Study: Treating Carbon Monoxide Poisoning by Lighting up the Lungs

Phototherapy may be an effective, noninvasive treatment for carbon monoxide (CO) poisoning.

Warren Zapol, MD, and colleagues at the Anesthesia Center for Critical Care Research at Massachusetts General Hospital, in a mouse study, showed that phototherapy increases the amount of CO exhaled after exposure, and decreases the amount of CO inhaled during exposure. Their study was published online in the American Journal of Respiratory and Critical Care Medicine on July 27, 2015.

CO poisoning is a leading cause of death by poisoning. Even if CO inhalation does not cause death, it can cause problems with memory, attention, and affect disorders. The current treatment for CO poisoning involves removing the CO quickly and restoring oxygen delivery. There is not a specific treatment for tissue damage due to CO poisoning.

CO binds to hemoglobin and becomes carboxyhemoglobin (COHb), which cannot transport oxygen, and therefore causes damage to oxygen-deprived tissues. Previous research showed that visible light causes CO to break away from COHb. The researchers investigated the hypothesis that directly illuminating the lungs of CO poisoned mice would cause the CO to dissociate from the COHb and be exhaled.

The researchers tested both direct illumination of the lungs, which required a thoracotomy, and the illumination with an optical fiber placed in the esophagus. Various wavelengths were also tested to determine which were most effective.

Illumination of the lungs combined with breathing either air or 100% oxygen “markedly reduced COHb” by 40% with air, and 55% with pure oxygen. These results led researchers to conclude that “the pulmonary circulation is an ideal location to induce COHb photodissociation” because the CO is exhaled, rather than rebinding to hemoglobin or diffusing into tissue.

There were some limitations to this study, including the fact that researchers could not test whether or not lung illumination would be beneficial after CO poisoning because for a mouse CO poisoning is an “acute lethal event.” Additionally, the trans-esophageal phototherapy was limited due to the necessity of using a laser generating limited wavelength, which does not penetrate tissue well.

Currently, patients suffering CO poisoning must be transported to specialized centers. This study suggests the possibility that “the development and application of lung phototherapy could provide a useful therapeutic strategy for field use” which could save hundreds of lives each year.