Cardiac Energetics in Presence of Lung Assist Devices: <i>In Silico</i> Study

Abstract

The treatment with a mechanical ventilator is required whenever a patient's respiratory system becomes unable to keep the concentrations of O 2 and CO 2 in blood at tolerable levels. However, in particular cases, the thoracic artificial lung (TAL) can be regarded as a viable alternative to mechanical ventilation (MV). We aim at studying the effects of mechanical ventilators and thoracic artificial lungs devices will have on the cardiovascular system. We will give careful consideration to cardiovascular energetic parameters, such as left and right ventricular external work, pressure-volume area, and cardiac mechanical efficiency. We simulated both, mechanically ventilated patients who are not subject to the application of an artificial lung and patients who are provided with a thoracic artificial lung (TAL). In the case of a thoracic artificial lung, we involved in our simulation studies all the usual operating modes of a TAL, viz. series mode, parallel mode, and hybrid mode of the TAL with regard to the native lung. In particular, the presented simulation results will contribute to elucidate the specific characteristics of each of the aforementioned operating modes. Generally, the energetic variables are influenced by different values of input TAL resistance in both modes: parallel and in series. In this paper, we concentrated on simulation studies of the effects evoked by TAL assistance on cardiac energetic and some other important circulatory parameters. The simulation results presented show that at all modes of TAL assistance exists a strong dependency on the TAL input variables and on the value of the mean intrathoracic pressure which has been assumed for a given situation.

Simulation as a preoperative planning approach in advanced heart failure patients. A retrospective clinical analysis

“…The main feature is a modular approach with an updatable library of numerical models of different sections of the cardiovascular system, which can be assembled according to the need of the simulation. The software is particularly suitable to study the interactions with pulsatile or continuous flow ventricular assist devices [ 15 , 22 – 24 ], intra-aortic balloon pump, artificial lung, biventricular assist device and biventricular pacing [ 15 , 18 , 61 – 63 ].…”

“…The pulmonary arteriole compartment consists of a single resistance in view of their relative stiffness and the fact that inertial forces are negligible. The pulmonary capillary section is also modelled with a single resistance as previously reported [ 18 ]. Coupling between the ventricles and the circulation is obtained by using ideal valves [ 17 , 22 ].…”

Decision-making in advanced heart failure patients requiring LVAD insertion: Can preoperative simulation become the way forward? A case study

“…7, we obtain: (9) Rearranging Eq. (9), the instantaneous left (right) ventricular pressure becomes: [48] (10) Equations (10) model the ventricular interactions.…”

“…(17), we obtain: (20) Rearranging Eq. (20), the instantaneous left (right) atrial pressure becomes: [48] (21) Equations (21) enable the simulation of the interactions between the two atrial chambers. Figure 1 shows the electric analogue of the cardiovascular network used for the simulations.…”

“…The behaviour of the pulmonary capillary bed is simulated using a single resistance (Rpc). [48] The coronary circulation is modelled using one of modules of the CARDIOSIM c library. [50] The four cardiac valves are considered ideal valves [9,13] and modelled with resistances and diodes.…”