C72-24 Cardiopulmonary Exercise Testing and Oscillometry for the Evaluation of Dyspnea (COED) Trial

Abstract Rationale Dyspnea evaluation is a complex process that requires an extensive workup. Dyspnea evaluation suffers from a lack of standardized framework in part due to its often-multifactorial nature and subjective symptoms. Tests are often negative, inconclusive, costly and time consuming. We wondered whether pre- and post-exercise airway oscillometry (AOS) testing to measure static and dynamic airway caliber and peripheral airway behavior could provide new insights into the etiology of unexplained dyspnea. Specifically, we proposed that tidal expiratory flow limitation (tEFL; inspiratory minus expiratory reactance at 5Hz, X5) measured by AOS before exercise might be predictive of expiratory flow limitation (EFL; 40% overlap of tidal expiratory flow volume curve with maximal curve) measured by cardiopulmonary exercise testing (CPET). Additionally, we aimed to use AOS for the evaluation of airway hyperresponsiveness (AHR; 10% decline in FEV1), using three thresholds proposed for oscillometry-defined AHR (Criteria #1: R5, resistance at 5 Hz, increase of 47% or X5 decrease of 50%. Criteria #2: R5 increase of 27% and X5 decrease of 47%). Methods Twenty subjects (age 18 years) at a single center referred to CPET for any reason were enrolled in our study. Pregnant and incarcerated individuals were excluded. Basic demographic data, medical history, anthropometry (BMI, neck circumference and hip:waist ratio) and patient reported outcomes (mBORG, dyspnea 12 and International Physical Activity Questionnaire) were completed. AOS was performed using a THORASYS® tremoFlo® C-100 Airwave Oscillometry System™ before and immediately after a standard CPET protocol. Results Four out of 20 subjects demonstrated tEFL prior to CPET. 100% of these subjects demonstrated both dynamic hyperinflation (DH) and EFL during CPET. Additionally, 12 subjects exhibited EFL during CPET but did not have tEFL prior to exercise. The ROC analysis for tEFL had an AUC of 0.64 CI: 0.39, 0.89; p = 0.28. With a tEFL threshold of 1 cmH2O·s/L, the test achieved a sensitivity of 25% and specificity of 100%. No subjects met criteria for AHR by FEV1 criteria. By AOS criteria, up to three subjects met the definition for AHR based on previously published thresholds (Figure 1). Conclusions tEFL was highly predictive of EFL during exercise but lacked sensitivity. With high pretest probability for ventilatory limitation in exercise, the occurrence of tEFL on AOS may preclude the need for CPET. AOS may be more sensitive for the diagnosis of exercise-induced AHR than spirometry. Further investigation is needed to test these possibilities using larger cohorts of subjects. This abstract is funded by: T32HL171029