Clinical assessment of a rebreathing method for measuring pulmonary gas transfer

A rebreathing method for measuring carbon monoxide transfer factor (TLCO) and transfer coefficient (KCO) is evaluated. The test was performed on 42 subjects. Seventeen of these had normal lung function while the remainder suffered from various conditions, most having fibrosing alveolitis. No patients with severe airways obstruction were included in the group. The results were compared with single-breath measurements and close correlations were found between single-breath KCO and rebreathing KCO (r = 0.78, p less than 0.001) and between single-breath TLCO and rebreathing TLCO (r = 0.97, p less than 0.001). The reasons for discrepancies between single-breath and rebreathing values are discussed. It is concluded that measurement of rebreathing gas transfer is a useful supplement to routine tests of lung function, particularly in breathless patients with a small vital capacity.