PONE-D-24-08655Effect of caffeine citrate on diaphragmatic electrical activity in pre-term newbornsPLOS ONE

Dear Dr. Zidan,

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.

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PLOS ONE

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Additional Editor Comments:

Dear writer,

Although the subject of the study is interesting, it will be re-evaluated if you respond adequately to the reviewer criticisms. You are expected to provide adequate explanations, especially regarding the availability of data and financial matters.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. 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 #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: I Don't Know

Reviewer #3: Yes

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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: No

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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: No

Reviewer #3: No

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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: I congratulate the authors on conducting a "basic science” research; it is indeed essential to demonstrate clinically the pharmacological effects of commonly used drugs. I do have some suggestions

1, The fact that the sample size is a convenience sample makes it less powerful - it needs to be highlighted. I wonder why the authors could not have planned a presumed difference in findings before and after caffeine for a single primary outcome and calculation could have ben done. it would have increased the power of the study

2. where does the funding for the Edi probe (NAVA) probe come from when it is used for spontaneously breathing / those who did not require any supports? I am curious to know

3. The figures 1,2 are quite redundant-either the study flow diagram can be expanded to include the primary outcome or the figure can be dropped as such

the figure 2 also does not add any corroborative information to the methodology

4. Please explain why the signals could not be have been measured and recorded for analysis for a longer duration (like midway between 2 doses ) or when the trough level is expected (before the next scheduled dose)?

the probe should have been in situ or was it removed every time after measurement at 60 min post dose?

5. Table 1 can be better formatted- the max and min need not have a separate column only for 2 variables

6. Other details of the respiratory support like how many days of CPAP/NIV/IMV would have more relevance than the proportion of neonates needing each alone

also clinically relevant outcomes like BPD- to know the sickness levels of the babies- effect of caffeine and diaphragmatic activity would depend on secondary causes of apnea too.

Reviewer #2: In this study by Brasil Zidan et. al. evaluates the effect of a single dose of caffeine citrate on the electrical activity of the diafragm muscle. Authors show a relation between the EDI parameters before and after the first dose of caffeine citrate and conclude that caffeine in preterm infants promotes electrical activity of the diaphragm 60-120min after the first loading dose.

The design of the study is valid, yet minimalistic. As such it adds to our current understanding of the effects of caffeine on the electrical activity of the diafraghm. However, I have several remarks regarding the manuscript I would like to mention.

1. There are paragraphs of text that are duplicated in the text, as well as spelling errors (e.g. diaphrgm in the keywords)

2. The data is fully available on Google Drive. I would have like more information how this would be accesible.

3. The abstract line 37-39 is a very general statement about significance. What I would like to read is what the clinical effect is, not just if it is significant.

4. Abstract line 41, you mention 60-120 minutes after loading dose, but measurements were taken until 60min after the loading dose? (line 78) I believe it has something to do with the start of the recording (line 144), but it is confusing.

5. The authors mention the beneficial effect of caffeine and the fact that it increases diaphragmatic electrical activity (lines 65, reference 12). In line 76 the authors mention other studies investigating the electrical activity, I presume reference 12 should be added to the list as well? Taken together this study does not add significant new data to the already existing amount of data regarding electrical activity after caffeine. It would certainly strengthen the study design to include a much larger group of participants who are (especially) followed for a longer duration. As authors rightfully mention the the discussion. This would really expend the current knowledge about caffeine.

6. One of my main concerns is the patient groups. It includes many patients on mechanical ventilation, who are often sedated. Also how does one detect apnea's when on mechanical ventilation? As usually there is a set backup breathing frequency? Also many patients are included very early on after birth, where as many patients will develop apneu's within the first days after birth when spontaniously breathing. Suggesting a selection bias in this cohort.

7. Why are patient with HFO ventilation excluded?

8. statistics are mostly based on normality as is suggested by the representation as mean +- SD. In these small populations I think that a non-normal distribution is perhaps a better choice?

9. Line 192: sample calculation was not performed in my opinion, authors did use "sampling based on convenience" or "convenience sampling".

10. Line 257: I am unsure what the relationship is between de EDI values and the statement in this line. "These data" suggest that the EDI data is important for this statement, which it is not.

11. Paragraph from line 292 misses a conclusion of how these results should be interpreted in light of the current evidence.

12. Line 298, this section should also adress the question whether serum caffeine levels correlate with the clinical effect of caffeine, known in literature.

13. Line 309, in this section authors discuss the negative effect of mechanical ventilation on diaphragm function. This conclusion leads to a limition of this study (the fact that many patients were on MV) which should be discussed.

Minor:

line 214 missed dot.

line 259 the use of "methylxantines" is the first mentioning of this synonym for caffeine, it is confusing to start using at this point in the article.

Line 263: spelling error funtion

Line 266: I would like to know why this is beneficial?

In conclusion this study would greatly benefit from extensive editing and correction. It woulf further benefit from not only the electrical data but the subsequent effect on clinical parameters, which is a serious deficit in this study.

Reviewer #3: I would like to thank PLOS ONE for giving me the opportunity to review this interesting manuscript. By investigating the effect of a loading dose of caffeine citrate on diaphragmatic activity and neural respiratory rate in preterm neonates, the authors picked up an important topic for clinical neonatology. Based on the criteria for publication in PLOS ONE, here are my conclusions:

- The study definitively presents the results of primary scientific research.

- The presented results have not been published elsewhere.

- From my point of view, experiments and statistics were performed to a high technical standard and are described in sufficient detail.

- Conclusions are presented in appropriate fashion and are supported by the data provided.

- In general, the manuscript is presented in an intelligible fashion, using appropriate English. However, it would benefit from additional editing and I have summarized some corrections in my comments below.

- I have one issue regarding the required “research integrity”, and this is the registration in a clinical trials registry. I am actually worried that the authors state that they are still waiting for approval from the Brazilian Registry of Clinical Trials, although they are presenting a finished study which was performed from 2018 to 2019! Usually a clinical study should be registered before it is being performed, and it worries me that the authors obviously did not wait for the study registration to be completed. In addition, the authors state in their ethical considerations section that they did not aim for registration in a clinical trials system due to the observational character of the study, which by the way is no reason not to register (see https://clinicaltrials.gov/about-site/about-ctg#q2) – this makes me wonder even more why approval from the Brazilian Registry of Clinical Trials was ultimately sought?

- Regarding required data availability: The statement “Data is avaiable on Google Drive” does not specifically tell how to access data– please add a link or equal, unless you decided to do so after acceptance of the manuscript.

- Regarding adherence to appropriate reporting guidelines: I strongly encourage the authors to add a STROBE statement (https://www.equator-network.org/reporting-guidelines/strobe/) to their submission.

Furthermore, I have the following recommendations:

1) Abstract, lines 34-35: The presented numbers of females and males does not add up to 36. Furthermore, the patient numbers provided differ from the ones presented in the results section. Please correct this diligently!

2) I suggest chancing the manuscript’s short title to “Caffeine citrate and diaphragmatic electrical activity”, as this probably makes more sense.

3) Abstract, lines 36-37: I suggest adding the information when caffeine citrate levels were obtained.

4) Inclusion criteria, page 6, line 120: Please change “SMIV” to “SIMV”.

5) Evaluation of the electrical activity of the diaphragm, page 6, line 135: Please put “Maquet, Getinge Group, Solna, Sweden” in brackets or add “by” before this information.

6) Fig. 4, page 8, line 174: Please change “Minimun” to “Minimum”.

7) Results, pages 10-11: Please be consistent and present data with decimal numbers using a dot instead of a comma.

8) Results, page 11, lines 234-237: Please be consistent with the use of abbreviations – some, such as “MinIEdi”, “MaxIEdi” and “MinEEdi”, are introduced here, although these terms have been used before in the manuscript. This makes it difficult for the reader to follow the text.

9) Results, page 11, line 241 and Table 2: What does “mpm” stand for? I am not familiar with this abbreviation.

10) Discussion, page 12, line 261: I suggest changing “stimulate” to “stimulates”; otherwise, one could get the impression that adenosine stimulates central respiratory centers.

11) Discussion, page 13, lines 287-291: This paragraph is identical with the one at the top of the next page – please remove it.

12) Discussion, page 13, lines 296-297: I disagree with this sentence, as the authors only found a reduction in absolute numbers of respiratory pauses, which, however, was not statistically significant.

13) The reference list uses different styles of referencing, which should be harmonized using one standard referencing style. Furthermore, I have recognized several mistakes in writing, e.g. for reference 5 “Jonhson … Neo- natal …”, which also need careful correction.

14) References, page 17: Reference number 19 should actually be number 20 – please correct this.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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<div>PONE-D-24-08655R1Effect of caffeine citrate on diaphragmatic electrical activity in pre-term newbornsPLOS ONE

Dear Dr. Zidan,

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.

Please submit your revised manuscript by Jan 16 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols .

We look forward to receiving your revised manuscript.

Kind regards,

Hakan Aylanc

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

Additional Editor Comments:

Although the improvements have been made are appropriate, in addition to the criticisms of the reviewer, I would like to make the following suggestions.

1. Spelling mistakes should be corrected with the support of a native English-speaking advisor.

2. There should be harmony between the abstract and the tables in the article, spelling mistakes should be corrected

3. 68% increase in peak inspiratory Edi”, according to Table 1, the maximum inspiratory Edi increased from 10.35 to 12.17, which corresponds to an increase of only 17.6%. Please explain.

4. The reference list should be corrected according to the spelling rules.

5. It is indicated that it was approved by the ethics committee. The full name of the ethics committee and the approval number, if available, should be included.

6. In lines 245,246, the conclusion of the study alone gives classical information and it would be good to combine the sentence with the sentence in 247 and 248.

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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 #3: (No Response)

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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 #3: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: 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 #3: Yes

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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 #3: No

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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 #3: The authors have answered and addressed many of the questions and issues that arose during the first round of reviews, and I would like to thank them for their effort to improve their manuscript.

My main concern was the fact that approval from the Brazilian Registry of Clinical Trials was sought, but obviously not obtained. The argument that registration with ClinicalTrials.gov was not performed because “it was not an interventional study” is not valid, because ClinicalTrials.gov explicitly invites observational studies “in which researchers simply collect information”. Therefore, I am interested what the answer from the Brazilian Registry of Clinical Trials actually was?

While many of the implemented changes have helped improving the presentation of the manuscript, there are still some changes and improvements required:

1) Introduction, page 3, line 52: Please be consistent when using abbreviations such as AOP.

2) Patient population, page 6, line 115: Please change “pacients” to “patients”.

3) Table 1: There are differences in the presented mean birth weight between the abstract and the table – please check this carefully and correct it appropriately.

4) Results, page 10, line 221: I suggest changing “age of data collection” to “age at data collection”.

5) Table 2 and throughout: Please be consistent with the use of dots instead of commas for decimal numbers.

6) Discussion, page 12, line 245: Please change “demonstreted” to “demonstrated”.

7) Discussion, page 13, line 280: Where does the “68% increase in inspiratory peak Edi” come from? According to Table 1, the maximum inspiratory Edi increased from 10.35 to 12.17, which only corresponds to an increase of 17.6%. Please explain.

8) Discussion, page 13, lines 291-292: I suggest changing “… in the same moment that other routine testes of newborns” to “… together with other routine blood tests”.

9) Discussion, page 14, lines 294-295: The information about “without increasing the risk of neurodevelopmental disabilities” seems not relevant here and could be omitted.

10) Discussion, page 14, line 308: Please change “ventialtion” to “ventilation”.

11) The reference list has still not been comprehensively revised and corrected, e.g. for reference 5 “Jonhson” is still incorrect. Furthermore, there are still different styles of referencing used, such as in references 28 and 31.

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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 #3: No

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[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.

Effect of caffeine citrate on diaphragmatic electrical activity in pre-term newborns

PONE-D-24-08655R2

Dear Dr. Zidan,

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 will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager®  and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, 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,

Hakan Aylanc

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments: