Cardiodynamic variables measured by impedance cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults

Fang Liu; Raymond C. C. Tsang; Alice Y. M. Jones; Mingchao Zhou; Kaiwen Xue; Miaoling Chen; Yulong Wang

doi:10.1371/journal.pone.0252219

Peer Review History

Original SubmissionMarch 25, 2021
27 Apr 2021 Decision Letter - Shane Patman, Editor PONE-D-21-09792 Cardiodynamic variables measured by Impedance Cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults PLOS ONE Dear Dr. Jones, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. For this initial cycle of the peer review process, it has been fortunate that three experienced reviewers have been able to contribute their time and expertise to considering this submission. On the whole their comments are very supportive of the project to date, with to follow some recommendations to further evolve the reporting of the work to enhance its reporting to the readership. 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Reviewer #1: Yes Reviewer #2: Yes Reviewer #3: I Don't Know ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes Reviewer #3: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes Reviewer #3: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: The manuscript "Cardiodynamic variables measured by Impedance Cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults" is very interesting and of high clinical utility. The design of the study is correct and thoughful, the aim is clear, the results support the conclusions. The disucussion is consisent and balanced. The proposed 6MWT/ICG and elaborated equation for calculation of VO2peak could be used in practice, i.e. for screening exams in young subjects. At first glance simply study effected in really valuable conclusions. I have only minor comments to be cosidered: 1. Introduction, verse 38 "....measured data during a 6MWT will be a stronger predictor of...." - maybe better "....measured data during a 6MWT will produce a stronger predictor of...." 2. Methods, verse 68-70 - the sentence about MasterScreen CPX - please delete here and insert in sentence verse 85-86 in CPET description. Reviewer #2: The present study investigates the use of impedance cardiography during a 6MWT for better predictability of VO2max. In general, the study seems well conducted and the manuscript is clear and easy to read. The authors should be complemented for addressing an important issue in the assessment of physical fitness in the clinical setting. I have only few comments for consideration. Abstract: - Line 10-21: A presentation of the peak values HR, SV, CO in CEPT and 6MWT would contribute to a better understanding of the study in the abstract. The description of the regression analyses could be more concise. Introduction: - Line 32-34: A little more detail is needed regarding the prediction of oxygen consumption due to the 6MWT. Methods: - Line 73: Why were two consecutive 6MWT conducted? Discussion: - Line 318: Measuring VO2 with a portable spirometry during the 6MWT would also be useful. - Also, the feasibility nature of the study should be addressed. The authors have demonstrated the benefits of impedance cardiography in simple clinical examinations. Further investigations (e.g. before and after operations) in various patient cohorts would be useful in the sequel. I recommend considering the manuscript for publication. Reviewer #3: In the manuscript "Cardiodynamic variables measured by Impedance Cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults" authors determine whether prediction of VO2peak can be improved by the inclusion of cardiovascular indices derived by impedance cardiography (ICG) during the 6MWT. This manuscript is correctly written, with the connection between aim, results, discussion and conclusions preserved. In my opinion, it is of significant clinical importance, although it is very limited to the studied age group, without chronic diseases, according to the authors' opinion. Minor comments: 1. While planning training or rehabilitation, it is important to determine the anaerobic threshold. Do you have any data on the level of effort achieved during the 6MWT (line 273-submaximal)? At the end of 6MWT, does the patient get VO2 corresponding to peak VO2 or VO2 at anaerobic threshold (AT) during CPET? Hence, there may be a difference in the strength of the correlation between hemodynamic parameters and VO2 between CPET and 6MWT. The incresases in SV and HR from their values at rest to those at the AT (AT–rest) are similar, but the increase in SV is significantly lower than HR after AT. Moreover, the increase in SV after AT is sensitive to lack of training and chronic diseases. Please complete the discussion on line 260-269. 2. How did you choose values for hemodynamic parameters suitable for analysis? How did you deal with measurement errors? Please complete the methodology - line 103. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: No Reviewer #3: Yes:** Małgorzata Kurpaska, MD, PhD [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0252219.r001
Revision 1
2 May 2021 Author Response We are grateful for all our reviewers’ valuable and insightful comments and have modified our manuscript following their suggestions. Reviewer #1: The manuscript "Cardiodynamic variables measured by Impedance Cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults" is very interesting and of high clinical utility. The design of the s tudy is correct and thoughtful, the aim is clear, the results support the conclusions. The discussion is consistent and balanced. The proposed 6MWT/ICG and elaborated equation for calculation of VO2peak could be used in practice, i.e. for screening exams in young subjects. At first glance simply study effected in really valuable conclusions. I have only minor comments to be considered: 1. Introduction, verse 38 "....measured data during a 6MWT will be a stronger predictor of...." - maybe better "....measured data during a 6MWT will produce a stronger predictor of...." 2. Methods, verse 68-70 - the sentence about MasterScreen CPX - please delete here and insert in sentence verse 85-86 in CPET description. Authors responses: We are grateful for Reviewer 1’s supportive comments. We have replaced ‘be’ with ‘produce’ in the sentence as advised. Please see line 43 under Introduction. We have now moved the description of MasterScreen CPX to the section under CPET, please see line 93. Reviewer #2: The present study investigates the use of impedance cardiography during a 6MWT for better predictability of VO2max. In general, the study seems well conducted and the manuscript is clear and easy to read. The authors should be complemented for addressing an important issue in the assessment of physical fitness in the clinical setting. I have only few comments for consideration. Authors response: We are grateful for Reviewer 2’s encouraging comments Abstract: - Line 10-21: A presentation of the peak values HR, SV, CO in CEPT and 6MWT would contribute to a better understanding of the study in the abstract. The description of the regression analyses could be more concise. Authors response: The peak values of HR, SV, CO in CPET and 6MWT are now included in the Abstract. Units in the equation were removed so the equation now appears more concise. Introduction: - Lines 32-34: A little more detail is needed regarding the prediction of oxygen consumption due to the 6MWT. Authors response: An extra sentence is now included in the Introduction to highlight the relationship between oxygen consumption and ICG cardiodynamic data during 6MWT. Please see lines 36-39. Methods: - Line 73: Why were two consecutive 6MWT conducted? Authors response: the reason for conducting two 6MWTs is now included, please refer to lines 78-81. Discussion: - Line 318: Measuring VO2 with a portable spirometry during the 6MWT would also be useful. Authors response: This is an excellent point. We were aware of the advantage of using a portable telemetric device to measure oxygen consumption during 6MWT. Unfortunately, we did not have the resources to acquire this equipment. This has now been addressed as a limitation. Please see lines 328-331. Also, the feasibility nature of the study should be addressed. The authors have demonstrated the benefits of impedance cardiography in simple clinical examinations. Further investigations (e.g. before and after operations) in various patient cohorts would be useful in the sequel. I recommend considering the manuscript for publication. Authors response: we have now included the feasibility point in the section “Implications of our study’, please refer to lines 319-321. Reviewer #3: In the manuscript "Cardiodynamic variables measured by Impedance Cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults" authors determine whether prediction of VO2peak can be improved by the inclusion of cardiovascular indices derived by impedance cardiography (ICG) during the 6MWT. This manuscript is correctly written, with the connection between aim, results, discussion and conclusions preserved. In my opinion, it is of significant clinical importance, although it is very limited to the studied age group, without chronic diseases, according to the authors' opinion. Authors response: We are thankful for Reviewer 3’s positive comments. We are currently extending our study to include subjects after stroke. Minor comments: 1. While planning training or rehabilitation, it is important to determine the anaerobic threshold. Do you have any data on the level of effort achieved during the 6MWT (line 273-submaximal)? At the end of 6MWT, does the patient get VO2 corresponding to peak VO2 or VO2 at anaerobic threshold (AT) during CPET? Hence, there may be a difference in the strength of the correlation between hemodynamic parameters and VO2 between CPET and 6MWT. The incresases in SV and HR from their values at rest to those at the AT (AT–rest) are similar, but the increase in SV is significantly lower than HR after AT. Moreover, the increase in SV after AT is sensitive to lack of training and chronic diseases. Please complete the discussion on line 260-269. Authors response: Thank you for this excellent comment. Indeed we have collected data on VO2 at anaerobic threshold during CPET. We have reported that the RPE level achieved at the end of CPET was 8/10 and that for 6MWT was 7/10 (line 250) but we did not report our AT data because the correlation between cardiodynamic and VO2peak data was much stronger than correlation with VO2 at AT. As suggested by the reviewer, we now consider that this information would be a nice addition to our report. We have therefore included data recorded at AT in Tables 3 and 4, and in the Results section: lines 182-184, and the Discussion at lines 263-269 and lines 276-277. 2. How did you choose values for hemodynamic parameters suitable for analysis? How did you deal with measurement errors? Please complete the methodology - line 103. Authors response: Thank you for pointing this out. We averaged the final 10 seconds of the ICG data recorded to provide the peak cardiodynamic variables of the 6MWT, and data for CPET were computed similarly. This measurement method was considered reliable as previously reported [9]. We have now included this in the Methodology section, lines 112-114. Attachments Attachment Submitted filename: Responses to reviewers comments.docx https://doi.org/10.1371/journal.pone.0252219.r002
12 May 2021 Decision Letter - Shane Patman, Editor Cardiodynamic variables measured by Impedance Cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults PONE-D-21-09792R1 Dear Dr. Jones, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Shane Patman, PhD Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #2: Yes ****** 4. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #2: (No Response) ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #2: Yes ****** 6. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #2: The authors have made the adjustments requested and I am happy that these changes have improved the article. ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #2: No https://doi.org/10.1371/journal.pone.0252219.r003
Formally Accepted
17 May 2021 Acceptance Letter - Shane Patman, Editor PONE-D-21-09792R1 Cardiodynamic variables measured by Impedance Cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults Dear Dr. Jones: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Assoc Prof Shane Patman Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0252219.r004

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