Analysis of airflow indices in paediatric respiratory disorders

Abstract

AimDuchenne Muscular Dystrophy (DMD) and Prader-Willi syndrome (PWS) are complex congenital disorders in which sleep disordered breathing (SDB) typically develop, and this impacts normal growth and neurological development. Due to the slow progression of SDB pathology and the lack of correlation between SDB pathology and daytime clinical symptoms, these patients are often only actively treated after SDB is fully established. This study aims: (1) to determine whether there are changes in breath timing and breath shape (morphology) during sleep in these paediatric respiratory disorders when compared with healthy children; and (2) whether there is an association between physiological markers of disorder progression with these indices of breath timing and shape. MethodsA retrospective cohort of 13 patients with DMD and 11 patients with PWS whom had at least three sequential overnight polysomnograms and 27 healthy controls (2-17 years) were identified from a clinical database. The nasal pressure signal in at least two tenminute segments of stage 2 non-rapid eye movement (NREM) sleep for each patient was extracted from each retrospective polysomnogram. Each breath was automatically segmented into inspiratory and expiratory phase using a customised algorithm, and these were used quantified using three categories of indices: (1) Timing indices including total breath time (Ttot) and fractional inspiratory time (FIT) (mean and standard deviation, SD);(2) Linear shape descriptors (skewness, kurtosis and variance); and (3) Non-linear shape descriptors (line morphology, length -'flatness'and variability). In addition, standard physiological markers of disease progression were extracted from the polysomnogram report: total apnoea-hypopnoea index (AHI), body-mass index (BMI), mean SpO2 and mean CO2. Indices of breath timing and shape were compared between the disorder cohorts and healthy controls; and the changes in indices over years for cohorts were compared to standardphysiological measures to determine if there was any association with disorder progression.