Application of PRVC in laparoscopic surgery

Objective: To discuss the clinical significance and value of PRVC by monitoring, comparing and studying pressure control (PC), volume control (VC) and pressure-regulated volume control (PRVC) ventilation modes during pneumoperitoneum. Methods: Ninety patients with laparoscopic cholecystectomy were randomly and equally divided into 3 groups (PC group, VC group and PRVC group). Esophageal pressure (PES), mean airway pressure (PAWM), peak airway pressure (PAP), arterial blood carbon dioxide partial pressure (PaCO2), end-tidal carbon dioxide concentration in the expired air (ETCO2), tidal volume (TV), mean arterial pressure (MAP) and heart rate (HR) were not only detected before pneumoperitoneum, but also in 5, 10, 15 and 20 minutes after pneumoperitoneum. Results: PES after pneumoperitoneum in VC mode was obviously higher than that in PC and PRVC groups. In 10 minutes after pneumoperitoneum, levels of PaCO2 and ETCO2 became increased obviously in PC and VC groups (p < .05);levels of PaCO2 and ETCO2 were not only increased in PC group, but also the level of TV after pneumoperitoneum in PC group was significantly lower than that in the other two groups (p < .05). Levels of PaCO2 and ETCO2 were increased in PC and VC groups after pneumoperitoneum, along with the increase of MAP and HR (p < .05). After pneumoperitoneum, levels of MAP and HR in PRVC group were significantly lower than those in PC and VC groups (p < .05). Conclusions: PRVC mode can effectively reduce the pneumoperitoneum-induced increase of PAWM, PAP and PES without the unusual increase of PaCO2 and ETCO2 during surgery, so as to guarantee the stability of vital signs in perioperative patients.

A Novel Method for Determining the Void Fraction in Gas-Liquid Multi-Phase Systems Using a Dynamic Conductivity Probe

Conventional conductivity methods for measuring the void fraction in gas-liquid multiphase systems are typically affected by accuracy problems due to the presence of fluid flow and salinity.This study presents a novel approach for determining the void fraction based on a reciprocating dynamic conductivity probe used to measure the liquid film thickness under forced annular-flow conditions.The measurement system comprises a cyclone,a conductivity probe,a probe reciprocating device,and a data acquisition and processing system.This method ensures that the flow pattern is adjusted to a forced annular flow,thereby minimizing the influence of complex and variable gas-liquid flow patterns on the measurement results;Moreover,it determines the liquid film thickness solely according to circuit connectivity rather than specific conductivity values,thereby mitigating the impact of salinity.The reliability of the measurement system is demonstrated through laboratory experiments.The experimental results indicate that,in a range of gas phase superficial velocities 5–20 m/s and liquid phase superficial velocities 0.079–0.48 m/s,the maximum measurement deviation for the void fraction is 4.23%.