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      Application of a new parameter in the 6-minute walk test for manifold analysis of exercise capacity in patients with COPD

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          Abstract

          Background

          New parameters in the 6-minute walk test (6MWT) are required for comprehensive analysis of exercise capacity in patients with chronic obstructive pulmonary disease (COPD). The aim of the present study was to apply a novel index, the desaturation distance ratio (DDR), to clinical research on COPD as an estimate of exercise capacity and to examine whether DDR is a potential parameter for manifold analysis of exercise capacity in patients with COPD.

          Methods

          A total of 41 patients with COPD (median age [interquartile range] =75 [68–79] years; and body mass index [BMI] =22.3 [19.4–23.8] kg/m 2) participated in the study. The 6MWT was performed along with anthropometric measurements and a pulmonary function test. The “desaturation area” was measured as the total area above the curve created using peripheral oxygen saturation (SpO 2) values observed at each minute during the 6MWT. Then the DDR was calculated as the ratio of the desaturation area to the 6-minute walk distance (6MWD).

          Results

          The 6MWD was 370 (328–445) m, and the decline in SpO 2 values (ΔSpO 2) was −5.0% (−8.0% to −1.5%). The DDR correlated modestly with baseline pulmonary function in patients with COPD (forced expiratory volume in 1 second [% of predicted value]: r=−0.658, P<0.001; and diffusing capacity of the lung for carbon monoxide [DL CO]: r=−0.470, P=0.002), comparable with the findings of the 6MWD. The DDR correlated well with ΔSpO 2 ( r=−0.656, P<0.001) and with the increase in subjective sense of dyspnea during the 6MWT, as assessed by Borg scale scores (ΔBorg) ( r=0.486, P=0.001), in contrast with the 6MWD, which was not significantly correlated with ΔSpO 2 and ΔBorg scale scores.

          Conclusion

          The DDR is more informative for manifold analysis of exercise capacity associated with oxygen desaturation and subsequent sense of dyspnea by exercise in patients with COPD.

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          Most cited references 21

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          The global burden of disease, 1990-2020.

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            Characteristics of physical activities in daily life in chronic obstructive pulmonary disease.

            Quantification of physical activities in daily life in patients with chronic obstructive pulmonary disease has increasing clinical interest. However, detailed comparison with healthy subjects is not available. Furthermore, it is unknown whether time spent actively during daily life is related to lung function, muscle force, or maximal and functional exercise capacity. We assessed physical activities and movement intensity with the DynaPort activity monitor in 50 patients (age 64 +/- 7 years; FEV1 43 +/- 18% predicted) and 25 healthy elderly individuals (age 66 +/- 5 years). Patients showed lower walking time (44 +/- 26 vs. 81 +/- 26 minutes/day), standing time (191 +/- 99 vs. 295 +/- 109 minutes/day), and movement intensity during walking (1.8 +/- 0.3 vs. 2.4 +/- 0.5 m/second2; p < 0.0001 for all), as well as higher sitting time (374 +/- 139 vs. 306 +/- 108 minutes/day; p = 0.04) and lying time (87 +/- 97 vs. 29 +/- 33 minutes/day; p = 0.004). Walking time was highly correlated with the 6-minute walking test (r = 0.76, p < 0.0001) and more modestly to maximal exercise capacity, lung function, and muscle force (0.28 < r < 0.64, p < 0.05). Patients with chronic obstructive pulmonary disease are markedly inactive in daily life. Functional exercise capacity is the strongest correlate of physical activities in daily life.
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              The 6-minute walk: a new measure of exercise capacity in patients with chronic heart failure.

              Cycle and treadmill exercise tests are unsuitable for elderly, frail and severely limited patients with heart failure and may not reflect capacity to undertake day-to-day activities. Walking tests have proved useful as measures of outcome for patients with chronic lung disease. To investigate the potential value of the 6-minute walk as an objective measure of exercise capacity in patients with chronic heart failure, the test was administered six times over 12 weeks to 18 patients with chronic heart failure and 25 with chronic lung disease. The subjects also underwent cycle ergometer testing, and their functional status was evaluated by means of conventional measures. The walking test proved highly acceptable to the patients, and stable, reproducible results were achieved after the first two walks. The results correlated with the conventional measures of functional status and exercise capacity. The authors conclude that the 6-minute walk is a useful measure of functional exercise capacity and a suitable measure of outcome for clinical trials in patients with chronic heart failure.
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                Author and article information

                Journal
                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                1176-9106
                1178-2005
                2014
                03 November 2014
                : 9
                : 1235-1240
                Affiliations
                [1 ]Department of Respiratory Medicine, Graduate School of Medicine, Osaka City University, Osaka, Japan
                [2 ]Department of Sports Medicine, Graduate School of Medicine, Osaka City University, Osaka, Japan
                Author notes
                Correspondence: Hiroshi Kanazawa, Department of Respiratory Medicine, Graduate School of Medicine, Osaka City University, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan, Tel +81 6 6645 3916, Fax +81 6 6646 6067, Email kanazawa-h@ 123456med.osaka-cu.ac.jp
                Article
                copd-9-1235
                10.2147/COPD.S71383
                4224096
                © 2014 Ijiri et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

                The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

                Categories
                Original Research

                Respiratory medicine

                6mwd, six-minute walk distance, ddr, chronic obstructive pulmonary disease

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