Assessment of heart and lung morphology in a single case during cardiopulmonary resuscitation: A virtual simulation

Abstract

Background: Basic science research in cardiopulmonary resuscitation (CPR) is limited by challenges in obtaining haemodynamic data from models that simulate physiological processes. In this study, we assessed the morphology of the heart and lungs and calculated the ejection fractions of cardiac chambers during CPR using a virtual simulation.

Methods: A finite element model of a complete thorax, including internal organs, thoracic rib cage, spine, musculature, and a generic material representing soft tissues, was constructed from magentic resonance images of a man. Twelve chest compression simulations were performed with forces ranging from F = 50 to 600 N. During compression, lung and heart volumes were assessed, and the ejection fraction of each cardiac chamber was calculated.

Results: In our numerical simulations a compression depth of 5.06 cm was reached with a force of 450 N. At this depth, the right and left ventricular ejection fractions were 34.0% and 14.4%, respectively, while the right and left atrial ejection fractions were 22.1% and 24.2%, respectively. The cross-sectional area of the outflow tract decreased by 27.5% and 15.6% in the right and left ventricles, respectively. Lung volumes decreased by 193 cm³ and 169 cm³ in the right and left lungs, respectively, representing 11.2% of the total lung volume.

Conclusion: The right ventricle exhibited the highest ejection fraction among the cardiac chambers, and the left atrium showed a higher ejection fraction than the left ventricle during CPR.

Keywords: Cardiopulmonary resuscitation; Finite element model; Haemodynamics.

Fig. 1

(a) Compression depth achieved as a function of the applied force. (b–d) Side view from the right of the rib cage and external heart structure, with (b) the uncompressed reference state and the computed geometries for compression forces of (c) F = 300 N and (d) F = 500 N. In (c, d), the heart surface is coloured to indicate displacement levels (ΔY) along the normal direction (aligned with the y-axis in the model setup).

Fig. 2

Simulated compression of the heart. (a) Front view of the external heart surface, coloured to indicate levels of normal backward displacement (ΔY). (b–d) Deformation of the myocardium and compression of the heart chambers plotted on the axial slice marked in (a), with compression levels of (b) F = 0 (reference, uncompressed state), (c) F = 300 N, and (d) F = 500 N. In (c, d), colours indicate normal backward displacement levels as shown in the colour scale in (a).

Fig. 3

Computed ejection fraction of the heart chambers during chest compression. (a) Left and right ventricles. (b) Left and right atria.

Fig. 4

(a) Variation of the cross-sectional area of the right and left ventricular outflow tract with chest compression depth. (b, c) Right and left ventricles in the uncompressed geometry, showing the slice used to measure the cross-sectional area. (d) Cross-sectional area of the right ventricular outflow tract in the uncompressed geometry. (e–h) Cross-sectional area of the right ventricular outflow tract deformed under compression forces of (e) F = 150 N, (f) F = 300 N, (g) F = 450 N, and (h) F = 600 N.

Fig. 5

(a) Lung volume variation with chest compression depth. (b) Slightly slanted front view of lungs and heart under a chest compression force of F = 450 N, with surfaces coloured to show backward displacement levels (ΔY) as indicated in the colour scale. (c) Lungs and heart in the axial slice marked in (b), with the cross-section of the sternum also shown for reference.