Prone restraint cardiac arrest in in-custody and arrest-related deaths

Abstract

We postulate that most atraumatic deaths during police restraint of subjects in the prone position are due to prone restraint cardiac arrest (PRCA), rather than from restraint asphyxia or a stress-induced cardiac condition, such as excited delirium. The prone position restricts ventilation and diminishes pulmonary perfusion. In the setting of a police encounter, metabolic demand will be high from anxiety, stress, excitement, physical struggle, and/or stimulant drugs, leading to metabolic acidosis and requiring significant hyperventilation. Although oxygen levels may be maintained, prolonged restraint in the prone position may result in an inability to adequately blow off CO₂ , causing blood pCO₂ levels to rise rapidly. The uncompensated metabolic acidosis (low pH) will eventually result in loss of myocyte contractility. The initial electrocardiogram rhythm will generally be either pulseless electrical activity (PEA) or asystole, indicating a noncardiac etiology, more consistent with PRCA and inconsistent with a primary role of any underlying cardiac pathology or stress-induced cardiac etiology. We point to two animal models: in one model rats unable to breathe deeply due to an external restraint die when their metabolic demand is increased, and in the other model, pressure on the chest of rats results in decreased venous return and cardiac arrest rather than death from asphyxia. We present two cases of subjects restrained in the prone position who went into cardiac arrest and had low pHs and initial PEA cardiac rhythms. Our cases demonstrate the danger of prone restraint and serve as examples of PRCA.

Keywords: George Floyd; arrest-related deaths (ARDs); autopsy; excited delirium; forensic pathology; in-custody deaths; metabolic acidosis; police-involved deaths; positional asphyxia; prone restraint; restraint asphyxia; sudden cardiac death.

FIGURE 1

This figure depicts the elimination of carbon dioxide as involving perfusion and ventilation (see Reference [68], Levitsky; Reference [56], West & Luks)

FIGURE 2

This graph demonstrates the direct ventilatory volume per minute response to the partial pressure of arterial carbon dioxide. The graph shows the dramatic increase in ventilation with increasing arterial pCO₂ and the greater need to ventilate at lower arterial pCO₂ levels during acidosis (see Reference [64], Yartsev; Reference , Levitsky, p. 219; Reference [56], West & Luks, p. 161)

FIGURE 3

This cartoon of a rat in a tube depicts the animal model of restricted ventilation (see Reference [78], Pudiak & Bozarth)

FIGURE 4

This cartoon of a rat in the coils of a boa constrictor snake depicts the animal model of decreased pulmonary perfusion (see Reference [85], Boback, et al.)