1
Goals and Considerations
Multiple mechanisms underlie upper airway obstruction in obstructive sleep apnea (OSA). Although a small upper airway size is fundamental to OSA, muscle tone, tissue factors, lung volume, loop gain, and arousal threshold are important additional determinants. It is therefore not surprising that treatments that aim to enlarge or stabilize the upper airway such as sleep surgery, oral appliance therapy, hypoglossal neurostimulation, positional therapy, and weight loss may not fully normalize the respiratory parameters of OSA. Even positive airway pressure (PAP), which has high efficacy for treating the respiratory parameters, does not normalize breathing in a subset of patients and is often not accepted or tolerated, thus resulting in lower clinical effectiveness. Treatment for OSA should be similar to that of most chronic diseases and result in sufficient reduction of medical risk factors and improvement in quality of life. Multimodality therapy may be needed for some patients and is appropriate.
The goals of surgery are reduction of risk and improvement in quality of life via airway enlargement and/or stabilization. The Apnea/Hypopnea Index (AHI) correlates with risk for morbidity and mortality when elevated to levels >20 events per hour and more so for AHI >30 events/hour. For surgical treatment, high-level studies show AHI reduction, and observational studies demonstrate reduction of mortality and cardiovascular morbidity. Multiple studies show improved quality of life with surgery as well, usually with AHI reduction but not normalization. For this reason, a common goal for surgery is AHI reduction below 20 events/hour with a 50% or more reduction from baseline and concurrent symptomatic improvement.
Multilevel surgery is commonly utilized for OSA treatment, with the assumption that multiple obstructive or collapsible structures need treatment for adequate response. Indeed, multilevel collapse has been shown using cross-sectional imaging and during sleep endoscopy. The unanswered question is not which structures appear obstructive or collapsible, but which truly need treatment to improve the patient’s status with the least morbidity. Some patients may, in fact, need multiple structures and levels addressed, but many may not when newer, advanced palatopharyngoplasty techniques are used. Another argument for performing less surgery is the “AHI floor” for most upper airway surgery publications. The mean AHI in most surgical publications is in the teens, including the author’s, whether multilevel surgery or only advanced palatopharyngoplasty is employed.
Finally, and most importantly, one must incorporate patient preferences, expectations, and goals. Patients seek improvement in quality of life and reduction of medical risk, if present. Snoring is a major factor for most OSA patients. They are also interested in undergoing the least surgery, not the most, and thus may prefer having palatopharyngoplasty alone, if possible.
2
Clinical Evaluation for Surgery
For surgical treatment of the upper and lower pharynx, anatomic analysis is used for procedure selection. However, staging systems for assessment of the awake patient in the clinic are limited in their utility. Patients are most often assessed for size of tonsils, adenoids, palatal morphology, tongue position, tongue base, and jaw size using direct and fiber-optic visualization. Some use supine end-expiration to reduce the effect of upper airway dilator muscles on pharyngeal morphology.
Simple descriptive systems are used to categorize the upper airway that include relative tonsil size, tongue position, and pharyngeal shape. Currently, our systems lack three-dimensional features, precise delineation of the soft palatal morphology, quantitative volumetric, or cross-sectional measurements. Furthermore, descriptors are for the “contents of the box,” often without relation to the skeletal framework or tissue composition such as fat. Thus we can have two patients with the same relative tongue position and tonsil size, both having “palatal redundancy” or “elongation,” but they may have very different body mass indexes (BMIs) and intermolar widths (measure of maxillary narrowing). The contribution of fat deposits, skeletal morphology, and tissue biomechanics may result in different outcomes for the same surgical procedure. As such, the utility of current staging systems is limited. For example, patients with large tonsils and relatively normal tongues would have a high rate of successful AHI outcome with tonsillectomy and classic uvulopalatopharyngoplasty (UPPP), whereas those with large tongues (high tongue position) and small tonsils are much less likely to succeed with the same approach and have been recommended a multilevel approach, including tongue base procedures.
3
Drug-Induced Sleep Endoscopy
Drug-induced sleep endoscopy (DISE) is also used for advanced surgical planning, with dynamic visualization and identification of collapsible structures and patterns. Using DISE, surgeons have modified their treatment plan for palatal, tongue base, and laryngeal loci of obstruction. DISE, however, is not natural sleep. There are considerable effects of the drugs used in DISE on the brain and upper airway tone, and rapid eye movement sleep is not present with DISE. Collapse also varies with the depth of sedation and duration of DISE.
Complete circumferential collapse of the velopharyngeal airway was identified as a negative predictor in some studies for successful AHI outcome using multilevel surgery and for one hypoglossal neurostimulation system. However, in most other cases, the precise application of collapse patterns in DISE is also not known. Velopharyngeal anatomy and physiology, lateral collapse, and the degree of collapse have not been well studied with respect to the outcome of specific surgical interventions. In the author’s experience, tongue base collapse in DISE does not appear to always require treatment. When lateral pharyngoplasty (LP) techniques are used alone, even in cases of multilevel collapse including the tongue base, the AHI outcome is not different from that in the case of only upper pharyngeal collapse on DISE ( Fig. 16.1 ).
