Multilevel Pharyngeal Surgery for Obstructive Sleep Apnea

1

Introduction

Obstructive sleep apnea (OSA) is a common sleep disorder. It is characterized by repetitive apneas and hypopneas during sleep. These events are due to partial or complete collapse of the upper airway, resulting in decreased oxygenation and sympathetic overdrive. Frequent arousals occur, causing sleep fragmentation, which leads to excessive daytime sleepiness, morning headaches, poor concentration, memory loss, frustration, depression, and even marital discord. The mechanism of upper airway collapse in OSA is usually multifactorial. Many authors concur that most patients with moderate and severe OSA are likely to have multilevel obstruction involving the palate, the lateral pharyngeal walls, and/or the base of tongue. Nasoendoscopic examination of the patient's anatomy is crucial. Inspection is performed of the nasal passage, the sinus turbinates, the nasal septum, and the presence of adenoids; the retropalatal space is important; and the lateral pharyngeal walls may be thick and/or bulky; the retroglossal space may be narrow as well. Mueller maneuver may still be used and grades airway collapse at three levels, namely the velopharynx, lateral pharyngeal wall, and the base of tongue. There are surgical procedures that can address these various anatomic sites of collapse in these patients. The lateral pharyngeal wall collapse can also be dealt with by creating tension in the lateral walls by the lateral pharyngoplasty or the expansion sphincter pharyngoplasty. Other pharyngeal palatoplasty techniques include the traditional uvulopalatopharyngoplasty (UPPP), the Z-plasty, or the transpalatal advancement pharyngoplasty; tongue base procedures also include a midline glossectomy, hyoid suspension, lingual tonsillectomy, genioglossus advancement, tongue suspension sling suture, robotic tongue base surgery, and the hypoglossal nerve stimulation.

The site of obstruction is less important when the modality of therapy is a tracheostomy or nasal continuous positive airway pressure (CPAP), which indiscriminately overcomes all collapsible airway segments much like a “pneumatic splint.” When upper airway surgery is contemplated, it is critical to tailor the approach according to the site of obstruction noted preoperatively, and for this drug-induced sleep endoscopy (DISE) may be used in certain circumstances. The type of surgery employed would depend on the site of anatomic collapse, whether the palatal, lateral wall, and/or tongue base collapse.

A staged approach to the upper airway reconstruction is acceptable, and even endorsed by the American Sleep Disorders Association. When multilevel obstruction is present, the chances of surgical success may be improved by addressing multiple anatomic sites at a single surgical sitting.

The initial staged approach was described by Fujita, when he introduced the UPPP for OSA. He recognized that the upper airway may collapse at multiple levels; hence he also described the laser midline glossectomy for patients who failed UPPP and who were diagnosed as having retrolingual obstruction. It was Riley et al. who first advocated simultaneous multilevel pharyngeal surgery for patients with multilevel obstruction. They showed promising success with minimal complications. Many authors have reported minimal complications with one-stage multilevel pharyngeal surgery (including nasal surgery, if required) for patients with OSA.

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Surgical Planning (Pang–Woodson Surgical Protocol)

Based on basic physics and the pathophysiologic basis of airflow dynamics, the proper assessment of the nasal cavity and passage is of essence. In addition, the upper airway in the nose itself represents over 70% of the entire airway tract resistance, from the nasal cavity to the minute alveoli.

During inspiration, negative pressure is created within the intrapleural space (e.g. −8 cm H ₂ O) to distend the alveoli and to suck in or inhale air from the atmosphere into the lungs for gaseous exchange and oxygenation of the blood. This act of inhalation exerts a negative pressure on the entire upper airway, including the hypopharyngeal, retroglossal, and retropalatal space. Hypothetically, if there were any form of upper airway blockage within the nasal passage (e.g. a deviated nasal septum, enlarged swollen turbinates, nasal polyps, etc.), the lungs would have to work “harder” to create a “more negative pressure” (e.g. −30 cm H ₂ O) to inhale air from the atmosphere; this would ultimately result in a greater negative pressure on the hypopharyngeal, retroglossal, and retropalatal space, potentially leading to collapse and obstruction of the hypopharyngeal upper airway. It is also important to understand that without any form of obstruction in the nose, the airflow into the lungs through the nose would be laminar; however, with nasal blockage, there would be turbulent airflow within the nasal cavity and passage, resulting in higher nasal resistance, poorer nasal breathing, and snoring with vibration of the palate (the first site of contact from the turbulent airflow). Therefore although surgical correction of anatomic obstruction of the nasal passage alone does not cure obstructive sleep apnea, it may still significantly decrease the negative pressure within the pharynx.