The preventive effect of acupuncture stimulation on optokinetic motion sickness: Examination of optimal acupuncture stimulation conditions in a randomized controlled trial

INTERVENTION: Control group (sham acupuncture group): After 20 minutes of rest, including placement of the electrodes and the VR head set, the subjects are asked to sit on the chair for a total of 40 min: 5 min baseline period, 20 min acupuncture stimulation, and 15 min VR intervention. The VR intervention is created based on previous reports, and a cylindrical shape with a diameter of 75 cm become a virtual space. A cylindrical shape have alternating white 6.2 cm and black 3.8 cm vertical stripes inside, that is rotated clockwise at a speed of 60 degree per second for 15 minutes to induce optokinetic motion sickness. At this time, the subjects complain of autonomic nervous symptoms and are instructed to remove the VR head set if they could not tolerate it. In sham acupuncture group, we use custom‐made (in‐house) sham acupuncture needles with disinfected stainless acupuncture needles (0.80 mm diameter and 40 mm length; TAIHO Medical Products Co., Ltd., Hiroshima, Japan) inserted into a custom‐made guide tube. The needling sites are performed on ST36 bilaterally located in the tibialis anterior muscle between the head of fibula and the lower end of the tibial tuberosity. Manual acupuncture group: After 20 minutes of rest, including placement of the electrodes and the VR head set, the subjects are asked to sit on the chair for a total of 40 min: 5 min baseline period, 20 min acupuncture stimulation, and 15 min VR intervention. The VR intervention is created based on previous reports, and a cylindrical shape with a diameter of 75 cm become a virtual space. A cylindrical shape have alternating white 6.2 cm and black 3.8 cm vertical stripes inside, that is rotated clockwise at a speed of 60 degree per second for 15 minutes to induce optokinetic motion sickness. At this time, the subjects CONDITION: Optokinetic motion sickness Nausea PRIMARY OUTCOME: The electrogastrogram (EGG) is measured using a portable EGG recorder (EGS2. Nipro Co., Japan). A disposable Ag‐AgCl electrodes (Vitrode F, NIHON KODEN, Japan) are placed just under the left and right costal margin at the upper quarter level between the processus xiphoideus and the umbilicus. Moreover, the keratin is removed using tape to reduce the electrical resistance of the skin in before applying the electrodes. EGG data are transferred to a PC at a sampling rate of 1 Hz, then using a fast Fourie's transform (FFT), we compute an algorithm of a power spectra of every 256 sec. Each EGG recording divided into blocks of 60 sec without overlapping. On the power spectrum of each 60 sec, the dominant frequencies of EGG are defined under 0‐9 cpm. The percentages of the normogastria range (2‐4 cpm), the bradygastria range (0‐2 cpm), and the tachygastria range (4‐9 cpm) are calculated, respectively. EGG is measured for 20 minutes of 5 minutes at rest before acupuncture stimulation and 15 minutes during VR intervention. INCLUSION CRITERIA: SECONDARY OUTCOME: For the electrocardiogram (ECG), a disposable Ag‐AgCl electrodes (Vitrode Bs, NIHON KODEN, Japan) are attached to the chest and amplified using a bio‐amplifier (ML132, AD instruments, Australia). The filter settings are high cut filter 60 Hz and the time constant is 0.03 sec. The ECG is taken into a PC at a sampling rate of 1 kHz via an A / D converter (Power Lab 8sp, AD Instruments, Australia), and HRV analysis is used the analysis software Chart5 (AD Instruments, Australia) and HRV module. In the power spectrum obtained by FFT, 0.05‐0.15 Hz power is defined as the low‐frequency (LF) component, and 0.15‐0.4 Hz power is defined as the high‐frequency (HF) component. The ratios of LF and HF to the total power values are defined as normalized units of LF (LFnu) and normalized units of HF (HFnu). Moreover, LF / HF is calculated which is the ratio of the LF component and the HF component. The HFnu is used as the inde Xfor vagal activity and the LFnu is used as the inde Xof sympathetic activity and the LF/HF ratio is used as the inde Xof sympatho‐vagal balance. The measurement is performed for a total of 20 minutes of 5 minutes before acupuncture stimulation and 15 minutes during VR intervention.; The evaluation of nausea is performed with 0 points for no symptoms and 100 points for vomiting, and listen to 3 times of before acupuncture stimulation and before/after VR intervention.; The subjective symptom of motion sickness (SSMS) is used to evaluate motion sickness. SSMS consists of 7 items of dizziness, headaches, warmth, sweating, drowsiness, increasing salivation, and nausea in motion sickness. The degree of each symptom is rated on a scale of 4 and 6, and the minimum score is 0 and the maximum score is 49. This SSMS is listened to every 3 minutes for 15 minutes corresponding to VR intervention, and the transition of symptoms over time is confirmed.