Correlations between lung-transfer factor, ventilation, and cardiac output during exercise.

In nine healthy and young subject of either sex, undergoing three or four rounds of muscular exercise of increasing severity on a bicycle ergometer, the authors investigated the behavior of the lung transfer factor (Dlco), pulmonary ventilation (V), alveolar ventilation (Va), and cardiac output (Q). In all instances they found a positive linear correlation between DLCO and oxygen consumption (VO2), at least up to 70% of maximum oxygen consumption (Vo2max) (r=0.935;p less than 0.001). Dlco was found to increase linearly as a function of increasing V (R=0.898;P LESS THAN 0.001) AND EVEN MORE SO OF INCREASING Va (r=0.919; p less than 0.001). Also the relationship between Dlco and Q appeared linear in all subjects (r=0.926; p less than 0.001). On the other hand, individual Dlco values showed considerable scatter at equal Vo2, V, Va, and Q values. Among the factors responsible for the increase of Dlco during muscular exercise, in addition to increased ventilation and cardiac output, the authors suggest the possible role of the greater desaturation of mixed venous blood and variations of hemoglobin affinity for CO.