Polysomnography Parameters Assessing Gas Exchange Best Predict Postoperative Respiratory Complications Following Adenotonsillectomy in Children With Severe OSA.

STUDY OBJECTIVES: Adenotonsillectomy (AT) is the treatment of choice for obstructive sleep apnea (OSA) in children with adenotonsillar hypertrophy. Severe OSA, identified by the apnea-hypopnea index (AHI), is a risk factor for surgical complications and AHI thresholds are used by surgeons to decide elective postoperative hospital admissions. The objective of this study was to identify the prevalence of surgical complications of AT in children with severe OSA and determine their association with specific parameters of polysomnography (PSG). METHODS: Retrospective evaluation of respiratory and nonrespiratory complications in children undergoing AT for severe OSA was performed. Events were then compared to several individual PSG indices. PSG indices included classic parameters such as AHI, and obstructive apnea indexes (OAI) as well as gas exchange parameters including the oxygen desaturation index (ODI), lowest oxyhemoglobin saturation (lowest SpO2), peak end-tidal CO2 (peak ETCO2), the percentage of the total sleep time (%TST) with ETCO2 > 50 mmHg (%TST ETCO2 > 50 mmHg) and oxygen saturation < 90% (%TST O2 < 90%). RESULTS: A total of 158 children were identified with severe OSA. Major respiratory complications occurred in 21.5% and were only associated with the ODI (P = .014), lowest SpO2 (P = .001) and %TST O2 < 90% (P < .001). Minor respiratory complications occurred in 19.6% and these were not associated with any PSG parameters. Major nonrespiratory complications occurred in 4.4% and also were not associated with any PSG parameters; however, minor nonrespiratory complications occurring in 37.3%, and were associated with %TST O2 < 90% (P < 0.001). CONCLUSIONS: PSG measures of gas exchange are strongly associated with postoperative complications of AT and are better suited for postoperative planning than classic indices such as AHI. CITATION: Molero-Ramirez H, Tamae Kakazu M, Baroody F, Bhattacharjee R. Polysomnography parameters assessing gas exchange best predict postoperative respiratory complications following adenotonsillectomy in children with severe OSA. J Clin Sleep Med. 2019;15(9):1251-1259.

Nitric oxide production by monocytes in children with OSA and endothelial dysfunction.

OSA (obstructive sleep apnoea) is associated with a higher risk for alterations in post-occlusive hyperaemia, an eNOS (endothelial NO synthase)-dependent endothelial response. However, since not all children manifest endothelial dysfunction, we hypothesized that differences in circulating monocyte subsets and NO production may underlie the vascular phenotype in paediatric OSA. Matched pre-pubertal children with OSA with abnormal endothelial function (OSAab) and with normal endothelial function (OSAn), and controls (CO) were recruited. Peripheral blood mononuclear cells were subtyped into CD14+ and CD16+ cells, and NO production was assessed using flow cytometry. Endothelial dysfunction was defined as Tmax (time to reach maximal reperfusion)>45 s by laser Doppler flowmetry. A total of 11 OSAab, 12 OSAn and 12 CO-matched children completed the study. The OSAab group had increased CD16+ and decreased CD14+ cell numbers. They also had increased CX3CR1 (CX3C chemokine receptor 1) expression in CD16+ monocytes (P<0.01). Furthermore, monocytes from the OSAab group exhibited overall reduced NO production (787±71 compared with 1226±229 and 1089±116 median fluorescence intensity in the OSAn group and CO children respectively; P<0.01). Significant bivariate associations emerged between NO production, monocyte subsets, CX3CR1 in CD16+ monocytes, the CD14+/CD16+ ratio and Tmax. Thus OSA in children is associated with increased numbers of pro-inflammatory monocytes and reduced NO production in circulating monocytes that are closely associated with endothelial function.

Circulating adropin concentrations in pediatric obstructive sleep apnea: potential relevance to endothelial function.

OBJECTIVE: To test the hypothesis that concentrations of adropin, a recently discovered peptide that displays important metabolic and cardiovascular functions, are lower in obstructive sleep apnea (OSA), especially when associated with endothelial dysfunction. STUDY DESIGN: Age-, sex-, and ethnicity-matched children (mean age, 7.2 ± 1.4 years) were included into 1 of 3 groups based on the presence of OSA in an overnight sleep study, and on the time to postocclusive maximal reperfusion (Tmax >45 seconds) with a modified hyperemic test. Plasma adropin concentrations were assayed using a commercial enzyme-linked immunosorbent assay kit. RESULTS: Among controls, the mean morning adropin concentration was 7.4 ng/mL (95% CI, 5.2-16.3 ng/mL). Children with OSA and abnormal endothelial function (EF) (OSA(+)/EF(+) group) had significantly lower adropin concentrations (2.7 ± 1.1 ng/mL; n = 35) compared with matched controls (7.6 ± 1.4 ng/mL; n = 35; P < .001) and children with OSA and normal EF (OSA(+)/EF(-) group; 5.8 ± 1.5 ng/mL; n = 47; P < .001). A plasma adropin concentration <4.2 ng/mL reliably predicted EF status, but individual adropin concentrations were not significantly correlated with age, body mass index z-score, obstructive apnea-hypopnea index, or nadir oxygen saturation. Mean adropin concentration measured after adenotonsillectomy in a subset of children with OSA (n = 22) showed an increase in the OSA(+)/EF(+) group (from 2.5 ± 1.4 to 6.4 ± 1.9 ng/mL; n = 14; P < .01), but essentially no change in the OSA(+)EF(-) group (from 5.7 ± 1.3 to 6.4 ± 1.1 ng/mL; n = 8; P > .05). CONCLUSION: Plasma adropin concentrations are reduced in pediatric OSA when endothelial dysfunction is present, and return to within normal values after adenotonsillectomy. Assessment of circulating adropin concentrations may provide a reliable indicator of vascular injury in the context of OSA in children.

Obstructive sleep apnea in children is associated with severity-dependent deterioration in overnight endothelial function.

BACKGROUND: Restorative sleep is expected to promote improved endothelial function (EF) in the morning compared to the evening. However, in adults with obstructive sleep apnea (OSA) EF is not only adversely affected, but it worsens during the night. Data in pediatric OSA are scarce, and overnight changes have not been explored. Therefore, we sought to examine potential associations between pediatric OSA and overnight changes in EF. METHODS: 59 habitually snoring children with various degrees of sleep-disordered breathing (age range, 4-16 years) underwent EF assessment (reactive hyperemia test by EndoPAT, Itamar Medical, Israel) in the evening before and the morning after an overnight polysomnography (PSG). Two brachial occlusion periods (1 min and 5 min) also were tested. Potential associations between evening-to-morning changes in EF and polysomnographic parameters were explored. RESULTS: Evening-to-morning changes in children with OSA displayed severity-dependent deterioration of EF, and occlusions lasting 1 or 5 min during the reactive hyperemia test yielded similar findings. CONCLUSIONS: In children deterioration in EF during the night significantly correlated with the severity of OSA. Furthermore, the reactive hyperemia test can be reliably performed with only 60 seconds of arterial flow occlusion in children. These findings support our hypothesis that similarly to adults, sleep apnea in children results in endothelial dysfunction (ED). We speculate that pediatric OSA is less commonly associated with cardiovascular complications possibly due to the shorter duration of the syndrome.