Alternately, another drug Roflumilast, a Cyclic nucleotide phosphodiesterase (PDE) inhibitor can strongly increase Cl− efflux by CFTR, enhance CBF, and MCC in COPD and in response to cigarette smoke (Baumlin et al., 2014; Lambert et al., 2014; Tyrrell et al., 2015). Here, CFTR is linked to chronic obstructive pulmonary disease.