Aim: In this work numerical simulation is used to predict the influence of mechanical ventilation (MV) on cardiac output (CO), coronary flow (CF) and left ventricular myocardial oxygen consumption (Vo2) in different circulatory conditions. Method: We used a computer simulator of the cardiovascular system in which, lumped parameters models reproduce the circulatory phenomena in terms of pressure and volume relationships. A variable elastance model reproduces the Starling's law of the heart. The coronary bed is considered as a single branch which links the left ventricle output with the right atrium input. In the study left ventricle elastance (Ev) assumed two different values (1 - 2 mmHgocm-3). Systemic arterial resistance (Ras) was also changed during simulation (0.6 - 1.05 - 1.5 mmHgocm-3osec). Positive mean thoracic pressure (Pt), changing from -2 to +5 mmHg, introduced the influence of MV. Results: Pt has a significant influence on CO, CF and Vo2. Changes of Ras have an effect on these variables. For Ev=1 mmHgocm-3, when Ras changes from 0.6 to 1.5 mmHgocm-3osec, CF increases from 36% (Pt=+5 mmHg) to 49% (Pt=-2 mmHg) and CO decreases from 43% (Pt=-2 mmHg) to 25% (Pt=+5mmHg). These effects, in CF and Vo2, are more visible for Ev=2 mmHgocm-3 and when Pt takes high positive values (between +2 and +5 mmHg). Conclusions: Our results confirmed the known effects of Pt on CO, CF and Vo2 evidencing the importance of circulatory and ventricular parameters and suggesting their monitoring in clinical environment.
The influence of ventilatory support on coronary flow and oxygen consumption in different circulatory conditions.
De Lazzari C;Ferrari G;
2002
Abstract
Aim: In this work numerical simulation is used to predict the influence of mechanical ventilation (MV) on cardiac output (CO), coronary flow (CF) and left ventricular myocardial oxygen consumption (Vo2) in different circulatory conditions. Method: We used a computer simulator of the cardiovascular system in which, lumped parameters models reproduce the circulatory phenomena in terms of pressure and volume relationships. A variable elastance model reproduces the Starling's law of the heart. The coronary bed is considered as a single branch which links the left ventricle output with the right atrium input. In the study left ventricle elastance (Ev) assumed two different values (1 - 2 mmHgocm-3). Systemic arterial resistance (Ras) was also changed during simulation (0.6 - 1.05 - 1.5 mmHgocm-3osec). Positive mean thoracic pressure (Pt), changing from -2 to +5 mmHg, introduced the influence of MV. Results: Pt has a significant influence on CO, CF and Vo2. Changes of Ras have an effect on these variables. For Ev=1 mmHgocm-3, when Ras changes from 0.6 to 1.5 mmHgocm-3osec, CF increases from 36% (Pt=+5 mmHg) to 49% (Pt=-2 mmHg) and CO decreases from 43% (Pt=-2 mmHg) to 25% (Pt=+5mmHg). These effects, in CF and Vo2, are more visible for Ev=2 mmHgocm-3 and when Pt takes high positive values (between +2 and +5 mmHg). Conclusions: Our results confirmed the known effects of Pt on CO, CF and Vo2 evidencing the importance of circulatory and ventricular parameters and suggesting their monitoring in clinical environment.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
