Predictors in routine practice of 6-min walking distance and oxygen desaturation in patients with COPD: impact of comorbidities
Received 1 October 2018
Accepted for publication 26 April 2019
Published 2 July 2019 Volume 2019:14 Pages 1399—1410
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Cristina Weinberg
Peer reviewer comments 4
Editor who approved publication: Dr Richard Russell
Thierry Perez,1 Gaëtan Deslée,2 Pierre Régis Burgel,3 Denis Caillaud,4 Olivier Le Rouzic,1 Maeva Zysman,5 Roger Escamilla,6 Gilles Jebrak,7 Pascal Chanez,8 Isabelle Court-Fortune,9 Graziella Brinchault-Rabin,10 Pascale Nesme-Meyer,11 Jean-Louis Paillasseur,12 Nicolas Roche,3 On behalf of the Initiatives BPCO Scientific Committee
1CHU 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; 2Department of Respiratory Diseases, Maison Blanche Hospital, CHU de Reims, INSERM UMRS 1250, Reims, France; 3Respiratory and Intensive Care Medicine Department, Cochin Hospital, AP-HP and Paris Descartes University (EA 2511), Sorbonne Paris Cité, Paris, France; 4Department of Respiratory Diseases, Gabriel Montpied Hospital, CHU de Clermont Ferrand, Clermont Ferrand, France; 5Department of Respiratory Diseases, CHU Nancy, Nancy, France; 6Department of Respiratory Diseases, CHU Toulouse, Toulouse, France; 7Department of Respiratory Diseases, Hôpital Bichat, APHP, Paris, France; 8Department of Respiratory Diseases, AP-HM, Université de Méditerranée, Inserm U 1077, Marseille, France; 9Department of Respiratory Diseases, CHU Saint Etienne, Saint Etienne, France; 10Department of Respiratory Diseases, Pontchaillou Hospital, CHU Rennes, Rennes, France; 11Department of Respiratory Diseases, La Croix Rousse Hospital, Lyon, France; 12EFFI-STAT, Paris, France
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/m2,), low BMI (BMI <18.5 kg/m2,), 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 r2,=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 r2,=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.
Keywords: 6-min walk test, distance, COPD, obesity, comorbidities, severity
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