控制性肺膨胀对急性肺损伤绵羊吸痰后肺复张容积的影响

目的　探讨控制性肺膨胀 (sustainedinflation ,SI)对急性肺损伤 (acutelunginjury ,ALI)绵羊吸痰后肺复张容积的影响。方法　内毒素静脉注射复制绵羊ALI模型 ,进行两组吸痰 ,SI组吸痰后立即予以一次SI,用P -V曲线法测定吸痰前后肺复张容积 ,同时观察吸痰前后动脉血氧合的变化。结果　非SI组吸痰前肺复张容积 (98 8± 77 6 )ml,吸痰后 3min显著降低 (6 4 3ml± 5 3 0ml,P <0 0 5 )。SI组吸痰后3min、 15min肺复张容积分别为 (12 8 1± 78 0 )ml和 (119 4± 6 1 5 )ml,均较吸痰前 (6 8 0± 5 0 3)ml显著增加 (P <0 0 5 )。非SI组动脉血氧分压 (PaO2 )在吸痰前为 (82 2± 4 6 9)mmHg ,叹痰后 15min显著降低为 (71 2± 30 3)mmHg (P <0 0 5 ) ;SI组吸痰前后PaO2 无明显变化。结论　吸痰可加重肺泡塌陷 ,SI可明显促进肺泡复张。     

常频叠加高频振荡通气对肺损伤大鼠氧合及通气的影响

目的观察常频叠加高频振荡通气对急性肺损伤大鼠氧合和通气的影响。方法以15只Wistar大鼠为实验对象,给予机械通气,用生理盐水肺灌洗制作急性肺损伤大鼠模型,先后行常频机械通气(CMV参数:FiO2 100%、f 30 bpm、PEEP 6 cmH2O、I∶E 1∶2、MAP 12 cmH2O)、高频振荡通气(HFOV参数:FiO2 100%、f 11 Hz、Paw 12 cmH2O、Ti 33%)、常频叠加高频振荡通气(CMV+HFOV参数同前)各1 h,监测动脉血气。计算PaO2/FiO2、氧合指数(OI)、肺内血分流率(Qs/Qt)。结果损伤前、CMV、HFOV、CMV+HFOV各指标变化:(1)PaCO2分别为(41.04±3.94)mmHg、(100.5±28.73)mmHg、(82.06±22.87)mmHg及(54.01±19.32)mmHg,损伤后均显著高于损伤前(P<0.01);CMV+HFOV显著低于CMV、HFOV(P<0.01);CMV、HFOV两者差异无统计学意义(P>0.05)。(2)PaO2/FiO2分别为(467.9±47.71)mmHg、(105.3±25.39)mmHg、(131.2±67.72)mmHg、(216.3±76.84)mmHg,损伤后均显著低于损伤前(P<0.01);CMV+HFOV显著高于CMV、HFOV(P<0.01);CMV、HFOV两者差异无统计学意义(P>0.05)。(3)OI分别为1.88±0.30、8.84±2.15、6.16±3.19、4.60±1.71,损伤后均显著高于损伤前(P<0.01);CMV+HFOV、HFOV显著低于CMV(P<0.01);CMV+HFOV、HFOV两者差异无统计学意义(P>0.05)。(4)Qs/Qt分别为0.11±0.02、0.29±0.02、0.26±0.05及0.24±0.04,损伤后显著高于损伤前(P<0.01);各通气模式差异无统计学意义(P>0.05)。结论常频叠加高频振荡通气在促进肺损伤大鼠CO2排出及改善氧合方面优于单纯常频通气和单纯高频通气。     

控制性肺膨胀对急性肺损伤患者肺气体交换及氧代谢的影响

目的　通过观察控制性肺膨胀 (SI)同小潮气量通气模式结合对急性肺损伤 (ALI)患者肺气体交换及氧代谢的影响 ,探讨SI的疗效及其最佳压力值。方法　选择严重创伤并发ALI的患者 31例 ,确诊ALI后 2 4h内入重症监护室 (ICU)予机械通气治疗。先予小潮气量通气模式 (基础阶段 )通气 1h ,然后分别给予 2 0cmH2 O× 30s(SI1 )、30cmH2 O× 30s(SI2 )、40cmH2 O× 30s(SI3)、50cmH2 O× 30s(SI4 )的SI各通气 1h ,在基础通气 1h、SI后 1h以及回到基础通气 1h各时点监测肺气体交换及氧代谢指标。结果　与基础通气模式相比 ,SI1 及SI2 后各指标无明显变化 ,SI3和SI4 后氧分压 (PaO2 )显著提高 ,分别由(92 0± 1 4 2 )mmHg上升至 (1 2 1 3± 1 6 9)mmHg和 (1 2 0 4± 1 7 0 )mmHg ,P <0 0 1 ,氧输送指数 (DO2 I)也显著提高 ,肺内分流率(Qs/Qt)显著减少 ,而当SI结束后 ,所有数据均回到基础通气状态。并且我们发现SI3和SI4 对氧合的改善作用无显著性差异。结论　SI同小潮气量通气模式结合治疗ALI患者时 ,可显著改善肺气体交换及氧合功能。 40cmH2 O为SI的最佳压力值     

高频振荡通气及肺泡表面活性物质对吸入性损伤兔肺组织的影响

目的 比较高频振荡通气(HFOV)与HFOV联合肺泡表面活性物质(PS)对重度蒸汽吸入性肺损伤兔肺组织的保护作用.方法 将24只新西兰大白兔制成重度蒸汽吸入性肺损伤模型后,按随机数字表法分为3组,每组8只.分别给予常规机械通气(CMV)、HFOV、HFOV+气管内滴入外源性PS(100 mg/kg)治疗;通气4 h后处死动物,取肺组织观察组织病理变化,并行肺组织损伤评分.结果 肺大体标本、光镜下及电镜下均观察到HFOV后肺损伤程度较CMV明显减轻,3组中以HFOV+PS组损伤最轻,CMV组损伤最重;肺组织损伤评分也显示CMV组最高[(3.71±0.43)分],HFOV+PS组最低[(2.08±0.28)分],HFOV组居中[(2.87±0.26)分],两两比较差异均有统计学意义(P<0.05或P<0.01).结论 与CMV比较,HFOV通过减少肺组织内炎性细胞浸润及水肿液的渗出,可减轻吸入性肺损伤,且HFOV联合PS作用最明显.     

控制性肺膨胀对急性肺损伤绵羊吸痰后动脉氧合的影响

目的探讨控制性肺膨胀 (SI)对急性肺损伤 (ALI)绵羊吸痰后动脉血氧合与肺机械力学的影响。方法内毒素持续静脉注射制备绵羊ALI模型 ,分为SI组与非SI组 ,SI组在吸痰后立即实施一次SI ,观察两组吸痰后动脉血氧合改变与肺机械力学改变。结果非SI组动脉血氧分压 (PaO2 )吸痰前为 1 0 9± 6 2 5kPa ,吸痰后 3min为 1 0 9± 6 2 4kPa ,较吸痰前无明显改变 ;在吸痰后 1 5min明显降低为 (9 4 9± 4 0 1 (P <0 0 5 )。SI组吸痰后PaO2较吸痰前无明显下降 (P >0 0 5 ) ;与非SI组相比 ,SI组在吸痰后 1 5minPaO2 有显著升高 (P <0 0 5 )。非SI组吸痰前静态肺顺应性 (Cst)为 2 0 6± 0 5 89ml/kPa ,在吸痰后 3min显著降低为 1 8 5± 0 4 82ml/kPa(P <0 0 5 )。SI组在吸痰前Cst为 2 0 1± 5 80ml/kPa,吸痰后 3和 1 5min显著增加至 2 5 5± 0 879ml/kPa和 2 4 2± 0 6 88ml/kPa(P <0 0 5 )。在吸痰后两组气道阻力均明显降低 (P <0 0 5 )。结论在吸痰后给予SI可以纠正吸痰所导致的低氧     

高频振荡结合部分液体通气治疗急性呼吸衰竭兔的实验研究

目的探讨高频振荡通气（HFOV）结合高氟碳化合物（PFC）对重度蒸汽吸入性肺损伤导致的急性呼吸衰竭兔的呼吸功能及IL-10、IL-18的影响。方法将24只新西兰大白兔制成重度蒸汽吸入性肺损伤并急性呼吸衰竭模型，随机分为常规机械通气（CMV）组、HFOV组和HFOV＋PFC组，分别在治疗后1、2、3、4h取动脉血行血气分析，治疗4h后抽血处死动物，ELISA法测定血清中IL-10、IL-18水平，右肺中叶取标本，行病理学检查。结果3组兔伤后PaO2均降至60mmHg（1mmHg=0．133kPa）以下，各组伤前、伤后比较均有显著性差异（P〈0.01），组问比较差异无统计学意义（P〉0.05）。3组兔伤后PaCO2均升高，pH值均降低，各组伤前、伤后比较有显著性差异（P〈0.01），组间比较无差异（P〉0.05）。治疗1h时3组的PaO2均有上升，HFOV＋PFC组上升最为明显，HFOV＋PFC组明显高于HFOV组（P〈0.01），HFOV组明显高于CMV组（P〈0.01）。治疗4h后3组PaO2均有所改善，HFOV＋PFC组高于相应时相HFOV组（P〈0.01），HFOV组高于相应时相CMV组（P〈0．01）。治疗4h后3组兔pH值、PaCO2与致伤后比较差异无统计学意义（P〉0.05）；血清中IL-10水平：HFOV＋PFC组高于HFOV组（P〈0.01），HFOV组高于CMV组（P〈0．01）；血清中IL-18水平：HFOV＋PFC组低于HFOV组（P〈0.01），HFOV组低于CMV组（P〈0．01）；肺组织病理学检查发现HFOV组的损伤程度较CMV组减轻，HFOV＋PFC组损伤最轻，CMV组损伤最重。结论HFOV结合PFC可显著改善蒸汽吸人性损伤导致的急性呼吸衰竭兔的PaO2，并能在更短的时间内达到最佳气体交换状态，改善呼吸功能。还可提高血清中IL-10水平，降低血清中IL-18水平，从而减轻肺部炎症反应，减轻肺损伤，是治疗急性呼吸衰竭兔较好的方法。     

创伤后急性肺损伤患者行俯卧位通气的研究

目的　探讨俯卧位通气对ALI/ARDS患者的治疗作用。方法　 1998年 7月至 2 0 0 0年 5月收入我院EICU的创伤所致ALI/ARDS患者 2 8例 ,在一定的镇静和肌松下进行俯卧位通气 ,分别监测初始仰位、俯位 1h、俯位 2h、仰位 1h、仰位 2h各时点的血流动力学、呼吸力学及血气分析指标。结果　患者转为俯位后 ,氧合状况显著改善 (PaO2 /FiO2 从 2 0 5 3± 5 7 4升至 2 5 7 0± 2 8 7、 2 73 3± 31 8,P <0 0 5 ) ,且在复转为仰位后 2h持续存在 (PaO2 /FiO2 )为 2 42 1± 6 0 5 ,P <0 0 5 ) ;Bp、HR、Paw、R、C、PaCO2 及血气指标在体位变动前后无明显变化。结论　俯卧位通气能显著改善ALI/ARDS病人的氧合状况 ,对血流动力学、呼吸力学无明显影响 ,可用于ALI/ARDS的辅助治疗     

机械通气联合肺表面活性物质、氟碳吸入治疗呼吸衰竭的研究

目的 研究高频振荡通气(high frequency oscillatory ventilation,HFOV)和常频机械通气(conventional mandatory ventilation,CMV)分别联合肺表面活性物质(pulmonary surfactant,PS)、部分液体通气(partial liquid ventilation,PLV)治疗急性呼吸衰竭的治疗效果.方法 将48只新西兰大白兔制备成吸入性损伤并呼吸衰竭模型后按随机数字表法分成6组:CMV组、CMV+PLV组、CMV+PS组、HFOV组、HFOV+PS组及HFOV+PLV组,每组各8只.分别采用6种方法进行通气(CMV、CMV+PS、CMV+PLV、HFOV、HFOV+PS、HFOV+PLV)治疗,对各组各时间点(治疗前,治疗后0.5、1.5、2.5、3.5 h)的PaCO2、PaCO2、心率及平均动脉压的变化进行比较.结果 6组动物通气治疗0.5 h PaO2后均明显升高,与治疗前比较差异均有统计学意义(均P<0.01).通气治疗1.5、2.5 h后CMV+PLV组、CMV+PS组、HFOV组、HFOV+PS组及HFOV+PLV组的PaO2均高于CMV组(P<0.05或P<0.01).通气治疗3.5 h CMV组、CMV+PLV组、CMV+PS组、HFOV组的PaO2均低于HFOV+PS组及HFOV+PLV组(均P<0.01).6组治疗后各时间点的PaCO2、心率及平均动脉压变化与治疗前比较差异无统计学意义(均P＞0.05).结论 与其他通气模式相比,HFOV联合PS、氟碳能提高呼吸衰竭兔的氧合水平.     

容积保证压力支持通气时不同水平恒定供气流量对呼吸衰竭患者肺力学的影响

目的　探讨在容积保证压力支持 (VAPS)通气时不同水平的恒定供气流量 (CF)对呼吸衰竭患者肺力学参数的影响。方法　呼吸衰竭患者 14例 ,其中男性 11例 ,女性 3例 ,年龄 (6 7± 2 )岁。基础疾病为慢性阻塞性肺疾病 (COPD) 8例 ,急性肺损伤 (ALI) 6例 ,所有患者均接受气管插管及机械通气支持 2 4h以上。保持患者处于镇静状态 ,首先应用定容型通气模式 (VCV) ,潮气量 (VT) 7～ 9ml/kg;随后转为VAPS通气 ,吸气压 (Pinspl)等于VCV时的Pplat,CF分别为 15L/min和 10L/min ,最后予以压力支持通气 (PSV)。COPD呼吸衰竭患者在沙丁胺醇 6 0 0 μg后重复上述各模式通气。 结果　与VCV相比 ,COPD患者在VAPS通气时的气道峰压 (PSV)以及峰压与气道平台压之差 (PIP Pplat)明显降低 ,在VT 相近的情况下 ,平均吸气流量 (VT/TI)呈显著下降 [(17 8± 3 6 )L/min (CF为 15L/min) ,(13 6± 2 7)L/min (CF为10L/min)与 (31 3± 2 9)L/min (VCV) ],而与PSV时相近 (均P <0 0 5 )。吸入沙丁胺醇后 ,VAPS时的吸气峰流量 (PIF)明显增高 [(2 7 1± 1 3)L/min与 (937 1± 1 9)L/min ,P <0 0 5 ) ],但PIP与PIP Pplat却进一步降低。ALI患者在VAPS时的PIF增高最为明显 ,CF为 10L/min时PIP Pplat降至 (1 2± 0 3)cmH2 O ,此时CF/PIF为     

高频振荡通气治疗新生儿重症呼吸衰竭

目的　探讨高频振荡通气 (HFV)治疗重症呼吸衰竭的疗效。方法　 1 3例重症呼吸衰竭新生儿 ,平均胎龄 33± 4周 ,体重 1 93± 0 85kg ,RDS 9例 ,先天性膈疝 4例 ,经常规机械通气 (CMV)治疗失败后改为HFV治疗 ,治疗过程中监测心率、血压、动脉血气及氧合指数等。结果　 1 3例患儿用HFV后 2h动脉血氧饱和度 (SaO2 )均≥ 0 90 ;在实施HFV治疗 8h后 ,平均气道压 (MAP)由 0 1 6 5± 0 0 38kPa降至 0 1 0 5± 0 0 4 6kPa(q =4 0 3,P <0 0 1 ) ;动脉肺泡氧分压 (a/A)由 (0 0 8± 0 0 2 )升至 (0 2 4± 0 1 1 )q=8 35 ,P <0 0 1 ) ,氧合指数 (OI)由 (30± 1 3)降至 (1 0± 4 ) (q =8 1 6 ,P <0 0 1 ) ;所需氧浓度 (FiO2 )亦由 (0 90± 0 1 0 )显著降至 (0 6 2± 0 1 7) (q =3 37,P <0 0 5 )。结论　重症呼吸衰竭用CMV无效后改用HFV可获得显著疗效 ,表现为氧合改善快、短时间内FiO2 迅速降低     

单向活瓣通气给氧在机械通气患者撤机中的应用研究

目的探讨在机械通气患者撤机过程中,使用单向活瓣通气给氧的方法对脱机训练的影响。方法选择行机械通气72 h以上患者48例,符合撤机标准,在准备撤机前将患者随机分成观察组和对照组各24例,观察组使用单向活瓣通气给氧的方法对患者进行脱机训练,对照组采用常规氧气管给氧通气的方法,通过观察两组患者的血气分析、呼吸频率、心率、血压变化,并了解患者的耐受性及舒适度改变等指标。结果两组患者在脱机后1 h3、h2、4 h动脉血气分析的血氧分压(PaO2)、动脉血氧饱和度(SaO2)、呼吸次数、心率、血压变化相比较,差异有显著性意义(P<0.05)。观察组患者的耐受性及舒适度明显比对照组好。结论使用单向活瓣通气给氧用于机械通气患者撤机的方法,可以使患者能吸入较精确的足够的氧混合气体,降低导管死腔,减少患者的呼吸做功,增加患者的舒适度,从而能使患者达到快速、顺利脱机的目的。     

胸科手术单肺通气期间定容模式和定压模式的比较

目的比较胸科手术单肺通气（OLV）期间采用定容（VCV）和定压（PCV）两种不同通气模式的效果。方法ASAⅠ～Ⅱ级、年龄18～68岁需行单肺通气胸科手术患者24例，随机分为Ⅰ、Ⅱ两组，每组各12例。全身麻醉诱导插双腔管后，侧卧位行双肺定容通气（TLV-VCV）后Ⅰ组先单肺定容通气（OLV—VCV）30min后行单肺定压通气（OLV—PCV），Ⅱ组单肺通气的顺序与Ⅰ组相反，即先定压通气（OLV—PCV）30min再定容通气（OLV—VCV）。双肺定容通气后，每种单肺通气后30min测定并记录心率（HR）、平均动脉压（MAP）、中心静脉压（CVP）、脉搏氧饱和度（SpO2）、气道峰压（Ppeak）、平均气道压（Pmean）、潮气量（VT）、呼吸末二氧化碳分压（PETCO2）。同时抽动血测血氧分压、氧饱和度（PaO2、SaO2）及二氧化碳分压（PaCO2）。结果患者TLV-VCV，OLV-VCV与OLV-PCV期间的HR、MAP、CVP、SpO2差异无统计学意义（P〉0．05）；OLV-VCV和OLV-PCV的Ppeak和Pmean较TLV-VCV高（P〈0．05或P〈0．01），而OLV—VCV又比OLV-PCV高（P〈0．05或P〈0．01）；OLV．PCV的PaO2较OLV-VCV高（P〈0．01），三种通气的VT、Sa02、PET，CO2、PaCO2差异无统计学意义（P〉0．05）。结论单肺定压通气效果优于单肺定容通气。     

Mouth-to-mouth ventilation is superior to mouth-to-pocket mask and bag-valve-mask ventilation during lifeguard CPR: a randomized study

Aim

The quality of cardiopulmonary resuscitation (CPR) is a crucial determinant of outcome following cardiac arrest. Interruptions in chest compressions are detrimental. We aimed to compare the effect of mouth-to-mouth ventilation (MMV), mouth-to-pocket mask ventilation (MPV) and bag-valve-mask ventilation (BMV) on the quality of CPR.

Materials and methods

Surf lifeguards in active service were included in the study. Each surf lifeguard was randomized to perform three sessions of single-rescuer CPR using each of the three ventilation techniques (MMV, MPV and BMV) separated by 5 min of rest. Data were obtained from a resuscitation manikin and video recordings.

Results

A total of 60 surf lifeguards were included (67% male, 33% female, mean age 25 years). Interruptions in chest compressions were significantly reduced by MMV (8.9 ± 1.6 s) when compared to MPV (10.7 ± 3.0 s, P < 0.001) and BMV (12.5 ± 3.5 s, P < 0.001). Significantly more effective ventilations (visible chest rise) were delivered using MMV (91%) when compared to MPV (79%, P < 0.001) and BMV (59%, P < 0.001). The inspiratory time was longer during MMV (0.7 ± 0.2 s) and MPV (0.7 ± 0.2 s, P < 0.001 for both) compared to BMV (0.5 ± 0.2 s). Tidal volumes were significantly lower using BMV (0.4 ± 0.2 L) compared to MMV (0.6 ± 0.2 L, P < 0.001) and MPV (0.6 ± 0.3 L, P < 0.001), whereas no differences were observed when comparing MMV and MPV.

Conclusion

MMV reduces interruptions in chest compressions and produces a higher proportion of effective ventilations during lifeguard CPR. This suggests that CPR quality is improved using MMV compared to MPV and BMV.     

Comparison of automated and manual ventilation in a prehospital pediatric model

Objective. Portable transport ventilators (TV) and demand valves (DV) may be effective and easy-to-use alternatives to bag-valve (BV) for prehospital ventilation of adults. The purpose of the study was to determine whether such devices maintain arterial blood gases and airway pressures similar to those for BV in a pediatric swine model. Method. This study was a prospective, randomized, crossover design using immature swine (9.6 ± 0.9 kg) to model ventilation in small children. Anesthetized, intubated, paralyzed, and cannulated animals were ventilated initially on standard mechanical hospital ventilation (HV). They were then assigned in random order to 10-minute intervals of ventilation using BV, TV, low-frequency jet ventilation (JV), and DV. Data were analyzed using repeated-measures ANOVA and Tukey multiple comparisons (alpha = 0.05). Results. The PaO₂ exceeded 90 mm Hg for all animal/ventilation combinations. Blood PaCO₂ was lower for BV and DV than it was for TV, JV, or HV. In contrast, blood pH was higher for BV and DV than it was for TV, JV, or HV. Peak airway pressure was higher for BV than it was for HV, TV, or JV; it was lower for JV than it was for HV, TV, or BV. Conclusion. This animal model suggests that automated TV and JV may provide more effective ventilation of children than do manual BV or DV devices. Although promising, these findings require application in children under prehospital emergent conditions.     

Noninvasive pressure support versus proportional assist ventilation in acute respiratory failure

Background Although conventional pressure ventilation (PSV) decreases the rate of intubation in acute respiratory failure, patient-ventilator dyssynchrony is a frequent cause of failure. In proportional assist ventilation (PAV), pressure is applied by the ventilator in proportion to the patient-generated volume and flow; therefore, there is automatic synchrony between the patient's effort and the ventilatory cycle.Objective The aim of this study was to compare the effects of PSV and PAV during noninvasive ventilation in the treatment of acute respiratory failure.Design Prospective randomised study.Setting A multidisciplinary 24-bed intensive care unit of an acute-care teaching hospital in Alicante, Spain.Patients This study included 117 consecutive adult patients with acute respiratory failure randomised to noninvasive ventilation delivered by PSV (n = 59) or PAV (n = 58).Measurements and results There were no statistically significant differences between patients assigned to each mode of ventilation with regard to baseline parameters and aetiological diagnoses of acute respiratory failure. With regard to outcome data, no significant differences were observed between PSV and PAV in the frequency of intubation (37% vs 34%), mortality rate (29% vs 28%), and mean length of stay. Subjective comfort (0–10 visual analogue scale) was rated higher and intolerance occurred less frequently (3.4% vs 15%, P = 0.03) in the PAV than in the PSV mode.Conclusions Although PAV seems more comfortable and intolerance occurred less frequently, no major differences exist in terms of physiological improvement or in terms of outcomes when comparing PSV and PAV.An editorial regarding this article can be found in the same issue ()     

Performance of noninvasive ventilation modes on ICU ventilators during pressure support: a bench model study

Objective Noninvasive ventilation (NIV) is often applied with ICU ventilators. However, leaks at the patient-ventilator interface interfere with several key ventilator functions. Many ICU ventilators feature an NIV-specific mode dedicated to preventing these problems. The present bench model study aimed to evaluate the performance of these modes. Design and setting Bench model study in an intensive care research laboratory of a university hospital. Methods Eight ICU ventilators, widely available in Europe and featuring an NIV mode, were connected by an NIV mask to a lung model featuring a plastic head to mimic NIV conditions, driven by an ICU ventilator imitating patient effort. Tests were conducted in the absence and presence of leaks, the latter condition with and without activation of the NIV mode. Trigger delay, trigger-associated inspiratory workload, and pressurization were tested in conditions of normal respiratory mechanics, and cycling was also assessed in obstructive and restrictive conditions. Results On most ventilators leaks led to an increase in trigger delay and workload, a decrease in pressurization, and delayed cycling. On most ventilators the NIV mode partly or totally corrected these problems, but with large variations between machines. Furthermore, on some ventilators the NIV mode worsened the leak-induced dysfunction. Conclusions The results of this bench-model NIV study confirm that leaks interfere with several key functions of ICU ventilators. Overall, NIV modes can correct part or all of this interference, but with wide variations between machines in terms of efficiency. Clinicians should be aware of these differences when applying NIV with an ICU ventilator. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A comparison of continuous positive pressure ventilation,combined high frequency ventilation and airway pressure release ventilation on experimental lung injury

In pigs with oleic induced lung injury, the effectiveness of combined high frequency ventilation (CHFV, with VDR-Phasitron) and airway pressure release ventilation (APRV) were compared to continuous positive pressure ventilation (CPPV) in a randomized study. The respiratory rate was 15/min, CPAP 8 mmHg and FiO₂ 0.25. PaCO₂ was maintained at 5 kPa. PaO₂ was significantly lower with APRV (12.5±3.9 kPa, CPPV: 15.8±3.9 kPa, and CHFV: 15.5±3.2 kPa). This was in accordance with the lowest peak airway pressure during APRV (20.9±4.8 mmHg, CPPV: 26.3±4.4 mmHg and CHFV: 28.2±3.7 mmHg). There was no difference in the pericardiac pressure between the 3 ventilation modes. The pressure related depressive effects on the cardiovascular function during CHFV and APRV were similar to those during CPPV. Adequate oxygenation and ventilation could be achieved with both CHFV and APRV, but these methods were not superior to CPPV.The study was supported by Instrumentariumin Tiedesäätiö     

Haemodynamic performance and weaning from mechanical ventilation following open-heart surgery

Summary In 38 patients ventilated after open-heart surgery the effect of a 20 minutes spontaneous breathing period on right atrial pressure (RAP), left atrial pressure (LAP), pulmonary artery pressure (PAP), aortic pressure (AoP), ECG and cardiac index (CI) was monitored. Arterial bloodgas analysis before and during spontaneous breathing ruled out any respiratory failure. The test period of spontaneous breathing provoked an increase in systemic and pulmonary vascular resistance. By this and by a direct aggravation of cardiac failure the work of both ventricles dropped inspite of an increase in end-diastolic ventricular pressure. If these hemodynamic effects of a spontaneous breathing test period are taken as a guide for deciding, if a patient after open-heart surgery is ready for being extubated, the need for reintubation will be extremely rare. The study encourages us to use mechanical ventilation as an additional instrument for treating heart failure even if no respiratory failure is present.