As a working definition, chronic CO poisoning involves an exposure to CO that occurs more than once and lasts longer than 24 hours. Accordingly, acute CO poisoning involves an exposure to CO that occurs only once and lasts no longer than 24 hours. Chronic CO poisoning usually involves lower levels of the gas in the air and lower blood COHb saturations; higher CO concentrations and COHb often end in death thus never becoming chronic. Exposure usually continues for many days, months, and even years. The boundary limit between acute and chronic exposure is indistinct.
This study suggests that a multitude of physical, cognitive and emotional symptoms persist for very long periods of time following chronic exposure to CO. The CO exposure need not produce altered consciousness at any time for this to occur. In fact, the CO exposure concentations and COHb saturations are usually quite low, in the range previously thought incapable of producing lasting health harm in humans.
The amount of data and the resulting conclusions regarding chronic CO poisoning in this chapter (and book) is probably more than published in any other work in the past 40 years. Clearly, prolonged exposure to this insideous poison, even at what were previously thought to be ultra-low levels, is capable of producing many and varied residual health effects. Furthermore the incidence of such unpleasant and often debilitating effects is far higher than was previously believed by the medical and public health community, and can continue for a very long period of time. It is not believed that this body of work answers all of the questions relevant to chonic CO poisoning, but rather will act to spur others to continue investigations of the problem which will provide a better understanding of what occurs and improve treatment for victims in the future.
Source: CRC Press, Boca Raton, FL., 2000.
also see CO Syndrome
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