Introduction:
Nocturnal oximetry is used to screen for obstructive sleep apnoea (OSA). The McGill Oximetry Score (MOS) grades OSA on oximetry but relies on a 6-hour minimum trace duration. A recent study suggests that one night is sufficient. We wanted to explore the additional benefit of using ≥4 hours minimum tracing recorded over 3 separate consecutive nights as a cut off aiming to reduce the number of inadequate studies.
Methods:
A retrospective observational study was conducted of overnight oximetry traces over 3 nights from suspected OSA children referred to the Royal Belfast Hospital for Sick Children. We used ≥4, ≥5 and ≥6 hours of continuous data to define technically adequate oximetry duration. Traces <6 hours’ duration were only deemed as adequate if they had an abnormal trace (MOS >1).
Results:
330 patient oximetry recordings were studied. Taking ≥6 hours of good oximetry trace as adequate over any of the 3 nights’ reduced the number who had no technically adequate tracing recorded from 16% to 5.7%. Similarly, when ≥5 hours of good trace was taken inadequate traces fell from 12.4% to 3%. Taking ≥4 hours of good trace reduced the numbers of inadequate traces from 9% to 1.5%.
Conclusion:
Reducing the time required for an adequate trace and using three consecutive nights decreased the number of inadequate studies when the result was abnormal. This study suggests that less than six hours may be technically adequate (in situations of MOS>1). A study of 4 hours’ duration may be scored but whether the result is reliable and should be acted upon if abnormal needs careful consideration.