The block diagram above shows the compartments included in the model. The cardiac chambers are contained in the pericardium. The four cardiac valves are not seen in the sketch. The pericardium and the thoracic part of the circulation are contained in the intrathoracic space. Pressures, flows and volumes in each node of the circuit are recalculated every 0.25 ms by default.
Aplysia CardioVascular Lab is a real-time simulation model and software developed to fulfill the needs for basic education in physiology and pathophysiology as well as patient-specific modeling of cardiovascular disease in modern health care. User interaction is a powerful pedagogical tool and the possibility to change the parameters one by one increases understanding. Aplysia CardioVascular Lab can be used in interactive e-learning tutorials as well as in traditional seminars during education of medical students and specialized nurses, cardiologists, anesthesiologists, intensive care doctors, pediatric and adult cardiac surgeons.Aplysia CardioVascular Lab is developed for PC and Windows, but other platforms will be targeted in the future. It is a stand-alone software, but can interact with web-based tutorials and case presentations.Normal physiology, systolic and diastolic heart failure, valve stenosis and regurgitation, rhythm disorders, arteriosclerosis, atrial septal defects, ventricular septal defects, persistent ductus arteriosus and transposition of great arteries and more can be simulated in neonatal, pediatric and adult patients.Diagnostic cardiac catheterization and treatment options such as inotropic and vasoactive drugs, mechanical ventilation, intra-aortic balloon pump, left/right pulsatile or non-pulsatile ventricular mechanical assist devices, cardiopulmonary resuscitation, extra-corporeal veno-venous and veno-arterial membrane oxygenation as well as open surgical and catheter-based valve interventions can be simulated one by one or in combination.
Details in simulation model
The cardiac model is based on time-varying elastance functions containing both cardiac systolic, diastolic and timing properties. The valves open and close gradually and are characterised by both resistive and inertial propertiers.The vascular segments consist of a non-linear resistance, a non-linear elastance (exponential increase in stiffness with expansion), an inertial element and a non-linear viscoelastic resistance. All parameter values are based on actual vascular dimensions and properties (length, radius, thickness, Young’s modulus and blood viscosity).The pericardium has an exponential pressure-volume relation. Normal pressure is close to zero.Pressure in the intrathoracic space is changing depending on the breathing pattern of the patient. Normal spontaneous breathing is characterised by mean pressures close to zero with slightly negative pressures during inspiration. Mechanical ventilation is characterised by positive pressures compromising circulation.Airway mechanics including resistance and compliance of both central and peripheral airways are included in the model. Both pulmonary compliance and chest wall compliance are included permitting calculation of trans-pulmonary pressures. The lung model also includes anatomocal and alveolar dead-space affecting gas exchange of both oxygen and carbon dioxide.
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