Non-invasive examination of the lungs by means of exhaled particles

With each breath we take, we exhale particles that are formed in the tiny airways of the lungs. The particles are made from the fluid film lining these airways, which contains lipids as well as proteins. Such particles can be collected by means of an impactor, directing the exhaled air via small nozzles onto a surface, where size-dependent inertia causes the particles to be deposited. This method allows material from deep within the lungs to be sampled non-invasively to study diseases. The challenge is the small quantity of particles, whose weight is determined based on their number and size distribution. Usually, less than one quarter of a millionth gram is available for this purpose. Highly sensitive detection methods are thus required for further analyses. To evaluate whether this new method is suitable for use in clinical settings, volunteers inhaled bacterial endotoxin in a clinical study. This inhalation exposure causes a short-term inflammatory response in the lungs, as has been demonstrated by standard methods such as sputum analysis. In the present study, the Fraunhofer researchers for the first time successfully demonstrated the increase in inflammatory cytokines in exhaled particles as well. They have published the data and have already used the method of exhaled particle measurement in several clinical studies.