The Donders Model of the Circulation in Normo- and Pathophysiology

Abstract

The solution of some recent as well as of long standing problems, unanswerable due to experimental inaccessibility or moral objections are addressed. In this report, a model of the closed human cardiovascular loop is developed. This model, using one set of 88 equations, allows variations from normal resting conditions to exercise, as well as to the ultimate condition of a circulation following cardiac arrest. The principal purpose of the model is to evaluate the continuum of physiological conditions to cardiopulmonary resuscitation (CPR) effects within the circulation.Within the model, Harvey's view of the circulation has been broadened to include impedance-defined flow as a unifying concept, and as a mechanism in CPR. The model shows that depth of respiration, sympathetic stimulation of cardiac contractile properties and baroreceptor activity can exert powerful influences on the increase in cardiac output, while heart and respiratory rate increases tend to exert an inhibiting influence, with the pressure and flow curves compatible with accepted references. Impedance-defined flow encompasses both positive and negative effects.The model also demonstrates the limitations to cardiopulmonary resuscitation caused by external force applied to intrathoracic structures, with effective cardiac output being limited by collapse and sloshing. Stroke volumes from 6 to 51 ml are demonstrated. It shows that the clinical inclination to apply high pressures to intrathoracic structures may not be rewarded with improved net flow.

Developing a kinematic understanding of chest compressions: the impact of depth and release time on blood flow during cardiopulmonary resuscitation

“…These findings fall outside of the predictions of the cardiac pump model [ 1 ], the thoracic pump model [ 2 – 4 ], or any of the numerical models that have been published to date [ 21 – 23 ]. One possible explanation for the difference between the prediction of the models and our experimental results is that the anatomical complexity of the non-thoracic vasculature is not included in the numerical models.…”

Dynamical behavior analysis of the heart system by the bifurcation structures

“…This rhythm imposed by the sinus node is regulated by various factors: the nervous system, hormones and substances circulating in the blood. However, a large number of disturbances can occur, which can affect the sinus node, the AV node, the atria and the ventricles, resulting in the loss of synchronization of the cardiac structures [ [17] , [18] , [19] , [20] ]. Cardiac rhythm is characterised by variations in the electrical potential of cells, some of which promote contraction and others automation and impulse conduction [ 7 , 21 ].…”

Efficacy of virtual reality techniques in cardiopulmonary resuscitation training: protocol for a meta-analysis of randomised controlled trials and trial sequential analysis

“…Cardiopulmonary resuscitation (CPR) is the most urgent and critical procedure in the rescue of patients with cardiac arrest 3. CPR can save lives by artificial ventilation and chest compressions, which preserve circulation to the brain when the cardiac arrest occurred 4–6. Early CPR could improve survival in both out-of-hospital and in-hospital cardiac arrests 7 8…”