Introduction

Gynecologic robotic surgery enhances precision and outcomes, but involves steep Trendelenburg positioning and pneumoperitoneum, which can impair respiratory function and raise the risk of postoperative pulmonary complications (POPCs) [1]. Gynecologic robotic surgery is challenging in Class 3 obesity patients, who exhibit alterations in lung volumes and respiratory mechanical properties inversely correlated with BMI [2]. Under general anesthesia and pneumoperitoneum in a steep Trendelenburg position, a Class 3 obesity patient may experience a significant decrease in lung and chest wall compliance, worsening ventilation–perfusion mismatch, and increasing intrapulmonary shunting, which may result in intraoperative arterial hypoxemia and hypercapnia [1, 2]. Despite general suggestions to optimize ventilatory management during robotic surgery, the level of evidence to determine the optimal ventilation strategy is weak, and data are lacking in severe Class 3 obesity patients [1]. We contribute by reporting how individualized positive end-expiratory pressure (PEEP) within the framework of volume-controlled inverse ratio protective lung ventilation guided by driving pressure (DP) and mechanical power (MP), may play a pivotal role in the effective ventilation strategy for severe Class 3 obesity patients undergoing robotic gynecological surgery.

Figure 1: Intraoperative ventilation parameters, positive end-expiratory pressure decremental trials, and arterial blood gas analysis in a severe Class 3 obesity patient undergoing robotic-assisted hysterectomy with bilateral ovariectomy. Pre-pneumoperitoneum: 10 min before the institution of carbon dioxide pneumoperitoneum; during pneumoperitoneum: 10 min after the beginning of carbon dioxide pneumoperitoneum; post-pneumoperitoneum: 10 min after the end of carbon dioxide pneumoperitoneum. The patient was placed in the 20-30° reverse Trendelenburg position. (A) Ventilator settings. VC-IRV: volume-controlled inverse ratio ventilation with individualized positive end-expiratory pressure (PEEP) (black frame); PBW: predicted body weight. Before the first PEEP decremental trial, the starting PEEP was 10 cmH₂O. (B) PEEP decremental trial. To find the individualized PEEP (black frame), PEEP was set at 20 cmH₂O and then decreased in 2-cmH₂O steps to 10 cmH₂O after calculation of static elastance (E_stat, cmH₂O/l), static compliance (Cstat, ml/cmH₂O), driving pressure (DP, cmH₂O) measured as plateau pressure (cmH₂O) minus PEEP (cmH₂O), and mechanical power (MP, J/min), according to a simple equation proposed for volume-controlled ventilation. [3] The FLOW-i^® ventilator required a 5-sec inspiratory hold and 5-sec expiratory hold to calculate plateau pressure, total PEEP, E_stat, and C_stat, as suggested by the manufacturer. (C) Individualized PEEP (black frame). Arterial blood gas analysis observed after 10 min of the choice of individualized PEEP, after the PEEP decremental trial.

Anesthesia was then maintained with sevoflurane and remifentanil titrated to ensure a bispectral index value of 40-50. As part of multimodal analgesia, ketamine 70 mg was administered (50 mg with clonidine 0.1 mg pre-pneumoperitoneum, and 20 mg post-pneumoperitoneum), accompanied by continuous infusions of magnesium 4 g and lidocaine 200 mg during anesthesia maintenance. A clinically validated electromyography neuromuscular function monitor (TwitchView® Monitor, Blink Device Company, Seattle, Washington, United States of America) was adopted, as per the manufacturer’s recommendations, to ensure a deep block level (post-tetanic counts 1-5) during the surgery and a full recovery at the end.

Invasive blood pressure was adopted, and a central venous line was placed under ultrasound guidance.

Then, before starting surgery, with the patient placed in the 20–30° Trendelenburg position, a PEEP decremental trial was performed to find the individualized PEEP, as suggested by the best combination of static elastance, static compliance, and DP, measured as plateau pressure minus PEEP. PEEP was set at 20 cmH2 O and then decreased in 2-cmH2 O steps to 10 cmH2 O, registering all ventilatory and respiratory parameters at each PEEP level. A simple equation proposed for volume-controlled ventilation to estimate the MP [3] was used to support the choice of the individualized PEEP. The PEEP decremental trial was performed before, during, and after pneumoperitoneum (see Figure 1 for PEEP decremental trials). Intra-abdominal pressure was placed at 12 mmHg and maintained unaltered throughout the surgery, resulting in an adequate surgical view.

Arterial oxygenation remained substantially stable during surgery. An increased respiratory rate was sufficient to manage pneumoperitoneum-induced hypercapnia, effectively returning to baseline value by the end of the procedure (see Figure 1 for arterial blood gas analysis). The cardiovascular parameters were stable throughout the surgical procedure.

At the conclusion of the uneventful 2-hour surgery, remifentanil was discontinued. Ondansetron 8 mg and ketorolac 30 mg were given for postoperative nausea and vomiting, and pain prophylaxis, respectively. A bilateral ultrasound-guided transversus abdominis plane block was performed using a total of 40 ml of ropivacaine 0.25%. Sugammadex 620 mg was administered to reverse the deep rocuronium-induced neuromuscular block (from five post-tetanic counts to a train-of-four ratio of 1.0 in 80 seconds). Sevoflurane was then discontinued, the patient awakened, and the tracheal tube removed 10 minutes later. The patient had no pain, postoperative nausea and vomiting, or signs of respiratory failure in the post-anesthesia care unit. She was discharged home after four days without any complications.

Discussion

Intraoperative lung-protective mechanical ventilation comprises low tidal volume (e.g., tidal volume 6-8 ml/kg), limited inspiratory pressure (e.g., plateau pressure <30 cmH₂O), and the application of PEEP [2]. It is a strategy utilized to mitigate the risk of ventilator-induced lung injury that arises from alveolar overdistention, repeated recruitment and collapse, or atelectasis [2, 4, 5], thereby diminishing the risk of POPCs [6].

Class 3 obesity patients often exhibit compromised intraoperative pulmonary mechanics resulting in elevated airway plateau and driving pressures, increased lung elastance, and reduced end-expiratory transpulmonary pressures [2,7]. Intraoperative lung-protective mechanical ventilation may benefit from higher PEEP levels [2], which showed to enhance intraoperative lung ventilation and oxygenation [7] and improve postoperative outcomes by significantly reducing the risk of acute hypoxic respiratory failure [8].

 Pneumoperitoneum and Trendelenburg positioning further impact intraoperative pulmonary mechanics in Class 3 obesity patients undergoing robotic laparoscopic surgery [5].  However, the degree of impairment varies widely among patients suffering from obesity, despite using a lung-protective ventilation strategy [5].

So, monitoring tidal cycle mechanics is crucial for lung protection [9, 10]. Measuring respiratory compliance provides valuable insights into the respiratory system’s mechanical properties [9]. Additionally, compliance determines the DP required to inflate the lungs with a specific tidal volume [9]. DP is an important mediator of ventilator-induced lung injury [2, 4, 9]. Adjusting PEEP and tidal volume can potentially reduce DP [4]. An inverse inspiratory-to-expiratory time ratio may further contribute by increasing functional residual capacity, reducing peak and plateau pressures, and improving respiratory mechanics, as observed in patients suffering from obesity undergoing gynecologic robotic surgery [10].

At a fixed tidal volume, the role of PEEP is crucial for DP [4]. While a moderate PEEP (4–8 cmH₂O) seems to be associated with better outcomes in patients undergoing robotic surgery [1], higher individualized PEEP is necessary in Class 3 obesity patients [5] to restore end-expiratory lung volume, regional ventilation distribution, and oxygenation during anesthesia [7]. However, increasing PEEP should not be accompanied by an increase in DP [2,4]. Changes in PEEP levels that lead to increased DP are associated with a significantly higher incidence of POPCs in adults undergoing noncardiac surgery [11].

Individualized PEEP settings can vary significantly among patients suffering from obesity. In cases of Class 3 obesity, a PEEP of 20 cmH₂O or higher may be required to sustain optimal lung ventilation during procedures involving pneumoperitoneum or Trendelenburg positioning [5]. During robotic laparoscopic abdominal surgery, PEEP levels should be adjusted based on BMI and the specific surgical stage [5], but it is crucial to tailor intraoperative lung-protective mechanical ventilation individually, taking into account not only the patient’s current physiological state but also their responses to treatment. DP should, then, be considered as a guide for the individualized PEEP [2, 4]. However, an individualized MP-based ventilation strategy may also be considered. MP is a novel concept that shows promise as an indicator of ventilator-induced lung injury. The MP, including tidal volume, respiratory rate, inspiratory flow, peak pressure, and PEEP in the equation, may help to estimate better than DP the contribution of the different ventilator-related causes of lung injury and their variations [3]. At the moment, a value of 18 J/min seems to discriminate the outcome [3]. In an experimental setting, mechanical ventilation is associated with lung injury even at low MP. The best compromise between severe histological injury and gas exchange was achieved at respiratory system MPs between 3 and 7 J/min [12].

Opioid-sparing anesthesia employing multimodal analgesia techniques, such as local anesthetics, should be utilized to minimize opioid-induced adverse respiratory effects in Class 3 obesity patients following surgery [2]. Deep neuromuscular blockade, compared to moderate, optimizes the view of the surgical field and has been shown to improve perioperative care [13]. A complete reversal of neuromuscular blockade, evaluated through quantitative monitoring of neuromuscular function, is recommended to enhance patient recovery [13]. Compared to neostigmine, sugammadex appears to further reduce the risk of POPCs (Relative Risk 0.31) [14].

Conclusion

Adopting an intraoperative lung-protective mechanical ventilation combining a volume-controlled inverse ratio ventilation and individualized PEEP after the recruitment maneuvre may be an effective strategy to improve lung function and oxygenation [2,10,15]. DP [4] and MP [3] should be adopted in the context of lung-protective mechanical ventilation [2] to optimize the ventilatory management of Class 3 obesity patients in any stage of robotic gynecological surgery.

Acknowledgments: None.

Ethical Considerations: This article adheres to the applicable Enhancing the Quality and Transparency of Health Research (EQUATOR) guidelines using the Case Reports (CARE) checklist. An Institutional Review Board approval was not required for this single-patient case report. Written informed consent from the patient was obtained for the publication of this case report.

Funding: None.

Conflict of Interest: No potential conflict of interest relevant to this article was reported.

References

1. Chiumello D, Coppola S, Fratti I, Leone M, Pastene B (2023) Ventilation strategy during urological and gynaecological robotic-assisted surgery: a narrative review. Br J Anaesth 131(4):764-774.
2. Carron M, Safaee Fakhr B, Ieppariello G, Foletto M (2020) Perioperative care of the obese patient. Br J Surg 107(2): e39-e55.
3. Giosa L, Busana M, Pasticci I, Bonifazi M (2019) Mechanical power at a glance: a simple surrogate for volume-controlled ventilation. Intensive Care Med Exp 7(1):61.
4. Ahn HJ, Park M, Kim JA, Yang M, Yoon S, et al. (2020) Driving pressure guided ventilation. Korean J Anesthesiol 73(3):194-204.
5. Tharp WG, Murphy S, Breidenstein MW, Love C, Booms A, et al (2020) Body Habitus and Dynamic Surgical Conditions Independently Impair Pulmonary Mechanics during Robotic-assisted Laparoscopic Surgery. Anesthesiology 133 (4): 750-763.
6. Bolther M, Henriksen J, Holmberg MJ, Jessen MK, Vallentin MF, et al (2022) Ventilation Strategies During General Anaesthesia for Noncardiac Surgery: A Systematic Review and Meta-Analysis. Anesth Analg 135(5):971-985.
7. Nestler C, Simon P, Petroff D, Hammermüller S, Kamrath D, et al (2017) Individualized positive end-expiratory pressure in obese patients during general anaesthesia: a randomized controlled clinical trial using electrical impedance tomography. Br J Anaesth 119(6):1194-1205.
8. Choi JY, Al-Saedy MA, Carlson B (2023) Positive end-expiratory pressure and postoperative complications in patients with obesity: a review and meta-analysis. Obesity (Silver Spring) 31(4): 955-964.
9. Tawfik P, Syed MKH, Elmufdi FS, Evans MD, Dries DJ, et al. (2022) Static and Dynamic Measurements of Compliance and Driving Pressure: A Pilot Study. Front Physiol 13: 773010.
10. Zhang WP, Zhu SM (2016) The effects of inverse ratio ventilation on cardiopulmonary function and inflammatory cytokine of bronchoaveolar lavage in obese patients undergoing Gynaecological laparoscopy. Acta Anaesthesiol Taiwan 54(1):1-5.
11. Neto AS, Hemmes SN, Barbas CS, Beiderlinden M, FernandezBustamante A, et al. (2016) PROVE Network Investigators. Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data. Lancet Respir Med 4(4): 272-80.
12. Romitti F, Busana M, Palumbo MM, Bonifazi M, Giosa L, et al (2022). Mechanical power thresholds during mechanical ventilation: An experimental study. Physiol Rep 10(6): e15225.
13. Marinari G, Foletto M, Nagliati C, Navarra G, Borrelli V, et al. (2022) Enhanced recovery after bariatric surgery: an Italian consensus statement. Surg Endosc 36(10):7171-7186.
14. Carron M, Tamburini E, Ieppariello G, Linassi F (2023) Reversal of neuromuscular block with sugammadex compared with neostigmine and postoperative pulmonary complications in obese patients: metaanalysis and trial sequential analysis. Br J Anaesth 130(6): e461-e463.
15. Wang J, Zeng J, Zhang C, Zheng W, Huang X, et al (2022) Optimized ventilation strategy for surgery on patients with obesity from the perspective of lung protection: A network meta-analysis. Front Immunol 13: 1032783.