CORRELATIONS BETWEEN LUNG-TRANSFER FACTOR, VENTILATION, AND CARDIAC-OUTPUT DURING EXERCISE

In 9 healthy and young subjects of either sex, undergoing 3 or 4 rounds of muscular exercise of increasing severity on a bicycle ergometer, the behavior of the lung transfer factor (DLCO), pulmonary ventilation (.ovrhdot.V), alveolar ventilation (.ovrhdot.VA) and cardiac output (.ovrhdot.Q) were investigated. In all instances, a positive linear correlation was found between DLCO and O2 consumption (.ovrhdot.VO2), at least up to 70% of maximum O2 consumption (.ovrhdot.VO2 max) (r = 0.935; P < 0.001). DLCO increased linearly as a function of increasing .ovrhdot.V (.hivin.r = 0.898; P < 0.001) and even more so of increasing .ovrhdot.VA (.hivin.r = 0.919; P < 0.001). Also the relationship between DLCO and .ovrhdot.Q appeared linear in all subjects (.hivin.r = 0.926; P < 0.001). Individual DLCO values showed considerable scatter at equal .ovrhdot.VO2, .ovrhdot.V, .ovrhdot.VA and .ovrhdot.Q values. Among the factors responsible for the increase of DLCO during muscular exercise, in addition to increased ventilation and cardiac output, the possible role of the greater desaturation of mixed venous blood and variations of Hb affinity for CO was suggested.