Obstructive hypopnea and gastroesophageal reflux as factors associated with residual obstructive sleep apnea syndrome.

Objective: The mechanism of persisting obstructive sleep apnea (OSA) after adenotonsillectomy is not fully explained. The purpose of this study was to evaluate factors associated with residual OSA. The primary outcome measures were metabolic tests and polysomnographic respiratory indices in children with residual disease compared with children who were diagnosed with OSA but were untreated. Secondary outcome measures were acid gastroesophageal reflux indices recorded parallel to the sleep study.

Methods: In the one-year study consecutive series of patients with sleep disordered breathing hospitalized in a tertiary pediatric center were evaluated. Following the study protocol a sleep interview, physical examination, metabolic blood tests (serum leptin and the homeostasis model assessment index for insulin resistance, HOMA-IR) and an overnight polysomnography with pH-metry recording were performed. Children diagnosed with OSA were analyzed in two groups: I - residual OSA (after surgery), II - non-residual OSA (newly diagnosed). Logistic regression analysis was applied to obtain significant risk factors for prediction of OSA.

Results: Fifty-seven children (mean age ± SE, 6.9 ± 0.5 years; 66.7% boys) met the inclusion criteria and were enrolled in the study as residual (n=19) or non-residual OSA (n=38). The groups differed significantly in mean oxygen saturation, SpO₂ (94.3% vs. 96.2%; p=0.018 respectively), in the Apnea Hypopnea Index, (20.6/h vs. 9.1/h; p<0.03), the number of respiratory arousals with desaturation (2.2/h vs. 0.8/h; p<0.03); mean intraluminal esophageal pH (5.36 vs. 5.86; p=0.007) and the Reflux Index (9.61% vs. 4.35%; p=0.003). The groups did not differ in total sleep time, tonsil size, BMI z-score and blood metabolic indices. Logistic regression analysis showed that residual OSA was significantly predicted by two polygraphic findings: the obstructive hypopnea index (OR 1.15; 95% CI 1.02-1.28; p=0.014) and by the Reflux Index (OR 1.01; 95% CI 1.00-1.34; p=0.042).

Conclusions: 1. Obstructive hypopneas, rather than obstructive apneas, persist after adenotonsillar surgery resulting in residual OSA. 2. Children with residual OSA are at higher risk of acid gastroesophageal reflux and should be evaluated for gastroesophageal reflux disease.