Indoor vs. Outdoor Exercise Challenge Testing In Patients With Suspected Reactive Airways Disease And Negative Methacholine Challenge Tests

Abstract

INTRODUCTION: Methacholine challenge testing (MCCT) has been proposed in the evaluation of dyspnea but has limitations. Running has been proposed as alternative method to diagnose exercise induced asthma (EIA). PURPOSE: To evaluate the utility of a portable cardiopulmonary exercise testing system during running challenges (indoor vs outdoor) in 2 different environments to evaluate EIA. METHODS: 26 patients with dyspnea on exertion and negative MCCT randomly performed both indoor & outdoor run challenge while wearing a Jaeger Oxycon™ Mobile CPX system. Baseline pulmonary function testing (PFTs) followed by exercise challenge testing using ATS guidelines was used. Serial PFTs were measured 5, 10, 15, 20 mins. A B2 agonist was then administered followed by one final spirometry PFT at 10 minutes post bronchodilator. Run testing in 2 environments was standardized by measuring CPX varibles. Environmental conditions measured included humidity, temperature, particulate matter, pollen counts, carbon dioxide levels, microbiological and fungal spores. RESULTS: Percent Change FEV1 Post Run Challenge. No statistically significant differences in any cardiopulmonary variables measured (VO2, VCO2, RR, HR, RER, VE, VE/VO2 & VE/VCO2) at any time point verifying that the exercise testing was of equal intensity both for indoor & outdoor testing conditions. CONCLUSIONS: There was no signifcant difference in FEV1 post exericse indoor vs outdoor run testing. Stepwise linear regression did not show significant environmental effect. MCCT testing for our patient population proved robust in that further exercise testing with respect to both test location and environmental factors did not result in any significant changes in measured performance.