Abstract P103: Effects of Chest Compression Pressure Field on Stroke Volume during Cardiopulmonary Resuscitation

Abstract

Hypothesis: The way that chest compressions generate blood flow remains unclear. Additionally, different mechanical chest compression devices may create different thoracic pressure fields. We hypothesize that three thoracic pressure fields, direct ventricular massage, cardiac pump, and thoracic pump, generate blood flow through different mechanisms resulting in different stroke volumes. Methods: The Donder’s model of the human cardiovascular system models vessels as resistor-inductor-capacitor (RLC) circuits, where the resistive component describes the viscous resistance to blood flow, the inductive component describes the inertial resistance to blood flow changes, and the capacitive component describes the elastic properties of the vessel. The model can account for effects of respiration on blood flow. Cardiac output for the three pressure fields was modeled using sinusoidal compression waveforms with maximum pressures between 25 and 150 mmHg. Results: The figure shows the dependence of stroke volume on the pressure maximum for the three pressure fields. Peak stroke volumes occur near 75 mmHg for ventricular massage, 125 mmHg for thoracic pump, and 25 mmHg for cardiac pump compressions. Ventricular massage and the cardiac pump model utilize the heart valves to generate blood flow. The thoracic pump model generates blood flow by utilizing the elastic differences between veins and arteries. Conclusions: The three pressure fields have unique values for optimum compression pressure. The Donder’s model may allow for rapid investigation of many pressure fields, pressure wave forms, and compression to ventilation ratios to accelerate the optimization of CPR.