Friday, November 26, 2010

Black Friday

Is the shift from a day dedicated to thanksgiving to a day devoted to voracious acquisitiveness giving you philosophic whiplash? Does the prospect of working off turkey fat by elbowing your way to the best deals on this season's consumer electronics seem rather distonic?

Join us, then, as winter heating season begins, for a brisk walk through the terrain of uncertainty surrounding patients suffering from carbon monoxide poisoning and its long-term effects. Although CO poisoning is an approved indication for hyperbaric oxygen therapy, it is a vastly underutilized treatment for that condition and one for which clinical research is sparse and contradictory.

In studies cited by the Undersea and Hyperbaric Medical Society's Hyperbaric Oxygen Therapy Indications, the 1,500+ patents treated with hyperbaric oxygen during a ten year period from 1992 to 2002 represent only a tiny portion of the 400,000 people estimated to have been seen in emergency rooms for CO poisoning during the same period. Not all incidents of carbon monoxide poisoning are acute, and not all victims seek immediate medical care, so the number of people effected could well be higher.

What accounts for the shortfall? As we previously reported, accurate diagnosis of CO poisoning is an issue. But the state of existing research and a lack of widely accepted protocols undoubtedly has a role in physician acceptance. Uncertainty over efficacy and treatment protocols weighed against potential side effects likely makes physicians reluctant to prescribe the treatment.

Even when detected by a doctor who regards HBOT as an effective treatment and appropriate for the case at hand, access to resources is an issue. Although there are well over 1,000 hyperbaric treatment centers in the United States, many are outpatient wound care facilities, independent hyperbaric clinics, or otherwise not integrated with a hospital's emergency services. For acute cases, access to hyperbaric facilities is likely to require patient transportation in many parts of the country. Traveling a considerable distance for multiple treatments adds to the challenges faced by patients suffering neurologic effects.

Much of the attention focused on carbon monoxide intoxication focuses on acute cases and short-term treatment. Standard protocols and current clinical trials involve 1 to 3 treatments and neuropsychiatric outcomes after 6 weeks. There is, however, research to support more lasting effects of COI. A 2009 review of clinical literature from 1974 through 2006 by the Department of Psychiatry at the University Hospital of Geneva found patients reporting symptoms for more than 30 years after CO poisoning and "affective disorders are observed in almost three-fourths of patients and personality disorders in more than half." The authors speculate that carbon monoxide intoxication may "constitute a risk factor in the waking of long-term neuropsychiatric disorders."

While not all victims of carbon monoxide poisoning have pre-existing risks for psychiatric disorders or suffer severe long-term effects of COI, there are still an array of potential cognitive and affective impairments. What can be done to detect these and measure the efficacy of hyperbaric oxygen therapy in improving patient outcomes? According to a 1995 study by the Center for Prehospital Care at UCLA Hospitals and Clinics, the standard CO Neuropsychological Screening Battery (CONSB) was "ineffective in detecting subtle neurological disturbances in victims of low-level CO poisoning", although the 1991 study by the Maryland Institute for Emergency Medical Services found the test battery to be "effective in evaluating cerebrally impaired CO-poisoned patients" and recommended its use for adequately assessing patients requiring aggressive hyperbaric oxygen therapy. The choice of diagnostic tools may need to be more closely calibrated to the severity and duration of carbon monoxide exposure.

None of the previous studies or current clinical trials evaluate long-term treatment of CO poisoning with HBOT, or speculate as to how neuropsychiatric improvements resulting from HBOT treatment could be measured effectively over time spans exceeding those considered in current studies. While it's possible recent advances in imaging can contribute to the body of evidence, it's likely cognitive testing will continue to be an important resource.

We'd like to suggest exploring a role for the subject-object interview as a diagnostic tool. Based on the understanding that people do not normally regress in their order of consciousness, the test could be used to detect the effects of CO poisoning if it can be shown that regression occurs in individuals effected by forms of brain injury. While the most useful context for comparison would be a relatively recent test prior to injury, severe impairment might be distinguishable relative to normative values for a relevant population group. Speculative, to be sure, but we're generally in favor of the subject-object interview being more widely conducted and understood. If it helps gain greater insight into brain injuries, so much the better.

Good luck with the shopping.

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