Abstract
Background: Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL). Tidal EFL has not been expressed as a continuous variable (0% - 100%) in previous analyses. Objective: To relate the magnitude of tEFL to spirometric values and Modified Medical Research Council (MMRC) score and Asthma Control Test (ACT). Methods: Tidal EFL was computed as percent of the tidal volume (0% - 100%) spanned (intersected) by the forced expiratory-volume curve. Results: Of 353 patients screened, 192 (114 M, 78 F) patients (136 with COPD, 56 with asthma) had CAL. Overall characteristics: (mean ± SD) age 59 ± 11 years, BMI 28 ± 7, FVC (% pred) 85 ± 20, FEV1 (% pred) 66 ± 21, FEV1/FVC 55% ± 10%, RV (% pred) 147 ± 42. Tidal EFL in patients with tEFL was 53% ± 39%. Using univariate analysis, strongest correlations were between tEFL and FVC and between tEFL and RV in patients with BMI 2. In patients with nonreversible CAL, tEFL was positively associated with increasing MMRC, negatively with spirometric measurements, and positively with RV/TLC. In asthmatics, ACT scores were higher in patients with mean BMI ≥ 28 kg/m2 (p 40% (p Conclusions: Dyspnea is strongly associated with tEFL and lung function, particularly in patients with nonreversible CAL. Air trapping and BMI contribute to tEFL.
Highlights
Tidal expiratory flow limitation is defined as absence of increase in air flow during forced expiration effort compared to tidal breathing and correlates with dyspnea at rest better than it does with FEV1 [1] [2] [3]
Asthma Control Test (ACT) scores were higher in patients with mean BMI ≥ 28 kg/m2 (p < 0.00014) and RV/TLC values > 40% (p < 0.03)
Dyspnea is closely associated with Tidal expiratory flow limitation (tEFL), spirometric values and hyperinflation, in patients with nonreversible airflow limitation
Summary
Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration effort compared to tidal breathing and correlates with dyspnea at rest better than it does with FEV1 [1] [2] [3]. Analysis of the forced expiratory flow-volume curve as part of spirometry remains the standard by which respiratory function and impairment are assessed in community and academic settings. We are not aware of any quantitative analysis of association of the FEFV-generated tEFL with commonly used indices of dyspnea in patients with nonreversible and reversible airflow limitation. Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL).
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