Does caffine improve lung function ?

Possibly: Caffeine can alter breathing and lung function. One article is: http://well.Blogs.Nytimes.Com/2010/11/29/asthma-symptoms-try-caffeine/?_php=true;_type=blogs;_r=0 which summarizes the news regarding a study of caffeine and asthma. Caffeine is also used to treat or to prevent apnea in young infants.

Marginal at best: Caffeine is a xanthine, a chemical similar to aminophylline, a drug we used for years to treat the disease. It is too short acting to be very helpful. It does not appear to aggravate asthma, but I would never rely on it as a form of treatment.