心肺压力感受器持续卸荷对前臂血流、血管阻力及心率变异性谱的影响

EFFECTS OF SUSTAINED UNLOADING OF CARDIOPULMONARY BARORECEPTORS ON FOREARM BLOOD FLOW,FOREARM VASCULAR RESISTANCE AND HEART RATE VARIABILITY SPECTRUM

低压值下体负压（ＬＢＮＰ）可仅使心肺压力感受器卸荷。采用－２ｋＰａＬＢＮＰ实验结果表明：ＬＢＮＰ既不引起动脉血压变化，也不引起心率改变，但却引起基础胸阻抗（Ｚ。）从对照的２１．８±０．４升高到２２．５±０．５Ω（Ｐ＜０．０１），前臂血管阻力（ＦＶＲ）从１２．３±０．９升高到１９．９±１．４Ｕ（Ｐ＜０．０１），前臂血流（ＦＢＦ）从对照时７．１±０．５降低到４．３±０．３ｍｌ·ｍｉｎ￣（－１）·１００ｍｌ￣（－１），心率变异性谱（ＨＲＶ）未发生任何变化，即心肺压力感受器卸荷时心脏自主神经活动水平与均衡性不受影响。由于ＦＶＲ和ＦＢＦ的变化可间接反映外周血管交感传出活动水平，上述实验结果提示，心肺压力感受器对外周血管及心脏自主神经活动的调节可能存在机能分化现象。

Twelve healthy young male subjects underwent a 10min control period followed by 20min of-2kPa lower body negative pressure(LBNP).During this low level of LBNP,there was no anysignificant change in arterial blood pressure and heart rate. Baseline thoracic impedance(Z_O) in-creased from a control value of 21.8 ± 0.4 to 22.5 ± 0.5Ω(P<0.01),the forearm blood flow (FBF)decreased from 7.1 ± 0.5 to 4.3 ± 0.3ml·min￣(-1)·100ml￣(-1)(P<0.01)and the forearm vascular re-sistance(FVR) increased from 12.3 ± 0.9 to 19.9±1.4 units(P<0.01).However,changes ofheart rate variability(HRV)spectral components during-2kPa LBNP exposure were not ob-served.These observations demonstrate that sustained unloading of cardiopulmonarybaroreceptors has no effect on cardiac sympathetic and parasympathetic nerve activities.To ourknowledge,the changes in muscle sympathetic nerve activity(MSNA) may be in parallel to thatof FVR,therefore it is suggested that a functional dissociation of cardiopulmonary baroreceptorregulation on MSNA and cardiac autonomic function may exist in humans.