The spectrum of sleep-related breathing difficulties—including snoring, upper-airway resistance syndrome (UARS), and obstructive sleep apnea syndrome (OSAS)—that are often grouped under the heading of sleep-disordered breathing (SDB) constitutes the greatest number of sleep disorders seen by pulmonologists as well as general practitioners in the outpatient setting.1 Optimal management of SDB, as with all primary sleep disorders, is predicated on an understanding of underlying causes, accurate diagnosis, and the institution of appropriate treatment.

One treatment option that patients seeking a “cure” for OSAS may inquire about is surgery. In general, surgery for OSAS is not without risks, and is reserved for patients with severe OSAS who cannot tolerate using a CPAP device, and for whom other interventions are ineffective or unacceptable.

Check the online archives for more articles on SDB surgery.

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OSAS OVERVIEW AND PATHOGENESIS

OSAS is a common yet underrecognized disorder that affects approximately 4% of middle-aged adults and 20% to 50% of elderly persons.2,3 Of the approximately 75,000 patients seen annually in sleep disorder centers, roughly 75% are diagnosed with OSAS.4 Projections of the prevalence of OSAS in the United States range from 7 million to 18 million people.4 However, despite the prevalence of sleep apnea, the pathogenic mechanisms of this disorder remain incompletely understood, and the spectrum and severity of clinical presentations of OSAS are extremely variable.

Increased upper airway resistance and collapsibility in patients with OSAS can be the result of an anatomic compromise. Pharyngeal resistance during wakefulness is increased in patients with OSAS compared with normal individuals, and pharyngeal resistance correlates with the severity of OSAS.5 The pharynx of adults with OSAS collapses when experimentally exposed to subatmospheric pressure during wakefulness, whereas that of normal controls does not.6 The upper airway is anatomically smaller in patients with OSAS than in normal individuals, particularly at the retropalatal and retroglossal levels. Pharyngeal cross-sectional area correlates inversely with OSAS severity.7

OSAS has been associated with anatomic compromise resulting from neoplasia (benign or malignant), metabolic abnormalities, and traumatic compromise.6,7 Inflammatory disorders may cause diffuse enlargement of structure such as the tongue and pharyngeal lymphoid tissues (as in tonsillitis), resulting in a compromise of the airway.7 However, in the majority of patients with OSAS, no specific focus of upper airway pathology can be identified.

The association between obesity and OSAS is well recognized. Weight gain in patients with OSAS usually results in an increase in the severity of apnea.8 It has long been hypothesized, and later documented by MRI, that the region surrounding the collapsible segment of the pharynx in patients with OSAS has a greater fat load than does the same region in equally obese patients who do not have OSAS. This finding—in conjunction with an increase in airway resistance and a decrease in airway stability documented when applying lard-filled bags to the neck to simulate cervical fat accumulation—suggests that the effect of obesity on OSAS might be related to local parapharyngeal fat deposits.8,9 Histopathologic studies of uvulas excised during uvulopalatopharyngoplasty (UPPP) for OSAS have demonstrated higher amounts of both fat and muscle mass compared with those seen during normal postmortem studies.9

Many people who snore or have OSAS mouth-breathe during sleep. Although this has not been systematically investigated, increased nasal or nasopharyngeal resistance might explain it. The open-mouth posture unfavorably alters the pharyngeal airway by creating a relatively unstable passage. With the mouth open, the tongue and soft palate are exposed to atmospheric pressure. This releases the anterior part of the tongue, producing a dorsal motion of the belly of the genioglossus, and decreases the dimensions of the oropharyngeal lumen. The entire transmural pressure of the pharynx is exerted across the soft palate, moving it dorsally and narrowing further the oropharyngeal lumen.

Open-mouth posture further compromises the pharyngeal airway by diminishing the length of the axis of action of the genioglossus and, therefore, its efficacy in pulling the tongue forward out of the airway. Furthermore, the nasal mucosa, which is bypassed in mouth breathing, might have receptors that respond to airflow and serve as afferent stimuli for the neural regulatory mechanisms of respiration. Eliminating this afferent input to reflex arcs involving upper airway muscles could predispose to OSAS.

Clinical studies have confirmed that nasal obstruction exacerbates a tendency toward OSAS.7 The larynx—the other high-resistance structure in the upper airway—can be the site of OSAS when compromised by space-occupying lesions or abductor paralysis.

CLINICAL MANIFESTATIONS

The reduction of tonic upper airway dilating muscle activity caused by sleep is associated with reduced upper airway caliber and increased pharyngeal wall compliance.10 The mechanical corollary of decreased caliber is an increase in upper airway resistance.11 In addition to increased resistance, increased pharyngeal wall compliance during sleep in snorers is manifested by the occurrence of inspiratory flow limitation as flow plateaus during inspiration.

The combination of increased resistance and inspiratory flow limitation leads to an increased work of breathing, hypoventilation, and frequent arousals from sleep, and ensuing excessive daytime sleepiness. This is a clinical description of UARS.12

The ability of the ventilatory control system to compensate for added loads is essential for the preservation of chemoreceptor homeostasis. However, immediate compensation for added loads is compromised during non-rapid eye movement (NREM) sleep. Therefore, resistive loading results in decreased tidal volume and minute ventilation and, consequently, alveolar hypoventilation with subsequent elevation of arterial PaCO2.13 Furthermore, NREM sleep abolishes the ability of upper airway dilating muscles to respond to negative pressure.13

In summary, the failure of immediate load compensation results in hypoventilation and a subsequent increase in respiratory muscle activity. This may explain the noted paradox in heavy snorers who have nocturnal CO2 retention and increased inspiratory and expiratory muscle activity.14

NONSURGICAL MANAGEMENT

Nonsurgical approaches to the management of OSAS include behavioral modification, drug therapy, and use of mechanical devices. Behavioral modifications include avoidance of alcohol and sedative medications, alteration of sleep position, avoidance of sleep deprivation, and weight loss. Drug therapy for OSAS is of limited clinical value, with the exception of thyroxine replacement in patients with hypothyroidism.15

Nasal CPAP is the initial treatment of choice for OSAS in adults and can reduce mortality associated with OSAS.16 CPAP allows progressive restoration of airflow, as the pressure applied exceeds the airway opening pressure. Appropriate CPAP can resolve OSAS in many patients. CPAP works by pneumatically splinting the collapsible upper airway. Although effective, CPAP is uncomfortable or intolerable for some patients, and variable patient compliance remains a significant problem. Studies have found that up to 25% of patients discontinue CPAP therapy.17,18

SURGICAL MANAGEMENT

Upper-airway surgery for OSAS seeks to modify dysfunctional pharyngeal anatomy or bypass the pharynx entirely. Modifications of the pharynx can diminish the bulk of soft tissue structures that abut the air column, place these structures under tension, or alter their spatial interrelationships. Surgical procedures are designed to modify the retropalatal pharynx, the retrolingual pharynx, or both. Appropriate application of surgery may achieve cure in some patients without resorting to tracheostomy.19

For patients with OSAS, airway evaluation is critical when making the decision about whether surgery is appropriate. At the very least, preoperative evaluation should include a basic head and neck physical examination to evaluate for overt pathology. An upper airway examination will also provide insight into identifying patients with a greater risk of OSAS. For patients who are evaluated for surgery, endoscopy combined with cephalometrics is the most accepted method of identifying patients with retroglossal collapse and obstruction. Examination should be directed at assessing risk factors to direct the aggressiveness of surgical intervention.20

Tracheostomy: Tracheostomy was the initial surgical procedure performed for OSAS and may be effective in decreasing the morbidity and mortality of OSAS. Because tracheostomy bypasses the collapsible upper airway, it is a definitive surgical treatment for OSAS. This procedure, however, is associated with complications and significant emotional and physical morbidity. From the patient’s perspective, tracheostomy is often esthetically and socially undesirable. Nevertheless, tracheostomy remains an important surgical option in patients with severe OSAS who cannot tolerate CPAP, and for whom other interventions are ineffective or unacceptable.

In a retrospective study of 79 patients (aged 25 to 70 years) who underwent tracheostomy for OSAS,21 OSAS was eliminated by the procedure in all cases. Morbidity observed within the first year was primarily limited to granulation tissue, infection, and stoma revision. Fourteen deaths were identified. Average age at time of death was 62 years. Five deaths were cardiopulmonary related, four were from cancer, two were from postoperative complications of unrelated surgery, and one was from aspiration. Tracheostomy-related mortality included one postoperative myocardial infarction and one tracheal fistula. The investigators concluded that severe OSAS and its comorbid conditions are effectively treated in the long term with tracheostomy.

Uvulopalatopharyngoplasty: UPPP is currently the most commonly performed surgical procedure for the treatment of OSAS.22-24 UPPP enlarges the retropalatal upper airway by excising a portion of the posterior soft palate and uvula with trimming and reorientation of the tonsillar pillars. The tonsils, if present, are excised as well. Historically, UPPP has been considered effective in about 50% of patients with OSAS.23 These suboptimal results are due largely to unresolved obstruction of the upper airway in sites other than the retropalatal region. Preoperative screening studies are now used to identify patients in whom the retropalate is the primary site of obstruction and in whom UPPP is more likely to be effective. Significant weight gain after UPPP may also contribute to suboptimal results.

Laser-Assisted Uvulopalatoplasty (LAUP): LAUP was initially proposed as an alternative method to treat habitual snoring. Throughout the years, the indications for LAUP have broadened; however, it has also remained an area of controversy.25

LAUP is performed under local anesthesia on an outpatient basis. LAUP is a multistaged procedure that involves CO2-laser excision of the uvula and a small portion of the soft palate at each stage. The goal of staging is to excise the least amount of palatal tissue needed to reduce snoring effectively while reducing the risk of developing pharyngeal insufficiency. LAUP has been reported to reduce morbidity, such as pain and bleeding, as compared to traditional UPPP.26 LAUP is also less expensive for payors and requires less time off from work for patients.26

In a prospective, nonrandomized, nonblinded assessment of outcomes after LAUP in 59 patients suffering from benign habitual snoring and/or mild OSAS,27 91.5% of the patients with habitual snoring reported significant short-term improvement based on post-treatment questionnaires, whereas 79.7% reported long-term subjective improvement. Nineteen of 25 patients (76%) with mild OSAS reported significant improvement of snoring based on post-treatment questionnaires. According to postoperative polysomnography, the apnea-hypopnea index (AHI) worsened in only 2% of patients, whereas 60% showed reduction of the AHI to £5. Eight patients (32%) showed little or no improvement in AHI postoperatively. The investigators concluded that LAUP is a safe and cost-effective procedure for the treatment of many cases of habitual snoring and mild OSAS when preceded by careful selection of surgical candidates.

OTHER CONVENTIONAL SURGICAL PROCEDURES

Additional surgical procedures used in selected patients with severe OSAS, all of which are designed to enlarge the retropalatal airway, include uvulopalatopharyngoglossoplasty; linguoplasty; laser midline glossectomy; inferior sagittal mandibular osteotomy and genioglossal advancement with hyoid myotomy and suspension (GAHM); and maxillomandibular osteotomy (MMO). Laser midline glossectomy involves laser extirpation of a portion of the posterior midline tongue. Laser lingual tonsillectomy, reduction of the aryepiglottic folds, and partial epiglottectomy may be performed in selected patients. Linguoplasty involves additional extirpation of posterior and lateral tongue tissue. In GAHM, the glenoid tubercle of the mandible (the anterior attachment of the tongue) is advanced by a limited osteotomy of the mandible. MMO enlarges the retrolingual airway maximally and provides some enlargement of the retropalatal airway as well. The major drawback of MMO is that it is a complex procedure limited to only a few institutions, and is associated with significant postoperative morbidity.

Radio-Frequency Tissue Ablation (Somnoplasty): A relatively new surgical procedure for OSAS is radio-frequency tissue ablation (RFTA). This outpatient procedure—which the US Food and Drug Administration (FDA) approved in November 1998—uses controlled, low-power radio-frequency energy to create one or several submucosal volumetric lesions. Over a period of 6 to 8 weeks, the lesions are naturally resorbed, reducing tissue volume and stiffening remaining tissue in the desired area.28 RFTA is still viewed as a new procedure, and relatively little published data on the procedure are available. It is marketed under the registered trademark Somnoplasty by Gyrus ENT, LLC, Bartlett, Tenn.

Tongue Suspension Procedure (Repose): The FDA approved a different surgical system designed to treat OSAS in February 1998. Known as genioglossus advancement or tongue suspension procedure, it is intended to keep the tongue from falling back over the airway during sleep. A small screw inserted into the lower jawbone and stitches below the tongue keep the tongue from blocking the airway. The tongue suspension procedure usually is performed in conjunction with other procedures. InfluENT Medical of Concord, NH, markets the procedure as the Repose® device.

In a multicenter, nonrandomized, open enrollment trial,29 the Repose device was used to treat tongue obstruction in 39 patients with snoring and/or OSAS; 23 patients completed 1 month of follow-up, and 19 completed 2 months of follow-up. In the OSAS group, activity level, energy, and sleepiness improved. Two-month outcomes were not as great. Fewer changes were observed in snorers than in OSAS patients. Complications occurred in 18% of patients, and included sialadenitis, gastrointestinal bleeding, and dehydration. The investigators concluded that the tongue suspension procedure may change subjective outcomes, but the improvement is incomplete. They recommended further evaluation to demonstrate effectiveness. To date, no studies on the long-term success of the tongue suspension procedure are available.

SUMMARY

The consequences of primary sleep disorders such as OSAS can be significant for those affected as well as bed partners and family members. Although many patients try to self-manage their symptoms, most will eventually seek treatment if symptoms are unrelenting and/or progressive. Optimal management depends on accurate diagnosis, which includes identification of possible triggers, and institution of the appropriate therapeutic modalities. Surgery offers a chance of cure for patients with severe OSAS who cannot tolerate CPAP. However, the key to positive outcomes with surgery appears to be linked to appropriate patient selection, versatility in varied surgical approaches, and willingness to utilize more than one procedure when necessary.


John D. Zoidis, MD, is a contributing writer for Sleep Review. Contact him at [email protected]

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