Correlation of Spirometry and Body Plethysmography During Exercise-induced Bronchial Obstruction

Background: The exercise challenge is the gold standard for diagnosing exercise-induced bronchoconstriction (EIB). Airway obstructions appear up to 30 min after the challenge, with a maximum decrease in spirometry and a maximum increase in airway resistance. There is evidence that changes in body plethysmography parameters are more sensitive to the exercise challenge and precede those in spirometry.

Purpose: To compare changes in body plethysmography and spirometry parameters after exercise challenges and to verify the cut-off values of sReff in EIB.

Procedures: In 82 subjects with suspected EIB, a total of 473 lung function tests were measured at baseline and at 5, 10, 15, and 30 min after exercise challenges at different stages of bronchial obstruction.

Findings: The maximum changes in the body plethysmography parameter sReff significantly preceded the maximum changes in the spirometry parameter FEV (sReff: 12.2 min ±8.8, FEV: 15.2 min ±9.3, p < 0.005). The parameters of sReff and FEV had a strong negative correlation (r = -0.63, p < 0.0001) with a nonlinear, polynomial relationship. Furthermore, sReff and Reff had a strong linear correlation (r = 0.86, p < 0.001), and Reff and Rtot had a perfect linear correlation (r = 0.99, p < 0.001). Based on baseline values and on quantile regression, an increase of 0.25 kPa s in sReff was defined as significant. Using this cut-off value, FEV and sReff almost equally detected EIB.

Conclusion: The changes in sReff were more sensitive and better indicated lung impairment than did the changes in FEV, which underestimated the degree of hyperinflation.