Anterior Nasal Resistance in Obese Children with Obstructive Sleep Apnea Syndrome (OSAS)

Sanghun Sin, MS1, David M. Wootton, PhD2, Joseph M. McDonough, MS3, Kiran Nandalike, MD1, Raanan Arens, MD1*

Division of Respiratory and Sleep Medicine, the Children’s Hospital at Montefiore and Albert Einstein College of Medicine1, Department of Mechanical Engineering, Cooper Union for the Advancement of Science and Art2, and the Division of Pulmonary Medicine, The Children’s Hospital of Philadelphia3

*Corresponding author: Raanan Arens, M.D., Division of Respiratory and Sleep Medicine Children’s Hospital at Montefiore 3415 Bainbridge Avenue Bronx, NY, 10467 Email: [email protected] Tel: (718) 515-2330; Fax: (718) 515-2608 Financial Support: National Institutes of Health Grants 5 R01 HD053693 and 5 R01 HL105212. Conflict of Interest: None

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/lary.24653 The American Laryngological, Rhinological and Otological Society, Inc.

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ABSTRACT: Objective/Hypothesis: To evaluate nasal resistance in obese children with and without 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 in the supine position during tidal breathing. Thirty obese children with OSAS (age 13.8±2.6 yrs, BMI-Z score 2.6±0.4) and 32 matched obese controls (age 13.6±2.3 yrs, BMI-Z score 2.4±0.4), were studied. Unpaired t-tests and Spearman correlation were performed. Results: The OSAS group had significantly higher aNR than the non-OSAS group during inspiration (p=0.012) and expiration (p=0.003). A significant correlation between inspiratory aNR and AHI was found for the OSAS group (r=0.39, p=0.04). 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 inspiration correlated significantly with AHI. These findings suggest that a causal or augmentative effect of high inspiratory aNR may exist for obese children who exhibit OSAS. Key words:

AAR: Active anterior rhinomanometry, Obesity, OSAS: Obstructive sleep apnea syndrome

Level of Evidence: 3b

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INTRODUCTION: Obstructive sleep apnea syndrome (OSAS) is a respiratory disorder characterized by repeated episodes of flow limitation or complete cessation of flow due to partial narrowing or complete occlusion of the pharyngeal airway during sleep 1. These respiratory events are followed by alterations in gas exchange arousals leading to disruption of normal sleep pattern. OSAS affects 2-4% of children in the general population 2. However, obese children have a much higher prevalence of the disorder that may approach 50%

3-5

. Thus, obesity is an

important risk factor for the development of OSAS in children. Several studies suggest that particular anatomical factors around the pharyngeal airway including lymphoid and parapharyngeal fat pad tissues in obese children induce sleep apnea by narrowing the upper airway 6-8. For a given inspiratory flow rate in the airway, increased airway resistance anterior to a given point in the airway will increase the magnitude of negative pressure loading at that point, favoring its narrowing and/or collapse. Additionally, this will be facilitated if there is no increased reflex activation of airway to maintain the airway patency. Distal to the choanae, the pharynx is particularly liable to collapse, especially in the region of the soft palate, tonsils and adenoids. Likewise, the oropharynx is susceptible to collapse due to the tongue, tonsils and the distensible nature of the surrounding structures comprising the airway. Although adenotonsillectomy is considered the first-line treatment in OSAS in obese children with adenotonsillar hypertrophy, up to 50% may still have unresolved OSAS after their surgery 9-11. This suggests that other factors not ameliorated by adenotonsillectomy contribute to OSAS in obese children. Factors to be considered include: low upper airway muscle tone, increased parapharyngeal fat and upper airway tissue fat content, altered chest-wall mechanics, all that could increase upper airway collapsibility during sleep; as well as anatomical

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abnormalities of nasal passages such as: nasal septal deviation, nasal turbinate hypertrophy, and allergic rhinitis, that could increase upper airway nasal resistance and perpetuate OSAS in these subjects. The relationship between nasal resistance and OSAS is not well defined

12

. Several

studies using a standardized method known as active anterior rhinomanometry (AAR) have shown that adults with OSAS have a higher anterior nasal resistance (aNR) compared to controls 13,14

. However, data in children and particularly in obese children is lacking. Thus, the main aim

of the study was to use a standardized method of AAR to evaluate the relationship between aNR and the occurrence of OSAS in obese children as compared to controls. We hypothesize that obese children with OSAS have an increase in aNR that pre-loads the nasopharynx and oropharynx and that this resistance will correlate with severity of the disorder. Such an abnormality may also help explain the low response to AT in these subjects. A secondary aim was to examine the role of gender and body mass index (BMI) on aNR in these groups.

METHODS: Subjects and Procedures All children were recruited at the Children’s Hospital at Montefiore (CHAM), Bronx, NY, USA. The study was approved by the Committee of Clinical Investigations at Albert Einstein College of Medicine, Bronx, NY. Sixty-four obese children with intact tonsils and adenoids in the age range of 8 to 17, (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 Control. 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

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bilateral nasal obstruction, which precludes measuring nasal resistance with anterior rhinomanometry. Thus, 2 of the OSAS subjects were excluded from final analysis due to unilateral nasal obstruction.

Overnight Polysomnography To evaluate for the existence and severity of OSAS an overnight polysomnography (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 AHI was >=5/hour. Sleep scoring was performed according to standard criteria as defined by the American Academy of Sleep Medicine 15. Active Anterior Rhinomanometry 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 Rhinomanomer (GM Instruments NR6, Kilwinning, KA13 6U, 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 and inserted into one nostril to carry out the pressure measurement while airflow through the other nostril was measured by a pneumotachometer. Measurement 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 column 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 (uNR): Nasal resistance of each nostril was defined at the 150 Pa standard transnasal pressure value (Figure 1). Twelve respiratory cycles were recorded and

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averaged for each subject during inspiration and expiration. Measurements were discarded if flow and pressure waveforms were atypical of normal breathing. Anterior nasal resistance: aNR was calculated using the two parallel resistances addition: (uNRR × uNRL)/ (uNRR + uNRL), where uNRR and uNRL are Right and Left unilateral measurements, respectively. Statistical Methods Demographics, polysomnographic, and rhinomanometry data are presented as mean ± standard deviation (SD) values for OSAS and control groups. Endpoints between groups were compared using two-tailed unpaired t-tests and Spearman correlation analysis was performed to evaluate the association between aNR and: AHI, gender, and BMI-Z score for all subjects. A p < 0.05 was considered significant. A commercial statistical software package (SigmaPlot 12, San Jose, CA, USA) was used for all statistical computations.

RESULTS: Demographic characteristics are summarized in Table 1. Obese control subjects (n = 32) with the mean age of 13.6 ± 2.3 years (range 8-17 years) and obese OSAS subjects (n = 30) with mean age of 13.8 ± 2.6 years (range 8-17 years) were studied. 12 females (37%) in control and 9 females (30%) in OSAS were included. BMI Z-scores of control and OSAS patients were 2.4 ± 0.4 and 2.6 ± 0.4, respectively. The control group included: 17 Hispanic, 11 African American and 4 other ethnicities and the OSAS group included: 16 Hispanic, 11 African American and 3 other ethnicities. Eleven of the 32 (34%) of controls and 6/30 (20%) of the OSAS subjects had history of allergic rhinitis (p=NS). There were no significant differences in demographic characteristics between groups.

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Polysomnographic data are presented in Table 2. Significant differences between controls and OSAS were noted, particularly in regard to: Apnea Index (AI, events/hr) 0.1 ± 0.3 vs. 3.8 ± 5.9 (p = 0.002), AHI 1.5 ± 1.6 vs. 24.2 ± 25.0 (p < 0.001), SpO2 Nadir (%) 92.9 ± 3.3 vs. 82.1 ± 6.9 (p < 0.001). Arousal Index (events/hr) was also significantly higher in OSAS (24.3 ± 20.2) than control (6.8 ± 3.6) (p < 0.001). For all subjects the correlation coefficient between AI and AHI was 0.73 (p

Anterior nasal resistance in obese children with obstructive sleep apnea syndrome.

To evaluate nasal resistance in obese children with and without obstructive sleep apnea syndrome (OSAS), study the correlation between nasal resistanc...
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