Different positive end expiratory pressure and tidal volume controls on lung protection and inflammatory factors during surgical anesthesia

BACKGROUND Mechanical ventilation can lead to the severe impairment of the metabolic pathway of alveolar surfactants,inactivating alveolar surfactants and significantly reducing lung-chest compliance.The cardiopulmonary function of elderly patients usually reduced to a certain extent,and there are lung complications after surgical anesthesia,just like lung barotrauma caused by mechanical ventilation,atelectasis and postoperative hypoxemia.AIM To investigate the effects of different positive end expiratory pressures(PEEPs)and tidal volumes(VTs)on respiratory function,the degree of the inflammatory response and hemodynamic indexes in patients undergoing surgery under general anesthesia.METHODS A total of 120 patients undergoing surgery for gastric or colon cancer under general anesthesia in Xinghua People's Hospital from January 2017 to January 2021 were randomly divided into Group A and Group B,with 60 cases in each group.The ventilation mode in Group A was VT(6.0 mL/kg)+PEEP(5.0 cmH_(2)O),while that in Group B was VT(6.0 mL/kg)+PEEP(8.0 cmH_(2)O).Blood gas parameters,respiratory mechanical parameters,inflammatory response indicators,hemodynamic indicators and related complications were compared between the two groups.RESULTS There were no significant differences in PaCO_(2),PaO_(2),oxygen or the examined indexes at T0 between group A and group B(P>0.05).The measured PaO_(2) value of patients in group A at T3 was higher than that in group B,and the difference was significant(P<0.05).There were no significant differences in peak airway pressure(P_(peak)),mean airway pressure or dynamic pulmonary compliance(Cdyn)at T0 between group A and group B(P>0.05).The measured P_(peak) value of patients in group A at T1 was higher than that in group B,and the difference was significant(P<0.05).The measured Cdyn value at T1 and T2 was greater than that in group B(P<0.05).Before surgery,there were no significant differences in tumor necrosis factor-α(TNF-α),interleukin(IL)-6 or IL-10 between group A and group B(P>0.05).After 4 h,the measured values of TNF-αand IL-6 in group A were lower than those in group B,and the differences were significant(P<0.05).The IL-10 Level in group A was higher than that in group B(P<0.05).At T0,there were no significant differences in cardiac output,cardiac index(CI),stroke volume index(SVI)or mean arterial pressure between group A and group B(P>0.05).The measured values of CI and SVI at T2 in patients in group A were higher than those in group B,and the differences were significant(P<0.05).CONCLUSION For patients undergoing surgery for gastric or colon cancer under general anesthesia,the VT(6.0 mL/kg)+PEEP(5.0 cmH_(2)O)regimen was more effective than the VT(6.0 mL/kg)+PEEP(8.0 cmH_(2)O)regimen in protecting the lung function and ventilatory function of patients,and it had better effects on maintaining hemodynamic stability and reducing inflammatory reactions.

INFLUENCE OF THREAD PITCH ON LOAD DISTRIBUTION ON THREADED END OF PRESSURE CYLINDER

One of the design methods for closing the end of a pressure cylinder is to screw down a screw plug on the threaded end of the cylinder. In this case, there is the problem of stress concentration in the threaded end of the pressure cylinder. To solve the problem, it is necessary to know accurately the load distribution on the threaded end of the cylinder. To find the load distribution on the threaded end of the pressure cylinder engaged with the screw plug, the following experiments are carried out. Applying the tensile load between the screw plug and the pressure cylinder and regarding the situation above as equivalent to the situation in which the internal pressure is applied, the load distribution is measured with the strain gauge. The influence of thread pitch on the load distribution on the threaded end of the cylinder is presented and an optimum pitch for design is discussed.

THE INTERACTION BETWEEN SHOCK WAVES AND FOAM IN A SHOCK TUBE

An experimental study and a numerical simulation were conducted to investigate the mechanical and thermodynamic processes involved in the interaction between shock waves and low density foam. The experiment was done in a stainless shock tube (80 mm in inner diameter, 10 mm in wall thickness and 5 360 mm in length). The velocities of the incident and reflected compression waves in the foam were measured by using piezo-ceramic pressure sensors. The end-wall peak pressure behind the reflected wave in the foam was measured by using a crystal piezoelectric sensor. It is suggested that the high end-wall pressure may be caused by a rapid contact between the foam and the end-wall surface. Both open-cell and closed-cell foams with different length and density were tested. Through comparing the numerical and experimental end-wall pressure, the permeability coefficients α and β are quantitatively determined.

Effect of Electroacupuncture on Heart Meridian for Change of End-Diastolic Intraventricular Pressure with Myocardial Ischemia in Rabbits

Objective: To explore the relationship between Heart Meridian (HM) and cardiac function. Methods: Thirty rabbits with acute myocardial ischemia resulting from intravenous dripping of pituitrin was established. Electroacupuncture (EA) on the HM and the Lung Meridian (LM) was applied, 3 points for each, and their change of end diastolic intraventricular pressure observed. Results: Obvious difference existed in the improvement of end diastolic intraventricular pressure on the HM and LM with EA treatment. The regulatory action of EA in HM on the cardiac function was significantly better than that of EA in LM. Conclusion: HM was closely related to the cardiac function.

Serum and lung endothelin-1 increased in a canine model of ventilator-induced lung injury

Background Nitric oxide （NO） plays an important role in acute lung injury （ALl）, acute respiratory distress syndrome （ARDS）, and in ventilator-induced lung injury （VILI）. A change in the balance of endothelin-1 （ET-1） and NO in the ALI/ARDS can also add to these problems. However, the profile of ET-1 and the balance of ET-1 and NO are still unknown in a VILI model. Methods Models of oleic acid induced ALl were established in dogs; these models were then randomized into three groups undergone different tidal volume （VT） mechanical ventilation, which included a VT6 group （VT equaled to 6 ml/kg body weight, positive end expiratory pressure （PEEP） equaled to 10 cmH20, n=-6）, a VT10 group （VT equaled to 10 ml/kg body weight, PEEP equaled to 10 cmH20, n=-4） and a VT20 group （VT equaled to 20 ml/kg body weight, PEEP equaled to 10 cmH20, n=-6） for 6-hour ventilation. The levels of ET-1 and NO in serum and tissue homogenates of lung were observed throughout the trial. Results PaO2 was increased after mechanical ventilation, but hypercapnia occurred in the VT6 group. The magnitudes of lung injury in the VT20 group were more severe than those in the VT6 group and the VT10 group. Serum levels of ET-1 and NO increased after ALl models were established and slightly decreased after a 6-hour ventilation in both the VT6 group and the VT20 group. The serum ET-1 level in the VT20 group was higher than that in the VT6 group and the VT10 group after the 6-hour ventilation （P 〈0.05） while the serum NO levels were similar in the three groups （all P 〉0.05）. There was no significant difference in serum ratio of ET-1/NO between any two out of three groups （P 〉0.05）, although there was a significant positive relationship between serum ET-1 and serum NO （r=0.80, P 〈0.01）. The levels of ET-1 and NO in the lung were increased after ventilation. The lung ET-1 level in the VT20 group was significantly higher than that in the VT6 group and VT10 group （both P 〈0.05） while there was no significant difference in lung NO levels between two groups （P〉0.05）. In the lung tissue, the ratio of ET-1/NO was significantly higher in the VT20 group than in the VT6 group and VT10 group after the 6-hour ventilation （P 〈0.05） as there was a significant positive relationship between ET-1 and NO in the lung （r=0.54, P 〈0.05）. Conclusions The production of ET-1 and NO was increased in serum and lung tissue in a VILI model. But the ET-1 levels increased much more than the NO levels in the lung, though there was a significant positive relationship between levels of ET-1 and NO. These results showed that there was an interaction between ET-1 and NO in a VILI model and changing the balance of ET-1 and NO levels might contribute to the pathophysiologic process of VILI.