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首页> 外文期刊>American Journal of Physiology >Time course analysis of baroreflex sensitivity during postural stress.
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Time course analysis of baroreflex sensitivity during postural stress.

机译：姿势压力下压力反射敏感性的时程分析。

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摘要

Postural stress requires immediate autonomic nervous action to maintain blood pressure. We determined time-domain cardiac baroreflex sensitivity (BRS) and time delay (tau) between systolic blood pressure and interbeat interval variations during stepwise changes in the angle of vertical body axis (alpha). The assumption was that with increasing postural stress, BRS becomes attenuated, accompanied by a shift in tau toward higher values. In 10 healthy young volunteers, alpha included 20 degrees head-down tilt (-20 degrees), supine (0 degree), 30 and 70 degrees head-up tilt (30 degrees, 70 degrees), and free standing (90 degrees). Noninvasive blood pressures were analyzed over 6-min periods before and after each change in alpha. The BRS was determined by frequency-domain analysis and with xBRS, a cross-correlation time-domain method. On average, between 28 (-20 degrees) to 45 (90 degrees) xBRS estimates per minute became available. Following a change in alpha, xBRS reached a different mean level in the first minute in 78% of the cases and in 93% after 6 min. With increasing alpha, BRS decreased: BRS = -10.1.sin(alpha) + 18.7 (r(2) = 0.99) with tight correlation between xBRS and cross-spectral gain (r(2) approximately 0.97). Delay tau shifted toward higher values. In conclusion, in healthy subjects the sensitivity of the cardiac baroreflex obtained from time domain decreases linearly with sin(alpha), and the start of baroreflex adaptation to a physiological perturbation like postural stress occurs rapidly. The decreases of BRS and reduction of short tau may be the result of reduced vagal activity with increasing alpha.
机译：姿势紧张需要立即的自主神经动作来维持血压。我们确定了垂直体轴角（α）逐步变化期间收缩压与心跳间隔变化之间的时域心脏压力反射敏感性（BRS）和时间延迟（tau）。假设是随着姿势压力的增加，BRS减弱，伴随着tau向更高值的转移。在10位健康的年轻志愿者中，alpha值包括：头向下倾斜20度（-20度），仰卧（0度），头向上倾斜30度和70度（30度，70度）和自由站立（90度）。在每次alpha变化之前和之后的6分钟内对无创血压进行分析。 BRS是通过频域分析和xBRS（互相关时域方法）确定的。平均而言，每分钟28（-20度）至45（90度）xBRS估计值可用。随着alpha的变化，xBRS在78％的案例中在第一分钟达到了不同的平均水平，而在6分钟后达到了93％。随着alpha的增加，BRS降低：BRS =-10.1.sinα+ 18.7（r（2）= 0.99），xBRS与互谱增益之间的紧密相关性（r（2）约为0.97）。延迟tau移向更高的值。总之，在健康受试者中，从时域获得的心脏压力反射的敏感性随sinα线性降低，并且压力反射适应诸如姿势压力之类的生理扰动迅速开始。 BRS的减少和短tau的减少可能是迷走神经活动随α增加而降低的结果。

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