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Variable Extrathoracic Obstruction Correlates With Higher Body Mass Index Among Adults With Asthma FREE TO VIEW

Emily Brigham, MD; Danielle Boyce, MPH; Meredith McCormack, MD
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The Johns Hopkins University, Baltimore, MD

Chest. 2013;144(4_MeetingAbstracts):837A. doi:10.1378/chest.1704865
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SESSION TITLE: Physiology/PFTs/Rehabilitation Posters

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PM

PURPOSE: Variable extrathoracic obstruction (VEO), flattening of the inspiratory limb on spirometric flow-volume loops, is linked to structural and functional abnormalities of the upper airway. Though VEO has been inconsistently associated with sleep disordered breathing, a disease highly correlated with obesity, little evidence is available evaluating a direct association between VEO and obesity. Despite mounting evidence linking obesity and asthma, even less is known about the relationship between VEO and obesity in asthma. We sought to characterize the relationship between body mass index (BMI) and abnormal flow in the upper airways, indicated by VEO, among patients referred for testing in the Johns Hopkins PFT lab and among those with a referring diagnosis of asthma.

METHODS: A total of 7,961 pulmonary function tests (PFTs) between October 2007 and January 2013 on unique patients at Johns Hopkins Hospital were included. VEO was defined as ratio of forced inspiratory to forced expiratory flow at 50% of vital capacity (FEF50/FIF50) of > 1. BMI was examined as a continuous and as a categorical variable (WHO classifications: BMI <18.5, 18.5-<25, 25-<30, 30-<35, 35-<40, >40). T-test and Pearson chi-2 were used for VEO versus BMI among all patients and the subgroup with a referring diagnosis of asthma.

RESULTS: Among all comers, mean BMI was 28.9 kg/m2 (SD 7.9), with no significant difference in prevalence of VEO by BMI as a continuous variable (p=0.52) and remained insignificant as a categorical variable. Among the 5.7% with asthma referring diagnosis, VEO was associated with increasing BMI, as a continuous variable (p<0.01 for both), and remained significant as a categorical variable.

CONCLUSIONS: While increasing BMI was not associated with VEO among patients tested in a University hospital-based PFT laboratory, there was a significant association between the presence of VEO and increasing BMI among those with a referring diagnosis of asthma.

CLINICAL IMPLICATIONS: While the clinical significance of this finding remains unclear, potential explanations include that patients had comorbid upper airway conditions, a misdiagnosis of asthma, or that there is a unique association between VEO and asthma among those with elevated BMI.

DISCLOSURE: The following authors have nothing to disclose: Emily Brigham, Danielle Boyce, Meredith McCormack

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