Inert gas analysis of ventilation-perfusion matching during hemodialysis

The mechanism of hypoxemia during hemodialysis was investigated by the multiple inert gas elimination technique in anesthetized, paralyzed, mechanically ventilated dogs. Profound leukopenia occurred in the first hour of a 2-h hemodialysis with a cuprophan membrane and dialysate that contained acetate. Arterial partial pressure of O2 and CO2 and oxygen consumption remained unchanged during dialysis. Pulmonary carbon dioxide elimination and lung respiratory exchange ratio decreased with the initiation of dialysis, remained depressed throughout the duration of dialysis, and returned to predialysis levels after the cessation of dialysis. Cardiac output diminished during dialysis but did not return to base-line levels after dialysis. Multiple indices calculated from inert gas analysis revealed no ventilation-perfusion mismatching during dialysis. The shunt and perfusion to regions of low alveolar ventilation-to-perfusion ratio (VA/Q) were unchanged during dialysis. There was no change in the mean or standard deviation of the profile of the percentage of total perfusion to regions of the lung that had VA/Q near 1.0; nor was there any increase in the directly calculated arterial-alveolar partial pressure differences for the inert gases during dialysis. Dead space became mildly elevated during dialysis. These results show that during dialysis with controlled ventilation there is no ventilation-perfusion mismatching that leads to hypoxemia. During spontaneous ventilation any hypoxemia must occur due to hypoventilation secondary to the CO2 exchange by the dialyzer and subsequent reduction in pulmonary CO2 exchange.     

Continuous positive airway pressure is beneficial in treatment of smoke inhalation

This study demonstrates that continuous positive airway pressure (CPAP) improves pulmonary function after smoke inhalation by dogs. Sixteen dogs were anesthetized with iv sodium pentobarbital. Arterial and mixed venous blood gas tensions; carboxyhemoglobin concentration (COHgb); mean systemic arterial (MAP), mean pulmonary arterial (MPAP), and pulmonary arterial wedge (WP) pressures; heart (HR) and respiratory (f) rates; cardiac output (CO); and airway pressure (Paw) were measured. Intrapulmonary physiologic shunt (Qsp/Qt) and pulmonary (PVR) and systemic (SVR) vascular resistances were calculated. The animals then breathed an aerosol of smoke and were divided randomly into 2 groups. The treatment group breathed spontaneously on 8-torr CPAP whereas the control group continued to breathe spontaneously at ambient pressure. After inhalation of smoke, Qsp/Qt, MPAP, PVR, COHgb, HR, and f rose, whereas PaO2 and MAP fell in untreated animals. When CPAP was applied, PaO2 and Qsp/Qt returned nearly to baseline values. Mean f also was significantly lower in the treated animals. We found that the early institution of CPAP improves oxygen exchange in the lungs after the inhalation of smoke.     

Mechanisms producing hypoxemia during hemodialysis

Arterial hypoxemia occurs frequently during hemodialysis. Proposed mechanisms for this phenomenon have included hypoventilation and embolism of granulocyte aggregates. We studied 18 patients with endstage renal failure who required chronic hemodialysis, and measured arterial blood gases, pulmonary gas exchange, and dialyzer gas exchange. During use of acetate as a dialysate buffer, PaO2 decreased to 80 +/- 6.8 torr, whereas during use of the bicarbonate buffer oxygen tension remained at 92 +/- 4.9 torr or greater. Hypoventilation and microembolism were not sufficient to explain the degree of hypoxemia during acetate dialysis. Hypoxemia occurred only after the 1st exposure to acetate; neither an instantaneous change to bicarbonate nor stopping dialysis restored oxygen tension to normal. We conclude that a pharmacologic action of acetate adversely affects lung function, aggravating the decreased alveolar oxygen tension (PAO2) due to hypoventilation. Hypoxemia was not present when bicarbonate was used. Acetate buffer should not be used for dialysis in patients with unstable cardiovascular or respiratory systems.     

The hazardous effects of alveolar hypocapnia on lung mechanics during weaning from cardiopulmonary bypass

The bronchoconstrictive effects of alveolar hypocapnia during weaning from cardiopulmonary bypass (CPB) were investigated in patients undergoing elective coronary artery revascularization. Thirty patients were randomly assigned into two equal groups. In both groups, mechanical ventilation was initiated for 3 min prior to weaning from CPB with the venous pressure low. This kept the pulmonary vascular bed empty, resulting in alveolar hypocapnia (ETCO2 < 2 kPa). Peak airway pressure (P(peak)) and plateau pressures (P(plateau)) were recorded. In group 1, 5% CO2 was added to the inspiratory gas mixture and the ETCO2 allowed to rise (ETCO2 > 3.3 kPa). The ventilation pressure measurements were recorded again after 3 min stabilization. In group 2, the venous pressure was increased to allow the pulmonary venous bed to fill and the ventilation pressures recorded after a 3 min period of stabilization. In group 1, the ventilatory pressures dropped significantly (p < 0.001) when the alveolar hypocapnia was reversed with added CO2 (P(peak) 19.71 +/- 5.7 to 12.31 +/- 2.8 cmH2O and P(plateau) 13.15 +/- 3.28 to 9.15 +/- 2.23 cmH2O). In group 2, a similar effect was achieved by allowing filling of the pulmonary vascular bed (P(peak) 17.46 +/- 4.72 to 11.92 +/- 3.03 cmH2O and P(plateau) 13.93 +/- 4.10 to 9.37 +/- 3.00 cmH2O). These results suggest that filling the pulmonary vascular bed prior to initiating ventilation, when weaning from CPB, prevents the otherwise deleterious effects of alveolar hypocapnia, resulting in raised bronchomotor tonus and raised airway pressures.     

俯卧位通气对急性肺损伤和急性呼吸窘迫综合征临床疗效影响的Meta分析

目的 系统评价俯卧位通气(PPV)对我国急性肺损伤(ALI)和急性呼吸窘迫综合征(ARDS)患者的短期临床疗效.方法 利用Cochrane系统评价法,全面检索2000年至2009年国内公开发表的所有ALI与ARDS患者PPV的临床研究资料.对纳入研究独立进行质量评价、资料提取、交叉核对后行Meta分析.结果 纳入研究8项共184例患者,PPV时患者动脉血氧分压(PaO2)、氧合指数(PaO2/FiO2)、呼吸系统总顺应性(C)均显著升高;动脉血二氧化碳分压(PaCO2)、中心静脉压(CVP)、呼吸道峰压(PIP)和呼吸系统总阻力(Raw)无显著的变化;心率(HR)与平均动脉压(MAP)显著升高. 结论 ALI与ARDS患者行PPV可增加呼吸系统总顺应性,改善患者低氧血症,相关临床研究结果基本一致.但因Meta分析的自身局限性,我们仍急需开展设计严谨的高质量大样本临床研究,明确PPV临床疗效、作用机制、科学的操作流程及PPV对患者血流动力学的影响等临床实际问题,改善国内ALI与ARDS患者的临床护理水平.     

持续高容量血液滤过对急性呼吸窘迫综合征合并多器官功能障碍综合征患者的治疗作用

目的 探讨持续高容量血液滤过(HVHF)对急性呼吸窘迫综合征(ARDS)合并多器官功能障碍综合征(MODS)患者血管外肺水和呼吸功能的影响.方法 将41例确诊为ARDS合并MODS患者随机分为对照组(20例)和HVHF治疗组(21例).HVHF组给予24 h的HVHF(6 L/h)治疗;放置PiCCO导管,监测心排血量(CO)、血管外肺水指数(EVLWI)和胸腔内血容量指数(ITBVI)的变化,记录气道峰压(Ppeak)、肺顺应性(Cdyn)和血气分析结果;用酶联免疫吸附法(ELISA)检测治疗前后细胞因子肿瘤坏死因子-α(TNF-α)和白细胞介素-6(IL-6)的变化.结果 对照组治疗前后各指标均无明显改善(P均>0.05).HVHF治疗后24 h,CO明显下降,EVLWI减少,ITBVI趋向稳定;TNF-α、IL-6浓度明显降低,Ppeak和Cdyn改善,氧合指数明显提高,与HVHF治疗前及对照组比较差异均有统计学意义(P均<0.05).结论 HVHF能够清除ARDS合并MODS患者的血管外肺水,降低炎症介质,改善呼吸功能,提高抢救成功率.     

Cardiopulmonary effects of the alpha2-adrenoceptor agonists medetomidine and ST-91 in anesthetized sheep

To test the hypothesis that pulmonary alterations are more important than hemodynamic changes in alpha2-agonist-induced hypoxemia in ruminants, the cardiopulmonary effects of incremental doses of (4-[1-(2,3-dimethylphenyl)ethyl]-1H-imadazole) hydrochloride (medetomidine; 0.5, 1.0, 2.0, and 4 micrograms/kg) and 2-(2, 6-diethylphenylamino)-2-imidazol (ST-91; 1.5, 3.0, 6.0, and 12 micrograms/kg) were compared in five halothane-anesthetized, ventilated sheep using a placebo-controlled randomized crossover design. Pulmonary resistance (RL), dynamic compliance, and tidal volume changes in transpulmonary pressure (DeltaPpl) were determined by pneumotachography, whereas cardiac index (CI), mean pulmonary artery pressure (Ppa), and pulmonary artery wedge pressure (Ppaw) were determined using thermodilution and a Swan-Ganz catheter. The most important finding was the fall in partial pressure of oxygen in arterial blood (PaO2) after administration of medetomidine at a dose (0.5 micrograms/kg) 20 times less than the sedative dose. The PaO2 levels decreased to 214 mm Hg as compared with 510 mm Hg in the placebo-treated group. This decrease in PaO2 was associated with a decrease in dynamic compliance and an increase in RL, DeltaPpl, and the intrapulmonary shunt fraction without changes in heart rate, CI, mean arterial pressure, pulmonary vascular resistance, Ppa, or Ppaw. On the other hand, ST-91 only produced significant changes in PaO2 at the highest dose. After this dose of ST-91, the decrease in PaO2 was accompanied by a 50% decrease in CI and an increase in mean arterial pressure, Ppa, Ppaw, and the intrapulmonary shunt fraction without significant alterations of RL and DeltaPpl. The study suggests that the mechanism(s) by which medetomidine and ST-91 produce lower PaO2 are different and that drug-induced alterations in the pulmonary system are mainly responsible for the oxygen-lowering effect of medetomidine.     

Alveolar opening maneuver (mobilization) in intraoperative pulmonary oxygenizing dysfunction in cardiosurgical patients

The purpose of the study was to investigate arterial oxygenation and hemodynamics during and after alveolar mobilization in the early post-cardiopulmonary bypass (CPB) period of cardiac surgery. The study involved 21 patients aged 30 to 73 years, who had a PaO2/FiO2 below 300 mm Hg in the early post-CPB period. PaO2/FiO2 was less than 200 mm Hg in 4 patients. Alveolar mobilization was performed by means of the "Open lung tool" function of a Servo-i respirator ("Maquet'). PaO2/FiO2 significantly increased (P < 0.5) from 244+/-11 to 472+/-20 mm Hg and thoracopulmonary compliance (Cdyn) increased from 53.3+/-3 to 67.5+/-2.9 ml/cm H20 (p < 0.5). Intrapulmonary shunt (Qs/Qt) significantly decreased from 14+/-1 to 10+/-1.5% (p < 0.5). The mean values of PaO2/FiO2 Cdyn and Qs/Qt were stable at the end of procedures. PaO/FiO, was greater than 350 mm Hg in 62% of the patients. Cardiac index considerably decreased from 2.7+/-0.1 to 225+/-0.1 l/min/m(2) at the peak of alveolar mobilization (p < 0.05); right atrial pressure and mean pulmonary artery pressure were moderately, but significantly higher at that moment. Hemodynamic parameters returned to the baseline levels after alveolar mobilization. There were no significant hemodynamic complications. It is concluded that alveolar mobilization is an effective technique in improving arterial oxygenation and lung biomechanics in cardiosurgical patients under anesthesia.     

Ventilatory support by tracheal gas insufflation and chest vibration during bronchoconstriction

OBJECTIVE: To determine whether chest wall vibration with tracheal gas insufflation during bronchoconstriction maintains gas exchange at lower airway and intrathoracic pressures than those that occur during positive pressure ventilation. DESIGN: Prospective study. SETTING: Experimental laboratory. SUBJECTS: Six anesthetized, paralyzed mongrel dogs (mean weight, 24.7+/-3.8 kg). INTERVENTIONS: Dogs were ventilated by two methods: mechanical ventilation (7 breaths/min, 25 mL/kg tidal volume); and tracheal oxygen insufflation at 0.15 L x kg(-1) x min(-1) delivered with external chest wall vibration (29 Hz, 2 mm amplitude) of the dependent hemithorax. Bronchoconstriction was induced by methacholine infusion adjusted to double and quadruple the baseline airway resistance. Proximal mean airway pressure was kept equal for both modes of ventilation. MEASUREMENTS AND MAIN RESULTS: Airway pressure and flow, esophageal pressure, hemodynamic variables (cardiac output, systemic and pulmonary arterial pressures, pulmonary artery occlusion pressure) and gas exchange variables (PaO2, PaCO2, pH, shunt fraction, VO2) were measured. Peak airway pressure was lower (p < .05) with insufflation and vibration than with mechanical ventilation by 83.6% at baseline resistance, by 76.9% at twice baseline resistance, and by 76.8% at four times baseline resistance. Peak esophageal pressure was lower (p < .05) during insufflation with vibration by 68.5% at baseline resistance, by 87.5% at twice baseline resistance, and by 107% at four times baseline resistance. During insufflation with vibration, mild hypercapnia (PaCO2 58+/-3 torr (7.7+/-0.4 kPa) and pH 7.28+/-0.02) developed with moderate bronchoconstriction; more profound respiratory acidosis (PaCO2 137+/-41 torr (18.2+/-5.5 kPa) and pH 6.87+/-0.11) developed with severe bronchoconstriction. CONCLUSIONS: Tracheal gas insufflation with chest vibration supports gas exchange with permissive hypercapnia only during moderate, not severe, bronchoconstriction. Gas exchange was achieved at lower airway and intrathoracic pressures than those that developed during mechanical ventilation. The alveolar hypoventilation that occurred during insufflation with vibration indicates impaired CO2 elimination and suggests increased resistance to CO2 transport. This ventilation technique may confer therapeutic advantages over mechanical ventilation in the treatment of asthma.     

大剂量盐酸氨溴索联用乌司他丁改善百草枯中毒患者肺损伤

目的 评价大剂量盐酸氨溴索(AMB)联用乌司他丁(UTI)改善百草枯(PQ)中毒患者肺损伤的临床应用价值.方法 对402例PQ中毒患者,198例实施常规治疗(对照组),204例实施大剂量AMB联合UTI治疗(联用组),分别通过检测患者的动脉血氧分压(PaO2)及肺部影像学改变,比较两组ARDS及MODS发生率,综合评估肺损伤的情况.结果 联用组低氧血症、ALI/ARDS发生率均低于对照组(P＜0.05)；影像学表现明显减轻.入院时即出现MODS伴(或不伴)ARDS者病情发展迅速,预后不良.结论 早期应用大剂量AMB联用UTI能减轻PQ对肺组织的损伤,促进肺泡或肺间质渗出液的吸收,减少肺纤维化的形成.     

Percutaneous transtracheal ventilation: effects of a new oxygen flow modulator on oxygenation and ventilation in pigs compared with a hand triggered emergency jet injector

The application of percutaneous transtracheal jet ventilation for emergency ventilation depends on special equipment which is often not available outside the operating room. The oxygen flow modulator is a new specially designed device for emergency ventilation using a low pressure oxygen supply. We studied the effects of the new device in comparison with a hand triggered emergency jet injector on oxygenation and ventilation in six pigs (21+/-1 kg). The animals were anaesthetized, tracheally intubated, and mechanically ventilated. Following central venous and pulmonary artery catheterization, a Paratrend 7 sensor was placed in the left femoral artery for continuous measurements of PaO(2) and PaCO(2). Then an emergency transtracheal airway catheter was inserted into the trachea after surgical exposure. In randomized order each animal was ventilated via the transtracheal airway catheter with the hand triggered emergency jet injector (inspiratory/expiratory (I/E) ratio of 1:1; respiratory rate of 60 min(-1); driving pressure 1.5 bar; FjetO(2) 1.0) and the oxygen flow modulator (FiO(2) 1.0 at an oxygen flow of 15 l min(-1); respiratory rate of 60 min(-1); I/E ratio of approximately 1:1) for 15 min each. After each phase of the experiment respiratory and hemodynamic variables were measured. Whereas PaO(2) was not significantly different between the two devices, PaCO(2) was higher during the hand-triggered jet ventilation. Thus, the efficacy of the oxygen flow modulator during the experiment was comparable with the efficacy of the hand triggered emergency jet injector.     

多指标评估犬内毒素性ARDS模型

目的 :建立犬内毒素性ARDS模型。方法 :选择健康成年毕格犬 12条 ,分两次静脉注射内毒素 ,动态观察氧合指数(PaO2 /FiO2 ) ;肺血管阻力指数 (PVRI) ;肺内分流率 (Qs /Qt) ;动态顺应性 (Cdyn) ;气道阻力 (Rrs) ;死腔量 (VD/VT) ;支气管肺泡灌洗液 (BALF)中总磷脂 (TPL)、饱和磷酸 (DSPC)、总蛋白 (TP)及表面张力 ;外周血中性粒细胞计数 ;肺组织形态学 ;X线胸片变化等指标判断肺损伤程度。结果 :(1)所有动物在 36h左右出现ARDS ,表现为PaO2 /FiO2 从 4 6 8降至 193mmHg ,Cdyn从 1.4 7降至 0 .85 (ml /cmH2 O .kg) ,VD/VT从 0 .14增加至 0 .5 7,Qs /Qt从 4 .75上升至 38% ,PVRI (dyne.sec /cm5/m2 )从 15 8增加至 5 70 ;(2 )BALF中TPL、DSPC明显降低 ,TP明显增加 ,最小表面张力 >2 0mN /m ;(3)外周血中性粒细胞明显减少 ;(4)X线胸片示两肺弥漫性阴影 ;(5 )两肺充血、出血及散在脓栓灶 ,肺泡及肺间质水肿 ,透明膜形成 ,中性粒细胞浸润 ,终末支气管上皮细胞变性坏死 ,肺不张 ,肺内斑片状出血 ,内皮细胞肿胀及空泡变性。结论 :(1)区别与其它实验研究 ,静脉输注内毒素致犬肺损伤达ARDS需一定时间 ;(2 )肺毛细血管内皮细胞功能失常 ,肺泡表面活性物质系统受损 ;中性粒细胞在肺内聚集参与ARDS的形成     

持续气管内吹气在急性肺损伤幼猪通气中的作用

目的 观察持续气管内吹气联合保护性低通气压控制通气对内毒素诱导急性肺损伤幼猪的疗效.方法 12只上海小白猪,内毒素60 μg,/ks静脉维持诱导肺损伤.随机(随机数字法)分为单纯机械通气组(MV,n=6)和联合气管内吹气组(TGI,n=6).呼吸机设置参数为吸气峰压10cmH2O(1 cmH2O=0.981 kPa);呼吸末正压2 cmH2O;呼吸频率30次/min,吸气时间0.4 s;流速20 L/min.TGI组经留置婴儿胃管给予2 L/min空气吹入,调节呼吸机吸氧浓度使吸入混合气体所测氧浓度为0.4.记录牛命体征、中心静脉压、通气功能和呼吸力学参数及动脉血气分析.结果 急性肺损伤成模后4 h,与MV组比较,TGI组呼气潮气量、通气效率指数显著升高(P<0.01),平均气道阻压下降(P<0.05).动脉血气分析提示TGI组pH值明显纠正,二氧化碳分压显著下降(P<0.01);同时氧分压、氧合指数显著改善(P<0.05).但两组心率、呼吸频率、动脉压、中心静脉压、肺顺应性和平均气道阻力差异均无统计学意义.组织学检查提示TGI组肺组织炎症程度及出血状况明显减轻.结论 持续气管内吹气可以显著提高急性肺损伤机械通气效率,促进二氧化碳排出,并改善氧合能力,在急性肺损伤治疗中具有一定的应用前景.     

Effect of continuous positive-pressure ventilation on oxygenation after pulmonary microemboli in dogs

We infused starch microemboli (63 to 74-mu diameter) into the external jugular vein of 28 dogs, to observe the effects of continuous positive-pressure ventilation (CPPV) on gas exchange and hemodynamics during hypoxemia (PaO2 53 +/- 3 torr). CPPV at both 10 and 15 cm H2O end-tidal pressure improved PaO2. CPPV 15 returned PaO2 and pulmonary shunt to control values but reduced cardiac output, O2 transport, and O2 consumption. In spite of these changes suggesting inadequate tissue oxygenation with CPPV 15, mixed venous oxygenation was not reduced. We conclude that: (a) hypoxemia after microemboli infusion is improved by CPPV and therefore likely caused by ventilation/perfusion abnormalities; (b) the improvement in PaO2 produced by CPPV after microemboli is not beneficial if CPPV reduces perfusion and O2 transport; and (c) mixed venous oxygenation does not appear to be an adequate measure of oxygen transport to tissues when CPPV is applied in this high pulmonary vascular resistance setting.     

高容量血液滤过对脓毒症合并急性呼吸窘迫综合征血流动力学和氧代谢的影响

目的探讨连续性高容量血液滤过(HVHF)对严重脓毒症合并急性呼吸窘迫综合征(ARDS)的呼吸、血流动力学和氧代谢的影响。方法选择由各种病因导致的12例脓毒症并发ARDS患者,全部病例均在呼吸机支持下每日连续给予床边HVHF(置换液流量80ml·kg-1·h-1)治疗12~18h,观察治疗前后患者炎性介质〔肿瘤坏死因子α(TNFα)、白细胞介素6(IL6)、IL8、IL10〕、氧合指数(PaO2/FiO2)、急性生理学与慢性健康状况评分系统(APACHE)评分、多器官功能障碍综合征(MODS)评分和胸腔液体容量(TFC)的变化。通过Swan Ganz导管获得心排血量(CO)、外周循环阻力(SVR)、肺循环阻力(PVR)、平均肺动脉压(MPAP)、肺动脉楔压(PAWP)、动脉血氧含量(CaO2)、混合静脉血氧含量(CvO2)、氧消耗(VO2)、氧输送(DO2)和氧摄取率(O2ER)。结果HVHF48h后的MPAP、PVR和TFC均明显下降(P均<0.05)。HVHF72h后,TNFα、IL6和IL8含量较HVHF前均明显下降(P均<0.05),DO2、O2ER和VO2逐渐稳定,并伴随动脉氧分压(PaO2)、PaO2/FiO2和气道峰压(Ppeak)的改善(P<0.05或P<0.01)。结论连续性HVHF可通过清除部分细胞因子,减少TFC,改善严重脓毒症合并ARDS患者的呼吸、血流动力学和氧代谢。     

便携式纤支镜肺泡灌洗对老年肺部感染呼吸衰竭有创机械通气患者降钙素原和超敏C反应蛋白的影响及治疗价值

目的探讨便携式纤支镜肺泡灌洗对老年肺部感染呼吸衰竭有创机械通气患者血清降钙素原(PCT)和超敏C反应蛋白(hs-CRP)的影响及治疗价值。方法 80例老年肺部感染合并呼吸衰竭有创机械通气治疗的患者,予以抗感染、扩张气道、祛痰和营养支持等治疗,对照组40例予以常规吸痰管吸痰治疗,观察组40例加用便携式纤支镜经气管导管吸痰和支气管肺泡灌洗、两天1次。治疗前及治疗1周后检测患者的血清PCT、hs-CRP、白细胞(WBC)、中性粒细胞比例(N)、动脉氧分压(PaO_2)、动脉血二氧化碳分压(Pa CO_2),比较两组治疗前后各指标的变化;观察并比较两组患者有创通气时间、住院时间、病死率和并发症。结果治疗1周后PCT、hs-CRP、WBC、N、PaO_2和Pa CO2与治疗前比较两组均有明显改善(P0.05),观察组治疗后各指标改善明显优于对照组(P0.05);有创通气时间、住院时间和病死率比较,观察组明显低于对照组(P0.05)。两组并发症比较差异无统计学意义(P0.05)。结论便携式纤支镜肺泡灌洗可使老年肺部感染呼吸衰竭有创机械通气患者的血清PCT和hs-CRP明显下降,治疗安全有效,具有重要的临床应用价值。     

Hemodynamic effects of high-frequency jet ventilation in dogs with a chronically banded pulmonary artery

Two to seven weeks after banding the main pulmonary artery, the hemodynamic effects of high-frequency jet ventilation (HFJV) and conventional mechanical ventilation (CMV) were studied in dogs with and without PEEP. In comparison with CMV, HFJV significantly increased cardiac index, stroke index (SI), left ventricular stroke work index, and oxygen delivery index, and decreased pulmonary vascular resistance index both with and without PEEP; however, there were significant decreases in PaO2 and increases in intrapulmonary physiologic shunt ratio in HFJV without PEEP. SI without PEEP was significantly greater with HFJV when the peak airway pressure was synchronized with the diastole in pulmonary arterial pressure (PAP) than with CMV and with HFJV synchronized with the systole in PAP. These findings suggest that HFJV has hemodynamic advantages over CMV in dogs with chronically banded pulmonary artery and dilated right ventricle.     

Partial liquid ventilation combined with kinetic therapy in acute respiratory failure in piglets

OBJECTIVE: To investigate the effect of the combination of kinetic therapy (KT) with partial liquid ventilation (PLV) on gas exchange, lung mechanics and hemodynamics in acute lung injury (ALI). DESIGN: Prospective, randomized, controlled pilot study. SETTING: University research laboratory. SUBJECTS: Eleven piglets weighing 8.3+/-0.9 kg. INTERVENTION: ALI was induced by the infusion of oleic acid (0.08 ml/kg) and repeated lung lavages with 0.9% NaCl (20 ml kg(-1)). Thereafter the animals were randomly assigned either for PLV or a combination of PLV with KT (PLV/KT). The dose of perfluorocarbon administered was 30 ml/kg, evaporative losses were substituted with 5 ml/kg per h. MEASUREMENTS AND MAIN RESULTS: Airway pressures, tidal volumes, dynamic compliance (Cdyn), expiratory airway resistance and arterial blood gases were measured. Hemodynamic monitoring included right atrial, mean pulmonary artery, pulmonary capillary wedge and mean systemic arterial pressures, and continuous flow recording of the pulmonary artery. In both groups the induction of ALI significantly reduced PaO2/FIO2 Cdyn and cardiac output, and significantly increased pulmonary artery pressure. After the initiation of PLV there was a significant increase of PaO2/FIO2, and Cdyn, and a significant decrease of pulmonary artery pressure in both groups. Except the PaCO2, which showed significantly lower values in the PLV/KT group, no variables showed any differences between the two groups. CONCLUSION: The additional use of KT did not show beneficial effects on oxygenation and lung mechanics during PLV. However, at constant minute ventilation PaCO2 levels were significantly lower during PLV/KT, indicating some positive influence on the ventilation/perfusion distribution within the lung. Extreme body positions during PLV/KT did not show any significant hemodynamic side effects.     

肺保护通气对食管癌患者术后肺部并发症的影响

目的探究肺保护通气对食管癌患者术后肺部并发症的影响。方法选取2014年1月-2017年1月该院收治的98例胸腹腔镜食管癌根治手术患者为研究对象,将患者依据随机数表法分为观察组(n=49)和对照组(n=49),两组患者术中均行单腔气管导管辅以二氧化碳CO2人工气胸,对照组患者采用传统通气模式,观察组患者采用肺保护性通气策略,比较两组患者不同时间点[气管插管后10 min(T_1);单肺通气1 h(T_2);手术结束时(T_3);术后24 h(T_4)]的肺功能指标、炎症反应、血气分析。依据患者术后是否复发肺部并发症分为复发组(n=24)和非复发组(n=74),分析肺部并发症及其相关因素。结果两组患者T_1时刻的吸气平台压(Pplat)、气道峰压(Ppeak)、气道阻力(Raw)、白细胞介素-6(IL-6)、白细胞介素-8(IL-8)、可溶性细胞间黏附分子(Sicam-1)、二氧化碳分压(PaCO_2)、血氧分压(PaO_2)和氧合指数(PaO_2/FiO_2)差异无统计学意义(P0.05);T_1~T_3之间对照组患者Pplat、Ppeak和Raw的变化幅度明显大于观察组患者,差异有统计学意义(P0.05),T_1~T_4之间对照组患者IL-6、IL-8和Sicam-1的变化幅度明显大于观察组患者,差异有统计学意义(P0.05),T_1~T_4之间对照组患者PaO_2的变化幅度明显大于观察组患者,差异有统计学意义(P0.05)。两组患者中均有部分患者存在多个肺部并发症,观察组和对照组分别有18.36%和30.61%患者合并各类肺部并发症,差异有统计学意义(P0.05)。术前吸烟、手术时间、根治程度、临床病理分期、淋巴管浸润、微血管浸润和术后辅助化疗与食管癌根治手术患者肺部并发症有密切相关性(P0.05)。结论肺保护通气能够缓解胸腹腔镜食管癌根治手术中气道阻力、压力和炎症反应,增大氧饱和度,应加强对高危肺部并发症发生率患者的监控,进行针对性预防,降低术后肺部并发症的发生率。     

Gas exchange during conventional and high-frequency pulse ventilation in the surfactant-deficient lung: influence of positive end-expiratory pressure

High-frequency pulse ventilation (HFPV) was compared to conventional ventilation (CV) in a model of severe respiratory failure induced by serial lung lavages with warm saline in 8 mongrel dogs. Before the lavage, during HFPV at 4 Hz with a pulse volume (PV) of 125 ml, mean PaO2 was 107 torr and mean PaCO2 was 34 torr. After the last lavage, during CV at an inspired oxygen fraction FIO2 of 1.0 and a tidal volume (VT) of 535 ml, the PaO2 averaged 60 torr and PaCO2 was 45 torr. At an FIO2 of 0.21, 20 cm H2O of positive end-expiratory pressure (PEEP) was applied to prevent hypoxemia. The resulting PaO2 was 87 torr; PaCO2 was 40 torr. Peak airway pressure (Ppa) rose from 21 to 51 cm H2O. When ventilation was switched to HFPV on room air, a PV similar to the control levels was associated with severe hypoxemia (PaO2 less than 45 torr, PaCO2 greater than 50 torr). As PV was increased PaO2 improved, reaching 113 torr at a PV of about 470 ml. The corresponding mean airway pressure (Paw) was about 20 cm H2O. Thus, application of PEEP during HFPV at low PV did not improve PaO2 even when measured Paw approximated 20 cm H2O. This suggests that HFPV with high PV is more effective than either CV with PEEP, or HFPV with low PV and PEEP.