To investigate the changes of cardiovascular function during short-term simulated weightlessness after electroacupuncture (EA) treatment．
Spaceflight is associated with cardiovascular deregulation. However, the influence of microgravity on the cardiovascular system and the underlying mechanisms and countermeasures remain largely unknown. Our previous studies have demonstrated that electroacupuncture (EA) is effective at improving orthostatic tolerance (OT). The purpose of this study was to determine if EA treatment can attenuate cardiovascular deconditioning induced by a 4-day -6° head-down bed rest (HDBR). Fourteen healthy male subjects were randomly allocated into a control group (Con, n=6, 4 days HDBR without countermeasure) and an EA treatment group (EA, n=8, 4 days HDBR with EA at Neiguan \[PC-6\] for 30 min daily for 4 consecutive days during HDBR). OT was estimated with a combination of +75°/20 min head-up tilt and lower body negative pressure test before and after HDBR. Plasma hormones and heart rate variability were assessed before and after HDBR. Cardiac systolic functions and cerebral blood flow were measured before, during, and after HDBR. The data showed that EA treatment applied daily for 30 min during a 4-day HDBR prevented OT and cardiac systolic function from decrease, prevented autonomic dysfunction (a decrease in the activity of the parasympathetic nervous system), and increased the concentrations of plasma angiotensin II (Ang II) and aldosterone (Ald). These results indicate that 30 min of daily EA treatment at PC-6 is highly effective in partially maintaining OT and cardiac systolic function. Activation of the peripheral sympathetic nervous system and increased plasma hormones is largely responsible for maintaining OT after a 4-day HDBR. Therefore, EA treatment appears to be an effective countermeasure against cardiovascular deconditioning induced by HDBR.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Enrollment
20
Electroacupuncture was performed using small-sized (1.5 cm) cutaneous electrode pads placed bilaterally at the PC-6 points of the forearms (Supplementary Figure 1). The intensity of the electrical stimulation was adjusted to produce the most intense tolerable electrical sensation without muscle contractions or uncomfortable feelings at a frequency of 50 Hz using the Hwato electronic acupuncture treatment instrument (Model No. SDZ-II; Suzhou Medical Appliances Co, Ltd, Suzhou, China).
Department of Aerospace Biodynamics, Faculty of Aerospace Medicine, Fourth Military Medical University
Xi'an, Shaanxi, China
Orthostatic tolerance test
The subjects remained at rest in a supine position for 15 min to collect control data, and then tilted to 75° head-up tilt testing (HUT) for 5 second followed by increasing steps of lower body negative pressure (LBNP). LBNP began at -20mm Hg for 5 minutes followed by an increase of -20 mm Hg every 5 minutes until -60 mm Hg (total duration = 20 minutes) or presyncope.
Time frame: 35 minutes
Measurements of cardiac systolic function and cerebral blood flow
Time frame: 6 days
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