肺保护性机械通气对脑损伤患者脑灌注压和脑氧代谢的影响

目的 观察肺保护性机械通气对颅脑损伤患者脑灌注压(CPP)及脑氧代谢的影响.方法 选择ICU需要机械通气的严重颅脑损伤伴呼吸衰竭患者40例,所有患者均行颅内压(ICP)监测、右侧颈内静脉逆行穿刺置管.将患者随机(随机数字法)分为①肺保护性通气组:潮气量为6～8mL/kg,初始吸氧体积分数40％,逐步提升呼气末正压(PEEP),PEEP与吸氧(FiO2)匹配同步升高,保持FiO2允许性低值;②常规通气组(对照组):潮气量为8～ 12 mL/kg,FiO2与PEEP匹配同步升高,保持PEEP允许性低值.监测桡动脉血气、平均动脉压(MAP)、颈静脉血氧饱和度(SjVO2),颈静脉血二氧化碳分压(PjVCO2),计算CPP=MAP-ICP;氧合指数PaO2/FiO2.结果 肺保护性通气组PEEP(8.2 ±3.3) cmH2O(1 cmH2O=0.098 kPa)、ICP (19.7±3.6) mmHg(1 mmHg=0.133 kPa)、PaCO2 (54±7.3 mmHg)高于对照组,VT、FiO2低于对照组,差异具有统计学意义;两组PaO2/FiO2、SjVO2、MAP、CPP差异无统计学意义.相关分析提示PaCO2与CPP呈正相关(r=0.368,P=0.019),与ICP、PaO2、SjVO2、Pjv CO2等并无相关性(P＞0.05);PEEP与ICP呈正相关;PEEP分为≤5 cmH2O、6～ 10 cmH2O及＞10 cmH2O三组,各组间ICP两两比较差异有统计学意义;PEEP在0～ 10 cmH2O上升,CPP变化不明显;PEEP＞ 10cmH2O时与CPP呈明显负相关(r=-0.395,P=0.017),CPP(58.5±7.2) mmHg,低于PEEP 0 ～ 5cmH2O时的(69.1±9.7) mmHg,差异具有统计学意义;PEEP越高,氧合指数越低;不同的PEEP水平下MAP、SjVO2、PjVCO2无明显变化.将PaCO2分为35～45 mmHg和46～60mmHg组,后者的CPP高于前组者,差异具有统计学意义(P＜ 0.05).SjVO2与PaO2及PjvCO2相关,与PaCO2、CPP、ICP、MAP及PEEP等均无相关性.结论 肺保护性通气策略对颅脑损伤患者来说是相对安全的.适当的CO2潴留联合较高的PEEP不影响脑灌注.肺保护性通气与常规通气相比SjVO2差异无统计学意义.提示两种通气方式下脑氧代谢无变化.     

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。     

保护性肺通气在俯卧位手术中的应用

目的观察小潮气量联合低水平呼气末正压（PEEP）对俯卧位手术患者氧合的影响。方法对50例ASAⅠ或Ⅱ级,择期在全麻下行胸腰椎手术患者,随机均分为两组,研究组A组使用保护性肺通气模式,VT=6ml／kg,PEEP=5cmH2O。对照组B组使用常规机械通气模式,VT=10ml／kg,分别监测麻醉前（T1）、俯卧位0．5h后（T2）、拔管后0．5h（T3）时的动脉血氧分压（PaO2）和术中的气道峰压（Ppeak）的变化,并计算氧合指数[PaO2／吸入氧浓度（FiO2）]的值。结果与B组比较,A组在T3时的PaO2、PaO2／FiO2显著提高（P〈0．05）。结论保护性肺通气模式有助于改善俯卧位手术患者术后氧合。     

痰热清联合黄芪注射液对急性呼吸窘迫综合征患者肺功能的影响

目的 观察痰热清注射液联合黄芪注射液对急性呼吸窘迫综合征(ARDS)患者肺功能的影响,并分析它们的作用机制.方法 选择ARDS患者62例,按随机原则分为常规机械通气对照组31例,机械通气+痰热清联合黄芪注射液治疗组31例,分别测定两组患者机械通气0、24、48、72 h血浆细胞间黏附分子-1(ICAM-1)水平、血气分析;监测相应时间的潮气量(Vt)、氧浓度(FiO2)、呼气末正压(PEEP)、吸气末压力(EIP)等呼吸参数,并计算氧合指数(PaO2/FiO2)、呼吸指数(RI)、肺动态顺应性(Cdyn).结果两组机械通气0 h血浆ICAM-1水平、PaO2/FiO2、RI、Cdyn比较差异均无统计学意义(P＞0.05);与对照组比较,治疗组机械通气48、72 h血浆ICAM-1水平明显下降(P＜0.05),PaO2/FiO2、RI、Cdyn均有明显改善(P＜0.05);与机械通气0、24、48 h 比较,对照组72 h PaO2/FiO2开始上升(P＜0.05),但RI、Cdyn无明显变化(P＞0.05).结论 痰热清注射液联合黄芪注射液可抑制ARDS患者血浆ICAM-1水平,同时对肺功能有很好的改善作用,有助于提高保护性通气策略的有效性.     

肺开放通气治疗急性呼吸窘迫综合征临床疗效分析

目的:通过大潮气量、高呼吸末正压(PEEP)肺开放策略,探索容量辅助控制通气、小潮气量、呼吸末正压治疗下,难以纠正的急性呼吸窘迫综合征(ARDS)低氧血症的策略。方法:容量辅助控制通气,潮气量为6mL/kg～8mL/kg,PEEP为10cmH2O～15cmH2O,FO2<60%机械通气过程中,提高PEEP20cmH2O～30cmH2O,潮气量(VT)15mL/kg,氧浓度为100%,开放通气2min～3min。低氧血症纠正,恢复基础通气模式和参数。结果:PEEP20cmH2O～30cmH2O,潮气量(VT)15mL/kg肺开放治疗ARDS有效率达96.87%(31/32)。结论:肺开放通气,促使萎陷肺泡开放,改善通气血流比例,提高PaO2,有效纠正低氧血症,为治疗ARDS的有效策略。     

反比通气对单肺通气时肺内分流和肺顺应性的影响

目的研究反比通气对择期行食管癌根治术患者单肺通气时肺内分流及肺顺应性的影响。方法 40例择期行食管癌根治术的患者随机分为两组:A组20例(吸呼比I∶E=1∶2)、B组19例(I∶E=1.5∶1)。分别于麻醉诱导后10min(T0),单肺通气后30min(T1)、60min(T2),恢复双肺通气后15min(T3)采取桡动脉血和混合静脉血做血气分析,记录呼吸力学指标(气道平台压、气道峰压、平均气道压)。结果单肺通气后T1、T2时,A组患者Qs/Qt、P plateau、Ppeak均高于B组,差异有统计学意义(P 0.01),PaO2/FiO2、Pmean、Cdyn、Cstat均低于B组,差异有统计学意义(P 0.01)。结论结果证明单肺通气时吸呼比为1.5∶1能有效的改善氧合,与传统机械通气模式相比,单肺通气时反比通气更有利于减少肺内分流并改善肺顺应性。     

较高水平呼气末正压对俯卧位通气重度ARDS病人氧合状况、肺复张指标及血清炎性因子水平的影响

目的:探讨较高水平呼气末正压(PEEP)对俯卧位通气重度急性呼吸窘迫综合征(ARDS)病人氧合状况、肺复张指标及血清炎性因子水平的影响.方法:选取医院2018年7月—2020年7月103例重度ARDS病人为研究对象,依据干预方式不同分为低PEEP组和高PEEP组.两组病人在治疗原发病基础上均给予肺保护性通气策略及俯卧位通气,低PEEP组51例给予较低水平PEEP(8～12 cmH2 O,1 cmH2 O=0.098 kPa),高PEEP组52例给予较高水平PEEP(13～17 cmH2 O),比较两组病人氧合指标、肺复张指标、血清炎性因子水平.结果:两组病人通气24 h、48 h末动脉血氧分压(PaO2)、血氧饱和度(SpO2)、氧合指数(OI)水平较干预前均升高,且高PEEP组明显高于低PEEP组(P<0.05).两组病人通气48 h末肺动态顺应性(Cdyn)水平较干预前均升高,且高PEEP组明显高于低PEEP组;肺驱动压(DP)、心率(HR)、血乳酸(Lac)水平较干预前均降低,且高PEEP组明显低于低PEEP组(P<0.05).两组病人通气48 h末血清白介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)及超敏C-反应蛋白(hs-CRP)水平较干预前均升高,且高PEEP组明显高于低PEEP组(P<0.05).结论:采用较高水平PEEP对俯卧位通气重度ARDS病人进行干预,通过扩张萎缩肺泡以改善氧合状态,调控肺复张指标,调节炎症因子水平,提高临床疗效.     

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-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PaO2/FiO2和Cdyn均明显增加,PPMC组PaO2/FiO2在RM后1、2、4 h较PLIP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、2 h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2 h(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.     

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。     

不同肺保护性通气策略对肺切除术术中通气和术后肺部并发症的影响

目的:评估小潮气量联合不同水平呼气末正压(positive end-expiratory pressure,PEEP)对胸腔镜下肺切除术患者通气氧合和术后肺部并发症(postoperative pulmonary complications,PPCs)的影响。方法:选取空军军医大学唐都医院2019年12月至2020年12月择期行胸腔镜下肺切除患者100例,采用随机数字表法分为两组:低水平PEEP组(LP组)和高水平PEEP组(HP组);LP组于单肺通气(one lung ventilation,OLV)时设置潮气量(tidal volume,V_T)6 mL/kg,PEEP≤5 cmH₂O,HP组于相同时间点设置V_T 6 mL/kg,PEEP 6~10 cmH₂O。分别于OLV前(T1)、OLV 60 min(T2)、手术结束(T3)采取桡动脉血液行血气分析;记录T1、T2、T3的心率(heart rate,HR)、脉搏血氧饱和度(pulse oxygen saturation,SpO₂)、收缩压/舒张压(systolic blood pressure/diastolic blood pressure,SBP/DBP)、呼气末二氧化碳分压(partial pressure of end-expiratory carbon dioxide,P_ETCO₂)、V_T、吸气峰压(peak pressure,Ppeak)、平台压(plateau pressure,Pplat);记录术后7 d内PPCs、胸腔引流管拔除时间、术后3 d内胸腔引流管引流量及术后住院时间。结果:与T1时比较,T2、T3时两组患者HR无明显变化;T2时平均动脉压(mean arterial pressure,MAP)明显降低(P<0.05);两组Ppeak、Pplat明显升高,动态肺顺应性(dynamic compliance,Cdyn)明显降低(P<0.05);两组患者氧合指数(oxygenation index,OI)明显降低,肺泡气-动脉血氧分压差(alveolar gas-arterial oxygen partial pressure difference,A-aDO₂)明显升高;T2时两组呼吸指数(respiratory index,RI)明显升高,T3时LP组RI明显升高(P<0.05)。与LP组比较,T2时HP组Ppeak明显升高;T2、T3时,HP组Pplat明显升高,驱动压(driving pressure,DP)明显降低,Cdyn明显增高(P<0.05);T2、T3时HP组OI明显升高,A-aDO₂、RI明显降低(P<0.05)。两组术后7 d PPCs及住院时间差异无统计学意义。结论:小潮气量6 mL/kg联合较高水平PEEP 6~10cmH₂O可改善胸腔镜下肺切除术患者OLV时通气氧合情况,利于术中麻醉管理。     

Spontaneous variability of arterial oxygenation in critically ill mechanically ventilated patients

Objective: To assess the magnitude of spontaneous variability of arterial oxygenation and oxygen tension-based indices over time in medical intensive care unit (ICU) patients and to study whether high positive end-expiratory pressure (PEEP) or inverse inspiratory-to-expiratory (I:E) ratio ventilation (IRV) results in a greater variability than low PEEP with conventiona l I:E ratio ventilation. Design: Prospective study. Setting: Medical ICU in a tertiary medical center. Participants: 23 patients requiring a pulmonary artery floating catheter for hemodynamic monitoring. Intervention: After being completely sedated, patients were randomized to receive pressure-control ventilation at setting A: high PEEP (15 cmH₂O) with conventional I:E ratio (1:2) and setting B: inverse I:E ratio (2:1) with low PEEP (5 cmH₂O) alternately, and then at setting C: low PEEP (5 cmH₂O) with conventional I:E ratio (1:2). Each ventilation setting lasted 1 h. Measurements and results: The arterial and mixed venous blood samples were measured simultaneously at baseline (time 0), and at 15, 30, 45, and 60 min thereafter. The coefficient of variation (CV) of arterial oxygen tension (PaO₂) over time was 5.9 % for setting A, 7.2 % for setting B, and 6.9 % for setting C. ANOVA showed no significant differences in CVs of PaO₂ between the three settings. Oxygen tension-based indices, alveolar-arterial oxygen difference (A-aDO₂) and PaO₂/PAO₂ (alveolar oxygen tension), displayed CV s equal to that of PaO₂; the CV of A-aDO₂/PaO₂ was significantly greater than that of PaO₂. Conclusions: In critically ill medical ICU patients, despite sedation, the spontaneous variability in PaO₂ over time is substantial. A high PEEP or IRV does not contribute to the increased variation in PaO₂. Received: 8 June 1998 Final revision received: 31 August 1998 Accepted: 5 October 1998     

支气管封堵器与双腔支气管导管对开胸前肺萎陷影响的比较

目的 比较支气管封堵器（BB）与双腔支气管导管（DLT）对开胸前肺萎陷效果的影响。方法 选取择期行电视胸腔镜下左肺叶切除术的患者72例,采用随机数表法分为3组（n = 24）：DLT常规萎陷组（DLT组）、DLT开胸前肺萎陷技术组（PTLCT-DLT组）和BB开胸前肺萎陷技术组（PTLCT-BB组）。其中,PTLCT-DLT组和PTLCT-BB组中分别有2例和1例发生低氧血症［经皮动脉血氧饱和度（SpO₂） < 90%］,被剔除,最终DLT组24例、PTLCT-DLT组22例、PTLCT-BB组23例完成该项研究。DLT组右侧卧位前左通道被夹闭并向空气开放,PTLCT-DLT组双肺纯氧通气并在侧卧位前夹闭左通道,PTLCT-BB组在侧卧位前封堵左支气管,排气管被故意堵塞。比较3组患者侧卧位即时（T₁）、单肺通气8 min（T₂）、单肺通气10 min（T₃）和开胸后2 min（T₄）的心率（HR）、收缩压（SBP）、舒张压（DBP）、SpO₂和动脉血氧分压（PaO₂）,记录3组患者在胸腔镜置入即刻的肺萎陷评分（LCS）。结果 与DLT组比较,PTLCT-DLT组和PTLCT-BB组的LCS明显升高（P < 0.05）,PTLCT-DLT组与PTLCT-BB组比较,差异无统计学意义（P > 0.05）。在T₃时点,PTLCT-DLT组和PTLCT-BB组SpO₂较DLT组明显降低（P < 0.05）,PTLCT-DLT组和PTLCT-BB组在T₂和T₃时点PaO₂较DLT组明显降低（P < 0.05）,在T₄时点较DLT组明显升高（P < 0.05）。结论 开胸前肺萎陷技术有助于BB和DLT完成开胸前肺萎陷,两者对开胸前肺萎陷的影响无差异。     

Prognostic value of extravascular lung water index in critically ill children with acute respiratory failure

Purpose

In critically ill adults, a reduction in the extravascular lung water index (EVLWi) decreases time on mechanical ventilation and improves survival. The purpose of this study is to assess the prognostic value of EVLWi in critically ill children with acute respiratory failure and investigate its relationships with PaO₂, PaO₂/FiO₂ ratio, A-aDO₂, oxygenation index (OI), mean airway pressure, cardiac index, pulmonary permeability, and percent fluid overload.

Methods

Twenty-seven children admitted to PICU with acute respiratory failure received volumetric hemodynamic and blood gas monitoring following initial stabilization and every 4?h thereafter, until discharge from PICU or death. All patients are grouped in two categories: nonsurvivors and survivors.

Results

Children with a fatal outcome had higher values of EVLWi on admission to PICU, as well as higher A-aDO₂ and OI, and lower PaO₂ and PaO₂/FIO₂ ratio. After 24?h EVLWi decreased significantly only in survivors. As a survival indicator, EVLWi has good sensitivity and good specificity. Changes in EVLWi, OI, and mean airway pressure had a time-dependent influence on survival that proved significant according to the Cox test. Survivors spent fewer hours on mechanical ventilation. We detected a correlation of EVLWi with percent fluid overload and pulmonary permeability.

Conclusions

Like OI and mean airway pressure, EVLWi on admission to PICU is predictive of survival and of time needed on mechanical ventilation.     

Assessment of regional lung recruitment and derecruitment during a PEEP trial based on electrical impedance tomography

Objective To investigate whether electrical impedance tomography (EIT) is capable of monitoring regional lung recruitment and lung collapse during a positive end-expiratory pressure (PEEP) trial. Design Experimental animal study of acute lung injury. Subject Six pigs with saline-lavage-induced acute lung injury. Interventions An incremental and decremental PEEP trial at ten pressure levels was performed. Ventilatory, gas exchange, and hemodynamic parameters were automatically recorded. EIT and computed tomography (CT) scans of the same slice were simultaneously taken at each PEEP level. Measurements and results A significant correlation between EIT and CT analyses of end-expiratory gas volumes (r = 0.98 up to 0.99) and tidal volumes (r = 0.55 up to r = 0.88) could be demonstrated. Changes in global and regional tidal volumes and arterial oxygenation (PaO₂/FiO₂) demonstrated recruitment/derecruitment during the trial, but at different onsets. During the decremental trial, derecruitment first occurred in dependent lung areas. This was indicated by lowered regional tidal volumes measured in this area and by a decrease of PaO₂/FiO₂. At the same time, the global tidal volume still continued to increase, because the increase of ventilation of the non-dependent areas was higher than the loss in the dependent areas. This indicates that opposing regional changes might cancel each other out when combined in a global parameter. Conclusions EIT is suitable for monitoring the dynamic effects of PEEP variations on the regional change of tidal volume. It is superior to global ventilation parameters in assessing the beginning of alveolar recruitment and lung collapse.     

Assessment of the SpO2/FiO2 ratio as a tool for hypoxemia screening in the emergency department

ObjectiveWe assessed the performance of the ratio of peripheral arterial oxygen saturation to the inspired fraction of oxygen (SpO₂/FiO₂) to predict the ratio of partial pressure arterial oxygen to the fraction of inspired oxygen (PaO₂/FiO₂) among patients admitted to our emergency department (ED) during the SARS-CoV-2 outbreak.MethodsWe retrospectively studied patients admitted to an academic-level ED in France who were undergoing a joint measurement of SpO₂ and arterial blood gas. We compared SpO₂ with SaO₂ and evaluated performance of the SpO₂/FiO₂ ratio for the prediction of 300 and 400 mmHg PaO₂/FiO₂ cut-off values in COVID-19 positive and negative subgroups using receiver-operating characteristic (ROC) curves.ResultsDuring the study period from February to April 2020, a total of 430 arterial samples were analyzed and collected from 395 patients. The area under the ROC curves of the SpO₂/FiO₂ ratio was 0.918 (CI 95% 0.885–0.950) and 0.901 (CI 95% 0.872–0.930) for PaO₂/FiO₂ thresholds of 300 and 400 mmHg, respectively. The positive predictive value (PPV) of an SpO₂/FiO₂ threshold of 350 for PaO₂/FiO₂ inferior to 300 mmHg was 0.88 (CI95% 0.84–0.91), whereas the negative predictive value (NPV) of the SpO₂/FiO₂ threshold of 470 for PaO₂/FiO₂ inferior to 400 mmHg was 0.89 (CI95% 0.75–0.96). No significant differences were found between the subgroups.ConclusionsThe SpO₂/FiO₂ ratio may be a reliable tool for hypoxemia screening among patients admitted to the ED, particularly during the SARS-CoV-2 outbreak.     

Differential ventilation with low-flow CPAP and CPPV in the treatment of unilateral chest trauma

A case of severe unilateral chest trauma with bronchopleural fistula is presented. Ventilatory therapy consisted of asynchronous independent lung ventilation (AILV). The injured lung was ventilated with intermittent positive pressure ventilation (IPPV) [tidal volume (TV)=200 ml, f=25/min, I:E=0.5, minute volume (MV)=5.0l/min, FiO₂=0.4], and the unaffected lung was ventilated with continuous positive pressure ventilation (CPPV) (TV=600 ml, f=12/min, I:E=0.5, MV=7.2l/min, PEEP=0.5 kPa, FiO₂=0.4). Adequate gas exchange was obtained (PaO₂=14.5±2.3 kPa, PaCO₂=5.5±0.7 kPa), but high air leakage volumes persisted. Thus, differential low-flow CPAP (V=5.0–7.5l/min, PEEP=0.5 kPa, FiO₂=0.4) of the injured lung and CPPV (TV=600 ml, f=12/min, MV-7.2l/min, I:E=0.5, PEEP=0.5 kPa, FiO₂=0.4) of the unaffected lung was applied for 36 hours. Further deterioration of pulmonary function was prevented, and the bronchopleural fistula closed after several hours. After another period of AILV the patient was treated with conventional mechanical ventilation, and finally weaned with high-flow CPAP.     

Effects of protective and conventional mechanical ventilation on pulmonary function and systemic cytokine release after cardiopulmonary bypass

Objective To evaluate the effects of protective and conventional ventilation with or without positive end-expiratory pressure (PEEP), on systemic tumor necrosis factor-, interleukin-6 levels and pulmonary function during open heart surgery.Design Prospective, randomized clinical study.Setting Single university hospital.Patients and participants Forty-four patients undergoing elective coronary artery bypass grafting surgery with cardiopulmonary bypass.Interventions Patients ventilated with (1) protective tidal volumes (6 ml/kg, respiratory rate: 15 breaths/min, PEEP 5 cmH₂O, n=15) group PV; (2) conventional tidal volumes (10 ml/kg, respiratory rate: 9 breaths/min, PEEP 5 cmH₂O, n=14) group CV+PEEP and (3) conventional tidal volumes (10 ml/kg, respiratory rate: 9 breaths/min, n=15) without PEEP, group CV+ZEEP. Various pulmonary parameters, systemic TNF- and IL-6 levels were determined throughout the study.Measurements and results There were no differences among the groups regarding the systemic TNF- and IL-6 levels. The plateau airway pressures of group PV were lower than those of groups CV+PEEP (p=0.02) and CV+ZEEP (p=0.001) after cardiopulmonary bypass. The shunt fraction of group PV was significantly lower than that of group CV+ZEEP 24 h after surgery (p<0.05). Oxygenation and the alveolar-arterial oxygen difference were better in both PEEP groups than in group CV+ZEEP 24 h after the operation.Conclusions We could not find any evidence that protective mechanical ventilation prevents some of the adverse effects of cardiopulmonary bypass on the lung, nor systemic cytokine levels, postoperative pulmonary function or length of hospitalization.This research is partially supported by Fresenius—Kabi and Aventis Pharma.     

Pressure-limited ventilation with permissive hypercapnia and minimum PEEP in salinelavaged rabbits allows progressive improvement in oxygenation,but does not avoid ventilator-induced lung injury

Objective To determine whether pressure-limited intermittent mandatory ventilation with permissive hypercapnia and positive end-expiratory pressure (PEEP) titrated to arterial oxygen tension (PaO₂) prevents or reduces acute lung injury, compared to conventional ventilation, in salinelavaged rabbits.Design Prospective randomised trial.Setting University animal laboratory.Subjects 18 New Zealand White rabbits.Interventions Following five sequential saline lung lavages, anaesthetised rabbits were randomly allocated in pairs to receive either of two ventilation protocols using intermittent mandatory ventilation. The study group had peak inspiratory pressure limited to 15 cm H₂O and arterial partial pressure of carbon dioxide (PaCO₂) was allowed to rise. The control group received 12 ml/kg tidal volume with rate adjusted for normocarbia. PEEP and fractional inspired oxygen (FIO₂) were adjusted to maintain PaO₂ between 8 and 13.3 kPa (60 and 100 mm Hg) using a predetermined protocol. At 10 h or following death, lung lavage was repeated and lung histology evaluated.Measurements and main results The mean increase in lavage cell counts and protein concentration and hyaline membrane scores were not significantly different between the groups. Oxygenation progressively improved more in the study group (p=0.01 vs control for PaO₂/FIO₂ ratio and alveolar-arterial oxygen tension gradient (AaDO₂)). PEEP was similar and the mean airway pressure higher in the control group, suggesting that this probably resulted from less ventilatorinduced injury in the study group. Four deaths occurred in the control group (three due to pneumothorax and one to hypoxaemia) and none in the study group (p=0.08).Conclusions This ventilatory protocol may have failed to prevent lung overdistension or it may have provided insufficient PEEP to prevent injury in this model; PEEP greater than the lower inflection point of the pressure-volume curve has been shown to prevent injury almost entirely.Funded by New Zealand Lottery Grants Board and Allen and Hanburys (NZ) Ltd.     

Effectiveness of prone position in acute respiratory distress syndrome and moderating factors of obesity class and treatment durations for COVID-19 patients: A meta-analysis

ObjectivesTo examine the effectiveness of prone positioning on COVID-19 patients with acute respiratory distress syndrome with moderating factors in both traditional prone positioning (invasive mechanical ventilation) and awake self-prone positioning patients (non-invasive ventilation).Research methodologyA comprehensive search was conducted in CINAHL, Cochrane library, Embase, Medline-OVID, NCBI SARS-CoV-2 Resources, ProQuest, Scopus, and Web of Science without language restrictions. All studies with prospective and experimental designs evaluating the effect of prone position patients with COVID-19 related to acute respiratory distress syndrome were included. Pooled standardised mean differences were calculated after prone position for primary (PaO₂/FiO₂) and secondary outcomes (SpO₂ and PaO₂)ResultsA total of 15 articles were eligible and included in the final analysis. Prone position had a statistically significant effect in improving PaO₂/FiO₂ with standardised mean difference of 1.10 (95%CI 0.60–1.59), SpO₂ with standardised mean difference of 3.39 (95% CI 1.30–5.48), and PaO₂ with standardised mean difference of 0.77 (95% CI 0.19–1.35). Patients with higher body mass index and longer duration/day are associated with larger standardised mean difference effect sizes for prone positioning.ConclusionsOur findings demonstrate that prone position significantly improved oxygen saturation in COVID-19 patients with acute respiratory distress syndrome in both traditional prone positioning and awake self-prone positioning patients. Prone position should be recommended for patients with higher body mass index and longer durations to obtain the maximum effect.     

Pulmonary ultrasound and pulse oximetry versus chest radiography and arterial blood gas analysis for the diagnosis of acute respiratory distress syndrome: a pilot study

IntroductionIn low-resource settings it is not always possible to acquire the information required to diagnose acute respiratory distress syndrome (ARDS). Ultrasound and pulse oximetry, however, may be available in these settings. This study was designed to test whether pulmonary ultrasound and pulse oximetry could be used in place of traditional radiographic and oxygenation evaluation for ARDS.MethodsThis study was a prospective, single-center study in the ICU of Harborview Medical Center, a referral hospital in Seattle, Washington, USA. Bedside pulmonary ultrasound was performed on ICU patients receiving invasive mechanical ventilation. Pulse oximetric oxygen saturation (SpO₂), partial pressure of oxygen (PaO₂), fraction of inspired oxygen (FiO₂), provider diagnoses, and chest radiograph closest to time of ultrasound were recorded or interpreted.ResultsOne hundred and twenty three ultrasound assessments were performed on 77 consecutively enrolled patients with respiratory failure. Oxygenation and radiographic criteria for ARDS were met in 35 assessments. Where SpO₂ ≤ 97 %, the Spearman rank correlation coefficient between SpO₂/FiO₂ and PaO₂/FiO₂ was 0.83, p < 0.0001. The sensitivity and specificity of the previously reported threshold of SpO₂/FiO₂ ≤ 315 for PaO₂/FiO₂ ≤ 300 was 83 % (95 % confidence interval (CI) 68–93), and 50 % (95 % CI 1–99), respectively. Sensitivity and specificity of SpO₂/FiO₂ ≤ 235 for PaO₂/FiO₂ ≤ 200 was 70 % (95 % CI 47–87), and 90 % (95 % CI 68–99), respectively. For pulmonary ultrasound assessments interpreted by the study physician, the sensitivity and specificity of ultrasound interstitial syndrome bilaterally and involving at least three lung fields were 80 % (95 % CI 63–92) and 62 % (95 % CI 49–74) for radiographic criteria for ARDS. Combining SpO₂/FiO₂ with ultrasound to determine oxygenation and radiographic criteria for ARDS, the sensitivity was 83 % (95 % CI 52–98) and specificity was 62 % (95 % CI 38–82). For moderate–severe ARDS criteria (PaO₂/FiO₂ ≤ 200), sensitivity was 64 % (95 % CI 31–89) and specificity was 86 % (95 % CI 65–97). Excluding repeat assessments and independent interpretation of ultrasound images did not significantly alter the sensitivity measures.ConclusionsPulse oximetry and pulmonary ultrasound may be useful tools to screen for, or rule out, impaired oxygenation or lung abnormalities consistent with ARDS in under-resourced settings where arterial blood gas testing and chest radiography are not readily available.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0995-5) contains supplementary material, which is available to authorized users.