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.

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 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.

基于FloTrac/Vigileo监测不同PEEP值对患者心指数、每搏变异度及氧输送指数的影响

目的探讨Flo Trac/Vigileo监测下不同呼气末正压通气(PEEP)值对患者心指数(CI)、每搏变异度(SVV)及氧输送指数(DO_2I)的影响,为患者血流动力学管理和改善氧合治疗提供参考依据。方法择期行电视辅助胸腔镜食管癌根治术患者60例,使用FloTrac/Vigileo系统观察患者CI、SVV及DO_2I的变化,记录麻醉诱导后改左侧卧位(T0)、开CO_2气胸+0 PEEP 5 min(T1)后、开CO_2气胸+5 PEEP 5 min(T2)后、开CO_2气胸+10 PEEP 5 min后(T3)、开CO_2气胸+15 PEEP 5 min后(T4)患者的CI、SVV及DO_2I。结果与T0时点比较,T1、T2、T3和T4时点患者CI下降,SVV升高(P<0.05);与T1时点比较,T4时点患者CI下降,SVV升高,T2、T3时点DO_2I升高(P<0.05)。结论术中采用呼气末正压通气会对患者的CI及SVV造成一定的影响,采取5~10 PEEP值可显著改善氧合并且对CI和SVV影响较小,可以适当地应用于临床中。

利用压力-容积曲线呼气支最大曲率拐点选择PEEP对ARDS患者氧合及血流动力学的影响

目的探讨利用压力一容积（P—V）曲线呼气支最大曲率拐点选择呼气末正压（PEEP）对急性呼吸窘迫综合征（ARDS）患者氧合及血流动力学影响。方法选取25例ARDS患者，采用肺保护性通气，肺复张（RM）后随机分为两组：利用P—V曲线呼气支最大曲率拐点设置PEEP组（PPMc）和以P—V曲线低位拐点设置PEEP组（PLIP），观察并比较RM前后两组患者PaO2／FiO2、呼吸系统动态顺应性（Cdyn）、心率（HR）、平均动脉压（MAP）、中心静脉压（CVP）等指标的变化。结果RM后两组患者短时间内PaO：／FiO：和Cdyn均明显增加，PPMc组PaO2／FiO2在RM后1、2、4h较Pup组升高（P〈0．05）。PLIP组Cdyn在RM后很快降至RM前水平，PPMC组Cdyn在RM后1、2h高于PLIP组（P〈0．05）。两组RM时均有MAP、CVP下降，HR升高（P〈0．01）；HR、MAP在RM后很快恢复，PPMC组CVP持续升高至RM后2h（P〈0．05）。结论RM后利用P—V曲线呼气支最大曲率拐点选择PEEP可以使氧合及呼吸系统顺应性改善更为明显，对血流动力学无严重的不良影响。

FiO2×PEEP对重症甲型H1N1流感致急性肺损伤病情评估与预后价值研究

目的观察重症甲型H1N1流感导致急性肺损伤（ALI）患者FiO2×PEEP水平的变化，探讨其对最症甲型H1N1流感导致ALI严重程度及预后评估的价值。方法对2009—10—28～2009—12—28我院EICU收治的10例（存活组6例，死亡组4例）重症甲型经H1N1病毒感染患者进行病例回顾分析，分别监测每组患者每天的FiO2、PEEP、PaO2，并计算FiO2×PEEP及氧合指数（PaO2／FiO2），比较FiO2×PEEP与氧合指数之间关系，动态比较两组治疗前后FiO2×PEEP的变化趋势及其差异。结果①FiO2×PEEP与氧合指数呈负相关（r=-0．44，P〈0．05）；②存活组治疗前后FiO2×PEEP均低于死亡组；③存活组在治疗干预后FiO2×PEEP逐渐下降，而死亡组FiO2×PEEP无下降趋势。结论FiO2×PEEP对重症甲型H1N1流感病毒感染导致急性肺损伤病情评估及预后判断具有良好的临床价值．

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.

FiO_2及PEEP对腹腔镜行下宫颈癌根治术全麻患者P_(a-ET)CO_2的影响

目的评价不同吸入氧浓度(FiO2)和呼气末正压(PEEP)对腹腔镜下行宫颈癌根治术全麻患者动脉血-呼气末二氧化碳分压差[P(a-ET)CO2]的影响。方法将108例腹腔镜下行根治术的宫颈癌患者分为4组,每组27例:第1组给予FiO2(100%的纯氧)和0 mmHg的PEEP;第2组给予FiO2(100%的纯氧)和7.0 mmHg的PEEP;第3组给予FiO2(50%的纯氧)和0 mmHg的PEEP;第4组给予FiO2(50%的纯氧)和7.0 mmHg的PEEP,均在即时(T1)和30 min(T2)和60 min(T3)三个时间点时分别检测动脉血二氧化碳分压(PaCO2),呼气末二氧化碳分压(P ET CO2),P(a-ET)CO2。结果不同时间点组间比较:T1时1、2、3、4组间PaCO2、和P(a-ET)CO2相互比较差异无统计学意义(P>0.05);T2和T3时,1组与2组比较、3组与4组比较、1组与3组比较、2组与4组比较PaCO2和P(a-ET)CO2差异均有统计学意义(P<0.05)。结论 FiO2浓度较高时,同时一定要相应提高PEEP,则可以有效降低P(a-ET)CO2;PEEP较低时,同时一定要降低FiO2浓度,这样可以有效降低P(a-ET)CO2。

呼气末正压(PEEP)对于截石位开腹手术患者肺泡氧合功能的影响

目的研究呼气末正压(positive end-expiratory pressure,PEEP)对截石位开腹手术的全麻患者肺泡氧合功能的影响。方法选择40例采取截石位行开腹肠道手术的患者,随机分为A组(PEEP=0 cmH2O,n=20)和B组(PEEP=10 cmH2O,n=20);另选20例采取仰卧位行开腹肠道手术的患者作为对照组C组。所有患者均采用气管内插管全身麻醉、机械通气。比较3组患者在不同时点的动脉血氧分压(PaO2)和肺泡-动脉血氧分压差[P(A-a)DO2)]的变化。结果与C组相比,A组和B组在摆放体位后30 min PaO2出现下降,两组的氧分压变化百分比和肺泡-动脉氧分压差百分比与C组相比差异都具有显著统计学意义(P=0.00)。与A组相比,B组在加用10 cmH2O的PEEP后60 min,PaO2明显上升、P(A-a)DO2显著下降。结论截石位在一定程度上影响患者的肺泡氧合,而逐级上调PEEP值至10 cmH2O可以在不影响循环稳定的同时改善肺泡氧合功能。

持续高水平PEEP治疗肺内源性ARDS的临床价值研究

目的:探索持续高水平呼气末正压通气(PEEP)治疗肺内源性急性呼吸窘迫综合征(ARDS)的临床价值,为机械通气治疗ARDS提供依据。方法:收集70例肺内源性ARDS患者的临床资料,根据其PEEP是否>12cmH2O,分为观察组和对照组,比较两组患者的机械通气后PaO2和PaCO2的改善情况、气压伤发生率、住ICU时间、机械通气时间以及病死率。结果:两组患者机械通气0h、24h、72h后PaO2和PaCO2的改善情况无差异(P>0.05),1周后观察组PaO2为(159.41±29.16)、PaCO2为(44.51±10.23),对照组PaO2为(286.14±38.46)、PaCO2为(40.21±8.97),两组对比差异显著(P<0.05);观察组住ICU时间、平均机械通气时间和病死率为(11.78±9.86)d、(7.56±6.09)d、34.51%,对照组为(6.51±8.97)d、(3.98±5.76)d、18.76%,两组对比差异有统计学意义(P<0.05);观察组有3例气压伤,对照组无气压伤发生。结论:持续高水平PEEP治疗肺内源性ARDS患者并不能有效改善氧合,但延长患者住ICU时间,增加病死率。

ARDS合并脓毒症休克时机械通气早期PEEP对血压影响的研究

目的探讨机械通气呼气末正压(positive end-expiratory pressure,PEEP)对急性呼吸窘迫综合征(acute respiratorydistresssyndrome,ARDS)合并脓毒症时对循环的影响。方法 ARDS合并脓毒症休克患者(n=72)气管插管机械通气后立即观察PEEP对血压影响,PEEP分别调整在0、5、10 cmH_(2)O,稳定10 s后观察平均动脉压(mean artery pressure,MAP)、心率以及调整不同PEEP后的变化,同时记录经皮氧饱和度的变化。记录患者MAP维持在65~70mmHg时去甲肾上腺素剂量,按照去甲肾上腺素使用剂量分组,去甲肾上腺素≤0.5μg/(kg·min)分为1组,去甲肾上腺素>0.5μg/(kg·min)分为2组,比较2组PEEP对血压影响的差异。其中氧合指数<100设定为重度ARDS(n=26),重度ARDS患者增加PEEP可使MAP下降≥3 mm Hg设定为变化明显患者,将MAP变化明显患者设为A组(n=14),PEEP对血压影响不明显的为B组(n=12),A组机械通气第1个24 h PEEP维持在0~3 cmH_(2)O,B组第1个24hPEEP维持在8~10cmH_(2)O,比较2组机械通气24h后去甲肾上腺素用量,MAP、中心静脉压(centralvenouspressure,CVP)、氧合指数、脑利钠肽(brainnatriureticpeptide,BNP)、总入液量以及7d病死率。结果 ARDS合并脓毒症机械通气即刻增加PEEP后,MAP均有下降,1组与2组在机械通气前MAP比较差异无统计学意义(P>0.05);机械通气后设定PEEP在5 cmH_(2)O及10cmH_(2)O时1组与2组MAP变化比较差异有统计学意义,此时平均动脉压、血氧饱和度变化差异均有统计学意义(P<0.05)。A组第1个24 h后使用去甲肾上腺素剂量、CVP、BNP、液体输入量均小于B组(P<0.05),2组病死率比较差异无统计学意义(P>0.05)。结论 ARDS合并脓毒症患者机械通气时PEEP对血压有影响,血管活性药物使用剂量大者PEEP对血压影响更明显,增加PEEP降低血压同时降低血氧饱和度。ARDS机械通气时既要关注肺通气又要关注肺血循环。

What Does a First Order Model Tell Us about PEEP Wave Maneuvers?

Patients with acute respiratory distress syndrome (ARDS) are currently treated with a lung protective ventilation strategy and the application of positive end-expiratory pressure (PEEP), sometimes in combination with recruitment maneuvers. In this study, the respiratory system elastance and airway resistance of each breath before, during and after a specific recruitment maneuver (PEEP wave maneuver) were analyzed in two patient groups, ARDS and control group. A reduction of elastance after the maneuver was observed in ARDS patients. In addition, only healthy lungs exhibited a reduction of the elastance during the course of the maneuver, while the lungs of ARDS patients didn’t show that reduction of elastance. The capability of PEEP wave maneuvers to improve lung ventilation was shown and the dynamic behavior of the elastance after the maneuver was illustrated. Healthy lungs adapt faster to changes in mechanical ventilation than the lungs of ARDS patients.

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.

全麻诱导期呼气末正压通气对老年患者无通气期的影响

目的观察全麻诱导呼气末正压通气（PEEP）能否延长老年患者无通气期。方法选择ASAⅠ～Ⅱ级、年龄大于65岁全麻老年患者30例，随机分为PEEP组和对照组（C组），每组15例。所有患者自主呼吸存在时行面罩吸100％O2 5min。全麻诱导后，C组行控制呼吸（FiO2 100％，RR12次／分，VT 10ml／kg）5min，PEEP组应用C组相同的控制呼吸条件加PEEP6cm H2O 5min。无通气期为SpO2降至90％。记录无通气期时间，分别于入室后（T1）、面罩吸100％O2 5min时（T2）、控制呼吸5min时（T3）和SpO2降至90％时（T4）抽血样本行血气分析。结果PEEP组无通气期时间为（396±121）S，显著长于C组（305±107）S（P〈0．05）。动脉血气分析显示，两组患者T1、T2和T4时的PaO2和PaCO2相似，但T3时PEEP组的PaO2明显高于C组（P〈0．05），而PaCO2显著低于C组（P〈0．05）。结论全麻诱导应用PEEP，可增加氧储备，延长老年患者无通气期。