Tracheal measurement

Correlation coefficient (r) for differences in spirometric values*

FEV₁

FEV₁

(% predicted)

FEV₁/FVC

FEF_25-75%

FEF_25-75%

(% predicted)

Peak flow

Difference in minimumtracheal CSA*

0.446

(P < 0.05)

0.418

(P < 0.05)

0.594

(P < 0.01)

0.240

(NS)

0.250

(NS)

0.397

(P < 0.05)