容积标限压力控制通气时吸入沙丁胺醇对呼吸衰竭患者通气参数的影响

目的　探讨在容积标限压力控制 (VTPC)通气时吸入沙丁胺醇后对呼吸衰竭患者通气参数的变化。方法　 2 1例呼吸衰竭患者 ,年龄 (6 7± 4 )岁 ,均接受气管插管与机械通气支持治疗 2 4h以上 ,采用Newporte 5 0 0型呼吸机 ,先实施定容型通气 (VCV) 30min ,潮气量 (VT/Tinflation)。随后转为VTPC通气 30min ,并同样记录上述参数。通过同轴吸入装置吸入沙丁胺醇 6 0 0 μg后重复VCV和VTPC通气 ,并记录上述通气参数。结果　VCV通气时 2 1例患者的系统静志顺应性 (Cst)为 (39 2± 2 4 )ml/cmH2 O ,气道阻力(Raw)为 (19 3± 2 2 )cmH2 O/ (L·S)。VTPC时气道峰压值 (PIP)和VT/Tinflation 较VCV时显著降低 (均P<0 0 5 ) ,PIF则显著增高 ,二种通气时的平台压Pplateau差异无显著性 (2 2 4cmH2 O± 0 9cmH2 O与 2 3 2cmH2 O± 1 2cmH2 O ,P >0 0 5 )。吸入沙丁胺醇后患者的Raw有显著降低 ,而Cst无明显变化 ,VCV时的PIP有所降低 ,但Pplateau无变化 ;VTPC时的PIP和Pplateau与吸入前比较无明显改变 ,PIF由 (4 9 7± 3 0 )L/min增至 (5 3 0± 4 1)L/min (P >0 0 5 ) ,但PEF出现明显增高 (4 2 3L/min± 1 8L/min与 5 2 3L/min± 1 6L/min ,P <0 0 5 ) ,Tinflation则相应缩短 (1 9s± 0 2s与 1 2s± 0 2s,P <0     

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     

正压机械通气与膈肌起搏联合通气对呼吸衰竭患者呼吸力学的影响

目的 观察正压机械通气与膈肌起搏联合通气对呼吸衰竭(呼衰)患者呼吸力学的影响.方法 采用自身前后对照研究方法,以20例中枢性呼衰患者先使用常规正压机械通气30 min作为对照组,后改用正压机械通气与膈肌起搏联合通气30 min作为试验组,观察两种通气方式下患者的呼吸力学变化.结果 与对照组比较,试验组平均气道压(Paw,cm H2O,1 cm H2O=0.098 kPa)、平台压(Pplat,cm H2O)明显降低(Paw:6.1±1.3比7.3±1.8;Pplat:10.4±2.5比12.1±2.6,均P＜0.05),峰食道压力(PPEAK ES,cm H2O)、峰食道压力与基准食道压力差(dPES,cm H2O)负值明显增加(PPEAK ES:-8.3±1.9比-3.2±1.4;dPES:-11.2±2.6比-8.2±2.2,均P＜0.05),吸气末屏气期间的跨肺压(Ptp plat,cm H2O)、呼吸系统静态顺应性(Cst,ml/cm H2O)明显增加(Ptp plat:23.6±3.8比15.6±3.1 Cst:52.7±8.2比48.3±7.2,均P＜0.05),气道阻力(Raw,cm H2O·L-1·s-1)、肺部阻力(RL,cm H2O·L-1·s-1)无明显改变(Raw:2.1±0.5比2.3±0.4; RL:2.9±0.6比3.1±0.5,均P＞0.05),患者呼吸功(WOBp,J/L)明显增加、机械呼吸功(WOBv,J/L)明显降低(WOBp:0.18±0.03比0;WOBv:0.31±0.07比0.53±0.11,均P＜0.05).结论 正压机械通气与膈肌起搏联合通气进行呼吸支持可明显降低呼衰患者气道压力,增加胸腔内压负值和跨肺压,提高肺顺应性,并能降低机械通气作功,但对气道阻力无明显影响.

Abstract：

Objective To observe the effects of combining positive pressure ventilation with diaphragm pacing on respiratory mechanics in patients with respiratory failure. Methods Twenty patients with central respiratory failure were studied with cohorts. The effects on respiratory mechanics were respectively observed in patients in control group, in whom ventilation by positive pressure only, and patients in experimental group in whom ventilation was instituted by combining positive pressure ventilation with diaphragm pacing. Results Compared with control group, mean airway pressure (Paw, cm H2O,1 cm H2O= 0. 098 kPa) and plateau pressure (Pplat, cm H2O) were significantly decreased in experimental group (Paw: 6. 1±1.3 vs. 7. 3±1.8; Pplat: 10. 4±2.5 vs. 12. 1±2. 6, both P＜0. 05), while the nagative value of peak esophageal pressure (PPEAK ES, cm H2O), the nagative value of the difference between peak and basic esophageal pressure (dPES, cm H2O), transpulmonary pressure at end of inspiration hold (Ptp plat,cm H2O), static compliance (Cst, ml/cm H2O) were significantly increased in experimental group (PPEAKES:-8.3±1.9 vs. -3.2±1.4; dPES: -11.2±2.6 vs. -8. 2±2. 2; Ptp plat: 23.6±3.8 vs. 15.6±3.1; Cst:52. 7±8. 2 vs. 48. 3 ±7. 2, all P ＜ 0. 05 ). No differences were found in airway resistance (Raw,cm H2O · L-1 · s-1) and lung resistance (RL, cm H2O · L-1 · s-1) between experimental group and control group (Raw: 2.1±0.5 vs. 2.3±0.4; RL: 2.9±0.6 vs. 3.1±0.5, both P＞0.05). Work of breath by patient (WOBp, J/L) was significantly increased and work of breath by ventilator (WOBv, J/L) was significantly decreased in experimental group compared with control group (WOBp: 0. 18± 0. 03 vs. 0;WOBv: 0.31±0.07 vs. 0.53±0.11, both P＜0.05). Conclusion Compared with positive pressure ventilation, positive pressure ventilation combined with diaphragm pacing can decrease the Paw, increase intrathoracic negative pressure, transpulmonary pressure, and Cst, and decrease WOBv, while there is no effect on Raw and RL.     

压力控制通气与容量控制通气在俯卧位手术患者气体交换功能的Meta分析

目的采用Meta分析比较压力控制通气(PCV)与容量控制通气(VCV)在围术期俯卧位通气的效果。方法计算机检索建库至2018年3月1日PubMed、EMbase、The Cochrane Library、Wan Fang Data数据库,收集俯卧位手术机械通气中应用PCV与VCV通气模式的随机对照试验(RCT)。2名研究者分别进行数据收集、文献筛选,并采用Cochrane协作网系统对纳入文献进行质量评价,应用Rev Man 5. 3软件进行Meta分析。结果最终纳入7个RCT,共计267例患者,其中PCV组134例,VCV组133例。与VCV组比较,PCV组术中俯卧位气道峰压(WMD=-2. 08 cm H2O,95%CI:-2. 78～-1. 34 cm H2O)以及气道平台压(WMD=-1. 49 cm H2O,95%CI:-2. 81～-0. 17 cm H2O)显著降低,且PCV组术中肺动态顺应性(WMD=5. 36 m L/cm H2O,95%CI:3. 47～7. 25 m L/cm H2O)显著改善,气道平均压(WMD=0. 77 cm H2O,95%CI:0. 10～1. 45 cm H2O)较高。结论相比VCV模式,俯卧位机械通气选择PCV模式能维持相对稳定的气道参数,减少气道相关并发症的发生率。     

心肺复苏持续胸外心脏按压时呼吸机潮气量与气道高压报警值设置的研究

目的 研究持续胸外心脏按压时设置呼吸机不同潮气量(VT)与气道高压报警值对心肺复苏(CPR)效果的影响.方法 将重症医学科中40例呼吸、心搏骤停患者按随机数字表法均分为小VT通气组与常规VT通气组.两组均采用容量控制模式,小VT通气组CPR开始后呼吸机VT设置为6～7 ml/kg,高压报警值由40 cm H2O(1 cm H2O=0.098 kPa)上调至60 cm H2O;常规VT通气组CPR开始后VT值和高压报警值均保持不变(VT8 ～ 12 ml/kg,高压报警值40 cm H2O).观察对比CPR过程中呼吸机实测VT、吸气峰压(PIP),10 min、30 min时血气分析和血乳酸,以及并发症发生情况.结果 CPR 10 min后小VT通气组动脉血气分析中的5项指标[pH值、血氧分压(PaO2,mm Hg,1 mm Hg=0.133 kPa)、血二氧化碳分压(PaCO2,mm Hg)、HCO3-(mmol/L)、血氧饱和度(SaO2)]及血乳酸(mmol/L)均优于常规VT通气组(pH值:7.21 ±0.09比7.13±0.07,PaO2:45.35±5.92比40.70±4.70,PaCO2:57.10±7.59比61.60±5.47,HCO3-:18.50±3.50比14.75±2.65,SaO2:0.796±0.069比0.699±0.066,乳酸:7.07±1.60比8.13±1.56,均P＜0.05).小VT通气组复苏成功率较常规VT通气组高(45％比15％,P＜0.05);PIP(cm H2O)较常规VT通气组低(37.25±7.99比42.70±7.40,P＜ 0.05);两组均未发现气压伤.结论 CPR时呼吸机设置小VT(6～7 ml/kg)并适当上调气道高压报警值比常规VT通气方法效果更好,且气压伤发生率未见明显增加.     

肺保护性通气患者的肺动脉漂浮导管监测

目的 应用肺动脉漂浮导管研究肺保护性通气对患者的血流动力学影响.方法 24例急性呼吸衰竭患者,予机械通气治疗及肺动脉漂浮导管监测.采用自身对照研究,先予常规通气,根据潮气量(VT)及气道平台压(Pplat)的状况,分为A、B两组,A组(14例):VT 12 ml/kg,Pplat<30 cm H2O(1 cm H2O=0.098 kPa);B组(10例):VT12 ml/kg,Pplat≥30 cm H2O.监测心率(HR)、平均动脉压(MAP)、中心静脉压(CVP)、平均肺动脉压(MPAP)、肺动脉楔压(PAWP)、心排血量(CO)、心排血指数(CI).然后换用VT6 ml/kg的肺保护性通气,机械通气0.5 h后再次监测血流动力学参数.比较两组患者常规通气和肺保护性通气的血流动力学变化.结果 在常规通气更换为肺保护性通气后,A组患者的血流动力学无明显变化.而B组的HR、MAP、CI明显升高,差异有统计学意义(P<0.05);而CVP、MPAP、PAWP无明显变化.结论 为了减少机械通气时血流动力学的影响,限制Pplat比限制VT更加重要,对于血流动力学不稳定的急性呼吸衰竭患者,肺保护性通气更加安全.     

沙丁胺醇雾化联合机械通气治疗危重哮喘疗效分析

目的 观察沙丁胺醇雾化联合机械通气治疗危重哮喘的治疗效果.方法 对2009年1月至2011年1月期间高州市人民医院内科ICU收住的62例危重哮喘患者给予沙丁胺醇雾化联合机械通气治疗,观察治疗前后血气分析、吸气气道峰压(PIP)、吸气平台压(Pplat)、每分钟通气量(MV)、心率(HR)、呼吸频率(RR)的变化情况.结果 治疗后患者哮喘持续状态明显缓解,血气分析无异常,PIP、Pplat下降,MV、HR、RR明显改善.结论 对危重哮喘患者给予沙丁胺醇雾化联合机械通气治疗,临床疗效好,抢救成功率显著提高,患者经济负担减轻,值得推广应用.     

乌司他丁对重症手足口病机械通气患儿肺保护作用的临床观察

目的:探计乌司他丁(UTI)对重症手足口病(HFMD)机械通气患儿肺的保护作用.方法:将2008年5月至2010年9月在本院住院重症HFMD需行气管插管机械通气48例患儿分为对照组24例和治疗组24例.对照组给予机械通气为主的综合治疗,治疗组在对照组治疗基础上予UTI静脉注射,每12小时1次,连用5 d.比较第1天和第5天两组呼吸力学指标:分钟通气量(MV)、吸气平台压(Pplat)、吸气峰压(PIP)、气道平均压(MAP)、气道阻力(Raw)、动态顺应性(Cyd).血气指标,pH值、动脉血氧分压(PaO2)、二氧化碳分压(PaCO2)、氧合指数(OI)、呼吸指教(RI)、肺泡-动脉氧分压[P(A-a)O2]、肺内分流量(Qs)与心排出量(Qt)比值(Qs/Qt).血流动力学指标,心率(HR)、呼吸(RR)、心排量(CO)、中心静脉压(CVP).比较两组机械通气时间和住PICU时间.结果:两组治疗后MV、Pplat、PIP、MAP、Raw、Cyd、pH、PaO2、PaCO2、OI、RI、P(A-a)O2、Qs/Qt、HR、CO、CVP明显好转,治疗组与对照组比较,MV、Pplat、PIP、MAP、Raw、Cyd、OI、RI差异有统计学意义(P<0.05).结论:UTI时重症HFMD机械通气患儿的呼吸力学指标、血气指标改善明显,能缩短惠儿的机械通气时间和住PICU时间,值得在临床上应用.     

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.     

跨肺压监测设定呼吸机参数对腹腔高压模型猪血流动力学及氧代谢的作用

目的 评价通过跨肺压(Ptp)设定呼吸机参数对腹腔高压(IAH)模型猪血流动力学、氧代谢和呼吸力学的影响。方法 将6只家猪进行麻醉、气管插管后接呼吸机辅助呼吸,容量控制模式,呼吸机参数设置潮气量(VT) 10 ml/kg,呼吸频率16次/min,吸入氧浓度(FiO2)0.40,呼气末正压(PEEP)5 cm H2O(1 cm H2O=0.098 kPa)。置入动脉导管和Swan-Ganz导管,测定机械通气1h（基础值）的心率、平均动脉压(MAP)、心排血指数(CI)、中心静脉压(CVP)、肺动脉楔压(PAWP)等血流动力学指标,以及气道峰压( Ppeak)、平台压(Pplat)、胸腔内压(Pes)、肺顺应性(Cst)等呼吸力学指标,并行血气分析检查。通过腹腔内注入氮气法复制25 mm Hg(1 mm Hg =0.133 kPa)IAH模型,呼吸机参数不变,持续观察2h;随后置入食道测压管,调整PEEP使呼气末Ptp≥0（为正值）,其余呼吸机参数不变,持续观察2h。结果 6只家猪均制模成功,无一发生气压伤和死亡。与基础值比较,IAH后1h、2h模型猪心率（次/min）增快(134.3±5.8、127.3±3.3比117.7±1.5),MAP(mm Hg)、CVP(mm Hg)和PAWP(mm Hg)上升(MAP：120.7±3.8、117.3±4.8比100.4±6.6,CVP：7.3±0.3、7.6±0.9比5.6±0.2,PAWP:14.0±0.6、14.0±1.0比12.3±0.3),CI(L．min-1．kg-1)下降(0.150±0.019、0.137±0.014比0.179±0.021);Ppeak (cm H2O)、Pplat (cm H2O)、Pes(cm H2O)上升(Ppeak:46.3±2.3、47.0±3.2比11.0±1.6,Pplat：25.7±1.3、26.0±1.6比9.0±0.6,Pes：13.7±0.3、14.3±0.3比2.3±0.3),Cst (ml/cm H2O)下降（8.3±0.3、9.0±0.6比23.0±1.6）;动脉血氧分压(PaO2,mm Hg)和氧输送量(DO2,ml．min-·kg-1)均下降(PaO2：142.0±13.2、140.0±16．0比166.3±11.3,DO2：19.40±2.90、19.88±4.14比25.07±6.30),差异均有统计学意义（均P＜0.05）。与IAH常规机械通气同时间点各指标比较,通过食道压监测1h、2h时PaO2 (161.6±11.9、164．0±13.6)、DO2(21.90±6.21、21.16±2.78)以及Cst（12.0±1.6、12.7±2.9）均明显改善,CI(0.121±0.013、0.120±0.012)则进一步下降,反映组织灌注的血乳酸(mmol/L)明显下降(1.60±0.12比2.70±0.44,1.67±0.07比2.27±0.13),Pplat (31.3±3.4、31.7±3.2)显著升高,差异均有统计学意义（均P＜0.05）;而动脉血二氧化碳分压(PaCO2)、心率、MAP、CVP、PAWP则无明显变化。结论 IAH状态下通过Ptp设定呼吸机参数能改善模型猪的氧分压及Cst,对血流动力学指标影响较小。     

小潮气量结合控制性肺膨胀对肿瘤术后早期急性呼吸窘迫患者的疗效

目的 观察小潮气量结合控制性肺膨胀(SI)对肿瘤术后早期呼吸窘迫(ARD)患者的疗效及可能出现的不良反应.方法 选择中国医学科学院肿瘤医院和北京协和医院2007年1月至2009年12月收治的肿瘤术后早期ARD患者51例,术后循环稳定,因ARD而不能脱离机械通气.监测并记录其持续无创血压(NBP)、脉搏血氧饱和度(SPO2),实行肺保护性通气,予SI治疗,记录SI前及SI后10 min、24 h和48 h的呼吸末正压通气(PEEP)水平及吸入氧浓度(Fi02);监测呼吸频率(F)、气道平台压(Pplat)、吸入峰值压(Ppeak)、潮气量(VT)、呼吸系统静态顺应性(Cst)及动脉血气分析(ABG).结果应用SI后,51例肿瘤术后ARD患者Fi02、PEEP减低(F值分别为66.05、241.28,P均＜0.01);VT、Cst增加(F值分别为262.40、118.28,P均＜0.01);Ppeak、Pplat、呼吸频率下降(F值分别为88.96、83.05、57.55,P均＜0.01),动脉血气分析改善,未发生各种不良事件.结论 SI在肺保护性通气的基础上可改善肿瘤术后ARD患者的氧合.     

Independent lung ventilation in patients with unilateral pulmonary contusion. Monitoring with compliance and EtCO2

OBJECTIVE: a) to describe a non-barotraumatic ventilatory setting for independent lung ventilation (ILV); b) to determine the utility of single lung end-tidal CO(2) (EtCO(2)) monitoring to evaluate the ventilation to perfusion (V/Q) matching in each lung during ILV and for ILV weaning. DESIGN: prospective study. SETTING: general intensive care unit in a university teaching hospital. PATIENTS: twelve patients with unilateral thoracic trauma needing ILV. INTERVENTIONS AND RESULTS: ILV was started with each lung ventilated with the same tidal volume (Vt): plateau airway pressure (Pplat) was 34.2+/-3.2 cmH2O in diseased lungs (DL) and 18.1+/-1.9 cmH2O in normal lungs (NL) ( P<0.01). Static compliance (Cst) was 9.9+/-1.1 ml/cmH(2)O in DL and 19.3+/-1.7 ml/cmH(2)O in NL ( P<0.01). EtCO2 was 22.5+/-2.2 mmHg in DL and 36.6+/-1.9 mmHg in NL ( P<0.01). PaO(2)/FiO(2) was at 151+/-20. PEEP was applied on the DL and each lung was ventilated with a Vt that developed Pplat < or =26 cmH2O. With this setting, Vt given to the NL was unchanged, whereas it was reduced in the DL (238+/-30 ml vs 350+/-31 ml; P<0.01). Cst and EtCO2 were still significantly lower in the DL ( P<0.01, respectively), while the PaO(2)/FiO(2) ratio remained unchanged. Vt was then progressively increased in the DL as Pplat decreased, but remained unchanged in the NL. ILV was discontinued when Vt, Cst and EtCO(2) were the same in each lung. PaO(2)/FiO(2) ratio had then increased to 295+/-18. CONCLUSIONS: a) during ILV, adequate oxygenation and a reduction in V/Q mismatch can be obtained by setting Vt and PEEP to keep Pplat below a safe threshold for barotrauma; b) measurement of single lung EtCO2 can be useful to evaluate progressive V/Q matching.     

Effects of helium-oxygen on respiratory mechanics,gas exchange,and ventilation-perfusion relationships in a porcine model of stable methacholine-induced bronchospasm

OBJECTIVE: To explore the consequences of helium/oxygen (He/O(2)) inhalation on respiratory mechanics, gas exchange, and ventilation-perfusion (VA/Q) relationships in an animal model of severe induced bronchospasm during mechanical ventilation. DESIGN: Prospective, interventional study. SETTING: Experimental animal laboratory, university hospital. INTERVENTIONS: Seven piglets were anesthetized, paralyzed, and mechanically ventilated, with all ventilator settings remaining constant throughout the protocol. Acute stable bronchospasm was obtained through continuous aerosolization of methacholine. Once steady-state was achieved, the animals successively breathed air/O(2) and He/O(2) (FIO(2) 0.3), or inversely, in random order. Measurements were taken at baseline, during bronchospasm, and after 30 min of He/O(2) inhalation. RESULTS: Bronchospasm increased lung peak inspiratory pressure (49+/-6.9 vs 18+/-1 cm H(2)O, P<0.001), lung resistance (22.7+/-1.5 vs 6.8+/-1.5 cm H(2)O x l(-1).s, P<0.001), dynamic elastance (76+/-11.2 vs 22.8+/-4.1 cm H(2)O x l(-1), P<0.001), and work of breathing (1.51+/-0.26 vs 0.47+/-0.08, P<0.001). Arterial pH decreased (7.47+/-0.06 vs 7.32+/-0.06, P<0.001), PaCO(2) increased, and PaO(2) decreased. Multiple inert gas elimination showed an absence of shunt, substantial increases in perfusion to low VA/Q regions, and dispersion of VA/Q distribution. He/O(2) reduced lung resistance and work of breathing, and worsened hypercapnia and respiratory acidosis. CONCLUSIONS: In this model, while He/O(2) improved respiratory mechanics and reduced work of breathing, hypercapnia and respiratory acidosis increased. Close attention should be paid to monitoring arterial blood gases when He/O(2) is used in mechanically ventilated acute severe asthma.     

Effect of different inspiratory rise time and cycling off criteria during pressure support ventilation in patients recovering from acute lung injury

OBJECTIVE: With many mechanical ventilators, it is possible to modify the time to reach the selected airway pressure and the criteria for cycling off the inflation during pressure support ventilation. This study evaluated the effect of different inspiratory rise time and cycling off criteria on breathing pattern and work of breathing. DESIGN: Clinical study. SETTING: University laboratory. PATIENTS: Ten intubated patients recovering from acute lung injury (PaO2/FiO2 245 +/- 26 torr, positive end-expiratory pressure 9 +/- 3 cm H2O). INTERVENTIONS: We studied two inspiratory rise time criteria (shortest and longest, 0% and 40% of the breath cycle time) and two cycling off criteria (lowest and highest, 5% and 40% of the peak inspiratory flow) at 5 and 15 cm H2O of pressure support. Respiratory rate, tidal volume, and inspiratory and expiratory work of breathing (WOBI and WOBE) were measured. MEASUREMENTS AND MAIN RESULTS: At both levels of pressure support ventilation, the shortest inspiratory rise time significantly reduced the WOBI from 0.77 +/- 0.32 to 0.56 +/- 0.23 J/L and from 0.24 +/- 0.28 to 0.08 +/- 0.09 J/L without affecting respiratory rate or tidal volume.At 15 cm H2O of pressure support ventilation, the lowest cycling off criteria significantly reduced respiratory rate from 24.9 +/- 12.1 to 21.5 +/- 12.7 beats/min and increased tidal volume from 0.51 +/- 0.17 to 0.60 +/- 0.26 L. At both levels of pressure support ventilation, the modification of cycling off criteria did not influence WOBI and WOBE. CONCLUSIONS: Our results suggest that in patients recovering from acute lung injury during pressure support ventilation, a) the shortest inspiratory rise time reduces the WOBI; and b) at 15 cm H2O of pressure support ventilation, the lowest cycling off criteria reduces the respiratory rate and increases the tidal volume without modifying the WOBI and WOBE. Modifications of inspiratory rise time and cycling off criteria must be carefully adjusted during pressure support ventilation.     

肺部物理治疗对急性呼吸衰竭患者呼吸系统顺应性的影响

目的研究单纯肺部物理治疗和叹气通气模式对急性呼吸衰竭患者呼吸力学与血流动力学的变化。方法选取ICU中21例镇静状态、无自主呼吸、依靠机械通气容量控制（CMV）模式维持呼吸功能的患者；采用自身前后对照对21例患者随机施行肺部物理治疗和叹气呼吸模式两种干预措施，肺部物理治疗采用机械法（美国产G5振肺机），双侧振肺时间分别为3min，振动频率为10r／s（1min）→20r／s（1min）→30r／s（1min）；叹气呼吸模式通过调节潮气量来获取双倍基础潮气量，连续3个呼吸周期，然后将潮气量重新调整为基础水平。于每种干预措施后5min测量患者的呼吸力学参数和血流动力学参数。结果施行肺部物理治疗后呼吸系统顺应性（Cst）有改善（P〈0．05），血氧饱和度（saoz）增加（P〈0．05），肺部物理治疗患者心率增快（P〈0．05），对血压无影响（P〉0．05）；施行机械通气叹气模式后患者Cst降低（P〈0．05），血氧饱和度（SaO2）无变化（P〉0．05）。两种方法在改善Cst方面具显著性差异（Z=-3．638，P〈0.0001）。结论肺部物理治疗在不增加潮气量和吸氧浓度的条件下可改善急性呼吸衰竭患者Cst，提高血氧饱和度；同时也会出现心率增快的负面效果。机械通气叹气模式使急性呼吸衰竭患者Cst降低，氧合无改善。因此，肺部物理疗法对改善急性呼吸衰竭患者Cst具有积极意义。     

Effects of face mask ventilation in apneic patients with a resuscitation ventilator in comparison with a bag-valve-mask

Bag-valve-mask ventilation in an unprotected airway is often applied with a high flow rate or a short inflation time and, therefore, a high peak airway pressure, which may increase the risk of stomach inflation and subsequent pulmonary aspiration. Strategies to provide more patient safety may be a reduction in inspiratory flow and, therefore, peak airway pressure. The purpose of this study was to evaluate the effects of bag-valve-mask ventilation vs. a resuscitation ventilator on tidal volume, peak airway pressure, and peak inspiratory flow rate in apneic patients. In a crossover design, 40 adults were ventilated during induction of anesthesia with either a bag-valve-mask device with room air, or an oxygen-powered, flow-limited resuscitation ventilator. The study endpoints of expired tidal volume, minute volume, respiratory rate, peak airway pressure, delta airway pressure, peak inspiratory flow rate and inspiratory time fraction were measured using a pulmonary monitor. When compared with the resuscitation ventilator, the bag-valve-mask resulted in significantly higher (mean+/-SD) peak airway pressure (15.3+/-3 vs. 14.1+/-3 cm H2O, respectively; p=0.001) and delta airway pressure (14+/-3 vs. 12+/-3 cm H2O, respectively; p<0.001), but significantly lower oxygen saturation (95+/-3 vs. 98+/-1%, respectively; p<0.001). No patient in either group had clinically detectable stomach inflation. We conclude that the resuscitation ventilator is at least as effective as traditional bag-valve-mask or face mask resuscitation in this population of very controlled elective surgery patients.     

The effects of pressure control versus volume control assisted ventilation on patient work of breathing in acute lung injury and acute respiratory distress syndrome

BACKGROUND: Patient work of breathing (WOB) during assisted ventilation is reduced when inspiratory flow (V(I)) from the ventilator exceeds patient flow demand. Patients in acute respiratory failure often have unstable breathing patterns and their requirements for V(I) may change from breath to breath. Volume control ventilation (VCV) traditionally incorporates a pre-set ventilator V(I) that remains constant even under conditions of changing patient flow demand. In contrast, pressure control ventilation (PCV) incorporates a variable decelerating flow wave form with a high ventilator V(I) as inspiration commences. We compared the effects of flow patterns on assisted WOB during VCV and PCV. METHODS: WOB was measured with a BICORE CP-100 monitor (incorporating a Campbell Diagram) in a prospective, randomized cross-over study of 18 mechanically ventilated adult patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Tidal volume, inspiratory time, and mean ventilator V(I) were constant in each mode. RESULTS: At comparable levels of respiratory drive and minute ventilation, patient WOB was significantly lower with PCV than with VCV (0.59 +/- 0.42 J/L vs 0.70 +/- 0.58 J/L, respectively, p < 0.05). Ventilator peak V(I) was significantly higher with PCV than with VCV (103.2 +/- 22.8 L/min vs 43.8 L/min, respectively, p < 0.01). CONCLUSIONS: In the setting of ALI and ARDS, PCV significantly reduced patient WOB relative to VCV. The decrease in patient WOB was attributed to the higher ventilator peak V(I) of PCV.     

Partial liquid ventilation and positive end-expiratory pressure reduce ventilator-induced lung injury in an ovine model of acute respiratory failure

OBJECTIVE: To examine the isolated and combined effects of positive end-expiratory pressure (PEEP) and partial liquid ventilation (PLV) on the development of ventilator-induced lung injury in an ovine model. DESIGN: Prospective controlled animal study. SETTING: University-based cardiovascular animal physiology laboratory. SUBJECTS: Thirty-eight anesthetized supine sheep weighing 22.3 +/- 2.2 kg. INTERVENTIONS: Animals were ventilated for 6 hrs (respiratory rate, 15; FIO2, 1.0, inspiratory/expiratory ratio, 1:1) with one of five pressure-controlled strategies, expressed as peak inspiratory pressure (PIP)/PEEP: low-PIP, 25/5 cm H2O (n = 8); high-PIP, 50/5 cm H2O (n = 8); high-PIP-PLV, 50/5 cm H2O-PLV (n = 8); high-PEEP, 50/20 cm H2O (n = 7); and high-PEEP-PLV, 50/20 cm H2O-PLV (n = 7). MEASUREMENTS AND MAIN RESULTS: Compared with the low-PIP control, high-PIP ventilation increased airleak, shunt, histologic evidence of lung injury, neutrophil infiltrates, and wet lung weight. Maintaining PEEP at 20 cm H2O or adding PLV reduced the development of physiologic shunt and dependent histologic injury indexes. Neither higher PEEP nor PLV reduced the high incidence of barotrauma observed in high-PIP animals. CONCLUSIONS: We conclude that application of PLV or PEEP at 20 cm H2O may improve gas exchange and afford lung protection from ventilator-induced lung injury during high-pressure mechanical ventilation in this model.     

Adapting prognostic respiratory variables of ARDS in children to small-scale community needs

PURPOSE: The clinical literature on the incidence and subsequent mortality of adult respiratory distress syndrome (ARDS) has come primarily from the experiences of large tertiary referral centers, particularly in Western Europe and North America. Consequently, very little has been published on the incidence, management, and outcome of ARDS in smaller community-based intensive care units. We aimed to delineate early clinical respiratory predictors of death in children with ARDS on the modest scale of a community hospital. MATERIALS AND METHODS: A retrospective chart review of children with ARDS needing conventional mechanical ventilation admitted to our pediatric intensive care unit from 1984 to 1997. The diagnosis of ARDS was based on acute onset of diffuse, bilateral pulmonary infiltrates of noncardiac origin and severe hypoxemia defined by partial pressure of oxygen <200 mm Hg during positive end-expiratory pressure (PEEP) of 6 cm H2O or greater for a minimum of 24 hours. Demographic, clinical, and physiological data including PaO2/ FIO2, A-aDo2, and ventilation index were retrieved. RESULTS: Fifty-six children with ARDS aged 8 +/- 5.5 years (range, 50 days to 21 years) were identified. The mortality rate was 50%. Early predictors of death included the peak inspiratory pressure (PIP), ventilation index, and PEEP on the third day after diagnosis: Nonsurvivors had significantly higher PIP (35.3 +/- 10.5 cm H2O vs 44.4 +/- 10.7 cm H2O, P < .001), PEEP (8 +/- 2.8 cm H2O vs 10.7.0 +/- 3.5 cm H2O, P < .01), and ventilation index (49.14 +/- 20.4 mm Hg x cm H2O/minute vs 61.6 +/- 51.1 mm Hg cm H2O/minute) than survivors. In contrast, PAO2/FIO2 and A-a DO2 were capable of predicting outcome by day 5 and thereafter. CONCLUSIONS: A small-scale mortality outcome for ARDS is comparable to large tertiary referral institutions. The PIP, PEEP, and ventilation index are valuable for predicting outcome in ARDS by the third day of conventional therapy. The development of a local risk profile may assist in decision-making of early application of supportive therapies in this population.