Effect of Salmeterol on Fluid Clearance From Alveolar-Capillary Membrane in COPD Patients

The cardiovascular component associated with COPD plays a major role in prognosis of the disease, being responsible of 25% of the deaths. Experimental and initial clinical data suggest that beta-adrenergic agonists accelerate clearance of excess fluid from the alveolar airspace, with potential positive effect on cardiogenic pulmonary edema.

The aim of this study was to investigate the effects of a long-acting beta-2 agonist, salmeterol, on alveolar fluid clearance in COPD patients by evaluating the diffusive and mechanical lung properties. Our experimental model to test alveolar fluid clearance was rapid saline intravenous infusion.

Ten COPD and 10 healthy subjects treated with salmeterol or placebo 4 hours before the begin of the study were evaluated, in four non consecutive days, just before and after a saline infusion or a similar period without infusion.

Both in COPD and healthy subjects rapid saline infusion, with placebo or salmeterol premedication, lead to a significant decrease of DLCO and FEV1. Nonetheless, salmeterol pretreatment lead to a significant reduction of the impairment of gas exchange due to saline infusion (-64% of DLCO reduction in comparison with placebo), whilst it did not affect the changes in FEV1. In the control setting, with no infusion, we did not find any significant change of both DLCO and mechanical properties of the lung.

In conclusions, in COPD patients salmeterol appears to provide a protective effect against an acute alveolar fluid clereance challenge secondary to lung fluid overload providing an intriguing mechanistic explanation for the benefits observed in larger trials.