Can you explain what nac is? also, who is nac helpful for in terms of copd patients? http://www.advance health.com/nacetylcysteine.html

Mucolytic, not very: Nac is also called n-acetylcysteine. It can be used to help break up thick secretions particularly in patients on mechanical ventilation or who are undergoing bronchoscopy. It can be simply squirted through a breathing tube or nebulized. It tends to irritate the airway when used a great deal. It is available in an form that can be ingested, and has some medical roles, but not much involving copd.

Antioxidant: N-acetylcysteine is a precursor for the body's antioxidant glutathione. Studies have been done using it in both COPD and pulmonary fibrosis. I must stress however that these studies are typically small and usually included less than 100 patients. Many of them were not randomized and didn't include a placebo arm. That said the drug is very safe and can be obtained in the US without a prescrip.