| Background: There are a number of different environmental factors in the course ofspace flight, of which weightlessness is the most important factor, and it is a hot topic inthe field of aerospace medicine. The environment of weightlessness could have effecton the various systems of human body with different degrees, particularly, impact on thecardiovascular system. The astronauts have been identified taking on cardiovascularadaptation during space flight, but the mechanism is far from clarified, and the rules andmechanisms about cardiovascular dysfunction are little known in the long-termweightlessness. With the continuous development of aerospace medicine and theimprovement in medical equipment, the cardiovascular system has been studied inweightlessness. Echo-tracking technology is the recent technology of ultrasoundimaging diagnosis, which could be used to evaluate the vascular elasticity. ETtechnology has already been used in clinical and research works. Through tracking themovement trajectory of the vessel’s wall by ET technology in real time, the changes ofthe vessel’s diameter could be calculated and the curve could be displayed, and whichcould be expressed as some parameters to reflect the arterial elasticity. Applying highresoulution ultrasound, blood flows of internal carotid artery and vertebral artery couldbe detected under simulated weightlessness, and the parameters associated with theblood flows could be calculated for analysis. These ultrasound techniques could be usedto evaluate the arterial elasticity and blood flow under weightlessness with highfeasibility and credibility.Objectives: The elasticities of bilateral common carotid artery of female volunteers were detected non-invasively by E-tracking technology, and blood flows of internalcarotid artery and vertebral artery were detected by high-resoulution ultrasond under thecondition of simulated weightlessness. Aimed to elucidate the effects of simulatedweightlessness on the elasticity and blood flow of female’s bilateral carotid artery.Methods: Twenty-two healthy female volunteers, aged of19to23years old, withaverage age of twenty-one years old, were exposed to-6°head down tilt (HDT) bedrest for21days. The elasticity of women’s bilateral common carotid artery was detectednon-invasively by E-tracking technology at the third day before HDT, the1st day, the3rd day, the7th day, the15th day during HDT, and the3rd day after HDT. The elasticityparameters of common carotid artery including pressure-strain elasticity modulus (Ep),stiffness parameter (β), arterial compliance (AC), pulse wave velocity (PWVβ) andaugmentation index (AI). The data were analyzed by paired t test with SPSS17.0, andP<0.05was significant point. Bilateral internal carotid artery and vertebral artery wereexamined by high-resolution ultrasound, and pulsatility index(PI), resistance index(RI)and flow volume were calculated. The data were analyzed by ANOVA test withSPSS17.0, and P<0.05was significant point.Results: All these twenty-two female volunteers completed this experimental task.1.Application of ET technologies in detecting artery elasticity, four of them had nointegral data, and the integral data of eighteen female volunteers were gotten foranalysis. Statistical analysis showed that there were no differences between left andright common carotid artery at all examination points. Compared with the data beforesimulated weightlessness, Ep, β, PWVβ and AC had no significant difference on rightcarotid artery, but AI had significant difference on right carotid artery; Ep, β, PWVβ andAC had no significant difference on left carotid artery, but AI had significant differenceat the third day before HDT, the1st and the3rd during HDT on left carotid artery.2. Detection of internal carotid artery and vertebral artery blood flow, the allvolunteer-related parameters were gotten. Statistical analysis showed as follows:compared with simulated weightlessness before, at the time node and after the3rd dayduring simulated weightlessness, bilateral internal carotid artery and vertebral arterypulsatility index and resistance index had no apparent change in blood flow. Total bloodflow of vertebral artery was lower at the3rd and7th days during simulatedweightlessness than simulated weightlessness before (p<0.05), but no significant changewas detected at other time points.Conclusions: The research indicated that short-term simulated weightlessness had nosignificant effects on the common carotid artery elasticity of healthy female volunteers.And simulated weightlessness had no significant effect on the flow internal carotidartery and vertebral artery. These phenomena showed, at the experimental time limitunder the condition of simulated weightlessness, that the human beings could keep thesteady state of the elasticity of common carotid arterial through autoregulation, and theparameters of bilateral internal carotid artery and vertebral artery could keep stationarystate as well. |
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