Abstract Rationale Within- or intra-breath change in oscillometric reactance (ΔX5) is a reliable marker of expiratory flow limitation (EFL) in individuals with COPD. A recent study in COPD also found that a faster rate of EFL development (ELDI) is associated with worse clinical and physiological characteristics. Although these measures have been studied among individuals with COPD, how they perform in those with asthma is unknown. Therefore, we sought to investigate EFL parameters (i.e., ELDI and X5 peak-to-peak) and ELDI among a treatment seeking Veteran cohort with and without asthma. Methods Veterans completed pulmonary function testing (PFT) and respiratory oscillometry (pre- and post-bronchodilator) as part of a standardized clinical evaluation. Raw oscillometry data were analyzed using a custom script to calculate ELDI and X5 peak-to-peak see Figure 1. Asthma was defined as the presence of bronchodilator reversibility (≥10% change in FEV1) or a positive methacholine test (PD20 400 µg). Group comparisons were conducted using the Wilcoxon rank sum test. Results Oscillometry and PFT results from 42 Veterans were included in this study. Nine (21%) met criteria for asthma. The asthmatic group were all male, 44 years of age, 67% white, had a body mass index (BMI) of 32.7, 5% never smoked and had an average deployment total of 574 days. Non-asthmatics were 85% males, 45 years of age, 73% white, had a BMI of 31.3, 61% never smoked and had an average deployment total of 540 days. Veteran demographics and pre-bronchodilator EFL parameters were not significantly different between groups. Compared to the non-asthma group, those who met the asthma definition had lower ELDI post-bronchodilator (Median Difference: 0.06, p = 0.042) and higher X5 peak-to-peak post-bronchodilator (Median Difference: 1.03, p = .0005). Conclusion In our Veteran sample, EFL parameters post-bronchodilator were significantly different between asthmatic Veterans and non-asthmatic Veterans, however, pre-bronchodilator and delta (post-pre bronchodilator) values were not different. This may be because these EFL measures were developed on COPD cohorts, and these measures may not translate directly to an unobstructed population. Further research is needed to examine these measures in a broader context outside of COPD cohorts. This abstract is funded by: This work is supported by the VHA Airborne Hazards and Burn Pits Center of Excellence (PL 115-929). The contents to not represent those of the US. Government or Department of Veterans Affairs.
Phen et al. (Fri,) studied this question.