Autonomic Medicine Section, Clinical Neurosciences Program, Division of Intramural Research, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive MSC-1620, Building 10 Room 8N260, Bethesda, MD, 20892-1620, USA.
Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, USA.
Clin Auton Res. 2024 Feb;34(1):125-135. doi: 10.1007/s10286-024-01022-7. Epub 2024 Mar 6.
Orthostasis increases the variability of continuously recorded blood pressure (BP). Low-frequency (LF) BP oscillations (Mayer waves) in this setting are related to the vascular-sympathetic baroreflex. Mechanisms of increased high-frequency (HF) BP oscillations at the periodicity of respiration during orthostasis have received less research attention. A previously reported patient with post-neurosurgical orthostatic hypotension (OH) and vascular-sympathetic baroreflex failure had large tilt-evoked, breathing-driven BP oscillations, suggesting that such oscillations can occur independently of vascular-sympathetic baroreflex modulation. In the present study we assessed effects of orthostasis on BP variability in the frequency domain in patient cohorts with or without OH.
Power spectral analysis of systolic BP variability was conducted on recordings from 73 research participants, 42 with neurogenic OH [13 pure autonomic failure, 14 Parkinson's disease (PD) with OH, 12 parkinsonian multiple system atrophy, and 3 status post-brainstem neurosurgery] and 31 without OH (control group of 16 healthy volunteers and 15 patients with PD lacking OH), before, during, and after 5' of head-up tilt at 90 degrees from horizontal. The data were log transformed for statistical testing.
Across all subjects, head-up tilting increased HF power of systolic BP variability (p = 0.001), without a difference between the neurogenic OH and control groups. LF power during orthostasis was higher in the control than in the OH groups (p = 0.009).
The results of this observational cohort study confirm those based on our case report and lead us to propose that even in the setting of vascular-sympathetic baroreflex failure orthostasis increases HF power of BP variability.
直立位会增加连续记录的血压（BP）的变异性。在此设置中，低频（LF）BP 振荡（Mayer 波）与血管 - 交感神经压力反射有关。在直立期间，呼吸周期的高频（HF）BP 振荡增加的机制受到的研究关注较少。以前报道的一例神经外科手术后直立性低血压（OH）和血管 - 交感神经压力反射衰竭的患者，倾斜诱发的呼吸驱动的 BP 振荡较大，这表明这种振荡可以独立于血管 - 交感神经压力反射调节而发生。在本研究中，我们评估了 OH 患者和无 OH 患者的 BP 变异性在频率域中的直立位影响。
对 73 名研究参与者的收缩压变异性的功率谱分析进行了记录，其中 42 名患有神经源性 OH [13 例纯自主神经衰竭，14 例帕金森病伴 OH，12 例帕金森病多系统萎缩和 3 例脑干神经外科术后]和 31 名无 OH（对照组 16 名健康志愿者和 15 名无 OH 的帕金森病患者），在水平 90 度头高位倾斜之前、期间和之后 5 分钟。为了进行统计检验，对数据进行了对数转换。
在所有受试者中，头高位倾斜增加了收缩压变异性的 HF 功率（p=0.001），神经源性 OH 组和对照组之间没有差异。在直立位期间，对照组的 LF 功率高于 OH 组（p=0.009）。
这项观察性队列研究的结果证实了基于我们的病例报告的结果，并使我们提出即使在血管 - 交感神经压力反射衰竭的情况下，直立位也会增加 BP 变异性的 HF 功率。
