Factors Influencing Abdominal Compliance during CO₂ Insufflation in Patients Undergoing Laparoscopic Abdominal Surgery

                                                                                                                    June 17th, 2024    

Dear editorial team,

We are very grateful to you for taking the time to review our paper. We appreciate your comments and contributions, which have helped us to improve our work. Please find below our detailed responses to your feedback, as well as the relevant revisions and corrections in the resubmitted manuscript. We have also made revisions to the introduction, results and conclusion sections of the study based on the feedback of both reviewers. We have made further improvements to the visual appearance of the manuscript by adding histogram plots. We have also corrected a minor error in our terminology and removed a reference containing a different definition of 'compliance' from the manuscript after the feedback. We would like to thank our reviewers once again for their guidance.

Best Regards...

* Corresponding author: Keziban Sanem Çakar Turhan

Address: Ankara University Faculty of Medicine, Ibni Sina Hospital Department of Anesthesiology and ICU, Ankara Turkey

Tel: 00 90 533 3689520   Fax: 00 90 312 311 5057

E-mail: [email protected]       

Response to Reviewer Comments

1.      Summary

We would like to express our gratitude for taking the time to review our article. Your comments and contributions are greatly valued and have helped us improve our work. You can find below our detailed responses to your feedback, as well as the relevant revisions and corrections contained in the resubmitted file.

2.      Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

No additional comments.

Are all the cited references relevant to the research?

Yes

No additional comments.

Is the research design appropriate?

Yes

No additional comments.

Are the methods adequately described?

Yes

No additional comments.

Are the results clearly presented?

Yes

No additional comments.

Are the conclusions supported by the results?

Yes

No additional comments.

3.      Point-by-point response to Comments and Suggestions for Authors

Comments 1: The key finding relevant to clinicians is that BMI does not affect AC. As there are only 90 patients, could the absence of difference be due to type 2 error, i.e. relatively small sample size?

Response 1:  We appreciate your concern regarding the potential for a type 2 error due to the sample size. We conducted a comprehensive pilot study as part of our study process. Our pilot study revealed a correlation of 0.3 between BMI and AC. Based on these findings, we determined that the sample size should be 84 with a significance level of 0.05 and 80% power. Consequently, we believe that our sample size is adequate and that we have taken the necessary measures to minimise the possibility of a type 2 error. However, as can be seen from the BMI distribution histogram on page 4, which we added with the revision, we have 4 patients with a BMI between 35-40 and only 2 patients with a BMI greater than 40. It would appear that a significant portion of the patients are clustered between BMI 25-30. Consequently, rather than the sample size, this situation is a cause for concern in terms of type 2 error. In order to reduce this possibility, we conducted a correlation analysis of BMI with AC, both with and without grouping, as we mentioned in the article.

Comments 2:  Introduction paragraph 2: "shape of the abdomen changes from spherical to circular". This sentence may be difficult to comprehend to the readers. "circular' usually refers to a 2 dimensional object whereas spherical refers to 3 dimensional object. One would imagine the abdominal cavity becomes spherical with insufflation of carbon dioxide. Maybe the authors can explain in another way.

Response 2: We would like to express our gratitude for your valuable critique, which highlighted the terminological error and ambiguity present in our manuscript.  In response to your feedback, we have revised the sentence in the second paragraph of the introduction section on page 2 as follows: 'In the initial phase of increasing IAV, referred to as 'reshaping', IAP undergoes a minimal increase and the shape of the abdominal cavity changes from elliptical to spherical. This change in shape is primarily due to an increase in the anteroposterior diameter and a decrease in the transverse diameter of the internal abdominal perimeter.’

 Comments 3: Same paragraph as above: "The IAP undergoes a significant increase but without a significant increase in IAV." Wouldn't one expect the other way around, i.e. a volume of 3979ml carbon dioxide insufflated with a change of 15mmHg pressure? 

Response 3: Thank you for your insightful feedback on the relationship between IAP and IAV. Further review of the existing literature on this topic shows that the pressurization phase is clearly defined as the exponential phase in the pressure-volume (P-V) curve of the abdominal cavity. However, the existing literature does not provide a clear cut-off value for the transition from the stretching phase to the pressurization phase, giving estimated values in a wide range of 5600 to 7600 ml. It remains unclear whether a precise cut-off value can be defined, and further studies on this subject would be beneficial. In our study of patients undergoing elective abdominal surgery, we did not cross the threshold for intra-abdominal hypertension, prioritizing patient safety by ensuring that IAP did not exceed 15 mmHg. As a result, the total insufflated CO₂ volume (IAV₃) in our study was 3979 ± 1085 ml. When we evaluate these results in the light of the literature, it is important to acknowledge that some patients in our study may not have entered the pressurization phase during the measurements. This represents a potential limitation of our study and highlights the need for further research to clarify the optimal IAV limit for pressurization. Nevertheless, although we did not set a definite IAV limit for pressurization, we believe that our study is valuable in terms of identifying factors affecting abdominal compliance.

Furthermore, to avoid confusion among readers regarding the pressurization phase, we have revised the sentence describing the third phase in the second paragraph of the Introduction as follows: 'Finally, in the third phase of IAV increase, designated 'pressurization', minimal increases in IAV result in a significant increase in IAP. This phase represents the exponential phase of the P-V curve’

4.      Response to Comments on the Quality of English Language

Comment: The manuscript would benefit from editing by a native English speaker.

Response: Thank you for your feedback. Once the final version of the manuscript was completed, we received an editing service and certificate in English. We also checked it again after the revisions. However, if there is a specific section you would like us to review again, we would be happy to do so.