Improved detection of obstructive events in childhood sleep apnoea with the use of the nasal cannula and the differentiated sum signal

The efficacy of the nasobuccal thermistor (NT) was compared with the nasal pressure cannula (NC) and the calibrated, time-differentiated respiratory inductance plethysmography sum signal (DS) in the detection of obstructive events in children during polysomnography (PSG). The overnight PSG of 20 consecutive referrals were selected for analysis. Obstructive events were scored in each study three times by one operator using a blinded procedure whereby either the NT, the NC or the DS was visible. The standard PSG channels were also visible. SPSS software was used for statistical analysis. Twenty patients aged 5 weeks to 16 years were studied. Agreement in obstructive apnoea-hypopnoea index (OAHI) was highest between the NT and NC, and the NC and DS. The NC signal was significantly more likely to be uninterpretable than the NT (P = 0.02) and this did not correlate with age. Event detection by the NT was significantly improved by the addition of either the NC (P = 0.01) or the DS (P = 0.001), while the NC stood alone unless the DS was added (P = 0.02). There was no significant difference in OAHI by the NC versus the DS. The NC detected significantly more OA than the NT or the DS (P = 0.04), while the DS trended towards detecting more OH. There was no significant difference in OAHI between any combination pair. The nasal cannula and differentiated sum signal perform better as measures of paediatric airflow than the NT. To optimize the detection of obstructive events in children we recommend using at least one, if not both these methods in paediatric sleep laboratories.