1. Introduction
Down syndrome (DS), or Trisomy 21 is the most common chromosomal disorder observed worldwide in live-born children 1. Occurrence rates vary widely globally, however, the rate of DS correlates with rising maternal age, which has been steadily increasing since the 1970’s 2. Reported DS birth rates range between 13.6-22.0/10,000 live births 2,3. In Ireland, the most recent figures demonstrate that 1 in 444 live-born babies have DS 2.
DS is characterised by a distinctive collection of phenotypic features in combination with developmental delay and intellectual impairment1. The phenotypic characteristics of DS are predominated by altered craniofacial anatomy, where mid-facial and mandibular hypoplasia, relative macroglossia, a posteriorly placed tongue, hypotonia, as well as, lymphoid, particularly adenotonsillar, hypertrophy culminate in a small and narrow upper airway4. The aforementioned phenotypic features in combination with the increased prevalence of congenital airway defects, such as laryngomalacia, tracheobronchomalacia, tracheal compression and subglottic stenosis predispose children with DS to obstructive sleep apnoea (OSA) 5,6. The reported prevalence of OSA in the DS paediatric population ranges from 30-66.4%, compared with 0.7-2% in the general paediatric population 7,8. Furthermore, OSA is more severe within the DS population, particularly in the younger age groups 7. There are numerous co-morbidities associated with DS which have been shown to be responsible, at least in part, for the severity of OSA within the DS population, including a predisposition to upper respiratory tract infections, hypothyroidism, gastro-oesophageal reflux (GORD) and obesity9-13. Within DS there is a propensity for congenital cardiac defects to affect the respiratory system, and vice versa, in which respiratory disease, including OSA, affects the heart and the pulmonary vasculature 14. OSA-induced recurrent hypoxaemia has been shown to alter pulmonary vessel resistance leading the development, persistence and recurrence of pulmonary hypertension, right-sided heart failure and cor pulmonale 14-16. Sleep disordered breathing has also been linked to enhanced sympathetic drive as well as worse left ventricular diastolic function17.
The management of OSA within the DS population involves a multidisciplinary approach. Upper airway surgery remains the preferred initial management for suitable candidates in moderate to severe OSA18. However, surgery is not always effective and residual OSA post-adenotonsillectomy has been reported to be as high as 70% 19-22. In such children, non-invasive ventilation (NIV) in the form of positive airway pressure, whether that be as continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP), is the mainstay of OSA treatment 23.
Effective management of OSA within the DS population is of the utmost importance. Poor OSA management has been associated with worsening cardiovascular issues, such as pulmonary hypertension, cardiovascular disease in adulthood, culminating in increased morbidity and mortality24-26. Moreover, the treatment of upper airway obstruction has been shown to reverse pulmonary hypertension26. The DS cohort has also been shown to be more susceptible to the negative impacts of sleep disturbances on neurocognitive and behavioural problems 27.
There are conflicting results within the current body of literature of the efficacy and adherence to domiciliary NIV within the paediatric DS population. Previous studies have suggested poor tolerance and compliance to NIV within this cohort 23. In this study we hypothesised that poor adherence is a key issue undermining the effectiveness of NIV in the DS population. The aim of this study was to assess adherence over time, as well as, the efficiency of NIV delivery to a paediatric DS cohort.