Lungs respond as if infected.

• Position: Ventilators - Brief article

When hospital patients need assistance breathing and are placed on a mechanical ventilator for days at a time. their lungs react to the pressure generated by the ventilator with an out-of-control immune response that can lead to excessive inflammation, suggests a study published in the Journal of the Federation of American Societies for Experimental Biology. While learning that lungs perceive the ventilation as an infection, researchers also discovered potential drug targets that might reduce the resulting inflammation--a tiny piece of RNA and two proteins that have roles in the immune response.

Using human cell cultures, researchers determined that mechanical pressure triggers an innate immune response--the same one that the body launches to begin its fight against any type of infection. The rhythmic pressure of ventilation stimulated the production of pro-inflammatory chemicals by activating proteins called toll-like receptors (TLRs) in lung cells.

"We showed that these cells respond to a mechanical force or pressure as if it were an inflammatory stimulus. They almost perceive it as a bacterial toxin--and they don't like it," indicates Samir Ghadiali, co-lead author of the study. "We didn't know until this...