Patients with irreversible airways obstruction of uncertain etiology present a diversity of clinical, physiological, and even pathological findings, and one feature that shows great variability is the tendency to carbon dioxide retention. The present report, which is based on studies of ventilatory mechanics in 34 patients, attempts to explain this variability. The study is divided into three parts.
First, Pco2 is correlated with ventilatory characteristics. Although confirming the observations of Gilbert, Keighley, and Auchincloss (1) that hypercapnia (or alveolar hypoventilation) is more closely related to a high fraction of dead space ventilation than to a low total minute volume, present