Carbon Dioxide Tension and Ventilatory Mechanics in Chronic Obstructive Lung Disease

PATIENTS WITH irreversible airways ob-struction 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 ven-tilatory 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 ob-servations of Gilbert, Keighley, and Auchin-closs (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 studies suggest that this is related to a relatively rapid, shallow breathing pattern in patients with carbon dioxide retention. This type of breathing necessitates a higher fractional dead space ventilation.