呼吸末正压通气治疗急性肺损伤的临床研究

目的 :对急性肺损伤 (ALI)病人进行呼吸机辅助呼吸比较不同值的呼气末正压(PEEP)对ALI氧供及氧耗的影响及其副作用。方法 :14例确诊为ALI病人在同一呼吸机参数下(不同PEEP)选择PEEP 0、 5、 10、 15、 2 0cmH2 O条件下监测其血流动力学、肺力学以及氧供氧耗的变化。结果 :(1)随着PEEP的增加气道峰值压 (pip)随之增加 ,肺顺应性在PEEP 0～15cmH2 O时逐渐增加 ,当PEEP大于 15cmH2 O反而下降 ;(2 )PEEP在 0～ 15cmH2 O时心输出量(CO)变化不大 ,差异无显著性 (P >0 0 5 ) ,在PEEP大于 15cmH2 O时CO明显下降 ,差异有显著性 ,P <0 0 5 ;(3)PEEP在一定范围内增加 ,氧供及氧耗也随之增加 ,当PEEP大于 15cmH2 O时氧供及氧耗反而下降。结论 :ALI的呼吸机治疗过程中 ,PEEP在 10～ 15cmH2 O时可获得最大的氧供最小的副作用     

氧合指数与肺静态顺应性对急性肺损伤机械通气的判定价值

目的　对14例ALI患者采用低潮气量加呼气末正压(PEEP)通气的患者行氧合指数(PaO2/FiO2)和肺静态顺应性(Cst)监测,了解此判定标准的临床意义。方法　最初采用A/C通气(VT8ml/kgfl6次/minflow34L/min),并逐渐增加PEEP(5、10、15、20cmH2O),每种方式30分钟,4种方式FiO2不变。利用Swan-Ganz导管获得血液动力学和氧代谢参数。结果　PaO2/FiO2随着PEEP的增高而增加,Cst在PEEP10～15cmH2O时,可稳定在336±83ml/cmH2O水平,当进一步增加时,Cst和DO2也进一步下降,PIP增加。结论　对ALI采用低潮气量加呼气末正压通气的患者,监测PaO2/FiO2和Cst有助于最佳PEEP的选择和获得最大的DO2。     

吸入氧浓度对急性呼吸窘迫综合征诊断的影响

目的 探讨吸入氧浓度(FiO2)对急性呼吸窘迫综合征(ARDS)患者氧合指数(P/F=PaO2/FiO2)的影响及其临床意义.方法 采用前瞻性研究,选择16例PEEP≥5 cmH2O(1 mmHg=0.098 kPa)时P/F为100～200 mmHg(1 mmHg=0.133 kPa)需机械通气的ARDS患者,实施肺复张(BIPAP,PH 40 cmH2O,40 s)后维持基线通气,稳定30 min后,按随机顺序设定FiO2为0.5,0.6,0.7,0.8,0.9和1.采用SPSS 13.0统计软件比较不同FiO2下患者呼吸力学、血气及血流动力学各指标的变化及其相关性.结果 随FiO2增加P/F逐渐增加,FiO2增加至0.7以上,P/F增加更加明显,FiO2分别为0.5和1.0两组进行比较,P/F的变化为24.70%±23.36%;6例(37.5%)患者FiO2为0.5时P/F＜200,而FiO2为1.0时P/F＞200;FiO2与Qs/Qt呈负相关(r=-0.390,P=0.027),吸入氧浓度越高,分流越小,FiO2为0.5和1.0时△Qs/Qt与△P/F呈正相关(r=0.82,P=0.005).结论 吸入氧浓度影响ARDS患者的氧合指数,从而可能影响ARDS的诊断,这与其对肺内分流的影响有关.

Abstract：

Objective To investigate the influence of inspired oxygen fraction (FiO2) on the ratio of PaO2/FiO2(P/F) during the implementation of lung protective ventilation strategy in patients with acute respiratory distress syndrome(ARDS) in order to unravel its clinical significance. Method This was a prospective study of 16 selected patients with ARDS treated with mechanical ventilation ( MV ) to get ratio of P/F in range of 100 to 200 by PEEP≥5 cmH2O and high inspired oxygen. After lung recruitment maneuvers by BiPAP with high pressure (PH) of 40 cmH2O for40 s, the MV was maintained the basic requirement for stabilizing the patients for 30 minutes. A series of FiO2 were set at fractions of 0.5,0.6,0.7,0.8,0.9 and 1in random sequence, and the changes of respiratory mechanics, blood gas and hemodynamics under the different concentrations of FiO2 were analyzed by using SPSS version 13.0 software. Results ( 1 ) The ratio of P/F increased as FiO2 increased, and it's significant as FiO2 increased to 0.7 or above. As the fractions of FiO2 were set at 0.5 and 1. O, the ratios of P/F changed in 24.70% ± 23.36% respectively. ( 2 ) Of them,6 patients ( 37.5% ) treated with FiO2 set at 0.5 had the ratio of P/F ＜ 200, and the fraction of FiO2 was increased to 1.0, the P/F ＞ 200. (3) FiO2 and Qs/Qt were negatively correlated ( r = - 0.390, P = O. 027 ),the higher inspired oxygen fraction, the lower shunt. When the fractions of FiO2 were set at 0.5 and 1.0 ,there was a positive correlation between △Qs/Qt and △P/F( r = 0.82, P = 0.005 ). Conclusions The inspired oxygen fraction affects the ratio of P/F, which may be resulted from shunt and it may influence the diagnosis of ARDS.     

最佳氧合法导向的PEEP对ARDS绵羊血流动力学和气体交换的影响

目的探讨最佳氧合法导向的呼气末正压(PEEP)对急性呼吸窘迫综合征(ARDS)绵羊血流动力学和气体交换的影响。方法肺泡灌洗法复制绵羊ARDS模型(n=6),在充分肺复张的基础上,利用最佳氧合法滴定最佳PEEP,并维持通气2 h。观察基础状态(PEEP 5 cmH2O)、ARDS模型稳定(PEEP 5 cmH2O)和最佳PEEP维持通气2 h的血流动力学、气体交换和呼吸力学变化。结果最佳氧合法滴定的最佳PEEP为(18±2)cmH2O。与ARDS模型比较,最佳PEEP维持通气期间心率(HR)、平均动脉压(MAP)、心脏指数(CI)、每搏指数(SVI)、中心静脉压(CVP)、平均肺动脉压(MPAP)、肺动脉嵌顿压(PAWP)和肺循环阻力指数(PVRI)差异无统计学意义(P>0.05),CVP、MPAP、PAWP和PVRI较基础状态明显升高(P<0.05)。与ARDS模型稳定时比较,最佳PEEP维持通气期间动脉血二氧化碳分压(PaCO2)明显降低(P<0.05),氧合指数(PaO2/FiO2)和氧输送(DO2I)显著升高(P<0.05),肺内分流率(Qs/Qt)明显改善(P<0.05),且PaCO2、PaO2/FiO2、DO2I和Qs/Qt均接近基础状态(P>0.05)。与ARDS模型稳定时比较,最佳PEEP维持通气期间的平均气道压(Pm)明显升高(P<0.05)、平台压力(Pplat)无明显变化(P>0.05)、肺动态顺应性(Cdyn)明显增加(P<0.05)。结论最佳氧合法导向的PEEP能有效地减少ARDS绵羊的肺内分流、改善氧合和肺顺应性,对血流动力学无明显影响。     

呼气末正压对急性呼吸窘迫综合征绵羊内脏器官灌注的影响

目的　观察呼气末正压 (PEEP)对急性呼吸窘迫综合征 (ARDS)绵羊内脏器官灌注的影响。方法　内毒素 (LPS)静脉注射复制绵羊ARDS模型 ,维持心脏最佳前负荷 ,依次调整PEEP为 5、 10、15cmH2 O ,观察不同PEEP对血流动力学、呼吸力学、氧代谢及内脏器官灌注的影响。结果　与基础值(PEEP =0cmH2 O)比较 ,PEEP 5、 10、 15cmH2 O组心率、平均动脉压、肺动脉压、中心静脉压、肺动脉嵌顿压及心输出量差异无显著性意义 ,但PEEP 10、 15cmH2 0组动脉氧分压和动脉氧饱和度均同步明显增加 ,氧合指数也从 ( 10 4 6 4± 2 5 2 1)mmHg提高到 ( 136 2 5± 38 5 4 )和 ( 135 37± 37 5 6 )mmHg (P <0 0 5 ) ,PEEP 5、 10、 15cmH2 O组肠黏膜pH值 (pHi)与基础比较 ,差异无显著性意义 (P >0 0 5 )。各组肠黏膜与动脉二氧化碳分压差 (Pg aCO2 )也无明显差异。全身氧输送、血乳酸无明显改变 (P >0 0 5 )。与基础值比较 ,PEEP各组平均气道压、气道平台压及肺动态顺应性显著增加 ,PEEP 15cmH2 O组气道峰压也明显增高(P <0 0 5 )。结论　维持心脏最佳前负荷状态下 ,血流动力学和氧输送可保持稳定 ,PEEP在 15cmH2 O以下对ARDS绵羊内脏灌注无明显影响     

密闭式吸痰结合高氧法和/或肺泡复张术对ARDS小猪心率、血压的影响

目的探讨高氧法和/或肺泡复张术在密闭式吸痰时对急性呼吸窘迫综合征(ARDS)小猪心率、血压的影响。方法16只小猪给予清洁剂(1.370±0.637)mg/kg气管注入制作ARDS模型。随机将模型猪分为呼气末正压(PEEP)5cmH2O和10cmH2O2组,每组8只。每只小猪按随机顺序分别采用单纯法、高氧法、复张法、结合法4种密闭式吸痰法吸痰,观察各组吸痰前1min心率、血压的变化,分别与吸痰后1,3,5,10min的结果进行比较。结果在PEEP5cmH2O组,4种方法吸痰后1min,ARDS小猪收缩压(SBp)均下降(P<0.05),单纯密闭式吸痰法在吸痰后10minSBp仍低于吸痰前基线水平(P<0.05);在PEEP10cmH2O组,4种方法吸痰后SBp也均下降,但与吸痰前基线水平比较差异无统计学意义(P>0.05)。各种方法在吸痰前后ARDS小猪心率及舒张压变化无统计学意义。结论不论在PEEP5cmH2O还是10cmH2O水平,各种密闭式吸痰方法对ARDS小猪心率、血压的影响趋势均一致,都可引起血压下降,PEEP5cmH2O时所引起的血压下降持续时间较长,因此,吸痰时更需要采取有效辅助措施以逆转对机体的不利影响。     

静态肺压力-容积曲线确定最佳呼气末正压的比较性试验研究

目的　通过静态肺压力 -容积曲线 (P -Vcurve)法和最大氧分压 (PEEPtrail)法确定不同PEEP对急性肺损伤家兔模型肺机械力学、氧代谢、血流动力学及病理学方面的影响 ,探讨最佳PEEP(BestPEEP)的确定方法。方法　采用内毒素诱导的家兔急性肺损伤 (ALI)模型 ,根据P -V曲线低位转折点 (Pinf)和PEEPtrail法确定PEEP水平 :Pinf- 2cmH2 O、Pinf、Pinf+2cmH2 O以及Ptrail,观察不同水平PEEP对ALI家兔肺机械力学、氧代谢、血流动力学及病理学的影响。结果　Ptrail和Pinf分别为 (15 8± 2 5 )cmH2 O和 (10 2± 2 1)cmH2 O差异显著 (P >0 0 5 )。虽然Ptrail组PaO2 显著高于Pinf组和Pinf+2cmH2 O组 ,但是Ptrail组心脏指数及氧输送指数均显著低于Pinf组和Pinf+2cmH2 O组 (P <0 0 5 )。Pinf组及Pinf+2cmH2 O组肺静态顺应性显著高于Ptrail组和Pinf- 2cmH2 O组 ,且Pinf组及Pinf+2cmH2 O组肺损伤指数显著低于Ptrail组和Pinf - 2cmH2 O组 (P <0 0 1)。结论　根据P -V曲线法确定PEEP是选择最佳PEEP的理想方法。Pinf或Pinf+2cmH2 O为最佳PEEP ,可获得最大肺顺应性和最大氧输送 ,而肺损伤最小。     

最佳氧合法导向的PEEP对ARDS绵羊血流动力学和气体交换的影响

目的 探讨最佳氧合法导向的呼气末正压（PEEP）对急性呼吸窘迫综合征（ARDS）绵羊血流动力学和气体交换的影响。方法 肺泡灌洗法复制绵羊ARDS模型（n=6）,在充分肺复张的基础上,利用最佳氧合法滴定最佳PEEP。并维持通气2h。观察基础状态（PEEP 5 cmH2O）、ARDS模型稳定（PEEP 5cmH2O）和最佳PEEP维持通气2h的血流动力学、气体交换和呼吸力学变化。结果 最佳氧合法滴定的最佳PEEP为（18&#177;2）cmH2O。与ARDS模型比较,最佳PEEP维持通气期间心率（HR）、平均动脉压（MAP）、心脏指数（CI）、每搏指数（SVI）、中心静脉压（CVP）、平均肺动脉压（MPAP）、肺动脉嵌顿压（PAWP）和肺循环阻力指数（PVRI）差异无统计学意义（P〉0．05）,CVP、MPAP、PAWP和PVRI较基础状态明显升高（P〈0．05）。与ARDS模型稳定时比较,最佳PEEP维持通气期间动脉血二氧化碳分压（PaCO2）明显降低（P〈0．05）,氧合指数（PaO2／FiO2）和氧输送（DO2I）显著升高（P〈0．05）,肺内分流率（Qs／Qt）明显改善（P〈0．05）,且PaCO2、PaO2／FiO2、DO2I和Qs／Qt均接近基础状态（P〉0．05）。与ARDS模型稳定时比较,最佳PEEP维持通气期间的平均气道压（Pm）明显升高（P〈0．05）、平台压力（Pplat）无明显变化（P〉0．05）、肺动态顺应性（Cdyn）明显增加（P〈0．05）。结论 最佳氧合法导向的PEEP能有效地减少ARDS绵羊的肺内分流、改善氧合和肺顺应性,对血流动力学无明显影响。     

不同密闭式吸痰方法对急性呼吸窘迫综合征小猪呼吸力学的影响

目的探讨密闭式吸痰时高氧法和(或)肺泡复张术对急性呼吸窘迫综合征(ARDS)小猪呼吸力学的影响。方法16只小猪给予清洁剂(1.37±0.64mg/kg)气管注入制作ARDS模型,模型成功后随机分为呼气末正压(PEEP)5cmH2O和10cmH2O两组,每组8只。每只小猪按随机顺序分别采用以下4种方法吸痰①单纯密闭式吸痰(简称单纯法),②高氧法密闭式吸痰(简称高氧法),即吸痰前1min给予100%氧供贯穿整个吸痰过程,共持续2min,③复张法密闭式吸痰(简称复张法),即吸痰后立即调节PEEP水平到20cmH2O,通气10s,④高氧 复张法密闭式吸痰(简称结合法),即吸痰时高氧供及肺泡复张术两种措施联合应用。观察吸痰前1min、吸痰后1min、3min、5min、10min小猪呼吸力学的变化。结果单纯法吸痰后ARDS小猪气道峰压(Ppeak),平台压(Pplat)和平均压(Pmean)升高,肺静态顺应性(Cs)下降,与吸痰前相比差异有统计学意义(P<0.05);高氧法吸痰后1minPpeak,Pplat和Pmean也随即升高,Cs明显降低(P<0.05);复张法吸痰后ARDS小猪Cs升高,Ppeak,Pplat和Pmean降低,与吸痰前基线水平比较,差异有统计学意义(P<0.05);结合法吸痰后1minPpeak,Pplat和Pmean与吸痰前相比明显下降,Cs显著升高(P<0.05)。不论在PEEP5cmH2O还是10cmH2O水平,各种吸痰方法对ARDS小猪呼吸力学的影响趋势均一致。但在PEEP5cmH2O组,吸痰所引起的缺氧及气道高压持续时间较长。结论单纯法和高氧法可使ARDS小猪肺顺应性降低,气道压力增高;有加重ARDS动物肺损伤的潜在危险;吸痰后给予肺泡复张术可改善ARDS小猪呼吸力学,且未发现明显不良反应,是一种比较安全的吸痰方式。     

小儿急性肺损伤的呼吸功能与炎症的研究

目的:探讨儿科急性肺损伤(ALI)的病理生理和发病机制。方法:比较小儿ALI与呼吸功能正常儿的呼吸功能与炎症因子的变化。结果:(1)ALI患儿血气分析显示氧合或通气功能不同程度的恶化。氧合功能(PaO2/FiO2)下降有47例;指标PaCO2上升有27例。(2)机械通气所需气道峰压(PIP)和呼气末正压(PEEP)呈不同程度的上升,PIP上升26例,ALI患儿与呼吸功能正常儿为(28.62±6.38)cmH2O比(20.90±3.60)cmH2O,P<0.05;PEEP为(5.0±1.6)cmH2O比(2.0±0.6)cmH2O,P<0.01。(3)ALI患儿血清TNF-α较正常对照组升高,分别为(32.60±8.62)pg/mL和(8.54±3.04)pg/mL,P<0.001。结论:(1)ALI的肺病理生理变化特点除氧合功能下降或肺泡有效通气减少外,还有小气道阻力升高;(2)全身炎症反应可能参与小儿ALI。     

压力调节容量控制通气对急性肺损伤血流呼吸动力学和氧代谢的影响

目的研究压力调节容量控制通气(PRVC)和间歇正压通气(IPPV)对急性肺损伤(ALI)患者血流动力学、呼吸动力学和氧代谢的影响.方法对30例ALI患者分别进行呼吸末正压(PEEP)0、5、10 cmH2O水平下的PRVC和IPPV通气,测定其血流动力学、呼吸力学和氧代谢参数.结果比较PRVC和IPPV二种通气模式,同一水平PEEP其血流动力学无明显差异(P＞0.05),但吸气峰压(PIP)、肺动态顺应性(Cst)、动脉氧分压(PaO2)和氧供(DO2)均有明显差异(P＜0.05).结论PRVC与IPPV相比能明显降低PIP,增加Cst,增加DO2.     

Current definitions of acute lung injury and the acute respiratory distress syndrome do not reflect their true severity and outcome

Background: Despite intensive research, there are no universally accepted clinical definitions for acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS). A recent joint American-European Consensus Conference on ARDS formally defined the difference between ALI and ARDS based on the degree of oxygenation impairment. However, this definition may not reflect the true prevalence, severity and prognosis of these syndromes. Methods: During a 22-month period, 56 consecutive mechanically ventilated patients who met the American-European Consensus definition for ARDS [arterial oxygen tension/fractional inspired oxygen (PaO₂/FIO₂≤ 200 mmHg regardless of the level of positive end-expiratory pressure (PEEP), bilateral pulmonary infiltrates, and no evidence of left heart failure] were admitted into the intensive care units (ICU) of the Hospital del Pino, Las Palmas, Spain, and prospectively studied. The diagnosis of ALI and ARDS was made by a PEEP-FIO₂ trial, 24 h after patients met the Consensus inclusion criteria. Patients were classified as having ALI_{–24 h} if the PaO₂/FIO₂ was > 150 mmHg with PEEP = 5 cmH₂O, and ARDS_{–24 h} if the PaO₂ /FIO₂ was ≤ 150 mmHg with PEEP ≥ 5 cmH₂O. Results: Overall mortality was 43 % (24 of 56). However, 24 h after inclusion, PaO₂ response to PEEP 5 cmH₂O allowed the separation of our patients into two different groups: 31 patients met our ALI_{–24 h} criteria (PaO₂/FIO₂ > 150 mmHg) and their mortality was 22.6 %; 25 patients met our ARDS_{–24 h} criteria (PaO₂/FIO₂≤ 150 mmHg) and their mortality was 68 % (p = 0.0016). The differences in the respiratory severity index during the first 24 h of inclusion, PaO₂/FIO₂ ratio at baseline and at 24 h, maximum plateau airway pressure, maximum level of PEEP, and number of organ system failures during the ICU stay were statistically significant. Conclusions: Since the use of PEEP in the American-European Consensus criteria for ARDS is not mandatory, that definition does not reflect the true severity of lung damage and outcome. Our data support the need for guidelines based on a specific method of evaluating oxygenation status before the American-European Consensus definition is adopted. Received: 18 April 1999 Final revision received: 30 June 1999 Accepted: 9 July 1999     

PEEP-induced tricuspid regurgitation

Objective : To determine the presence of tricuspid regurgitation (TR) in patients affected by acute lung injury (ALI) and the adult respiratory distress syndrome (ARDS) during mechanical ventilation with positive end-expiratory pressure (PEEP). Design: A prospective clinical study. Setting: 10-bed general intensive care unit in a University Hospital. Patients: 7 consecutive patients an age 44.7 ± 8.6 years with a diagnosis of ALI or ARDS were studied. All were on mechanical ventilation with PEEP. Interventions: PEEP was increased in steps of 5 cm H₂O until the appearance of TR or up to a limit of 20 cm H₂O. Measurements and results: Right atrial pressure, pulmonary artery pressure, and wedge pressure were measured and cardiac output was determined by thermodilution. TR was graded from 0 to 3. Standard 2D echocardiographic and pulsed-wave images were obtained at each level of PEEP. PEEP was increased from 4 ± 3 to 17 ± 2 cm H₂O. Mean PAP increased from 27.7 ± 2.9 to 36.7 ± 3.5 mm Hg (p < 0.02) when PEEP was increased. Five patients had competent valves and two had mild TR at baseline. In six out of the seven, TR either developed or increased when PEEP was increased. Conclusions: Our study demonstrated the development of TR after the use of PEEP in patients with ALI and ARDS as a consequence of pulmonary hypertension and right ventricular overloading. Since TR may randomly affect cardiac output values and derived parameters, the assessment of cardiac performance by some techniques such as thermodilution should be used with caution. Received: 3 December 1996 Acepted: 5 May 1997     

FiO_2×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FiO_2×PEEP水平的变化,探讨其对重症甲型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FiO_2、PEEP、PaO_2,并计算FiO_2×PEEP及氧合指数(PaO_2/FiO_2),比较FiO_2×PEEP与氧合指数之间关系,动态比较两组治疗前后FiO_2×PEEP的变化趋势及其差异.结果 ①FiO_2×PEEP与氧合指数呈负相关(r=-0.44,P<0.05);②存活组治疗前后FiO_2×PEEP均低于死亡组;③存活组在治疗干预后FiO_2×PEEP逐渐下降,而死亡组FiO_2×PEEP无下降趋势.结论 FiO_2×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.     

静脉输注高氧液对急性肺损伤的治疗作用

目的探讨静脉输注高氧液对急性肺损伤（ALI）的疗效。方法将高浓度氧气溶解在常规输液用液体内制备成高氧液，通过静脉输液的方式进行输氧。33例ALI患者入选，给予高浓度面罩吸氧2h后仍缺氧者即给予静脉输氧，于静脉输氧1、3h后进行血气分析，并与治疗前比较；对低氧血症仍未纠正并进展为急性呼吸窘迫综合征（ARDS）者，给予机械通气并继续静脉输氧治疗。结果在静脉输注高氧液1h和3h后，有25例患者动脉血氧分压（PaO2）升高明显（P〈0．01），氧合指数改善明显（P〈0．01）；对8例进展为ARDS者，及时进行机械通气并继续静脉输氧，其中5例低氧血症纠正并最终脱机。结论静脉输氧对AL1患者的低氧血症具有较好的治疗作用，并能防止AL1进展为ARDS。     

Acute respiratory distress syndrome: Underrecognition by clinicians

Background

Previous reports suggest that acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is underdiagnosed in both adult and pediatric clinical practice. Underrecognition of this condition may be a barrier to instituting a low tidal volume ventilation strategy. This study aimed to determine the accuracy of clinical diagnoses of ARDS in daily practice using the American European Consensus Conference (AECC) criteria as a criterion standard and to investigate whether clinical recognition of ARDS altered ventilator management.

Methods

This retrospective study included intensive care unit (ICU) patients who died and underwent postmortem examination. Two independent reviewers assigned each patient to those with ALI/ARDS or no ALI. For those who met AECC criteria for ARDS, all patient records were reviewed for the presence of a documented diagnosis of the condition. The accuracy of the clinicians in diagnosing ALI/ARDS was determined, and ventilator settings between the clinically “diagnosed” and “non-diagnosed” groups were compared. The diagnostic accuracy in predetermined subgroups (those with diffuse alveolar damage, with ≥ 3 affected chest x-ray quadrants, with diagnosis ≥ 3 days, with pulmonary vs extrapulmonary cause) was also examined.

Results

Of 98 consecutive ICU patients who died and underwent autopsy, 51 met the inclusion criteria. Sixteen of 51 patients (31.3%) who had ALI/ARDS according to the AECC criteria had this recorded in their clinical notes. Those with histologic evidence of ALI/ARDS (diffuse alveolar damage) and with a more severe chest x-ray pattern or who satisfied the criteria for a number of consecutive days were no more likely to have a clinical diagnosis of ALI/ARDS recorded. However, those with a pulmonary cause of ALI/ARDS were more likely to have a diagnosis recorded. Tidal volumes, positive end-expiratory pressure, and mean airway pressure were higher in those with a clinical diagnosis of ARDS.

Conclusions

Acute respiratory distress syndrome is underrecognized by clinicians in ICU, and recognition does not result in lower tidal volume ventilation. Significant barriers remain to the recognition of ALI/ARDS and application of an evidence-based ventilator strategy.     

高呼气末正压通气结合小潮气量对急性肺损伤/急性呼吸窘迫综合征患者预后影响的荟萃分析

目的 系统评价高呼气末正压(PEEP)与低PEEP机械通气对急性肺损伤/急性呼吸窘迫综合征(ALI/ARDS)患者预后的影响.方法 通过检索美国<医学索引>、荷兰<医学文摘>、Cochrane临床试验数据库、中国生物医学文献数据库(CBM)和中国期刊网全文数据库(CNKI)等文献数据库,全面收集全世界范围内高PEEP与低PEEP治疗ALI/ARDS患者的随机对照试验(RCT),提取文献中的相关资料和评估方法学质量,而后采用Cochrane协作网RevMan 5.0软件对资料进行荟萃分析(Meta分析).结果 最终纳入6个RCT共2484例ALI/ARDS患者.A亚组的3个RCT中试验组采用了高PEEP(相对于对照组),对照组采用了低PEEP(相对于试验组),两组均采用了小潮气量(6 ml/kg)通气;B亚组的3个RCT中试验组采用了高PEEP加小潮气量,对照组采用了低PEEP加传统潮气量通气.合并结果显示,B亚组中高PEEP加小潮气量通气策略可以降低患者的28 d病死率[Peto比值比(OR)=0.40,95%可信区间(95%CI)0.22～0.72,P=0.003]和气压伤发生率(OR=0.20,95%CI 0.05～0.82,P=0.02);A亚组中,两组患者的28 d病死率(OR=0.86,95%CI 0.72～1.02,P=0.08)和气压伤发生率(OR=1.19,95%CI 0.89～1.58,P=0.25)差异无统计学意义.结论 高PEEP加小潮气量通气可以改善ALI/ARDS患者的28 d病死率和气压伤发生率,单独高PEEP的作用需要进一步评价.

Abstract：

Objective To compare the effects of high and low positive end-expiratory pressure (PEEP) levels on prognosis of patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Methods The data in PubMed, EMbase, Cochrane Library, CBM and CNKI were retrieved. All randomized controlled trials (RCTs) of treatment of ALI/ARDS with PEEP with high or low level were included. Study selection and assessment, data collection and analyses were undertaken by two independent reviewers. Meta-analyses were done using Cochrane Collaboration's RevMan 5.0 software.Results Six RCTs, involving a total of 2 484 patients of ALI/ARDS were included in the review. According to ventilation strategy, all trials were divided into subgroup A (high PEEP+low tidal volume of 6 ml/kg vs.low PEEP+low tidal volume) and subgroup B (high PEEP+low tidal volume vs. low PEEP+traditional tidal volume). In subgroup B, there were three RCTs, and high PEEP was found to be associated with a lower 28-day mortality [odds ratio (OR)=0. 40, 95% confidence interval (95%CI) 0.22 -0.72, P=0.003]and a lower barotraumas (OR = 0.20,95%CI 0.05 - 0.82, P = 0.02) in patients with ALI/ARDS. In subgroup A, there were three RCTs, and it was found that the differences in 28-day mortality (OR=0.86,95%CI 0.72 - 1.02, P = 0.08) and barotraumas (OR = 1.19, 95%CI 0.89 - 1.58, P= 0.25) were not significant. Conclusion As compared with conventional ventilation, high PEEP and low tidal volume ventilation are associated with improved survival and a lower rate of barotrauma in patients with ALI/ARDS.It is necessary to further confirm the role of high PEEP only in the ventilation strategy in patients with ALI/ARDS.     

Lung computed tomography during a lung recruitment maneuver in patients with acute lung injury

OBJECTIVE: To assess the acute effect of a lung recruitment maneuver (LRM) on lung morphology in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). PATIENTS: Ten patients with ALI/ARDS on mechanical ventilation. DESIGN: Prospective clinical study. SETTING: Computed tomography (CT) scan facility in a teaching hospital. INTERVENTIONS: An LRM performed by stepwise increases in positive end-expiratory pressure (PEEP) of up to 30-40 cm H(2)O. Lung basal CT sections were taken at end-expiration (patients 1 to 5), and at end-expiration and end-inspiration (patients 6 to 10). Arterial blood gases and static compliance (C(st)) were measured before, during and after the LRM. MEASUREMENTS AND MAIN RESULTS: Poorly aerated and non-aerated tissue at PEEP 10 cm H(2)O accounted for 60.0+/-29.1% of lung parenchyma, while only 1.1+/-1.8% was hyperinflated. Increasing PEEP to 20 and 30 cm H(2)O, compared to PEEP 10 cm H(2)O, decreased poorly aerated and non-aerated tissue by 16.2+/-28.0% and 33.4+/-13.8%, respectively ( p<0.05). This was associated with an increase in PaO(2) and a decrease in total static compliance. Inspiration increased alveolar recruitment at all PEEP levels. Hyperinflated tissue increased up to 2.9+/-4.0% with PEEP 30 cm H(2)O, and to a lesser degree with inspiration. No barotrauma or severe hypotension occurred. CONCLUSIONS: Lung recruitment maneuvers improve oxygenation by expanding collapsed alveoli without inducing too much hyperinflation in ALI/ARDS patients. An LRM during the CT scan gives morphologic and functional information that could be useful in setting ventilatory parameters.     

Impact of positive end-expiratory pressure on the definition of acute respiratory distress syndrome

Objective We examined whether PEEP during the first hours of ARDS can induce such a change in oxygenation that could mask fulfillment of the AECC criteria of a PaO₂/FIO₂ 200 essential for ARDS diagnosis.Design and setting Observational, prospective cohort in two medical-surgical ICU in teaching hospitals.Patients 48 consecutive patients who met AECC criteria of ARDS on 0 PEEP (ZEEP) at the moment of diagnosis.Measurements and results PaO₂/FIO₂ and lung mechanics were recorded on admission (0 h) to the ICU on ZEEP, and after 6, 12, and 24 h on PEEP levels selected by attending physicians. Lung Injury Score (LIS) was calculated at 0 and 24 h. PaO₂/FIO₂ rose significantly from 121±45 on ZEEP at 0 h, to 234±85 on PEEP of 12.8±3.7 cmH₂O after 24 h. LIS did not change significantly (2.34±0.53 vs. 2.42±0.62). These variables behaved similarly in pulmonary and extrapulmonary ARDS, and in survivors and nonsurvivors. After 24 h only 18 patients (38%) still had a PaO₂/FIO₂ of 200 or lower. Their mortality was similar to that in the remaining patients (61% vs. 53%).Conclusions The use of PEEP improved oxygenation such that one-half of patients after 6 h, and most after 24 h did not fulfill AECC hypoxemia criteria of ARDS. However, LIS remained stable in the overall series. These results suggest that PEEP level should be taken into consideration for ARDS diagnosis.     

呼气末正压对感染性休克患者心脏前负荷的影响

目的 探讨不同水平的呼气末正压(PEEP)对接受机械通气的感染性休克患者心脏前负荷的影响.方法 采用前瞻性、干预性的研究方法对北京协和医院MICU 15例行机械通气的感染性休克患者应用跨肺热稀释法及持续脉搏轮廓的方法进行血流动力学监测(PiCCOplus).所有患者采用容量控制通气,血流动力学稳定后,每隔1 h递增PEEP水平,PEEP从0增加20 cmH_2O(如果能耐受),根据不同的PEEP水平分为5组(0,5,10,15,20 cmH_2O).应用one-way ANOVA和Pearson's行统计分析及相关分析,观察在不同水平的PEEP对心脏前负荷的影响及其相关性.结果 15例感染性休克患者,男10例(67%),女5例(33%),年龄(67.6±19.5)岁,APACHEⅡ评分(22.1±7.5)分,基础PEEP水平(8.5±3.6)cmH_2O,基础PaO_2/FiO_2(225.6±89.2)mmHg,ICU病死率67%.随着PEEP的升高,CVP明显升高,不同水平的PEEP组差异具有统计学意义(p=0.002),而GEDI无明显变化,各组间差异无统计学意义.以PEEP0为基础值,不同PEEP水平的CVP,CI,GEDI与基础值之差为增量,发现△CI和△GEDI呈明显的正相关(r=0.6),而△CI和△CVP无明显的相关性.结论 在高PEEP存在的情况下,GEDI能够有效地评价心脏的前负荷.