Chapter 42 A minimally invasive technique for tongue base stabilization
Obstructive sleep apnea syndrome (OSAS) results from a complex scenario initiated with airway collapse and obstruction, loss of compensatory wake and sleep reflexes, increased ventilatory effort, arousal, hypoventilation, and asphyxia during sleep. In adults, a structurally small upper airway may be a primary contributing factor. Enlarging this airway may prevent the cascade into sleep apnea and snoring.
The etiology of the small upper airway in adults may include an abnormal craniofacial structure, excessive soft tissue for the available space, and obesity. These abnormalities are not isolated to the upper pharynx and involve multiple upper airway segments. It has long been speculated that failure to treat these other areas of obstruction and collapse has been a cause of failure of isolated treatment with palatal surgery such as uvulopalatopharyngoplasty (UPPP). Hypopharyngeal levels of obstruction may include the structures of the tongue base, lateral hypopharynygeal walls, lingual tonsils and supraglottis. To treat these areas multiple procedures have been described. Each has varying levels of potential effectiveness and risks of morbidity. For surgeons the dilemma has been to adequately treat these observed sites of obstruction with the least morbidity.
Appropriate surgical treatment options require an understanding of the underlying airway abnormality. The pharyngeal wall is the posterior tongue. Its position stabilizes the hypopharynx, the lateral pharyngeal walls, and even the epipharynx. The tongue which in most mammals is an oral structure, in humans is unique and is also a pharyngeal structure. The human pharynx is potentially collapsible and is unique in requiring these muscles to maintain patency during sleep. The genioglossus and other tongue musculature do not just sustain speech and swallowing, but are ventilatory muscles supporting the airway during sleep.
Increasing stability of the tongue and lower pharynx may stabilize the airway during sleep and may effectively treat sleep-disordered breathing. Surgical procedures stiffen the airway, change shape, or increase volume of the airway. Procedures directed at the anterior wall of the pharynx include posterior glossectomy and advancement and suspension procedures. Skeletal osteotomies of the mandible may increase volume of the airway by advancing tissue or may stiffen by traction, muscle tension and stiffening. Glossectomy or tissue volume reduction procedures decrease tongue volume and proportionally increase airway size.
Most of these procedures are not widely applied. The absolute effect of any single procedure is variable. This combined with the perceived or actual morbidity discourages use to a relatively small population. The goal of surgery of the lower pharynx is to improve effectiveness, better define the surgical population, and decrease surgi-cal morbidity. The procedure of tongue base suspension is an option to treat lower pharyngeal obstruction and reduce morbidity compared to alternative procedures.
Airway collapse during sleep is both dynamic and passive. Dynamic collapse occurs during inspiration. Passive collapse occurs during expiration. Both are the result of a combination of applied forces that collapse and dilate the airway. In a structurally small airway during sleep, when dilating forces that stabilize the airway are greater than the collapsing forces, the airway is obstructed.
Obstruction during sleep is the result of a complex cascade. During inspiration, upper (pharynx) and lower (chest wall and diaphragm) airway muscles are activated. The lower airway muscles create a negative intraluminal force balanced by upper airway muscles that stiffen and dilate the airway. Increases in negative airway pressure or loss of muscle dilation will obstruct the airway. In sleep-disordered breathing both occur. Increased upper airway resistance leads to more negative intraluminal pressure and activation of upper airway dilator muscles is delayed or decreased. During expiration, positive pressure forces dilate the airway, and upper airway muscle tone is reduced. If the balance is unfavorable and the effects of tissue mass are not compensated, collapse and obstruction occur.
The tipping point for apnea is poorly understood, but is likely initiated by passive expiratory collapse. It is this collapse that triggers the dynamic events during inspiration. Without passive airway collapse, the cascade of progressive inspiratory flow limitation, increased negative luminal pressure and increased upper airway resistance may be aborted. If adequate airway size is maintained during expiration, inspiratory obstruction is prevented.
Since during expiration the largest decreases in airway size occur in the hypopharynx, treatment of this segment may be critical for most if not all individuals with sleep-disordered breathing. The tongue suspension procedure was conceived as a means of providing an extraluminal dilating force to the lower pharyngeal airway in contrast to nasal Continuous Positive Airway Pressure (CPAP) which is an intraluminal dilating force. This is accomplished by passing a submucosal suture into the posterior midline tongue. The suture prevents passive collapse while not interfering with anterior and superior tongue movements which are involved with swallowing and speech. Placement is directed towards the level of the foramen cecum (Fig. 42.1).
The procedure is performed under general or local anesthesia. Local anesthesia requires an external approach. Technically, the procedure may be combined with other pharyngeal procedures. Due to tethering and edema of the tongue, this procedure may augment the pain and dysphagia of other procedures. Benefits of combined procedures must be balanced with risks of increased perioperative morbidity and increased side effects. Using the procedure as an isolated intervention is recommended until clinical experience is adequate. Since a foreign body is placed, preoperative broad-spectrum antibiotics to cover and intraoral closed wound are given Decadron 10 mg reduces tongue pain and swelling and postoperative nausea. Intubation may be oral or nasal depending on the surgeon’s experience and preference. With oral intubation, care must be taken to protect the endotracheal tube from damage or displacement. The oral cavity is prepped with antibacterial solutions such as chlorhexidine oral solution. Exposure is facilitated by using a shoulder roll. Local anesthesia is infused into the anterior midline floor of mouth anterior to Wharton’s ducts.
When performing the intraoral approach, an intraoral incision is made posterior to the salivary papillae (Fig. 42.2). The incision should be generous. An excessively long linear incision is easily closed with excellent healing. An incision too small for the device may result in mucosal tearing that may damage the papillae and create an intraoral scar. If an external incision is used an incision is made 1cm posterior to the gnathion in a convenient skin crease or shadow.
Fig. 42.2 Placement of intraoral incision is shown. The midline incision should be generous in length to avoid trauma and possible tearing of mucosa. Alternatively, an extraoral approach may be performed (not shown).
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