TY - JOUR T1 - Tidal Flow-Volume Loop Enveloping at Rest in Advanced COPD JF - Respiratory Care SP - 1488 LP - 1499 DO - 10.4187/respcare.06787 VL - 64 IS - 12 AU - Luiz Felipe Fröhlich AU - Fernanda Machado Balzan AU - Franciele Plachi AU - Ricardo Gass AU - Nathalia Branco Schweitzer Mendes AU - Danton Pereira da Silva, Jr AU - Paulo Robero Stefani Sanches AU - Marli M Knorst AU - J Alberto Neder AU - Danilo Cortozi Berton Y1 - 2019/12/01 UR - http://rc.rcjournal.com/content/64/12/1488.abstract N2 - BACKGROUND: Expiratory flow limitation (EFL) is a key physiological abnormality in COPD. Comparing tidal-to-maximum flow-volume (F-V) loops is a simple and widely available method to assess EFL in patients with COPD. We aimed to investigate whether subjects with COPD showing significant resting tidal F-V enveloping (ie, > 50% tidal volume) would present with higher exertional operating lung volumes, which would lead to greater burden of dyspnea and poorer exercise tolerance compared to their counterparts.METHODS: 37 subjects with COPD (21 males; 63.1 ± 9.2 years old; FEV1 = 37 ± 12% predicted) and 9 paired controls (3 males; 55.9 ± 11.7 y old) performed an incremental cardiopulmonary exercise testing on a cycle ergometer. Dyspnea perception, inspiratory capacity maneuvers after 3–4 sequential tidal F-V loops, and esophageal and gastric pressures were measured during exercise.RESULTS: Most subjects (31 of 37, 84%) presented with significant tidal F-V enveloping. Critical inspiratory constraints and upward dyspnea inflection points (as a function of both work rate and ventilation) were reached earlier in these subjects, thereby leading to poorer exercise tolerance compared to their counterparts (P = .01). Abdominal muscle recruitment (ie, increase in gastric pressure ≥ 15%) during tidal expiration was significantly higher in the EFL+ group. However, this did not bear an influence on the operating lung volumes, inspiratory constraints, dyspnea, cardiocirculatory responses, or exercise tolerance (P > .05).CONCLUSIONS: Tidal F-V loop enveloping at rest should be valued as it is related to relevant clinical outcomes, such as dyspnea burden and exercise tolerance in subjects with COPD. ER -