If you just look at what a pipe looks like if not cleaned properly, and picture the lungs looking the same, maybe the blood vessels too, then nicotene seems lik

If you just look at what a pipe looks like if not cleaned properly, and picture the lungs looking the same, maybe the blood vessels too, then nicotene seems like the least of the problems. However, confounding factors means that a simple additive measure cannot illuminate the problem. Short breath alone, which invariably follows the exposure to aggressive gases, leads to contraction of the vessels and increased heart rate, to keep up the oxygen level in vital parts. Even if tar should not enter the blood streem in a healthy tester, which I'm not sure, the built up tar pits so to speak are cozy breeding grounds for all kinds of pathogens. Excess water in the lungs, or vice versa dry lungs impact the imunosystem as well.