Department of Anesthesiology, Yale University School of Medicine, 333 Cedar Street, PO Box 208051, New Haven, CT 06520-8051, USA.
Physiol Meas. 2014 Jul;35(7):1509-20. doi: 10.1088/0967-3334/35/7/1509. Epub 2014 Jun 5.
Lower body negative pressure (LBNP) creates a reversible hypovolemia by sequestrating blood volume in the lower extremities. This study sought to examine the impact of central hypovolemia on peripheral venous pressure (PVP) waveforms in spontaneously breathing subjects. With IRB approval, 11 healthy subjects underwent progressive LBNP (baseline, -30, -75, and -90 mmHg or until the subject became symptomatic). Each was monitored for heart rate (HR), finger arterial blood pressure (BP), a chest respiratory band and PVP waveforms which are generated from a transduced upper extremity intravenous site. The first subject was excluded from PVP analysis because of technical errors in collecting the venous pressure waveform. PVP waveforms were analyzed to determine venous pulse pressure, mean venous pressure, pulse width, maximum and minimum slope (time domain analysis) together with cardiac and respiratory modulations (frequency domain analysis). No changes of significance were found in the arterial BP values at -30 mmHg LBNP, while there were significant reductions in the PVP waveforms time domain parameters (except for 50% width of the respiration induced modulations) together with modulation of the PVP waveform at the cardiac frequency but not at the respiratory frequency. As the LBNP progressed, arterial systolic BP, mean BP and pulse pressure, PVP parameters and PVP cardiac modulation decreased significantly, while diastolic BP and HR increased significantly. Changes in hemodynamic and PVP waveform parameters reached a maximum during the symptomatic phase. During the recovery phase, there was a significant reduction in HR together with a significant increase in HR variability, mean PVP and PVP cardiac modulation. Thus, in response to mild hypovolemia induced by LBNP, changes in cardiac modulation and other PVP waveform parameters identified hypovolemia before detectable hemodynamic changes.
下体负压（LBNP）通过将血量隔离在下肢来造成可逆性低血容量。本研究旨在检查中心低血容量对自主呼吸受试者外周静脉压（PVP）波形的影响。经机构审查委员会批准，11 名健康受试者接受了逐步 LBNP（基线，-30mmHg，-75mmHg 和-90mmHg，或直到受试者出现症状）。监测心率（HR）、手指动脉血压（BP）、胸部呼吸带和 PVP 波形，PVP 波形来自经转换的上肢静脉部位。由于在收集静脉压力波形时出现技术错误，第一个受试者被排除在 PVP 分析之外。分析 PVP 波形以确定静脉脉搏压、平均静脉压、脉搏宽度、最大和最小斜率（时域分析）以及心脏和呼吸调制（频域分析）。在 -30mmHg LBNP 时，动脉血压值没有发现有意义的变化，而 PVP 波形的时域参数（除了呼吸引起调制的 50%宽度外）以及 PVP 波形在心脏频率但不在呼吸频率的调制都有显著降低。随着 LBNP 的进展，动脉收缩压、平均血压和脉压、PVP 参数和 PVP 心脏调制显著降低，而舒张压和 HR 显著增加。在症状期，血流动力学和 PVP 波形参数的变化达到最大值。在恢复阶段，HR 显著降低，HR 变异性、平均 PVP 和 PVP 心脏调制显著增加。因此，在 LBNP 引起的轻度低血容量反应中，心脏调制和其他 PVP 波形参数的变化在可检测的血流动力学变化之前确定了低血容量。
