[Determination of pulmonary blood flow by acetylene rebreathing method in patients with chronic respiratory disease].

Non-invasive measurement of pulmonary blood flow by acetylene rebreathing was performed in patients with pulmonary diseases. Cardiac output measurement by thermodilution method was also used simultaneously. A fast computation system was coupled with the measurement. Fourteen emphysema patients and 7 pulmonary fibrosis patients were the subjects. Ten patients with normal lung function were normal controls. After the measurement of cardiac output, the subjects rebreathed mixed gas containing acetylene and argon from the end tidal level. The inspiratory and expiratory gas was measured by mass-spectrometer. A lung model made of two compartments connected in series, a compartment of the rebreathing bag and a compartment of the lung were used for the analysis, while taking account of the volume reduction due to O2 and CO2 exchange and the fluctuation of end tidal gas concentration until equilibrium between the bag and the lung was reached. Values in 9 emphysema cases and 6 fibrosis cases were within or near the 90% confidence limits of control. Five emphysema cases were obviously out of the range, and their pulmonary blood flow was less than the cardiac output and their mean arterial PCO2 was higher than that of the other emphysema cases. These cases were considered to have blood flow to the sites with low alveolar ventilation per unit volume.