2.3 Polysomnography and NIV domiciliary data
Polysomnography (PSG) was performed on all children overnight in the hospital sleep laboratory using the Philips Respironics Alice 6TM PSG system (Koninklijke Philips N.V., Netherlands) with Transcutaneous Capnography Radiometer TOSCA 500TManalyser and scored with the aid of Philips Respironics G3TM software according to the American Academy of Sleep Medicine (AASM) paediatric criteria 28,29.
NIV therapy was prescribed by a treating paediatric respiratory consultant, based on the PSG findings and symptomatology. NIV therapy was commenced using a previously prescribed pathway with the support of an NIV clinical nurse specialist 30.
Domiciliary NIV data was collected via secure memory cards and modem technology. Only children with downloadable data available for at least one year were included in the analysis. Data recorded in this study included parameters relating to usage, function and clinical outcomes.
The usage parameters included pressure (cmH2O), humidity, percent days used, percentage days used >4hrs and average use per night. Functional measures include system leak (L/min) and percentage of time with excess leak (%). Clinical outcomes were measured using apnoea–hypopnoea index (AHI).