The new test measures particles that are shed by tiny blood vessels known as capillaries that surround air sacs (alveoli) in lungs. These particles are debris shed by ongoing injury to the air sacs -- damage that eventually results in devastation of the sacs and the "Swiss cheese" appearance of the lungs.

The alveoli are where critical gas exchanges occur: blood in the capillaries brings carbon dioxide from the rest of the body for release into the air sacs, and the oxygen in the sacs (taken in from breathing) is taken up by the blood and transported to the rest of the body...