Acupuncture at the Neiguan (P6) point has been shown to lessen nausea and vomiting which are related to vagal modulation. This study investigated whether acupuncture at the P6 point could improve vagal modulation by using heart rate variability analysis. We compared the heart rate variability measures of 39 subjects receiving acupuncture at the P6 point, 38 subjects receiving sham acupuncture, and 34 subjects receiving no treatment at all. The normalized high-frequency power was used as the index of vagal modulation, and the low-/high-frequency power ratio was used as the index of sympathovagal balance. The normalized high-frequency power after acupuncture increased significantly from 28.1 +/- 12.6 nu (mean +/- SD) to 30.7 +/- 14.1 nu in the P6 acupuncture group, but not in the sham acupuncture (30.6 +/- 13.7 nu versus 31.8 +/- 13.8 nu) or no-treatment group (30.1 +/- 15.0 nu versus 30.1 +/- 15.7 nu). In both the P6 and sham acupuncture groups, the mean RR interval (the intervals between consecutive R waves in the electrocardiogram) increased significantly after acupuncture. In the no-treatment group, there was no statistical difference in all heart rate variability measures in the initial and later sessions. In conclusion, acupuncture at the P6 point can increase vagal modulation of the subjects. This result may be helpful in the understanding of the mechanism underlying the effect of acupuncture or acupressure at P6 on the lessening of nausea and vomiting in clinic.

The resting autonomic nervous function of COPD patients is not different from that of normal controls. Though the degree of airway narrowing is not related to the cardiac autonomic nervous function, chronic hypoxemia can lead to enhanced cardiac vagal activity and depressed sympathetic activity in COPD patients. A worse oxygenation status is associated with increased cardiac vagal and decreased cardiac sympathetic activities in COPD patients.

The right lateral decubitus position can lead to the highest vagal modulation and the lowest sympathetic modulation among three recumbent positions in patients with Q wave myocardial infarction. The right lateral decubitus position can be used as an effective vagal enhancer in patients with Q wave myocardial infarction but without severe bradycardia or atrioventricular block.

Patients with systemic lupus erythematosus (SLE) are known to have lower heart rate variability and impaired vagal modulation, and right lateral position has been shown to lead to a higher vagal modulation than supine position in healthy subjects and patients with cardiovascular diseases. This study evaluated the effect of disease activity and different recumbent positions on cardiac autonomic nervous modulation by heart rate variability analysis in patients with SLE. Thirty-five female patients with SLE and 33 female controls were enrolled in this study. Electrocardiogram was recorded during supine, left lateral, and right lateral positions for 15 min. Both time and frequency domains heart rate variability measures were calculated. The normalized high-frequency power was used as the index of vagal activity, and the low-/high-frequency power ratio as the index of sympathovagal balance. We found that patients with SLE had lower indices of time domain heart rate variability measures and lower low-frequency power, high-frequency power, and normalized high-frequency power than control subjects. SLE patients with lower serum albumin had lower normalized high-frequency power and higher low-/high-frequency power ratio. In patients with SLE, right lateral position could lead to higher high-frequency power, normalized high-frequency power, and lower low-/high-frequency power ratio than supine position. In addition, the lower the normalized high-frequency power in supine position the patient had, the greater the increase in normalized high-frequency power when the position of the patient was changed from supine to right lateral. Thus, serum albumin level might be used as a potential disease severity index of SLE, and right lateral position can lead to higher vagal modulation and lower sympathetic modulation, renin-angiotensin-aldosterone modulation, and vagal withdrawal than supine position in patients with SLE. Right lateral position can be used as an efficient and physiological vagal enhancer in SLE patients with depressed vagal modulation.