To test the premise and to characterize the time dependence of the responses, the investigators propose the following two aims:
1. To determine the effect of a medium dose glucocorticoid/long-acting beta-agonist preparation (250 μg fluticasone plus 50 μg salmeterol) administered for 3 weeks on inhaled albuterol and sub-lingual NTG induced vasodilation in the bronchial artery, as assessed by ΔQaw in stable glucocorticoid-naïve COPD patients, and to re-assess the responses after a 3 week glucocorticoid/long-acting beta-agonist washout period.
2. To determine inhaled albuterol and sub-lingual NTG-induced vasodilation (ΔQaw) before, and 30 min and 120 min after a single medium dose of an ICS (220 μg fluticasone) in stable glucocorticoid- naïve COPD patients.
For both aims, the protocol design will be placebo-controlled and double-blind. For the second aim, only fluticasone pretreatment will be possible because the salmeterol component of the fluticasone/salmeterol combination preparation could influence albuterol responsiveness irrespective of any glucocorticoid effect. The timing of the endothelial function measurements in the long-term glucocorticoid/long-acting beta-agonist protocol and single dose ICS protocol is based on the past experience with ICS on airway vascular function. Single dose effects were seen within 15-30 min and waned by 90 min (25,26), while long-term treatment effects were no longer seen 3 weeks after ICS withdrawal (16).
