Both lung recruitment maneuver and PEEP are needed to increase oxygenation and lung volume after cardiac surgery

BACKGROUND: Patients ventilated after cardiac surgery commonly have impaired oxygenation, mainly due to lung collapse. We have previously found that PaO2 and end-expiratory lung volume (EELV) were increased by a lung recruitment maneuver (LRM) followed by positive end-expiratory pressure (PEEP). The aim of this study was to evaluate whether only PEEP or only a LRM could give similar effects. METHODS: Thirty circulatory stable patients (aged 55-79 years) mechanically ventilated after cardiac surgery were randomized to receive LRM (four 10-s insufflations to an airway pressure of 45 cmH2O) and zero end-expiratory pressure (LRM-group), PEEP 12 cmH2O (PEEP-group) or LRM in combination with PEEP 12 cmH2O (LRM + PEEP-group). The set end-expiratory pressure was kept for 75 min. Before, during and after the intervention, EELV (SF6 washout technique) and blood gases were measured. RESULTS: Initial EELV and PaO2 were similar in all groups. In the LRM-group, PaO2 and EELV increased transiently (P < 0.0001), but returned at 5 min to the initial values. In the PEEP-group, PaO2 did not change but EELV increased to 155 +/- 27% of the initial value (P < 0.0001). In the LRM+PEEP-group, PaO2 and EELV increased to 212 +/- 66% and 178 +/- 31% of the initial values (P < 0.0001), respectively, and were maintained during PEEP application. CONCLUSION: In patients ventilated after cardiac surgery: (1) PEEP increased lung volume but not PaO2, (2) a lung recruitment maneuver without subsequent PEEP had no sustained effect, and (3) both a lung recruitment maneuver and PEEP were needed to increase and maintain the increased lung volume and PaO2.     

An individualized recruitment maneuver for mechanically ventilated patients after cardiac surgery

Purpose  The recruitment maneuver (RM) has been shown to improve oxygenation for post-cardiopulmonary bypass (CPB) patients; however, sustained inflation of the lung gives rise to hypotension. The primary goal of our study was to evaluate the safety and efficacy of our proposed RM, defined on the basis of dynamic lung compliance (Cdyn). Methods  Twenty-eight patients undergoing elective cardiac surgery with CPB were assigned to two treatment groups: an individualized RM group, in which a pressure equal to 15 ml × real body weight/Cdyn + positive end-expiratory pressure (PEEP) cmH₂O was applied for 15 s; and a control RM group, in which a pressure of 20 cmH₂O was applied for 25 s. Arterial blood pressure, cardiac output, pulmonary artery pressure, and heart rate (HR) were monitored. Tidal volume (V_T), and airway pressure were continuously obtained from an expiratory flow meter and pressure monitor. Blood samples were obtained and analyzed with a blood gas analyzer. Results  The changes in HR, mean arterial pressure, mean pulmonary artery pressure, and cardiac index at the end of the RM were not significantly different between the two groups. The mean airway pressure of sustained inflation was 28.3 ± 1.3 cmH₂O in the individualized RM group. The individualized RM significantly improved the Cdyn and partial pressure arterial oxygen/inspiratory fraction of oxygen (P/F) ratio compared with values in the control RM group (P = 0.026 and P = 0.012, respectively). Conclusion  The present study indicates that the individualized RM resulted in minimum changes of hemodynamics and brought about improvement in oxygenation and lung compliance.     

The effects of the alveolar recruitment maneuver and positive end-expiratory pressure on arterial oxygenation during laparoscopic bariatric surgery

Abnormalities in gas exchange that occur during anesthesia are mostly caused by atelectasis, and these alterations are more pronounced in morbidly obese than in normal weight subjects. Sustained lung insufflation is capable of recruiting the collapsed areas and improving oxygenation in healthy patients of normal weight. We tested the effect of this ventilatory strategy on arterial oxygenation (Pao2) in patients undergoing laparoscopic bariatric surgery. After pneumoperitoneum was accomplished, the recruitment group received up to 4 sustained lung inflations with peak inspiratory pressures up to 50 cm H2O, which was followed by ventilation with 12 cm H2O positive end-expiratory pressure (PEEP). The patient's lungs in the control group were ventilated in a standard fashion with PEEP of 4 cm H2O. Variables related to gas exchange, respiratory mechanics, and hemodynamics were compared between recruitment and control groups. We found that alveolar recruitment effectively increased intraoperative Pao2 and temporarily increased respiratory system dynamic compliance (both P < 0.01). The effects of alveolar recruitment on oxygenation lasted as long as the trachea was intubated, and lungs were ventilated with high PEEP, but soon after tracheal extubation, all the beneficial effects on oxygenation disappeared. The mean number of vasopressor treatments given during surgery was larger in the recruitment group compared with the control group (3.0 versus 0.8; P = 0.04). In conclusion, our data suggest that the use of alveolar recruitment may be an effective mode of improving intraoperative oxygenation in morbidly obese patients. Our results showed the effect to be short lived and associated with more frequent intraoperative use of vasopressors.     

Beneficial effects of high positive end-expiratory pressure in lung respiratory mechanics during laparoscopic surgery

Background: The effect of neuromuscular blockade (NMB) and positive end‐expiratory pressure (PEEP) on the elastic properties of the respiratory system during pneumoperitoneum (PnP) remains a controversial subject. The main objective of the present study was to evaluate the effects of NMB and PEEP on respiratory mechanics. Methods: We performed a dynamic analysis of respiratory mechanics in patients subjected to PnP. Twenty‐one patients underwent cholecystectomy videolaparoscopy and total intravenous anesthesia. The respiratory system resistance (R_RS), pulmonary elastance (E_P), chest wall elastance (E_CW), and respiratory system elastance (E_RS) were computed via the least squares fit technique using an equation describing the motion of the respiratory system, which uses primary signs such as airway pressure, tidal volume, air flow, and esophageal pressures. Measurements were taken after tracheal intubation, PnP, NMB, establishment of PEEP (10 cmH₂O), and PEEP withdrawal [zero end‐expiratory pressure (ZEEP)]. Results: PnP significantly increased E_RS by 27%; both E_P and E_CW increased 21.3 and 64.1%, respectively (P<0.001). NMB did not alter the respiratory mechanic properties. Setting PEEP reduced E_RS by 8.6% (P<0.05), with a reduction of 10.9% in E_P (P<0.01) and a significant decline of 15.7% in R_RS (P<0.05). These transitory changes in elastance disappeared after ZEEP. Conclusions: We concluded that the 10 cmH₂O of PEEP attenuates the effects of PnP in respiratory mechanics, lowering R_RS, E_P, and E_RS. These effects may be useful in the ventilatory approach for patients experiencing a non‐physiological increase in IAP owing to PnP in laparoscopic procedures.     

Effects of end-inspiratory and end-expiratory pressures on alveolar recruitment and derecruitment in saline-washout-induced lung injury -- a computed tomography study

BACKGROUND: Lung protective ventilation using low end-inspiratory pressures and tidal volumes (VT) has been shown to impair alveolar recruitment and to promote derecruitment in acute lung injury. The aim of the present study was to compare the effects of two different end-inspiratory pressure levels on alveolar recruitment, alveolar derecruitment and potential overdistention at incremental levels of positive end-expiratory pressure. METHODS: Sixteen adult sheep were randomized to be ventilated with a peak inspiratory pressure of either 35 cm H2O (P35, low VT) or 45 cm H2O (P45, high VT) after saline washout-induced lung injury. Positive end-expiratory pressure (PEEP) was increased in a stepwise manner from zero (ZEEP) to 7, 14 and 21 cm of H2O in hourly intervals. Tidal volume, initially set to 12 ml kg(-1), was reduced according to the pressure limits. Computed tomographic scans during end-expiratory and end-inspiratory hold were performed along with hemodynamic and respiratory measurements at each level of PEEP. RESULTS: Tidal volumes for the two groups (P35/P45) were: 7.7 +/- 0.9/11.2 +/- 1.3 ml kg(-1) (ZEEP), 7.9 +/- 2.1/11.3 +/- 1.3 ml kg(-1) (PEEP 7 cm H2O), 8.3 +/- 2.5/11.6 +/- 1.4 ml kg(-1) (PEEP 14 cm H2O) and 6.5 +/- 1.7/11.0 +/- 1.6 ml kg(-1) (PEEP 21 cm H2O); P < 0.001 for differences between the two groups. Absolute nonaerated lung volumes during end-expiration and end-inspiration showed no difference between the two groups for given levels of PEEP, while tidal-induced changes in nonaerated lung volume (termed cyclic alveolar instability, CAI) were larger in the P45 group at low levels of PEEP. The decrease in nonaerated lung volume was significant for PEEP 14 and 21 cm H2O in both groups compared with ZEEP (P < 0.005). Over-inflated lung volumes, although small, were significantly higher in the P45 group. Significant respiratory acidosis was noted in the P35 group despite increases in the respiratory rate. CONCLUSION: Limiting peak inspiratory pressure and VT does not impair alveolar recruitment or promote derecruitment when using sufficient levels of PEEP.     

不同氧浓度肺复张联合呼气末正压对胸腔镜肺癌根治术患者术后肺部并发症的影响

目的 探究不同氧浓度肺复张联合呼气末正压（PEEP）对胸腔镜肺癌根治术患者术后肺部并发症（PPCs）的影响。
方法 选择2020年7月至2021年4月期间择期行肺癌根治术患者100例,男59例,女41例,年龄44～73岁,BMI ≤30 kg/m²,ASA Ⅰ—Ⅲ级。采用随机数字表法分为两组：FiO ₂ 80%肺复张组（H组）和FiO₂ 30%肺复张组（L组）,每组50例。两组均于单肺通气（OLV）结束时以不同氧浓度进行肺复张,复张完毕后予PEEP 6～8 mmH₂O通气持续至术毕。记录PPCs发生情况、PPCs严重程度分级以及术后住院时间,记录术后谵妄、恶心呕吐、低血压、高血压等不良反应发生情况。
结果 两组PPCs发生率［L组19例（38%） vs H组24例（48%）］差异无统计学意义。L组PPCs分级≥2级所占比例明显低于H组[5例(10%) vs 13例(26%),P＜0.05],L组术后住院时间明显短于H组[ (4.5±0.7) d vs (4.9±0.8) d,P＜0.05]。两组术后不良反应发生率差异无统计学意义。
结论 与80%氧浓度肺复张比较,30%氧浓度肺复张不能降低胸腔镜肺癌根治术患者PPCs发生率,但低氧浓度肺复张有助于减轻术后肺部并发症严重程度,缩短术后住院时间。     

Changes in respiratory mechanics and gas exchange during the acute respiratory distress syndrome

BACKGROUND: The time course of impairment of respiratory mechanics and gas exchange in the acute respiratory distress syndrome (ARDS) remains poorly defined. We assessed the changes in respiratory mechanics and gas exchange during ARDS. We hypothesized that due to the changes in respiratory mechanics over time, ventilatory strategies based on rigid volume or pressure limits might fail to prevent overdistension throughout the disease process. METHODS: Seventeen severe ARDS patients {PaO2/FiO2 10.1 (9.2-14.3) kPa; 76 (69-107) mmHg [median (25th-75th percentiles)] and bilateral infiltrates} were studied during the acute, intermediate, and late stages of ARDS (at 1-3, 4-6 and 7 days after diagnosis). Severity of lung injury, gas exchange, and hemodynamics were assessed. Pressure-volume (PV) curves of the respiratory system were obtained, and upper and lower inflection points (UIP, LIP) and recruitment were estimated. RESULTS: (1) UIP decreased from early to established (intermediate and late) ARDS [30 (28-30) cmH2O, 27 (25-30) cmH2O and 25 (23-28) cmH2O (P=0.014)]; (2) oxygenation improved in survivors and in patients with non-pulmonary etiology in late ARDS, whereas all patients developed hypercapnia from early to established ARDS; and (3) dead-space ventilation and pulmonary shunt were larger in patients with pulmonary etiology during late ARDS. CONCLUSION: We found a decrease in UIP from acute to established ARDS. If applied to our data, the inspiratory pressure limit advocated by the ARDSnet (30 cmH2O) would produce ventilation over the UIP, with a consequent increased risk of overdistension in 12%, 43% and 65% of our patients during the acute, intermediate and late phases of ARDS, respectively. Lung protective strategies based on fixed tidal volume or pressure limits may thus not fully avoid the risk of lung overdistension throughout ARDS.     

肺泡征募对单肺通气时氧合和肺内分流的影响

目的探讨肺泡征募(ARS)通气方式对单肺通气(OLV)时氧合和肺内分流的影响。方法择期行食管癌根治术患者24例随机分为观察组和对照组。全麻诱导后插入右双腔支气管导管,开胸后行OLV。观察组ARS于开胸后15min进行。记录动脉血压、HR和SpO2,并在侧卧后双肺通气(TLV)15min、OLV15min、OLV40min行动脉血气分析,以简化肺内分流公式计算肺内分流率(Qs/Qt)值。结果TLV15min和OLV15min时,观察组和对照组的SpO2、SaO2、PaO2、Qs/Qt和PaCO2差异无显著意义(P>0.05)。OLV40minARS观察组较对照组PaO2显著增加(P<0.05),Qs/Qt明显降低(P<0.05)。结论ARS通气方式在麻醉状态下OLV时可改善肺内氧合,降低肺内分流。     

Regional pulmonary pressure volume curves in mechanically ventilated patients with acute respiratory failure measured by electrical impedance tomography

BACKGROUND: We hypothesized, that in mechanically ventilated patients with acute respiratory failure, regional pressure volume curves differ markedly from conventional global pressure volume curves of the whole lung. METHODS: In nine mechanically ventilated patients with acute respiratory failure during an inspiratory low-flow manoeuvre, conventional global pressure volume curves were registered by spirometry and regional pressure volume curves in up to 912 regions were assessed simultaneously using electrical impedance tomography. We compared the lower (LIP) and upper (UIP) inflection points obtained from the conventional global pressure volume curve and regional pressure volume curves. RESULTS: We identified from the conventional global pressure volume curves LIP [3-11 (8) cmH2O] in eight patients and UIP [31-39 (33) cmH2O] in three patients. Using electrical impedance tomography (EIT), LIP [3-18 (8) cmH2O] in 54-264 (180) regions and UIP [23-42 (36) cmH2O] in 149-324 (193) regions (range and median) were identified. Lung mechanics measured by conventional global pressure volume curves are similar to the median of regional pressure volume curves obtained by EIT within the tomographic plane. However, single regional pressure volume curves differ markedly with a broad heterogeneity of lower and upper inflection points. CONCLUSION: Lower and upper inflection points obtained from conventional global pressure volume curves are not representative of all regions of the lungs.     

Extracorporeal life support during and after bilateral sequential lung transplantation in patients with pulmonary artery hypertension

The use of extracorporeal membrane oxygenator instead of standard cardiopulmonary bypass during lung transplantation is debatable. Moreover, recently, the concept of prolonged postoperative extracorporeal membrane oxygenator (ECMO) support has been introduced in many transplant centers to prevent primary graft dysfunction (PGD) and improve early and long-term results. The objective of this study was to review the results of our extracorporeal life support strategy during and after bilateral sequential lung transplantation (BSLT) for pulmonary artery hypertension. We review retrospectively our experience in BSLT for pulmonary artery hypertension between January 2010 and August 2018. A total of 38 patients were identified. Nine patients were transplanted using cardiopulmonary bypass (CPB), in eight cases CPB was followed by a prolonged ECMO (pECMO) support, 14 patients were transplanted on central ECMO support, and seven patients were transplanted with central ECMO support followed by a pECMO assistance. The effects of different support strategies were evaluated, in particular in-hospital morbidity, mortality, incidence of PGD, and long-term follow-up. The use of CPB was associated with poor postoperative results and worse long-term survival compared with ECMO-supported patients. Predictive preoperative factors for the need of intraoperative CPB instead of ECMO were identified. The pECMO strategy had a favorable effect to mitigate postoperative morbidity and mortality, not only in intraoperative ECMO-supported patients, but even in CPB-supported cases. In our experience, ECMO may be considered as the first choice circulatory support for lung transplantation. Sometimes, in very complex cases, CBP is still necessary. The pECMO strategy is very effective to reduce incidence of PGD even in CPB-supported patients.     

The effects of nebulized salbutamol, external positive end-expiratory pressure, and their combination on respiratory mechanics, hemodynamics, and gas exchange in mechanically ventilated chronic obstructive pulmonary disease patients

We hypothesized that combined salbutamol and external positive end-expiratory pressure (PEEPe) may present additive benefits in chronic obstructive pulmonary disease (COPD) exacerbation. In 10 anesthetized, mechanically ventilated, and bronchodilator-responsive COPD patients exhibiting moderate intrinsic PEEP (PEEPi), we assessed respiratory system (rs) mechanics, hemodynamics, and gas exchange at (a) baseline (zero PEEPe [ZEEPe]), (b) 30 min after 5 mg of nebulized salbutamol administration (ZEEPe-S), (c) 30 min after setting PEEPe at baseline PEEPi level (PEEPe), and (d) 30 min after 5 mg of nebulized salbutamol administration with PEEPe maintained unchanged (PEEPe-S). Return of determined variable values to baseline values was confirmed before PEEPe application. Relative to ZEEPe, (a) at ZEEP-S, PEEPi (4.8 +/- 0.7 versus 7.0 +/- 1.1 cm H(2)O), functional residual capacity change (115.6 +/- 23.1 versus 202.1 +/- 46.0 mL), minimal rs (airway) resistance (9.3 +/- 1.4 versus 11.8 +/- 2.2 cm H(2)O.L(-1).s(-1)), and additional rs resistance (5.2 +/- 1.4 versus 7.2 +/- 1.3 cm H(2)O.L(-1).s(-1)) were reduced (P < 0.01), and hemodynamics were improved; (b) at PEEPe, PEEPi (3.7 +/- 1.3 cm H(2)O) was reduced (P < 0.01), and gas exchange was improved; and (c) at PEEPe-S, PEEPi (2.0 +/- 1.2 cm H(2)O) was minimized, and rs mechanics (static rs elastance included), hemodynamics, and gas exchange were improved. Conclusively, in carefully preselected COPD patients, bronchodilation/PEEPe exhibits additive benefits.     

小潮气量结合肺复张术对食管癌开胸术后早期急性呼吸窘迫综合征患者的疗效

目的 观察小潮气量(VT)结合肺复张术对食管癌开胸术后早期急性呼吸窘迫综合征(ARDS)患者的疗效与可能出现的不良反应.方法 2007年1月1日至2009年9月30日收治食管癌开胸术后早期ARDS患者26例,男性20例,女性6例;年龄51～76岁,平均65.5岁.患者术后循环稳定,因ARDS而不能脱离机械通气.监测并持续记录无创血压、脉搏氧饱和度,实行小VT通气结合呼吸末正压(PEEP)递增法进行肺复张.记录肺复张前及两次肺复张后30 min的PEEP水平及吸入氧浓度(FiO2);监测静态肺顺应性(CLS)及动脉血气分析.结果 26例患者共实施肺复张术52次,全部患者在肺复张术后,FiO2减低,CLS增加,动脉血气分析改善.所有病例均顺利出院,未发生气压伤或其他并发症.结论 小VT结合肺复张策略可以有效改善食管癌开胸术后早期ARDS患者的低氧血症.     

Evaluation of a recruitment maneuver with positive inspiratory pressure and high PEEP in patients with severe ARDS

BACKGROUND: To evaluate the effect of a recruitment maneuver (RM) with constant positive inspiratory pressure and high positive end-expiratory pressure (PEEP) on oxygenation and static compliance (Cs) in patients with severe acute respiratory distress syndrome (ARDS). METHODS: Eight patients with ARDS ventilated with lung-protective strategy and an arterial partial pressure of oxygen to inspired oxygen fraction ratio (PaO2/FIO2) < or =100 mmHg regardless of PEEP were prospectively studied. The RM was performed in pressure-controlled ventilation at FIO2 of 1.0 until PaO2 reached 250 mmHg or a maximal plateau pressure/PEEP of 60/45 cmH2O was achieved. The RM was performed with stepwise increases of 5 cmH2O of PEEP every 2 min and thereafter with stepwise decreases of 2 cmH2O of PEEP every 2 min until a drop in PaO2 >10% below the recruitment PEEP level. Data was collected before (preRM), during and after 30 min (posRM). RESULTS: The PaO2/FIO2 increased from 83 +/- 22 mmHg preRM to 118 +/- 32 mmHg posRM (P = 0.001). The Cs increased from 28 +/- 10 ml cmH2O(-1) preRM to 35 +/- 12 ml cmH2O(-1) posRM (P = 0.025). The PEEP was 12 +/- 3 cmH2O preRM and was set at 15 +/- 4 cmH2O posRM (P = 0.025). The PEEP of recruitment was 36 +/- 9 cmH2O and the collapsing PEEP was 13 +/- 4 cmH2O. The PaO2 of recruitment was 225 +/- 105 mmHg, with five patients reaching a PaO2 > or = 250 mmHg. The FIO2 decreased from 0.76 +/- 0.16 preRM to 0.63 +/- 0.15 posRM (P = 0.001). No major complications were detected. CONCLUSION: Recruitment maneuver was safe and useful to improve oxygenation and Cs in patients with severe ARDS ventilated with lung-protective strategy.     

Continuous positive airway pressure and lung separation during cardiopulmonary bypass to facilitate congenital heart surgery via the right thorax in children

We describe a fast track anesthesia technique that facilitates congenital heart surgery via right axillary thoracotomy in children. Continuous positive airway pressure on the dependent lung, before and during cardiopulmonary bypass, approximates the heart towards the chest wall incision, and significantly improves the surgeon's access to the heart.     

肺泡复张术和呼气末正压通气对后腹腔镜术后早期呼吸功能的影响

目的探讨肺泡复张术（RM）复合呼气末正压通气（PEEP）是否能有效改善后腹腔镜手术后早期呼吸功能。方法 30例择期后腹腔镜手术患者,随机分为3组行不同的术中通气方式：对照组（n=10）行常规正压通气;PEEP组（n=10）正压通气加呼气末正压（PEEP）4 cmH2O;PEEP＋RM组（n=10）通气方式与PEEP组相同,在气腹结束后立即以30 cmH2O压力维持30s气道正压行肺泡复张术。在气腹前（Baseline）、气腹后10 min（PI 10 min）、气腹后30 min（PI 30 min）、气腹后60 min（PI 60 min）、放气腹后1 min（PD1 min）、拔管后5 min（EX 5 min）、拔管后0.5h（EX 30 min）等7个时点检测记录呼气末CO （2ETCO2）、动脉血气分析并计算动脉与呼气末CO2差值[D（a-e）CO2]、氧合指数（OI）等。结果与对照组相比,PEEP、PEEP＋RM两组在PI 60 min和PD1 min两个时点的Pa CO2显著降低（P〈0.005）。PEEP组与PEEP＋RM组在PI 30 min、PI 60 min和EX 30 min等时点,其D（a-e）CO2均显著低于对照组（P〈0.05）。在EX 5 min和EX 30 min两时点,PEEP＋RM组的OI则显著高于对照组（P〈0.05）;而两时点间Pa-CO2的差值ΔPaCO2在PEEP＋RM组显著高于对照组（P〈0.05）。结论术中使用PEEP可有效减少动脉血和肺泡的CO2分压差,减少肺泡塌陷;肺泡复张术可在拔管后有效加快动脉血CO2分压的下降并改善氧合指数。复合以上两种处理,可有效减轻后腹腔镜术后早期CO2蓄积,促进呼吸功能恢复。     

Effect of fluid loading with saline or colloids on pulmonary permeability, oedema and lung injury score after cardiac and major vascular surgery

Background. The optimal type of fluid for treating hypovolaemiawithout evoking pulmonary oedema is still unclear, particularlyin the presence of pulmonary vascular injury, as may occur aftercardiac and major vascular surgery. Methods. In a single-centre, prospective, single-blinded clinicaltrial 67 mechanically ventilated patients were randomly assignedto receive saline, gelatin 4%, HES 6% or albumin 5%, accordingto a 90 min fluid loading protocol with target central venouspressure of 13 and pulmonary capillary wedge pressure of 15mm Hg, within 3 h after cardiac or major vascular surgery. Beforeand after the protocol, we recorded haemodynamics and ventilatoryvariables and took chest radiographs. The pulmonary vascularinjury was evaluated using the ⁶⁷Ga-transferrin pulmonary leakindex (PLI) and extravascular lung water (EVLW). Plasma colloidosmotic pressure (COP) was determined and the lung injury score(LIS) was calculated. Results. More saline was infused than colloid solutions (P<0.005).The COP increased in the colloid groups and decreased in patientsreceiving saline. Cardiac output increased more in the colloidgroups. At baseline, PLI and EVLW were above normal in 60 and30% of the patients, with no changes after fluid loading, exceptfor a greater PLI decrease in HES than in gelatin-loaded patients.The oxygenation ratio improved in all groups. In the colloidgroups, the LIS increased, because of a decrease in total respiratorycompliance, probably associated with an increase in intrathoracicplasma volume. Conclusions. Provided that fluid overloading is prevented, thetype of fluid used for volume loading does not affect pulmonarypermeability and oedema, in patients with acute lung injuryafter cardiac or major vascular surgery, except for HES thatmay ameliorate increased permeability. During fluid loading,changes in LIS (and respiratory compliance) do not representchanges in pulmonary permeability or oedema.      

肺复张结合肺保护通气对肝移植术后肺损伤换气功能的影响

目的探讨肺复张结合肺保护通气策略对肝移植术后ALI或ARDS早期换气功能、血流动力学的影响。方法肝移植术后合并ALI者18例，其中6例发展为ARDS，给予25cm H2O气道压力及PEEP 17 cm H2O通气2min，扩张已萎陷实变的肺泡，并用适当的PEEP预防肺泡闭塞，保持肺泡复张。结果18例病人肺复张后氧分压、氧饱和度及吸氧分数均有明显改善，除1例肺部严重感染病人肺复张后吸氧分数仅上升40％，余17例均对肺复张反应良好。复张后平均氧分压上升68mmHg，平均氧饱和度上升9．5％，平均吸氧分数上升104．66％，改善的氧合可维持2～24h。肺复张结合肺保护通气策略纠正低氧血症的有效率为94．4％。病人对肺复张的耐受性佳，无明显并发症。结论肺复张结合肺保护通气策略是治疗肝移植术后ALI或ARDS的安全有效措施。     

Alveolar recruitment strategy and PEEP improve oxygenation,dynamic compliance of respiratory system and end‐expiratory lung volume in pediatric patients undergoing cardiac surgery for congenital heart disease

Objective: Optimizing alveolar recruitment by alveolar recruitment strategy (ARS) and maintaining lung volume with adequate positive end‐expiratory pressure (PEEP) allow preventing ventilator‐induced lung injury (VILI). Knowing that PEEP has its most beneficial effects when dynamic compliance of respiratory system (Crs) is maximized, we hypothesize that the use of 8 cm H₂O PEEP with ARS results in an increase in Crs and end‐expiratory lung volume (EELV) compared to 8 cm H₂O PEEP without ARS and to zero PEEP in pediatric patients undergoing cardiac surgery for congenital heart disease. Methods: Twenty consecutive children were studied. Three different ventilation strategies were applied to each patient in the following order: 0 cm H₂O PEEP, 8 cm H₂O PEEP without an ARS, and 8 cm H₂O PEEP with a standardized ARS. At the end of each ventilation strategy, Crs, EELV, and arterial blood gases were measured. Results: EELV, Crs, and P_aO₂/FiO₂ ratio changed significantly (P < 0.001) with the application of 8 cm H2O + ARS. Mean P_aCO₂– PETCO₂ difference between 0 PEEP and 8 cm H2O PEEP + ARS was also significant (P < 0.05). Conclusion: An alveolar recruitment strategy with relative high PEEP significantly improves Crs, oxygenation, P_aCO₂– PETCO₂ difference, and EELV in pediatric patients undergoing cardiac surgery for congenital heart disease.