Background: Establishing a pneumoperitoneum for laparoscopy is common surgical practice, with the goal to create an optimal surgical workspace within the abdominal cavity while minimizing insufflation pressure. Individualized strategies, based on neuromuscular blockade (NMB), pre-stretching routines, and personalized intra-abdominal pressure (IAP) to enhance surgical conditions are strategies to improve surgical workspace. However, the specific impact of each factor remains uncertain. This study explores the effects and side-effects of modifying intra-abdominal volume (IAV) through moderate and complete NMB in a porcine laparoscopy model. Methods: Thirty female Landrace pigs were randomly assigned to groups with complete NMB, regular NMB and a control group. Varying IAP levels were applied, and IAV was measured using CT scans. The study evaluated the maximum attainable IAV (V_max), the pressure at which the cavity opens (p₀), and the ease of expansion (λ_exp). Cardiorespiratory parameters, including peak inspiratory pressure (PIP), mean arterial pressure (MAP), heart rate (HR), and cardiac output (CO), were continuously recorded to evaluate side-effects. Results: There were no significant weight differences between NMB groups (median 21.1 kg). Observed volumes ranged from 0 to 4.7 L, with a mean V_max of 3.82 L, mean p₀ of 1.23 mmHg, and mean λ_exp of 0.13 hPa⁻¹. NMB depth did not significantly affect these parameters. HR was significantly increased in the complete NMB group, while PIP, MAP, and CO remained unaffected. Repeated insufflation positively impacted V_max; ease of opening; and expanding the cavity. Conclusion: In this porcine model, the depth of NMB does not alter abdominal mechanics or increase the surgical workspace. Cardiorespiratory changes are more related to insufflation pressure and frequency rather than NMB depth. Future studies should compensate for the positive effect of repeated insufflation on abdominal mechanics and surgical conditions.

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In laparoscopic surgery the abdominal cavity is insufflated with pressurized carbon dioxide gas to create workspace. This pressure is exerted through the diaphragm onto the lungs, competing with ventilation and hampering it. In clinical practice the difficulty of optimizing this balance can lead to the application of harmfully high pressures. This study set out to create a research platform for the investigation of the complex interaction between insufflation and ventilation in an animal model. The research platform was constructed to incorporate insufflation, ventilation and relevant hemodynamic monitoring devices, controlling insufflation and ventilation from a central computer. The core of the applied methodology is the fixation of physiological parameters by applying closed-loop control of specific ventilation parameters. For accurate volumetric measurements the research platform can be used in a CT scanner. An algorithm was designed to keep blood carbon dioxide and oxygen values stable, minimizing the effect of fluctuations on vascular tone and hemodynamics. This design allowed stepwise adjustment of insufflation pressure to measure the effects on ventilation and circulation. A pilot experiment in a porcine model demonstrated adequate platform performance. The developed research platform and protocol automation have the potential to increase translatability and repeatability of animal experiments on the biomechanical interactions between insufflation and ventilation.@en

Background: Abdominal compliance describes the ease of expansion of the abdominal cavity. Several studies highlighted the importance of monitoring abdominal compliance (C_ab) during the creation of laparoscopic workspace to individualize the insufflation pressure. The lack of validated clinical monitoring tools for abdominal compliance prevents accurate tailoring of insufflation pressure. Oscillometry, also known as the forced oscillation technique (FOT), is currently used to measure respiratory mechanics and has the potential to be adapted for monitoring abdominal compliance. This study aimed to define, develop and evaluate a novel approach which can monitor abdominal compliance during laparoscopy using endoscopic oscillometry. Materials and methods: Endoscopic oscillometry was evaluated in a porcine model for laparoscopy. A custom-built insufflator was developed for applying an oscillatory pressure signal superimposed onto a mean intra-abdominal pressure. This insufflator was used to measure the abdominal compliance at insufflation pressures ranging from 5 to 20 hPa (3.75 to 15 mmHg). The measurements were compared to the static abdominal compliance, which was measured simultaneously with computed tomography imaging. Results: Endoscopic oscillometry recordings and CT images were obtained in 10 subjects, resulting in 76 measurement pairs for analysis. The measured dynamic C_ab ranged between 0.0216 and 0.261 L/hPa while the static C_ab based on the CT imaging ranged between 0.0318 and 0.364 L/hPa. The correlation showed a polynomial relation and the adjusted R-squared was 97.1%. Conclusions: Endoscopic oscillometry can be used to monitor changes in abdominal compliance during laparoscopic surgery, which was demonstrated in this study with a comparison with CT imaging in a porcine laparoscopy model. Use of this technology to personalize the insufflation pressure could reduce the risk of applying excessive pressure and limit the drawbacks of insufflation.

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