Overnight pulse oximetry for evaluation of sleep apnea among children with trisomy 21

Abstract

Study objectives: For children with trisomy 21, polysomnography at age 4 to assess obstructive sleep disordered breathing (OSDB) is the standard of care. Oximetry alone has been used to screen for disease among children without trisomy 21. This study evaluates the potential usefulness of oximetry scoring in diagnosing OSDB among children with trisomy 21.

Methods: A McGill oximetry score from 1 to 4 was derived from a full overnight PSG done on 119 consecutive pediatric subjects with trisomy 21. Most were referred to the sleep laboratory because of suspicion for OSDB. Oximetry scorers were blinded to the child's full PSG and clinical course. Results of the complete PSG were then compared to oximetry scores.

Results: Obstructive apnea-hypopnea index (OAHI) was ≥ 2.5 for 50% of all subjects. Fifty-nine subjects (49.6%) had McGill Score 1 ("inconclusive"); median OAHI was 1.0 (IQR 0.4-3.3). McGill Score was 2 for 43 subjects (36.1%); median OAHI was 4.5 (IQR 1.3-8.8). Seventeen subjects (14.3%) had McGill Scores of 3 or 4; median OAHI was 16.1 (IQR 9.3-45.5, range 2.1 to 101.1). Ten percent of subjects had a considerable number of central events (≥ 2.5 respiratory events/h but OAHI < 2.5), including 7 with McGill Score 2.

Conclusions: In a retrospective cohort of children with trisomy 21, McGill oximetry scores of 3 or 4 reliably identified patients with marked OSDB. The possibility of central apneas causing hypoxemia must be considered in those with McGill Score 2. With these caveats, oximetry screening should be considered when developing streamlined protocols for early intervention to treat OSDB in this population.

Keywords: central apnea; obstructive sleep apnea; pulse oximetry; trisomy 21.

Figure 1. Flow chart describing 119 consecutive pediatric subjects with trisomy 21 who had McGill oximetry scoring on PSG.

PSG, polysomnogram; CPAP, continuous positive airway pressure; O₂, supplemental oxygen.

Figure 2. Total, obstructive and central apnea-hypopnea indices by assigned McGill score.

Box plots of apnea-hypopnea indices for each McGill score with median (horizontal line), 25th and 75th interquartile values (box ends), and total range without outliers (whiskers). Circles represent the outliers of 1.5-3 times the interquartile range (box length). Asterisks represent extreme outliers 3 times the box length. (A) Positive correlation between McGill Oximetry Score and total apnea-hypopnea index. Subjects with higher McGill scores had higher total AHI, Spearman correlation rho = 0.65, p < 0.001. (B) Positive correlation between McGill oximetry score and obstructive apnea-hypopnea index. Subjects with higher McGill Scores had higher OAHI, Spearman correlation rho = 0.60, p < 0.001. (C) Positive correlation between McGill score and central apnea index, Spearman correlation, rho = 0.25, p = 0.006. Extreme outlier for one subject with central apnea index of 35.2 excluded from this figure for purposes of the image scale.

Figure 3. BMI values by assigned McGill Score for all subjects and for those with and without prior adenotonsillectomy.

Box plots of BMI values for each McGill score with median (horizontal line), 25th and 75th interquartile values (box ends), and total range (whiskers). Circles represent the outliers of 1.5-3 times the interquartile range (box length). Asterisks represent extreme outliers 3 times the box length. (A) Positive correlation of McGill score with BMI. Patients with trisomy 21 with higher assigned McGill scores had larger BMI (Spearman correlation rho = 0.36, p < 0.001). (B) BMI with McGill oximetry score for those who had a prior adenoidectomy and/or tonsillectomy compared to those who did not.