In order to study the cardiovascular hemodynamic characteristics and evaluate the blood pump, we made a series of cardiovascular simulation devices which could reflect the hemodynamics of blood circulation system by the elastic chamber model, and tested the relations between cardiovascular hemodynamic parameters (such as systole pressure, diastole pressure, average pressure, pulsative pressure, flow rate) and ventricular afterload (peripheral resistance and vascular compliance) as well as cardiac output, diastolic period, systole period and preload. The effect of the parameters on the arterial pressure and flow rate was estimated when any one of the parameters was changed. The result of simulating experiment was coincided with that deduced from mathematical model and physiologic condition. Therefore the series of cardiovascular simulation devices can reflect the hemodynamics of blood circulation.
Blood Pressure ; physiology ; Cardiac Output ; physiology ; Cardiovascular Physiological Phenomena ; In Vitro Techniques ; Models, Cardiovascular ; Vascular Resistance ; physiology

BACKGROUNDEchocardiography is regarded as a gold standard for measuring hemodynamic values. The ultrasonic cardiac output monitor (USCOM) is a new method for measuring hemodynamics and could provide non-invasive point of care guidance. So far, there are no published USCOM reference values for neonates, nor has USCOM's accuracy been established in this population. We aimed to determine the accuracy and clinical utility of the USCOM in healthy neonates relative to published echocardiographic data, to establish normal hemodynamic parameters that it measures, and to assess the possible role of USCOM as an alternative to echocardiography as a trend monitor.

METHODSRight and left heart hemodynamics of 90 normal neonates were measured during circulatory adaptation over the first three days of life using the USCOM and automated oscillotonometry.

RESULTSHeart rate showed a significant decline from days one to three, from 126 to 120 (P < 0.001). Systolic, diastolic and mean arterial pressures all increased significantly from 66 to 71 mmHg, 33 to 38 mmHg and 44 to 49 mmHg, respectively (P < 0.001 in each case). Right ventricular cardiac index (RV-CI) showed no change with a mean of 5.07 L × min(-1) × m(-2). Left ventricular cardiac index (LV-CI) declined from 3.43 to 3.00 L × min(-1) × m(-2) (P < 0.001). RV-CI exceeded LV-CI on all three days by a mean of 61%. The systemic vascular resistance index (SVRI), based on LV-CI, increased significantly over the three days from 1083 to 1403 dyne × sec × cm(-5) × m(2) (P < 0.001).

CONCLUSIONSNormal neonatal hemodynamic values, as indicated by USCOM, were established. LV-CI measurement showed excellent agreement with published echocardiographic studies. RV-CI was constant and exceeded LV-CI for all three days of this study. It may be falsely high due to flow velocity measurement errors arising from the pulmonary branch arteries, and may represent a limitation of the USCOM method. The progressive rise of arterial pressure and SVRI despite a declining LV-CI may indicate functional closure of the ductus arteriosus, with the greatest change occurring within the first 24 hours. Evidence of closure of the foramen ovale was not observed.

Cardiac Output ; physiology ; Female ; Heart Rate ; physiology ; Hemodynamics ; physiology ; Humans ; Infant, Newborn ; Male ; Monitoring, Physiologic ; instrumentation ; methods ; Ultrasonography ; instrumentation ; methods

OBJECTIVETo observe the regulation of heart rate to cardiac pump function in the phase of negative force-frequency relationship and their possible mechanisms.

METHODSThe left ventricular pressure, aortic pressure, and cardiac output were measured in isolated working heart of rat from 240 to 300 beats/min of pacing rate.

RESULTSCardiac output of isolated working heart was decreased by a proximally 20% (P < 0.01) with the increase in the pacing rate from 240 to 300 beats/min. Left ventricular end-systolic pressure (LVESP) was declined by 4.8% (P < 0.05), but left ventricular end-diastolic pressure (LVEDP) was elevated by 139% (P < 0.01) with an increase in the pacing rate. Left atrium was enlarged at 300 beats/min of pacing rate. The time from peak to 75% relaxation in left ventricular pressure was shortened with the increased pacing rate. Pressure at aortic valve close was raised (P < 0.01) and ejection duration was shortened with the increased pacing rate (P < 0.01).

CONCLUSIONThose above results suggest that there are different mechanisms between the depressed cardiac output at higher heart rate and negative force-frequency relationship. The frequency-dependent acceleration of relaxation facilitates the decline of left ventricular pressure, and then may elevate the pressure of aortic valve close in the condition that the shape of aortic pressure curve stays the same. Therefore, the ejection duration is shortened at higher pacing rate. The shortened ejection duration may induce a decrease in stroke volume of the left ventricle. The increment of heart rate is not enough to compensate the decreased stroke volume. Finally, cardiac output shows a decrease at higher heart rate.

Animals ; Blood Pressure ; Cardiac Output ; Heart Rate ; physiology ; Male ; Pressoreceptors ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study the clinical application of ultrasonic cardiac output monitor (USCOM) in evaluation of cardiac function in children with severe pneumonia.

METHODSTwenty-nine children with severe pneumonia were enrolled in the observation group and forty-three children with common pneumonia were enrolled in the control group. The USCOM was used to measure the cardiac function indices in the two groups. The results were compared between the two groups. The changes in cardiac function indices after treatment were evaluated in the observation group.

ESULTSThe observation group had a significantly higher heart rate and significantly lower cardiac output, systolic volume, and aortic peak velocity than the control group (P<0.05). There were no significant differences in cardiac index or systemic vascular resistance between the two groups (P>0.05). In the observation group, the heart rate, cardiac output, systolic volume, aortic peak velocity, cardiac index, and systemic vascular resistance were significantly improved after treatment (P<0.05).

CONCLUSIONSThe USCOM is a fast, convenient, and accurate approach for dynamic measurement of cardiac function and overall circulation state in children with severe pneumonia. The USCOM can provide a basis for diagnosis, treatment, and evaluation of the disease, which is quite useful in clinical practice.

Cardiac Output ; physiology ; Child ; Female ; Humans ; Infant ; Male ; Monitoring, Physiologic ; instrumentation ; Pneumonia ; physiopathology ; Ultrasonics

Principle of ambulatory cardiac output (CO) measuring technique is introduced in this paper. A lot of experimental studies of the current distribution on the thorax under the condition that the current injection electrodes were adhered to different positions were carried out by using a developed multi-channel impedance mapping system. The static impedance contour maps (Zo-map) and its pulsatile component contour maps (deltaZ-map) under different measuring conditions were analyzed, and the applicability of a two-compartment coaxial cylindrical model using a spot-electrode array instead of the conventional band-electrode array for ambulatory CO measurement, as well as the optimal spot-electrode array, were discussed. Based on the experimental results and the daily use of the ambulatory CO measuring technique, the optimal spot-electrode array meeting the condition of the two-compartment coaxial cylindrical model was determined as that a pair of spot-electrodes for current injection was located on the positions behind the ears and on the right lower abdomen, and a pair of spot-electrodes for voltage pick-up places on the medial portion at the level of clavicle and on the portion above the xiphisternum.
Cardiac Output ; physiology ; Cardiography, Impedance ; methods ; Electric Impedance ; Electrodes ; Equipment Design ; Humans

AIMTo introduce a new device and catheter to be determining cardiac output through cor sinistrum with thermodilution.

METHODSOwn control was introduced in eight dogs. A pulmonary thermodilution catheter was used through the cor dextrum of the dogs; The new-design catheter was used through artery, and there were two situs to fix:its ahead in left atrium and the ahead near to aortic root. Determine cardiac output (CO) under four circumstances: controlled respiration, apnoea, in controlled hypotension, after controlled hypotension.

RESULTSThere was no significant difference among the parameters (CO and cardiac index) of all circumstances. The CO determined by the pulmonary thermodilution catheter and those by the new-design catheter in two situs were positive correlation, and the gamma were 0.986, 0.989; likewise, the cardiac index (CI) was positive correlation, and the gamma were 0.983, 0.985. The CO and CI by the new-design catheter between two situs were positive, and the gamma were 0.992, 0.988.

CONCLUSIONThe parameters by the new-design catheter and those by the pulmonary thermodilution catheter were concordant. In comparison with the pulmonary thermodilution catheter, the new-design catheter had simple device and could be easily operated.

Animals ; Cardiac Output ; physiology ; Catheterization, Swan-Ganz ; instrumentation ; Dogs ; Thermodilution ; methods

Pulse contour cardiac output (PiCCO) monitoring is a new type of invasive hemodynamic monitoring technology, which is more and more often applied in perioperative period and the patients suffering from multiple injuries, septic shock, and extensive burn. With PiCCO one is able to monitor patients' hemodynamic indexes safely, timely, accurately, and continuously to provide reference for judgment of patients' condition and proper quality and quantity of fluid administration. This technique has a good prospect in clinical application.
Cardiac Output ; physiology ; Fluid Therapy ; methods ; Hemodynamics ; Humans ; Monitoring, Physiologic ; instrumentation

BACKGROUND: It is still unclear what the minimal infusion volume is to effectively predict fluid responsiveness. This study was designed to explore the minimal infusion volume to effectively predict fluid responsiveness in septic shock patients. Hemodynamic effects of fluid administration on arterial load were observed and added values of effective arterial elastance (Ea) in fluid resuscitation were assessed. METHODS: Intensive care unit septic shock patients with indwelling pulmonary artery catheter (PAC) received five sequential intravenous boluses of 100 mL 4% gelatin. Cardiac output (CO) was measured with PAC before and after each bolus. Fluid responsiveness was defined as an increase in CO >10% after 500 mL fluid infusion. RESULTS: Forty-seven patients were included and 35 (74.5%) patients were fluid responders. CO increasing >5.2% after a 200 mL fluid challenge (FC) provided an improved detection of fluid responsiveness, with a specificity of 80.0% and a sensitivity of 91.7%. The area under the ROC curve (AUC) was 0.93 (95% CI: 0.84-1.00, P  < 0.001). Fluid administration induced a decrease in Ea from 2.23 (1.46-2.78) mmHg/mL to 1.83 (1.34-2.44) mmHg/mL (P = 0.002), especially for fluid responders in whom arterial pressure did not increase. Notably, the baseline Ea was able to detect the fluid responsiveness with an AUC of 0.74 (95% CI: 0.59-0.86, P < 0.001), whereas Ea failed to predict the pressure response to FC with an AUC of 0.50 (95% CI: 0.33-0.67, P = 0.086). CONCLUSION: In septic shock patients, a minimal volume of 200 mL 4% gelatin could reliably detect fluid responders. Fluid administration reduced Ea even when CO increased. The loss of arterial load might be the reason for patients who increased their CO without pressure responsiveness. Moreover, a high level of Ea before FC was able to predict fluid responsiveness rather than to detect the pressure responsiveness. TRIAL REGISTRATION ClinicalTrials.gov, NCT04515511.
Cardiac Output/physiology* ; Fluid Therapy ; Gelatin/therapeutic use* ; Hemodynamics ; Humans ; Shock, Septic/therapy*

Fontan circulation is generally characterized by high central venous pressure, low cardiac output, and slightly low arterial oxygen saturation, and it is quite different from normal biventricular physiology. Therefore, when a patient with congenital heart disease is selected as a candidate for this type of circulation, the ultimate goals of therapy consist of 2 components. One is a smooth adjustment to the new circulation, and the other is long-term circulatory stabilization after adjustment. When either of these goals is not achieved, the patient is categorized as having “failed” Fontan circulation, and the prognosis is dismal. For the first goal of smooth adjustment, a lot of effort has been made to establish criteria for patient selection and intensive management immediately after the Fontan operation. For the second goal of long-term circulatory stabilization, there is limited evidence of successful strategies for long-term hemodynamic stabilization. Furthermore, there have been no data on optimal hemodynamics in Fontan circulation that could be used as a reference for patient management. Although small clinical trials and case reports are available, the results cannot be generalized to the majority of Fontan survivors. We recently reported the clinical and hemodynamic characteristics of early and late failing Fontan survivors and their association with all-cause mortality. This knowledge could provide insight into the complex Fontan pathophysiology and might help establish a management strategy for long-term hemodynamic stabilization.
Cardiac Output ; Cardiac Output, Low ; Central Venous Pressure ; Fontan Procedure ; Heart Defects, Congenital ; Hemodynamics* ; Humans ; Mortality ; Oxygen ; Patient Selection ; Physiology ; Prognosis ; Survivors ; Vascular Resistance

The control arithmetic is proposed for axial blood pump driven by extracorporeal alternating magnet field based on ventricular work. According to health physiological parameters, the control model is verified by calculation and experiment. The control model used for driving blood pump is derived from the relationship of natural heart and artificial heart. By comparison with others, the control arithmetic based on ventricular work is more helpful in appraising the property of left ventricular aided device (LVAD), in meeting human body's natural need, and in effective use of motor for avoiding motor running at high speed and hence preventing the blood from the destruction caused by a blood pump at high temperature.
Algorithms ; Cardiac Output ; physiology ; Computer Simulation ; Heart Ventricles ; Heart-Assist Devices ; Hemorheology ; Humans ; Models, Cardiovascular ; Ventricular Function, Left ; physiology