nighttime symptoms of OSA include loud, habitual snoring, apneas, choking or gasping sounds, and nocturia or enuresis. Vibrations in upper airway soft tissues produce the loud, crescendo snoring and signify increased upper airway resistance. Apneas, which frequently terminate abruptly with gasping noises, represent complete upper airway obstruction. The negative inspiratory pressure generated during apneic events is transmurally delivered to the contracting heart and stretches the right atrium. As a consequence, atrial natriuretic peptide is released, leading to nocturia and enuresis in some patients. The repetitive arousals and frequent awakenings to micturate lead to sleep fragmentation, which may lead to daytime symptoms.
Nearly 30% of adult men and 40% of adult women with an AHI > 5 events/h report not feeling refreshed in the morning when arising. In addition, 25% of adult men and 35% of women with an AHI > 5 events/h complain of excessive daytime sleepiness, which can cause frequent napping or dozing, poor work performance, and automobile accidents.
All patients should be evaluated for hypertension since it is correlated with OSA severity. Because studies have shown a positive correlation between OSA and BMI > 27.8 kg/m2 in men and BMI > 27.3 kg/m2 in women as well as neck circumference—measured at the level of the cricothyroid membrane—>17 inches in men and >15 inches in women, weight and neck circumference should be recorded.
The outward appearance of thyromegaly or signs of dry skin, coarse hair, or myxedema may lead to a diagnosis of hypothyroidism, and an inattentive or unkempt patient who seems disengaged or speaks with a sad or flat affect may have undiagnosed depression. Both these conditions can cause excessive sleepiness or fatigue and should be considered before diagnosing OSA.
The patient is always examined in the Frankfurt plane—a line bisecting the inferior orbital rim and the superior rim of the external auditory meatus that is always parallel with the floor. To assess the patient for maxillary retrusion, a line dropped from the nasion to the subnasale should be perpendicular to the Frankfurt plane. To assess the patient for retrognathia, a line bisecting the vermillion border of the lower lip with the pogonion should be perpendicular to the Frankfurt plane as well. If the pogonion is retroposed more than 2 mm, retrognathia is suspected. A lateral cephalometric x-ray helps evaluate this area with precision.
The nose should be examined for signs of gross deformity, tipptosis, asymmetry of the nostrils, and internal valve obstruction. The examiner can perform the modified Cottle maneuver to dilate the nasal valve and assess for improvement in breathing. The nasal cavity should be thoroughly examined for turbinate size, signs of polyps, masses, rhinitis, and purulent discharge. The septum should be examined for signs of defects or deviation. Nasopharyngoscopy permits evaluation of the posterior choanae (to discover the rare case of stenosis or atresia), the eustachian tube orifices, the velopharyngeal valve, and the adenoids, and it can provide direct observation of the velopharynx during the Müller maneuver, which some believe to be helpful in identifying the site of obstruction in OSA.
The tongue should be examined for size and for stigmata of OSA. A normal-sized tongue rests below the occlusal plane, and a tongue that extends above this plane is graded as mildly, moderately, or severely enlarged. Tongue crenations, or ridging, if found, may indicate macroglossia. The relationship between the tongue and the soft palate should also be observed, specifically to determine whether an enlarged tongue obscures vision of the palate, whether the palate itself is low-lying or deviated, or whether the posterior pharyngeal wall is obscured by both. The morphology of the soft palate (ie, thick, webbed, posteriorly located, low, and so on) should also be noted. The uvula is also described as normal, long (>1 cm), thick (>1 cm), or embedded in the soft palate. The tonsils should be described as being surgically absent (0) or by their size (1, 2, 3, or 4+, respectively, indicating a 0–25%, 25–50%, 50–75%, or > 75% lateral narrowing of the oropharynx). The tonsils should also be examined for any asymmetry or any other pathology. A narrow oropharynx, independent of tonsil size, should also be noted. A system of examination and staging of the oral cavity examination has been described termed the Obstructive Sleep Apnea/Hypopnea Syndrome Score (OSAHS Score), which is described below.
The hypopharynx can be evaluated by means of flexible nasopharyngoscopy to assess the base of tongue and the lingual tonsils and to look for masses obstructing the supraglottic, glottic, or subglottic larynx. Obliteration of the vallecula, retrodisplacement of the epiglottis obscuring the larynx, lateral pharyngeal narrowing, and general obstruction by the tongue base may indicate hypopharyngeal collapse during sleep. Any abnormalities in appearance, symmetry, and movement of the vocal cords should be noted. Many perform the Müller maneuver to assess collapse of the retropalatal and retroglossal areas during inspiration against a closed nose and mouth scored as a percentage of closure during the maneuver. Opinions on the clinical usefulness of this maneuver are mixed.
Although description of the structures as noted above appears useful in determining the site of obstruction in OSA, a more formalized staging system has been created (Table 41–2). This system includes three sections including (a) the standard description of tonsils from 0-4, (b) the oral cavity/tongue (Figure 41–2), and (c) BMI. It has been shown to be useful to predict the probability of success in uvulopalatopharyngoplasty for sleep apnea and can serve as a single score to describe patients with OSA.
Figure 41–2.
Friedman palate position. The Friedman palate position is based on visualization of structures in the mouth with the mouth open widely without protrusion of the tongue. Grade I allows the observer to visualize the entire uvula and tonsils. Grade II allows visualization of the uvula but not the tonsils. Grade III allows visualization of the soft palate but not the uvula. Grade IV allows visualization of the hard palate only.
A host of imaging modalities can play a role in identifying the patient with OSA; however, most of them have limited clinical application, and some remain investigational.
Lateral cephalometric studies and plain film x-rays are useful in evaluating the patient with observable craniofacial abnormalities such as midface hypoplasia or mandibular retrusion. These studies are required for precise evaluation of maxillary retrusion, retrognathia, and micrognathia, and they help in planning Phase I and Phase II surgical procedures (discussed later in this chapter). The studies are inexpensive to perform, and the equipment is widely available. However, as a diagnostic tool for OSA in general, they suffer from several limitations including exposure to radiation, absence of supine imaging, and lack of soft tissue resolution.
CT scanning and MRI are also commonly available and have facilitated an increased understanding in the differences between the normal and apneic airways (Figure 41–3). Images obtained with both modalities can be used to recreate three-dimensional models of the upper airway and have been used to evaluate apneic airway dynamics during respiration. Both modalities, however, are significantly more expensive than the previously mentioned modalities and have a number of contraindications. Furthermore, CT and MRI have yet to be proved effective in identifying patients with OSA or reliably characterizing OSA severity.
Figure 41–3.
Comparative axial anatomy. Axial magnetic resonance images acquired at the retropalatal levels in a normal patient (left) and an apneic patient (right) demonstrating (1) increased lateral pharyngeal wall dimensions, (2) decreased retropalatal airway area, and (3) increased lateral pharyngeal fat pads in a representative apneic patient. (Image contributed by Richard J. Schwab, MD, University of Pennsylvania Health System, Philadelphia, PA.)
Subjective tests permit the patient to evaluate his or her drive to sleep. These include the Epworth Sleepiness Scale (ESS)
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