• Respiratory care · Dec 2019

    Tidal Flow-Volume Loop Enveloping at Rest in Advanced COPD.

    • Luiz Felipe Fröhlich, Fernanda Machado Balzan, Franciele Plachi, Ricardo Gass, Nathalia Branco Schweitzer Mendes, da Silva Danton Pereira DP Jr Hospital de Clínicas de Porto Alegre, Rio Grande do Sul, Brazil., Paulo Robero Stefani Sanches, Marli M Knorst, J Alberto Neder, and Danilo Cortozi Berton.
    • Programa de Pós-Graduação em Ciências Pneumológicas, Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil.
    • Respir Care. 2019 Dec 1; 64 (12): 1488-1499.

    BackgroundExpiratory 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.Methods37 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.ResultsMost 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).ConclusionsTidal 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.Copyright © 2019 by Daedalus Enterprises.

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