Contributions of lung recoil and airway resistance to forced expiratory flow limitation.

Abstract

Fifty patients with chronic obstruction of the pulmonary airways and similar reductions in spirometric measurements of maximal forced expiratory flow (Vmax) were studied to determine the relative contribution of changes in lung recoil (Pe1) and airway resistance (Raw) to the over-all flow limitation. All 20 patients with Raw less than 2.5 cm H2O per liter per sec had a Pe1 of less than −10 cm H2O. Among patients with Raw greater than 2.5 cm H2O per liter per sec, 11 had reduction of Pe1 to less than −10 cm H2O whereas most of the remaining 19 patients had normal Pe1. Patients with the lower Raw and Pe1 had lower body weights and arterial CO2 tensions with greater dynamic compliances and tidal volumes than did those with the higher Raw. The lowest mean Vmax was found in the group of patients who had a high Raw as well as a low Pe1. Only patients with increased Raw showed an increase in Vmax after bronchodilators. These findings demonstrate that decreased Pe1 or increased Raw, or both, can severely limit...