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.

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.

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.

不同潮气量和PEEP对脉搏轮廓法与经肺热稀释法测量巴马猪心排血量的影响

【目的】探究机械通气时不同潮气量和呼气末正压(PEEP)对脉搏轮廓法与经肺热稀释法测量巴马猪心排血量的影响。【方法】选取实验用巴马猪12只,随机分为对照组(肺动脉导管热稀释法)、研究组A(经肺热稀释法)和研究组B(脉搏轮廓法),各4只。建立模型,采用不同方法测量心排出量,分析其一致性,比较不同潮气量和PEEP对心排出量的影响。【结果】脉搏轮廓法与热稀释法测定猪心排血量的相关系数为r=0.754,两者具有正相关性。经肺热稀释法与热稀释法测定猪心排血量的相关系数为r=0.771,两者具有正相关性。脉搏轮廓法、与热稀释法测定猪心排血量相对误差为13.5%,两者具有一致性。经肺热稀释法与热稀释法测定猪心排血量相对误差为12.9%,两者具有一致性。随着潮气量增加,心排出量值明显降低,差异具有统计学意义(P<0.05)。随着PEEP增加,猪心排出量明显降低,差异具有统计学意义(P<0.05)。【结论】脉搏轮廓法、经肺热稀释法与热稀释法测定猪心排血量的一致性良好;当机械通气潮气量或PEEP增加时猪心排血量逐渐下降。

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 titrated by transpulmonary pressure improved oxygenation and respiratory mechanics in acute respiratory distress syndrome patients with intra-abdominal hypertension

Background Intra-abdominal hypertension （IAH） is common in acute respiratory distress syndrome （ARDS） patients and when resulting in decrease of chest wall compliance will weaken the effect of positive end expiratory pressure （PEEP）. We investigated the effect of PEEP titrated by transpulmonary pressure （Ptp） on oxygenation and respiratory mechanics in ARDS patients with IAH compared with PEEP titrated by ARDSnet protocol. Methods ARDS patients admitted to the intensive care unit （ICU） of the Zhongda Hospital were enrolled. Patients were ventilated with volume control mode with tidal volume of 6 ml/kg under two different PEEP levels titrated by Ptp method and ARDSnet protocol. Respiratory mechanics, gas exchange and haemodynamics were measured after 30 minutes of ventilation in each round. IAH was defined as intra-abdominal pressure of 12 mmHg or more, Results Seven ARDS patients with IAH and 8 ARDS patients without IAH were enrolled. PEEP titrated by Ptp were significant higher than PEEP titrated by ARDSnet protocol in both ARDS patients with IAH （（17.3±2.6）cmH20 vs. （6.3±1.6） cmH2O and without IAH （（9.5±2.1） cmH2O vs. （7.8±1.9） cmH2O）. Arterial pressure of O2/fraction of inspired oxygen （PaO2/ FiO2） was much higher under PEEP titrated by Ptp when compared with PEEP titrated by ARDSnet protocol in ARDS patients with IAH （（27.2±4.0） cmHg vs. （20.9± 5.0） cmHg. But no significant difference of PaO2/FiO2 between the two methods was found in ARDS patients without IAH. In ARDS patients with IAH, static compliance of lung and respiratory system were higher under PEEP titrated by Ptp than by ARDSnet protocol. In ARDS patients with IAH, central venous pressure （CVP） was higher during PEEP titrated by Ptp than by ARDSnet protocol. Conclusion Positive end expiratory pressure titrated by transpulmonary pressure was higher than PEEP titrated by ARDSnet protocol and improved oxygenation and respiratory mechanics in ARDS patients with IAH.

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.

跨肺压导向滴定呼气末正压治疗ARDS的疗效及安全性的meta分析

目的:评价通过跨肺压导向滴定呼气末正压(PEEP)个体化治疗急性呼吸窘迫综合征(ARDS)与其他调整PEEP的方法相比对患者是否获益更多。方法:计算机检索PubMed、Embase、Web of Science、Cochrane Library、中国知网、中国生物医学文献、维普、万方数据库中关于跨肺压导向PEEP滴定、其他方法调整PEEP治疗ARDS患者的相关随机对照研究,检索时间限定为建库以来至2021年8月15日,并对纳入文献进行meta分析。结果:共纳入16篇文献,累计样本量1075例,其中跨肺压导向PEEP滴定共540例,其他PEEP滴定方法共535例。meta分析结果显示:与其他方法调整PEEP相比,跨肺压导向PEEP滴定可改善ARDS患者的氧合指数(WMD=46.54,95%CI:27.63~65.46,P<0.05)、血氧饱和度(WMD=6.03,95%CI:4.67~7.39,P<0.05)、肺顺应性(WMD=6.97,95%CI:4.71~9.23,P<0.05)、28 d病死率(OR=0.55,95%CI:0.38~0.79,P=0.001)。结论:跨肺压导向PEEP滴定与其他滴定方法相比疗效、安全性更优。

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.

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.

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.

跨肺压滴定PEEP在急性主动脉夹层术后低氧血症患者中的临床应用研究

目的探讨跨肺压指导呼气末正压通气(PEEP)选择对急性主动脉夹层术后低氧血症患者氧合、血流动力学及预后的影响。方法采用前瞻性随机对照研究,入选2014年1月—2015年8月急性Stanford A型主动脉夹层术后低氧血症患者28例,随机分为2组:个体化治疗组(n=19),肺复张后通过食道压监测结果调整PEEP;传统机械通气治疗组(n=9),肺复张后按照ARDSnet建议调整PEEP。比较2组患者呼吸、血流动力学参数、机械通气时间、住ICU时间及住院病死率。结果第72 h,个体化治疗组的PEEP、吸气末跨肺压均较传统机械通气治疗组高(P<0.05);第72 h,个体化治疗组动脉血氧分压(PO2)、氧合指数高于传统机械通气治疗组(P<0.05)。整个实验过程中,2组患者的心率和心排量无明显差异(P>0.05)。个体化治疗组患者机械通气时间和住ICU时间均比传统机械通气组时间短(P<0.05),2组患者的住院病死率无统计学差异(P>0.05)。结论肺复张后应用跨肺压指导PEEP的机械通气策略可改善急性主动脉夹层术后低氧血症患者氧合,缩短机械通气时间、住ICU时间,且不会引起循环波动。

快速输液条件下温度稀释法与动脉压法心输出量测定的比较

目的比较温度稀释法与动脉压法心输出量(CO)测定的不同,并观察快速输液条件下血流动力学的变化。方法选择ASAⅠ或Ⅱ级的骶骨肿瘤手术患者10例,麻醉诱导后,放置Swan-Ganz导管、FloTrac传感器和Vigileo监护仪,温度稀释法间断测定心输出量(ICO),动脉压法测定心输出量(APCO)。手术开始前30min内输注10ml/kg羟乙基淀粉130/0.4注射液,测定液体输注前后HR、MAP、CVP、肺动脉楔压(PAWP)、ICO、每搏量变异度(SVV)、APCO、每搏输出量指数(SVI)。采用Bland-Altman分析,比较两种方法测量CO的差异。结果 APCO-ICO的均数为-0.10L/min,95%CI为-1.14～0.94L/min。(APCO+ICO)/2的均数为5.97L/min,与95%区间的最大绝对值1.14L/min相比临床可以接受。快速液体后,CVP、PAWP、APCO和SVI明显升高(P<0.05或P<0.01);而SVV明显低于输液前(P<0.01);HR和MAP无明显变化。结论动脉压法测定CO与温度稀释法相关性好,可为围术期提供有效的血流动力学监测。

腹腔压力对急性肺损伤家猪呼吸力学及血流动力学的影响

目的探讨不同腹腔内压力(IAP)对急性肺损伤(ALI)家猪呼吸力学及血流动力学的影响。方法将8只家猪经耳缘持续静脉泵入油酸0.1 mL/kg制作急性肺损伤模型,采用氮气气腹法制作不同腹腔压力模型,随机将IAP设置为0、15和25 mm Hg,即分为IAP0组、IAP15组和IAP25组,动态监测心率(HR)、平均动脉压(MAP)、中心静脉压(CVP),采用脉搏轮廓持续心排出量监测(PiCCO)法动态监测心排出量(CO)、胸腔内血容量指数(ITBVI)等血流动力学指标,同时置入食管内压管动态监测食管内压(Pes)的变化。结果 IAP15组、IAP25组与IAP0组比较,Pes和气道峰压(Ppeak)均显著增加(P<0.01),肺顺应性(Cstat)则显著下降(P<0.05),跨肺压(Ptp)呈下降趋势,PaO2亦呈下降趋势,PaCO2则呈上升趋势,但均无统计学意义(P>0.05)。IAP15组、IAP25组与IAP0组比较,HR和CVP显著增加(P<0.05),CI和ITBVI则显著下降(P<0.05),但MAP无明显改变(P>0.05);ΔPes与CI的变化(ΔCI)呈负相关(r=-0.648,P<0.05)。结论急性肺损伤时,腹腔内压增高引起胸腔内压力增高,导致肺顺应性下降和心排出量下降。

跨肺压指导下机械通气对急性呼吸窘迫综合征患者呼吸功能和血液动力学的影响

目的:观察不同跨肺压(Pt P)指导下机械通气(MV)对急性呼及窘迫综合征(ARDS)患者呼吸功能及血液动力学的影响。方法:采用前瞻性随机对照研究,选取ARDS患者72例,按照随机数字表法分为观察组(55例)和对照组(17例)。根据设置不同的呼气末正压(PEEP)与胸腔内压(食管球囊测定法测得)计算得出不同的Pt P,观察组中,设定Pt P分别为10、15、20 cm H_2O 3个亚组,执行MV策略;对照组根据ARDS协作网(ARDSNet)意见制定MV策略;观察2组患者机械通气后1、24、48 h呼吸力学指标及血气分析结果,采用脉搏指示连续心排血量监测仪(PICCO)监测各时间点血液动力学指标,记录患者MV时间、RICU住院时间及28 d病死率。结果:治疗后,2组患者呼吸功能及血气分析指标均好转,但对照组各时间点呼吸功能与血液动力学指标比较差异无统计学意义(P> 0. 05);通气48h后,观察组中Pt P20 cm H_2O亚组肺容积、肺静态Cst、气道PIP、气道Pplat、PEEP及PaO_2、PaCO_2、PaO_2/FiO_2均明显高于对照组(均P <0. 05);血液动力学指标MAP、CVP、CI明显低于对照组(均P <0. 05); Pt P10 cm H_2O亚组肺容积、肺静态顺应性(Cst)、气道峰压(PIP)、气道平台压(Pplat)、呼气末正压(PEEP)及PaO_2、PaCO_2、PaO_2/FiO_2均明显高于对照组(均P <0. 05);血液动力学指标与对照组比较差异不明显(P>0. 05)。Pt P20 cm H_2O亚组MV时间与RICU住院时间较对照组明显缩短(均P <0. 05);各组间28d病死率比较,差异无统计学意义(P> 0. 05)。结论:跨肺压为10 cm H_2O时的机械通气,对ARDS患者呼吸功能及通气效果较好,对血液动力学影响小,是安全可靠的保护性肺通气策略。

经肺温度稀释法在肝及其与肾、胰、十二指肠联合移植围术期的应用研究

目的:观察经肺温度稀释法(PiCCO技术)在肝及其与肾、胰、十二指肠联合移植手术围术期的应用情况,并与改良式肺动脉漂浮导管(CCO导管)比较反映心脏前负荷参数的有效性。方法:对2例实施肝移植,1例实施肝脏、胰腺、十二指肠移植术,1例实施肝肾联合移植术的患者进行研究,4例患者均为男性,年龄42～48岁,ASAⅢ～Ⅳ级。无PiCCO及CCO导管置入禁忌证。静脉注射咪唑安定、异丙酚、芬太尼、维库溴胺后经鼻气管插管。于麻醉诱导前、气管插管后、切皮、无肝前期、无肝期、新肝前期、新肝期、术毕及术后血流动力学发生变化时,通过温度稀释法同时测定PiCCO与CCO系列参数。结果:共测得数据135组,其中全心舒张末期容积指数(GEDI)与每搏量指数正相关(r=0.77,P<0.001),肺动脉阻塞压与GEDI相关(r=0.44,P<0.05),中心静脉压与GEDI不相关(r=0.24,P>0.05);两种方法心输出量指数结果对比差异无统计学意义(P>0.05)。SVI与GEDI之间Pearson相关系数为r=0.77(P<0.001)。结论:在上腹部单或多器官移植围术期应用PiCCO技术可准确测量心输出量,其所测量的全心舒张末期容积与胸腔内血容积较CVP更能反映心脏前负荷变化。

应用经肺热稀释技术评价幼猪心输出量和容量负荷

目的 评价经肺热稀释法（TPTD）测量心输出量（CO）的准确性,以及该方法测量的胸内血容量指数（ITBVI）用于评价容量负荷的有效性.方法 研究10只幼猪,体重（20.6±1.9） kg.分别在基础血容量、高血容量和低血容量状态下进行同步的肺动脉热稀释法（PATD）测量CO （COPA）和TPTD测量CO（COTP）、ITBVI,每种状态下连续测量3次,同时记录中心静脉压（CVP）和心率.分析不同血容量状态下CVP、ITBVI与心指数（CI）、每搏输出量指数（SVI）的相关性.结果 共进行90次同步热稀释法测量CO.COTP与COPA相关系数为0.977 （P＜0.001）,平均偏差为（0.25 ±0.26） L/min（95％ CI：0.20～0.30 L/min,P＜0.001）.COTP变异系数为3.7％,COPA变异系数为5.4％.与基础血容量状态比较,高血容量状态下CVP和ITBVI均显著升高（P=0.002、0.019）,低血容量状态下ITBVI显著下降（P＜0.001）,但CVP的差异无统计学意义（P=0.050）.相关分析显示ITBVI与CI和SVI在基础血容量状态下呈高度正相关（r =0.741,P=0.014;r=0.885,P=0.001）,在高血容量和低血容量状态下均无显著相关性;CVP与CI和SVI在各种血容量状态下均无显著相关性.结论 TPTD在不同血容量状态下测量CO的准确度和精确度均理想,其测量的ITBVI与CVP比较可更有效地反映容量负荷.

肺复张对重症患者血流动力学的影响

各种原因引起的肺不张常常导致肺内分流增加、静脉血氧合不充分最终出现低氧血症甚至呼吸衰竭。肺复张的目的就是通过迅速短暂的增加气道压力来打开塌陷的肺泡。虽然肺复张可以改善氧合,但由于心肺以及心脏的左、右心室间的相互作用,可能造成胸内压力升高从而对心血管系统产生严重的影响。这篇综述的目的就是总结肺复张过程中心肺间的病理生理特征并探讨在肺复张过程中如何更好地监测这些特征的变化,从而在临床工作中更好地使用肺复张。