Characteristics and determinants of endurance cycle ergometry and six-minute walk distance in patients with COPD
1 Department of Research & Education, CIRO+, Centre of Expertise for Chronic Organ Failure, Hornerheide 1, 6085 NM Horn, Eindhoven, Netherlands
2 BioSci Consulting, Weg naar Geneuth 95, 3631, Maasmechelen, Limburg, Belgium
3 Department of Respiratory Medicine, Catharina Hospital, Eindhoven, Netherlands
4 Department of Physical Education and Sport Sciences, National and Kapodistrian University of Athens, Ethnikis Antistasis 41, 17237 Athens, Greece
5 Institute of Clinical Exercise and Health Sciences, University of the West of Scotland, Paisley PA1 2BE, Scotland, United Kingdom
6 Department of Respiratory Medicine, Maastricht University Medical Centre (MUMC+), P.Debyelaan 25, 6202 AZ Maastricht, Netherlands
BMC Pulmonary Medicine 2014, 14:97 doi:10.1186/1471-2466-14-97Published: 31 May 2014
Exercise tolerance can be assessed by the cycle endurance test (CET) and six-minute walk test (6MWT) in patients with Chronic Obstructive Pulmonary Disease (COPD). We sought to investigate the characteristics of functional exercise performance and determinants of the CET and 6MWT in a large clinical cohort of COPD patients.
A dataset of 2053 COPD patients (43% female, age: 66.9 ± 9.5 years, FEV1% predicted: 48.2 ± 23.2) was analyzed retrospectively. Patients underwent, amongst others, respiratory function evaluation; medical tests and questionnaires, one maximal incremental cycle test where peak work rate was determined and two functional exercise tests: a CET at 75% of peak work rate and 6MWT. A stepwise multiple linear regression was used to assess determinants.
On average, patients had impaired exercise tolerance (peak work rate: 56 ± 27% predicted, 6MWT: 69 ± 17% predicted). A total of 2002 patients had CET time of duration (CET-Tend) less than 20 min while only 51 (2.5%) of the patients achieved 20 min of CET-Tend . In former patients, the percent of predicted peak work rate achieved differed significantly between men (48 ± 21% predicted) and women (67 ± 31% predicted). In contrast, CET-Tend was longer in men (286 ± 174 s vs 250 ± 153 s, p < 0.001). Also, six minute walking distance (6MWD) was higher in men compared to women, both in absolute terms as in percent of predicted (443 m, 67%predicted vs 431 m, 72%predicted, p < 0.05). Gender was associated with the CET-Tend but BMI, FEV1 and FRC were related to the 6MWD highlighting the different determinants of exercise performance between CET and 6MWT.
CET-Tend is a valuable outcome of CET as it is related to multiple clinical aspects of disease severity in COPD. Gender difference should temper the interpretation of CET.