The mechanism of blood flow during chest compressions for cardiac arrest is probably influenced by the patient's chest configuration

Abstract

AimMechanical assist devices are sometimes needed during resuscitation efforts of patients with prolonged cardiac arrest. Two such devices, the AutoPulse and the LUCAS, have different mechanisms of action. We propose that the effectiveness of mechanical assist devices is somewhat dependent on the configuration and compliance of the patient's chest wall.MethodsA previous study of patients with out‐of‐hospital cardiac arrest in Arizona reported that survivors were younger and many were observed to have narrow anterior–posterior chest diameters. These observations suggest that the predominant mechanism of blood flow during cardiopulmonary resuscitation of individuals with primary cardiac arrest is influenced by the patient's anterior–posterior chest diameter and compliance. It is proposed that in older individuals with an increased anterior–posterior chest diameter and decreased chest compliance that the AutoPulse, which works by increasing intrathoracic pressures, may be more effective. In contrast, the LUCAS device, which works predominately by compression of the sternum, is probably more effective in patients with narrower anterior–posterior diameters and a more compliant chest.ResultsThese hypotheses need to be confirmed by researchers who not only have access to the lateral chest roentgenograms of patients with cardiac arrest, to determine their anterior–posterior chest diameter, but also to the type of mechanical device that was used during resuscitation efforts and their patient's survival. If the observations herein proposed are confirmed, hospitals and paramedics may ideally need to have one of each type of mechanical chest compression unit and select the one to use depending on the patient's age and anterior–posterior chest diameter.ConclusionsThe mechanism of blood flow in patients with cardiac arrest is predominantly secondary to cardiac compression in younger patients with narrow anterior chest diameters and predominately secondary to the thoracic pump mechanism in older patients with emphysema.

Correlation between end-tidal carbon dioxide and the degree of compression of heart cavities measured by transthoracic echocardiography during cardiopulmonary resuscitation for out-of-hospital cardiac arrest

“…Mitral and tricuspid valves remain opened and retrograde blood flow is prevented by venous valves. This theory assumes collapse of the airways at each compression that allows an increase in intrathoracic pressure [26]. At present, it is not known which of the two is the main mechanism.…”

“…At present, it is not known which of the two is the main mechanism. Probably both may be involved, and the major factors that determine which mechanism will be dominant in the individual patient may be chest configuration, compliance of the chest wall, age, type of cardiac compression device (if used), force of the compressions and velocity of the compressions [26, 27]. These circumstances, especially the chest configuration, may be the reason for different mechanisms of generating blood flow by chest compressions in humans and experimental animals [28, 29].…”

Associations between Central Obesity and Outcomes of Adult In-hospital Cardiac Arrest: A Retrospective Cohort Study

“…Alternatively, the worse IHCA outcomes associated with central obesity may be explained in a mechanistic way. According to cardiac pump theory 38 , in order to provide high-quality chest compression, the rescuer's hands should be placed on the lower half of the sternum 39 where the maximal left ventricle diameter is assumed to be 40 . Lee et al 41 .…”

Comparison of in-hospital use of mechanical chest compression devices for out-of-hospital cardiac arrest patients

“…AUTOPULSE has a cardiac and thoracic pump mechanism. [1] A load-distributing band consists of a cover plate and 2 bands integrated with a compression pad with a Velcro fastener. Attached to a platform under the patient, the band is automatically adjusted to the patient and provides compressions to the patient's chest in the region of the heart.…”

“…[2] By contrast, LUCAS has a cardiac pump mechanism. [1] A back plate is positioned underneath the patient as a support for the external chest compressions. An upper part with a suction cup is attached to the back plate through a claw lock on each side.…”