One misconception about DLCO results that I’ve heard over and over is that DLCO/VA is DLCO “adjusted” for lung volume and that using it is a way of “normalizing” DLCO for lung volume. This is not true and the information that DL/VA can give you about a patient’s lung without also considering VA as well is very limited and can be misleading.
WARNING, MATH AHEAD!
The equation for calculating DLCO is: 
Most pulmonary technicians and physicians are aware that a patient’s hemoglobin and carboxyhemoglobin levels are factors that affect DLCO test results. What may be less well appreciated is the degree to which DLCO varies with the alveolar oxygen concentration.
Oxygen and carbon monoxide both compete for uptake by hemoglobin so when alveolar O2 is low or high the measured DLCO will also vary accordingly. The relationship between DLCO and PAO2 has been studied both in a regards to FIO2 and to barometric pressure. Both empirically and mathematically DLCO is estimated to change by approximately 0.35% per mmHg PAO2 change.