To the Editor:
We have read with great interest the article by Corbellini et al,1 “Diaphragmatic Mobility Loss in Subjects With Moderate to Very Severe COPD May Improve After In-Patient Pulmonary Rehabilitation.” This article provides relevant information regarding diaphragm mobility measured with M-mode ultrasonography in healthy subjects and subjects with COPD. Additionally, the article verified the effect of pulmonary rehabilitation on diaphragm mobility and lung function in subjects with COPD. Nevertheless, we found some inconsistencies in the data presentation, and some information was not sufficiently explained to understand the study fully.
The main problem refers to the fourth paragraph of the results section (page 6) and the corresponding Figures 3–5 (page 8) and their titles. As an example, in the main text, we read that the percent of predicted FEV1 negatively correlates with diaphragm mobility during breathing at rest and positively correlates with diaphragm mobility during deep inspiration; however, Figure 3 and its title suggest the reverse relationship. A similar lack of consistency is seen between the last sentence of the fourth paragraph and Figure 5 and its title. In turn, Figure 4 presents 2 positive relationships, whereas the title of Figure 4 suggests a negative correlation.
The second problem is a lack of information regarding which subjects were used to calculate the correlations. Initially, there were 46 subjects with COPD and 16 healthy subjects, but only 30 subjects with COPD completed the full protocol. In the results section, it states that the correlation analysis was performed on 45 subjects. Who were these 45 subjects? Were they the subjects with COPD from the baseline assessment or 30 subjects with COPD and 15 healthy subjects (or 16, with 1 subject lost in the analysis)? The abstract of the study suggests that ultrasound measurements were performed on 52 subjects with COPD, whereas in the main text the data are based on 46 subjects with COPD. This is confusing for readers. Additionally, the study protocol (NCT02838953) registered on ClinicalTrials.gov suggests an enrollment of 56 subjects.
The third problem refers to the sentence on page 7, “our study identified an inverse correlation between diaphragmatic mobility during deep inspiration and COPD severity,” and the last sentence in the abstract, “These changes were correlated with COPD severity . . . .” In the methods section, it was stated that COPD severity was classified based on GOLD criteria (http://goldcopd.org. Accessed December 11, 2020), but the exact correlation between COPD severity and diaphragmatic mobility was not presented in the study.
In conclusion, the study by Corbellini et al1 presents promising results on the use of M-mode ultrasonography to assess altered diaphragmatic function in patients with COPD and confirms the effects of pulmonary rehabilitation on lung function and diaphragm mobility. Nevertheless, more attention to detail is necessary to provide consistent results and information on the examined population. Otherwise, the study is not useful for readers. We suggest a correction is necessary to resolve the ambiguities that we have pointed out. This update may help other readers use the study by Corbellini et al1 as a source of reliable information.
Footnotes
- Correspondence: Linek Pawel PhD, Institute of Physiotherapy and Health Sciences, Musculo-skeletal Elastography and Ultrasonography Laboratory, The Jerzy Kukuczka Academy of Physical Education, 40–065, Mikolowska 72A, Poland. E-mail: linek.fizjoterapia{at}vp.pl
The authors have disclosed no conflicts of interest.
- Copyright © 2021 by Daedalus Enterprises
Reference
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