适当呼气末正压及不同通气模式对肝移植患者血流动力学和氧代谢动力学的影响

目的 寻找适宜的呼气末正压(PEEP),研究不同机械通气方式对肝移植术后患者血流动力学及氧代谢动力学的影响.方法 采用随机、单盲、交叉试验方法.选取11例背驮式肝移植术后呼吸机辅助通气患者为观察对象,经漂浮导管、桡动脉导管进行持续心排血量(CO)、平均肺动脉压(MPAP)、平均动脉血压(MABP)、中心静脉压(CVP)和气道压力监测.压力调节容量控制通气(PRVCV)的PEEP定为0、5、10和15 cm H2O(1 cm H2O=0.098 kPa),不同水平PEEP各用30 min;交替使用PRVCV和压力控制同步间歇指令通气加压力支持通气(PC-SIMV+PSV)各60 min;观察4种PEEP水平和两种通气模式下血流动力学和氧代谢动力学指标的变化.结果 不同水平PEEP时肝移植术后患者气道峰压、平均气道压、CVP及MPAP差异均有显著性,其中在PEEP为10 cm H2O和15 cm H2O时显著高于PEEP为0和5 cm H2O时;不同水平PEEP对pH、动脉血二氧化碳分压(PaCO2)、动脉血氧分压(PaO2)、动脉血氧饱和度(SaO2)、氧供给(DO2)、氧消耗(VO2)、氧摄取率(O2ER)均无明显影响.PRVCV模式时平均气道压明显低于PC-SIMV+PSV模式[(8.78±1.53)cm H2O比(11.64±3.30)cm H2O,P＜0.05];PRVCV模式时VO2虽低于PC-SIMV+PSV模式,但差异无显著性.两种通气模式对患者的其他血流动力学指标以及氧代谢动力学指标并无显著影响.结论 为减少对患者体循环及移植肝脏血液回流的影响,肝移植术后患者通气支持时宜选用5 cm H2O的低水平PEEP.PRVCV模式可作为肝移植术后患者呼吸支持和脱机过渡较为理想的通气模式.     

急性心源性肺水肿机械通气患者呼气末正压设定的临床研究

目的探讨急性心源性肺水肿(ACPE)时不同呼气末正压(PEEP)水平对血流动力学与肺参数的影响。方法39例呼吸衰竭机械通气患者根据心排血指数(CI)分为两组。观察心功能正常组(n=18,CI≥2.0L·min-1·m-2)与心功能低下组(n=21,CI<2.0L·min-1·m-2)在双水平气道正压通气(BIPAP)模式下不同PEEP水平对血流动力学〔心排血量(CO)、CI、肺毛细血管血流(PCBF)、中心静脉压(CVP)、外周血管阻力(SVR)〕、肺参数〔内源性呼气末正压(PEEPi)、气道峰压(Ppeak)、平均气道压(Pmean)、每分通气量(MV)、肺泡通气量(Vtalv)〕及经皮血氧饱和度(SpO2)、血压(BP)、心率(HR)等的变化。结果心功能正常组PEEP在0～13cmH2O(1cmH2O=0.098kPa)对血流动力学无明显影响,肺参数中Ppeak、PEEPi随着PEEP增高而相应增高,气道阻力(R)下降;心功能低下组随着PEEP变化SVR、CO、CI呈曲线性变化,以PEEP0～7cmH2O时CO、CI值较高而SVR较低,10～13cmH2OCO、CI值较低而SVR较高,对肺参数影响以PEEP5～7cmH2O时PEEPi较小。结论ACPE患者机械通气调节应结合血流动力学变化并兼顾肺机械参数变化,PEEP使用具有明显个体化倾向,以PEEP5～7cmH2O(一般<10cmH2O)为宜。     

不同呼气末正压设定对机械通气患者血流动力学及心功能的影响

目的探讨不同呼气末正压(PEEP)水平对机械通气患者血流动力学及心功能的影响。方法将39例呼吸衰竭进行机械通气的危重患者根据心排血指数(CI)分为两组。应用部分CO2重复呼吸法(NICO)连续监测血流动力学,观察心功能正常组(CI≥2.0L.min-1.m-2,n=18)与心功能低下组(CI<2.0L.min-1.m-2,n=21)在双水平气道正压通气(BIPAP)模式下0、5、7、10和13cmH2O(1cmH2O=0.133kPa)PEEP水平对血流动力学心排血量(CO)、CI、肺毛细血管血流(PCBF)、中心静脉压(CVP)、外周血管阻力(SVR)、肺机械参数内源性呼气末正压(PEEPi)、气道峰压(PIP)、平均气道压(Pmean)及脉搏血氧饱和度(SpO2)、血压(BP)、心率(HR)等的变化。结果心功能正常组随PEEP增加,CVP明显升高,CO、CI、SVR和PCBF无明显变化;心功能低下组随PEEP增加,CVP明显升高,CO、CI呈曲线变化,且明显下降,SVR下降后显著升高,PCBF明显减少;两组患者随PEEP增加,Pmean、PIP、PEEPi均相应增加,气道阻力明显下降。结论机械通气在相对容量恒定时,在0~13cmH2O的PEEP对正常心脏无明显影响,对衰竭心脏可明显减少右心前负荷、PCBF和左心室前负荷,设定适当PEEP可改善心功能。气道压力的变化与CO、CI的变化并非一致。     

Recruitment maneuver and high positive end-expiratory pressure improve hypoxemia in patients after pulmonary thromboendarterectomy for chronic pulmonary thromboembolism

OBJECTIVES: To investigate the effects of a recruitment maneuver and high positive end-expiratory pressure (PEEP) on oxygenation and hemodynamics in hypoxemic patients with pulmonary hypertension after pulmonary thromboendarterectomy for chronic pulmonary thromboembolism. DESIGN: Prospective, observational, clinical study. SETTING: A surgical intensive care unit in a national heart institute. PATIENTS: Fourteen consecutively admitted patients who developed acute lung injury (Pa(O2) <300 torr at F(IO2) 1.0) and pulmonary hypertension (mean pulmonary artery pressure >25 mm Hg) after pulmonary thromboendarterectomy for chronic pulmonary thromboembolism. INTERVENTIONS: The recruitment maneuver was an increase of PEEP to 30 cm H2O in one step for 1 min at F(IO2) 1.0. The level of pressure control ventilation during the recruitment maneuver was the same as before the maneuver. Subsequently, PEEP was decreased in 15-min intervals from 15 to 10, 5, and 0 cm H2O. MEASUREMENTS AND MAIN RESULTS: Hemodynamics and respiratory variables were analyzed before and during the recruitment maneuver and at each PEEP level. At F(IO2) 1.0, Pa(O2) increased from 240 +/- 62 torr to 470 +/- 83 torr at 15 cm H2O of PEEP and 469 +/- 75 torr at 10 cm H2O of PEEP after the recruitment maneuver (p < .001). At 15 cm H2O of PEEP, cardiac index decreased (from 2.7 +/- 0.6 at baseline to 2.2 +/- 0.3 L.min(-1).m(-2), p < .01) and mean blood pressure decreased (from 86 +/- 8 at baseline to 74 +/- 11 mm Hg, p < .05), but they returned to the baseline levels at 10 cm H2O of PEEP (2.5 +/- 0.4 L.min(-1).m(-2) and 83 +/- 9 mm Hg). There were no differences in mean pulmonary artery pressure at different levels of PEEP. CONCLUSIONS: In hypoxemic patients with pulmonary hypertension after pulmonary thromboendarterectomy for chronic pulmonary thromboembolism, oxygenation was improved by the recruitment maneuver followed by high PEEP. However, hemodynamics were transiently suppressed and overall oxygen delivery did not change.     

不同呼气末正压水平对绵羊急性呼吸窘迫综合征模型肺复张效果及血流动力学的影响

目的观察在绵羊急性呼吸窘迫综合征（ARDS）模型上利用控制性肺膨胀（SI）实施肺复张策略后不同呼气末正压（PEEP）水平对复张效果及血流动力学的影响，以找到理想的PEEP压力范围。方法12只绵羊在麻醉后，行纤维支气管镜温生理盐水肺泡灌洗复制ARDS模型，低流速法描记准静态压力-容积（P-V）曲线，寻找P-V曲线的上拐点（UIP），并以UIP下5cm H2O（1cm H2O=0．098kPa）作为SI的峰压进行肺复张，肺复张后根据不同的PEEP水平分为PEEP5、PEEP10、PEEP15、PEEP20组。记录肺复张后2h内的血流动力学参数及氧代谢指标，实验后进行肺组织活检，观察SI后不同的PEEP水平对血流动力学及复张效果的影响。结果PEEP5组和PEEP10组在复张后2h内对血流动力学没有影响，但PEEP5组氧合呈现下降趋势，病理显示肺泡组织仍轻度萎陷，伴灶性肺泡塌陷；PEEP≥15cm H2O时中心静脉压（cVP）明显升高，心排血指数（CI）明显降低，氧合指数、肺机械参数均较复张前明显改善并保持2h以上。结论ARDS肺复张后，PEEP设定在10-20cm H2O可以明显改善氧合，对正常心功能状态下的血流动力学影响并不显著。     

Liver blood flow during cardiac surgery

OBJECTIVE: Impairment of liver blood flow and, therefore, potentially liver function, has important short-term consequences because of the liver's key metabolic importance and role in drug metabolism. The objective of this study was to quantify the effect of cardiac surgery on liver blood flow from before the induction of anaesthesia to 24 hours postoperatively. METHOD: Ten patients with no history of liver impairment, moderate or good left ventricular function, and undergoing routine hypothermic coronary artery bypass graft surgery, were entered into the study. Liver blood flow was determined by the clearance of indocyanine green (ICG), expressed as a percentage disappearance rate (PDR). RESULTS: The mean baseline percentage disappearence rate (PDR) of indocyanine green (ICG) was 19.84 +/- 4.47%/min. This increased marginally to 20.42 +/- 6.67%/min following the induction of anaesthesia, but after 15 min of cardiopulmonary bypass, the PDR fell to 13.51 +/- 3.69%/min; this was significantly lower than all other PDRs measured throughout the study. Prior to extubation, the PDR increased again to 20.01 +/- 3.72%/ min, and this level was maintained at 12 hours (PDR 20.32 +/- 3.53%min) and 24 hours (PDR 20.51 +/- 2.27%/min). CONCLUSION: The induction of anaesthesia and positive pressure ventilation do not affect liver blood flow. Cardiopulmonary bypass at 30 degrees C is associated with a significant reduction in liver blood flow, which returns to normal within 4-6 hours of surgery and remains normal for up to 24 hours after surgery.     

Ventilation with end-expiratory pressure in acute lung disease

In 10 patients with severe, acute respiratory failure we studied the effects of positive end-expiratory pressure when intermittent positive pressure ventilation (IPPV) with inspired oxygen (F(IO2)) up to 0.5 failed to maintain arterial oxygen tension (P(aO2)) above 70 torr.Positive end-expiratory pressures (PEEP) of 0, 5, 10, and 15 cm H(2)O were applied for 30-min periods each and in random order. Blood gas exchange, lung volumes, compliance, and hemodynamics were studied at each level of PEEP. P(aO2) (F(IO2) = 1.0) rose linearly with elevation of PEEP, the mean increase being from 152 to 347 torr, or 13 torr/cm H(2)O PEEP. Mean functional residual capacity (FRC) was 1.48+/-0.78 liters at zero PEEP (i.e., IPPV) and the increase was essentially linear, reaching 2.37 liters at 15 cm H(2)O PEEP. P(aO2) and FRC showed a close correlation. Total and lung static compliance were greater during ventilation with high than with low levels of PEEP. The increase in P(aO2) correlated with the specific lung compliance. Dynamic lung compliance decreased progressively with rising levels of PEEP except for an increase with 5 and 10 cm H(2)O PEEP in patients with initial values of 0.06 liter/cm H(2)O or higher. Cardiac index fell in some patients and rose in others and there was no correlation of mean cardiac index, systemic blood pressure, or peripheral vascular resistance with level of PEEP. The most probable explanation for the effect of PEEP on P(aO2) and compliance is recruitment of gas exchange airspaces and prevention of terminal airway closure.     

Gastric intramucosal PCO2 and pH variability in ventilated critically ill patients

OBJECTIVE: Gastric intramucosal PCO2 (PiCO2) and pH (pHi) are currently used as indices of the adequacy of splanchnic perfusion and as end points to guide therapeutic intervention. However, little is known about their spontaneous variability over time. The present study was designed to define the magnitude of spontaneous variability of PiCO2 and pHi in sedated medical intensive care unit (ICU) patients using an automated recirculating air tonometer and to test whether high-level positive end-expiratory pressure (PEEP) or inverse inspiratory/expiratory (I:E) ratio ventilation resulted in a greater variability than low PEEP with conventional I:E ratio ventilation. DESIGN: Prospective study. SETTING: Medical ICU in a tertiary medical center. PATIENTS: Twenty-three acute respiratory failure patients. INTERVENTIONS: After being sedated, patients were randomized to undergo pressure control ventilation at the following three settings: A, high PEEP (15 cm H2O) with conventional I:E ratio (1:2), and B, low PEEP (5 cm H2O) with inverse I:E ratio (2:1) alternately, and then C, low PEEP (5 cm H2O) with conventional I:E ratio (1:2). Each ventilation setting period lasted 1 hr. MEASUREMENTS AND MAIN RESULTS: The PiCO2 and pHi were measured at baseline (time 0), and at 15, 30, 45, and 60 mins thereafter. The corresponding coefficients of variation (CVs) of PiCO2 for overall pooled group and settings A, B, and C were 4.0%, 4.4%, 3.4%, and 4.2%, respectively. The corresponding CVs of pHi for overall pooled group and settings A, B, and C were 0.36%, 0.37%, 0.33%, and 0.4%, respectively. Analysis of variance showed no significant difference in the CVs of PiCO2 or pHi between the three settings. The 95% confidence interval is approximately +/-8% variability for PiCO2 and +/-0.7% variability for pHi. CONCLUSIONS: In critically ill medical ICU patients with stable hemodynamics, the spontaneous variability of PiCO2 or pHi are not substantial. High PEEP (15 cm H2O) and inverse ratio ventilation (2:1), which does not change the cardiac output or hemodynamics, does not contribute to increased spontaneous variability in PiCO2 or pHi.     

Does PEEP impair the hepatic outflow in patients following liver transplantation?

Objective Evaluation of the impact of end-expiratory pressure (PEEP) ventilation on venous liver outflow, portal vein, and hepatic artery flows as well as systemic hemodynamics in patients following liver transplantation (LT).Design Prospective, interventional patient study.Setting University hospital intensive care unit.Patients 65 consecutive patients after LTInterventions All patients were intubated and mechanically ventilated with biphasic positive airway pressure (BIPAP). The effects of three levels of PEEP (0, 5, and 10 mbar) applied at random order on hepatic inflow and outflow were studied in the immediate postoperative period.Measurement and results Central venous-, arterial pressure, and cardiac index was recorded from every patient at three different PEEP levels (0, 5, and 10 mbar). Simultaneously, flow velocities in the hepatic-, portal vein, and hepatic artery were determined by Doppler ultrasound. PEEP of 10 mbar significantly increased central venous pressure in comparison with zero PEEP. Mean arterial pressure and cardiac index was not influenced. Hepatic inflow and outflow of the transplanted livers were not impaired by any of the used PEEP levels.Conclusions BIPAP ventilation with PEEP levels up to 10 mbar does not affect systemic hemodynamics. Furthermore, neither venous outflow nor portal venous or hepatic artery inflow of the liver are impaired at PEEP levels up to 10 mbar immediately following liver transplantation. Although these results suggest that PEEP ventilation up to 10 mbar does not affect liver hemodynamics, further studies are needed to determine whether these findings could be confirmed for a longer ventilation period with PEEP.     

The effect of positive end-expiratory pressure during partial liquid ventilation in acute lung injury in piglets.

OBJECTIVES: To investigate the effects of positive end-expiratory pressure (PEEP) application during partial liquid ventilation (PLV) on gas exchange, lung mechanics, and hemodynamics in acute lung injury. DESIGN: Prospective, randomized, experimental study. SETTING: University research laboratory. SUBJECTS: Six piglets weighing 7 to 12 kg. INTERVENTIONS: After induction of anesthesia, tracheostomy, and controlled mechanical ventilation, animals were instrumented with two central venous catheters, a pulmonary artery catheter and two arterial catheters, and an ultrasonic flow probe around the pulmonary artery. Acute lung injury was induced by the infusion of oleic acid (0.08 mL/kg) and repeated lung lavage procedures with 0.9% sodium chloride (20 mL/kg). The protocol consisted of four different PEEP levels (0, 5, 10, and 15 cm H2O) randomly applied during PLV. The oxygenated and warmed perfluorocarbon liquid (30 mL/kg) was instilled into the trachea over 5 mins without changing the ventilator settings. MEASUREMENTS AND MAIN RESULTS: Airway pressures, tidal volumes, dynamic and static pulmonary compliance, mean and expiratory airway resistances, and arterial blood gases were measured. In addition, dynamic pressure/volume loops were recorded. Hemodynamic monitoring included right atrial, mean pulmonary artery, pulmonary capillary wedge, and mean systemic arterial pressures and continuous flow recording at the pulmonary artery. The infusion of oleic acid combined with two to five lung lavage procedures induced a significant reduction in PaO2/FI(O2) from 485 +/- 28 torr (64 +/- 3.6 kPa) to 68 +/- 3.2 torr (9.0 +/- 0.4 kPa) (p < .01) and in static pulmonary compliance from 1.3 +/- 0.06 to 0.67 +/- 0.04 mL/cm H2O/kg (p < .01). During PLV, PaO2/FI(O2) increased significantly from 68 +/- 3.2 torr (8.9 +/- 0.4 kPa) to >200 torr (>26 kPa) (p < .01). The highest PaO2 values were observed during PLV with PEEP of 15 cm H2O. Deadspace ventilation was lower during PLV when PEEP levels of 10 to 15 cm H2O were applied. There were no differences in hemodynamic data during PLV with PEEP levels up to 10 cm H2O. However, PEEP levels of 15 cm H2O resulted in a significant decrease in cardiac output. Dynamic pressure/volume loops showed early inspiratory pressure spikes during PLV with PEEP levels of 0 and 5 cm H2O. CONCLUSIONS: Partial liquid ventilation is a useful technique to improve oxygenation in severe acute lung injury. The application of PEEP during PLV further improves oxygenation and lung mechanics. PEEP levels of 10 cm H2O seem to be optimal to improve oxygenation and lung mechanics.     

急性心源性肺水肿机械通气治疗效果及对血流动力学的影响

目的研究急性心源性肺水肿(ACPE)机械通气治疗方法,比较持续气道正压成比例压力支持(CPAPPPS)、持续气道正压压力支持通气(CPAPPSV)两种模式对血流动力学的影响。方法77例ACPE患者进行无创、有创机械通气治疗,对其中机械通气时间超过24h的61例患者在有创机械通气开始与低辅助通气时用部分CO2重复呼吸法(无创心排血量,NICO)监测血流动力学变化,在药物干预下,对照研究两种模式下血流动力学变化。结果61例ACPE患者中33例行无创机械通气,成功24例(72.7%),33例有创机械通气(5例为无创转为有创机械通气),11例失败。控制通气应用双水平气道正压/压力支持通气(BIPAP/PSV),高水平压力(Phigh)16～24cmH2O(1cmH2O=0.098kPa),高水平压力时间(Thigh)1.5s,呼气末正压(PEEP)6～15cmH2O,吸入氧浓度(FiO2)0.5;有创机械通气撤机成功患者心排血量(CO)和心排血指数(CI)较有创机械通气撤机失败患者明显改善,低辅助通气采用PPS模式患者的CO和CI较采用PSV模式患者改善更明显(P均<0.001),有创机械通气撤机失败患者在药物干预下仍CI<1.5L·min-1·m-2。结论对ACPE患者应在血流动力学监测下进行药物干预及无创/有创机械通气治疗,宜采用压力控制模式,个体化调节PEEP,一般6～15cmH2O,依据临床情况尽快过渡到自主通气模式,对撤机困难者可应用CPAPPPS模式。     

Phase-related changes in right ventricular cardiac output under volume-controlled mechanical ventilation with positive end-expiratory pressure.

OBJECTIVE: To examine determinants of right ventricular function throughout the ventilatory cycle under volume-controlled mechanical ventilation with various positive end-expiratory pressure (PEEP) stages. DESIGN: Prospective observational animal pilot study. SETTING: Animal research laboratory at a university hospital. SUBJECTS: Eight healthy swine under volume- controlled mechanical ventilation. INTERVENTIONS: Flow probes were implanted in eight swine in order to continuously measure blood flow in the pulmonary artery and inferior vena cava. After a recovery phase of 14 days, the swine were subjected to various PEEP stages (0, 5, 10 cm H2O) during volume-controlled positive pressure ventilation. MEASUREMENTS AND MAIN RESULTS: Continuous flow measurement took place in the pulmonary artery and inferior vena cava. Data on standard hemodynamic parameters were additionally acquired. Respiration-phase-specific analysis of right ventricular cardiac output and of additional hemodynamic function parameters followed, after calculation of mean values throughout five respiration cycles. PEEP at 5 cm H2O led to significant decreases in inferior vena cava flow (4.1%), and in right ventricular cardiac output (5.2%); the respective decreases at PEEP 10 cm H2O were 13.9% and 18.3%. In the inspiration phase at PEEP 10 cm H2O, results revealed an overproportionally pronounced decrease in comparison with the expiration phase in inferior vena cava flow (-24.6% vs. -10%) and right ventricular cardiac output (-35% vs. -13.5%). This phenomenon is presumably caused by a PEEP-related increase in mean airway pressure by the amount of 10.7 cm H2O in inspiration. CONCLUSIONS: Increases in PEEP during volume-controlled mechanical ventilation leads to respiration-phase-specific reduction of right ventricular cardiac output, with a significantly pronounced decrease during the inspiration phase. This decrease in cardiac output should be taken into particular consideration for patients with already critically reduced cardiac output.     

Open lung ventilation does not increase right ventricular outflow impedance: An echo-Doppler study

OBJECTIVE: Ventilation according to the open lung concept (OLC) consists of recruitment maneuvers, followed by low tidal volume and elevated positive end-expiratory pressure (PEEP). Elevated PEEP is associated with an increased right ventricular afterload. We investigated the effect of OLC ventilation on right ventricular outflow impedance during inspiration and expiration in patients after cardiac surgery using transesophageal echo-Doppler. DESIGN: A prospective, single-center, crossover, randomized, controlled clinical study. SETTING: Cardiothoracic intensive care unit of a university hospital. PATIENTS: Twenty-eight patients scheduled for elective cardiac surgery with cardiopulmonary bypass. INTERVENTIONS: In the intensive care unit, each patient was ventilated for approximately 30 mins according to both OLC and conventional ventilation. During OLC ventilation, recruitment maneuvers were applied until PaO2/FiO2 was >375 torr (50 kPa); during conventional ventilation no recruitment maneuvers were performed. MEASUREMENTS AND MAIN RESULTS: Transesophageal echo-Doppler measurements were performed at end-inspiration and end-expiration in a steady-state condition, 20 mins after initiation of a ventilation strategy. Mean acceleration of flow was determined in the long axis of the pulmonary artery in a transverse axis view. During OLC ventilation, a total PEEP of 14 +/- 4 cm H2O was applied vs. 5 cm H2O during conventional ventilation. Mean acceleration during expiration was comparable between groups. During inspiration, OLC ventilation did not cause a decrease of mean acceleration compared with expiration, whereas this did occur during conventional ventilation. CONCLUSIONS: Despite the use of elevated PEEP levels, ventilation according to OLC does not change right ventricular outflow impedance during expiration and decreases right ventricular outflow impedance during inspiration.     

Optimization of oxygen transport in mechanically ventilated newborns using oximetry and pulsed Doppler-derived cardiac output

In respiratory distress syndrome (RDS), PEEP improves arterial oxygenation but may impair cardiac output. The effects of PEEP on gas exchange and hemodynamics were studied in 12 mechanically ventilated newborns in the acute phase of RDS. Stepwise increase in PEEP resulted in both a) a progressive increase in PaO2 and transcutaneous oxyhemoglobin saturation, and b) a depression of pulsed Doppler-measured cardiac output that was statistically significant at 9 cm H2O PEEP. Thus, averaged systemic oxygen delivery (DO2) was maintained with improved arterial oxygenation up to 6 cm H2O PEEP. Further increase in PEEP induced a significant fall in DO2. No variation was observed in heart rate and mean arterial pressure. The combined use of oximetry and pulsed Doppler echocardiography enables noninvasive optimization of mechanical ventilation and PEEP during the clinical course.     

Perioperative indocyanine green clearance is predictive for prolonged intensive care unit stay after coronary artery bypass grafting - an observational study

Introduction  

During cardiac surgery with cardiopulmonary bypass (CPB) haemodilution occurs. Hepatic dysfunction after CPB is a rare, but serious, complication. Clinical data have validated the plasma-disappearance rate of indocyanine green (PDR ICG) as a marker of hepatic function and perfusion. Primary objective of this analysis was to investigate the impact of haemodilutional anaemia on hepatic function and perfusion by the time course of PDR ICG and liver enzymes in elective CABG surgery. Secondary objective was to define predictors of prolonged ICU treatment like decreased PDR ICG after surgery.     

应用超声心动技术分析机械通气对左室功能的影响

目的 应用超声心动技术评价机械通气时呼气末正压(PEEP)对左室功能的影响.方法 将36例呼吸衰竭行机械通气的危重患者按心排血指数(CI)分为两组.应用彩色超声心动技术检测患者不同PEEP(0、4、7、10、14 cm H2O,1 cm H2O=0.098 kPa)时左室功能.结果 心功能正常组(CI≥2.0 L·min-1·m-2,17例)随PEEP增加,代表左室收缩功能的指标左室收缩期末容积(LVESV)、左室舒张期末容积(LVEDV)、心排血量(CO)、射血分数(EF)未见明显变化,代表左室舒张功能的指标二尖瓣口舒张早期充盈速度(E)、舒张晚期充盈速度(A)、E/A比值、舒张早期运动速度(Ve)、舒张晚期运动速度(Va)、Ve/Va比值及左室舒张期末压(LVEDP)未见明显改变.心功能异常组(CI＜2.0 L·min-1·m-2,19例)随PEEP增加到10 cm H2O和14 cm H2O时,与PEEP 0比较,左室收缩功能指标LVESV(ml:10 cm H2O时21.2±1.2比18.2±1.4)明显升高,LVEDV(ml:42.6±2.4、40.1±1.9比44.5±3.5)、CO(L:2.3±0.6、2.1±0.7比2.6±0.7)、EF(0.40±0.02、0.39±0.02比0.42±0.02)明显下降(均P＜0.05);左室舒张功能指标A(cm/s:88.5±15.2、93.2±18.7比76.0±9.0)、Va(cm/s:14.3±4.5、15.8±5.3比12.0±1.2)、LVEDP[mm Hg(1 mm Hg=0.133 kPa):15.3±2.0、16.9±2.8比10.7±2.5]明显升高,E(cm/s:73.6±15.4、63.2±16.4比83.1±20.1)、E/A比值(0.83±0.10、0.68±0.20比1.10±0.20)、Ve(cm/s:11.7±1.8、10.4±2.0比13.8±2.8)、Ve/Va比值(0.8±0.1、0.6±0.2比1.2±0.2)明显下降(均P＜0.05).结论 与机械通气时,0～14 cm H2O的PEEP对正常心脏无明显影响;心功能低下患者,当PEEP≥10 cm H20时可明显降低左室舒张和收缩功能;设定最佳PEEP可改善左室功能.

Abstract：

Objective To study the effects of different positive end-expiratory pressure (PEEP) levels on the heart function of patients undergoing mechanical ventilation (MV) with echocardiography. Methods Thirty-six critical patients with respiratory failure undergoing MVwere divided into two groups according to the cardiac index (CI). The left heart function was measured with echocardiography at different PEEP levels (0, 4, 7, 10, 14 cm H2O, 1cm H2O = 0. 098 kPa). Results In the normal cardiac function group (CI≥2. 0 L · min-1 · m-2, n=17), an increase in PEEP had no significant effects on left ventricular systolic function [left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV),cardiac output (CO), ejection fraction (EF)]. The increase in PEEP had no significant effect on left ventricular diastolic function [mitral early diastolic filling velocity (E), late diastolic filling velocity (A), the ratio of E/A, early diastolic velocity (Ve), late diastolic velocity (Va), the ratio of Ve/Va, left ventricular end-diastolic pressure (LVEDP)]. In the poor cardiac function group (CI＜ 2. 0 L · min-1 · m-2, n = 19),when PEEP was increased to 10 cm H2O and 14 cm H2O, compared with PEEP 0, left ventricular systolic function indexes including LVFSV (ml: 21.2±1.2 vs. 18. 2±1.4 as 10 cm H2O) was significantly higher,i.e. LVEDV (ml: 42. 6±2. 4, 40. 1±1.9 vs. 44. 5±3. 5), CO (L: 2. 3±0. 6, 2. 1±0. 7 vs. 2. 6±0. 7), EF (0. 40±0. 02, 0. 39±0. 02 vs. 0. 420. 02) were decreased (all P＜0. 05); left ventricular diastolic function indexes including A (cm/s: 88.5±15.2, 93.2±18.7 vs. 76.0±9.0), Va (cm/s: 14.3±4.5, 15.8±5.3vs. 12.0±1.2), LVEDP [mmHg (1 mm Hg=0.133 kPa):15.3±2.0, 16.9±2.8 vs. 10.7±2.5] were significantly higher; E (cm/s: 73. 6±15.4, 63.2±16.4 vs. 83.1±20.1), the ratio of E/A (0. 83±0. 10,0.68±0.20 vs. 1.10±0.20), Ve (cm/s: 11.7±1.8, 10.4±2.0 vs. 13.8±2.8), the ratio of Ve/Va (0. 8±0. 1, 0. 6±0. 2 vs. 1.2±0. 2) were decreased (all P＜0. 05). Conclusion Under the same condition of MV, change in PEEP levels (0 - 14 cm H2O) do not produce any obvious effect in the normal cardiac function group, on the other hand when PEEP≥10 cm H2O left heart function is significantly dowered in the poor cardiac function group. Optimial PEEP may improve the cardiac function.     

呼气末正压对机械通气患者中心静脉压及髂总静脉压的影响

目的 观察不同呼气末正压(PEEP)水平对机械通气患者中心静脉压(CVP)和髂总静脉压(CIVP)及两者相关关系的影响.方法 将2007年2-8月收住重症加强治疗病房(ICU),无心肺疾患、循环稳定、无腹胀、无凝血功能异常,需机械通气的20例成年患者列为观察对象,采用自身对照,随机加用0、5和10 cm HzO(1 am H2O=0.098 kPa)PEEP,评估在此条件下,CVP、CIVP和两者压力阶差变化及其与机械通气压力变化间的相关关系.结果 CVP及CIVP随PEEP增加而增高,差异有统计学意义(P0.05);CVP及CIVP与机械通气各压力值变化呈正相关,但CVP及CIVP仅与平均气道压(Pmean)及PEEP有统计学意义(CVP与PEEP r=0.751,CIVP与PEEP r=0.685,CVP与Pmean r=0.634,CIVP与Pmena r=0.603,P均相似文献   

Positive end-expiratory pressure does not compromise myocardial contractility in myocardial ischemia/reperfusion

Therapy for severe myocardial ischemia/reperfusion sometimes necessitates intermittent positive pressure ventilation, which may impair left ventricular function by reduction of ventricular loading. It is unknown today whether positive airway pressure also affects contractile force after myocardial ischemia/reperfusion. The authors tested whether positive end-expiratory pressure (PEEP) impairs myocardial contractility in acute ischemic heart failure. In 11 anesthetized mechanically ventilated pigs (28 +/- 3 kg), cardiac output (CO, aortic flow probe), load-independent parameters of left ventricular contractility (conductance method: preload recruitable stroke work [PRSW] and end-systolic elastance [E(es)]) and preload (end-diastolic volume [EDV] conductance) were assessed before and after myocardial ischemia and reperfusion (left anterior descending artery occlusion, 60 min). Data were taken during PEEP 0, 5, and 10 cm H2O. Before myocardial ischemia, both PEEP 5 and 10 cm H2O reduced CO (P < 0.05) because of a reduction of EDV (P < 0.05, PEEP 10 cm H2O). The PRSW remained unchanged (not significant [NS]) and E(es) increased (P < 0.05, PEEP 10 cm H2O). After myocardial ischemia/reperfusion, CO and PRSW, but not E(es) (NS), deteriorated markedly. At the same time, PEEP 10 cm H2O reduced CO (P < 0.05) and, slightly, EDV (NS). Now, both PRSW (P < 0.05, PEEP 5 cm H2O) and E(es) (P < 0.05, PEEP 10 cm H2O) improved upon ventilation with PEEP. In our model, the administration of PEEP impaired global left ventricular function before and after myocardial ischemia/reperfusion. The observed impairment is not attributable to compromised contractility.     

Acoustic effects of positive end-expiratory pressure on normal lung sounds in mechanically ventilated pigs

Computerized lung sounds analysis offers a new technique to monitor regional ventilation during spontaneous breathing. The purpose of the present study was to assess the acoustic behaviour of the respiratory system in healthy pigs during mechanical ventilation when a positive end-expiratory pressure (PEEP) is applied. Lung sounds were recorded during mechanical ventilation and different PEEP levels of 0, 5, 10, 15 and 20 cm H(2)O were applied. The increase in end-expiratory lung volume (EELV) related to the PEEP application was also measured and the correlation between changes in EELV (DeltaEELV) and sound amplitude (DeltaA) was examined. The amplitude of normal lung sounds was reduced by application of PEEP >or=10 cm H(2)O (P<0.05). The increase in PEEP from 0 to 20 cm H(2)O reduced the acoustic energy of lung sounds recorded at ZEEP by 0.3 dB (PEEP 5), 2 dB (PEEP 10), 5 dB (PEEP 15) and 7 dB (PEEP 20), which corresponds to 1%, 6%, 14% and 21% in acoustic attenuation, respectively. The variations in DeltaA correlated with changes in lung volume (P<0.05) and with changes in compliance of the respiratory system (P<0.05), but were not correlated with changes of the resistance of respiratory system. The frequency analysis showed a downward shifting of the spectra at frequencies between 150 and 600 Hz for PEEP levels >or=10 cm H(2)O and frequencies between 75 and 600 Hz for PEEP levels >or=15 cm H(2)O. The application of increasing levels of PEEP reduced the amplitude and changed the spectral characteristics of normal lung sounds.     

Two-dimensional echocardiographic evaluation of inferior vena cava, right ventricle, and left ventricle during positive-pressure ventilation with varying levels of positive end-expiratory pressure

The effects of intermittent positive-pressure ventilation (IPPV) with 0, 10, and 15 cm H2O of PEEP on inferior vena cava (IVC), right and left ventricular length and septal-lateral dimensions, and cardiac output were examined in 19 patients with respiratory failure using two-dimensional echocardiography. In five patients, cardiac output was also obtained by the thermodilution technique. As PEEP was increased, IVC dimensions increased during both inspiration and expiration, and the IVC collapsibility index decreased. This indicated an increase in venous stasis and decrease in venous return to the right atrium. Increasing PEEP was associated with progressive decreases in cardiac output, and length and septal-lateral dimensions of both ventricles. The decreased cardiac output during IPPV with 10 and 15 cm H2O PEEP may be due to the decreased venous return and ventricular filling. Cardiac output determined by echocardiography was correlated closely to that by the thermodilution technique.