Chapter 16. Pulmonary Function Testing, Plethysmography, and Pulmonary Diffusing Capacity
A 55-year-old man who has smoked 10 cigarettes in the preceding 90 minutes now has a measured HbCO of 10%. If his measured DLCO on this same day is 21.4 mL·min–1·mm Hg–1, what is the best approximation of this patient's actual DLCO?
The most correct answer is b.
For every % of HbCO present, the measured DLCO is decreased by about the same amount from the actual DLCO. In this patient with HbCO = 10%, the measured DLCO is 21.4 mL·min–1·mm Hg–1. Multiplying the measured value of 21.4 by 110% will correct upward toward the actual value of 23.5 mL·min–1·mm Hg–1 that would have been found if this patient's HbCO had been 0%.