Answers

Short answers

1. The abnormalities are detailed in fig 2.

View larger version (45K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 2 Overnight sleep study showing abnormalities in transcutaneous carbon dioxide (CO2), oxygen saturation (SaO2), and heart recordings

2. Sleep disordered breathing (obstructive sleep apnoea).

3. The intervention, which improved sleep quality (fig 3), would have been adenotonsillectomy or institution of non-invasive ventilation.

View larger version (44K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 3 Overnight sleep study showing improvement in abnormalities after treatment. Mean oxygen saturation (SaO2) is improved, with a lower baseline transcutaneous carbon dioxide (CO2) and obliteration of CO2 peaks

2. Sleep disordered breathing (obstructive sleep apnoea)
Figure 2 shows three discrete periods of desaturation associated with tachycardia, and on two of these occasions high carbon dioxide values. Such a pattern commonly occurs in REM sleep, when a fall in skeletal muscle tone of the chest wall and upper airway occurs.

Sleep disordered breathing has been reported in 45-79% of children with Down’s syndrome,^{1 2 3 4 5} although one study of 28 patients found no such association.⁶ Several factors predispose these children to this condition, including hypotonia of the upper airways and chest wall, macroglossia, large maxillary size, obesity,⁷ and male sex.⁴

3. Treatment
Children with Down’s syndrome and upper airway pathology are treated with adenotonsillectomy or institution of non-invasive ventilation. These children are difficult to manage, however, because adenotonsillectomy has a high failure rate,⁸ and instituting non-invasive ventilation or oxygen therapy is difficult in a child with limited understanding. This child had already had adenotonsillectomy so he was given non-invasive ventilation.

Although adenotonsillectomy may relieve obstruction,^{8 9} in many cases the accompanying upper airway hypotonia seen in Down’s syndrome leads to ongoing upper airway obstruction after surgery. A recent retrospective study of polysomnographic analyses in children with Down’s syndrome and sleep disordered breathing found that abnormal breathing persists in 48% of children after adenotonsillectomy.⁸ When children who had hypoxia and hypercapnia before surgery were considered separately, 67% of them still had abnormal polysomnographic studies after surgery.

Non-invasive mask ventilation (bilevel positive airway pressure or continuous positive airway pressure) can relieve this obstruction, but it can be challenging to establish in young children with Down’s syndrome—for parents and medical staff alike. We have found that input from psychology, play therapy, and physiotherapy workers can be helpful when introducing a new treatment in patients whose understanding may be limited.

A community based study of 995 children showed that hypoxia (SaO₂ nadir below 93%) predicts impaired mathematical ability.¹⁰ Cognitive functioning seems to improve after adenotonsillectomy in children with sleep disordered breathing,¹¹ as does school performance.¹² Gozal studied 297 children ranked in the lowest 10th of their school class.¹² Using nocturnal CO₂ and SaO₂ measures, he identified 54 children with sleep associated abnormalities of gas exchange. Of the 24 who had adenotonsillectomy, only two remained in the lowest 10th the next year, whereas those who did not have surgery did not improve, and neither did those with poor academic performance and normal gas exchange.¹² Improvements in behaviour and quality of life are also reported after adenotonsillectomy.¹³

Successful treatment of upper airway obstruction in Down’s syndrome can thus have a positive effect on learning. Non-invasive mask ventilation should be considered if surgery fails to correct breathing.¹⁴ However, the only published data on the use of non-invasive ventilation in Down’s syndrome is a case report of successful treatment.¹⁵ Over the past two years, we have evaluated seven children, aged 3 months to 14 years, with Down’s syndrome and refractory sleep disordered breathing; we have successfully instituted non-invasive ventilation in six of them and used nasal cannula oxygen to ameliorate hypoxia in the seventh.

Successful treatment of sleep disordered breathing may lift non-syndromic children out of the bottom tier of the educational strata.¹² Such an effect on learning in children with Down’s syndrome may enable these children to live independently rather than under supervision, although no evidence exists to evaluate this hypothesis.

Cite this as: BMJ 2008;337:a1229