Caleb Sooknanan ’20

For the past few decades, cardiopulmonary resuscitation (CPR) guidelines have been regulated on the basis of chest compression, medication procedures, and other criteria. However, the circulation generated via CPR varies with intensity and duration of compressions, which can be inconsistent. As studies evaluating such inconsistencies have been relegated to animal or computer simulations due their medical and ethical concerns, Dr. Stefan Eichhorn and researchers at Technische Universität München in Germany attempted to create a mechanical model of the thorax to better assess the efficacy procedure.

The researchers constructed a CPR simulation model using valve-controlled pneumatic pistons, an artificial heart, and thoracic stiffness data derived from human cadavers. The model has two stiffness modes and an integrated blood flow system, as well as a blood flow apparatus that reflected depth and waveform modulations similar to human conditions. CPR was then conducted at both stiffness modes, using a LUCAS™ Chest Compression System, a motor-driven plunger, and human volunteers.

As the researchers expected, the performance of volunteers differed between the two stiffness modes. Resuscitative efforts at high stiffness produced significantly less blood flow at the third minute as opposed to the first minute of operation, averaging only 87% of initial performance The maximum arterial pressure and compressive depth declined significantly relative from initial values, displaying means of 82% and 90%, respectively.

The study’s primary limitations included how modifications of the outlet tubing for the heart, namely in the form of the arterial tree, would have been needed to generate more physiologically relevant values. The proper tubing caliber would have to be addressed in future studies. Also, researchers would need to address how the model’s geometrical dimensions could be minimized for use in a CPR training manikin’s chest. The current shape of the model would not be suitable for utilization in such conditions.

Even with these limitations, the researchers were able to evaluate the impact of variable chest stiffness on blood flow generated during CPR, as well as how cycle waveform changes in mechanical resuscitation devices could be adjusted for more successful use. Further research into these simulation models may lead to improvements in resuscitation methods.

References:

1. S. Eichhorn, et al., Development and validation of an improved mechanical thorax for simulating cardiopulmonary resuscitation with adjustable chest stiffness and simulated blood flow. Medical Engineering & Physics 43, 64 – 70 (2017). doi: 10.1016/j.medengphy.2017.02.005
2. Image retrieved from: https://startcpr1st.com/cpr-classes-mandatory-schools/