Changes in circulating blood volume influence aortic characteristic impedance in awake dogs

1984 ◽  
Vol 246 (4) ◽  
pp. H579-H584
Author(s):  
D. N. Stone ◽  
J. P. Dujardin ◽  
H. S. Klopfenstein ◽  
H. L. Brooks ◽  
H. P. Pieper
Keyword(s):  
Arterial Pressure ◽  
Blood Volume ◽  
Characteristic Impedance ◽  
Aortic Pressure ◽  
External Diameter ◽  
Cross Sectional ◽  
Circulating Blood Volume ◽  
Acute Hemorrhage ◽  
Catheter Tip ◽  
Chronically Instrumented Dogs

Experiments on five chronically instrumented dogs were performed to study the effects of changes in circulating blood volume on the aortic smooth muscle activity in awake animals. The external diameter of the proximal descending aorta was measured with a sonomicrometer. Aortic pressure was measured in the same cross-sectional area with a catheter-tip transducer. Acute hemorrhage of 15% of the estimated blood volume was performed 17 times by quickly withdrawing blood through a jugular cannula. At any given arterial pressure within the range of overlap the aortic diameter (D) was always decreased after hemorrhage compared with control, and the pressure-strain elastic modulus (Ep) and the characteristic impedance (Zc) were always increased. For example at 140 kdyn X cm-2 (104.5 mmHg) delta D = -0.61 +/- 0.12 mm or delta D = -3.44 +/- 0.68% of control, delta Ep = 31.0 +/- 8.6%, and delta Zc = 22.6 +/- 4.5%. Each of these changes was significant with P less than 0.01. Volume expansion of 30% was performed eight times by infusing warm saline. At any given arterial pressure D was always increased and Ep and Zc were always decreased. At 140 kdyn X cm-2 delta D = 0.55 +/- 0.15 mm or delta D = 3.12 +/- 0.95% of control, delta Ep = -12.4 +/- 3.2%, and delta Zc = -12.0 +/- 2.1%. Each of these changes was significant with P less than 0.01. Since in these awake animals the changes in circulatory blood volume modified the arterial pressure only slightly, the contribution of viscoelasticity and myogenicity to the observed responses was minimal.

scholarly journals Role of kidneys in regulation of arterial pressure in normal conditions and following changes in circulating blood volume

2019 ◽  
pp. 80-90
Author(s):  
В.О. Еркудов ◽  
А.П. Пуговкин
Keyword(s):  
Arterial Pressure ◽  
Blood Volume ◽  
Systemic Circulation ◽  
Systemic Arterial Pressure ◽  
Circulating Blood Volume ◽  
Angiotensin System ◽  
Hypothalamic Pituitary Axis ◽  
Clinically Significant ◽  
Regulation Of Blood Pressure

В лекции рассмотрено значение почечных механизмов контроля артериального давления и объёма циркулирующей крови в норме и при широко распространённых в клинической практике условиях: кровопотере и инфузии дополнительного объёма жидкости в сосудистое русло. Подчеркивается, что с почками связаны два контура регуляции кровообращения: один, где регулируемым параметром является системное артериальное давление, реализуется через ренин-ангиотензиновую систему, а второй, где регулируемым параметром является объём циркулирующей крови - через гипоталамо-гипофизарную систему. Даётся патофизиологическое описание значимости этих систем в компенсации кровопотери и её инфузионной терапии. На основании собственных экспериментальных данных объясняются методы контроля показателей системной гемодинамики, мониторинг которых крайне необходим при кровопотере и её компенсации. Материал предназначен для врачей всех специальностей, в особенности, специализирующихся в области терапии ургентных состояний, но может быть полезен студентам старших курсов медицинских учебных заведений. The review focused on contribution of renal mechanisms to regulation of blood pressure under clinically significant conditions of haemorrhage or infusion of an additional volume of fluid into the circulation. The authors underlined that kidneys are involved in two circuits of cardiovascular regulation, one of which is linked to systemic arterial pressure via the rennin-angiotensin system and the other is linked to changes in circulating blood volume via the hypothalamic-pituitary axis. Special attention is paid to participation of the rennin-angiotensin system and vasopressin in compensation and therapy for blood loss. The authors’ own experimental data are used to explain approaches for monitoring the systemic circulation. The review is addressed to physicians and senior medical students particularly interested in resuscitation and urgent therapy.

Discrepancies in Observed and Predicted Longitudinal Change in Central Hemodynamic Measures: The Framingham Heart Study

Hypertension ◽  
2021 ◽  
Author(s):  
Leroy L. Cooper ◽  
Jian Rong ◽  
Martin G. Larson ◽  
Emelia J. Benjamin ◽  
Naomi M. Hamburg ◽  
...  
Keyword(s):  
Risk Factor ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Framingham Heart Study ◽  
Aortic Stiffness ◽  
Characteristic Impedance ◽  
Longitudinal Change ◽  
Cross Sectional ◽  
Heart Study ◽  
Age Relations

Community-based studies have evaluated cross-sectional age relations of aortic stiffness measures, which are not often recapitulated in longitudinal studies. We examined baseline and longitudinal change in aortic stiffness in 5491 participants (mean age, 49.5±14.5 years; 54% women) who attended 2 sequential examinations (6.0±0.6 years apart) of the Framingham Heart Study. Cross-sectional relations of central hemodynamics (mean arterial pressure, central pulse pressure, carotid-femoral pulse wave velocity, and characteristic impedance) with age and risk factors were assessed at visits 1 and 2 (models 1 and 2). We used model 1 coefficients (M 1 ), visit 1 risk factor levels (R 1 ), and age at each visit (A 1 , A 2 ) to estimate values at visits 1 (M 1 R 1 A 1 ) and 2 (M 1 R 1 A 2 ). While using model 1 coefficients, we accounted for age and risk factor level (R 2 ) changes to predict values at visit 2 (M 1 R 2 A 2 ). Using model 2 coefficients (M 2 ) and visit 2 age and risk factor levels, we predicted visit 2 values (M 2 R 2 A 2 ). We calculated predicted change 3 ways: delta1=M 1 R 1 A 2 −M 1 R 1 A 1 , delta2=M 1 R 2 A 2 −M 1 R 1 A 1 , and delta3=M 2 R 2 A 2 −M 1 R 1 A 1 . Delta1 values were biased and correlated poorly with actual changes ( r =−0.02–0.14). For mean arterial pressure, delta1=1.9±0.8 mm Hg ( r =0.14), observed change=−3.3±10.3 mm Hg, and discrepancy=5.2±10.2 mm Hg ( P <0.0001). For characteristic impedance, delta1=7.2±14.7 dyne×sec/cm 5 ( r =0.07), observed change=20.5±68.2 dyne×sec/cm 5 , and discrepancy=−13.3±68.7 dyne×sec/cm 5 ( P <0.0001). Delta2 values were moderately correlated with change ( r =0.17–0.54) but remained biased whereas delta3 values were moderately correlated with change with no bias. Projected change in hemodynamic measures extrapolated from cross-sectional age relations may differ substantially from actual change, particularly for variables with nonlinear age relations.

Response of systemic arterial input impedance to volume expansion and hemorrhage

1980 ◽  
Vol 238 (6) ◽  
pp. H902-H908 ◽  
Author(s):  
J. P. Dujardin ◽  
D. N. Stone ◽  
L. T. Paul ◽  
H. P. Pieper
Keyword(s):  
Blood Volume ◽  
Volume Expansion ◽  
Characteristic Impedance ◽  
Aortic Pressure ◽  
Arterial System ◽  
Aortic Smooth Muscle ◽  
Direct Measurements ◽  
Dextran 70 ◽  
Anesthetized Dogs ◽  
The Mean

Experiments on 12 anesthetized dogs were performed to study the effects of changes in blood volume on the pulsatile hemodynamics of the arterial system as seen from its input. Pressure and flow were measured in the ascending aorta under control conditions, after volume expansion with dextran 70 (+30% of estimated blood volume), and after hemorrhage (-15% of estimated blood volume). The input inpedance of the arterial system was calculated for each condition. It was found that after volume expansion the characteristic impedance of the proximal aorta, Zc, was decreased by 26.6 +/- 5.1% (SE) (P less than 0.01). After hemorrhage Zc was increased by 30.4 +/- 3.4% (P less than 0.01). Since it is well known that Zc is a very weak function of the mean arterial pressure, it is concluded that the changes in Zc seen with volume expansion or hemorrhage are caused mainly by changes in aortic smooth muscle activity. This conclusion is also supported by direct measurements of aortic pressure diameter relationships in earlier work from our lab.

Pressure dependence of the mechanical properties of arteries in vivo

1975 ◽  
Vol 229 (5) ◽  
pp. 1371-1375 ◽  
Author(s):  
RH Cox
Keyword(s):  
Mechanical Properties ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Phase Velocity ◽  
Vagal Stimulation ◽  
Characteristic Impedance ◽  
External Diameter ◽  
Mean Pressure ◽  
Change In Mean

Simultaneously measurements of intra-arterial pressure and external diameter were recorded from the thoracic and abdominal aortas, the carotid, brachiocephalic, left subclavian, and femoral arteries of anesthetized dogs. Data were recorded under control conditions and during efferent vagal stimulation, and were used to compute values of wall geometry, mechanical properties, phase velocity, and characteristic impedance. Values of these parameters computed for both control and vagal stimulation were used to represent their dependence on mean arterial pressure. Both the dynamic elastic modulus and the phase velocity increased with mean pressure at each arterial site. Values of computed characteristic impedance were constant and independent of mean arterial pressure between 80--150 mmHg. The tropical application of norepinephrine (100 mug/ml) to the femoral artery produced no change in mean pressure, while external diameter and dynamic modulus were decreased, and characteristic impedance was increased. These results provide direct support for the conclusion of previous studies on vascular impedance spectra which suggested a constancy of characteristic impedance with changes in mean arterial pressure.

Arterial vasodilatory and ventricular diastolic reserves determine the stroke volume response to exercise in elderly female hypertensive patients

2011 ◽  
Vol 301 (6) ◽  
pp. H2433-H2441 ◽  
Author(s):  
Anders Sahlén ◽  
Goran Abdula ◽  
Mikael Norman ◽  
Aristomenis Manouras ◽  
Lars-Åke Brodin ◽  
...  
Keyword(s):  
High Risk ◽  
Arterial Pressure ◽  
Stroke Volume ◽  
Arterial Compliance ◽  
Characteristic Impedance ◽  
Aortic Pressure ◽  
Exponential Relationship ◽  
Hypertensive Patients ◽  
Elderly Female ◽  
End Diastolic Volume

Elderly female hypertensives with arterial stiffening constitute a majority of patients with heart failure with preserved ejection fraction (HFpEF), a condition characterized by inability to increase cardiac stroke volume (SV) with physical exercise. As SV is determined by the interaction between the left ventricle (LV) and its load, we wished to study the role of arterial hemodynamics for exertional SV reserve in patients at high risk of HFpEF. Twenty-one elderly (67 ± 9 yr) female hypertensive patients were studied at rest and during supine bicycle stress using echocardiography including pulsed-wave Doppler to record flow in the LV outflow tract and arterial tonometry for central arterial pressure waveforms. Arterial compliance was estimated based on an exponential relationship between pressure and volume. The ratio of aortic pressure-to-flow in early systole was used to derive characteristic impedance, which was subsequently subtracted from total resistance (mean arterial pressure/cardiac output) to yield systemic vascular resistance (SVR). It was found that patients with depressed SV reserve ( NoRes; reserve <15%; n = 10) showed decreased arterial compliance during exercise, while patients with SV reserve ≥15% ( Res; n = 11) showed increased compliance. Exercise produced parallel increases in LV end-diastolic volume and arterial volume in Res patients while NoRes patients exhibited a lesser decrease in SVR and a drop in effective arterial volume. Poor SV reserve in elderly female hypertensives is due to simultaneous failure of LV preload and arterial vasodilatory reserves. Abnormal arterial function contributes to a high risk of HFpEF in these patients.

Dorsal aortic impedance in stage 24 chick embryo following acute changes in circulating blood volume

1996 ◽  
Vol 270 (5) ◽  
pp. H1597-H1606 ◽  
Author(s):  
M. Yoshigi ◽  
N. Hu ◽  
B. B. Keller
Keyword(s):  
Blood Volume ◽  
Arterial Compliance ◽  
Characteristic Impedance ◽  
Peripheral Resistance ◽  
Dependent Manner ◽  
Mean Flow ◽  
Windkessel Model ◽  
Hydraulic Power ◽  
Circulating Blood Volume ◽  
Acute Changes

The effects of acute changes in circulating blood volume on embryonic vascular hemodynamics were evaluated with the use of input impedance. We simultaneously measured dorsal aortic pressure with a servo-null system and flow velocity with a 20-MHz pulsed Doppler system in n = 90 stage 24 chick embryos. We withdrew or infused 1,3, or 5 microliters of blood via a second-order vitelline vein (n = 10 per group). In addition, we withdrew and then infused or infused and then withdrew 3 microliters (n = 5 per group). Characteristic impedance, peripheral resistance, arterial compliance and elastance, and hydraulic power as well as basic hemodynamic parameters were evaluated on the basis of the three-element windkessel model. In response to withdrawal, mean and pulse pressure, mean flow, arterial compliance, and hydraulic power decreased, whereas peripheral resistance and arterial elastance increased in a dose-dependent manner. Results in response to infusion were converse in effect. Characteristic impedance was unchanged by volume alternations. Oscillatory fraction of hydraulic power was higher than mature circulation and remained relatively constant during interventions, which indicates well-regulated energy efficiency for vascular growth in the embryonic circulation. A hysteresis relevant to altered peripheral resistance was present after multiple interventions. Embryonic vasculature is sensitive to circulating blood volume and preserve blood pressure at the expense of blood flow. In the absence of autonomic innervation, embryonic vascular tone may be regulated by mechanical properties of the vessel (the law of Laplace) and/or vasoactive substances.

Hemodynamic sensing using subcutaneous photoplethysmography

2008 ◽  
Vol 295 (6) ◽  
pp. H2560-H2572 ◽  
Author(s):  
Robert G. Turcott ◽  
Todd J. Pavek
Keyword(s):  
Arterial Pressure ◽  
Blood Volume ◽  
Correlation Coefficients ◽  
Aortic Pressure ◽  
Scatter Plots ◽  
Rapid Pacing ◽  
Acute Changes ◽  
Hemodynamic Information ◽  
Induced Changes ◽  
Av Delay

Pacemakers and implantable defibrillators presently operate without access to hemodynamic information. If available, such data would allow tailoring of delivered therapy according to perfusion status, optimization of device function, and enhancement of disease monitoring and management. A candidate method for hemodynamic sensing in these devices is photoplethysmography (PPG), which uses light to noninvasively detect changes in blood volume. The present study tested the hypotheses that PPG can function in a subcutaneous location, that the acute changes in blood volume it detects are directly proportional to changes in arterial pressure, and that optimum pacing intervals identified by it are concordant with those determined by arterial pressure. Aortic pressure and PPG were simultaneously recorded in 10 dogs under general anesthesia during changes in atrioventricular (AV) delay and bursts of rapid pacing to simulate tachyarrhythmias. Direct proportionality between transient changes in pressure and PPG waveforms was tested using regression analysis. Scatter plots had a linear appearance, with correlation coefficients of 0.95 (SD 0.03) and 0.72 (SD 0.24) for rapid-pacing and AV delay protocols, respectively. The data were well described by a directly proportional relationship. Optimum AV delays estimated from the induced changes in aortic pressure and PPG waveforms were concordant. This preliminary canine study demonstrates that PPG can function subcutaneously and that it may serve as a surrogate for acute changes in arterial pressure.

Sign in / Sign up

Export Citation Format

Share Document