Pressure-Controlled Inverse Ratio Ventilation during General Anesthesia for Open Abdominal Surgery Improves Postoperative Pulmonary Function

Background: Studies have shown that pressure-controlled ventilation improves alveolar gas distribution. And inverse ratio ventilation has advantages of improving oxygenation in acute respiratory distress syndrome (ARDS) patients. However, the effects that pressure-controlled inverse ration ventilation in patients undergoes endotracheal intubation general anesthesia have not been assessed. Objective: To investigate whether pressure-controlled inverse ratio ventilation (PIV) would improve ventilatory and oxygenation parameters as well as lung function compared to conventional ventilation in patients undergoing open abdominal surgery. Interventions: In the conventional ventilation (CV) group, the ventilation strategy involved zero end-expiratory pressure and volume-controlled ventilation. In the pressure-controlled inverse ratio ventilation (PIV) group, the strategy involved P high starting at 7 cm H2O, P low starting at 4 cm H2O, T high at 4 s, T low at 2 s, and an inspiratory-to-expiratory time ratio of 2:1. The ΔP value was adjusted according to VT. Pressure levels were increased by 2 cm H2O until a maximal VT was observed. Inspired oxygen fraction (FIO2) was 1.0 and tidal volume (VT) was 6 mL/kg in both groups. Main Outcome Measures: The primary outcome is pulmonary function tests. Hemodynamic, ventilatory and oxygenation parameters were measured;visual analog scale (VAS) scores, and nausea and vomiting scores were also measured. Results: The PIV group tolerated pressure-controlled inverse ratio ventilation without significant hemodynamic instability. Mean airway pressure and static compliance were significantly higher in the PIV group than those in CV group (P P 2 h was well tolerated and improved respiratory compliance and lung function on the first postoperative day.

Effect of Pressure-Controlled Inverse Ratio Ventilation on WBC,PCT and CRP in Rats Undergoing Radical Gastrectomy and Related Mechanism

Objective:To explore the effect of pressure-controlled inverse ratio ventilation on partial pressure of oxygen(PaO_(2)),partial pressure of carbon dioxide(PaC O2),dynamic lung compliance(Cdyn),white blood cell(WBC),procalcitonin(PCT),C-reactive protein(CRP),and other indicators.Methods:A total of 100 healthy Wistar rats,aged 6-8 weeks and weighing 300-356 g,were used to establish gastric cancer models with 1-methyl-3-nitro-1-nitrosoguanidine(MNNG).60 gastric cancer rats were randomly divided into three groups and treated with laparoscopic radical gastrectomy after anesthesia.Rats in the VCV group were given volume control ventilation,rats in the PCV group were given pressure control ventilation,and rats in the PC-IRV group were given pressure control inverse ratio ventilation.The levels of WBC,PCT and CRP in the three groups were observed and compared on the 1st,3rd and 5th day after operation.Results:There were significant differences in PaO_(2)levels at 15 min after ventilation mode change and at the time of pneumoperitoneum closure,and in PaCO_(2)and Cdyn levels at 10 min after induction and at 15 min after ventilation mode change among the three groups(P<0.05).The PaO_(2)levels in PC-IRV group were higher than those in VCV group and PCV group at 15 min after the ventilation mode was changed and at the time of closing the pneumoperitoneum.The level of PaCO_(2)in PC-IRV group was lower than that in VCV group and PCV group 10 min after induction and 15 min after ventilation mode change,and the level of PaCO_(2)in PC-IRV group was lower than that in VCV group when pneumoperitoneum was turned off.The level of Cdyn in PC-IRV group was higher than that in VCV group and PCV group at 10 min after induction and 15 min after ventilation mode change.The level of Cdyn in PC-IRV group was higher than that in PCV group at the time of closing pneumoperitoneum.The Cdyn level in PCV group was lower than that in VCV group at 15 min after ventilation mode change.There were significant differences in WBC levels among the three groups on the 1st day after operation(P<0.05),and there were no significant differences in PCT and CRP levels among the three groups on the 1st day after operation(P>0.05).There were significant differences in WBC,PCT and CRP levels in the three groups of rats on the 3rd and 5th days after surgery(P<0.05).Except for PCT and CRP on the 1st day after operation,the WBC on the 1st,3rd and 5th days after operation,PCT and CRP on the 3rd and 5th days after operation in PCV group and PC-IRV group were lower than those in VCV group(P<0.05).Except for WBC,PCT and CRP on 1st day after operation,the levels of WBC,PCT and CRP on the 3rd and 5th days after operation in PC-IRV group were lower than those in PCV group(P<0.05).Conclusion:During laparoscopic radical gastrectomy for gastric cancer,pressure-controlled inverse ratio ventilation can help rats maintain good respiratory status and lung compliance during the operation,which can effectively alleviate the postoperative inflammatory response.