• Yukio Fujita, Motoo Yamauchi, Masanori Yoshikawa, Yoshifumi Yamamoto, Kazuhiro Sakaguchi, Nobuhiro Fujioka, Takahiro Ibaraki, and Shigeo Muro.
• Department of Respiratory Medicine, Nara Medical University, Kashihara, Japan. ffyukio0314@gmail.com.
• Respir Care. 2021 Sep 1; 66 (9): 147714841477-1484.

BackgroundDyspnea is a common symptom in patients with COPD. It causes physical inactivity and impaired health-related quality of life. Although optimal breathing methods alleviate dyspnea, it is unclear whether breathing instability has a clinical impact on patients with COPD. This study aimed to investigate whether resting breathing instability during wakefulness was associated with dyspnea assessed by the modified Medical Research Council (mMRC) dsypnea scale and whether breathing instability can be a novel predictor of clinical outcomes.MethodsForty-four subjects with stable COPD were enrolled (mean age, 71.0 y). Resting breathing was monitored for 15 min by using respiratory inductance plethysmography. Breathing instability was evaluated with the coefficient of variation for breath-by-breath respiratory duration and tidal volume ([Formula: see text]) by using an artifact-free respiratory signal for 5 min. Pulmonary function testing and blood gas analysis were performed (mean FEV1 percent of predicted, 68.5%). Questionnaires with regard to dyspnea and health-related quality of life were also completed. Exacerbations were recorded prospectively for 1 year after the initial assessment.ResultsThe coefficients of variation for [Formula: see text] were significantly higher in the subjects with an mMRC dyspnea scale score ≥ 2 versus those with an mMRC dyspnea scale score < 2 (26.4 ± 7.4% vs 20.3 ± 6.4%, P = .006) . The coefficients of variation for respiratory duration and VT were not associated with age, body mass index, and pulmonary function variables. In multivariate analysis, FEV1 percent of predicted and coefficient of variation for [Formula: see text] remained significant predictors for an mMRC dyspnea scale score ≥ 2 (P = .004 and P = .01, respectively). Coefficient of variation values were also correlated with several health-related quality of life domains. The exacerbation frequency was associated with the coefficient of variation for [Formula: see text].ConclusionsResting breathing pattern during wakefulness is a novel assessment tool for severity of dyspnea, which can be one of the predictors for exacerbation in patients with COPD.Copyright © 2021 by Daedalus Enterprises.

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