Diminished pulse-respiration-coupling in depressed patients

The research on autonomic dysfunctions plays an increasing role in clinical psychophysiology. Our approach was not to measure peripheral autonomic activity but to evaluate parameters that mirror central autonomic regulation. Pulse-respiration coupling is such a parameter closely connected to the central autonomic state. We recorded heart-rate and respiration from 42 patients with Major Depression and their age- and sex matched controls. 23 of the patients were unmedicated and 19 were medicated with tricyclic antidepressants (equivalent to 150 mg imipramine). All inspiration-onsets were plotted synchronized to the previous it-peak to detect the degree of pulse-respiration-coupling. Histograms of the inspiration-onsets were computed and the amount of coupling was compared between the groups. We observed that pulse-respiration-coupling was diminished in medicated as well as in unmedicated patients compared to their controls. The shapes of the average histograms were similar in the two control groups as well as in the two patient groups, but were different between patients and controls. Medication obviously has less influence on the shape of the histogram than the disorder itself. The assessment of higher order coordination of cardio-respiratory functions through pulse-respiration coupling allows to demonstrate autonomic differences between depressed patients and normal controls. The description of autonomic regulation of cardiorespiratory parameters may facilitate the assessment of the role of the central autonomic state regarding autonomic dysfunctions in psychiatric patients.