The pulmonary CO diffusing capacity according to Bates and according to Filley in patients with unequal ventilation

The pulmonary CO diffusing capacity (d l, co) was determined according to Filley et al., by these authors' method and according to Bates et al. in 24 patients with unequal ventilation without severe diffusion disturbances. Under the influence of the unequal ventilation, the Filley method yielded too high D values, while the values according to Bates were too low. The D values obtained by the authors' method were in between the above two extremes.In patients with unequal ventilation, the d value calculated by one of these methods affords little information as to the presence or absence of a diffusion disturbance, and no information on the extent of this diffusion disturbance. Only if D(F) is much too low is there a possibility of a disturbance in diffusion. A normal D(B) or D(K) indicates the probability of absence of a diffusion disturbance.