Available from: Sanghun Sin Retrieved on: 20 August 2015 The LaryngoscopeVC 2014 The American Laryngological,Rhinological and Otological Society, Inc.Anterior Nasal Resistance in Obese Children With Obstructive Sleep Apnea SyndromeSanghun Sin, MS; David M. Wootton, PhD; Joseph M. McDonough, MS; Kiran Nandalike, MD;Raanan Arens, MDObjectives/Hypothesis: To evaluate nasal resistance in obese children with and without obstructive sleep apnea syn-drome (OSAS), study the correlation between nasal resistance and severity of OSAS using the apnea-hypopnea index (AHI),and examine the association of gender and body mass index (BMI) with this measurement. Study Design: Retrospective analysis. Methods: Active anterior rhinomanometry was used to determine anterior nasal resistance (aNR) during wakefulness inthesupinepositionduringtidalbreathing.Thirty obesechildren withOSAS (aged13.8 6 2.6years,BMIzscore2.6 60.4)and 32 matched obese controls (aged 13.6 62.3 years, BMI z score 2.4 6 0.4), were studied. Unpaired t tests and Spearmancorrelation were performed. Results: The OSAS group had significantly higher aNR than the non-OSAS group during inspiration (P 5.012) and expi-ration (P 5.003). A significant correlation between inspiratory aNR and AHI was found for the OSAS group (r 50.39, P 5.04).The aNR did not correlate with BMI z score or with either gender. Conclusions: We noted a higher aNR in obese children with OSAS as compared to obese controls, and the aNR on inspi-ration correlated significantly with AHI. These findings suggest that a causal or augmentative effect of high inspiratory aNRmay exist for obese children who exhibit OSAS. Key Words: Active anterior rhinomanometry, obesity, obstructive sleep apnea syndrome. Level of Evidence: 3b. Laryngoscope, 124:2640–2644, 2014 INTRODUCTION yngeal fat pad tissues, induce sleep apnea by narrowingObstructivesleepapneasyndrome(OSAS)isa the upper airway.6–8 For a given inspiratory flow rate inrespiratory disorder characterized by repeated episodes theairway,increasedairwayresistanceanteriortoaofflowlimitationorcompletecessationofflowdueto given point in the airway will increase the magnitude ofpartialnarrowingorcompleteocclusionof thepharyn- negative pressure loading at that point, favoring its nar-geal airway during sleep.1 These respiratory eventsare rowingand/orcollapse.Additionally,thiswillbefacili-followed by alterations in gas exchange arousals leading tated if there is no increased reflex activation of airwayto disruption of normal sleep pattern. tomaintaintheairwaypatency.Distaltothechoanae,OSASaffects2%to4%ofchildreninthegeneral the pharynx is particularly liable to collapse, especially inpopulation.2 However, obese children have a much higher the region of the soft palate, tonsils, and adenoids. Like-prevalenceofthedisorderthatmayapproach50%.3–5 wise, the oropharynx is susceptible to collapse due to theThus, obesity is an important risk factor for the develop- tongue,tonsils,andthedistensiblenatureofthesur-ment of OSAS in children. Several studies suggest that rounding structures comprising theairway. particular anatomical factors around the pharyngealair- Although adenotonsillectomy is considered the first-way in obese children, including lymphoid and paraphar- line treatment in OSAS in obese children with adenoton- sillar hypertrophy, up to 50% may still have unresolved OSASaftertheirsurgery.9–11ThissuggeststhatotherFromtheDivisionofRespiratoryandSleepMedicine(S.S.,K.N., factors not ameliorated by adenotonsillectomy contributeR.A.),the Children’s Hospital at Montefiore and Albert Einstein College toOSASinobesechildren.Factorsto beconsideredof Medicine, Bronx, New York; the Department of Mechanical Engineer- include lowupperairway muscle tone,increased para-ing (D.M.W.), Cooper Union for the Advancement of Science and Art,New York, New York; and the Division of Pulmonary Medicine (J.M.M.),The pharyngealfatandupperairwaytissue fat content,Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, U.S.A. altered chest-wall mechanics,whichcan all increaseEditor’sNote:ThisManuscriptwasacceptedforpublication upperairwaycollapsibilityduringsleep.In addition,February 19, 2014. anatomical abnormalities of the nasal passages, such asThis work was supported by National Institutes of Health grants5 R01 HD053693 and 5 R01 HL105212. nasal septal deviation, nasal turbinate hypertrophy, andThe authors have no other funding, financial relationships, orcon- Allergic rhinitis, couldincreaseupper airwaynasalflicts of interest to disclose. resistance and perpetuate OSAS in these subjects.Send correspondence to Raanan Arens, MD, Divisionof Respira- tory and Sleep Medicine, Children’s Hospital at Montefiore, 3415Bain- The relationship between nasal resistance and OSAS isbridge Avenue, Bronx, NY 10467. E-mail: rarens@montefiore.org notwelldefined.12SeveralstudiesusingastandardizedDOI: 10.1002/lary.24653 method known as active anterior rhinomanometry (AAR)Laryngoscope 124: November 2014 Sin et al.: Nasal Resistance in Obese Children With OSAS 2640 Fig. 1. Diagram with flow versus pressure changes from a control(A) (apnea-hypopnea index [AHI]: 0, anterior nasal resistance [aNR]: 0.256 kPa/L/s on inspiratory, aNR: 0.258 kPa/L/s on expira-tory) and an obstructive sleep apnea syndrome subject (B) (AHI: 5.7, aNR: 1.149 kPa/L/s during inspiratory, aNR: 1.297 kPa/L/s during expiratory). Green line: pressure reference value at 150 Pa; blue curve: a breathing cycle of the right nostril; red curve: a breathe cycle of the left nostril. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com.]have shown that adults with OSAS have higher anterior nasal resistance (aNR) compared to controls.13,14 However, data in children, and particularly in obese children, are lack-ing. Thus, the main aim of the study was to use a standar-dized method of AAR to evaluate the relationship between aNR and the occurrence of OSAS in obese children compared to controls. We hypothesize that obese children with OSAS have an increase in aNR that preloads the nasopharynx and oropharynx, and that this resistance will correlate with the severity of the disorder. Such an abnormality may also help explain the low response to adenotonsillectomy in these sub-jects. A secondary aim was to examine the role of gender and body mass index (BMI) on aNR in these groups.MATERIALS AND METHODSSubjects and ProceduresAll children were recruited at the Children’s Hospital at Montefiore (CHAM), Bronx, New York. The study was approved by the Committee of Clinical Investigations at Albert EinsteinLaryngoscope 124: November 2014 College of Medicine, Bronx, New York. Sixty-four obese children with intact tonsils and adenoids in the age range of 8 to 17 years (BMI >95th percentile for age and gender) were initially enrolled into the study. After an overnight polysomnography (PSG) study, each subject was classified as an OSAS or a con-trol. Subjects were excluded if they had abnormal development or a known metabolic or endocrine disorder. Subjects were also excluded if they had complete unilateral or bilateral nasal obstruction, which precludes measuring nasal resistance with anterior rhinomanometry. Thus, two of the OSAS subjects were excluded from final analysis due to unilateral nasal obstruction.
Overnight PSG
To evaluate for the existence and severity of OSAS, over-night PSG (Xltek, Oakville, ON, Canada) was conducted at the Sleep Disorders Center at the CHAM. OSAS was defined if the apnea index (AI) was 1/hour and/or the apnea-hypopnea index (AHI) was 5/hour. Sleep scoring was performed according to standard criteria as defined by the American Academy of Sleep Medicine.15
Active aNR
To measure aNR we used the AAR technique.16 Accordingly, transnasal pressure and airflow were measured separately in each nostril during quiet tidal breathing in the supine position during wakefulness. Airflow and pressure were collected by a research grade clinical rhinomanometer (NR6; GM Instruments, Kilwinning, UK) with a face mask. Patients were allowed to blow their nose prior to test if needed. We used disposable foam plugs fitted with a pressure-sensing tube inserted into one nostril to carry out the pressure measurement while airflow through the other nostril was measured by a pneumotachometer. Measure-ment of the opposite nostril was performed in the same fashion. Thus, pressure measured in the occluded nostril is equivalent to the driving pressure at the choanal junction, because the air col-umn in the occluded nostril is stagnated. Subjects maintained a closed mouth during the measurement. Measurements included four breathing phases: ascending and descending phases during inspiration and expiration.
Unilateral nasal resistance. Unilateral nasal resistance (uNR) of each nostril was defined at the 150 Pa standard trans-nasal pressure value (Fig. 1). Twelve respiratory cycles were recorded and averaged for each subject during inspiration and expiration. Measurements were discarded if flow and pressure waveforms were atypical of normal breathing.
aNR. aNR was calculated using the two parallel resistan-ces addition: (uNRR 3 uNRL)/(uNRR 1uNRL), where uNRR and uNRL are right and left unilateral measurements, respectively.
Statistical Methods
Demographics, polysomnographic, and rhinomanometry data are presented as mean 6standard deviation values for OSAS and control groups. End points between groups were compared using two-tailed unpaired t tests, and Spearman cor-relation analysis was performed to evaluate the association between aNR and AHI, gender, and BMI z score for all subjects. P <.05 was considered significant. A commercial statistical soft-ware package (SigmaPlot version 12; Systat Software, San Jose, CA) was used for all sta
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