PONE-D-21-16924

Intranasal oxygen reverses hypoxaemia in immobilised free-ranging capybaras (Hydrochoerus hydrochaeris)

PLOS ONE

Dear Dr. Carregaro,

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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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

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

Reviewer #1: I Don't Know

Reviewer #2: 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

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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

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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: 1. Line 26 : Mention the scientific name

2. Line 90 : Describe the recumbency in which the animals were maintained

3. Line 90 : ...... maintained in breathing air.... (Mention the percentage of oxygen for better understanding)

4. Line 93: Oxygen was provided ............ (Mention the percentage of oxygen for better understanding)

5. Line 96:..... height of medial corner of the eye (Consider using the term medial canthus of eye)

6. Line 98 to 102: Was the reversal agents mixed in a single syringe ?? (Describe it as in separate syringes)

Reviewer #2: Dear authors,

this study aims to verification of hypoxaemia prevention in capybaras by oxygen supplementation during anesthesia. As any anesthetic protocol for wild animals the presented findings may be of use in wildlife population control as well as for treatment of animals in captivity. This makes it a worth publishing. On the other hand, the paper is kept very technical. Without any additional contribution to the field and I do not find it suitable for publication in high ranking journal in its current state. I am missing a review of so far published anesthetic protocols in capybaras and I do not like the experimental design. I would understand if the design was governed by other study/procedure and this study was a by product, but there is no indication for that. Moreover the most basic physiological parameters - breathing rate and hearth rate - were not measured. Apart from this, I have also following specific comments:

45 "it can" -> "it's population"

54 there are a multiple anesthesia protocols missing. Eg https://doi.org/10.29374/2527-2179.bjvm107220, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7136804/ or https://www.jstor.org/stable/3784559.

55-58 Please show why is this a concern with capybaras. Do other protocols result in hypoxaemia as well? Even anecdotic observations could be informative. It would be good if you could justify why you used a different anesthetic protocol than those already published. Are there any practical or theoretical advantages or disadvantages of your protocol or of the published protocols?

59-62 Please explain the choice of oxygen flow rates. Did you have some preliminary data?

Was any other treatment done on the capybaras (eg sterilization) during the anesthesia or was the restraint only because of this study?

Materials and methods

78 please indicate the sex in the raw data and check the (rounding of) mean weight. My calculation suggest that the average mass is 49kg.

82-88 Why did you choose these exact doses? Are these doses recommended by the manufacturer for rodents/caviomorphs/capybaras?

88 Was weight estimated or measured? If estimated, please add the dose of anesthetic in the raw data.

90-93 Please justify the design. I do not see apparent advantage in your design. It seems to me that it would be better if you started started with 3 groups, which would either be air, 2L/min and 5L/min oxygen supplementation immediately after onset on anesthesia. Such design would allow more direct comparison by paired tests and would also be more linked with the planned use of the anesthesia protocol. I do not expect anyone to first wait 30 min and then apply oxygen to follow your protocol. If you aimed to show that hypoxaemia is reversible, please state this clearly.

103 "all the groups ..." please be more specific here. I do not understand the sentence, what repetition you mean?

106 "25x7 mm" Please specify this in more detail or remove the information.

111 Is there any support for the assumption that the cartridges measure/calculate SaO2 and other parameter correctly? I doubt that there is data for this in capybaras and as such this should be clearly admitted. I do not find your statement in discussion too helpful. You could for example estimate the possible error or put emphasis on the non-calculated parameters. What is the precision of measurement by CG8+ cartridges?

113 How was the Tb measured?

116 I believe that this is not correct. Do you have any justification for this approach?

120 Why didn't you use the measured body temperature?

120 RQ=1 - Why? Normally assumed RQ is 0.85.

122 pH2O=47 mmHg - please justify this assumption. It seems to me that you assume that the temperature of the expired air has temperature of 37°C and saturated water vapour content at that temperature. I doubt this is correct. The maxilloturbinals in the nasal cavity will for sure preserve some heat and water, resulting in lower expired air temperature and lower water vapor pressure in the expired air. Also please explain all abbreviations. PAO2 and PiO2 are not explained.

136 Why did you use one-tailed paired t-test? For single tailed test you need to state the hypothesis first (greater/lower). What do you mean by intragroup?

Results

146 "The capybaras remained quiet after they were caught in the trap." How do you know this? Were the traps observed?

146 "The small size of the traps facilitated physical restraint with the net for drug administration by hand injection." This belongs to methods.

148 not meaningful to pool the two protocols at this moment. You explain the pooling below. Please check the mean, my calculations show 9.9min mean induction time.

149-150. missing Test statistics, p levels, df. Pleas provide this data and the tests for the revision process or even better place them in an appendix.

153 Please define hypoxaemia in methods. What is the threshold for hypoxaemia?

154 This information is not shown in Table 1. Only means are presented in Table 1. Please reformulate the sentence.

154 check/remove the ">" sign.

157 difference in what?

160 Please list all abbreviation in the table caption. Table should be able to stand alone. Valid for Tab. 2 as well.

Tab 1 3rd column. Group does not seem to be a good name. Moreover this column is the same in whole table and therefore redundant. Please remove. Same for table 2

Please list the parameters by subgroups as well. Add subgroup term in methods, you call call them groups there You may still keep the grand mean as well. You are showing statistical significant differences for the paired test and we do not see the first value of the pair. Moreover, it seems that you are using paired t-test, which has an assumption of normal distribution for data which you tested distribution and claim non-normal for a different test.

SaO2 It seems that you compared percentages by parametric test without any transformation. Please justify, the usual apprach is to perform arcsine transformation prior to statistical comparison.

PaO2/FiO2 please add to methods how was this calculated. Add a unit. And consider removing from the table as it is not used in the second part of the table.

P(A-a)O2 Consider removing from the table or filling the other part of the table.

175 this wording suggest gradual increase, but only two measurements do not allow this statement.

Table 2

Why is this table separate from table 1? Consider merging the tables.

Unify the units throughout the text. Please express the units per Liter or justify. I also suggest to use SI units, ie mol/L everywhere where possible.

Lactate: please check if median really equals lower boundary of interquartile range. The raw data suggest median of 1 and not 0.7 in the 30 min group. Please check the other values as well. Moreover the numbers do not seem to be correct because of the assumption on line 116.

Na+ and K+ data missing for one animal in the raw data and the methods state that animals with missing data were excluded. Please adjust.

200 Fig 1. Consider erasing the figure and putting the correlations in the table1/2. "BE" not explained anywhere in the text, please delete it from the figure. In the image legend on the right change the decimal comma to decimal point. Remove the legend bellow the figure and put the text in figure caption.

204 Was the p-value adjusted for multiple tests? if yes, please add this information to methods. If not, consider doing so. With 22 test the probability of false positive is very high.

222 patients?

226 But how reliable and comparable with reality these figures are?

228-230. Ratios do not have dimension. Additionally the sentence does not have verb and is meaningless, please reformulate.

234 It seems to me that PaO2 increased in ALL animals in 2L group. Moreover I suggest not to mix PaO2 and hypoxaemic. Please be careful in formulations.

239 "animals that were breathing air in the 2L group" is not clear. Two meanings are possible. Either delete the breathing air or 2L group.

259 why however?

260 please check the units. You are using mmol/L here, but in table 2 you are using mg/dL with the same parameter. One of these is probably faulty.

265 If no long-term adverse effect of the anesthesia on the animals was observed, how necessary is to prevent hypoxaemia then?

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Reviewer #1: No

Reviewer #2: No

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Intranasal oxygen reverses hypoxaemia in immobilised free-ranging capybaras (Hydrochoerus hydrochaeris)

PONE-D-21-16924R1

Dear Dr. Carregaro,

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.

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Kind regards,

Ruud AW Veldhuizen

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

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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: Yes

**********

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

Reviewer #1: 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: 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)

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Reviewer #1: No