FRIDAY, Aug. 11, 2006 (HealthDay News) -- The long-term brain health of patients in a coma or a prolonged vegetative state might be compromised by assisted-breathing protocols that deliver air significantly below normal body temperature, two researchers hypothesize.
The clinical theory was sparked by a single case study of a woman who displayed signs of recovery from nearly three years in a vegetative state after the removal of an oxygen tube that had been funneling in cold air.
"Even a small drop in brain temperature can disturb the neurochemistry of the brain, and this could be a factor in keeping or even causing a vegetative state," said study co-author David C. Reardon. "And this case showed that by restoring normal upper respiratory tract warming -- simply by removing the respirator -- brain functioning may improve."
The theory, published in the July issue of Medical Science Monitor, met the skepticism of at least one coma expert.
Kester Nedd, who heads up the division of neurological rehabilitation at the University of Miami's School of Medicine, said the study authors seemed to have gone way out on a limb with their conclusions.
"I don't think you can draw any conclusions from a single case report," he cautioned. "And there is a lot of evidence that a drop in brain temp is actually neuroprotective."
Reardon, who is director of the Elliot Institute, an anti-abortion advocacy organization in Springfield, Ill., developed the theory with George P. Ford, director of the Institute for the Minimally Conscious, in Rye, N.Y., while reviewing the case of the 53-year old woman who had been in a coma and then a prolonged vegetative state following an overdose of back pain medication.
Reardon and Ford noted that over the course of 31 months, the patient was administered oxygen through a tube inserted directly into her trachea, by means of an unheated nebulizer. At the end of that timeframe, they said, the attending physicians observed that the temperature of the air the woman had been receiving was approximately 63 degrees Fahrenheit.
Although the patient's overall body temperature appeared to be normal, the two noted, her physicians expressed concern that such readings might hide localized hypothermia, which could be taking place in the lung, heart and/or brain region as a result of the cold oxygen.
At that point -- after establishing that the patient's blood-oxygen level indicated she could breath sufficiently on her own -- the tube was disconnected.
One month later, the researchers noted that the patient began exhibiting signs of brain recovery -- displaying an intermittent verbal ability to respond to simple questions.
Reardon and Ford said they reviewed a number of other cases -- anecdotally noting evidence of similar instances of oxygen-assisted coma patients in which brain recovery appeared to occur only when the unheated air-assistance was removed.
A subsequent review of prior brain temperature research indicated that bypassing the upper respiratory tract with cold oxygen administration appears to significantly cool the blood surrounding the heart and the brain, they contended.
Reardon and Ford noted that while current medical standards for air assistance recommend that oxygen be delivered at room temperature, most treatment facilities they reviewed did not appear to adhere to such advice.
And they concluded that more research is needed.
"The case we looked at was an isolated case," Reardon admitted. "However, there are plenty of opportunities for further research and we're optimistic that a lot more can be known about this right away. And it's a fairly simple thing to adjust and take care of."
However, Nedd noted, "Right now, there are lots of clinical trials looking at this in animals and it shows that when you reduce brain temperature, it actually prevents some of the cascade of events that cause neural injury. So I would say that their theory behind this doesn't make sense at all. What they're saying is contrary to the wisdom of how we understand how neuroprotection works."
More information
For more on coma and treatment, visit the National Institute of Neurological Disorders and Stroke.
