ABSTRACT
We are grateful to Ulasli and Esquinas for their comments to our paper.. They argued that arterial blood gas analyses were not performed without oxygen prior to the 6-minute walk test with noninvasive ventilation (6MWT-NPPV). This point has already been discussed in our original work by indicating the limitations of our study. The reason for using oxygen prior to exercise testing was to guarantee comparable starting conditions.
KEYWORDS:
We agree with Ulasli and Esquinas that further studies investigating NPPV during exercise in COPD patients should consider the presence or absence of cor pulmonale and cardiovascular diseases. We can also not exclude with certainty that patients in our current trial and in our previous trials were completely comparable Citation(1–3). However, inclusion criteria were similar and patients characteristics, especially lung function parameters, were comparable in all the three studies Citation(1–3).
Another concern of Ulasli and Esquinas was a potential learning effect related to test repetition and practice during the 6MWT. They refer to a recent review of the European Respiratory Society/American Thoracic Society stating that “consideration should be given to performing two 6MWTs” Citation(4). Again, all patients were familiarized with 6MWT, since it is performed on a routine basis during control visits in our hospital. In order to prevent misinterpretation of the results caused by a potential learning effect, the order of 6MWTs in the current study was randomized Citation(1). As stated, 6MWTs were performed according to the available guidelines at the time the study was conducted Citation(5).
Finally, all subjects were patients from the Department of Pneumology at the University Hospital Freiburg, Germany. Optimal treatment regarding pulmonary and cardiovascular medications was adjusted according to the current guidelines Citation(6). Medication dose and time of application did not differ between the two study days.
Acknowledgments
We are grateful to Ulasli and Esquinas for their comments to our paper. They argued that arterial blood gas analyses were not performed without oxygen prior to the 6-minute walk test with noninvasive ventilation (6MWT-NPPV). This point has already been discussed in our original work by indicating the limitations of our study. The reason for using oxygen prior to exercise testing was to guarantee comparable starting conditions.
Declaration of interest
David J. Walker received travel funding for national and international research conferences by Vivisol and Sapio Life.
References
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