Effects of 2-Hz and 100-Hz Electroacupuncture Stimulation on Respiratory Function and Heart Rate Variability: A Randomized Crossover Study

Background: Bronchial contraction and dilation is thought to be caused by non-adrenergic non-cholinergic nerves. Objective: To investigate the effects of low-frequency (1-5 Hz) and high frequency (50-100 Hz) electric acupuncture (EA) stimulation on bronchial dilation. Design: Prospective, single-center study. Setting: Teikyo Heisei University Subjects: Seventeen healthy male adults Randomization: We randomly assigned subjects to 2-Hz EA and 100-Hz EA groups in a crossover trial. The washout period was 2 weeks. Intervention: Both groups underwent a respiratory function test, followed by a 5-minute rest, followed a 5-minute rest or EA stimulation, followed by a 5- min rest. Heart rate variability was measured at rest, followed by another respiratory function test. Acupuncture was delivered near the cervical ganglia at the level of the sixth cervical vertebra on the left side. EA stimuli were set to 2-Hz or 100-Hz, and stimulation intensity was set to a level where no pain was felt. Main outcome measures: Spirometry (forced vital capacity, forced expiratory volume in 1 s, and maximum respiratory flow), autonomic nerve activity (low-frequency component, high-frequency component, and their ratio), and heart rate variability. Results: Heart rate variability analysis showed significant differences in heart rate between the 2-Hz EA and 100-Hz EA groups. The 2-Hz EA group showed a significant increase in HF. Conclusions: 2-Hz EA stimulation resulted in decreased heart rate and increased HF during stimulation. This may be more effective for regulation of the autonomic nerves of the cardiopulmonary system than 100-Hz EA stimulation. Future studies are required to confirm our findings.