Abstract
We investigated changes in a utonomic nervous function in response to postural change of the upper gastrointestine by analysis of R-R intervals in electrocardiograms obtained during headup tilt (90°C HUT) and head-down tilt (-35°C HDT). Holter electrocardiograms were obtained from 12 persons at rest (horizontal prone position), during and after HUT and HDT, for frequency-domain analysis of change in the heart rate. During HUT and HDT, the high frequency spectral power (HF power; 0.15 to 0.40Hz), which reflects parasympathetic nervous activity, decreased to significantly less than those at rest or at rest after postural changes (p<0.05). During HUT and HDT, the low frequency spectral power (LF power; 0.04 to 0.15Hz), which reflects the balance of sympathetic and parasympathetic nervous activity, and the LF/HF ratio, which reflects sympathetic nervous activity, increased to significantly more than those at rest or at rest after postural changes (p<0.01). The present study suggests that enhanced sympathetic nervous activity and reduced parasympathetic nervous activity are evoked by postural changes of HUT and HDT. There are reports that enhanced sympathetic activity induces arrhythmias, while enhanced parasympathetic nervous activity has an antiarrhythmic effect. Therefore, we conclude that during upper gastrointestinal movements, a reduced angle or time of postural changes is necessary in elderly people and “highrisk” subjects to prevent cardiovascular complications.
