INTRODUCTION: Nocturnal pulse oximetry can be used to screen for obstructive sleep apnoea (OSA) using the McGill Oximetry Score (MOS). The MOS has a time threshold for a technically adequate study of 6 hours. It has been suggested that one night of oximetry is sufficient to screen for OSA using the MOS.
AIMS: (1) To evaluate night-to-night variation of the MOS. (2) To determine the impact of recording three nights of oximetry on the screening yield for OSA. (3) To explore whether useful MOS data are discarded when a threshold of 6 hours of oximetry recording is used.
METHODS: A retrospective study of nocturnal pulse oximetry done at home over three consecutive nights in paediatric patients with suspected OSA. Studies were scored (MOS) using thresholds of ≥6 and ≥4 hours of recording.
RESULTS: A total of 329 patients were studied. MOS scores over three nights showed only fair to moderate agreement. On the first night 126 patients (38%) screened positive for OSA. When three nights of oximetry were done 195 patients (59%) screened positive on at least one of the nights. There were 48 patients with studies of between 4 and 6 hours duration on one or more nights. If these studies are scored 20 patients (42%) would screen positive for OSA on at least one night based on scoring these studies alone.
CONCLUSION: One night of oximetry screening may not be sufficient to screen for OSA. Lowering the time threshold to ≥4 hours may increase the screening capability of nocturnal oximetry.