Abstract
Dyspnoea should be measured at a standardised level of exertion http://ow.ly/kpMQ30jWXau
From the authors:
We would like to thank M. Ekström and colleagues for their correspondence with comments on our article entitled “Effects of inspiratory muscle training on dyspnoea in severe COPD patients during pulmonary rehabilitation: a controlled randomised trial” [1]. We agree with most of the points underlined by M. Ekström and colleagues.
As mentioned, a limitation of our study is that dyspnoea at exertion was not evaluated at the same level of effort. Indeed, we measured dyspnoea at exertion at the end of the 6-min walk test (6MWT), which does not allow comparison of dyspnoea at the same level of effort. The 6MWT is a well-standardised exercise test according to the guidelines by Holland et al. [2]. We performed the 6MWT as it is recommended by the American Thoracic Society/European Respiratory Society task force, including standardised instructions which limit performance variations. Moreover, as the 6MWT is a submaximal test, consequently, dyspnoea measured at the end of the 6MWT is also submaximal. Thus, in our study, dyspnoea evaluated with multidimensional dyspnoea profile (MDP) questionnaire (sensory components) (data not published) was significantly improved in a similar extent at the end of the 6MWT in the two randomised groups despite an increase in the 6-min walk distance, without significant difference between the two groups. The best test to compare dyspnoea at the same level of exertion would be the cycloergometer endurance test (constant work rate exercise test), because we can measure dyspnoea at isotime and isowork between the beginning and the end of the pulmonary rehabilitation programme [3]. The endurance shuttle walk test allows this measure too, but less data are available.
M. Ekström and colleagues added that “The issue of non-standardised exertion applies also to questionnaires (uni- and multidimensional) of breathlessness during daily life.” It is right but there are dyspnoea scales such as the modified Medical Research Council dyspnoea scale (despite the lack of sensibility of this scale) or London Chest of Activity of Daily Living (LCADL) scale which allow measurement of the impact of dyspnoea on activity of daily of life [4]. Information provided by the LCADL scale could be more informative for the clinician than dyspnoea itself.
About the field test mentioned by M. Ekström and colleagues for measuring exertional dyspnoea, we agree with their comments: the 3-min constant rate step test and 3-min constant rate shuttle walk test have shown responsiveness to changes in dyspnoea from bronchodilation, and are able to measure dyspnoea at the same level of exertion before and after a treatment; however, studies must be realised to show responsiveness to change in dyspnoea after pulmonary rehabilitation.
Lastly, we fully agree with the idea of using MDP questionnaire during standardised exertion to measure dyspnoea. A multicentre study will begin to determine minimal clinical important difference (MCID) for the MDP questionnaire. The LCADL questionnaire would also be used for measuring the impact of dyspnoea during activity of daily living.
Footnotes
Conflict of interest: None declared.
- Received May 1, 2018.
- Accepted May 1, 2018.
- Copyright ©ERS 2018