Arterial carbon dioxide tension and dyspnea in chronic bronchitis and pulmonary emphysema.

The severity of dyspnea (MRC scale) was confronted to the blood carbon dioxide tension (PaCO2) in 45 patients with chronic nonspecific lung disease having moderate or severe airway obstruction (FEV1.0 of less than 1.5 liters). The patients were classified as "bronchitic", "emphysematous" and "intermediate" using a 10- criterion (clinical, roentgenologic and biological) "emphysema score". No correlation between dyspnea grade and PaCO2 was found in "bronchitic" and "intermediate" patients; in the "emphysematous" subgroup PaCO2 tended to rise as dyspnea was more severe, but the linear correlation coefficient (r= +0.37) did not reach the significance threshold, which is high (0.468) for such a limited number of observations.