Summary: Investigation of respiratory control requires an accurate measuring system which does not itself after the pattern of respiration. We have used a transthoracic impedance pneumograph to investigate the effects of application of a face mask plus pneumotachograph or the face mask rim alone on tidal volume and respiratory frequency in 10 sleeping term infants aged 1–4 days. Application of the face mask rim led to a small but significant fall in respiratory frequency, 12% in quiet sleep (QS) and 17% in rapid eye movement (REM); with the application of the complete face mask plus pneumotachograph, changes were 10% and 14% in QS and REM, respectively. These changes were accompanied by rises in tidal volume of similar magnitude (15%, 11% in QS and 21%, 17% in REM, respectively). These results suggest that the change in respiratory pattern is due mainly to trigeminal stimulation rather than respiratory loading; thus, recordings obtained by methods utilising face masks cannot be considered to represent undisturbed respiration, for at least the first 5 min of recording.
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