Relationships of Carbon Dioxide Retention to Ventilatory Impairment and Hypoxemia in Chronic Obstructive Lung Disease

Abstract

In 80 male patients (average age 52.5 yr) with severe obstructive ventilatory impairment (FEV1.0 [forced expiratory volume in 1 s] less than 40% of predicted) due to chronic bronchitis and/or emphysema, the blood CO2 tension [PaCO2] measured at rest, in a stable clinical status, was correlated to the spirometric variables and the O2 tension [PaO2]. PaCO2 (range 31-60 mm Hg) was loosely related to the VC [vital capacity] (r [correlation coefficient] = -0.28) and the FEV (r = -0.30, both P < 0.05) and strongly related to the PaO2 (r = 0.60; P < 0.001). When patients were classified as bronchitic or emphysematous by clinical, roentgenologic and biological criteria, the correlations were higher for bronchitics. In patients with chronic bronchitis with severe obstruction a very good estimation of PaCO2 is possible from PaO2: PaCO2 = 75.8-0.44 PaO2 (SE 0.1 mm Hg.).