Effect of positive end-expiratory pressure ventilation on central venous pressure and intraoperative blood loss in patients undergoing laparoscopic hepatectomy

Objective:Tto investigate the effects of positive end-expiratory pressure(PEEP)ventilation on central venous pressure(CVP)and intraoperative blood loss in patients undergoing laparoscopic hepatectomy.Methods:46 cases of patients undergoing laparoscopic hepatectomy,25 cases of male,female 21 cases,ASAⅠ~Ⅲlevel,were randomly divided into two groups.In group A tidal volume was set to 6 ml/kg(Predicted Body Weight,PBW)and PEEP was set to 0 cmH2O.The tidal volume of group B was set as group A,PEEP was set to 8 cmH2O.CVP,MAP,and Ppeak were recorded in the supine position after intubation(T0),supine position after pneumoperitoneal(T1),anti-trendelenberg position after pneumoperitoneal(T2),supine position after surgery(T3),and Ddyn was calculated.The amount of nitroglycerin and the amount of blood loss were recorded.Results:Compared with group A,the CVP of group B was significantly increased at T1 and T2(P<0.05).Compared to T2 with T1 in group A and group B,CVP was decreased significantly(P<0.05).At T3,Cdyn in group B was significantly higher than that in group A(P<0.05).The amount of nitroglycerin in group B was significantly higher than that in group A(P<0.05).There was no significant difference in intraoperative fluid rehydration and blood loss between the two groups(P>0.05).Conclusion:PEEP with 8cmH2O can improve Ddyn in patients undergoing laparoscopic hepatectomy,but increased CVP.It requires more use of controlled low central venous pressure techniques to reduce intraoperative blood loss.

Role of proning and positive end-expiratory pressure in COVID-19

The novel coronavirus,which was declared a pandemic by the World Health Organization in early 2020 has brought with itself major morbidity and mortality.It has increased hospital occupancy,heralded economic turmoil,and the rapid transmission and community spread have added to the burden of the virus.Most of the patients are admitted to the intensive care unit(ICU)for acute hypoxic respiratory failure often secondary to acute respiratory distress syndrome(ARDS).Based on the limited data available,there have been different opinions about the respiratory mechanics of the ARDS caused by coronavirus disease 2019(COVID-19).Our article provides an insight into COVID-19 pathophysiology and how it differs from typical ARDS.Based on these differences,our article explains the different approach to ventilation in COVID-19 ARDS compared to typical ARDS.We critically analyze the role of positive end-expiratory pressure(PEEP)and proning in the ICU patients.Through the limited data and clinical experience are available,we believe that early proning in COVID-19 patients improves oxygenation and optimal PEEP should be titrated based on individual lung compliance.

Driving pressure in mechanical ventilation:A review

Driving pressure(ΔP)is a core therapeutic component of mechanical ventilation(MV).Varying levels ofΔP have been employed during MV depending on the type of underlying pathology and severity of injury.However,ΔP levels have also been shown to closely impact hard endpoints such as mortality.Considering this,conducting an in-depth review ofΔP as a unique,outcome-impacting therapeutic modality is extremely important.There is a need to understand the subtleties involved in making sureΔP levels are optimized to enhance outcomes and minimize harm.We performed this narrative review to further explore the various uses ofΔP,the different parameters that can affect its use,and how outcomes vary in different patient populations at different pressure levels.To better utilizeΔP in MV-requiring patients,additional large-scale clinical studies are needed.

Effects of positive end-expiratory pressure on intracranial pressure,cerebral perfusion pressure,and brain oxygenation in acute brain injury:Friend or foe?A scoping review

Background Patients with acute brain injury(ABI)are a peculiar population because ABI does not only affect the brain but also other organs such as the lungs,as theorized in brain–lung crosstalk models.ABI patients often require mechanical ventilation(MV)to avoid the complications of impaired respiratory function that can follow ABI;MV should be settled with meticulousness owing to its effects on the intracranial compartment,especially regarding positive end-expiratory pressure(PEEP).This scoping review aimed to(1)describe the physiological basis and mechanisms related to the effects of PEEP in ABI;(2)examine how clinical research is conducted on this topic;(3)identify methods for setting PEEP in ABI;and(4)investigate the impact of the application of PEEP in ABI on the outcome.Methods The five-stage paradigm devised by Peters et al.and expanded by Arksey and O'Malley,Levac et al.,and the Joanna Briggs Institute was used for methodology.We also adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)extension criteria.Inclusion criteria:we compiled all scientific data from peer-reviewed journals and studies that discussed the application of PEEP and its impact on intracranial pressure,cerebral perfusion pressure,and brain oxygenation in adult patients with ABI.Exclusion criteria:studies that only examined a pediatric patient group(those under the age of 18),experiments conducted solely on animals;studies without intracranial pressure and/or cerebral perfusion pressure determinations,and studies with incomplete information.Two authors searched and screened for inclusion in papers published up to July 2023 using the PubMed-indexed online database.Data were presented in narrative and tubular form.Results The initial search yielded 330 references on the application of PEEP in ABI,of which 36 met our inclusion criteria.PEEP has recognized beneficial effects on gas exchange,but it produces hemodynamic changes that should be predicted to avoid undesired consequences on cerebral blood flow and intracranial pressure.Moreover,the elastic properties of the lungs influence the transmission of the forces applied by MV over the brain so they should be taken into consideration.Currently,there are no specific tools that can predict the effect of PEEP on the brain,but there is an established need for a comprehensive monitoring approach for these patients,acknowledging the etiology of ABI and the measurable variables to personalize MV.Conclusion PEEP can be safely used in patients with ABI to improve gas exchange keeping in mind its potentially harmful effects,which can be predicted with adequate monitoring supported by bedside non-invasive neuromonitoring tools.

Influence of positive end-expiratory pressure upregulation on the right ventricle in critical patients with acute respiratory distress syndrome:an observational cohort study

Background This study aimed to investigate the influence of positive end-expiratory pressure(PEEP)on the right ventricle(RV)of mechanical ventilation-assisted patients through echocardiography.Methods Seventy-six patients assisted with mechanical ventilation were enrolled in this study.Positive end-expiratory pressure was upregulated by 4 cm H_(2)O to treat acute respiratory distress syndrome,wherein echocardiography was performed before and after this process.Hemodynamic data were also recorded.All variables were compared before and after PEEP upregulation.The effect of PEEP was also evaluated in patients with and without decreased static lung compliance(SLC).Results Positive end-expiratory pressure upregulation significantly affected the RV function.Remarkable differences were observed in the following:Tei index(P=0.027),pulmonary artery pressure(P=0.039),tricuspid annular plane systolic excursion(P=0.014),early wave/atrial wave(P=0.002),diaphragm excursion(P<0.001),inferior vena cava collapsing index(P<0.001),and SLC(P<0.001).There were no significant changes in heart rate,respiratory rate,central venous pressure,mean arterial pressure,and base excess(P>0.05).Furthermore,the cardiac output of the RV was not significantly affected.In patients with decreased SLC(n=41),there were more significant changes in diaphragm excursion(P<0.001),inferior vena cava collapse index(P=0.025),pulmonary artery pressure(P<0.001),and tricuspid annular plane systolic excursion(P=0.007)than in those without decreased SLC(n=35).Conclusion Positive end-expiratory pressure upregulation significantly affected the RV function of critically ill patients with acute respiratory distress syndrome,especially in those with decreased SLC.

Positive End-expiratory Pressure Titration after Alveolar Flecruitment Directed by Electrical Impedance Tomography

Background： Electrical impedance tomography （EIT） is a real-time bedside monitoring tool, which can reflect dynamic regional lung ventilation. The aim of the present study was to monitor regional gas distribution in patients with acute respiratory distress syndrome （ARDS） during positive-end-expiratory pressure （PEEP） titration using EIT. Methods： Eighteen ARDS patients under mechanical ventilation in Department of Critical Care Medicine of Peking Union Medical College Hospital from January to April in 2014 were included in this prospective observational study. After recruitment maneuvers （RMs）, decremental PEEP titration was performed from 20 cmH20 to 5 cmH20 in steps of 3 cmH20 every 5-10 min. Regional over-distension and recruitment were monitored with EIT. Results： After RMs, patient with arterial blood oxygen partial pressure （PaO2） ＋ carbon dioxide partial pressure （PaCO2） 〉400 mmHg with 100% of fractional inspired oxygen concentration were defined as RM responders. Thirteen ARDS patients was diagnosed as responders whose PaO2 ＋ PaCO2, were higher than nonresponders （419 ± 44 mmHg vs. 170 ±73 mmHg, P 〈 0.0001）. In responders, PEEP mainly increased-recruited pixels in dependent regions and over-distended pixels in nondependent regions. PEEP alleviated global inhomogeneity of tidal volume and end-expiratory lung volume. PEEP levels without significant alveolar derecruitment and over-distension were identified individually. Conclusions： After RMs, PEEP titration significantly affected regional gas distribution in lung, which could be monitored with EIT. EIT has the potential to optimize PEEP titration.

Effects of different levels of end-expiratory positive pressure on lung recruitment and protection in patients with acute respiratory distress syndrome

Background It is still controversial as to the implementation of higher positive end-expiratory pressure （PEEP） in patients with acute respiratory distress syndrome （ARDS）. This study was conducted to compare the lower and higher PEEP in patients with ARDS ventilated with low tidal volume, to investigate the relationship between the recruited lung volume by higher PEEP and relevant independent variables and to provide a bedside estimate of the percentage of potentially recruitable lung by higher PEEP. Methods Twenty-four patients with ARDS were studied. A lung recruiting maneuver was performed, then each patient was ventilated with PEEP of 8 cmH20 for 4 hours and subsequently with PEEP of 16 cmH20 for 4 hours. At the end of each PEEP level period, gas exchange, hemodynamic data, lung mechanics, stress index ＂b＂ of the dynamic pressure-time curve, intrinsic PEEP and recruited volume by PEEP were measured. Results Fourteen patients were recruiters whose alveolar recruited volumes induced by PEEP 16 cmH20 were （425_＋65） ml and 10 patients were non-recruiters. Compared with the PEEP 8 cmH20 period, after the application of the PEEP 16 cmH20, the PaO2/FiO2 ratio and static lung compliance both remained unchanged in non-recruiters, whereas they increased significantly in recruiters. Changes in PaO2/FiO2 and static lung compliance after PEEP increase were independently associated with the alveolar recruitment. Analyzing the relationship between recruiting maneuver （RM）-induced change in end-expiratory lung volume and the alveolar recruitment induced by PEEP, we found a notable correlation. Conclusions The results of this study indicated that the potential for alveolar recruitment might vary among the ARDS population and the higher PEEP levels should be limited to recruiters. Improving in PaO2/FiO2, static lung compliance after PEEP increase and the shape of the pressure-time curve could be helpful for PEEP application.

Alveolar stability under different combinations of positive end-expiratory pressure and tidal volume： alveolar microscopy in isolated injured rat lungs

Background High positive end-expiratory pressure （PEEP） and low tidal volume （VT） ventilation is thought to be a protective ventilation strategy. It is hypothesized that the stabilization of collapsible alveoli during expiration contributes to lung protection. However, this hypothesis came from analysis of indirect indices like the analysis of the pressure-volume curve of the lung. The purpose of this study was to investigate isolated healthy and injured rat lungs by means of alveolar microscopy, in which combination of PEEP and VT is beneficial with respect to alveolar stability （I-E%）. Methods Alveolar stability was investigated in isolated, non-perfused mechanically ventilated rat lungs. Injured lungs were compared with normal lungs. For both groups three PEEP settings （5, 10, 20 cmH20） were combined with three VT settings （6, 10, 15 ml/kg） resulting in nine PEEP-VT combinations per group. Analysis was performed by alveolar microscopy. Results In normal lungs alveolar stability persisted in all PEEP-VT combinations （I-E% （3.2±11.0）%）. There was no significant difference using different settings （P 〉0.01）. In contrast, alveoli in injured lungs were extremely instable at PEEP levels of 5 cmH20 （mean I-E% 100%） and 10 cmH2O （mean I-E% （30.7±16.8）%）; only at a PEEP of 20 cmH20 were alveoli stabilized （mean I-E% of （0.2±9.3）%）. Conclusions In isolated healthy lungs alveolar stability is almost unaffected by different settings of PEEP and VT. In isolated injured lungs only a high PEEP level of 20 cmH2O resulted in stabilized alveoli whereas lower PEEP levels are associated with alveolar instability.

Effect of neurally adjusted ventilatory assist on trigger of mechanical ventilation in acute exacerbation of chronic obstructive pulmonary disease patients with intrinsic positive end-expiratory pressure

Objective To compare the trigger delay and work of trigger between neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV) in acute exacerbation of chronic obstructive pulmonary disease(AECOPD) patients with intrinsic positive end-expiratory pressure (PEEP) during mechanical ventilation.

厚煤层综放面切顶卸压及停采位置优化研究

针对厚煤层综放面停采后在工作面后方形成悬臂结构、进而传递覆岩应力导致煤柱内超前应力影响范围广,需留设较大尺寸煤柱护巷而导致煤资源浪费,以高河矿W4302工作面为背景,采用理论分析、数值模拟、现场实测相结合的方法,对厚煤层综放面末切顶及合理停采位置进行研究。研究表明,不切顶情况下煤柱留设尺寸应大于70 m,切顶后煤柱留设尺寸可优化至60 m。终采线距离准备巷道60 m,选定水力压裂对综采面末进行切顶,并对W4302工作面对应的区域进行矿压监测,监测结果表明,切顶后巷道围岩变形量较小,验证了分析、模拟的可靠性及切顶的可行性,可为同类工程提供有益参考。

Erroneous presentation of respiratory-hemodynamic disturbances and postsurgical inflammatory responses in patients having undergone abdominal cavity cancer surgery

In this letter to the editor,the authors discuss the findings and shortcomings of a published retrospective study,including 120 patients undergoing surgery for gastric or colon cancer under general anesthesia.The study focused on perioperative dynamic respiratory and hemodynamic disturbances and early postsurgical inflammatory responses.

矿井井下地压微震监测技术优化研究

某矿由于井底地压的变化,经常发生冒顶、塌方等事故。以某矿地压监测系统为研究对象,提出引入微震监测系统的方法改进该矿区的现有技术,采用仿真计算与的方法计算了改进方案的定位误差与灵敏度,通过现场实验检测同一位置,系统给出数据的相对误差仅为10.34 m,证明了改进方案的可行性。

有创血压监测动脉穿刺置管流程的优化及效果评价

目的采用尖端腔内电图定位技术优化有创血压监测动脉穿刺置管流程,并进行效果评价。方法2021年6月-2022年6月,选取新疆维吾尔自治区某三级甲等医院和某二级甲等医院各60例进行有创血压监测的患者。依据穿刺方法,采用随机数字表法将研究对象分为优化组和传统组,每组60例。优化组优化动脉穿刺套管与压力换能器的连接流程,引入动脉穿刺尖端腔内电图定位技术;传统组使用穿透法动脉穿刺置管术。主要评价指标包括首次置管成功率、穿刺后瘀斑、穿刺出血、疼痛及患者满意度。结果与传统组相比,优化组首次置管成功率明显提高(95.0%与83.3%,P=0.04);穿刺后瘀斑率显著降低(5.0%与28.3%,P=0.01);穿刺出血率显著降低(0与100.0%,P=0.04);轻度疼痛患者比例明显增加(95.0%与75.0%,P=0.02),而中度疼痛患者比例明显下降(5.0%与25.0%,P=0.02);患者的满意度也得到明显提升(95.0%与75.0%,P=0.01)。结论有创血压监测动脉穿刺置管的流程优化能有效提高首次穿刺成功率,减少并发症,并增加患者满意度,可提供一种更安全、更高效的置管方法。

新型铁钻工铰接臂铰点位置的优化

鉴于铁钻工铰接臂铰点的位置直接影响伸展与升降油缸的最大工作压力与油压稳定性,在分析铁钻工铰接臂运动特性的基础上,以降低最大工作压力与提高压力稳定性为目标,采用统一目标函数法建立针对铰点位置的优化模型。采用遗传基因算法,利用Matlab优化工具箱,优化铰点位置。根据优化结果,借助Adams软件建立铰接臂动力学模型,比较优化前后伸展与升降油缸油压的变化情况。仿真结果表明:优化后的铰点位置大大提高铰接臂工作性能。

急性呼吸窘迫综合征机械通气肺复张的研究进展

呼吸支持是急性呼吸窘迫综合征(ARDS)治疗的基础,近年来运用小潮气量的肺保护性机械通气策略能明显改善ARDS患者的症状和预后,但小潮气量不利于塌陷肺泡的复张,因此有必要在肺保护的基础上联合使用肺复张手法使肺泡保持开放。但肺复张受ARDS病因、病程、复张前通气参数、复张方法、复张后潮气量及呼气末正压水平等多种因素的影响,本文对此进行了综述。

输水洞径对调压室最佳位置的影响

鉴于在输水管道上移动调压室位置可使涌浪压力与水锤压力彼此相互消长,当两者相等即对应了调压室最佳位置。以原输水洞径不变对应的最佳位置为前提,采用电站水力过渡过程的数学模型,模拟研究了引水隧洞及压力管道直径的改变对调压室最佳位置的影响。结果表明,随着引水隧洞直径的减小,调压室需左移远离厂房以恢复到最佳位置,且移动前后蜗壳末端压力差值呈增长趋势,但变幅较小;而随着压力管道直径的减小,调压室需右移靠近厂房以恢复平衡,且压力差值较前者更为明显。

软土盾构法隧道管片接头位置的优化研究

盾构法隧道衬砌结构由若干管片通过各种连接件 (如螺栓等 )拼装而成 ,因此相邻管片之间存在接头。本文在讨论接头位置对衬砌结构刚度、周围土层抗力分布形式以及结构本身内力、变形等影响的基础上 ,试图对接头位置的优化提出一些建议 ,以期能给衬砌结构设计提供参考。

阿舍勒铜矿微震监测系统站网布置的优化设计

根据新疆阿舍勒铜矿的矿山地质条件和地压活动规律,拟定了两套微震系统站网布置方案,一套是传感器七中段布置方案,另一套是三中段布置方案。从有效监测范围、灵敏度和定位误差综合考虑,最终确定传感器七中段布置方案。系统安装完毕后,经过5次人工放炮手段来调试系统的定位精度,最好精度达到7.1 m,本微震监测系统能对井下地压活动准确监测预报。

MEMS氮化钛谐振式压力传感器研究

提出了一种基于TiN双谐振梁结构的MEMS谐振式压力传感器,利用TiN谐振梁的谐振频率与被测压力的关系进行压力测量。针对传感器的敏感结构建立了数学模型,通过理论分析和ANSYS有限元软件的模拟,得出了谐振梁长度的变化范围和谐振梁的结构参数,并确定了TiN谐振梁在矩形压力膜上方的最佳位置。这对传感器的结构设计具有重要的指导意义。

无线传感网络通信优化算法仿真

研究无线传感网络声压干扰下的准确通信问题。高精度的传感器网络工作在较为敏感的环境下,对外围信号干扰极其灵敏,外界声音会形成非线性声压信号,对通信过程造成干扰。传统的通信方法中利用阀值设定门限进行噪声过滤,导致声压干扰下原始信号形成不同的幅值。信号与声压混合后无法确保电压接近门限值,导致噪声过滤不准。为通信准确性,提出了一种利用功率偏差补偿的无线传感网络通信优化方法。根据加权组播树相关理论,建立加权组播树,在通信过程中容易受到声压干扰,需要利用功率偏差补偿方法,对上述干扰造成的误差进行补偿。实验证明,利用改进算法进行无线传感网络通信,可以降低由于声压干扰的通信误码率。