Lung elastic recoil and airway resistnce as factors limiting forced expiratory flow.

Abstract

Spirometric estimates of forced expiratory air flow were related to measurements of airway resistance and lung elastic recoil in 200 patients with chronic lung disease. Several patients with severe loss of lung recoil had no appreciable limitation of forced expiratory flow. In the other patients, the severity of flow limitation was not related to lung recoil but was related to small increments of airway resistance within the normal range. Almost all patients with increased airway resistance had limitation of forced expiratory flow that was most severe when associated with loss of lung recoil. Forced expiratory flow was decreased in some patients with neither mechanical abnormality. It was concluded that loss of lung recoil had little or no direct effect on forced expiratory flow but possibly had an indirect effect through a decreased tolerance to small increments of airway resistance. Other mechanisms also may be important, e.g., increased compliance of airways.