Figure 4.

As seen in Fig. 3, a fixed correction factor applied to the assumption of N₂ concentration of “trapped air” spaces still did not improve the correlation coefficient or remove large outliers, when comparing volume of trapped gas with trapped air%. Therefore, we used a molarity calculator to model the N₂% for an individual patient that was likely present in the “trapped air” spaces which would generate a perfect agreement with trapped air % from spirometry-controlled computed tomography. Each dot is color coded for the N₂% modeled to generate that perfect agreement. Note the patients in red had a larger volume of trapped gas (VTG) over residual volume % (RV%) than trapped air %, therefore N₂ concentration could not be calculated. The range for N₂% for the 5 inspiratory capacity breaths (5IC) method was 3.5% to 34.8% and for the 5 vital capacity (5VC) was 8.6% to 55.3%. Without having the accompanying trapped air% values calculating an accurate VTG/RV% is not possible.