scholarly journals The view of the native gauges of blood pressure - focus on atrium (hydrodynamics and rheology)

2016 ◽  
Author(s):  
Yuri Kamnev
Keyword(s):  
Venous Pressure ◽  
Outer Radius ◽  
Viscoelastic Deformation ◽  
Viscous Deformation ◽  
Specific Distribution ◽  
Component Velocity ◽  
The One ◽  
Coefficient Of Viscosity ◽  
Ventricular Filling ◽  
Velocity Pressure

The precision of the inlet parameters depends on mechanism of response. Reflexes are satisfied with relative higher or lower but if the inlet information is presented by different parameters and the response is calculated according to some equation precision must reach the degree which does not slur over the results of calculation. At recent work the equation for controlling of circulation was suggested where the main inlet parameters are the arterial diastolic and vinous pressures and it becomes pertinent to analyze how organism can perceive these pressures with hydrodynamic accuracy. As far as the velocity pressure component of total pressure can not be detected by wall receptor of the rectilinear section of artery it was noticed that baroreceptors are located at the outer radius of the bend of central arteries and that is justified due to specific distribution of pressure. This phenomenon can be interpreted as a correction of measuring of static pressure with regard for velocity pressure component. Velocity pressure component of venous pressure is comparable with the one of arterial pressure but static components of venous and arterial pressures are incomparable and it is the fact that cannot be ignored when choosing the gauge. The possible method of measuring of pressure is based on observation that pressure-volume vector of the ventricular cycle is similar to a-loop vector of atrial cycle. Ventricular filling vector and x-trough vector show the behavior of viscous material but v-loop inserted into a-loop demonstrates typical viscoelasticity with creep. If viscous deformation of atrium at early relaxation possesses standard duration being stopped by transformation of viscous deformation into viscoelastic deformation the venous pressure can be measured in accordance with the value of viscous deformation. Measuring of pressure by viscous method implemented by atrium has the advantage comparing to measuring by baroreceptor with elastic sensor. Early relaxation of atrium which reveals coefficient of viscosity corresponds to ventricular relaxation and its coefficient of viscosity but the latter is liable to different biochemical shifts. Such shifts influences the atrial coefficient of viscosity either and the values of venous pressure measured by viscous method will be more accurate for calculations because coefficient of viscosity participates in the equation being not estimated in organism.

scholarly journals Viscous deformation of relaxing ventricle and pulsatile blood propelling (numerical model)

2014 ◽  
Author(s):  
Yuri Kamnev
Keyword(s):  
Numerical Model ◽  
Volume Flow Rate ◽  
Venous Pressure ◽  
Ventricular Volume ◽  
Volume Flow ◽  
Viscous Deformation ◽  
Operating Range ◽  
Independent Variables ◽  
Dimensional Argument ◽  
Ventricular Filling

AbstractThe numerical model of one-loop circulation exploits viscous deformation as mechanism of ventricular filling. Mathematical advantage of viscous deforming is a possibility to present the ventricular filling as the function of two independent variables (stress and time); two-dimensional argument frames a table which permits to calculate end-diastolic ventricular volume due to information about measured venous pressure and duration of ventricular diastole. The equation was deduced which balances the system while varying of such parameters as arterial resistance, the value of normal rhythm and the volume flow rate. The model pays attention on the phenomenon of asymmetrical position of normal rhythm (the steady rhythm in conditions of rest) and explains why the operating range of brady-rhythms is much narrower than the operating range of tachy-rhythms.

Effect of vasopressin on systemic capacity

1991 ◽  
Vol 261 (5) ◽  
pp. H1494-H1498 ◽  
Author(s):  
F. G. Welt ◽  
D. L. Rutlen
Keyword(s):  
Intact Animal ◽  
Venous Pressure ◽  
Portal Venous Pressure ◽  
Portal Flow ◽  
Compensatory Response ◽  
Venae Cavae ◽  
Subsequent Decrease ◽  
Constant Rate ◽  
Arterial Inflow ◽  
Ventricular Filling

To assess the effect of vasopressin (VP) on systemic capacity (SC), blood was drained from the venae cavae to an oxygenator and returned to the aorta at a constant rate so that changes in SC could be measured as the inverse of changes in oxygenator volume in 17 anesthetized pigs. After 10 min of VP administration (1.1 U/min ia), mean arterial pressure increased from 67 +/- 2 to 144 +/- 7 mmHg (P less than 0.001). SC decreased promptly and reached a nadir of 110 +/- 32 ml (P less than 0.02, 5.5 ml/kg) below control at 5 min but returned to 35 +/- 65 ml (P = not significant, 1.8 ml/kg) below control at 10 min. Portal venous pressure decreased from 19.3 +/- 2.6 to 16.6 +/- 2.7 mmHg (P less than 0.001), and portal flow decreased from 828 +/- 68 to 458 +/- 92 ml/min (P less than 0.001). Transhepatic venous resistance increased. After evisceration, VP caused only an increase in SC. Thus VP causes an initial SC decrement due entirely to a decrease in splanchnic capacity. The decrease in splanchnic capacity must be caused, at least in part, by the decrease in gastrointestinal arterial inflow and subsequent decrease in portal venous pressure. These initial effects of VP on SC would be expected to enhance ventricular filling and cardiac output in the intact animal and could be important in the acute compensatory response to hemorrhage.

Mechanical Assistance for the Fontan Circulation Using an Intravascular Axial Flow Blood Pump

2010 ◽  
Author(s):  
Sonya S. Bhavsar ◽  
William B. Moskowitz ◽  
Amy L. Throckmorton
Keyword(s):  
Venous Pressure ◽  
Vena Cava ◽  
Axial Flow ◽  
Blood Pump ◽  
Pharmacologic Therapy ◽  
Mechanical Pressure ◽  
Fontan Patient ◽  
Axial Flow Blood Pump ◽  
Ventricular Filling ◽  
Failing Fontan

Research indicates that an afterload reducing agent improves ventricular-vascular interactions and Fontan hemodynamics [1]. Few such therapeutic alternatives exist for the failing Fontan patient beyond conventional pharmacologic therapy. To address this need for therapeutic options, we are developing an intravascular, magnetically levitated axial flow blood pump to support the total cavopulmonary connection (TCPC) of a failing Fontan in adolescent and adult patients [1,2]. Our pump is designed to provide mechanical pressure augmentation of blood flow from the inferior vena cava (IVC) to the lungs, thus improving systemic venous pressure and increasing ventricular filling.

scholarly journals Hemodynamics during the 10-Minute NASA Lean Test: Evidence of circulatory decompensation in a subset of ME/CFS patients

2020 ◽  
Author(s):  
Jihyun Lee ◽  
Suzanne D Vernon ◽  
Patricia Jeys ◽  
Weam Ali ◽  
Andrea Campos ◽  
...  
Keyword(s):  
Heart Rate ◽  
Pulse Pressure ◽  
Orthostatic Intolerance ◽  
Point Of Care ◽  
Venous Pressure ◽  
Chronic Fatigue ◽  
Exercise Intolerance ◽  
Hemodynamic Changes ◽  
Fatigue Syndrome ◽  
Ventricular Filling

Abstract Background. Lightheadedness, fatigue, weakness, heart palpitations, cognitive dysfunction, muscle pain, and exercise intolerance are some of the symptoms of orthostatic intolerance (OI). There is substantial comorbidity of OI in ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome). The 10-minute NASA Lean Test (NLT) is a simple, point-of-care method that can aid ME/CFS diagnosis and guide management and treatment of OI. The objective of this study was to understand the hemodynamic changes that occur in ME/CFS patients during the 10-minute NLT. Methods. A total of 150 ME/CFS patients and 75 age, gender and race matched healthy controls (HCs) were enrolled. We recruited 75 ME/CFS patients who had been sick for less than 4 years (<4 ME/CFS) and 75 ME/CFS patients sick for more than 10 years (>10 ME/CFS). The 10-minute NLT involves measurement of blood pressure and heart rate while resting supine and every minute for 10 minutes while standing with shoulder-blades on the wall for a relaxed stance. Spontaneously reported symptoms are recorded during the test. ANOVA and regression analysis were used to test for differences and relationships in hemodynamics, symptoms and upright activity between groups.Results. At least 5 minutes of the 10-minute NLT were required to detect hemodynamic changes. The <4 ME/CFS group had significantly higher heart rate and abnormally narrowed pulse pressure compared to >10 ME/CFS and HCs. The <4 ME/CFS group experienced significantly more OI symptoms compared to >10 ME/CFS and HCs. The circulatory decompensation observed in the <4 ME/CFS group was not related to age or medication use. Conclusions. Circulatory decompensation characterized by increased heart rate and abnormally narrow pulse pressure was identified in a subgroup of ME/CFS patients who have been sick for <4 years. This suggests inadequate ventricular filling from low venous pressure. The 10-minute NLT can be used to diagnose and treat the circulatory decompensation in this newly recognized subgroup of ME/CFS patients. The >10 ME/CFS group had less pronounced hemodynamic changes during the NLT possibly from adaptation and compensation that occurs over time. The 10-minute NLT is a simple and clinically useful point-of-care method that can be used for early diagnosis of ME/CFS and help guide OI treatment.

scholarly journals The activation energy of viscoelastic deformation of rocks

2003 ◽  
pp. 101-105
Author(s):  
Dzhema Melkonyan
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Temperature Dependence ◽  
Probabilistic Approach ◽  
Deformation Energy ◽  
Total Probability ◽  
Suggested Model ◽  
Viscoelastic Deformation ◽  
Viscous Deformation

The suggested model, which considers the simultaneous appearance (on the intermolecular scale) of elastic and viscous behaviors of rocks during their viscoelastic deformation, enables the relaxation time, t0, of the viscoelastic deformation energy to be defined. By determination of t0, the activation energies of the elastic and viscous deformation can be separated from the temperature dependence of the viscoelastic deformation energy stream U. The probabilistic approach to viscoelastic deformation of rocks allows the introduction of the a notion of the total probability, consisting of the probabilities of elastic and viscous deformations.

Designing variable control charts under failure censoring reliability tests with replacement

2020 ◽  
Vol 42 (15) ◽  
pp. 3002-3011
Author(s):  
Hasan Rasay ◽  
Hossein Arshad
Keyword(s):  
Control Charts ◽  
Type I Error ◽  
Average Run Length ◽  
Quality Characteristic ◽  
Erlang Distribution ◽  
Type I ◽  
Chi Square ◽  
Variable Control ◽  
Specific Distribution ◽  
The One

There exist many processes where the quality characteristic does not follow a normal distribution, and the conditions for the application of central limit theorem are not satisfied; for example, because collecting data in a subgroup is impossible or the distribution is highly skewed. Thus, researchers have developed the control charts according to the specific distribution that models the quality characteristic. In this paper, some control charts are designed to monitor an exponentially distributed lifetime. The life testing is conducted according to the failure censoring while during the test; once observing a failure item, it is replaced by a new one so that the total number of items inspected during the test remains constant. Under the condition of the test, it is discussed that the elapsed time until observing the r’th failure has Erlang distribution. According to the relation of Erlang and chi-square distributions, the chart limits are computed to satisfy a specified value of type I error. Examples are presented and the curves of average run length are derived for the one-sided and two-sided control charts. Also, a comparative study is conducted to show the performance and superiority of the proposed control charts.

scholarly journals Hemodynamics During the 10-Minute NASA Lean Test: Evidence of Circulatory Decompensation in a Subset of ME/CFS Patients

2020 ◽  
Author(s):  
Jihyun Lee ◽  
Suzanne D Vernon ◽  
Patricia Jeys ◽  
Weam Ali ◽  
Andrea Campos ◽  
...  
Keyword(s):  
Heart Rate ◽  
Pulse Pressure ◽  
Orthostatic Intolerance ◽  
Point Of Care ◽  
Venous Pressure ◽  
Chronic Fatigue ◽  
Exercise Intolerance ◽  
Hemodynamic Changes ◽  
Fatigue Syndrome ◽  
Ventricular Filling

Abstract Background Lightheadedness, fatigue, weakness, heart palpitations, cognitive dysfunction, muscle pain, and exercise intolerance are some of the symptoms of orthostatic intolerance (OI). There is substantial comorbidity of OI in ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome). The 10-minute NASA Lean Test (NLT) is a simple, point-of-care method that can aid ME/CFS diagnosis and guide management and treatment of OI. The objective of this study was t o understand the hemodynamic changes that occur in ME/CFS patients during the 10-minute NLT. Methods A total of 150 ME/CFS patients and 75 age, gender and race matched healthy controls (HCs) were enrolled. We recruited 75 ME/CFS patients who had been sick for less than 4 years (<4 ME/CFS) and 75 ME/CFS patients sick for more than 10 years (>10 ME/CFS). The 10-minute NLT involves measurement of blood pressure and heart rate while resting supine and every minute for 10 minutes while standing with shoulder-blades on the wall for a relaxed stance. Spontaneously reported symptoms are recorded during the test. ANOVA and regression analysis were used to test for differences and relationships in hemodynamics, symptoms and upright activity between groups. Results At least 5 minutes of the 10-minute NLT were required to detect hemodynamic changes. The <4 ME/CFS group had significantly higher heart rate and abnormally narrowed pulse pressure compared to >10 ME/CFS and HCs. The <4 ME/CFS group experienced significantly more OI symptoms compared to >10 ME/CFS and HCs. The circulatory decompensation observed in the <4 ME/CFS group was not related to age or medication use. Conclusions Circulatory decompensation characterized by increased heart rate and abnormally narrow pulse pressure was identified in a subgroup of ME/CFS patients who have been sick for <4 years. This suggests inadequate ventricular filling from low venous pressure. The 10-minute NLT can be used to diagnose and treat the circulatory decompensation in this newly recognized subgroup of ME/CFS patients. The >10 ME/CFS group had less pronounced hemodynamic changes during the NLT possibly from adaptation and compensation that occurs over time. The 10-minute NLT is a simple and clinically useful point-of-care method that can be used for early diagnosis of ME/CFS and help guide OI treatment.

Probing of Flow Fields with Shock Waves—The Swing Probe

1971 ◽  
Vol 49 (10) ◽  
pp. 1340-1349 ◽  
Author(s):  
J. D. Strachan ◽  
B. Ahlborn
Keyword(s):  
Shock Waves ◽  
Source Term ◽  
Flow Fields ◽  
Inhomogeneous Media ◽  
Shock Propagation ◽  
Local Velocity ◽  
One Dimensional ◽  
Density Distributions ◽  
The One ◽  
Velocity Pressure

The one dimensional equations governing shock propagation into inhomogeneous media have been developed to allow a shock to be used as a probe. Shock waves which collide with unknown gas or plasma flow fields suffer a change in velocity. Pressure, density, particle velocity, and local energy input at the edge of an unknown flow can be determined from the measurement of unknown flow. The steady variation of the velocity of strong probing shocks reveals details of the local velocity and density distributions inside the unknown flow field. One further result is the extension of the general theory of shock propagation into inhomogeneous media to cover the case when an energy source term appears at the front.

Pitfalls of venous occlusion method for determination of capillary pressure in humans

1989 ◽  
Vol 66 (2) ◽  
pp. 997-1002
Author(s):  
B. Braam ◽  
H. A. Koomans ◽  
T. J. Rabelink ◽  
R. Berckmans
Keyword(s):  
Capillary Pressure ◽  
Venous Pressure ◽  
Venous Occlusion ◽  
Upper Arm ◽  
Basic Principles ◽  
Venous Valves ◽  
Large Pressure ◽  
Cubital Fossa ◽  
The One

We tested the method of estimating capillary pressure from venous pressure transients obtained after sudden venous clamping in a hydrodynamic model. The basic principles were confirmed in the model, but it was found that when occlusion was caused over a relatively wide distance or in a predistended vessel, capillary pressure was overrated. This problem was due to volume backflow from the occlusion site, since it could be eliminated by placing a one-way valve upstream from the occlusion site. Upstream from the valve, the venous pressure transient accurately followed capillary pressure. Downstream, however, the reading of capillary pressure was impaired by the backflow volume squeezed between valve and occlusion clamp, which caused an immediate large pressure elevation. We also tested the method recently advanced to estimate capillary pressure in humans from venous pressure curves obtained after rapid venous occlusion with an air-filled compression cuff. With the cuff around the upper arm, venous pressure was recorded at different levels along the forearm. The tracings obtained from the dorsum of the hand and halfway along the forearm did not show the initial rapid upstrokes that might indicate the capillary pressure. Tracings obtained slightly below or above the cubital fossa were similar to those seen downstream from the one-way valve in the model. Extrapolation to zero-time, using the distally recorded curves as a template, yielded values equal to venous pressure. We conclude that although the problem of backflow can be circumvented by pressure recording distal from venous valves, the method of venous occlusion by a circular upper-arm cuff may not be appropriate to estimate capillary pressure in humans.

Muscle metaboreflex increases ventricular performance in conscious dogs

1998 ◽  
Vol 275 (1) ◽  
pp. H220-H224 ◽  
Author(s):  
Donal S. O’Leary ◽  
Robert A. Augustyniak
Keyword(s):  
Venous Pressure ◽  
Vascular Occlusion ◽  
Systemic Arterial Pressure ◽  
Ventricular Contractility ◽  
Ventricular Performance ◽  
Muscle Metaboreflex ◽  
Filling Time ◽  
Reflex Activation ◽  
Ventricular Filling ◽  
Chronically Instrumented Dogs

Ischemia of active skeletal muscle stimulates neuronal afferents within the muscle, which elicits a reflex increase in systemic arterial pressure (SAP), heart rate (HR), and cardiac output (CO) termed the muscle metaboreflex. We investigated whether activation of the muscle metaboreflex elicits increases in ventricular performance using conscious, chronically instrumented dogs trained to run on a treadmill (3.2 km/h, 0% grade). The muscle metaboreflex was activated via progressive partial vascular occlusion of the terminal aorta during control experiments and with HR maintained constant via a pacemaker connected to ventricular electrodes (225 beats/min). In control experiments, hindlimb ischemia elicited substantial increases in SAP, HR, and CO (+53.9 ± 4.3 mmHg, +32.4 ± 4.5 beats/min, and +1.57 ± 0.22 l/min, respectively; all changes P < 0.05), whereas stroke volume (SV) remained unchanged with reflex activation (control 45.9 ± 2.3 vs. 46.1 ± 2.4 ml, P > 0.05). During metaboreflex activation at constant HR, SV significantly increased such that the increases in CO and SAP were not significantly different from control experiments (+1.77 ± 0.56 l/min and +57.4 ± 3.8 mmHg, P > 0.05 vs. control experiments). No significant change in central venous pressure occurred in either experiment, indicating no Frank-Starling effect on SV. We conclude that muscle metaboreflex-induced increases in ventricular contractility act to sustain SV despite decreases in ventricular filling time due to the tachycardia such that the sustained SV coupled with the tachycardia elicits substantial increases in CO that contribute importantly to the reflex increase in SAP.

Sign in / Sign up

Export Citation Format

Share Document