Identification of Three Exercise-induced Mortality Risk Factors in Patients with COPD. (1st December 2014)

• Record Type: Journal Article
• Authors: Yoshimura, Kenji; Maekura, Ryoji; Hiraga, Toru; Miki, Keisuke; Kitada, Seigo; Miki, Mari; Tateishi, Yoshitaka; Mori, Masahide
• Is Part Of: COPD. Volume 11:Number 6(2014:Dec.)
• Page Start: 615
• Page End: 626
• Publication Date: 2014-12-01
• Subjects: Lungs -- Diseases, Obstructive -- Periodicals; 616.24
• DOI: 10.3109/15412555.2014.898038
• Languages: English
• ISSNs: 1541-2555

Abstract

<abstract> <title>Abstract</title> <p>The survival rate of chronic obstructive pulmonary disease (COPD) patients with severely reduced exercise capacity is extremely low. We recently identified three life-threatening pathophysiological conditions during cardiopulmonary exercise testing (CPET): (1) exercise-induced hypoxemia, (2) sympathetic overactivity, and (3) progressive respiratory acidosis at low-intensity exercise. The present prospective observation study aimed to determine whether these parameters constitute risk factors of mortality in moderate-to-very severe COPD. Ninety-six COPD patients were followed-up, monthly, for >3 years. Subsequently, spirometry and CPET were performed to examine parameters of exercise-induced hypoxemia ([PaO<sub>2</sub> slope, mmHg/L · min<sup>−1</sup>] = Decrease in PaO<sub>2</sub>/ΔV˙ O<sub>2</sub> (Difference in ΔV˙ O<sub>2</sub> between at rest and at peak exercise)), progression of acidosis ([ΔpH/ΔV˙ O<sub>2</sub>, /L · min<sup>−1</sup>] = Decrease in pH/ΔV˙ O<sub>2</sub>), and sympathetic overactivity ([Δnorepinephrine (NE)/ΔV˙ O<sub>2</sub>, ng/mL/L · min<sup>−1</sup>] = Increase in NE/ΔV˙ O<sub>2</sub>). Univariate analysis revealed a significant association between the three conditions with increased mortality. Kaplan–Meier analysis showed that the quartile combining the steepest PaO<sub>2</sub> slope (≤–55 mmHg/ΔV˙ O<sub>2</sub> [L/min]), steepest decrease in arterial blood pH (≤ –1.72/ΔV˙ O<sub>2</sub> [L/min]), and most rapid increase in plasma NE level (≥ 5.2 ng/VO<sub>2</sub> [L/min]) during incremental exercise was associated with higher all-cause mortality. These conditions showed cumulative effects on COPD patients' survival. Multivariate analyses revealed that these three life-threatening factors are also independent predictors of mortality based on age, heart rate and PaO<sub>2</sub> at rest, body mass index, and forced expiratory volume in 1 s. Thus, these new exercise-induced mortality risk factors may lead to more efficient pulmonary rehabilitation programs for COPD patients based on patient-specific exercise-induced pathophysiological profiles.</p> </abstract>