Physiology and biomechanics of prone restraint respiration.

There is a debate over whether the effect of prone restraint on respiration can lead to cardiac arrest. In itself, the prone or prone restrained posture does not likely compromise ventilation to any clinically significant degree for a detainee who is passive and calm, as a number of prone restraint studies have shown. However, these studies were not able to replicate an anxious, distressed or intoxicated (alcohol or drugs) detainee who is struggling and being actively held down. This review examines the physiology and biomechanics of respiration, highlighting the differences between upright position respiration and prone respiration and the effect of restraint on respiration. In addition, the findings of research on the effects of struggling, obesity, anxiety or panic and drug intoxication on the consequent carbon dioxide (CO₂) production and the work of breathing are presented. The limitations which each of these factors place on the ability to remove CO₂ from the blood are discussed. The evidence suggests that severe respiratory or metabolic acidosis could arise as the result of the combined effects of several factors and that cardiac arrest, if it occurs, would be more likely due to hypercapnia than hypoxia.