Aug 13, 2005

Effects of an impedance threshold valve upon hemodynamics in Standard CPR: studies in a refined computational model

C F Babbs


An impedance threshold valve (ITV) is a new airway adjunct for resuscitation that permits generation of a small vacuum in the chest during the recoil phase of chest compression. To explore in detail the expected magnitude and the hemodynamic mechanisms of circulatory augmentation by an ITV in Standard CPR. A 14-compartment mathematical model of the human cardiopulmonary system--upgraded to include applied chest compression force, elastic recoil of the chest wall, anatomic details of the heart and lungs, and the biomechanics of mediastinal compression--is exercised to explore the conditions required for circulatory augmentation by an ITV during various modes of CPR. The ITV augments systemic perfusion pressure by about 5 mmHg compared to any particular baseline perfusion pressure without the ITV. When baseline perfusion is low, owing to either diminished chest compression force, the existence of a thoracic pump mechanism of blood flow, or the presence of an effective compression threshold, then the relative improvement produced by an ITV is significant. With an ITV the heart expands into soft pericardiac tissue, which makes the heart easier to compress. An ITV can augment perfusion during CPR. The observed effectiveness of ITVs ...Continue Reading

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Mentioned in this Paper

Arterial Pulse Pressure
Entire Thoracic Aorta
Salicylhydroxamic acid
Physiologic Pulse
Electric Impedance
Circulatory System
Esophageal Tissue
Vascular Resistance
Left Ventricular Structure

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