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      Predictors in routine practice of 6-min walking distance and oxygen desaturation in patients with COPD: impact of comorbidities

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          Background: The 6-min walk test (6MWT) allows exercise tolerance to be assessed, and it has a significant prognostic value in COPD. The goal of this study was to analyse the determinants (obtained in routine practice) of a low 6-min walking distance (6MWD) and exercise-induced desaturation (EID) in COPD, including comorbidities.

          Methods: Patients were recruited from the real-life French COPD cohort “Initiatives BPCO”. A low 6MWD was defined as <350 m. EID was defined by a minimum pulse oxygen saturation (SpO2)<90% and delta SpO2≥4% from baseline. Multivariate logistic regression analyses assessed the influence on 6MWD and EID of age, sex, obesity (body mass index, BMI >30 kg/m 2), low BMI (BMI <18.5 kg/m 2), modified Medical Research Council (mMRC) dyspnea scale, FEV1% pred, FVC % pred, hyperinflation and comorbidities including cardiovascular diseases.

          Results: Among 440 patients with available 6MWT data, a 6MWD <350 m was found in 146 patients (33%), which was positively associated in multivariate analyses with age and mMRC and negatively with resting SpO2 and FVC % pred (rescaled r 2=0.34), whereas no comorbidity was associated with a low 6WMD. EID was found in 155 patients (35%). This was positively associated with hypertension and negatively with age, obesity, FEV1% pred and resting SpO2 (rescaled r 2=0.37).

          Conclusion: 6MWD and EID exhibit different determinants in COPD with a minor impact of comorbidities limited to hypertension in EID and to obesity, which was unexpectedly associated with less EID. Other variables including age, routine resting lung function and SpO2 were weakly associated with 6MWD and EID. Altogether, these results suggest that 6MWT performance remains difficult to predict with routine clinical/functional parameters.

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          Most cited references 21

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          Anxiety and depression in COPD: current understanding, unanswered questions, and research needs.

          Approximately 60 million people in the United States live with one of four chronic conditions: heart disease, diabetes, chronic respiratory disease, and major depression. Anxiety and depression are very common comorbidities in COPD and have significant impact on patients, their families, society, and the course of the disease. We report the proceedings of a multidisciplinary workshop on anxiety and depression in COPD that aimed to shed light on the current understanding of these comorbidities, and outline unanswered questions and areas of future research needs. Estimates of prevalence of anxiety and depression in COPD vary widely but are generally higher than those reported in some other advanced chronic diseases. Untreated and undetected anxiety and depressive symptoms may increase physical disability, morbidity, and health-care utilization. Several patient, physician, and system barriers contribute to the underdiagnosis of these disorders in patients with COPD. While few published studies demonstrate that these disorders associated with COPD respond well to appropriate pharmacologic and nonpharmacologic therapy, only a small proportion of COPD patients with these disorders receive effective treatment. Future research is needed to address the impact, early detection, and management of anxiety and depression in COPD.
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            Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease: a clinical trial. Nocturnal Oxygen Therapy Trial Group.

            At six centers, 203 patients with hypoxemic chronic obstructive lung disease were randomly allocated to either continuous oxygen (O2) therapy or 12-hour nocturnal O2 therapy and followed for at least 12 months (mean, 19.3 months). The two groups were initially well matched in terms of physiological and neuropsychological function. Compliance with each oxygen regimen was good. Overall mortality in the nocturnal O2 therapy group was 1.94 times that in the continuous O2 therapy group (P = 0.01). This trend was striking in patients with carbon dioxide retention and also present in patients with relatively poor lung function, low mean nocturnal oxygen saturation, more severe brain dysfunction, and prominent mood disturbances. Continuous O2 therapy also appeared to benefit patients with low mean pulmonary artery pressure and pulmonary vascular resistance and those with relatively well-preserved exercise capacity. We conclude that in hypoxemic chronic obstructive lung disease, continuous O2 therapy is associated with a lower mortality than is nocturnal O2 therapy. The reason for this difference is not clear.
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              Distance and oxygen desaturation during the 6-min walk test as predictors of long-term mortality in patients with COPD.

              The distance walked in the 6-min walk test (6MWT) predicts mortality in patients with severe COPD. Little is known about its prognostic value in patients with a wider range of COPD severity, living in different countries, and the potential additional impact of oxygen desaturation measured during the test. We enrolled 576 stable COPD outpatients in Spain and the United States and observed them for at least 3 years (median, 60 months). We measured FEV1, body mass index, Pao2, Charlson comorbidity score, 6-min walk distance (6MWD), and oxygen saturation by pulse oximetry (Spo2) during the 6MWT. Desaturation was defined as a fall in Spo2 > or = 4% or Spo2 < 90%. Regression analysis helped determine the association between these variables and all-cause and respiratory mortality. The 6MWD was a good predictor of all-cause and respiratory mortality primarily in patients with FEV1 < 50% of predicted (p < 0.001) after adjusting for all covariates. Patients with desaturation during the 6MWT had a higher mortality rate than patients without desaturation (67% vs 38%, p < 0.001). Oxygen desaturation predicted mortality (relative risk, 2.63; 95% confidence interval, 1.53 to 4.51; p < 0.001) but with less power than Pao2 at rest. The 6MWD helps predict mortality primarily in patients with severe COPD. Although the oxygen desaturation profile during the 6MWT improves the predictive ability of the 6MWD, it appears to be of less relevance than in other lung diseases and than the resting Pao2.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of Chronic Obstructive Pulmonary Disease
                02 July 2019
                : 14
                : 1399-1410
                [1 ] CHU Lille, Department of Respiratory Diseases, F-59000 Lille and Univ. Lille, Center for Infection and Immunity of Lille, INSERM U1019 - CNRS UMR 8204, F-59000 , Lille, France
                [2 ] Department of Respiratory Diseases, Maison Blanche Hospital, CHU de Reims, INSERM UMRS 1250 , Reims, France
                [3 ] Respiratory and Intensive Care Medicine Department, Cochin Hospital, AP-HP and Paris Descartes University (EA 2511), Sorbonne Paris Cité , Paris, France
                [4 ] Department of Respiratory Diseases, Gabriel Montpied Hospital, CHU de Clermont Ferrand , Clermont Ferrand, France
                [5 ] Department of Respiratory Diseases, CHU Nancy , Nancy, France
                [6 ] Department of Respiratory Diseases, CHU Toulouse , Toulouse, France
                [7 ] Department of Respiratory Diseases, Hôpital Bichat, APHP , Paris, France
                [8 ] Department of Respiratory Diseases, AP-HM, Université de Méditerranée, Inserm U 1077 , Marseille, France
                [9 ] Department of Respiratory Diseases, CHU Saint Etienne , Saint Etienne, France
                [10 ] Department of Respiratory Diseases, Pontchaillou Hospital, CHU Rennes , Rennes, France
                [11 ] Department of Respiratory Diseases, La Croix Rousse Hospital , Lyon, France
                [12 ] EFFI-STAT , Paris, France
                Author notes
                Correspondence: Thierry PerezHôpital Calmette, CHRU de Lille , Bd J Leclercq, Lille cedex59037, FranceTel +33 32 044 5619Email thierry.perez@
                © 2019 Perez et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (

                Page count
                Figures: 2, Tables: 4, References: 41, Pages: 12
                Original Research

                Respiratory medicine

                severity, 6-min walk test, distance, copd, obesity, comorbidities


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