The Relationship Between Pulmonary System Impedance and Right Ventricular Function in Normal Sheep

Kuo, Alexander S.; Sato, Hitoshi; Reoma, Junewai L.; Cook, Keith E.

doi:10.1007/s10558-009-9083-2

Cited by 10 publications

(16 citation statements)

References 38 publications

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“…Kuo et al . 6 confirmed that Z 0 is the key determinant of RV output in their study examining the effect of pulmonary system impedance on CO. For every 1 mmHg/(L/min) increase in Z 0 , there is an approximate 3.65% decrease in CO. Likewise, for every 1 mmHg/(L/min) increase in Z 1 , there is a 0.08 Z 0 % decrease in CO.…”

Section: Introductionmentioning

confidence: 63%

“…1,11 The most physiologically relevant impedances in this setting are those at the zeroth and first harmonic frequencies. 5,6 These represent, respectively, the opposition to blood flow that is steady and periodic at a frequency equal to the heart rate. Moreover, cardiac output (CO) during TAL attachment is affected mostly by the magnitude of the zeroth and first harmonic impedance moduli ( Z 0 and Z 1 ).…”

Section: Introductionmentioning

confidence: 99%

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Thoracic Artificial Lung Impedance Studies Using Computational Fluid Dynamics and In Vitro Models

et al. 2011

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Current thoracic artificial lungs (TALs) possess blood flow impedances greater than the natural lungs, resulting in abnormal pulmonary hemodynamics when implanted. This study sought to reduce TAL impedance using computational fluid dynamics (CFD). CFD was performed on TAL models with inlet and outlet expansion and contraction angles, θ, of 15°, 45°, and 90°. Pulsatile blood flow was simulated for flow rates of 2–6 L/min, heart rates of 80 and 100 beats/min, and inlet pulsatilities of 3.75 and 2. Pressure and flow data were used to calculate the zeroth and first harmonic impedance moduli, Z0 and Z1, respectively. The 45° and 90° models were also tested in vitro under similar conditions. CFD results indicate Z0 increases as stroke volume and θ increase. At 4 L/min, 100 beats/min, and a pulsatility of 3.75, Z0 was 0.47, 0.61, and 0.79 mmHg/(L/min) for the 15°, 45°, and 90° devices, respectively. Velocity band and vector plots also indicate better flow patterns in the 45° device. At the same conditions, in vitro Z0 were 0.69 ± 0.13 and 0.79 ± 0.10 mmHg/(L/min), respectively, for the 45° and 90° models. These Z0 are 65% smaller than previous TAL designs. In vitro, Z1 increased with flow rate but was small and unlikely to significantly affect hemodynamics. The optimal design for flow patterns and low impedance was the 45° model.

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Section: Introductionmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Thoracic Artificial Lung Impedance Studies Using Computational Fluid Dynamics and In Vitro Models

et al. 2011

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“…This may not be uniform with increasing body size, and the short axis function may be more prominent in smaller individuals (14). The influence of afterload on SЈ was evident and in keeping with others (15)(16)(17).…”

Section: Discussionmentioning

confidence: 62%

Longitudinal Myocardial Contribution to Peak Systolic Flow and Stroke Volume in the Neonatal Heart

et al. 2011

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Systolic longitudinal myocardial function is important for cardiac ejection. Data describing hemodynamic determinants and the time course of myocardial longitudinal contraction as measured by tissue Doppler are lacking. Ten newborn pigs were used for invasive hemodynamic investigation. Tissue Doppler assessment of the lateral part of the mitral valve annulus during systole was performed during pharmacological modulation of inotropy, cardiac pacing, and modulations of loading conditions. The strongest association was found between peak systolic velocity (SЈ) and peak systolic flow (PSF) and end-systolic pressure (ESP), respectively (␤ ϭ 0.09 cm/mL, p Ͻ 0.001 and ␤ ϭ Ϫ0.07 cm/mL, p ϭ 0.003). Displacement (D) was mostly influenced by stroke volume (SV) (␤ ϭ 0.05 cm/mL, p Ͻ 0.001). Ejection time, SV, ESP, maximum first derivative of pressure (dP/dt max ), and PSF were all associated with SЈ and D under different states of hemodynamic modulation; however, the ratio between PSF and SЈ, SV, and D were stable during hemodynamic modulations. Normalized cross correlations indicate that SЈ and D follow the same trajectory as flow and SV, respectively. In conclusion, this study provides validity of accounting systolic D in the long axis as the longitudinal contribution to SV and peak systolic tissue velocity as the longitudinal contribution to PSF. S ystolic excursion and motion of the mitral valve annulus has been evaluated for myocardial function in both children and adults (1,2). It is easily obtainable in most patients and has the potential of being a routine parameter for assessment of myocardial function (3). Most available data are generated on the basis of studies in adults or experimental data from mature animal studies. In children, data are being published, but validated data explaining changes that occur within and between individuals at all age groups are lacking (4).This study was designed to possibly understand the nature of longitudinal peak systolic velocity (SЈ) and systolic displacement (D) when acting under the influence of hemodynamic changes in small individuals. Neonatal pigs were chosen because of the similarity to human neonates with regards to heart size and heart rate (HR). METHODSPopulation. Ten pigs (age 3-6 d, weight 2520 -6080 g) were studied under general anesthesia. A total of 185 echocardiographic assessments were performed. Twenty (11%) assessments were excluded mainly due to no capture during right atrial pacing, missing data file, or atrial contraction before mitral valve opening during pacing. All animals were in good health without overt clinical signs of disease. The experimental protocol was approved by the Norwegian Animal Research Authority. The animals were cared for and handled in accordance with the European Guidelines for Use of Experimental Animals.Experimental model. The piglets were anesthetized with sevoflurane for i.v. cannulation and maintained on midazolam, fentanyl, and penthobarbital. The animals were mechanically normoventilated (fraction of inhaled oxygen [...

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“…This index is a preferred index of afterload by physiologists due to its independence from cardiac function [4] and because it includes blood flow resistance due to left atrial pressure. Thus, it is less commonly referred to as the “total peripheral resistance.” Previous studies by our group have indicated that this is an excellent index for predicting right ventricular function under high afterload states [5,6]. …”

Section: Methodsmentioning

confidence: 99%

“…Kim et al [5] and Kuo et al [6] studied this relationship previously for sheep at resting CO. They both found that sheep with larger baseline CO had larger changes in CO for a given increase in Z 0 .…”

Section: Commentmentioning

confidence: 99%

In-Parallel Artificial Lung Attachment at High Flows in Normal and Pulmonary Hypertension Models

Akay

Reoma

Camboni

et al. 2010

The Annals of Thoracic Surgery

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Background End stage lung disease patients who require a thoracic artificial lung (TAL) must be extubated and rehabilitated prior to lung transplantation. The purpose of this study is to evaluate hemodynamics and TAL function under simulated rest and exercise conditions in normal and pulmonary hypertension sheep models. Methods The TAL, the MC3 Biolung®, was attached between the pulmonary artery and left atrium in nine normal sheep and eight sheep with chronic pulmonary hypertension. An adjustable band was placed around the distal pulmonary artery to control the percentage of cardiac output (CO) diverted to the TAL. Pulmonary system hemodynamics and TAL function were assessed at baseline (no flow to the TAL) and with approximately 60, 75, and 90% of CO diverted to the TAL. Zero, 2, and 5 mcg/kg/min of intravenous dobutamine were used to simulate rest and exercise conditions. Results At 0 and 2 mcg/kg/min, CO did not change significantly with flow diversion to the TAL for both models. At 5 mcg/kg/min, CO decreased with increasing TAL flow up to 28±5% in normal sheep and 23±5% in pulmonary hypertension sheep at 90% flow diversion to the artificial lung. In normal sheep, the pulmonary system zeroth harmonic impedance modulus, Z0, increased with increasing flow diversion. In hypertensive sheep, Z0 decreased at 60% and 75% flow diversion and returned to baseline levels at 90%. TAL outlet blood oxygen saturation was ≥ 95% under all conditions. Conclusions Pulmonary artery to Left atrium TAL use will not decrease CO during rest or mild exercise but may not allow more vigorous exercise.

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The Relationship Between Pulmonary System Impedance and Right Ventricular Function in Normal Sheep

Cited by 10 publications

References 38 publications

Thoracic Artificial Lung Impedance Studies Using Computational Fluid Dynamics and In Vitro Models

Thoracic Artificial Lung Impedance Studies Using Computational Fluid Dynamics and In Vitro Models

Longitudinal Myocardial Contribution to Peak Systolic Flow and Stroke Volume in the Neonatal Heart

In-Parallel Artificial Lung Attachment at High Flows in Normal and Pulmonary Hypertension Models

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