A group of Medical School researchers has discovered a bizarre twist on the harmful effects of car exhaust and cigarette smoke: nitric oxide, a component of both pollutants, can help treat a deadly type of pneumonia.
The finding doesn't mean anyone should start sniffing exhaust fumes or light up to avoid the flu. But according to Dr. Warren M. Zapol, Jenney professor of anesthesia at Mass. General Hospital, nitric oxide can improve lung efficiency in patients suffering from Adult Respiratory Distress Syndrome (ARDS).
Pneumonia plugs up the lung's air spaces, reducing the surface area available for the lungs to exchange gas with the blood. Nitric oxide, produced naturally by organ linings as a hormone to dilate blood vessels, works by improving gas exchange efficiency in the remaining unclogged spaces.
ARDS is an often fatal form of pneumonia which claimed the life of Muppet originator Jim Henson.
Zapol reports in today's New England Journal of Medicine that after inhaling nitric oxide, eight of ten chronic ARDS patients survived. He said he has not yet observed any side effects, if low doses of the fresh gas are administered properly within seconds of its formation.
The gas is actually harmless, Zapol said. The researcher said the Environmental Protection Agency assured him that while nitrogen oxide's "daughter product," nitrogen dioxide, also present in pollutants, is poisonous, nitric oxide itself is not dangerous.
Instructor in Anaesthesia Dr. Jesse D. Roberts, Jr., a member of Zapol's research group, said the discovery also explains why mountain climbers short of breath often claim that smoking cigarettes makes them stronger. The seeming paradox may be due to the presence of nitric oxide in cigarette smoke.
When a patient breathes nitric oxide, Zapol said, the gas never leaves the lungs. Instead, it combines with oxygen-carrying hemoglobin in red blood cells and is deactivated, so that any effects are purely local.
This also means that rather than decreasing blood pressure through out the body, a danger of other conventional treatments, nitric oxide only reduces pressure in the lungs.
Scientists contacted yesterday were generally optimist about the apparent success of the nitric oxide approach.
"This looks promising," said Joseph D. Brain, Drinker professor of environmental physiology at the School of Public Health. "I think it's pretty solid stuff."
And nitric oxide may only be the tip of the iceberg. The idea behind the treatment, that pollutants that are toxic in high doses are actually essential chemicals in the human body, may open a whole new world of safe drugs for other diseases.
Carbon monoxide, another toxic gas present in automobile exhaust, has also been shown to be a chemical messenger between cells, Brain said. "It's remarkable that it's escaped everyone's notice for so long," he said.
Previous treatment for similar respiratory diseases have included mechanical ventilation and infusion of high levels of oxygen, Zapol said, but "nothing to make the lungs smarter."
Zapol said previous research has proven nitric oxide's efficacy in treating "blue babies," who cannot breathe on their own at birth, and
Stella Kourembanas, assistant professor of pediatrics at the Medical School, said a great deal of attention has been focused on nitric oxide since the discovery in 1987 of its effects on the lung's blood vessels. In 1992, Science named the compound "Molecule of the Year."
According to Zapol, it all reduces to one simple thing. "Good things hide in pollutants and cigarettes," he said