From ForceScience Newsletter #270:
Controversy sparks anew over alleged risks of prone positioning
A Canadian anesthesiologist has attempted to revive the controversy about alleged risks associated with the prone positioning of arrestees, only to draw an emphatic rebuke from a team of experts on the subject.
The physician is Alain Michaud, affiliated with a hospital in Roberval, Quebec. In published correspondence to the Journal of Forensic and Legal Medicine, he presents an argument sometimes advanced by plaintiffs' attorneys in lawsuits against police involving arrest-related deaths. Namely, that applying pressure to the back of a proned-out, struggling suspect can compress the inferior vena cava blood vessel to the extent that blood from the legs and abdomen cannot get back to the heart, thus provoking a fatal cardiac disruption. He links the problem especially to individuals experiencing the excited delirium syndrome (ExDS).
INSISTENT CHALLENGE. The anesthesiologist challenges a study published earlier in the Journal which disputed the hypothesis that "weight force" applied to "the center of [a suspect's] back" could cause a "sudden cardiovascular collapse" from significantly diminished blood return to the heart.
That study was too limited, Michaud argues, because, among other things, it did not adequately factor in the impact of physical exertion and psychological stress that invariably accompany ExDS encounters on the street.
Restraining a "hyperactive individual" in the prone position on a hard surface, he insists, "will impede free expansion of the chest and the abdomen" during inhalation and "may interfere with cardiopulmonary" function. Indeed, he says, even the weight of one knee applied to the back of a subject in the throes of ExDS "should alter the venus [blood] return significantly."
Moreover, he writes, a "tight hogtie position could also reduce the venous return directly and indirectly by different mechanisms."
Citing several papers written by others, Michaud concludes that the prone position should not be ruled out "as a contributing or precipitating factor in fatal ExDS." Police, he says, should consider "developing restraint techniques that would not impede abdominal and chest expansion...in the lateral position."
Michaud's letter can be read in full, for a fee, by clicking here
SHARP REBUTTAL. Four researchers involved in the study Michaud criticizes have fired back with a lengthy letter of their own. This team--Drs. Gary Vilke, Theodore Chan, Davut Savaser, and Tom Neuman--are physicians with the Dept. of Emergency Medicine at the University of California-San Diego.
"It is highly doubtful that Dr. Michaud's letter would ever survive peer review," they write, because he "relies on speculative theories" supported mainly by "reports of questionable applicability and no true experimental literature" and also "mischaracterizes many of his cited references,...often leaving out key details" to support his assertions.
The team points out that Michaud presents "no data" to support his claim that a single knee to the back of an excited delirium subject can significantly hamper blood flow. Although this is presented as fact, it appears in reality to be merely his "conjecture" and "speculation," they write.
"Dr. Michaud completely fails to mention five other experimental papers," in addition to their own study, "that directly contradict his thesis," the researchers continue. These studies dealt with back weight up to 225 pounds, "with no reports of any adverse effects such as blood pressure drops" or heart distress symptoms "that would be consistent with marked reductions in cardiac output....
"To be blunt, Dr. Michaud ignores common sense. Were as little as one knee in the back sufficient to cause such a dangerous reduction in cardiac output, there would be significant death rates among rugby or football players."
In contrast, the team notes, "there is now abundant evidence that even relatively minor degrees [of structural heart disease] is associated with an increased incidence of sudden death." This risk factor, they conclude, is far more worthy of focus and exploration than the "unfounded and unsupported theory" of prone positioning adversely affecting blood flow.
The rebuttal can be accessed in full, for a fee, by clicking here.
An abstract of the study at the core of the Journal's letter exchange can be viewed free of charge by clicking here. The title is "The effect of the prone maximal restraint position with and without weight force on cardiac output and other hemodynamic measures."
ANOTHER VOICE. Another observer weighing in recently on the alleged risks of prone positioning is Dr. Michael Graham, a professor of pathology at St. Louis University and chief medical examiner for the city of St. Louis. Graham includes the subject in a broad, 24-page review of factors often associated with arrest-related deaths published in Academic Forensic Pathology, the official journal of the National Assn. of Medical Examiners.
In light of existing research on the subject, Graham concludes that "in the vast majority of cases, it is unlikely" that the extent and duration of compression of an arrestee's chest, back, or abdomen during prone positioning "are sufficient to cause or contribute to death."
Sophisticated studies, he notes, have failed to confirm a risk of fatal breathing or cardiac problems induced by prone positioning with either hogtying or weight force.
In another section of his report, Graham explores research findings regarding the role of CEWs in arrest-related deaths, again concluding that no causal relationship has been established. He also describes relevant factors in deaths associated with neck restraint, excited delirium, and short-term physical exertion by suspects with the sickle cell trait.
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