What options does the supine-standing-supine test offer to patients with hypertension? Demonstrations of examples

Aims: The purpose of the study was to demonstrate autonomic nervous system (ANS) changes associated with treatment in hypertensive patients and utilization of these measurements in practice. Methods: Hypertensive patients were examined before the start of treatment and after blood pressure compensation. The telemetric system VarCor PF 5 was used for non-invasive heart rate registration and automatic evaluation of heart rate variability (HRV) parameters. The supine-standing-supine test with ortho-clinostatic loading in standard conditions was used for HRV evaluation. Results: The influence of antihypertensive therapy on ANS was demonstrated in two cases. The first was a case of a responder to therapy and the second case was example of a non-responder to monotherapy regarding more therapeutic steps for blood pressure control. Different modes of results presentation are demonstrated: 3D graph, numeric form of standard parameters of HRV, computer interpretation of results by means of complex parameters and indices in numeric, graphic and verbal form with functional age calculation, cross graph of vagal activity index versus sympatho-vagal balance index was used for repeated measurements and follow-up. The increased spectral performance with augmented vagal activity and slope down of sympatho-vagal ratio are evident after blood pressure control achievement. Improvement of functional age parameter associated with blood pressure compensation is visible using a complex age-dependent parameters interpretation. Conclusions: HRV evaluation in hypertensive patients provides new parameters for patient's examination. These parameters are influenced by both the illness itself and by pharmacotherapy. Such an approach offers more complex information about patient.     

An adaptive test for a subset of coefficients in a multivariate regression model

An adaptive multivariate test is proposed for a subset of regression coefficients in a linear model. This adaptive method uses the studentized deleted residuals to calculate an appropriate weight for each observation. The weights are then used to compute Wilk's lambda for the weighted model. The adaptive test is performed by permuting the independent variables corresponding to those parameters that are assumed to equal zero in the null hypothesis. The permuted variables are then weighted to obtain a permutation test statistic that is used to estimate the p-value. An example is presented of a multivariate regression that uses systolic and diastolic blood pressure as dependent variables with age and body mass index as independent variables. The simulation results show that the adaptive test maintains its size for the three multivariate error distributions that were used in the study. For normal error models the power of the adaptive test nearly equaled that of the non-adaptive test. For models that used non-normal errors the adaptive test was considerably more powerful than the traditional non-adaptive test.     

同步间歇指令通气和适应性支持通气对COPD合并呼吸衰竭患者周围循环和血气的影响

目的:研究同步间歇指令通气(SIMV)与适应性支持通气(ASV)对慢性阻塞性肺部疾病(COPD)合并呼衰患者机体外周血循环、血气指标的影响。方法:选取2006年3月至2013年12月在我院接受治疗的COPD合并呼吸衰竭患者86例,对其分别先后采用ASV、SIMV呼吸模式,记录呼吸机参数、外周血循环参数及血气指标。结果:ASV组呼吸频率(RR)、潮气量(TV)、吸气峰值压(PIP)均显著低于SIMV组(均P0.01);ASV组外周血心率(HR)、收缩压(SBP)、舒张压(DBP)、中心静脉压(CVP)均显著低于SIMV组(均P0.01);ASV组动脉血氧分压(PaO_2)、pH、血氧饱和度(Sa O2)均较SIMV组显著升高(均P0.05)。结论:ASV模式下治疗COPD合并呼吸衰竭患者的呼吸参数、外周血循环参数、血气改善效果优于SIMV模式。     

垂体后叶素联合催产素对腹腔镜下子宫肌瘤剔除术患者循环系统的影响及止血效果

目的:研究垂体后叶素联合催产素对腹腔镜下子宫肌瘤剔除术患者循环系统的影响及止血效果。方法:收集本院2011年10月至2013年10月进行腹腔镜下子宫肌瘤剔除术的75例子宫肌瘤患者,采用简单随机分组的方法将研究样本序贯分为A组(垂体后叶素组)、B组(催产素组)、C组(垂体后叶素联合催产素组)三组,各25例。比较各组循环系统和止血效果指标是否有变化及差异。结果:三组之间收缩压、舒张压、心率差异有统计学意义(P0.05),不同时间的收缩压、舒张压、心率差异有统计学意义(P0.05),收缩压、舒张压、心率分组与时间之间有交互作用(P0.05)。A组较B组低血压、心动过速及出血量更少,B组较A组高血压、心动过缓更少,差异均有统计学意义(P0.05);C组较A组高血压、心动过缓更少,差异有统计学意义(P0.05);C组较B组低血压、心动过速及出血量更少,差异有统计学意义(P0.05)。结论:腹腔镜下子宫肌瘤剔除术患者联合应用垂体后叶素与催产素后循环波动小,止血效果好,值得在临床上推广应用。     

Motion energy as a control variable for adapting stimulation frequency

An activity sensing rate-responsive pacing system is presented which adaptively controls heart rate to adjust cardiac output in response to increased metabolic demand, and more optimally restore homeostasis of the intact cardiovascular system. The current use of ventricular demand and DDD universal pacing systems, although rate and multi-parameter and multi-function programmable, are fixed at these programmed settings. These devices are adequate for patients at rest or during moderate exertion, but are suboptimal for physically active patients whose physiology requires increased oxygen supply to meet an increased cardiac demand. In the past, these patients may have experienced fatigue or dyspnea out of proportion to their cardiovascular disease. The Ergos rate-adaptive single- and dual-chamber pacing system is a second generation pulse generator which is rate responsive to a patient's increased physiologic demand by sensing a motion signal which reflects increased work load and the need for a compensating increase in heart rate. Ergos offers increased assistance to patients with sinus bradycardia who may require the rate-responsiveness with the additional advantage of AV synchrony. Clinical results show the effectiveness of the presented sensor control by motion energy for rate adaptive pacing therapy.     

Selected zinc metabolism parameters in relation to insulin, renin-angiotensin-aldosterone system, and blood pressure in healthy subjects

The relationship between the renin-angiotensin-aldosterone system and insulin concentration and selected zinc (Zn) metabolism parameters and arterial blood pressure in young healthy subjects of both sexes is presented in this study. The following parameters were measured: systolic and diastolic arterial blood pressure, total and ouabain-dependent efflux rate constants of Zn from lymphocytes, serum and lymphocyte Zn concentrations, serum aldosterone, angiotensin-converting enzyme, insulin, sodium and potassium concentrations, body mass index, and plasma rennin activity. The correlations among these parameters show gender-dependent differences, except for a negative correlation between serum Zn and ouabain-dependent Zn efflux rate constant and the serum level of angiotensin-converting enzyme, and a positive relationship between the total efflux rate constant of Zn from lymphocytes and the serum aldosterone levels, both of which were gender independent. The results led us to conclude that there is a gender-independent functional relation between Zn homeostasis and the renin-angiotensin-aldosterone system. Insulin does not appear to play a significant role in Zn homeostasis.     

Respiratory modulation of the autonomic nervous system during Cheyne-Stokes respiration

Cheyne-Stokes respiration (CSR) is associated with increased mortality among patients with heart failure. However, the specific link between CSR and mortality remains unclear. One possibility is that CSR results in excitation of the sympathetic nervous system. This review relates evidence that CSR exerts acute effects on the autonomic nervous system during sleep, and thereby influences a number of cardiovascular phenomena, including heart rate, blood pressure, atrioventricular conduction, and ventricular ectopy. In patients in sinus rhythm, heart rate and blood pressure oscillate during CSR in association with respiratory oscillations, such that both peak heart rate and blood pressure occur during the hyperpneic phase. Inhalation of CO2 abolishes both CSR and the associated oscillations in heart rate and blood pressure. In contrast, O2 inhalation sufficient to eliminate hypoxic dips has no significant effect on CSR, heart rate, or blood pressure. In patients with atrial fibrillation, ventricular rate oscillates in association with CSR despite the absence of within-breath respiratory arrhythmia. The comparison of RR intervals between the apneic and hyperpneic phases of CSR indicates that this breathing disorder exerts its effect on ventricular rate by inducing cyclical changes in atrioventricular node conduction properties. In patients with frequent ventricular premature beats (VPBs), VPBs occur more frequently during the hyperpneic phase than the apneic phase of CSR. VPB frequency is also higher during periods of CSR than during periods of regular breathing, with or without correction of hypoxia. In summary, CSR exerts multiple effects on the cardiovascular system that are likely manifestations of respiratory modulation of autonomic activity. It is speculated that the rhythmic oscillations in autonomic tone brought about by CSR may ultimately contribute to the sympatho-excitation and increased mortality long observed in patients with heart failure and CSR.     

血压自适应控制系统研究

本文设计一个自适应血压自动控制系统,首先,通过动物实验,获得了受控对象的参数变化范围的信息.在此基础上,我们应用参考模型和自校正调节器两种算法设计自适应控制系统.计算机仿真证明这两类算法均可成功地应用于血压的自适应控制,尽管受控对象存在未知时变延时,时间常数和增益的变化.最后,将设计的系统在动物(狗)中作了检验.在18条狗上作升压或降压试验证明,两种算法均有良好的过渡过程特性,这一系统将可应用于临床,以改进药物注射系统的性能.     

Dynamical systems analysis of arterial blood pressure signals in relation to heart rate fluctuations in chick embryos

We attempted a new approach based on a modern dynamical system theory to reconstruct the arterial blood pressure signals in relation to heart rate fluctuations of developing chick embryos. The dynamical systems approach in general is to model a phenomenon that is presented by a single time series record and approximate the dynamical property (e.g. heart rate fluctuations) of a system based only on information contained in a single-variable (arterial blood pressure) of the system. The time-series data of the arterial blood pressure was reconstructed in 3-dimensional space to draw characteristic orbits. Since the reconstructed orbits of the blood pressure should retain information contained in the pressure signals, we attempted to derive instantaneous heart rate (IHR) from the reconstructed orbits. The derived IHR presenting HR fluctuations coincided well with the IHR obtained conventionally from the peak-to-peak time intervals of the maximum blood pressure. Movements of the reconstructed orbits of the arterial blood pressure in 3-dimensional space reflected HR fluctuations (i.e. transient decelerations and accelerations).     

Phase Synchronization of Hemodynamic Variables at Rest and after Deep Breathing Measured during the Course of Pregnancy

Background

The autonomic nervous system plays a central role in the functioning of systems critical for the homeostasis maintenance. However, its role in the cardiovascular adaptation to pregnancy-related demands is poorly understood. We explored the maternal cardiovascular systems throughout pregnancy to quantify pregnancy-related autonomic nervous system adaptations.

Methodology

Continuous monitoring of heart rate (R-R interval; derived from the 3-lead electrocardiography), blood pressure, and thoracic impedance was carried out in thirty-six women at six time-points throughout pregnancy. In order to quantify in addition to the longitudinal effects on baseline levels throughout gestation the immediate adaptive heart rate and blood pressure changes at each time point, a simple reflex test, deep breathing, was applied. Consequently, heart rate variability and blood pressure variability in the low (LF) and high (HF) frequency range, respiration and baroreceptor sensitivity were analyzed in resting conditions and after deep breathing. The adjustment of the rhythms of the R-R interval, blood pressure and respiration partitioned for the sympathetic and the parasympathetic branch of the autonomic nervous system were quantified by the phase synchronization index γ, which has been adopted from the analysis of weakly coupled chaotic oscillators.

Results

Heart rate and LF/HF ratio increased throughout pregnancy and these effects were accompanied by a continuous loss of baroreceptor sensitivity. The increases in heart rate and LF/HF ratio levels were associated with an increasing decline in the ability to flexibly respond to additional demands (i.e., diminished adaptive responses to deep breathing). The phase synchronization index γ showed that the observed effects could be explained by a decreased coupling of respiration and the cardiovascular system (HF components of heart rate and blood pressure).

Conclusions/Significance

The findings suggest that during the course of pregnancy the individual systems become increasingly independent to meet the increasing demands placed on the maternal cardiovascular and respiratory system.     

Biocybernetic studies on reflectory heart modification in the rabbit]

In rabbits the depressor nerves and cardiac vagal branches were stimulated. Their actions on heart rate, atrio-ventricular conduction time, myocardial action potential and mean central blood pressure were recorded. The frequency-effect characteristics of the chronotropic, dromotropic and electrotropic actions on the heart, resulting from afferent and efferent nerve stimulation, are compared. The participation of each of the depressor nerves in their total effects on heart rate and blood pressure is studied. Time courses of heart rate and blood pressure decrease by afferent and efferent nerve stimulation with sinusoidally modulated pulse rates are presented. The results are discussed with respect to the different dynamics of blood pressure and heart rate control. It is concluded that at least two mechanisms are involved in blood pressure control by the depressor nerves: 1. Decrease of vascular resistance by lowering the sympathetic tone. 2. Decrease of heart rate by enhancing the cardiac vagal activity. It is suggested that the parasympathetic control unit compensates rapid disturbances, whereas the slow-acting sympathetic vascular mechanism exerts a long-time pressure control of high efficiency.     

Chronophysiology of the cardiovascular system

The development of ambulatory blood pressure monitoring devices and the beat-by-beat measurement of heart rate have enabled it to be established that there are circadian rhythms in heart rate and blood pressure in subjects living normally. Investigations of these variables have led to quantification of their fall at night, and rapid rise on awakening and becoming active in the morning. These changes are of particular interest insofar as abnormalities in them are associated with cardiovascular problems and morbidity in patients and also act as risk factors in otherwise healthy individuals. It has also been shown that there are many other variables of the cardiovascular system. The causes of the circadian rhythms in heart rate and blood pressure are outlined, with particular stress upon the role of the autonomic nervous system, as assessed from low- and high-frequency components of the variation in heart rate measured beat-by-beat. Activity increases blood pressure, but there is evidence that this “reactivity” varies with time of day, and this also might be related to cardiovascular morbidity. Based upon data from several sources, including night work, resting subjects and bed-ridden patients, it is concluded that the contribution of the “body clock” to producing the circadian rhythm in heart rate and blood pressure is relatively small. A bias towards an exogenous cause applies also to most other circadian rhythms in the cardiovascular system. Knowledge of circadian rhythmicity in cardiovascular system, together with an understanding of its causes, provides a rationale for advice to reduce cardiovascular risk and to assess the efficacy of therapies.     

Blood flow subject to a single cycle of body acceleration

The present study deals with the effect of a single cycle of body accelerations on blood flow in arteries. Such body accelerations are usually caused unintentionally, for example during travel in road vehicles, aircraft or spacecraft. A mathematical model of flow in single arteries subject to a pulsating pressure gradient due to the normal heart action as well as body acceleration expressible in terms of unit functions is presented. The body acceleration is such that it builds up from zero to a maximum value at a uniform rate, remains constant at the maximum value for some time, and thereafter reduces to zero at a uniform rate. The resulting equations are solved by using the technique of Laplace transforms. Computational results are presented for the effects of body accelerations on flow variables namely flow rate, velocity of flow, acceleration and shear stress corresponding to blood flow in the human aorta.     

A finite-element model of blood flow in arteries including taper, branches, and obstructions

A nonlinear mathematical model of arterial blood flow, which can account for tapering, branching, and the presence of stenosed segments, is presented. With the finite-element method, the model equations are transformed into a system of algebraic equations that can be solved on a high-speed digital computer to yield values of pressure and volume rate of flow as functions of time and arterial position. A model of the human femoral artery is used to compare the effects of linear and nonlinear modeling. During periods of rapid alternations in pressure or flow, the nonlinear model shows significantly different results than the linear model. The effect of a stenosis on pressure and flow waveforms is also simulated, and the results indicate that these waveforms are significantly altered by moderate and severe stenoses.     

老年肥胖型正常高值血压患者24h-动态血压变异特点及与动脉僵硬度的相关性研究

摘要 目的：探讨老年肥胖型正常高值血压患者24h-动态血压变异特点及与动脉僵硬度的相关性。方法：选择2018年1月~2020年5月期间在我院住院的老年正常高值血压患者174例作为研究对象,根据腰围分为腹型肥胖组（n=85）和非腹型肥胖组（n=89）。所有受试者监测24h-动态血压[包括24h平均收缩压（24h-SBP）、白昼平均舒张压（dDBP）、24h平均舒张压（24h-DBP）、夜间平均收缩压（nSBP）、白昼平均收缩压（dSBP）、夜间平均收缩压（nDBP）、血压变异系数（CV）]和颈-桡动脉脉搏传导速度（crPWV）,分析24h-动态血压变异性、节律性特点和crPWV的影响因素。结果：腹型肥胖组患者非杓型血压、24h-SBP-CV、24h-DBP-CV、dSBP-CV、nSBP-CV、夜间SBP下降率以及crPWV均高于非腹型肥胖组（P<0.05）,腹型肥胖组患者动脉僵硬度增高发生率高于非腹型肥胖组患者（P<0.05）。控制混杂因素后,腹型肥胖组患者腰围与夜间SBP下降率（r=0.338）、24h-SBP-CV（r=0.279）、24h-DBP-CV（r=0.259）、dSBP-CV（r=0.208）、nSBP-CV（r=0.317）、crPWV（r=0.543）呈正相关性（P<0.05）。经多元线性回归分析结果显示,腰围、LDL-C、夜间SBP下降率、24h-SBP-CV和nSBP-CV是crPWV的重要影响因素（P<0.05）。结论：腹部脂肪沉积对老年正常高值血压患者24h动态血压变异性和动脉僵硬度有显著影响,部分24h-动态血压参数与动脉僵硬度有关,控制腰围对预防动脉硬化有着重要的意义。     

Steady flow of a viscous fluid through a network of tubes with applications to the human arterial system

The paper presents a finite-element model for the analysis of steady flow of a viscous fluid through a connected system of elastic tubes with the aim of simulating the conditions of blood flow through the human arterial system. The governing equations of the model are non-linear in character and are solved through an iterative computational procedure. This model is capable of incorporating the effects of stenosis on flow and pressure. Typical results are presented and discussed. Quantitative results have been obtained on blood flow through a model of the human arterial system corresponding to the sets of prescribed conditions at the terminations. Also computational results on the effect of stenosis in typical arteries of the system are presented.     

Seeking Tau in Head Injury

The aim of this study was to determine if heart rate, blood pressure (diastolic, systolic, and mean), intracranial pressure, and cerebral perfusion pressure of patients with head injury have circadian rhythm. We studied data of 13 patients with severe head injury using the Iterative Cosinor method. We detected a circadian rhythm for at least one of the parameters in 11 (85%) of the 13 patients. The period of the rhythms (tau) was often not equal to 24 hours. Also, taus within and between patients were different. The results of our study showed that in these patients, when parameters are recorded hourly, tau can be estimated reasonably accurately (average error 0.7 hours). The distribution of taus suggests that the patients in our sample had free-running circadian rhythm. We used the surrogate data technique to validate the results of our study. Possible reasons for uncertainty in tau-estimation and proposed changes in data collection protocols and inclusion criteria are discussed.     

Seeking Tau in Head Injury

The aim of this study was to determine if heart rate, blood pressure (diastolic, systolic, and mean), intracranial pressure, and cerebral perfusion pressure of patients with head injury have circadian rhythm. We studied data of 13 patients with severe head injury using the Iterative Cosinor method. We detected a circadian rhythm for at least one of the parameters in 11 (85%) of the 13 patients. The period of the rhythms (tau) was often not equal to 24 hours. Also, taus within and between patients were different. The results of our study showed that in these patients, when parameters are recorded hourly, tau can be estimated reasonably accurately (average error 0.7 hours). The distribution of taus suggests that the patients in our sample had free-running circadian rhythm. We used the surrogate data technique to validate the results of our study. Possible reasons for uncertainty in tau-estimation and proposed changes in data collection protocols and inclusion criteria are discussed.     

Altered Orcadian Rhythms of Blood Pressure and Heart Rate in Non-Hemodialysis Chronic Renal Failure

The extended use of ambulatory monitoring has permitted the identification of many conditions in which the circadian rhythm of blood pressure is altered. The common denominator seems to be an impairment of the autonomic nervous system function. We examined whether the circadian blood pressure rhythm is altered in chronic renal failure (where autonomic dysfunction is usually present) by using a standardized chronobiological inferential statistical method in hospitalized subjects. For this purpose, a group of 30 non-hemodialysis hypertensive patients with chronic renal failure was compared with a second group of 30 patients affected by uncomplicated mild-to-moderate essential hypertension. The two groups were matched by age, sex and circadian mesors of blood pressure. Diet, meal times, sleep and activity logs were standardized. Blood pressure and heart rate recordings were obtained by using an automatic oscillometric recorder and subsequently analyzed according to the cosinor method. A mean circadian rhythm of blood pressure was documented in both groups, but while the mean acrophases occurred between 2 and 3 p.m. in essential hypertension, in renal failure they were between 11 p.m. and midnight for blood pressure and around 7 p.m. for heart rate. In addition, the mean circadian amplitudes were significantly lower in renal failure, while the mean circadian mesor of heart rate was significantly higher. Our data demonstrate that the circadian rhythms of blood pressure and heart rate are altered also in hypertension due to chronic renal failure.     

Blood pressure regulation and cardiac autonomic control in mice overexpressing alpha- and gamma-melanocyte stimulating hormone

Melanocyte stimulating hormones (MSH) derived from pro-opiomelanocortin have been demonstrated to participate in the central regulation of cardiovascular functions. The aim of the present study was to elucidate the chronic effects of increased melanocortin activation on blood pressure regulation and autonomic nervous system function. We adapted telemetry to transgenic mice overexpressing alpha- and gamma-MSH and measured blood pressure, heart rate and locomotor activity, and analyzed heart rate variability (HRV) in the frequency-domain as well as baroreflex function by the sequence technique. Transgenic (MSH-OE) mice had increased systolic blood pressure but their heart rate was similar to wild-type (WT) controls. The 24-h mean of systolic blood pressure was 132+/-7mmHg in MSH-OE and 113+/-4mmHg in WT mice. Locomotor activity was decreased in the MSH-OE mice. Furthermore, MSH-OE mice showed slower adaptation to mild environmental stress in terms of blood pressure changes. The low frequency (LF) power of HRV tended to be higher in MSH-OE mice compared to WT mice, without a difference in overall variability. The assessment of baroreflex function indicated enhanced baroreflex effectiveness and more frequent baroreflex operations in MSH-OE mice. Baseline heart rate, increased LF power of HRV and increased baroreflex activity may all reflect maintenance of baroreflex integrity and an increase in cardiac vagal activity to counteract the increased blood pressure. These results provide new evidence that long-term activation of the melanocortin system elevates blood pressure without increasing heart rate.