Effect of psychological stress on gastric motility assessed by electrical bio-impedance

Abstract

Aim: To evaluate gastric motility using electrical bio-impedance (EBI) and gastric changes as a result of stress induced by psychological tests.

Methods: A group of 57 healthy women, aged 40-60 years, was recruited, and a clinical history and physical examination were performed. The women were free from severe anxiety, chronic or acute stress, severe depression, mental diseases and conditions that affect gastric activity. The women were evaluated under fasting conditions, and using a four-electrode configuration, the gastric signals were obtained through a BIOPAC MP-150 system. The volunteers were evaluated using the following paradigm: basal state, recording during the Stroop Test, intermediate resting period, recording during the Raven Test, and a final resting period. We analyzed the relative areas of the frequency spectrum: A1 (1-2 cpm), A2 (2-4 cpm), A3 (4-8 cpm), and A4 (8-12 cpm), as well as the median of area A2 + A3. The data were analyzed by an autoregressive method using a Butterworth filter with MatLab and Origin. Analysis of variance (ANOVA) and Friedman ANOVA (for nonparametric variables) were performed; in addition, pairs of groups were compared using the T dependent and Wilcoxon T tests.

Results: The results of the main values of area A2 were not significantly different comparing the five steps of the experimental paradigm. Nevertheless, there was a tendency of this A2 region to decrease during the stress tests, with recuperation at the final resting step. When an extended gastric region was considered (1-4 cpm), significant differences with the psychological stress tests were present (F = 3.85, P = 0.005). The A3 region also showed significant changes when the stress psychological tests were administered (F = 7.25, P < 0.001). These differences were influenced by the changes in the adjacent gastric region of A2. The parameter that we proposed in previous studies for the evaluation of gastric motility by electrical bio-impedance (EBI) was the median of the area under the region from 2 to 8 cpm (A2 + A3). The mean values of these frequencies (median of the A2 + A3 area) with the stress test showed significant changes (F = 5.5, P < 0.001). The results of the Wilcoxon T test for the A4 area parameter, which is influenced by the breathing response, changed significantly during the Raven stress test (P < 0.05).

Conclusion: We confirm that the gastric response to acute psychological stress can be evaluated by short-term EBI.

Keywords: Bio-impedance; Gastric motility; Psychological stress.

Figure 1

Raw data of the gastric bio-impedance signal showing mainly the breathing oscillations (fast oscillations) and the gastric contribution (2-4/min), which are shown by the dashed curve. AU: Arbitrary units.

Figure 2

Typical frequency spectrum of the electrical bio-impedance gastric signal. The three curves show the typical changes during the tests (Stroop Test in this example): series 1: solid line, before the test; series 2: dotted line, during the test; series 3: dashed line after the test. AU: Arbitrary units.

Figure 3

Changes in the relative area under the frequency spectrum of the gastric electrical bio-impedance signal (mean ± SE). A: From 2 to 4 cpm; B: From 1 to 4 cpm; C: From 4 to 8 cpm; D: Median of the area from 2 to 8 cpm. Basal: Basal gastric motility recording; Stroop: Recording during the Stroop Test; IRP: Intermediate resting period; Raven: Recording during the Raven test; FRP: Final resting period.

Figure 4

Changes in the relative area under the frequency spectrum of the gastric electrical bio-impedance signal from 8 to 12 cpm (median and interquartile range). Basal: Basal gastric motility recording; Stroop: Recording during the Stroop Test; IRP: Intermediate resting period; Raven: Recording during the Raven Test; FRP: Final resting period.