Phornphop Naiyanetr

Left Ventricle Afterload Impedance Control by an Axial Flow Ventricular Assist Device: A Potential Tool for Ventricular Recovery

Ventricular assist devices (VADs) are increasingly used for supporting blood circulation in heart failure patients. To protect or even to restore the myocardial function, a defined loading of the ventricle for training would be important. Therefore, a VAD control strategy was developed that provides an explicitly definable loading condition for the failing ventricle. A mathematical model of the cardiovascular system with an axial flow VAD was used to test the control strategy in the presence of a failing left ventricle, slight physical activity, and a recovering scenario. Furthermore, the proposed control strategy was compared to a conventional constant speed mode during hemodynamic changes (reduced venous return and arterial vasoconstriction). The physiological benefit of the control strategy was manifested by a large increase in the ventricular Frank-Starling reserve and by restoration of normal hemodynamics (5.1 L/min cardiac output at a left atrial pressure of 10 mmHg vs. 4.2 L/min at 21 mmHg in the unassisted case). The control strategy automatically reduced the pump speed in response to reduced venous return and kept the pump flow independent of the vasoconstriction condition. Most importantly, the ventricular load was kept stable within 1%, compared to a change of 75% for the constant speed. As a key feature, the proposed control strategy provides a defined and adjustable load to the failing ventricle by an automatic regulation of the VAD speed and allows a controlled training of the myocardium. This, in turn, may represent a potential additional tool to increase the number of patients showing recovery.

Continuous assessment of cardiac function during rotary blood pump support: A contractility index derived from pump flow

BACKGROUND The clinical application of rotary blood pumps (RBPs) for bridge-to-recovery and destination therapy has focused interest on the remaining contractile function of the heart and its course. This study reports a method to determine contractility that uses readily measured variables of the RBP. METHOD The proposed index (I(Q)) is defined as the slope of a linear regression between the maximum derivative of the pump flow and its peak-to-peak value. I(Q) was compared with the maximal derivative of ventricular pressure (dP/dt(max)) vs end-diastolic volume (EDV) and the pre-load-recruitable stroke work. All indices were evaluated using computer simulations and animal experiments. For in vivo studies, a MicroMed-DeBakey ventricular assist device (VAD) was implanted in 7 healthy sheep. Ventricular contractility was examined under normal conditions and after pharmacologic intervention. For the computer simulation, variations of ventricular contractility, ventricular pre-load and after-load, and pump speeds were studied. RESULTS In vivo and computer simulations showed the I(Q) index to be sensitive to changes of cardiac contractility, similar to other classic indices. For reduced cardiac contractility, it decreased to 9.3 +/- 3.9 (s(-1)) vs 15.3 +/- 4.0 (s(-1)) in the control condition (in vivo experiments). The I(Q) index was only marginally influenced by pre-load and after-load changes: a variation of 7.0% +/- 8.9% and 1.3% +/- 7.1%, respectively, was observed in computer simulations. CONCLUSIONS The I(Q) index, which can be derived from pump data only, is a useful parameter for continuous monitoring of the cardiac contractility in patients with RBP support.

Evaluation of Left Ventricular Relaxation in Rotary Blood Pump Recipients Using the Pump Flow Waveform: A Simulation Study

In heart failure, diastolic dysfunction is responsible for about 50% of the cases, with higher prevalence in women and elderly persons and contributing similarly to mortality as systolic dysfunction. Whereas the cardiac systolic diagnostics in ventricular assist device patients from pump parameters have been investigated by several groups, the diastolic behavior has been barely discussed. This study focuses on the determination of ventricular relaxation during early diastole in rotary blood pump (RBP) recipients. In conventional cardiology, relaxation is usually evaluated by the minimum rate and the time constant of left ventricular pressure decrease, dP/dt(min) and τ(P) . Two new analogous indices derived from the pump flow waveform were investigated in this study: the minimum rate and the time constant of pump flow decrease, dQ/dt(min) and τ(Q) . The correspondence between the indices was investigated in a numerical simulation of the assisted circulation for different ventricular relaxation states (τ(P) ranging from 24 to 68 ms) and two RBP models characterized by linear and nonlinear pressure-flow characteristics. dQ/dt(min) and τ(Q) always correlated with the dP/dt(min) and τ(P) , respectively (r>0.97). These relationships were influenced by the nonlinear pump characteristics during partial support and by the pump speed during full support. To minimize these influences, simulation results suggest the evaluation of dQ/dt(min) and τ(Q) at a pump speed that corresponds to the borderline between partial and full support. In conclusion, at least in simulation, relaxation can be derived from pump data. This noninvasively accessible information could contribute to a continuous estimation of the remaining cardiac function and its eventual recovery.

Estimation of cardiac contractility during rotary blood pump support using an index derived from left ventricular pressure

Introduction In the clinical use of cardiac assist devices, the diagnostics of the remaining heart contractility is essential for the evaluation of therapeutical measures. In this study a contractility index based on the left ventricular pressure (LVP) was evaluated during rotary blood pump support, by comparison with two other indexes.

Effects of body mass on OGTT-derived insulin sensitivity indexes in healthy subjects

Several indexes have been proposed to quantify insulin sensitivity from fasting plasma glucose and plasma insulin levels as well as from the data obtained by the oral glucose tolerance test (OGTT). Obesity represents the major risk factor associated with development of insulin resistance and Type 2 diabetes mellitus. The goal of this paper is to study the effect of body mass index (BMI) on the insulin sensitivity indexes and secretion in normal glucose tolerance subjects. The experimental results show that he BMI is significantly and inversely correlated with insulin sensitivity indexes.

ECG system with heart rate variability application

An electrocardiogram (ECG) is a standards test for cardiac testing. The ECG in commercial system is too expensive and most of them using thermal printing. On this research, we developed the ECG system that display and record in digital form. The interface of this system designs on personal computer. The ECG circuit box is connected to computer by USB port. The ECG program is graphic user interface (GUI) that can changes sampling rate, detects heart rate and finds heart rate variability. This system can transferable via local area networks (LANs) or the internet to another remote site in the telemedicine application.

Effect of Left-Right Heart During Biventricular Assist Device Support by Speed Synchronization: A Computer Study

Biventricular assist device (BiVAD) is a treatment for the end-stage heart failure patients. Normally, after left ventricular assist device (LVAD) implanted in the end-stage heart failure patients, a right heart failure immediately appeared. Then, the right ventricular assist device (LVAD) was implanted. Both LVAD and RVAD implanted so call BiVAD. Additionally, the speed synchronization is a novel concept for remaining the high preload and increasing the cardiac output. It is a potential to promote a bridge to recovery treatment. The cardiovascular, RVAD, LVAD and speed synchronization models (co-pulse mode) are implemented using MATLAB. The normal heart and pathology heart are used in this study. The pathology level of the heart was regulated by a level of maximum elastance (Emax: 30% of normal heart value) in the heart model. The constant speed mode and co-pulse mode (increasing pump speed in systolic period between 8,000–11,000 rpm) are simulated using the MicroMed-DeBakey VAD model. The hemodynamics, ejection fraction, pressure-volume loop and pressure volume area (PVA) of different heart condition and pump mode are simulated. The results indicated the aortic pressure, pulmonary artery pressure and ejection fraction in co-pulse mode are similar to the constant speed mode. However, PVA in co-pulse mode are higher than the constant speed mode on pathology heart. In conclusion, this computer simulation can re-generated the effect of BiVAD under the pathological condition. The optimal ratio of RVAD support is important to prevent the suction event. Speed synchronization can maintain the high PVA than constant speed. Therefore, partial support with co-pulse mode can potentially use for the bridge to recovery treatment.

A modular vital sign monitoring based-on USB communication

Vital sign monitoring system mainly monitors the physiological parameters of the patient. The commercial product is usually designed as all-in-one device. However, the increasing of new medical sensors causes the researchers need to develop monitoring platform for their own sensor. The purpose of this study is to redesign the state of the art vital sign monitor for various type of sensor device based on de facto Universal Serial Bus (USB) communication.

Effect of tubing length pump on flow derived index during rotary blood pump support

The variable of connecting tube length (CTL) in rotary blood pumps (RBPs) is normally existed for the external circulatory support and thus eventually incurs the different outcome as compared to the internal circulatory support. This study aims to determine the effect of the various CTL on the measured parameters from RBP. To serve this purpose, a derived indexes from RBP under mock circulatory loop (MCL) were examined. IQ which is a slope of the linear regression between the maximal time derivative of pump flow, dQ/dtmax, and its peak to peak, QP2P, was determined to evaluate the effect of 3 different CTLs; 130, 50 and 10 cm (length of inlet tube), and 130, 50 and 50 cm (length of outlet tube). Moreover, the parameters dH/dtmax, which are the maximal time derivative of pressure head (H); AOP-LVP, and its peak to peak were derived. The slope of a linear regression between dQ/dtmax and dH/dtmax decreased during reduce CTL in contrast to IQ index. Thus, this study proved that IQ index was not significant influenced by a hydraulic resistance (including CTL) and therefore can be used to monitor the cardiac function in case of both external and internal RBP support.

Cognitive function monitoring platform based on a smartphone for alternative screening tool

Neurological assessment is a commonly mental screening evaluation for initial neurological disorders in patients. Mild Mental Status Examination is a standard screening test which is used as one of the tools for diagnosis. In Thailand, Thai Mental Status Examination was used to screen the Thai-patients.