Respiratory acidosis in obese gynecological patients undergoing laparoscopic surgery independently of the type of ventilation

Accepted Manuscript Respiratory acidosis in obese gynecologic patients undergoing laparoscopic surgery independently of the type of ventilation. Sergey S. Simakov, PhD, Xenia I. Roubliova, MD, MSc, PhD, Alexey A. Ivanov, MD, PhD, Anar K. Kaptaeva, MD, PhD, Madina I. Mazitova, MD, PhD, ScD, Ospan A. Mynbaev, MD, PhD, ScD PII:

S1875-4597(16)30042-X

DOI:

10.1016/j.aat.2016.11.004

Reference:

AAT 270

To appear in:

Acta Anaesthesiologica Taiwanica

Received Date: 21 April 2016 Accepted Date: 23 November 2016

Please cite this article as: Simakov SS, Roubliova XI, Ivanov AA, Kaptaeva AK, Mazitova MI, Mynbaev OA, Respiratory acidosis in obese gynecologic patients undergoing laparoscopic surgery independently of the type of ventilation., Acta Anaesthesiologica Taiwanica (2016), doi: 10.1016/j.aat.2016.11.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Title page, Correspondence / Letter to the Editor

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Authors: Sergey S Simakov, PhD1 Xenia I Roubliova, MD, MSc, PhD1 Alexey A Ivanov, MD, PhD2 Anar K Kaptaeva, MD, PhD3 Madina I Mazitova, MD, PhD, ScD4 Ospan A Mynbaev, MD, PhD, ScD1,2*

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Full title: Respiratory acidosis in obese gynecologic patients undergoing laparoscopic surgery independently of the type of ventilation.

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Affiliations: 1 Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow region, The Russian Federation;

The Russian National Research Medical University named after N.I. Pirogov, Moscow, Russia I.M. Sechenov First Moscow State Medical University

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Kazan State Medical Academy, Kazan, Tatarstan, The Russian Federation

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*Corresponding author: Ospan A Mynbaev, MD, PhD, ScD, The MIPT Adjunct Professor, The Principal Researcher, Laboratory of Human Physiology, Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow region, The Russian Federation e-mail: [email protected] 9 Institutskiy per., Dolgoprudny, Moscow Region, 141700, The Russian Federation Mob: +79161271546

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Short title: Conventional/inverse ratio ventilation in obese patients undergoing gynecological laparoscopy

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Keywords: Lung ventilation; inverse ratio ventilation, CO2-pneumoperitoneum, obesity; hypercapnia; acidosis; airway pressure, lung compliance.

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To the Editor: ACCEPTED MANUSCRIPT An article by Zhang and Zhu1 recently published in your journal attracted our interest since it aimed to cast light on lung physiology changes depending on ventilation modes during laparoscopic surgery (LS) in gynecologic obese patients (OPs). This is an important multidisciplinary topic involving respiratory physiology, anesthesiology, obesity and minimally invasive LS. Based on their own investigation, the authors1 concluded that volume controlled inverse ratio ventilation (IRV) during LS reduces both airway pressures (Ppeak and Pplat), and the release of inflammatory cytokines, but also increases mean airway pressure (Pmean), and improves oxygenation and dynamic compliance of the respiratory system in OPs undergoing gynecologic LS. This procedure does not have any adverse respiratory and hemodynamic effects in comparison with those of conventional ratio ventilation (CRV). Subsequently, the authors stated that IRV is superior to CRV in terms of oxygenation, respiratory mechanics and inflammatory cytokine in OPs undergoing gynecologic LS.1 Upon closer reading of this article1, we have got several questions since conclusions do not completely meet the results and study design. Briefly, the authors designed their investigation as a comparative study of conventional ventilation with ratio 1:2 and IRV with ratio 2:1 during gynecologic LS upon CO2pneumoperitoneum with an intraperitoneal pressure (15 mmHg) and the patient 30° Trendelenburg position.1 PETCO2 was continuously monitored in order to maintain its concentration below 50 mmHg. Respiratory parameters (breathing rate or tidal volume) were adjusted to keep this parameter below 50 mmHg, however, increased amount of the minute ventilation value was missing. Such kind of study should be designed for all their parameters by the same perioperative monitoring of hemodynamic parameters in this study,1 registered at 5 minutes before anesthesia induction (T0), immediately before the onset of pneumoperitoneum (T1), 60 minutes after the onset of pneumoperitoneum (T2), and the end of surgery (T3) with appropriate statistical tests for repeated measures. We re-analyzed the results in order to understand the importance of the findings of this study1 concerning respiratory changes and lung mechanics (Fig.1 A, B, C) in order to demonstrate changes in pCO2 and pH values and their correlation with parameters of lung mechanics(Ppeak, Pmean, Compliance and AutoPEE). The authors concluded that IRV resulted in beneficial respiratory outcomes without adverse respiratory effects, although pCO2 and pH values were significantly changed during LS in both ventilation modes (see Fig.1 A). Moreover, after 60 min of CO2-pneumoperitoneum onset, respiratory changes were more pronounced in patients with IRV, which resulted high pCO2 value (48.65±5.44 mmHg) with a low pH (7.32±0.06), than those of patients with CRV, respectively 46.87±4.86 mmHg and 7.34±0.07. It is well known, that when arterial blood pH lower than 7.35, the condition is considered as acidosis. Definitely, the reason for these changes is related to the authors’ decision to control CO2 accumulation in their patients’ body at the level of PETCO2 - 50 mmHg. Usually this parameter is adjusted at physiologic level 35-40 mmHg in most of the analogous studies,2,3 taking into account physiologic arterial-to-end tidal CO2 gradient considered about 5-10 mmHg.4 IRV optimally decreased both airway pressure values (Ppeak and Pplat) in comparison with those of conventional ventilation, however, the adversely Pmean value was significantly increased in all monitored points (see Fig.1B). Another two parameters of lung mechanics (lung compliance and auto-PEEP) were lower in overall monitored points before and 60 min after the onset of pneumoperitoneum in patients with IRV in comparison with those of the conventional ventilation group (see Fig.1C). An increased rate of individuals with obesity among patients undergoing LS is a health care concern due to anesthesia and ventilation difficulties in obese population. 5 Therefore, understanding of physiology and pathophysiology of lung function is an important issue during long lasting LS with an increased insulation pressure in order to avoid possible side effects of CO2-pneumoperitoneum. We suggest that cause-effect mechanisms of a CO2 accumulation manifested with increased arterial pCO2 and decreased pH (see Fig.1A) during LS observed in this study1 are associated with the relatively high level of PETCO2 concentration and reduced capacity of CO2 elimination of these both ventilation modes due to highly adjusted PETCO2 concentration at 50 mmHg. In our opinion, most or patients in this study1 has experienced an acute respiratory acidosis during gynecologic laparoscopic surgery, therefore a design of such

kind of studies should be more precise in order to prevent such conditions. Further studies are called in order ACCEPTED MANUSCRIPT to study CO2 elimination capacity of IRV in OPs with more precisely designed study methodology. Conflict of interest The report has not been externally funded, and none of the authors has a conflict of interest.

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References 1). Zhang WP, Zhu SM. The effects of inverse ratio ventilation on cardiopulmonary function and inflammatory cytokine of bronchoalveolar lavage in obese patients undergoing gynecological laparoscopy. Acta Anaesthesiol Taiwan. 2016 Mar; 54(1):1-5. doi: 10.1016/j.aat.2015.11.001. Epub 2015 Dec 13. 2). Jo YY, Kim JY, Park CK, Chang YJ, Kwak HJ. The Effect of Ventilation Strategy on Arterial and Cerebral Oxygenation During Laparoscopic Bariatric Surgery. Obes Surg. 2016 Feb;26(2):339-44. doi: 10.1007/s11695015-1766-8. 3). Liao CC, Kau YC, Ting PC, Tsai SC, Wang CJ. The Effects of Volume-Controlled and PressureControlled Ventilation on Lung Mechanics, Oxidative Stress, and Recovery in Gynecologic Laparoscopic Surgery. J Minim Invasive Gynecol. 2016 Mar-Apr;23(3):410-7. doi: 10.1016/j.jmig.2015.12.015. Epub 2016 Jan 7. 4). Valenza F, Chevallard G, Fossali T, Salice V, Pizzocri M, Gattinoni L. Management of mechanical ventilation during laparoscopic surgery. Best Pract Res Clin Anaesthesiol. 2010 Jun;24(2):227-41. 5). Shah U, Wong J, Wong DT, Chung F. (2016) Preoxygenation and intraoperative ventilation strategies in obese patients: a comprehensive review. Curr Opin Anaesthesiol. Feb;29(1):109-18. doi: 10.1097/ACO.0000000000000267.

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Figure legends: Fig.1. Changes in respiratory parameters and lung mechanics depending on inspiratory to expiratory ventilation ratio during gynecologic laparoscopic procedures in obese patients, according to data1: A – changes of arterial blood gas values (pCO2 and pH); B – changes in airway pressure parameters (Ppeak and Pmean); C – parameters of lung compliance and Auto-PEEP. Changes of Pplat (not shown) were analogous with those of Ppeak. CRV - conventional ratio ventilation; IRV - inverse ratio ventilation.

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