Six-minute walk distance and work relationship with incremental treadmill cardiopulmonary exercise test in COPD

Authors


  • Authorship and contributorship Ms Poersch was in charge of exercise data collection; she took part in the analysis and interpretation of data, wrote the first draft of the manuscript and revised its later versions. Dr Berton was in charge of statistical planning and data analysis and interpretation; he revised earlier and later versions of the manuscript. Mr Canterle helped with data collection and interpretation; he revised later versions of the manuscript. Mr Castilho, Mr Lopes and Mr Martins supervised data collection, analysis and interpretation and revised later versions of the manuscript. Dr Oliveira and Dr Teixeira designed the study, supervised data collection, analysis and interpretation, and revised earlier and later versions of the manuscript.

  • Ethics This study has been reviewed by our institutional ethics committee and been performed in accordance with the ethical standards established in the 2000 Declaration of Helsinki. All study subjects gave their informed consent prior to their inclusion in the study and any details that might disclose their identity were omitted.

  • Conflict of interest The authors have stated explicitly that there are no conflicts of interest in connection with this article.

Paulo José Zimermann Teixeira, MD, DSc, Pavilhão Pereira Filho-Santa Casa de Porto Alegre, UFCSPA, Av. Independencia 155, 93510-250 Porto Alegre, RS, Brazil. Tel: +55 51 33469513, Fax: +55 51 33469513, email: paulozt@ufcspa.edu.br

Abstract

Introduction:  Cardiopulmonary exercise testing (CPET) is increasingly used to evaluate the overall impact of the illness on patients with chronic obstructive pulmonary disease (COPD). While laboratory tests of exercise performance are costly, the 6-min walk test (6-MWT) can be more easily performed. Although the main outcome commonly used in this field test is the distance walked in 6 min (6-MWD), this measure does not account for differences in body weight. Previous studies showed a good correlation between the work performed during the 6-MWT with incremental cycling CPET, an exercise modality more associated with quadriceps fatigability and with lower peak oxygen consumption inline image than incremental walking tests.

Objective:  Evaluate the correlation between the 6-MWD and its derivative body weight–walking distance product, an estimation of the work performed during the 6-MWT, with peak inline image from a treadmill CPET.

Methods:  Thirty COPD patients [forced expiratory volume in 1 s (FEV1) =  39 ± 13%; peak inline image predicted] performed CPET to the limit of tolerance on a treadmill and 6-MWT, 48 h apart.6-MWD and work were correlated to resting and exercise functional variables.

Results:  The work of walking during the 6-MWT provided greater associations with peak inline image than observed with 6-MWD. This was the case for FEV1, forced vital capacity, inspiratory capacity, lung diffusion capacity for carbon monoxide, peak inline image, carbon dioxide output, minute ventilation and double product (r = 0.57, r = 0.57, r = 0.73, r = 0.7, r = 0.75, r = 0.65, r = 0.51 and r = 0.4, respectively; all P < 0.05).

Conclusion:  A better association was found between the work estimated from the 6-MWT and peak inline image achieved during CPET, in this case with a treadmill, than the 6-MWD alone.

Please cite this paper as: Poersch K, Berton DC, Canterle DB, Castilho J, Lopes AL, Martins J, Oliveira AR and Teixeira PJZ. Six-minute walk distance and work relationship with incremental treadmill cardiopulmonary exercise test in COPD. Clin Respir J 2013; 7: 145–152.

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