Changes in the shape of expiratory flow-volume curves affect dead space and tidal volume patterns during exercise in patients with copd

SESSION TITLE: Pulmonary Physiology: Exercise Testing in the 21st Century SESSION TYPE: Original Investigations PRESENTED ON: 10/09/2023 10:30 am - 11:30 am PURPOSE: The rectangular area ratio (RAR) calculated from the spontaneous expiratory flow-volume curve during exercise can be used to identify if an expiratory-flow limitation develops (RAR < 0.5) during exercise (Porszasz et al., Respir Physiol Neurobiol, 2018). Volumetric capnography (VC) can determine the subcomponents of physiologic dead-space (VDphy), i.e. airway (VDaw) and alveolar (VDalv) relative to tidal volume (VT) during exercise. In this study, we investigated whether the change in RAR with bronchodilator (BD) vs. Placebo (PLA) therapy affected the dead space components during exercise. METHODS: Methods: 44 COPD patients completed two constant work rate exercise bouts at 80% peak work rate to intolerance following 2 weeks of either BD or PLA therapy. The rectangular area ratio (RAR) was calculated during exercise from the spontaneous expiratory flow-volume curve. VC was used to determine VDaw and VDalv components of VDphy during these exercise tests. RESULTS: Results: All data are presented at the final isotime point of the shorter exercise test. In 30 patients (63±7yr, 24 males, post-BD FEV1 62±16% pred), BD increased the RAR relative to PLA (0.50±0.08 → 0.53±0.07, p=0.003), “convex” profile. In 14 patients (62±9yr, 7 males, post-BD FEV1 61±19% pred) BD decreased the RAR relative to PLA (0.52±0.05 → 0.47±0.06, p=0.055), “concave” profile. The increase in endurance time (PLA to BD) was the same in both convex and concave groups (convex: 308±112 → 374±167s p = 0.13; concave: 360±110 → 433±238s; p =0.34 ). VDaw was similar during PLA in convex and concave groups (0.164±0.065 vs. 0.159±0.058L, p=0.51) but post-BD increased in convex patients without change in concave patients. VDalv was larger in convex vs. concave patients during PLA (0.336±0.176 vs. 0.184±0.173 L, p=0.009) but did not change in either group post-BD. VDphy was larger in convex vs. concave patients during PLA (0.509±0.199 vs. 0.342±0.205 L, p=0.013) but did not change in either group post-BD. VT was larger in convex vs. concave patients during PLA (1.53±0.48 vs. 1.07±0.49L, P=0.003) but did not change in either group post-BD. Because VDphy and VT were both proportionally higher in convex patients, VDphy/VT was the same in both convex and concave patients (0.34±0.086 vs. 0.34±0.11L, p=0.63), and did not change in either group with BD. CONCLUSIONS: Patients with a convex vs. concave expiratory-flow profile in response to BD during exercise in COPD are more likely to have a greater VDalv and VT at baseline, and a greater increase in VDaw on BD. However, these changes between convex and concave groups don’t affect the PLA or BD overall VDphy/VT, despite differences in RAR during exercise. CLINICAL IMPLICATIONS: Breath by Breath Volumetric Capnography allowing detailed analysis of the various components of dead space and the expiratory flow pattern of breaths combine to facilitate a greater understanding of the physiologic response to exercise in COPD. This is important as it applies to pharmacologic interventions, such as bronchodilators, etc., and should lead to a better understanding of individualized or personalized therapy for COPD patients with apparently similar pulmonary function testing at rest. DISCLOSURES: Advisory Committee Member relationship with Verona Please note: April, 2023 -present Added 05/22/2023 by Richard Casaburi, source=Web Response, value=Consulting fee Advisory Committee Member relationship with Inogen Please note: 2022- present Added 03/21/2023 by Richard Casaburi, value=Consulting fee Advisory Committee Member relationship with Genentech Please note: $1001 - $5000 by Richard Casaburi, value=Honoraria Removed 03/21/2023 by Richard Casaburi, source=Web Response Consultant relationship with Regeneron Please note: $1001 - $5000 by Richard Casaburi, value=Consulting fee Speaker/Speaker's Bureau relationship with GSK Please note: $5000 - $10,000 Added 03/21/2023 by Richard Casaburi, value=Honoraria Speaker/Speaker's Bureau relationship with Boehringer-Ingelheim Please note: $5001 - $20000 by Richard Casaburi, value=Honoraria Removed 03/21/2023 by Richard Casaburi, source=Web Response Contracted research relationship with Regeneron Please note: June 2021-current Added 03/28/2023 by Carrie Ferguson, source=Web Response, value=Grant/Research Support Contracted research relationship with United Therapeutics Please note: June 2021-current Added 03/28/2023 by Carrie Ferguson, source=Web Response, value=Grant/Research Support No relevant relationships by Divya Narayanan No relevant relationships by Janos Porszasz Consultant relationship with Regeneron Please note: 2021-2022 Added 11/07/2022 by William Stringer, source=Web Response, value=Consulting fee Clinical Research Site relationship with Genentech Please note: 2021-Present Added 11/07/2022 by William Stringer, source=Web Response, value=Grant/Research Support Site Researcher relationship with Regeneron Please note: 2021-2022 by William Stringer, value=Consulting fee Reduced Fee Medical Equipment relationship with Medical Graphics Corporation Please note: 2021 by William Stringer, value=Equipment Consultant relationship with Vyair Medical, Inc. Please note: 2020 by William Stringer, value=Consulting fee Removed 11/08/2022 by William Stringer, source=Web Response Research Clinical Trial relationship with Department of Defense Please note: 2016 to Present by William Stringer, value=Grant/Research Support Consultant relationship with Syneos DSMB Please note: 2018 to Present by William Stringer, value=Consulting fee Investigator relationship with Boehringer-Ingelheim Please note: 2016-2021 by William Stringer, value=Grant/Research Support Author relationship with Wolters Kluwer Please note: 2011 to Present by William Stringer, value=Royalty No relevant relationships by Chu-Yi Wang