PONE-D-25-41209Study on Post-Acute COVID-19 Syndrome in Improvement of COVID-19 Rehabilitated Patients by Respiratory TrainingPLOS ONE

Dear Dr. Hsieh,

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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We look forward to receiving your revised manuscript.

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Toufic Ahmad Chaaban, M.D.

Academic Editor

PLOS ONE

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Additional Editor Comments:

This manuscript require significant edits and revisions before deciding on publication. Please address reviewers comments and consider sharing the protocol prior to the study and if it was published

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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: Yes

Reviewer #3: Partly

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

Reviewer #1: No

Reviewer #2: Yes

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: No

Reviewer #2: Yes

Reviewer #3: Yes

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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: Yes

Reviewer #3: Yes

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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: This reports the results of an RCT that compared the efficacy of IS for improving dyspnea and functional status in post COVID 19 patients. Unfortunately, this paper is impossible to read and understand.

-A ton of outcomes are presented - with no distinction about which are the primary outcomes and which are secondary.

-It is unclear how the randomization was carried out.

-The experimental group is stratified by time since infection, but it is unclear whether this was defined a priori or not.

-The analysis compares within changes from baseline to post intervention in each group. What is important is if these changes are different in the experimental arms vs. the control arm. See suggestions below.

1. How exactly was the randomization carried out? Please see the consort checklist and ensure that all the details are given, in one section. Right now these are scattered throughout the manuscript.

2. Why was such a high power used for the sample size calculation? What outcome was the sample size based on? What detectable difference was used? What SD was used? Please justify each choice.

3. Please be specific about the primary outcome. Was this 6MT walk at follow up or was it the change from baseline? OR was it dyspnea?

4. Were the groups defined a priori?

5. Please remove the p value from Table 2. Also standardize the number of decimal places. For the continuous variables present mean (SD). Also - please fix the format - it is impossible to read as is. What does a mean 1.8 for gender mean??

6. The primary analysis should compare the change in 6 minute walk between the intervention groups vs the control group overall. And then, the same thing for dyspnea. Then, use a regression model that includes arm and the group, and the interaction between arm and group - the crucial thing is if the effect of the intervention differs by group.

7. How exactly were the GEE fit? What correlation structure was used? Were robust standard errors used? Table 4 presents group by time interaction - this is a little better - now we can see that some of the groups have different changes than the control group.

8. Table 8 is extraneous, and not part of the objectives. Remove all these results.

9. the discussion says that "Among these, EG1, who underwent the intervention within 3 months of recovery, showed the greatest improvement, with a 79% reduction in D-12 scores." Is this statistically different than the changes observed in the other EGs?

Reviewer #2: This is an excellent article focusing on a highly relevant and common issue currently encountered in pulmonary and medicine clinics.

The study effectively evaluates the use of incentive spirometry as a component of respiratory training to relieve symptoms associated with long COVID. While there are currently no established treatment alternatives proven to resolve long COVID, respiratory training—including techniques like incentive spirometry—has long been utilized in the management of other chronic lung diseases. This approach aims to improve lung function, reduce dyspnea, and enhance overall functional status, suggesting that such interventions may play a valuable role in the multidisciplinary management of post-COVID patients

The study features an innovative approach by employing multiple experimental groups alongside a control group. These groups are evaluated longitudinally, according to the duration elapsed since recovery from COVID-19. This design allows for assessment of intervention effectiveness over time, providing valuable insights into how respiratory training may impact functional recovery and symptom resolution in the post-COVID population.

A key strength of the study lies in the intervention's simplicity, which is easy to implement and associated with limited to no immediate perceived harm to the patient. Moreover, the fact that incentive spirometry can be self-performed by patients adds to its practicality and feasibility, making it an attractive option for managing long COVID symptoms in the outpatient setting. The sample size for this study was appropriately calculated using statistical methods, including repeated measures one-way ANOVA. The investigators also accounted for a potential 10% dropout rate by enrolling an adequate number of additional participants. This approach enhances the robustness of the findings and ensures that sufficient data would be available for meaningful analysis despite potential attrition.

The diagnosis of long COVID is a complex and nuanced topic that warrants discussion on its own. Unlike many other conditions, long COVID remains primarily a diagnosis of exclusion, as there is currently no definitive imaging or blood-based test to confirm its presence. Clinicians must therefore rely on clinical evaluation, history, and the persistence of characteristic symptoms beyond the acute phase of infection, while actively ruling out alternative explanations. This diagnostic uncertainty presents a significant challenge in both research and clinical practice.

A significant limitation of the study is its lack of consideration for the inherent severity or risk posed by pre-existing cardiopulmonary disease. For example, the study does not account for whether participants’ initial COVID-19 illness was complicated by respiratory failure, myocarditis, hypoxemic respiratory failure, or pulmonary embolism. Instead, it includes individuals who have recovered from COVID-19 within the past year, without stratifying them according to the severity or type of their prior cardiopulmonary involvement. A mean 6-minute walk distance of 347 meters indicates that the study group consisted of a relatively healthy population with moderate baseline functional capacity. This may limit the applicability of the findings to individuals with more severe impairment or lower exercise tolerance. Subjective performance in interventions such as respiratory training may vary significantly with age, as younger patients often tolerate these exercises better than older individuals. There is no age-based stratified analysis to address these potential differences. Furthermore, the study does not fully account for underlying health risk factors such as pre-existing cardiopulmonary disease and environmental exposures, including urban air pollution. Although hypertension and cardiovascular disease were the most reported underlying medical conditions among participants, it remains uncertain whether individuals with chronic lung diseases were excluded. These factors could substantially influence both baseline functional status and response to intervention, and their omission may limit the generalizability of the study’s findings. The study comments on baseline exercise tolerance, noting that 40% of participants did not engage in regular physical activity. However, it is unclear whether this lack of activity reflects participants’ habits prior to their COVID-19 episode or is a consequence of their illness and recovery. This ambiguity makes it difficult to interpret the impact of the intervention on overall exercise capacity and recovery trajectories. Although participants of the study have at least 1 or 2 episodes of covid infection, the study does not address whether outcomes differed between individuals with repeated COVID-19 infections compared to those who experienced a single episode. This information is not provided, leaving uncertainty about whether recurrent infection may impact functional recovery or response to respiratory training in long COVID patients. Injectable antivirals were only used in 3 out of 85 participants (4% of study population). so, I would expect the participants to have a lower acuity of covid infection at base line. What is the difference among those who were treated with the medications vs no medication group (28 of 85)

Despite robust sample calculation several subgroups had a limited number of patients; detailed interpretation in some of the subgroup analyses was extremely limited.

The effect of the Chinese medicine formula on the results is not clearly addressed in the study. It is unclear whether a separate analysis was conducted for patients who did not receive the Chinese medicine formula, which raises concerns about the generalizability of the findings—particularly to populations that do not use traditional Chinese medicine. Additionally, the possible interaction between the Chinese medicine formula and the intervention being studied (such as respiratory training) remains uncertain. Without subgroup analysis, it is difficult to determine whether the observed improvements in recovery are attributable to the respiratory intervention itself, the Chinese medicine formula, or a combination of both. This limitation should be considered when interpreting the applicability of the study to broader patient populations

Quality control in the study was addressed by having a nurse perform the initial training for participants. However, subsequent performance of the intervention relied on patient self-reporting, which introduces the potential for variation in both execution and documentation of the exercise. While telephone follow-up calls were used to assess compliance, a video call could have provided a more objective assessment, allowing direct observation of patient technique without the confounding factor of patients talking during incentive spirometry sessions. Employing video-based monitoring might enhance the accuracy and consistency of performance evaluation in future studies.

The study mentions regular telephone follow-ups; however, it does not specify the exact frequency of these calls. Further clarification regarding the timing and intervals of follow-up contacts would be useful to assess the consistency of monitoring and its potential impact on patient compliance and outcomes.

There appears to be some lack of clarity regarding the final number of participants included in the analysis. The study notes that five patients were lost to follow-up, and an additional three participants, who only completed the questionnaire assessments, were excluded from the final analysis. Based on these exclusions, the total analysis group was stated as 85; however, by calculation, one might expect the final number to be 82. Clarifying the exact criteria for inclusion and ensuring consistency in reporting participant numbers is important for accurate interpretation of study results.

Smoking prevalence in Taiwan, where this study was conducted, is low at around 13% overall. This aligns with the study population, in which female smoking prevalence is reported at only 2% and male smoking at 23%. These rates reflect national averages and provide important context for interpreting study outcomes, especially when considering risk factors commonly associated with cardiopulmonary health.

In table 2

When we look at the average duration of post recovery. For experimental Group 2 it is mentioned that the average duration of post recovery is only 1.2 months, I am not sure. If this is represented adequately as experimental, group 2 should be Three to six months. It is unclear why there are numbers in the row beside Hypertension in the mean and SD, I do not think we need this is necessary for categorical variables

Based on the PCFS score, there are significant differences that are noted in the Experimental Groups. It indicates that the study population is a healthier population, and the underlying COVID infection was less severe. Without any long-term Needs for supplemental oxygen. So, I would expect that the patients would not have any diseases like COVID-induced ILD.

There is a paragraph repetition between lines 110 and 120 and this could be corrected.

Reviewer #3: I appreciate the authors' commitment to rigorously evaluating a low-cost strategy for managing Long COVID syndrome, especially given the crucial need for accessible interventions in low and middle-income countries.

However, I have a significant methodological concern regarding the composition of the standard care arm and its relationship to the intervention being tested.

My concern is two-fold:

1. Exclusion of Pulmonary Rehabilitation:

Pulmonary rehabilitation is widely recognized and increasingly accepted as a cornerstone of management for persistent respiratory and functional impairment in Long COVID. Excluding it as a component of standard care for both the control and intervention groups may create a potential ethical and scientific deficit by not providing the currently accepted optimal care to the participants.

2. Role of Incentive Spirometry:

I believe that both groups should have received a structured pulmonary rehabilitation program. The authors' chosen low-cost intervention, such as incentive spirometry, should have been evaluated as an additive or specific, targeted component in addition to comprehensive pulmonary rehabilitation, rather than a potential replacement for it.

I would appreciate a strong justification from the authors for this trial design choice, particularly on why they elected to avoid including pulmonary rehabilitation in the standard care protocol, which is critical for fully assessing the incremental benefit of their low-cost strategy.

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Reviewer #1: No

Reviewer #2: Yes: Madhu Kalyan Pendurthi

Reviewer #3: Yes: Dapanaduwage Amila Vindana Rathnapala

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PONE-D-25-41209R1Study on Post-Acute COVID-19 Syndrome in Improvement of COVID-19 Rehabilitated Patients by Respiratory TrainingPLOS One

Dear Dr. Hsieh,

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 address some residual minor comments related to structuring and results presentation

Please submit your revised manuscript by Mar 14 2026 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 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,

Toufic Ahmad Chaaban, M.D.

Academic Editor

PLOS One

Journal Requirements:

If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise.

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.

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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 #1: (No Response)

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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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 #1: No

Reviewer #2: Yes

Reviewer #3: Yes

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

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: N/A

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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 #1: No

Reviewer #2: Yes

Reviewer #3: Yes

**********

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 #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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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 #1: The paper is more understandable now.

1. Why wasn't the control group stratified on the basis of long covid? How long had the control group been suffering from long covid? How could this have affected the results?

2. The tables are now in separate documents - this is hard to review.

4. Table 4-7 - these tables are very hard to understand, and interpret. But I am happy to see the p for interaction. Can you please instead integrate the p for interaction into Table 3.

5. Also - re-arrange table 3 into Primary and Secondary outcomes.

6. Please integrate the sample size information into the main manuscript. I cannot replicate the sample size calculation - thus more details are needed. With two groups you would need a much larger sample size - I am not clear how you get to 90 total subjects.

7. the discussion says that "Among these, EG1, who underwent the intervention within 3 months of recovery, showed the greatest improvement, with a 79% reduction in D-12 scores." Is this statistically different than the changes observed in the other EGs? Your reply did not address my question.

8. The discussion emphasizes the wrong thing. The first paragraph should talk about whether D-12 change from baseline to follow up was different in the control group to the intervention group.  Within group différences could have occurrence due to usual improvement of symptoms over time.

9. The second paragraph of discussion: " Moreover, many participants reported noticeable relief from dyspnea within 3 weeks of initiating IS training, along with enhanced subjective comfort and adherence." Where are these results presented? Similarly for results pertaining to the inspiratory ball count?

10. The interpretations of the effects in lines 357-389 should emphasize the difference of differences vs the control group.

11. Everywhere - the order of results should first describe the primary results.

12. For the between group differences - should these be adjusted for relevant confounders since the EG groups are not randomized?

13. lines 339-40 "indicating that participants in EGs improved their functional status to a comparable functional level as the CG." This is an incorrect interpretation. An equivalence test would need to be conducted to make this statement.

Reviewer #2: Replies from the authors suffice the questions raised in the review. I appreciate your effort in revising several key areas of the draft.

Reviewer #3: I have reviewed the revised manuscript and the authors' response to my previous concerns regarding the study design and the standard of care provided to the control group. I appreciate the authors' thorough engagement with these points.

1. Regarding the Standard Care Arm and Pulmonary Rehabilitation: I accept the authors' explanation that at the time of the study, a standardized pulmonary rehabilitation program for Long COVID was not routinely available in clinical practice in Taiwan. This context satisfactorily justifies why pulmonary rehabilitation could not be included as the "standard of care" for the control group. It resolves the ethical and scientific concern regarding the withholding of optimal care, as the study design reflected the real-world clinical reality of that specific period and region.

2. Regarding the Role of Incentive Spirometry (IS): I commend the authors for revising the Introduction to clarify the positioning of the intervention. The added text explicitly states that "although IS cannot replace pulmonary rehabilitation, it may serve as a low-cost, self-administered intervention option... to address existing gaps". This successfully shifts the framing of the study from proposing IS as a substitute for comprehensive rehab to evaluating it as a feasible, accessible alternative for resource-limited settings.

General Observations: The inclusion of Generalized Estimating Equations (GEE) analysis and the expanded Limitations section—addressing comorbidities and pre-existing conditions —have significantly strengthened the rigor of the manuscript. The revisions have adequately addressed my methodological concerns.

I have no further comments and recommend the manuscript for publication.

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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 #1: No

Reviewer #2: Yes: Madhu Kalyan Pendurthi

Reviewer #3: Yes: Dapanaduwage Amila Vindana Rathnapala

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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.]

To ensure your figures meet our technical requirements, please review our figure guidelines: https://journals.plos.org/plosone/s/figures

You may also use PLOS’s free figure tool, NAAS, to help you prepare publication quality figures: https://journals.plos.org/plosone/s/figures#loc-tools-for-figure-preparation.

NAAS will assess whether your figures meet our technical requirements by comparing each figure against our figure specifications.

PONE-D-25-41209R2Study on Post-Acute COVID-19 Syndrome in Improvement of COVID-19 Rehabilitated Patients by Respiratory TrainingPLOS One

Dear Dr. Hsieh,

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.

==============================

ACADEMIC EDITOR: please make corrections according to reviewers' comments or write a detailed rebuttal on a point-by-point basis.

==============================

Please submit your revised manuscript by May 25 2026 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 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.

As the corresponding author, your ORCID iD is verified in the submission system and will appear in the published article. PLOS supports the use of ORCID, and we encourage all coauthors to register for an ORCID iD and use it as well. Please encourage your coauthors to verify their ORCID iD within the submission system before final acceptance, as unverified ORCID iDs will not appear in the published article. Only  the individual author can complete the verification step; PLOS staff cannot  verify ORCID iDs on behalf of authors.

We look forward to receiving your revised manuscript.

Kind regards,

Davor Plavec, MD, MSc, PhD, Prof.

Academic Editor

PLOS One

Journal Requirements:

If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise.

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:

Dear Authors,

please make corrections according to reviewers' comments or write a detailed rebuttal on a point-by-point basis.

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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 #1: (No Response)

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

Reviewer #4: (No Response)

**********

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 #1: Partly

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

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

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: N/A

Reviewer #4: I Don't Know

**********

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 #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

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 #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: 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 #1: 1. Table 3 remove the t-value from the table.

2. Table 4; Present only the beta and a 95% CI. Remove Se, Wald chi square, df and p value.

3. table 4 is described as interaction effects between group and time. Are you sure that is what you are presenting here? Please write out the model and show which parameters are included in the table.

4. How were the subjects who dropped out handled? If these are excluded then this is not an intention to treat analysis and this should be acknowledged as a potential source of bias.

5. Please also acknowledge as a limitation the very small size of the control group, which was not stratified by length of long COVID.

Reviewer #2: (No Response)

Reviewer #3: The authors have thoroughly and satisfactorily addressed my previous concerns regarding the study design and the intervention's clinical role.

Specifically, the authors provided crucial context regarding the lack of standardized pulmonary rehabilitation programs in the study's region during the data collection period. This adequately justifies the composition of the standard care control arm and resolves my ethical and methodological concerns. Furthermore, the revised Introduction accurately positions Incentive Spirometry not as a replacement for comprehensive pulmonary rehabilitation, but as a practical, low-cost, and accessible adjunct for resource-limited settings.

These clarifications significantly strengthen the manuscript's clinical relevance and scientific integrity. I have no further concerns and recommend the manuscript for publication.

Reviewer #4: Dear colleagues, thank you for giving me the opportunity to review your article. Basically, the article is of interest in the sense of post-covid rehabilitation possibilities. I had not the opportunity to review previous versions, but this version is much improved. I would have some minor suggestions to even more improve your article:

1. “Study on Post-Acute COVID-19 Syndrome in Improvement of 2 COVID-19 Rehabilitated Patients by Respiratory Training.”

The article title can be misleading and not informative enough what the article is about so I would suggest you to rephrase it.

2. “Currently, no definitive treatment for Long COVID.”

This is not a valid sentence, correct it.

3. “Respiratory training—commonly used to manage symptoms in chronic pulmonary disease—is considered a potentially beneficial intervention for Long COVID; however, supporting evidence remains limited.”

This is not truth, evidence exist so please rephrase this sentence and add new references. That should be corrected throughout the article.

4. “provides patients with an alternative choice”

No truth because it was not compared with pulmonary rehabilitation. You should omit this sentence.

5. “Participants were randomly assigned to groups based on recovery duration.”

If they were assigned by recovery duration what was random? The later explanation in the article is correct, but this sentence is not.

6. “The flow diagram of participant enrollment and allocation in figure 1.”

Incorrect sentence, please correct it.

Best regards

**********

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.

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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: Yes: Madhu Kalyan Pendurthi

Reviewer #3: Yes: Dapanaduwage Amila Vindana Rathnapala

Reviewer #4: No

**********

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You may also use PLOS’s free figure tool, NAAS, to help you prepare publication quality figures: https://journals.plos.org/plosone/s/figures#loc-tools-for-figure-preparation.

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PONE-D-25-41209R3Effects of Incentive Spirometer Training on Dyspnea and Functional Status in Patients with Long COVIDPLOS One

Dear Dr. Hsieh,

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.

==============================

ACADEMIC EDITOR: Dear Authors, please make suggested revisions according to reviewers' comments or write a detailed rebuttal on a point-by-point basis.

==============================

Please submit your revised manuscript by Jul 02 2026 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.

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We look forward to receiving your revised manuscript.

Kind regards,

Davor Plavec, MD, MSc, PhD, Prof.

Academic Editor

PLOS One

Journal Requirements:

If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise.

Additional Editor Comments:

Dear Authors,

please make suggested revisions according to reviewers' comments or write a detailed rebuttal on a point-by-point basis.

[Note: HTML markup is below. Please do not edit.]

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 #1: (No Response)

Reviewer #3: All comments have been addressed

Reviewer #4: (No Response)

**********

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 #1: Yes

Reviewer #3: Partly

Reviewer #4: No

**********

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

Reviewer #1: I Don't Know

Reviewer #3: N/A

Reviewer #4: I Don't Know

**********

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 #1: No

Reviewer #3: Yes

Reviewer #4: Yes

**********

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 #1: Yes

Reviewer #3: Yes

Reviewer #4: 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 #1: Thank you for the revisions.

I think there is a problem with the values for the PCFS interaction terms presented in Table 4. These do not seem to line up with what would be expected given the results presented in Table3. Please verify.

The other values presented are close to what is presented in Table 3.

Reviewer #3: The authors have successfully maintained the crucial clarifications requested in the previous review rounds, effectively resolving my primary methodological and ethical concerns.

Specifically, the manuscript correctly contextualizes the control arm by acknowledging the absence of standardized pulmonary rehabilitation programs during the study period. This provides a solid ethical and scientific justification for the study design based on the clinical reality of the time.

Furthermore, the authors have appropriately defined the role of Incentive Spirometry. By framing it as a practical, self-administered adjunct rather than a replacement for comprehensive pulmonary rehabilitation, the study offers a highly relevant, low-cost option. This distinction is particularly valuable for optimizing respiratory care in resource-limited settings where formal, multidisciplinary rehabilitation programs may be inaccessible to patients.

The revisions have significantly strengthened the manuscript's clinical applicability and scientific integrity. The authors have adequately addressed all of my feedback, and I have no further concerns. I recommend this article for publication.

Reviewer #4: Dear colleagues,

Thank you for giving me the opportunity to review your article. This is an interesting idea but unfortunately, I don’t believe that you have scientifically proof your conclusion: “In conclusion, IS represents an effective and practical strategy for alleviating dyspnea and improving functional limitations in individuals with Long COVID.“

The design of your study has many limitations as you have correctly stated in the limitations section but there is also one big limitation and you have not mentioned it. The lung function analysis of the patients with CO diffusion capacity which is known to be the important parameter considering the exercise limitation in post-COVID patients. From my point of view, no studies of post-COVID respiratory investigations should be done or at least published without the DLco data. Also, the intervention itself could have important placebo effect that was not possible to exclude by the study design.

If you can correct for previously stated problems, I would be glad to re-review your article.

Best regards

**********

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 #1: No

Reviewer #3: Yes: Dapanaduwage Amila Vindana Rathnapala

Reviewer #4: No

**********

[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.]

To ensure your figures meet our technical requirements, please review our figure guidelines: https://journals.plos.org/plosone/s/figures

You may also use PLOS’s free figure tool, NAAS, to help you prepare publication quality figures: https://journals.plos.org/plosone/s/figures#loc-tools-for-figure-preparation.

NAAS will assess whether your figures meet our technical requirements by comparing each figure against our figure specifications.

Effects of Incentive Spirometer Training on Dyspnea and Functional Status in Patients with Long COVID

PONE-D-25-41209R4

Dear Dr. Hsieh,

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. For questions related to billing, please contact billing support.

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,

Davor Plavec, MD, MSc, PhD, Prof.

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 #1: 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 #1: Yes

**********

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

Reviewer #1: 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 #1: Yes

**********

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 #1: 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 #1: (No Response)

**********

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 #1: No

**********