Simultaneous Measurement of Pulmonary Diffusing Capacity for CO and Cardiac Output by a Rebreathing Method in Patients with Pulmonary Diseases

Abstract

Pulmonary diffusing capacity for CO (DL_CO) and cardiac output (Q) were simultaneously measured by a noninvasive rebreathing method (RB) in 15 normal subjects and in 60 patients, including cardiac diseases (CD), bronchial asthma (BA), chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (PF). DL_CO and Q were tested by the single breath method (SB) and the dye-dilution method (Dye), respectively. DL_CO(RB) correlated well with DL_CO (SB) (r=0.890, p<0.001). Q(RB) also correlated well with Q(Dye) (r=0.909, p<0.001). Factors affecting DL_CO (RB) were age, height, body surface area, O₂ consumption, Q, hematocrit (Hct) and Q&built;Hct, among which Q&built;Hct was the prominent influential determinant. DL_CO per lung volume was smaller in COPD and PF than in BA or healthy subjects, while, the ratio of DL_CO/(Q&built;Hct) was significantly higher in COPD than in PF. Simultaneous measurements of DL_CO and Q offer comprehensive characterization for functional changes in lung parenchyma.
(Internal Medicine 34: 330-338, 1995)