Pang-Rotenberg Sign Snoring Surgery Prognosticator: A Prospective Clinical Trial of 153 Patients

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1 The Laryngoscope VC 2015 The American Laryngological, Rhinological and Otological Society, Inc. Pang-Rotenberg Sign Snoring Surgery Prognosticator: A Prospective Clinical Trial of 153 Patients Kenny P. Pang, FRCSEd, FRCSI(OTO); Srivinas Kishore, MBBS, MS; Joseph Chung Chun Kit, FRCS; Edward B. Pang; Yiong Huak Chan, PhD; Siow Jin Keat, MD, FRCS; Brian Rotenberg, MD, FRCS Objectives/Hypothesis: To illustrate the reliability of the Pang-Rotenberg (PR) sign as a prognosticator of snoring surgery. Our hypothesis was that patients who are PR-positive have better snoring reduction scores and outcomes than PRnegative patients after nose and palate surgery. Study Design: A multicenter prospective series of 153 patients with snoring. Methods: All patients graded the snoring intensity on a visual analog scale (VAS). All 137 patients enrolled had both the nose surgery and palate surgery. The control group consisted of 16 patients who underwent nasal surgery alone. Results: There were 122 men and 15 women, the mean age was 44.6 years old, and mean body mass index was There were 15 simple snorers and 122 obstructive sleep apnea patients. Patients who were PR-positive showed significantly better postoperative snoring VAS reduction (from 9.04 to 1.02) compared to those patients who were PR-negative (from 8.91 to 3.14) (P <.001). The mean follow-up time was 7.4 months. The control group had poor snoring VAS reduction from 9.21 to After adjusting for covariates that influence the snoring VAS change due to surgery, we found that PR-negative patients achieved an average of 5.78 improvement in snoring VAS, whereas PR-positive patients achieved an average of 8.02 improvement in snoring VAS (P <.001). Conclusions: The PR sign is a reliable prognosticator of snoring reduction, after combined nose and palate surgery, for patients with troublesome snoring. Key Words: Pang-Rotenberg sign, snoring reduction, obstructive sleep apnea. Level of Evidence: 2b Laryngoscope, 126: , 2016 INTRODUCTION Snoring is considered a social nuisance and an objectionable social problem. It is caused by the vibration of the structures in the oral cavity and oropharynx, namely the soft palate, uvula, tonsils, base of tongue, epiglottis, and pharyngeal walls. Obstructive sleep apnea (OSA) is a common sleep disorder. Young et al. studied 602 state employees with attended overnight polysomnography and found that the incidence of sleepdisordered breathing (SDB) was 24% in men and 9% in women. 1 Most of these patients are undiagnosed. It is estimated that up to 93% of females and 82% of males with moderate to severe OSA remain undiagnosed. 2 From the Department of Otolaryngology (K.P.P, E.B.P.), Asia Sleep Centre, Paragon Medical, Singapore; Department of Otolaryngology (S.K.), Nova Specialty Hospital, Hyderabad, India; Department of Otolaryngology (J.C.C.K.), Tuen Mun Hospital, Hong Kong; Biostatistics Unit (Y.H.C.), Dean s Office School of Medicine, National University, Singapore; Department of Otolaryngology (S.J.K.), Tan Tock Seng Hospital, Singapore; and the Department of Otolaryngology Head and Neck Surgery (B.R.), Western University, London, Ontario, Canada. Editor s Note: This Manuscript was accepted for publication April 20, The authors have no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Kenny P. Pang, Department of Otolaryngology, Asia Sleep Centre, Paragon Medical, 290 Orchard Road, Unit 18-04, Singapore drkpang@gmail.com DOI: /lary It is well known that most snoring occurs when the patient subconsciously opens the mouth, which causes vibration of the palate (palatal flutter), resulting in the loud snore. By opening the mouth, the temporomandibular joint rotates inferiorly and posteriorly, narrowing the retroglossal space further, which results in worsening OSA. Ideally, the mouth should be closed and nasal breathing encouraged; however, this is often not possible, especially if the patient has some form of nasal obstruction. Hence, surgical intervention to open up the nasal passage for nasal breathing and mouth closure is crucial. However, intuitively, there are some patients who are habitual mouth breathers and may continue to breathe through the oral route despite having a patent nasal passage. Many snoring/osa surgical techniques have been introduced to reduce, trim, or stiffen the palate to reduce the snoring; however, conceptually, treating the nose alone would produce dismal surgical results, 3 7 as with treating the palate alone would not allow the patient to take on nasal breathing with reliable, consistent, and complete mouth closure. 6,7 We present a new clinical sign (Pang-Rotenberg [PR] sign) to prognosticate and aid in the preoperative patient counseling for snoring surgery in this group of patients with simple snoring and OSA. MATERIALS AND METHODS This was a nonrandomized, prospective, multicenter clinical trial of consecutive patients seen in the ear, nose, and throat

2 office for complaints of bothersome snoring who met the selection criteria and underwent multilevel surgery of the airway. Patients were recruited from four clinical centers, including Singapore, Canada, India, and Hong Kong. All patients underwent a comprehensive clinical assessment including a thorough physical examination, nasoendoscopy, and overnight polysomnography (PSG). For patients who had overnight PSG, apnea was defined as a >90% reduction in airflow persisting for >10 seconds, relative to basal amplitude. An hypopnea was defined as a more than 50% decrease in airflow amplitude relative to the baseline and associated with >3% desaturation of oxygen or arousal >10 seconds. Patients completed the Epworth Sleepiness Scale (ESS) and a visual analog scale (VAS) for snoring before and after surgery. The sleep partner completed a similar scale for snoring. The patient also completed a VAS for pain on postoperative days 1, 3, 7, and 14. Examination included height, weight, neck circumference, body mass index (BMI), and blood pressure, and an endoscopic assessment of the nasal cavity, posterior nasal space, oropharyngeal area, soft palatal redundancy, uvula size and thickness, tonsillar size, and Mallampati grade. Flexible nasoendoscopy was performed for all patients, and collapse during a Mueller s maneuver was graded for the soft palate, lateral pharyngeal walls, and base of tongue on a fivepoint scale. 8 Outcome measures included subjective improvement in snoring based on the VAS and improvement in sleepiness as indicated by the ESS. Objective changes were presented by the polysomnographic findings. Reduction of at least 50% of the preprocedure apnea-hypopnea index (AHI) and postprocedure AHI below 20 was deemed a success. Surgical Intervention All patients enrolled had both nasal and palatal surgery performed at the same sitting. Hence, all patients had some form of nasal surgery done, either in the form of a septoplasty, turbinate reduction, and/or turbinoplasty. Palate surgery was performed based on clinical examination, according to the Pang- Woodson protocol, 9 either in the form of Fairbank s uvulopalatopharyngoplasty, anterior palatoplasty, Z-plasty, uvulopalatal flap, and/or expansion sphincter pharyngoplasty. During the course of this prospective trial, 16 patients self-selected themselves; these patients had declined palate surgery for various reasons (fear of the pain and/or work commitment) and became the control group who only had nasal surgery. The inclusion criteria was age >18 years, BMI <33, tonsil size grade 1 to 4, all Mallampati grades, minimal base of tongue collapse (<25%) as seen on Muller s maneuver, mainly retropalatal collapse noted, simple snorers (AHI <5), patients with OSA, and with no previous nose, mouth, and throat surgery. The study protocol and methodology were reviewed and approved by the hospital ethics committee/institutional review board. Statistical Analysis The sample characteristics were reported in mean (standard deviation) for continuous variables and number (percent) for categorical variables. Within each individual group, statistical analysis was also performed to evaluate the statistical significance of each group s snoring reduction. Two groups, PR sign-positive and PR sign-negative, were compared at baseline of enrollment to examine comparability in terms of clinical and demographic variables. Within each individual group, statistical analysis was also performed to evaluate the statistical significance of each group s postoperative scores using a mixed model. SPSS 21.0 (IBM, Armonk, NY) was used, with statistical significance set at P <.05. The two groups were also compared after surgery to check the difference in snore improvement measured as snore score and ESS score. A multivariable general linear model was conducted to evaluate the effect of PR sign status on snoring improvement while controlling for confounders such as age, gender, race, BMI, and preoperative snore extent. PR Sign Patients were instructed to voluntarily open the mouth slightly and to gently produce a palatal flutter sound on inhalation through the mouth (mouth breathing/inhalation with palatal flutter) (note: this is not a gargle, as gargling noises are made on exhalation) and attempt to repeat this palatal flutter again with the mouth/lips closed. The PR sign is positive when the patient is able to create the palatal flutter noise with the mouth slightly open (mouth breathing with palatal flutter) but is unable to create the same palatal flutter noise with the mouth closed (on gentle nasal inhalation with mouth closed, not strong nasal snorting). The PR sign is negative when the patient can create the palatal flutter noise with the mouth slightly open (mouth breathing with palatal flutter) and is able to create a throat/ nose noise even when the mouth is completely closed. These would be patients who are PR-negative. On further nasoendoscopic evaluation, those patients who are able to create this throat/nose noise have vibrations of the salpingopharyngeus folds in the nasopharyngeal and velopharyngeal junction. RESULTS There were 122 men and 15 women, the mean age was 44.6 years old (range, years), and the mean BMI was 26.1 (range, ). All patients had preoperative PSG; however, only patients with AHI >5 had a postoperative PSG repeated. There were 15 snorers and 122 patients with OSA. There were a total of 99 patients (72.3%) who were found to be PR-positive and 38 patients (27.7%) who were PR-negative. Intragroup analysis showed that patients who were PR-positive had achieved a snoring VAS reduction (adjusted for age, gender, race, OSA severity, BMI, and presurgery scores) from 9.04 to 1.02 (P <.001) and ESS improvement from to 2.68 (P <.001) (Table I). Patients who were PR-negative had achieved a snoring VAS reduction from 8.92 to 3.14 (P <.001) and ESS improvement from to 5.61 (P <.001). The PR-positive group showed larger improvement (adjusted for age, gender, race, OSA severity, BMI, and presurgery scores) in both snoring VAS and ESS than the PR-negative group. The comparisons were statistically significant (P <.001) (Table II) compared to those patients who were PR-negative (from 8.91 to 3.14) (P <.001) (Table II). Sixteen patients in the control group (who only had nasal surgery) had poor snoring VAS reduction postoperatively from 9.21 to The ESS improved from preoperative (group 1)/12.75 (group 2) to postoperative 8.86 (group 1)/7.14 (group 2), respectively (P <.001). The mean follow-up time was 7.4 months. The preoperative mean AHI for the PR-positive group was 29.6, compared to the preoperative mean AHI 261

3 TABLE I. Comparisons Between PR 1 and PR 2 Patients Pre- and Postoperation. Characteristic PR 2,n5 38 PR 1,n5 99 P Preoperative data, mean (SD) Age, yr 43 (11.59) (10.66).163 BMI 27.5 (2.76) (3.43).065 Preoperative Epworth (4.15) (3.27).119 Preoperative snore score 8.92 (1.16) 9.04 (1.41).639 Preoperative LSAT (9.91) (9.49).882 Preoperative AHI (23.13) (24.70).329 Gender, No. (%) Male 34 (88.90) 88 (88.90) Female 4 (11.10) 11 (11.10) 1 Race, No. (%) Chinese 19 (50.00) 73 (73.30) Indian 9 (22.20) 21 (21.20) Others 10 (27.80) 5 (5.10).001 Postoperative data, mean (SD) Postoperative Epworth 5.61 (3.09) 2.68 (2.04) <.001 Epworth improvement 7.14 (2.99) 8.86 (3.18).006 Postoperative snore score 3.14 (1.64) 1.02 (1.15) <.001 Snore improvement 5.78 (1.48) 8.02 (1.91) <.001 AHI 5 apnea-hypopnea index; BMI 5 body mass index; LSAT 5 lowest oxygen saturation; PR 5 Pang-Rotenberg; SD 5 standard deviation. for the PR-negative group, which was The preoperative mean lowest oxygen saturation (LSAT) for the PRpositive group was 80.5%; the preoperative mean LSAT for the PR- negative group was 82.4%. There was a decrease in the preoperative to the postoperative BMI for both the PR-positive and PR-negative groups. There was a slightly larger decrease of BMI in the PR-positive group from 27.5 to 24.7, compared to the PR-negative group (from BMI 26.3 to 24.1), which was not statistically significant. The prevalence of hypertension in the entire group was 22.6% (31 out of 137 patients), whereas the prevalence of diabetes mellitus was 7.3% (10 out of 137 patients). Nine out of 137 patients (6.6%) had a history of asthma. Of interest, we noted that males had a better prognosis in terms of snoring reduction compared to females 1.41 times more change in snoring reduction in the males (P <.001). Table III shows that Chinese and Indians (compared to the other races) had a better prognosis in terms of snoring and ESS reduction. Their BMI was negatively associated with the final snoring VAS, meaning that the higher the BMI, the lesser the change in snoring VAS postsurgery (P 5.02). There was also statistical evidence that the higher the preoperative snoring VAS score, the greater the reduction in VAS score postsurgery (P <.001). After adjusting for covariates that influence the snoring VAS change due to surgery, we found that PR-negative patients achieved an average of 5.78 improvement in snoring VAS, whereas PR-positive patients achieved an average of 8.02 improvement in snoring VAS (P <.001). There was clinically and statistically significant reduction in snoring VAS scores in both PR groups, although the reduction was more in the PR-positive group. In terms of OSA severity, the study did not find any correlation or influence of AHI on the snoring reduction outcome and/or the PR status of patients (p 5.329, Table I). There are no postoperative polysomnographic data available; the preoperative polysomnogram was used to stratify the patients into OSA severity groups to evaluate if they made a difference to the final outcome. Pain was the most common complaint. The amount of pain was noted to be of higher intensity in patients who had a concurrent tonsillectomy done. Almost all of the patients revealed that throat pain resolved between the 10th and 13th day postsurgery. DISCUSSION Snoring is caused by a vibration of the structures of the oral cavity/oropharynx the soft palate, uvula, tonsils, base of tongue, epiglottis, and pharyngeal walls. Partial or complete upper airway obstruction during sleep can be due to excessive soft tissue or abnormal facial skeletal framework. Patients with adenotonsillar hypertrophy have a crowded upper airway with very little space for airflow, whereas obese patients frequently have soft palate redundancy, huge tongues, and thick lateral pharyngeal walls. It is the vibration of these soft TABLE II. Inter- and Intragroup Comparisons on Pre- and Postoperative Variables. PR 2 PR 1 Scores Pre Post P Value* Pre Post P Value* Snoring VAS scores, mean (SD) 8.92 (1.16) 3.14 (1.64) < (1.41) 1.02 (1.15) <.001 Epworth sleepiness score, mean (SD) (4.15) 5.61 (3.09) < (3.27) 2.68 (2.04) <.001 Scores PR 1 vs. PR 2 Change (95% CI) P Value* Pre-Post snoring VAS scores 2.4 ( ) <.001 Pre-Post Epworth sleepiness scores 1.6 ( ) <.001 *Adjusted for age, gender, race, body mass index, obstructive sleep apnea severity, and preoperative scores. CI 5 confidence interval; PR 5 Pang-Rotenberg; SD 5 standard deviation; VAS 5 visual analog scale. 262

4 TABLE III. Predictors on Postoperative Outcomes. Variable Difference in Postoperative Snoring VAS Score (95% CI) P Value Difference in Postoperative Epworth Sleepiness Score (95% CI) P Value Male gender 1.5 (0.86 to 2.2) < (1.1 to 3.2) <.001 Race*.021 Chinese 1.5 (0.58 to 2.5) (1.0 to 3.9).001 Malay 1.4 (20.99 to 3.8) (21.2 to 6.3).180 Indian 1.4 (0.34 to 2.4) (1.3 to 4.5) <.001 PR (1.7 to 3.0) < (0.8 to 2.3) <.001 BMI (20.14 to ) (20.2 to 0.001).051 Age ( to ) (20.02 to 0.04).651 Preoperative AHI ( to 0.007) ( to 0.020).397 Preoperative score 0.89 (0.72 to 1.05) < (0.66 to 0.85) <.001 *Reference 5 others. AHI 5 apnea-hypopnea index; BMI 5 body mass index; CI 5 confidence interval; PR 5 Pang-Rotenberg; VAS 5 visual analog scale. tissues during sleep that results in snoring. 10 When the bulk of these soft tissues exceed a certain amount, it leads to collapse, partial or complete, of these structures, which then leads to upper airway obstruction during sleep. Patients with retrognathia will have less space available, therefore increasing the likelihood of airway compromise during sleep. There are some authors who believe that SDB is entirely based on the equilibrium between forces that hold the airway open and forces that tend to collapse the airway. 10 Simplistically, it is these factors and balances between the container (the nasomaxillary complex and the mandible) and the contents (the soft tissues in the oropharynx) that determine the severity of snoring and OSA; however, it is also well accepted that snoring and OSA are based on a dynamic neuro-electrophysiological interaction of impulses between the upper and lower airway. 10,11 Based on fundamental laws of physics and the pathophysiological principles of airflow dynamics, the proper assessment of the nasal cavity and passage is of essence. 11 In addition, the upper airway in the nose itself represents over 75% 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., negative 8 cm H 2 O) to distend the alveoli and to 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 was any form of upper airway blockage within the nasal passage (e.g., a deviated nasal septum, enlarged swollen turbinates, nasal polyps), the lungs would have to work harder to create a more negative pressure (e.g., negative 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, leading to collapse and obstruction of the hypopharyngeal upper airway. 10 Hence, it is 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 any form of 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 (palatal flutter/snoring), the first site of contact from the turbulent airflow. It is reasonable to therefore conclude that surgical correction of anatomical obstruction of the nasal passage alone does not cure OSA, but it can significantly decrease the negative pressure within the hypopharyngeal region. 4 Most authors would agree that the nasal surgery, as a single-site procedure, would not significantly impact sleep apnea severity, but may have some effect on snoring. 3 7 Verse and Pirsig showed through a meta-analysis of nine studies with 102 patients with OSA that the results of nasal surgery alone for these patients are at best <20%. 11 Li et al. had similar findings in their metaanalysis of 13 articles from 1999 to Two studies provided control groups and 11 articles (84.6%) consisted of prospective, noncontrolled clinical trials (level 2 in evidence strength). The weighted mean AHI measured by polysomnography in nine studies decreased from to events/hour after nasal surgery (overall, P 5.69). The pooled success rate of nasal surgery in treating OSA was 16.7%. Friedman et al. looked at 49 patients with OSA and actually showed worsening of the Respiratory Disturbance Index in patients with mild OSA undergoing nasal surgery alone. 13 This study showed that subjective nasal breathing improved in 49 (98%) patients, and snoring decreased or disappeared in 17 (34%), whereas the remaining 33 (66%) patients did not notice any significant change in their snoring, illustrating that nasal surgery alone does not reduce snoring. Based on these studies, instinctively treating the nose alone would not benefit the snorer or the sleep apneic. This study elegantly illustrates this point; patients with snoring have good results in snoring reduction after both nasal and palatal surgery, compared to 263

5 nasal surgery alone. To further refine and identify the patients who might have better prognosis in snoring reduction after nasal and palate surgery, we used the Pang-Rotenberg sign. From the 137 patients enrolled, a majority of them were PR-positive (72.3%), with significant snoring reduction after nasal and palate surgery. These patients who were PR-positive had significant reduction in their snoring level postoperatively (from 9.04 to 1.02), compared to patients who were PR-negative (from 8.91 to 3.14) (P <.001). There were significant reductions in both groups; however, there was more marked reduction in snoring VAS in the PR-positive group. By adjusting statistically for clinical covariates that might affect the snoring VAS change due to surgery, the PR-negative patients had only achieved an average of a 5.78 improvement in snoring VAS, whereas PR-positive patients achieved an average of a 8.02 improvement in snoring VAS (P <.001). The evident clinical and statistical difference in outcome aids the physician in preoperative counseling to better manage the patients and their bed partners expectations. Palatal flutter is difficult to produce when the mouth is closed, which is true for the majority of patients as demonstrated in our data. Hence, it is imperative to ensure that patients close their mouth during sleep; this can only be achieved if there is an open and patent nasal passage, which emphasizes the importance of nasal surgery in snoring patients who have limited and/restricted nasal passages. Although it is believed that mouth opening during sleep may also be a habitual event due to prolonged mouth opening from chronic nasal obstruction, this behavior can be modified with time and/or perhaps with a chin strap device, which is a mouth strap that aids in keeping the mouth closed during sleep. The patients who were PR-negative, who had residual snoring despite having had nasal and palate surgery, were reexamined to elucidate the site of the snoring sound during sleep. It was evident that the nasal snorting/grunting sound was produced from the fluttering and vibration of the salpingopharyngeus fold/ muscle in the nasopharyngeal and velopharyngeal level. It was found that these patients who were PR-negative had thicker and bulker salpingopharyngeal folds/ muscles, which led to the persistent snoring sound made during sleep despite a closed mouth and explains the poor results of snoring reduction in this group of PRnegative patients. A clinical trial is currently ongoing to stiffen these thick and bulky salpingopharyngeal folds. There were 16 patients who self-selected themselves as the control group. These patients were not keen to undergo both the nasal and palate surgery at the same sitting (either due to fear of multiple surgeries, postoperative pain, and/or lack of time availability). Despite preoperative counseling that their snoring reduction may not be significant, these patients proceeded to have only nasal surgery. This control group demonstrated poor snoring VAS reduction postoperatively from 9.21 to Their bed partners were still complaining of their persistent snoring. The lack of significant snoring reduction with nasal surgery alone illustrates the need to treat the palatal flutter as a source of loud snoring, as many of these patients might have persistent mouth opening during sleep resulting in palatal snoring. There was no clinical or statistical difference between the ESS in the PR-positive group or the PRnegative group, although as an entire group, the ESS improved from preoperative 11.5 to postoperative 2.6 (for both groups) (P <.001). The preoperative mean AHI and mean LSAT for both groups were very similar; the PRpositive group had a mean AHI of 29.6 compared to the PR-negative group with an AHI of The preoperative mean LSAT for the PR-positive group was 80.5%, whereas the preoperative mean LSAT for the PRnegative group was 82.4%. The two groups were further stratified into mild, moderate, and severe OSA categories; however, there was no correlation or influence between AHI and snoring reduction and/or PR status (Table III). A point to note is that there was a marginally larger decrease of BMI in the PR-positive group (from 27.5 to 24.7) compared to the PR-negative group (from 26.3 to 24.1). This was, however, not statistically significant. The data also suggested that being male with a lower preoperative BMI correlated with better postoperative snoring reduction. Limitations of this study would include the fact that there were no comparisons made between preoperative physical examinations with the PR sign. For example, tonsil size and Friedman tongue position were not compared; further studies are needed to delineate some of these correlations. CONCLUSION It is of importance and crucial to understand that the PR sign does not only measure the nature of the palate to create noise while snoring during sleep, but it also evaluates/accounts for other possible sites of noise production (such as the nasal snorting with mouth closed) from a simple noninvasive office maneuver. The PR sign has also shown to be a reliable prognostic indicator for snoring reduction after combined nose and palate surgery for patients with troublesome snoring and/or OSA. There is significant clinical and statistical reduction in snoring VAS scores in both PR-positive and PR-negative groups, although the reduction is larger in the group of patients who are PR-positive. BIBLIOGRAPHY 1. Young T, Palta M, Dempsey J, et al. The occurrence of SDB among middle-aged adults. N Engl J Med 1993;328: Young T, Evans L, Finn L, et al. Estimation of the clinically diagnosed proportion of sleep apnea syndrome in middle aged men and women. Sleep 1997;20: Verse T, Pirsig W, Kroker BA. Obstruktive Schlafapnoe und polyposis nasi. Laryngorhinootologie 1998;77: Friedman M, Tanyeri H, Lim JW, et al. Effect of nasal breathing on OSA. Otolaryngol Head Neck Surg 2000;122; Verse T, Joachim TM, Pirsig W. Effect of nasal surgery on sleep related breathing disorders. Laryngoscope 2002;112: Gleeson K, Zwillich CW, Bendrick TW, et al. Effect of inspiratory nasal loading on pharyngeal resistance. J Appl Physiol 1986;60: Kerr P, Millar T, Buckle P, et al. The importance of nasal resistance in OSA. J Otolaryngol 1992;21:

6 8. Terris DJ, Hanasono MM, Liu YC. Reliability of the Muller maneuver and its association with sleep-disordered breathing. Laryngoscope 2000;110: Bliwise DL, Feldman DE, Bliwise NG, et al. Risk factors for SDB in heterogeneous geriatric population. J Am Geriatr Soc 1987;35: Pang KP, Woodson BT. Current concepts in evaluation and surgical planning: The Pang-Woodson protocol. In: Pang KP, Rotenberg BR, Woodson BT, eds. Advanced Surgical Techniques in Snoring and Sleep Apnea. San Diego, CA.: Plural Publishing; Verse T, Pirsig W. Impact of impaired nasal breathing on sleep-disordered breathing. Sleep Breath 2003;7: Li HY, Wang PC, Chen YP et al. Critical appraisal and meta-analysis of nasal surgery for obstructive sleep apnea. Am J Rhinol Allergy 2011;25: Friedman M, Tanyeri H, Lim JW, et al. Effect of improved nasal breathing on obstructive sleep apnea. Otolaryngol Head Neck Surg 2000;122: