Nasal capnography in children: automated analysis provides a measure of obstruction during sleep

A detailed analysis was made of nasal capnograms obtained from sleeping children with differing degrees of sleep-induced respiratory obstruction, the severe form being known as obstructive sleep apnoea. Clinical observations of these children were compared with analyses of nasal capnography data. During periods when the degree of obstruction was consistent throughout the first hour of sleep, the means and coefficients of variation of several parameters, derived from the capnograms were calculated. The coefficients of variation showed a close relationship to the degree of obstruction. In comparison, measures of end-tidal carbon dioxide concentration proved to be a very insensitive index of the degree of obstruction. The conclusion is that the usefulness of nasal capnography in predicting and grading obstruction can easily be extended by the use of statistical measures of dispersion and that this concept warrants further work.