Effects of Acupuncture Stimulation to Cervical Sympathetic Trunk on Maximal Respiratory Mouth Pressure: A Randomized Crossover Study

Abstract

Objective: The autonomic nerves in the lungs and the intercostal and phrenic nerves are important for respiratory movements. This study investigated the effects of electroacupuncture (EA) stimulation via the sympathetic nerve on maximal respiratory mouth pressure.

Materials and methods: This prospective, single-center, randomized crossover study was conducted in Teikyo Heisei University, Japan. The subjects were 17 healthy adults (15 men and 2 women), who were randomly assigned to untreated and EA groups in a crossover trial with a 2-week washout period. Initially, respiratory mouth pressure was tested in both groups. After 5 minutes of rest, either a 5-minute rest or an EA stimulus was delivered, followed by 5 minutes of rest. EA was delivered near the cervical ganglia at the level of the sixth cervical vertebra on the left side. The EA stimulus was set to 2 Hz, and the stimulation intensity was set to a level so that no pain would be felt by the volunteers. Nasal-skin temperature was measured during rest or EA stimulation. Thereafter, respiratory mouth pressure was tested again in both groups.

Results: The EA group had a significant reductions in nasal-skin temperature during the intervention and a significant increase in inspiratory and expiratory respiratory mouth pressure after the intervention, compared to the nonstimulated group.

Conclusions: The 2-Hz EA stimulation via the sympathetic nerve activated the sympathetic nerves and suppressed respiratory mouth pressure weakness. Future studies are needed to evaluate EA's effectiveness for treating bronchial stenosis and respiratory weakness.

Keywords: airway smooth muscle; nasal-skin temperature; respiratory-function test.

FIG. 1.

Research protocol. First, participants were in a seated position and rested for 10 minutes. Participants then rested in a supine position for 5 minutes. A crossover study was then performed without stimulation or with 2-Hz electroacupuncture (EA) stimulation for 5 minutes. After the intervention, the volunteers rested for 5 minutes. The washout period was 2 weeks. Respiratory-function measurement points and oral pressures: Before: Respiratory function and oral pressure in a sitting position after 10 minutes of rest; After: 5 minutes of rest in a supine position, 5 minutes of intervention and 5 minutes of rest, after which respiratory function and oral pressure were measured again. Measurement points of nasal skin temperature: Before stimulation: After rest in the supine position for 3 minutes, nasal skin temperature measured continuously for 2 minutes; During stimulation: Nasal skin temperature measured without stimulation or 2-Hz EA stimulation for 5 minutes. After stimulation: Nasal skin temperature measured for 5 minutes. min, minutes.

FIG. 2.

Changes in maximum inspiratory pressure (MIP). Changes in inspiratory-muscle strength are shown for the untreated group ( × ) and the 2-Hz electroacupuncture (EA) group (●). On the vertical axis, Before is the reference value of 0; After is the amount of change in MIP between the groups after the intervention. On the abscissa, Before shows the reference value as 0; After shows the change in each group after the intervention. On the vertical axis, the inspiratory-muscle strength of the 2-Hz EA group had a significant increase after the intervention, compared to before the intervention (P = 0.0326). On the horizontal axis, there was a significant difference between the 2-Hz EA group and the untreated group after the intervention (P = 0.018). Statistical analysis was performed using a 2-way analysis of variance, and the significance level was set at *P < 0.05.

FIG. 3.

Changes in maximum expiratory pressure (MEP). Changes in expiratory-muscle strength are shown for the untreated group ( × ) and the 2-Hz electroacupuncture (EA) group (●). On the vertical axis, Before is the reference value as 0; After is the amount of change in MEP between the groups after the intervention. On the abscissa, Before shows the reference value as 0; After shows the change in each group after the intervention. On the vertical axis, the expiratory-muscle strength of the untreated group had a significant decrease after the intervention, compared to that before the intervention (P = 0.0015). The horizontal axis was significantly reduced in the untreated group [ × ] and in the 2-Hz EA [●] group after the intervention (P = 0.0007). Statistical analysis was performed with a 2-way analysis of variance, and the significance level was set at **P < 0.01.

FIG. 4.

Changes in peak expiratory flow (PEF). Changes in PEF are shown for the untreated group ( × ) and the 2-Hz electroacupuncture (EA) group (●). On the vertical axis, Before is the reference value as 0; After is the amount of change in PEF between the groups after the intervention. On the abscissa, Before shows the reference value as 0; After shows the change in each group after the intervention. On the vertical axis, the 2-Hz EA group PEF was significantly different after the intervention, compared to before the intervention (P = 0.001). On the horizontal axis, there was a significant difference between the 2-Hz EA group and the untreated group after the intervention (P = 0.0031). Statistical analysis was performed by a 2-way analysis of variance, and the significance level was set at **P < 0.01. min, minutes.

FIG. 5.

Changes in forced vital capacity (FVC). Changes in FVC are shown for the untreated group ( × ) and the 2-Hz electroacupuncture (EA) group (●). On the vertical axis, Before is the reference value as 0; After is the amount of change in FVC between the groups after the intervention. On the abscissa, Before shows the reference value as 0; After shows the change in each group after intervention. On the vertical axis, there was no significant difference in the untreated group and the 2-Hz EA group after the intervention, compared to before the intervention. On the horizontal axis, there was no significant difference between the groups. Statistical analysis was performed by a 2-way analysis of variance; significance level was set at P < 0.05.

FIG. 6.

Changes in forced expiratory volume in 1 second (FEV_1.0). Changes in FEV_1.0 are shown for the untreated group ( × ) and the 2-Hz electroacupuncture (EA) group(●). On the vertical axis, Before is the reference value as 0; After is the amount of change in FEV_1.0 between the groups after the intervention. On the abscissa, Before shows the reference value as 0; After shows the change in each group after the intervention. On the vertical axis, there was no significant difference in the untreated group and the 2-Hz EA group after the intervention, compared to before the intervention. On the horizontal axis, there was no significant difference between the groups. Statistical analysis was performed by a 2-way analysis of variance; significance level was set at P < 0.05.

FIG. 7.

Variations in nasal skin temperature. The amount of change in nasal skin temperature is shown between the untreated group ( × ) and the 2-Hz electroacupuncture (EA) group (●). The vertical axis is 0, which indicates the amount of change in nasal skin temperature during and after the intervention. The abscissa shows the amount of change in nasal skin temperature during and after stimulation at rest, and the rest before stimulation is set as the reference value 0. No changes were observed in the untreated group during or after the intervention. In the 2-Hz EA group, a significant difference (P = 0.0003) was observed before and during stimulation. A significant difference (P = 0.0359) was observed before and after the stimulation. In addition, a significant difference (P = 0.0002) was observed between the untreated group and the 2-Hz EA group. Statistical analysis was performed by a 2-way analysis of variance; significance levels were set to *P < 0.05; **p < 0.01. min, minutes.