Browsing by Author "Belenkie, Israel"
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Item Open Access Hemodynamic effects of positive pressure ventilation and PEEP(2002) Mitchell, Jamie R.; Belenkie, IsraelItem Open Access Mechanisms of Early Filling in the Left Ventricle(2021-01-08) Urroz Lopez, Maryell Giofred; Tyberg, John V. T.; Shrive, Nigel Graham; Belenkie, Israel; Sheldon, Robert Stanley; Fewell, James E.The mechanism by which ventricular filling occurs has been debated for centuries. Originally, it was believed that ventricular filling was an entirely passive process. However, in the 20th-century, researchers proposed that LV played a role in its own filling sucking blood into itself. At the early phase of diastole, the LV enlarges faster than it is able to fill passively by the Left Atrium (LA); therefore, aspirating blood into itself. Diastolic suction (DS) is the term applied to the phenomenon whereby the left ventricle (our study will be limited to the LV), in part, fills itself. Two approaches to study DS are the volume of filling due to suction, VDS (Katz’ approach), and the energy of the Backward Decompression Wave, BDW (Wang’s approach). Our first aim was to determine if DS exists at LV volumes that exceed the unstressed volume. Our second aim was to compare Katz’ Criterion to the energy of the BDW generated by the LV (Wang’s approach). The study was performed using a porcine model. Hemodynamics and mitral blood flow velocity were measured over a range of filling pressures during baseline, inferior vena cava occlusion (IVCO), and volume loading. Our findings suggests that the LV generates suction when ESV is greater than ESV at baseline (ESVB), which opposes the view that the LV is not capable of generating suction at increasing ESV’s. We found non-zero values of VDS and IW-DS when ESV>ESVB which suggest a non-recoil mechanism responsible for suction. In addition, our data shows that both approaches to DS, measured by VDS and IW-DS, are indeed related as they responded in the same manner to changes in EDV, ESV, and EDP.Item Open Access P1.4 Hemodynamics of Pulmonary Hypertension: Application of the Reservoir-Wave Approach(2015-11-23) Ghimire, Anukul; Andersen, Mads; Burrowes, Lindsay; Bouwmeester, J. C.; Grant, Andrew; Belenkie, Israel; Fine, Nowell; Borlaug, Barry; Tyberg, JohnAbstract Using the reservoir-wave approach, previously we characterized pulmonary vasculature mechanics with multiple interventions in a canine model. In the present study, we measured high-fidelity pulmonary arterial (PA) pressure, Doppler flow velocity, and pulmonary capillary wedge pressure in 11 patients referred for evaluation of exertional dyspnea. The analysis was performed using the reservoir-wave approach; wave intensity analysis was subsequently utilized to characterize the PA wave pattern. Our objective was to identify specific abnormalities associated with pulmonary hypertension. Seven patients with varying PA pressures had reduced pulmonary vascular conductance (i.e., the amount of flow that the lungs can accept per pressure gradient), suggesting that these patients might benefit from pulmonary vasodilator therapy, some even in the absence of markedly elevated PA pressures. Right ventricular (RV) performance was assessed by examining the work done by the wave component of systolic PA pressure. Wave work, the non-recoverable energy expended by the RV to eject blood, varied directly with mean PA pressure. Wave pressure was partitioned into two components: forward-travelling and reflected backward-travelling waves. Among patients with lower PA pressures, we found pressure-decreasing backward waves that aided the RV during ejection, as previously reported in normal experimental animals. Among patients with higher PA pressures, we detected pressure-increasing backward waves that impede RV ejection. We conclude that it is important to measure pulmonary vascular conductance to properly assess the pulmonary vasculature. The reservoir-wave approach and wave intensity analysis may prove to be valuable tools to evaluate RV performance and may facilitate development of therapeutic strategies.Item Open Access Pulmonary Hypertension: Insights From the Reservoir-Wave Approach(2016) Ghimire, Anukul; Tyberg, John; Fine, Nowell; Belenkie, Israel; Grant, AndrewWe employed the reservoir-wave approach to analyze high-fidelity pulmonary arterial (PA) pressure and Doppler flow velocity in 11 patients with varying cardiac diseases. Our specific objectives were to (1) to characterize PA wave pattern and (2) evaluate right ventricular (RV) performance. Wave pressure was partitioned into its forward and backward components. Among patients with lower PA pressures, pressure-decreasing and flow-increasing reflected waves that assist RV ejection were detected. Among the more pulmonary hypertensive patients, pressure-increasing and flow-decreasing reflected waves that impede RV ejection were detected. The four patients with the highest PA pressures showed an early systolic deceleration in flow, which was found to coincide with reflected pressure-increasing, flow-decreasing waves. Wave work done by the RV increased with PA pressure, but expressed as a fraction of total RV work, did not change. The reservoir-wave approach may prove to be a valuable tool to characterize PA-RV interaction and evaluate RV performance.Item Open Access The hemodynamic effects of high frequency oscillatory ventilation(2010) Smailys, Andrea; Belenkie, Israel