Albuterol Improves Alveolar-Capillary Membrane Conductance in Healthy Humans

BACKGROUND: Beta-2 adrenergic receptors (β(2)ARs) are located throughout the body including airway and alveolar cells. The β(2)ARs regulate lung fluid clearance through a variety of mechanisms including ion transport on alveolar cells and relaxation of the pulmonary lymphatics. We examined the effect of an inhaled β(2)-agonist (albuterol) on alveolar-capillary membrane conductance (DM) and pulmonary capillary blood volume (V(C)) in healthy humans. METHODS: We assessed the diffusing capacity of the lungs for carbon monoxide (DLCO) and nitric oxide (DLNO) at baseline, 30 minutes, and 60 minutes following nebulized albuterol (2.5 mg, diluted in 3 mL normal saline) in 45 healthy subjects. Seventeen subjects repeated these measures following nebulized normal saline (age = 27 ± 9 years, height = 165 ± 21 cm, weight = 68 ± 12 kg, BMI = 26 ± 9 kg/m(2)). Cardiac output (Q), heart rate, systemic vascular resistance (SVR), blood pressure, oxygen saturation, forced expiratory volume at one-second (FEV(1)), and forced expiratory flow at 50% of forced vital capacity (FEF(50)) were assessed at baseline, 30 minutes, and 60 minutes following the administration of albuterol or saline. RESULTS: Albuterol resulted in a decrease in SVR, and an increase in Q, FEV(1), and FEF(50) compared to saline controls. Albuterol also resulted in a decrease in V(C) at 60 minutes post albuterol. Both albuterol and normal saline resulted in no change in DLCO or DM when assessed alone, but a significant increase was observed in DM when accounting for changes in V(C). CONCLUSION: These data suggest that nebulized albuterol improves pulmonary function in healthy humans, while nebulization of both albuterol and saline results in an increase in DM/V(C).