P139 What threshold of total sleep time of hypercapnia should define hypoventilation in children with neuromuscular disorders?

Abstract

Abstract Background there are numerous definitions of hypoventilation, the most commonly used for children being pCO₂ >50mmHg >25% total sleep time. There are concerns that a total sleep time threshold of >25% is not sensitive enough in children and individuals with neuromuscular disorders. Alternative thresholds of 2%, 5% and 10% total sleep time have been suggested. Methods the relationship between percentage of total sleep time with pCO₂ >50mmHg and the presence of hypoventilation (determined by physician diagnosis) was examined in a small exploratory analysis of children with neuromuscular disorders. ROC curves were constructed to determine the impact of changing cut-off thresholds for total sleep time with pCO₁ >50mmHg to define hypoventilation. Results the mean percentage of total sleep time that pCO₂ >50mmHg was higher for the studies with hypoventilation (50% vs.10%). The mean difference (40%) was not statistically significant, likely due to the small number of studies (n=6) with hypoventilation. The AUC for percentage of total sleep time with pCO₂ >50mmHg was 0.808 (p=0.035, CI 0.6 to 1.0). For thresholds of total sleep time with pCO₂ >50mHg to define hypoventilation of 20% and 27%, sensitivity was 50%. For thresholds of 11%, 5% and 3%, sensitivity was 67%, 100% and 100% respectively. Conclusions in this study the upper limit of total sleep time with pCO₂ >50mmHg in children with neuromuscular disorders without hypoventilation was 10%. Thresholds lower than 25% of total sleep time with pCO₂ >50mmHg to define hypoventilation had higher sensitivity for diagnosing hypoventilation in this population.