Background Diaphragm surface EMG (sEMGdi) has been proposed as a possible tool to assess respiratory effort during sleep in adults. Previous studies suggest posture, stages of sleep, and age may affect the magnitude of respiratory effort in adults. Aim To assess possible factors which may affect respiratory effort as represented by sEMGdi during sleep in children. Methods Excerpts from routine overnight sleep studies in children were exported from the Compumedics Profusion 3 system to the Spike2 system for analysis of sEMGdi. Statistical analysis were performed to determine the relationship between sEMGdi and age; position of sleep (supine, prone, right and left lateral); and stages of sleep (light, deep, REM sleep). Results sEMGdi data from the sleep studies of 40 children aged 4.05 years (median; IQR 2.75-6.04) were analysed. Univariate analyses performed confirmed age as a statistically significant negative predictor of sEMGdi (p=0.03). Position of sleep was not a significant predictor of sEMGdi (p=0.83). Repeated ANOVA measures showed sEMGdi is significantly greater during REM sleep (6.83uV in REM, 5.32uV in deep sleep (p < 0.005), 5.80uV in light sleep (p=0.007))

. Conclusion Respiratory effort in children, as estimated by sEMGdi is affected by age and stages of sleep. Sleeping position did not affect sEMGdi significantly.