ABSTRACT

Riot control agents are those that cause disabling physiological effects when they come into contact with the eyes or skin, or when inhaled. They have the capacity to induce intense sensory irritation of the skin and mucous membranes of the eye and respiratory tract. Riot control agents are peripheral sensory irritants that pharmacologically interact with sensory nerve receptors in skin and mucosal surfaces at the site of contamination, resulting in local pain and discomfort sensations with associated reexes (Salem et al., 2001). The reex most associated with the inhalation exposure of irritants is the Kratschmer reex, rst reported in 1870 (Kratschmer, 1870). He described this reex response following the exposure of rabbits to chemical irritants such as chloroform and carbon dioxide. On exposure, the immediate response was apnea or cessation of respiration. This reex is one of the protective reexes or defense mechanisms programmed to prevent or reduce the amount of the noxious chemical reaching the lower respiratory tract and maintain homeostasis. This effect is accompanied by bradycardia and a biphasic fall and rise in aortic blood pressure. The Kratschmer reex is mediated by the olfactory (I), trigeminal (V), and glossopharyngeal (IX) cranial nerves and was also demonstrated to occur in humans (Allen, 1928-1929). The Kratschmer reex also occurred in rodent and canine experiments following an exposure to volatile solvents (Aviado, 1971). The cardiopulmonary receptors involved in the defense mechanisms prevent the absorption and distribution of the inhaled irritant to the vital organs, as well as facilitate the expulsion of the irritant, while the extra-cardiopulmonary mechanisms promote metabolism and excretion of the absorbed chemicals. These have been described by Aviado and Salem (1968, 1987) and by Aviado and Aviado (2002). During apnea or cessation of respiration, blood levels of carbon dioxide increase and thus drive the respiratory center to restart breathing. Individuals with compromised immune systems, or nervous system depression as a result of alcohol or illicit drug consumption, or a combination of these, may prevent the restarting of respiration, resulting in death from asphyxia. This may be, in part, responsible for the over 100 in-custody deaths attributed by law enforcement agencies to positional asphyxia following exposure to pepper sprays.