The effect of abnormal levels of hematocrit on the single breath diffusing capacity

In order to study the effect of different levels of hematocrit on the single breath diffusing capacity (DLCO), we studied 90 lifelong nonsmokers with either iron deficiency anemia, polycythemia vera or normal hematocrits, age range 9 to 81 years, with expiratory normal flow rates and lung volumes. The DLCO ranged from 10.6 to 41.3 ml/min/mmHg and hematocrit ranged from 28%–64%. We noted a significant relationship between the DLCO and age, height, and hematocrit. We recommend that DLCO measured in the conventional manner be corrected for anemia and polycythemia by incrementing or decrementing the measured value, if expressed as a percent of predicted, by 1.35% for each percent of measured hematocrit below or above the normal values of 44%.