Original Research—Pediatric Otolaryngology

Blood Pressure after Surgery among Obese and Nonobese Children with Obstructive Sleep Apnea

Otolaryngology– Head and Neck Surgery 2015, Vol. 152(5) 931–940 Ó American Academy of Otolaryngology—Head and Neck Surgery Foundation 2015 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0194599815573927 http://otojournal.org

Yen-Lin Kuo, MD1,2, Kun-Tai Kang, MD, MPH1,3,4, Shuenn-Nan Chiu, MD, PhD5, Wen-Chin Weng, MD5, Pei-Lin Lee, MD, PhD6,7, and Wei-Chung Hsu, MD, PhD1,6

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Abstract Objectives. Treating obstructive sleep apnea in children is found to be associated with blood pressure decreases. However, exactly how adenotonsillectomy (T&A) affects blood pressure in obese and nonobese children remains unclear. This study assesses how obesity affects blood pressure in children with sleep apnea after T&A. Study Design. Case series with chart review. Setting. A tertiary referral center. Subjects and Methods. From 2010 to 2012, a total of 78 children were included. Based on propensity score methods (age, sex, and preoperative apnea-hypopnea index matched), children were assigned to either the obese group (n = 39) or the nonobese group (n = 39). All children received adenotonsillectomy. We recorded clinical symptoms, preoperative overnight polysomnography (PSG), and subsequent PSG within 3 months after T&A. We measured blood pressure 3 times before PSG (nocturnal blood pressure) and after PSG (morning blood pressure) in a sleep laboratory. Results. Following surgery, the nonobese group had a significantly decreased nocturnal diastolic blood pressure (DBP) index (–12.0 to 218.8, P = .018), morning systolic blood pressure (SBP; 111.1 to 105.8 mm Hg, P = .014), SBP index (–5.4 to 210.9, P = .008), and DBP (–12.0 to 218.7, P = .023). Nevertheless, all blood pressure parameters in the obese group were not significantly changed postoperatively. The nonobese group improved more than obese group in nocturnal and morning DBP and DBP index by 2-way analysis of variance. Conclusion. Among the children receiving T&A as treatment for OSA, nonobese children improved more than obese children did in terms of blood pressure, allowing us to infer that obese children with OSA may benefit less from T&A in cardiovascular morbidities.

Keywords adenotonsillectomy, blood pressure, child, obesity, sleep apnea syndromes, tonsillectomy Received September 24, 2014; revised January 19, 2015; accepted January 30, 2015.

A

s is well recognized, obstructive sleep apnea (OSA) in adults is associated with hypertension1,2 and other cardiovascular morbidities.3,4 In children, several studies correlated OSA with hypertension.5-7 Guilleminault et al5 first described high blood pressure (BP) in children with OSA in 1976. Li et al7 asserted that OSA in children was correlated with elevated daytime and nocturnal blood pressure. Previous studies suggested that some children with OSA have a higher blood pressure, possibly causing further end-organ damage.5-11 Hypertrophy of adenoids and tonsils are the main causes of OSA in children.12 Thus, adenotonsillectomy (T&A) is widely recognized as the most effective therapy for childhood sleep apnea.13-16 Recent literature has shown T&A would improve cardiovascular parameters in children with sleep apnea.17-19 Importantly, T&A significantly improves respiratory events13-16 and plays a major role in reversing the cardiovascular sequelae of OSA.17-19 1

Department of Otolaryngology, National Taiwan University Hospital, Taipei, Taiwan 2 Department of Otolaryngology, National Taiwan University Hospital, Hsinchu Branch, Taipei, Taiwan 3 Department of Otolaryngology, Taipei Hospital, Ministry of Health and Welfare, New Taipei City, Taiwan 4 Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan 5 Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan 6 Sleep Center, National Taiwan University Hospital, Taipei, Taiwan 7 Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan Corresponding Author: Wei-Chung Hsu, MD, PhD, Department of Otolaryngology, National Taiwan University Hospital, #7, Chung-Shan South Road, Taipei, Taiwan. Email: [email protected]

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The global epidemic of pediatric obesity represents a major societal burden worldwide.20-28 Obesity is associated with alterations in the endocrine and inflammatory process of fat cells, many of which may modulate blood pressure20-24 and respiratory control.25-28 Childhood obesity is increasingly recognized as related to both pediatric OSA25-30 and hypertension.20-24 Given the high prevalence of obesity-related OSA, further research is needed to understand how these 2 conditions interact with their connections to adverse cardiovascular events.26-28 However, to our knowledge, obese and nonobese children with sleep apnea have never been compared in terms of postoperative blood pressure changes. This study elucidates how obesity-related OSA and nonobesity-related OSA in children differ in blood pressure after surgery. By using propensity score–matched methods, possible confounders affecting blood pressure are eliminated. Exactly how pediatric obesity and OSA interact with each other and contribute to cardiovascular parameter changes in children after surgery is also examined.

Methods Study Group The study protocol was approved by the Ethics Committee of National Taiwan University Hospital (Taipei, Taiwan). Informed consent was obtained from the parents of the participants during the postoperative follow-up periods. From May 2010 to January 2012, children aged 3 to 18 years with OSArelated symptoms were recruited for this study. Children were included if they had signs and symptoms of a sleep disturbance, including snoring and mouth breathing; witnessed apnea for at least 1 month; and were shown to have OSA by polysomnography (PSG). Children with clinical symptoms and an apnea-hypopnea index (AHI) 1 were included in the study and received T&A. Exclusion criteria were significant medical illnesses such as cardiac, respiratory, or renal insufficiency; craniofacial anomalies; neuromuscular diseases; children younger than 3 years; suboptimal sleep studies (total sleep time \4 hours or sleep efficiency \60%); and previous tonsil, adenoid, or pharyngeal surgery. Detailed histories were obtained and physical examinations were done. Basic data, including age, sex, symptoms, and signs of sleep disturbances, were recorded, as were history of nasal allergy, otitis media with effusion, and sinusitis or asthma. Adenoid size was measured on a lateral radiograph according to the method by Fujioka et al,31 which defined enlarged adenoids as having an adenoid/nasopharynx ratio .0.67. The tonsils were graded using the scheme by Brodsky et al,32 and we defined grade III or IV as tonsillar hypertrophy. Body mass index (BMI) was calculated. The age- and sex-adjusted BMI was applied using established guidelines to convert BMI into BMI percentile.33 Obesity was defined as a BMI higher than the 95th percentile for a child’s age and sex.26-30,33

Adenotonsillectomy Children with a PSG diagnosis of OSA were requested to have tonsillectomy and adenoidectomy as the

treatment. Tonsillectomy was performed using the coblation method, and adenoidectomy was performed using the microdebrider-assisted method. All surgical procedures were performed in a single stage under general anesthesia with 2-day hospitalization.34

Polysomnography Full-night PSG (Embla N7000; Medcare Flaga, Reykjavik, Iceland) was performed in a sleep laboratory following the established protocol.29-31,35-39 The sleep stage and respiratory events were scored according to the standard of the American Academy of Sleep Medicine.40 We adopted both nasal pressure and oronasal thermal flow for airflow detection and inductance plethysmography for respiratory belts. Obstructive apnea is defined as continued inspiratory effort associated with a .90% decrease in airflow for a duration of 2 breaths. Hypopnea is defined as a 50% decrease in airflow for a duration of 2 breaths associated with arousal, awakening, or reduced arterial oxygen saturation of 3%. Pediatric OSA is defined as an AHI 1 event per hour in the overnight polysomnographic study.12-16,29-30,35-39 All children had a preoperative PSG to diagnose OSA and also received a PSG within 3 months after surgery. Residual OSA is defined as AHI 1 after T&A.13,14,15,30

Blood Pressure Measurements Systolic and diastolic blood pressure were measured in a sleep laboratory, using an electronic sphygmomanometer (Terumo Digital Blood Pressure Monitor ES-H55; Terumo Medical Corporation, Tokyo, Japan) with appropriate-sized arm cuffs.41 Measurements were taken on each subject 3 times, who was resting in a sitting position for 10-15 min.41 We took casual BP measurements before PSG in the evening (nocturnal) and after PSG in the next morning (morning). The BP before PSG (nocturnal BP) may demonstrate the baseline status, and the BP after PSG (morning BP) may show the sleep effect on cardiovascular status.42,43 Blood pressure values were further compared with established guidelines for age and sex normative data.44 Different age and sex groups were compared by applying BP percentile and the BP index.6,8,11,44 The BP index was calculated by using the following formula: BP index 5ðmeasured BP  95th percentileÞ= 95th percentile 3 100:

Statistical Methods Data were analyzed using SPSS software version 20 (SPSS, Inc, an IBM Company, Chicago, Illinois). Continuous data were expressed as the mean and standard deviation and categorical data as the number and percentage. We performed propensity score matching to eliminate a potential bias due to uneven distribution of the confounding factors between obese and nonobese groups.45 Thirty-nine obese children with OSA were identified first, followed by the calculation of a logit probability (also called propensity score)

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Table 1. Demographic and Polysomnographic Characteristics between Obese and Nonobese Children with Obstructive Sleep Apnea. NOB (n = 39) Parameter Age range, y Sex, male/female Weight, kg Weight, percentile Height, cm Height, percentile BMI, kg/m2 BMI, percentile Total sleep time, min Sleep efficiency, % REM, % NREM, % Stage 1 (N1) Stage 2 (N2) Stage 3 (N3) AHI, event/h Mean SpO2, % Nadir SpO2, % AI, event/h

Pre

Pa

Pre

– – \.001 NS \.001 NS .006 NS NS NS NS

9.4 6 3.8 28:11 49.8 6 21.8 96.0 6 5.0 137.7 6 21.7 70.1 6 28.0 24.6 6 4.2 98.5 6 1.1 366.7 6 50.8 86.1 6 10.8 18.2 6 6.3

9.6 6 – 51.0 6 95.1 6 139.4 6 70.0 6 24.8 6 97.3 6 382.5 6 91.2 6 19.6 6

3.6 NS 17.3 NS 17.0 NS 7.5 \.001 0.7 \.001 4.5 \.001 2.5 .009

7.2 6 4.8 47.0 6 14.0 27.7 6 13.9 18.0 6 21.9 96.2 6 2.0 83.6 6 8.3 7.8 6 3.8

4.9 6 38.3 6 35.1 6 2.0 6 97.4 6 89.5 6 4.1 6

Post

8.9 6 3.3 28:11 32.3 6 14.9 53.0 6 30.4 130.8 6 20.7 51.3 6 31.9 17.7 6 3.0 57.0 6 28.6 377.9 6 44.7 88.2 6 9.3 16.6 6 6.3

9.2 6 – 34.6 6 59.0 6 133.9 6 54.3 6 18.3 6 61.6 6 372.7 6 90.4 6 19.2 6

4.6 6 2.9 37.9 6 18.2 40.9 6 18.1 18.1 6 23.6 96.9 6 1.4 83.8 6 8.9 6.1 6 3.3

4.4 6 40.8 6 34.6 6 2.5 6 97.9 6 90.6 6 4.4 6

OB (n = 39)

3.2 15.3 27.8 20.5 31.5 3.1 28.5 50.9 10.2 5.8

Group Comparison Pa

P at Preb

P at Postb

P Interactionc

22.0 7.5 21.1 25.5 4.6 3.9 38.8 7.1 6.1

– – .001 NS \.001 NS NS .006 NS .003 .218

NS – \.001 \.001 NS .007 \.001 \.001 NS NS NS

NS – \.001 \.001 NS .033 \.001 \.001 NS NS NS

– – .043 .003 .011 NS NS .024 .046 NS NS

3.5 17.1 18.0 2.4 0.9 3.4 1.7

.003 .007 .032 \.001 \.001 \.001 \.001

.008 NS \.001 NS .032 NS .031

NS NS NS NS .006 NS NS

.019 .030 .008 NS NS NS .026

Post 3.7

Abbreviations: AHI, apnea-hypopnea index; AI, total arousal index; BMI, body mass index; Mean SpO2, average oxygen saturation; Nadir SpO2, minimum oxygen saturation; NOB, nonobese; NREM, nonrapid eye movement; NS, not significant; OB, obese; REM, rapid eye movement; —, not applicable. a Wilcoxon signed rank test. b Mann-Whitney U test. c Interaction of ‘‘group by time’’ obtained from the generalized estimating equation for both continuous and categorical variables.

for each subject, based on the following confounding factors: age, sex, and preoperative AHI. Finally, each subject from the obese group was matched to a corresponding subject from the nonobese group by using the propensity score. Subjects without a match were withdrawn from the study. Continuous variables such as weight, height, BMI, sleep parameters, and BP parameters before and after T&A were then compared using the Wilcoxon signed rank test. Categorical variables such as the prevalence of subjects greater than the 90th or 95th BP percentile before and after T&A were compared using the McNemar test. The preoperative and postoperative values between the obese and nonobese groups were compared by the Mann-Whitney U test for continuous variables and by the Fisher exact test for categorical variables. The difference in improvement (change) from preoperative to postoperative between adiposity groups was tested by a 2-way repeated-measures analysis of variance (ANOVA), which was estimated with the generalized estimating equation (GEE). The parameters changed in one group more than another group when the interaction of ‘‘group by time’’ was statistically significant. P interaction was used to compare the change (before and after difference) between groups (ie, obese and nonobese, etc). P \ .05 means that one group changed more than the other. On the basis of the postoperative AHI data, children were further assigned to the resolved group (AHI \1) and

residual group (AHI 1). Moreover, the resolved group and the residual group were compared in terms of the BP parameter changes after surgery. A P value lower than .05 was considered statistically significant.

Results A total of 253 children with OSA who underwent T&A were first identified. Sixty-two children were excluded due to incomplete records or suboptimal PSG data, while 38 children were excluded by exclusion criteria. Another 2 subjects with previous adenoid or pharyngeal surgeries were excluded as well. In total, 151 subjects were enrolled. On the basis of propensity score methods, children were assigned into either the obese group (n = 39) or the nonobese one (n = 39). Seventy-three subjects without a match were withdrawn. The mean age of study participants was 9.16 3.5 years. Boys comprised 71.8% (56/78). Adenoid hypertrophy was observed in 55.1% (43/78) of all children, whereas tonsil hypertrophy was found in 91.0% (71/78). Although the 2 groups did not significantly differ in AHI (P . .05), the nonobese group had a slightly higher average oxygen saturation (mean SpO2) than did the obese group before surgery (96.9% vs 96.2%, P = .032). Table 1 summarizes the demographic and clinical information for all subjects, including the obese and the

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Table 2. Blood Pressure Changes in Obese and Nonobese Children with Obstructive Sleep Apnea.a NOB (n = 39) Parameter Before PSG (nocturnal) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile After PSG (morning) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile

OB (n = 39)

Group Comparison

Pre

Post

Pb

Pre

Post

Pb

P at Prec

P at Postc

P Interactiond

110.2 6 8.5 –6.3 6 8.6 68.1 6 9.8 –12.0 6 12.5 16 (41.0) 10 (25.6) 16 (41.0) 6 (15.4)

106.7 6 10.6 –10.1 6 9.5 63.5 6 9.6 –18.8 6 12.7 8 (20.5) 3 (7.7) 6 (15.4) 3 (7.7)

NS NS NS .018 NS NS .013 NS

112.1 6 8.3 –6.6 6 7.9 66.4 6 11.2 –15.6 6 13.3 12 (30.8) 7 (17.9) 10 (25.6) 5 (12.8)

111.7 6 8.0 –7.2 6 7.6 70.2 6 8.2 –11.0 6 10.7 14 (35.9) 4 (10.3) 11 (28.2) 3 (7.7)

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

.017 NS .001 .002 NS NS NS NS

NS NS .005 .003 NS (.051) NS .043 NS

111.1 6 7.5 –5.4 6 8.1 68.0 6 9.4 –12.0 6 12.4 13 (33.3) 7 (17.9) 15 (38.5) 8 (20.5)

105.8 6 10.5 –10.9 6 9.4 63.7 6 9.4 –18.7 6 12.1 9 (23.1) 5 (12.8) 8 (20.5) 4 (10.3)

.014 .008 NS .023 NS NS NS NS

112.5 6 9.4 –6.3 6 7.9 67.3 6 10.9 –14.3 6 14.0 13 (33.3) 7 (17.9) 11 (28.2) 4 (10.3)

110.7 6 10.6 –8.1 6 9.1 69.0 6 9.5 –12.7 6 11.1 11 (28.2) 5 (12.8) 9 (23.1) 3 (7.7)

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

.032 NS .008 .022 NS NS NS NS

NS NS .047 .041 NS NS NS NS

Abbreviations: DBP, diastolic blood pressure; NOB, nonobese; NS, not significant; OB, obese; PSG, polysomnography; SBP, systolic blood pressure. a Data are presented as mean 6 standard deviation or number (percentage). b Wilcoxon signed rank test for continuous variables and McNemar test for categorical variables. c Mann-Whitney U test for continuous variables and Fisher exact test for categorical variables. d Interaction of ‘‘group by time’’ obtained from the generalized estimating equation for both continuous and categorical variables.

nonobese groups with before-and-after surgery comparisons. Among all subjects, children significantly increased in weight, height, and BMI after surgery (41.0 to 42.8 kg, P \ .001; 134.2 to 136.6 cm, P \ .001; 21.2 to 21.5 kg/m2, P = .027, respectively). Nonobese children significantly increased in parameters such as weight, height, and BMI after surgery (32.3 to 34.6 kg, P \ .001; 130.8 to 133.9 cm, P \ .001; 17.7 to 18.3 kg/m2, P = .006, respectively). Obese children also increased in weight and height (49.8 to 51.0 kg, P = .001; 137.7 to 139.4 cm, P \ .001, respectively), yet decreased in BMI percentile (98.5 to 97.3, P = .006) after surgery.

Polysomnography After surgery, children significantly improved in sleep parameters, including, AHI, arousal index (AI), mean SpO2, and minimum oxygen (nadir SpO2) (18.0 to 2.3/h, P \ .001; 7.0 to 4.2/h, P \ .001; 96.6% to 97.6%, P \ .001; 83.7% to 90.1%, P \ .001, respectively). Similarly, both groups significantly improved in respiratory parameters after T&A, including AHI, AI, mean SpO2, and nadir SpO2 (Table 1).

Blood Pressure Table 2 compares the obese and nonobese groups in terms of blood pressure before and after surgery. After surgery, the nonobese group had a significant decrease in the

nocturnal diastolic blood pressure (DBP) index (–12.0 6 12.5 to 218.8 6 12.7, P = .018). The nonobese group also had a significant decrease in the prevalence of DBP .90th percentile (41% to 15.4%, P = .013) in nocturnal BP measurement. Similar findings were observed in morning blood pressure parameters. The nonobese group had a significant decrease in systolic blood pressure (SBP), SBP index, and DBP index (111.1 to 105.8 mm Hg, P = .014; 25.4 to 210.9, P = .008; 212.0 to 218.7, P = .023, respectively) after surgery. In contrast, the obese group did not significantly change in nocturnal or morning blood pressure parameters. Moreover, the obese group had an increase in the nocturnal and morning DBP and DBP index postoperatively, although not reaching statistical significance. In group comparison, we found that the nonobese group improved more than the obese group in nocturnal and morning DBP and DBP index by analysis with the interaction of ‘‘group by time’’ obtained from the GEE. Figures 1 and 2 illustrate the postoperative changes of SBP and DBP in both obese and nonobese groups. Nonobese children had a significant decrease in both nocturnal and morning DBP after surgery, as well as in morning SBP (Figure 1B and Figure 2). Obese children, compared with the nonobese children, had a smaller decrease of SBP after surgery (Figure 1). Moreover, DBP after surgery was increased in the obese group, although statistically insignificant (Figure 2).

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Figure 1. Systolic blood pressure (SBP) changes in children with obstructive sleep apnea (A) before polysomnography (PSG) (nocturnal) and (B) after PSG (morning). NOB, nonobese; OB, obese; OP, operative. *P \.05 for preoperative and postoperative comparisons using the Wilcoxon signed rank test.

Figure 2. Diastolic blood pressure (DBP) changes in children with obstructive sleep apnea (A) before polysomnography (PSG) (nocturnal) and (B) after PSG (morning). NOB, nonobese; OB, obese; OP, operative. *P \.05 for preoperative and postoperative comparisons using the Wilcoxon signed rank test.

Blood Pressure Changes in Residual or Resolved OSA After T&A, 15 (38.4%) children in the nonobese group had residual OSA (AHI 1). Among them, 5 had AHI \5 and 10 had AHI 5. On the other hand, 21 (53.8%) obese children had residual OSA, including 4 children having AHI \5 and 17 children having AHI 5. Following surgery, the nonobese children with residual OSA had a significant decrease in the nocturnal DBP and DBP indices (71.2 to 63.8 mm Hg, P = .049; 28.6 to 218.9, P = .027, respectively), as well as morning SBP and SBP index (114.2 to 106.5 mm Hg, P = .043; 23.6 to 210.8, P = .036, respectively). The nonobese, OSA-resolved group also tended to have a decrease in blood pressure, yet not reaching statistical significance (Table 3). However, the group comparison did not reveal a significant difference in any blood pressure parameters between resolved and residual subgroups. The obese children did not significantly improve in all blood pressure parameters recorded in both the OSAresolved group and the OSA-residual group. Interestingly, the obese children with residual OSA had a significant increase in the nocturnal DBP and DBP indices (65.5 to 71.8 mm Hg, P = .032; 216.7 to 28.6, P = .034, respectively) postoperatively (Table 4). However, similar to the

nonobese group, group comparison did not show a significant difference between resolved and residual subgroups. Once OSA was resolved, there was no significant difference in BP change between obese and nonobese children (Table 5). However, nonobese children with residual OSA improved more in DBP than did their obese counterparts (Table 6).

Discussion To our knowledge, this study describes for the first time the disparities of postoperative BP changes among obese and nonobese children with OSA. Importantly, this study demonstrates that nonobese children with OSA improve more in SBP and DBP after surgery than do obese children. According to our results, the anticipated decreases in BP do not occur among obese children, implying obesity is a major determinant of postoperative BP change in children with sleep apnea. In adults, OSA inflicts a major cardiovascular burden.1-4 Pertinent studies posited that hypertension largely accounted for increased cardiovascular risks.1-4 While reviewing the associations between hypertension and OSA in adults, Phillips and O’Driscoll46 described how OSA caused hypertension: OSA

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Table 3. Blood Pressure Changes in Nonobese Children with or without Resolution of Sleep-Disordered Breathing.a NOB 1: OSA Resolved after T&A (n = 24) Parameter Before PSG (nocturnal) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile After PSG (morning) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile

NOB 2: Residual OSA after T&A (n = 15)

Group Comparison

Pre

Post

Pb

Pre

Post

Pb

P at Prec

P at Postc

P Interactiond

109.2 6 8.1 –6.7 6 8.4 66.1 6 11.1 –14.1 6 13.9 10 (41.7) 7 (29.2) 10 (41.7) 3 (12.5)

106.5 6 12.0 –10.0 6 10.9 63.3 6 9.3 –18.8 6 13.1 5 (20.8) 3 (12.5) 4 (16.7) 2 (8.3)

NS NS NS NS NS NS NS NS

111.7 6 9.2 –5.6 6 9.2 71.2 6 6.5 –8.6 6 9.1 6 (40.0) 3 (20.0) 6 (40.0) 3 (20.0)

107.1 6 8.1 –10.4 6 7.0 63.8 6 10.4 –18.9 6 12.4 3 (20.0) 0 (0.0) 2 (13.3) 1 (6.7)

NS NS .049 .027 NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

109.2 6 7.5 –6.6 6 8.1 65.8 6 10.2 –14.5 6 13.6 8 (33.3) 3 (12.5) 8 (33.3) 5 (20.8)

105.4 6 11.6 –10.9 6 10.4 63.0 6 8.6 –19.1 6 11.9 6 (25.0) 4 (16.7) 4 (16.7) 3 (12.5)

NS NS NS NS NS NS NS NS

114.2 6 6.8 –3.6 6 8.1 71.5 6 7.0 –8.1 6 9.5 5 (33.3) 4 (26.7) 7 (46.7) 3 (20.0)

106.5 6 8.8 –10.8 6 8.0 64.7 6 10.8 –17.9 6 12.8 3 (20.0) 1 (6.7) 4 (26.7) 1 (6.7)

.043 .036 NS NS NS NS NS NS

.027 NS .044 NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

Abbreviations: DBP, diastolic blood pressure; NOB, nonobese; NS, not significant; OSA, obstructive sleep apnea; PSG, polysomnography; SBP, systolic blood pressure; T&A, adenotonsillectomy. a Data are presented as mean 6 standard deviation or number (percentage). b Wilcoxon signed rank test for continuous variables and McNemar test for categorical variables. c Mann-Whitney U test for continuous variables and Fisher exact test for categorical variables. d Interaction of ‘‘group by time’’ obtained from the generalized estimating equation for both continuous and categorical variables.

Table 4. Blood Pressure Changes in Obese Children with or without Resolution of Sleep-Disordered Breathing.a OB 1: OSA Resolved after T&A (n = 18) Parameter Before PSG (nocturnal) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile After PSG (morning) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile

OB 2: Residual OSA after T&A (n = 21)

Pre

Post

Pb

113.4 6 9.0 –6.0 6 8.5 67.5 6 10.0 –14.4 6 12.2 6 (33.3) 4 (22.2) 4 (22.2) 3 (16.7)

110.4 6 7.8 –8.8 6 7.8 68.3 6 9.8 –13.9 6 12.4 5 (27.8) 1 (5.6) 4 (22.2) 0 (0.0)

NS NS NS NS NS NS NS NS

111.0 –7.2 65.5 –16.7 6 3 6 2

113.4 6 10.3 –6.1 6 8.1 66.8 6 10.3 –15.0 6 13.3 5 (27.8) 3 (16.7) 5 (27.8) 2 (11.1)

109.7 6 10.6 –9.4 6 9.2 66.0 6 10.4 –16.9 6 12.3 2 (11.1) 1 (5.6) 3 (16.7) 0 (0.0)

NS NS NS NS NS NS NS NS

111.8 –6.5 67.8 –13.6 8 4 6 2

Group Comparison

Post

Pb

P at Prec

P at Postc

P Interactiond

6 7.8 6 7.6 6 12.2 6 14.3 (28.6) (14.3) (28.6) (9.5)

112.9 6 8.2 –5.8 6 7.4 71.8 6 6.2 –8.6 6 8.6 9 (42.9) 3 (14.3) 7 (33.3) 3 (14.3)

NS NS .032 .034 NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

6 8.8 6 8.0 6 11.7 6 14.9 (38.1) (19.0) (28.6) (9.5)

111.6 6 10.7 –7.0 6 9.0 71.6 6 8.0 –9.2 6 8.8 9 (42.9) 4 (19.0) 6 (28.6) 3 (14.3)

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS .037 NS NS NS

NS NS NS NS NS NS NS NS

Pre

Abbreviations: DBP, diastolic blood pressure; NS, not significant; OB, obese; OSA, obstructive sleep apnea; PSG, polysomnography; SBP, systolic blood pressure; T&A, adenotonsillectomy. a Data are presented as mean 6 standard deviation or number (percentage). b Wilcoxon signed rank test for continuous variables and McNemar test for categorical variables. c Mann-Whitney U test for continuous variables and Fisher exact test for categorical variables. Downloaded from oto.sagepub.com at UNIV OF MISSISSIPPI on June 18, 2015 d Interaction of ‘‘group by time’’ obtained from the generalized estimating equation for both continuous and categorical variables.

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Table 5. Blood Pressure Changes between Obese and Nonobese Children Whose OSA Resolved after T&A.a NOB 1: OSA Resolved after T&A (n = 24) Parameter Before PSG (nocturnal) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile After PSG (morning) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile

Pre

OB 1: OSA Resolved after T&A (n = 18)

Group Comparison

Post

Pb

Pre

Post

Pb

P at Prec

P at Postc

P Interactiond

109.2 –6.7 66.1 –14.1 10 7 10 3

6 8.1 6 8.4 6 11.1 6 13.9 (41.7) (29.2) (41.7) (12.5)

106.5 6 12.0 –10.0 6 10.9 63.3 6 9.3 –18.8 6 13.1 5 (20.8) 3 (12.5) 4 (16.7) 2 (8.3)

NS NS NS NS NS NS NS NS

113.4 6 9.0 –6.0 6 8.5 67.5 6 10.0 –14.4 6 12.2 6 (33.3) 4 (22.2) 4 (22.2) 3 (16.7)

110.4 6 7.8 –8.8 6 7.8 68.3 6 9.8 –13.9 6 12.4 5 (27.8) 1 (5.6) 4 (22.2) 0 (0.0)

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS .048 NS NS NS NS NS

NS NS NS NS NS NS NS NS

109.2 –6.6 65.8 –14.5 8 3 8 5

6 7.5 6 8.1 6 10.2 6 13.6 (33.3) (12.5) (33.3) (20.8)

105.4 6 11.6 –10.9 6 10.4 63.0 6 8.6 –19.1 6 11.9 6 (25.0) 4 (16.7) 4 (16.7) 3 (12.5)

NS NS NS NS NS NS NS NS

113.4 6 10.3 –6.1 6 8.1 66.8 6 10.3 –15.0 6 13.3 5 (27.8) 3 (16.7) 5 (27.8) 2 (11.1)

109.7 6 10.6 –9.4 6 9.2 66.0 6 10.4 –16.9 6 12.3 2 (11.1) 1 (5.6) 3 (16.7) 0 (0.0)

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

Abbreviations: DBP, diastolic blood pressure; NOB, nonobese; NS, not significant; OB, obese; OSA, obstructive sleep apnea; PSG, polysomnography; SBP, systolic blood pressure; T&A, adenotonsillectomy. a Data are presented as mean 6 standard deviation or number (percentage). b Wilcoxon signed rank test for continuous variables and McNemar test for categorical variables. c Mann-Whitney U test for continuous variables and Fisher exact test for categorical variables. d Interaction of ‘‘group by time’’ obtained from the generalized estimating equation for both continuous and categorical variables.

induced intermittent hypoxia, hypercapnia, negative intrathoracic pressure swings, and arousals, along with sympathetic activation, oxidative stress, endothelial dysfunction, and chronic inflammatory status. All of the above factors incurred vasoconstriction and arterial stiffness and, thus, hypertension. In children, a meta-analysis by Zintzaras and Kaditis47 offered insufficient evidence that moderate to severe OSA was associated with hypertension. However, this finding was confounded by a small sample size and large heterogeneity among studies. Recent studies demonstrated a trend of elevated blood pressure in children with OSA.5-11,17-19 Li et al7 and Xu et al8 found that OSA in children was correlated with elevated BP. Horne et al9 indicated that pediatric OSA increased blood pressure during sleep more than in controls, regardless of OSA severity. The above findings asserted the correlations between increased BP and OSA in children, implying that treatment should be considered in this category of patients to prevent further cardiovascular complications. Obesity, as well as overweight status, can cause hypertension, ultimately increasing cardiovascular risks.22,23,48,49 In a meta-analysis by Friedemann et al,23 BMI outside the normal range significantly worsens risk parameters for cardiovascular disease in school-aged children. A national survey from 1988 to 2008 by Rosner et al48 found that BMI was independently associated with a prevalence of elevated

blood pressure in children. The same observation was also confirmed in an Asian population,22,49 raising the possibility that obesity may also affect outcomes in blood pressure parameters among children with sleep apnea having undergone surgery. Based on the above effects, the proposed causes for obese children to have higher BP is: sleep fragmentation, sustained sympathetic activation, intermittent hypoxia, and oxidative stress, all of which increased in proinflammatory vascular mediators and thus ultimately promoted cardiovascular morbidities.26,27 Few studies have addressed blood pressure changes in children having undergone T&A for OSA.18,19,50,51 Among these studies, 3 used casual BP measures, while only 1 study used 24-hour ambulatory BP monitoring and reported diastolic BP load improvements in children with OSA after surgery.19 In 2008, Amin et al18 described that children with OSA had a significant decrease in DBP 6 months after surgery, and AHI was a significant predictor of higher systolic and diastolic blood pressure 1 year after surgery. Amin et al18 also found a significant decline in postoperative DBP in the AHI .3 recurrence group. In a Greek population, Apostolidou et al50 found that SBP index increased significantly after surgery in nonobese children with residual OSA (postoperative AHI .1), and children with a complete resolution of OSA had a significant reduction in DBP postoperatively. Their results

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Table 6. Blood Pressure Changes between Obese and Nonobese Children Whose OSA Did Not Resolve after T&A.a NOB 2: Residual OSA after T&A (n = 15) Parameter Before PSG (nocturnal) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile After PSG (morning) SBP, mm Hg SBP index, mm Hg DBP, mm Hg DBP index, mm Hg SBP .90th percentile SBP .95th percentile DBP .90th percentile DBP .95th percentile

OB 2: Residual OSA after T&A (n = 21)

Group Comparison

Pre

Post

Pb

Pre

Post

Pb

P at Prec

P at Postc

P Interactiond

111.7 6 9.2 –5.6 6 9.2 71.2 6 6.5 –8.6 6 9.1 6 (40.0) 3 (20.0) 6 (40.0) 3 (20.0)

107.1 6 8.1 –10.4 6 7.0 63.8 6 10.4 –18.9 6 12.4 3 (20.0) 0 (0.0) 2 (13.3) 1 (6.7)

NS NS .049 .027 NS NS NS NS

111.0 6 7.8 –7.2 6 7.6 65.5 6 12.2 –16.7 6 14.3 6 (28.6) 3 (14.3) 6 (28.6) 2 (9.5)

112.9 6 8.2 –5.8 6 7.4 71.8 6 6.2 –8.6 6 8.6 9 (42.9) 3 (14.3) 7 (33.3) 3 (14.3)

NS NS .032 .034 NS NS NS NS

NS NS NS NS NS NS NS NS

NS (.058) NS (.077) .012 .007 NS NS NS NS

NS (.077) NS (.059) .001 .001 NS (.057) NS NS NS

114.2 6 6.8 –3.6 6 8.1 71.5 6 7.0 –8.1 6 9.5 5 (33.3) 4 (26.7) 7 (46.7) 3 (20.0)

106.5 6 8.8 –10.8 6 8.0 64.7 6 10.8 –17.9 6 12.8 3 (20.0) 1 (6.7) 4 (26.7) 1 (6.7)

.043 .036 NS NS NS NS NS NS

111.8 6 8.8 –6.5 6 8.0 67.8 6 11.7 –13.6 6 14.9 8 (38.1) 4 (19.0) 6 (28.6) 2 (9.5)

111.6 6 10.7 –7.0 6 9.0 71.6 6 8.0 –9.2 6 8.8 9 (42.9) 4 (19.0) 6 (28.6) 3 (14.3)

NS NS NS NS NS NS NS NS

NS NS NS NS NS NS NS NS

NS NS NS (.054) NS (.072) NS NS NS NS

NS (.070) NS (.069) .011 .011 NS NS NS NS

Abbreviations: DBP, diastolic blood pressure; NOB, nonobese; NS, not significant; OB, obese; OSA, obstructive sleep apnea; PSG, polysomnography; SBP, systolic blood pressure; T&A, adenotonsillectomy. a Data are presented as mean 6 standard deviation or number (percentage). b Wilcoxon signed rank test for continuous variables and McNemar test for categorical variables. c Mann-Whitney U test for continuous variables and Fisher exact test for categorical variables. d Interaction of ‘‘group by time’’ obtained from the generalized estimating equation for both continuous and categorical variables.

suggested that residual OSA may contribute to high blood pressure after surgery. Our data revealed elevated DBP in the obese group with residual disease yet observed that the nonobese children with residual disease had significantly lower SBP and DBP (Tables 3 and 4). But the group comparison did not reveal significance, meaning residual OSA did not have a significant effect on BP change. Interestingly, we also found once OSA was resolved, obese children improved the same in BP change as their nonobese counterparts (Table 5), which was not anticipated. However, nonobese children with residual OSA had a significant drop in DBP compared with obese children with residual disease (Table 6), suggesting obesity still had effect on BP change. The possible explanation of the results may be that the use of AHI 1 to determine residual OSA may not be severe enough to identify the blood pressure differences between the residual and resolved groups, and the effect of residual disease or obesity becomes insidious due to the limited sample size. Despite the above contributions, this study has certain limitations. First, this study did not recruit a control group. Although T&A is considered an effective treatment worldwide for pediatric OSA, a randomized trial by Marcus et al16 suggested that watchful waiting may also be a reasonable treatment option for pediatric OSA. Moreover, recent studies by Vlahandonis et al52,53 observed improvements in blood

pressure in children with spontaneously resolved obstructive sleep disorders during 4-year follow-up. Second, the sample size in this study was relatively small, making it difficult to thoroughly examine confounding factors other than age, sex, and AHI. Third, the follow-up period in this study was relatively short, warranting the need for studies on long-term cardiovascular outcomes.54 Fourth, the study adopted casual BP rather than a 24-hour ambulatory blood pressure monitoring system, whereas the latter is considered a more precise means of diagnosing hypertension.7,8,11,19 Finally, a lack of normal blood pressure values in Taiwanese children was of concern, explaining why the normative data of the US population were adopted in this study.44 Results of this study highlight the extent to which obesity adversely affects postoperative blood pressure in children with OSA. We recommend that future studies further clarify whether residual disease adversely affects postoperative blood pressure and yields different effects among obese and nonobese groups in children with OSA.

Conclusions This study demonstrates how pediatric obesity and OSA interact with each other and contribute to cardiovascular parameter changes. After T&A to treat OSA, nonobese children had more improvement in blood pressure than did

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obese children. Obese children with residual OSA even had a higher DBP after surgery. We recommend a long-term follow-up study with a 24-hour ambulatory blood pressure monitoring system to elucidate how obesity and residual OSA affect postoperative blood pressure parameter changes in children with OSA. Acknowledgments The authors thank staff of the Center of Sleep Disorders, National Taiwan University Hospital for their technical support. They also thank Hsing-Fen Lin for helping with the statistical method. The authors would like to thank two anonymous reviewers and the editors for their comments.

Author Contributions Yen-Lin Kuo, study concept and design, acquisition of data, drafting of the manuscript, critical revision of the manuscript for important intellectual content; Kun-Tai Kang, study concept and design, acquisition of data, analysis and interpretation of data, drafting of the manuscript, statistical analysis, critical revision of the manuscript for important intellectual content; Shuenn-Nan Chiu, acquisition of data, analysis and interpretation of data, statistical analysis, revising manuscript critically for important intellectual content; Wen-Chin Weng, acquisition of data, critical revision of the manuscript for important intellectual content; Pei-Lin Lee, acquisition of data, critical revision of the manuscript for important intellectual content; Wei-Chung Hsu, takes responsibility for the content of the paper, study concept and design, acquisition of data, analysis and interpretation of data, drafting of the manuscript, critical revision of the manuscript for important intellectual content.

Disclosures Competing interests: None. Sponsorships: None. Funding source: Grant MOST 103-2314-B-002-086 from Ministry of Science and Technology, R.O.C. (Taiwan).

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Blood pressure after surgery among obese and nonobese children with obstructive sleep apnea.

Treating obstructive sleep apnea in children is found to be associated with blood pressure decreases. However, exactly how adenotonsillectomy (T&A) af...
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