Influence of beta-2 agonist aerosols on pressure-volume characteristics of the lungs

The effects of inhalation of a beta-2 adrenergic compound (fenoterol) on the expiratory pressure-volume curve of the lung were studied in 11 normal subjects. In particular, the dose dependence and the time course of this effect were determined, and they were compared to the characteristics of the bronchodilator action. Analysis of the results showed that (1) despite a decrease in esophageal tone, lung recoil pressures at all lung volumes were decreased by these compounds, (2) this change, in contrast to bronchodilation, was observed only when high doses were inhaled, and (3) this effect appeared rapidly and elapsed after approximately 30 min, whereas bronchodilation remained stable for at least 2 hours. Additional studies with intravenous infusion of the drug indicated that the effects of beta adrenergic agonists on the pressure-volume characteristics of the lungs are related to the amount of the drug delivered to the peripheral segments of the lung. These findings suggested that large doses of beta-2 agonist aerosols can cause sufficient relaxation of the contractile elements of the lung parenchyma to produce alterations in the static elastic properties of the lungs. In contrast to bronchodilation, which results from a topical action of inhaled particles, these alterations are probably a systemic effect of these aerosols, related to the quantity of the drug absorbed into the circulation.