Surgical Evaluation in Obstructive Sleep Apnea: Climbing the Steep Part of the Learning Curve.

Abstract

Many physiologic factors contribute to obstructive sleep apnea (OSA), including pharyngeal anatomy, dilator muscle activation, lung volumes, arousal threshold, and ventilatory control.1 Although it may be possible to examine the relative importance of these factors in researchsettings, there are no clinically available tests that can be used to treat patientsaccordingly (forexample,usingasedativehypnoticagent for those patientswith a low arousal threshold). Surgery is an anatomical treatment, and Woodson2 summarizes the evidence regarding identificationof thepatternofobstructionand surgical treatment of OSA. The first relevant issue is how to predict outcomes of palate surgerywith tonsillectomy.Higher-level evidence fromcohort studies indicates that Friedman stage shows the clearest association with outcomes after uvulopalatopharyngoplasty (UPPP). There are conflicting studies about the relative value of endoscopy and theMuellermaneuver duringwakefulness, but Iwanaga et al3 and Hessel and Vries4 showed that druginduced sleep endoscopy (DISE) is also associated with UPPP outcomes. Comparison of findings from evaluation methods has not been undertaken as extensively for alternative palate procedures. This is important because some of these procedures (expansion sphincter pharyngoplasty, lateral pharyngoplasty) have demonstrated better outcomes than UPPP in randomizedtrials andbecauseonly 10%ofOSAcasesareFriedman stage 1. The second key issue is how to select alternative or adjunctive treatments and whether the findings predict outcomes.Mostof the literature regardingevaluationmethodshas focused on findings that are associated with worse outcomes, identifying mandible position (eg, SNB [sellanasion-B point] angle on the lateral cephalogram) and body mass index as factors associated with outcomes for all hypopharyngeal or retroglossal procedures.DISEmay identify specific structures (VOTE classification) that contribute specifically to obstruction, but no studies have prospectively used DISE to select procedures. However, there are cohort studies showing that specificDISE findings are associatedwithworse outcomes after surgery,5,6 mandibular repositioning appliance use, or hypoglossal nerve stimulation. In my own practice, I use Friedman stage to select patients for isolated palate surgery and complement this with awake endoscopy for a more detailed evaluation of the pharynx. Insteadof usingDISE as a routine separate evaluation for all patients, as is done in some European centers, I prefer to use it as a stand-alone evaluation in approximately 20%ofpatients where I believe that it can change recommendations, such as those with previous surgery or an especially unclear pattern of obstruction. In some cases, I will perform DISE at the timeof a procedure to guide the selectionof a specific palate surgery technique or the extent of tongue base tissue resection, but this is based on personal experience rather than anything approaching a randomized trial. Woodson2 correctly describes that the surgical evaluation of OSA surgery remains in its infancy. Current techniques that evaluate physical anatomymaybe combinedwith physiologic measures suchaspharyngeal critical closingpressure.Asnovel technologies and techniques for treatment become available, so too will major advances in sleep surgery with larger, controlled, and prospective studies of evaluation methods. Both areashaveprovenessential inourquest toselectproceduresand enable targeted, effective, and predictable outcomes.