Effect of total lung capacity, gender and height on CT airway measurements

Testing the hypothesis that CT airway measurements could be influenced by total lung capacity (TLC), gender and height in normal individuals.

In this ethics committee-approved prospective trial, 87 healthy never-smoking volunteers who provided written informed consent were included. From a helical CT scan of the chest, the wall thickness (WT) and the lumen area were twice measured in the third- and fourth-generation airways by three readers using a dedicated software. In addition, the TLC was also measured using CT (TLC_CT). The percentage of airway area occupied by the wall (WA%) and the square root of wall area at an internal perimeter of 10 mm (√WAPi10) were calculated. CT airway measurements were compared between genders by using a mixed linear model. The correlations between height, TLC_CT and CT airway measurements were tested by using a Pearson correlation analysis. These correlations were arbitrarily considered as significant if there was a significant correlation observed for each of the six measurement sessions.

√WAPi10, WT^3rd and WT^4th were significantly different between genders. For both genders, there was no significant correlation between any airway measurements and TLC_CT. In females only, WT^3rd and WT^4th were significantly and negatively correlated with height.

√WAPi10, WT^3rd and WT^4th are different in males and females. WT^3rd and WT^4th are correlated with height in females only but not with TLC or in males. Advances in knowledge: CT airway measurements are influenced by gender and by height in females only but not by TLC. They should be adjusted according to gender and height in females.