Effect of Low Hemoglobin Levels on the Diffusing Capacity of the Lungs for CO

The influence of the hemoglobin concentration in the peripheral venous blood on the diffusing capacity of the lungs for CO (DLCO) was tested with the single-breath method. 9 patients with histologically verified interstitial pulmonary fibrosis of varying etiology and 26 persons with healthy lungs with anemia requiring transfusions were investigated before and after compensation of the anemia. It was found that the true maximum diffusing capacity of the lungs measured in anemia patients was too low. In the test subjects with healthy lungs, there was a positive linear correlation between the hemoglobin content of the blood and DLCO. A correction factor to calculate the true DLCO in patients with healthy lungs but with anemia is specified. In the patients with interstitial pulmonary fibrosis, the influence of the reduced diffusing capacity of the alveolocapillary membrane on the extent of the diffusion disorder was in each case greater than the effects due to the anemia.