Lung transfer factor and KCO at cardiac frequency 100 beats/min as a guide to impaired function of lung parenchyma.

Transfer factor (TL) and KCO have been measured by the single breath carbon monoxide method in 39 patients with confirmed or suspected lung disease, mostly of occupational origin, and 37 healthy subjects. TL and KCO at an exercise cardiac frequency of 100 beats/min (TL100 and KCO100) and the slopes of the regression of exercise transfer factor and KCO on exercise cardiac frequency (delta TL/delta fC and delta KCO/delta fC) were obtained. The discriminatory performance of these indices in detecting defective gas transfer was compared with that of TL and KCO at rest (TLrest and KCOrest). The slope indices did not distinguish between healthy subjects and patients with emphysema or conditions of the lung parenchyma, including asbestosis. The slope indices also failed to distinguish between individuals with normal and abnormal gas transfer at rest. The indices TL100 and KCO100 contributed additional information not contained in the indices at rest and they merit further study.