Combining Partial Liquid Ventilation and Prone Position in Experimental Acute Lung Injury

Background: Partial liquid ventilation (PLV) and prone position can improve arterial oxygen tension (PaO2) in acute lung injury (ALI). The authors evaluated additive effects of these techniques in a saline lung lavage model of ALI.

Methods: ALI was induced in 20 medium-sized pigs (29.2 +/- 2.5 kg body weight). Gas exchange and hemodynamic parameters were determined in both supine and prone position in all animals. Thereafter, one group was assigned to PLV with two sequential doses of 15 ml/kg of perfluorocarbon (n = 10); the second group was assigned to gaseous ventilation (n = 10). Gas-exchange and hemodynamic parameters were determined at corresponding time points in both groups in prone and supine position.

Results: In the PLV group, positioning the animals prone resulted in an increase of PaO2 prior to PLV and during PLV with both doses of perfluorocarbon when compared to ALI. PLV in supine position was only effective if 30 ml/kg of perfluorocarbon was applied. In the gaseous ventilation group, PaO2 increased reproducibly compared with ALI when the animals were turned prone. A significant additive improvement of arterial oxygenation was observed during combined therapy with 30 ml/kg of perfluorocarbon and prone position in the PLV group compared with either therapy alone.     

全氟化碳对体外循环肺损伤保护的实验研究

目的探讨以全氟化碳(perfluorocarbon,PFC)为媒介的部分液体通气(partial liquid ventilation,PLV)结合持续肺动脉灌注(continuous pulmonary perfusion,CPP)对体外循环(cardiopulmonary bypass,CPB)后幼猪急性肺损伤(acute lung injury,ALI)的肺组织炎性变化及气体交换的影响。方法将18只幼猪(体重为10.2±1.6kg)随机分为3组,对照组即单纯CPB组:只行单纯CPB;CPP CPB组(CPP组):在主动脉阻断期间,以20～25ml/kg.min的血液流量持续灌注肺动脉;PLV CPP CPB组(PLV组):在CPP组基础上停CPB后即刻向肺内灌入12ml/kg的PFC。分别在CPB前、停CPB即刻及停CPB后1h、2h、3h观察动脉血气指标的变化;实验结束后,取不同部位肺组织标本于光学显微镜下观察组织病理的变化。结果与对照组比较,PLV组在1h、2h、3h时点动脉血氧分压(PaO2)明显升高,动脉-肺泡氧分压梯度(AaDO2)明显降低(P<0.05),3h时动脉血二氧化碳分压(PaCO2)下降显著(P<0.05);CPP组的通气、换气功能也有明显改善;PLV组保护作用则较为明显。停CPB后,3组血液中的肿瘤坏死因子-α(TNF-α)、白细胞介素-8(IL-8)和白细胞介素-6(IL-6)均有所增加;与对照组比较,PLV组3h后TNF-α显著降低(P<0.05)。组织学检查:光学显微镜下见对照组肺组织(HE染色)细胞间黏附因子-1(ICAM-1)表达呈强阳性,PLV组及CPP组均呈弱阳性。结论以PFC为媒介的PLV结合持续肺动脉灌注介入CPB诱导的急性肺损伤,可明显地降低肺组织炎症反应和改善其肺气体交换。     

Effects of Spontaneous Breathing during Airway Pressure Release Ventilation on Intestinal Blood Flow in Experimental Lung Injury

Background: In critical illness, the gut is susceptible to hypoperfusion and hypoxia. Positive-pressure ventilation can affect systemic hemodynamics and regional blood flow distribution, with potentially deleterious effects on the intestinal circulation. The authors hypothesized that spontaneous breathing (SB) with airway pressure release ventilation (APRV) provides better systemic and intestinal blood flow than APRV without SB.

Methods: Twelve pigs with oleic acid-induced lung injury received APRV with and without SB. When SB was abolished, either the tidal volume or the ventilator rate was increased to maintain pH and arterial carbon dioxide tension constant as compared to APRV with SB. Systemic hemodynamics were determined by double indicator dilution. Blood flow to the intestinal mucosa-submucosa and muscularis-serosa was measured using colored microspheres.

Results: Systemic blood flow increased during APRV with SB. During APRV with SB, mucosal-submucosal blood flow (ml [middle dot] g-1 [middle dot] min-1) was 0.39 +/- 0.21 in the stomach, 0.76 +/- 0.35 in the duodenum, 0.71 +/- 0.35 in the jejunum, 0.71 +/- 0.59 in the ileum, and 0.63 +/- 0.21 in the colon. During APRV without SB and high tidal volumes, it decreased to 0.19 +/- 0.03 in the stomach, 0.42 +/- 0.21 in the duodenum, 0.37 +/- 0.10 in the jejunum, 0.3 +/- 0.14 in the ileum, and 0.41 +/- 0.14 in the colon (P < 0.001, respectively). During APRV without SB and low tidal volumes, the respective mucosal-submucosal blood flows decreased to 0.24 +/- 0.10 (P < 0.01), 0.54 +/- 0.21 (P < 0.05), 0.48 +/- 0.17 (P < 0.01), 0.43 +/- 0.21 (P < 0.01), and 0.50 +/- 0.17 (P < 0.001) as compared to APRV with SB. Muscularis-serosal perfusion decreased during full ventilatory support with high tidal volumes in comparison with APRV with SB.     

Comparative Effects of Vaporized Perfluorohexane and Partial Liquid Ventilation in Oleic Acid- induced Lung Injury

Background: It is currently not known whether vaporized perfluorohexane is superior to partial liquid ventilation (PLV) for therapy of acute lung injury. In this study, the authors compared the effects of both therapies in oleic acid-induced lung injury.

Methods: Lung injury was induced in 30 anesthetized and mechanically ventilated pigs by means of central venous infusion of oleic acid. Animals were assigned to one of the following groups: (1) control or gas ventilation (GV), (2) 2.5% perfluorohexane vapor, (3) 5% perfluorohexane vapor, (4) 10% perfluorohexane vapor, or (5) PLV with perfluorooctane (30 ml/kg). Two hours after randomization, lungs were recruited and positive end-expiratory pressure was adjusted to obtain minimal elastance. Ventilation was continued during 4 additional hours, when animals were killed for lung histologic examination.

Results: Gas exchange and elastance were comparable among vaporized perfluorohexane, PLV, and GV before the open lung approach was used and improved in a similar fashion in all groups after positive end-expiratory pressure was adjusted to optimal elastance (P < 0.05). A similar behavior was observed in functional residual capacity (FRC) in animals treated with vaporized perfluorohexane and GV. Lung resistance improved after recruitment (P < 0.05), but values were higher in the 10% perfluorohexane and PLV groups as compared with GV (P < 0.05). Interestingly, positive end-expiratory pressure values required to obtain minimal elastance were lower with 5% perfluorohexane than with PLV and GV (P < 0.05). In addition, diffuse alveolar damage was significantly lower in the 5% and 10% perfluorohexane vapor groups as compared with PLV and GV (P < 0.05).     

Mechanical Ventilation by EsophagealPressure Guided in Acute Lung Injury

Background：Survival of patients with acute lung injury or the acute respiratory distress syndrome （ARDS） has been improved by ventilation with small tidal volumes and the use of positive end-expiratory pressure （PEEP）; however, the optimal level of PEEP has been difficult to determine. In this pilot study, we estimated transpulmonary pressure with the use of esophageal balloon catheters. We reasoned that the use of pleuralpressure measurements, despite the technical limitations to the accuracy of such measurements, would enable us to find a PEEP value that could maintain oxygenation while preventing lung injury due to repeated alveolar collapse or overdistention.
Methods：We randomly assigned patients with acute lung injury or ARDS to undergo mechanical ventilation with PEEP adjusted according to measurements of esophageal pressure （the esophageal-pressure Cguided group） or according to the Acute Respiratory Ditress Syndrome Network standard-of-care recommendations （the control group）. The primary end point was improvement in oxygenation. The secondary end points included respiratory-system compliance and patient outcomes.
Results：The study reached its stopping criterion and was terminated after 61 patients had been enrolled. The ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen at 72 hours was 88 mm Hg higher in the esophageal-pressure-guided group than in the control group （95% confidence interval, 78.1 to 98.3; P = 0.002）.This effect was persistent over the entire follow-up time （at 24, 48, and 72 hours; P = 0.001 by repeated-measures analysis of variance）. Respiratory-system compliance was also significantly better at 24, 48, and 72 hours in the esophagealpressureCguided group （ = 0.01 by repeated- measures analysis of variance）.
Conclusions：As compared with the current standard of care, a ventilator strategy using esophageal pressures to estimate the transpulmonary pressure significantly improves oxygenation and compliance. Multicenter clinical trials are needed to determine whether this approach should be widely adopted. （ClinicalTrials.gov number, NCT00127491 .）
Recent changes in the practice of mechanical ventilation have improved survival in patients with the acute respiratory distress syndrome （ARDS）, but mortality remains unacceptably high. Whereas low tidal volumes are cleady beneficial in patients with ARDS, how to choose a positive end-expiratory pressure （PEEP） is uncertain. Ideally, mechanical ventilation should provide sufficient transpulmonary pressure （airway pressure minus pleural pressure） to maintain oxygenation while minimizing repeated alveolar collapse or overdistention leading to lung injury. In critical illness, however, there is marked variability among patients in abdominal and pleural pressures ; thus, for a given level of PEEP, transpulmonary pressures may vary unpredictably from patient to patient.
We estimated pleural pressure with the use of an esophageal balloon catheter. Although this technique has been validated in healthy human subjects and animals, it has not been systematically applied in patients in the intensive care setting. We reasoned that we could adjust PEEP according to each patient＇s lung and chest-wall mechanics. We speculated that in patients with high estimated pleural pressure who are undergoing ventilation with conventional ventilator settings, underinflation may cause hypoxemia. In such patients, raising PEEP to maintain a positive transpulmonary pressure might improve aeration and oxygenation without causing overdistention. Conversely, in patients with low pleural pressure, maintaining low PEEP would keep transpulmonary pressure low, preventing overdistention and minimizing the adverse hemedynamic effects of high PEEP.
We report the results of a randomized, controlled pilot trial involving patients with acutelung injury or ARDS. The trial compared mechanical ventilation directed by esophageal-pressure measurements with mechanical ventilation managed according to the Acute Respiratory Distress Syndrome Network （ARDSNet） recommendations. We tested the hypothesis that oxygenation in patients can be improved by adjusting PEEP to maintain positive transpulmonary pressures.     

Immediate Changes in the Pulmonary Blood Flow After Various Vascular Anastomoses in Lung Autotransplantation

The purpose of the present study was to investigate, by means of radioactive Xe 133, the different effects produced on the distribution of the pulmonary blood flow by various vascular anastomoses in lung autotransplantation.

Twenty mongrel dogs of varying weights were used. In Group I, which consisted of 7 dogs, the pulmonary artery was severed and resutured end-to-end. The distribution of the pulmonary blood flow was measured with Xe 133 pre- and postoperatively. Group II consisted of 5 dogs, whose pulmonary arteries also were severed, but a Dacron Velour patch was used in the resuturing to dilate the site of anastomosis as much as possible. The pre- and postoperative distributions were measured as for Group I. The 5 dogs of Group III were treated by severing and resuturing the pulmonary veins using the atrial cuff. The distribution of blood flow was measured as before. The remaining 3 dogs made up Group IV, the control group. Their treatment consisted of a thoracotomy incision and opening of the pleural cavity, and the closure of the incision without further interference. The pre- and postoperative distributions were measured as for the other groups. Pressure measurements revealed no pressure gradient at the anastomotic line of the pulmonary artery. Nor did the atrial suture, judging from pressure measurements, produce any constriction. The pre- and postoperative measurements with radioactive Xe 133 disclosed that thoracotomy alone did not affect the distribution of the pulmonary blood flow. Nor did the severing and resuturing of the pulmonary veins alone change the distribution. But in Group I, after the severance and end-to-end anastomosis of the pulmonary artery, a distinct, statistically highly significant fall was recorded in the distribution to the operated lung. The reduction in the blood volume was of the order of 38%. However, in the experimental animals whose pulmonary artery had been similarly severed, but where the site of anastomosis had been dilated by means of a Dacron Velour patch, the distribution did not change. The great importance of the pulmonary arterial anastomosis in the search for the causes of increased vascular resistance in autotransplantation is discussed. This detail, however, cannot be claimed to solve the whole problem.     

Effect of Increasing Perfluorocarbon Dose on ˙Va/˙Q Distribution during Partial Liquid Ventilation in Acute Lung Injury

Background: Although gas exchange during partial liquid ventilation (PLV) depends on perfluorocarbon liquid, the effect of perfluorocarbon dose on the ventilation-perfusion ([spacing dot above]Va/[spacing dot above]Q) distribution is not known. This study investigated how [spacing dot above]Va/[spacing dot above]Q distribution of an acutely injured lung is affected during PLV at increasing perfluorocarbon dose.

Methods: In eight rabbits (3.2 +/- 0.1 kg), acute lung injury (ALI) was created by repeated saline lavage (arterial oxygen partial pressure/fraction of inspired oxygen, 37 +/- 11 mm Hg). Three different doses of perfluorodecalin (9 ml/kg = low dose; 13.5 ml/kg = medium dose; 18 ml/kg = functional residual capacity [FRC] dose) were applied in random order during PLV. [spacing dot above]Va/[spacing dot above]Q distribution at different doses was evaluated by multiple inert gas elimination technique.

Results: Inert gas shunt (63 +/- 21% at ALI) decreased with increasing perfluorocarbon dose (43 +/- 21% at low dose, 29 +/- 10% at medium dose, 11 +/- 9% at FRC dose;P = 0.022). Compared with ALI (0%), the proportion of low [spacing dot above]Va/[spacing dot above]Q units was higher at all tested doses (19 +/- 10, 25 +/- 12, and 34 +/- 18%, respectively; all P < 0.05). Compared with ALI (27 +/- 14%), the proportion of normal [spacing dot above]Va/[spacing dot above]Q units was not increased at low or medium doses but was increased only at the FRC dose (45 +/- 13% ;P = 0.027).     

双水平正压通气对急性肺损伤患者血气及血流动力学指标的影响

目的探讨应用脉搏指数连续心排血量（PiCCO）容量监测仪技术研究双水平正压通气模式对急性肺损伤（ALI）患者血气及血流动力学的影响,探讨这种新型呼吸模式应用于ALI患者的临床疗效,对循环系统的影响程度,以提高ALI的治愈率。方法42例ALI患者,男27例,女15例;年龄15～75岁。按患者的入院先后顺序将40例患者（2例未完成研究）分为两组,每组20例。双水平正压通气组：入院的第1～20例患者,给予双水平正压通气呼吸支持,采用支持/时间（S/T）模式,吸气末压初始设为8～10cmH2O,逐渐增加至14～20cmH2O,以患者舒适为宜;呼气末压初设为3～5cmH2O,逐渐增加至8～12cmH2O,吸入氧浓度（FiO2）保持不变。对照组：入院的第21～40例患者,采用辅助/控制（A/C）通气模式,并依次按5cmH2O,10cmH2O,15cmH2O,20cmH2O增加呼气末正压（PEEP）,每种压力持续30min,通气支持过程中FiO2保持不变。观察两组患者的心排血量（CO）、体循环血管阻力（SVR）等血流动力学和血气指标改变。结果两组死亡13例,其中双水平正压通气组死亡5例,对照组死亡8例。死于多器官功能衰竭7例,感染性休克3例,循环衰竭3例。双水平正压通气组气管内插管时间（2.9±0.8dvs.4.2±0.9d,t=7.737,P=0.006）和住院时间（17.2±4.5dvs.18.5±3.6d,t=2.558,P=0.039）明显短于对照组。对照组：当PEEP在5～15cmH2O范围内,患者动脉血氧分压（PaO2）、氧合指数（PaO2/FiO2）随着PEEP的增高而逐渐增加（P〈0.05）;当PEEP增加至20cmH2O时CO降低,SVR、肺循环阻力（PVR）和气道峰值压（PIP）较5～15cmH2O范围时增加（P〈0.05）。双水平正压通气组：PaO2、PaO2/FiO2随着EPAP的增高而逐渐增加,当EPAP增加至10cmH2O时PaO2、PaO2/FiO2达最大值（P〈0.05）;与对照组比较PIP明显降低（t=7.831,P=0.000）。结论对ALI/急性呼吸窘迫综合征（ARDS）患者给予双水平正压通气治疗可减少对呼吸和血     

Changes in Regional Ventilation after Autologous Blood Clot Pulmonary Embolism

Background: Previous studies have suggested that pulmonary embolism (PE) and pulmonary artery occlusion result in a shift in alveolar ventilation away from unperfused regions. This study aimed to directly assess changes in regional specific ventilation (s[latin capital V with dot above]A) due to autologous blood clot PE using positron emission tomography.

Methods: Pulmonary embolism was created in six anesthetized, paralyzed, and mechanically ventilated sheep by injecting cylindrical clots of autologous blood (7 mm in diameter and height). Clots were progressively infused into a central vein until a stable mean pulmonary artery pressure between 30 and 40 mmHg was achieved. A multislice positron emission tomography camera was used to image 15 contiguous, 6.5-mm-thick transverse cross-sections of the chest beginning just above the diaphragm. s[latin capital V with dot above]A from perfused regions (s[latin capital V with dot above]A,p) was assessed as the ventilatory turnover rate of the tracer 13NN after central venous injection of 13NN-labeled saline.

Results: Pulmonary embolism obstructed flow to 64% of imaged areas. Before PE, s[latin capital V with dot above]A,p was equivalent in areas that would remain perfused and those that would become embolized after PE (0.021 +/- 0.007 vs. 0.021 +/- 0.006 s-1;P = nonsignificant). After PE, s[latin capital V with dot above]A,p of areas remaining perfused increased to 0.033 +/- 0.011 s-1 (P < 0.005). This effect on regional s[latin capital V with dot above]A,p could have been caused by active redistribution of s[latin capital V with dot above]A,p or by a reduction in tracer concentration of perfused areas due to the dead space common to perfused and embolized regions. Model simulations indicated that the common dead-space effect could only explain a small part of the s[latin capital V with dot above]A,p increase.     

Treatment of Pulmonary Hypertension and Hypoxia Due to Oleic Acid Induced Lung Injury with Intratracheal Prostaglandin E1 during Partial Liquid Ventilation

Background: Partial liquid ventilation using perfluorocarbon liquids may be of therapeutic benefit in patients with acute respiratory failure. This study investigated the effects of prostaglandin E1 (PGE1) delivered intratracheally during partial liquid ventilation on lung function and pulmonary circulation in rabbits with acute respiratory distress syndrome.

Methods: Lung injury was induced by intravenous oleic acid in adult Japanese white rabbits, 1 h after which they were divided into four groups of 10 animals. Group 1 received mechanical ventilation alone, group 2 received aerosolized PGE1 (5 [micro sign]g followed by 0.1 [micro sign]g [middle dot] kg-1 [middle dot] min-1) under mechanical ventilation combined with 5 cm H2 O positive end-expiratory pressure, and groups 3 and 4 received partial liquid ventilation with 15 ml/kg perflubron. Group 4 received a 5-[micro sign]g bolus followed by 0.1 [micro sign]g [middle dot] kg-1 [middle dot] min-1 PGE1 instilled intratracheally (not by aerosol) in combination with partial liquid ventilation. Measurements were performed at 30-min intervals for 120 min after lung injury.

Results: After lung injury, hypoxemia, hypercapnia, acidosis, and pulmonary hypertension developed in all animals and were sustained in groups 1 and 2 throughout the experiment. The partial pressure of oxygen in arterial blood of animals in group 3 improved with initiation of treatment, with statistical significance achieved at the 30 and 60 min time points as compared with controls. Group 4 animals had immediate and sustained increases in the partial pressure of oxygen in arterial blood that were significant compared with all other groups during the experiment. Statistically significant reductions in mean pulmonary artery pressure were seen only in group 4 animals compared with all other groups.     

Low Tidal Volume Reduces Lung Inflammation Induced by Liquid Ventilation in Piglets With Severe Lung Injury

Total liquid ventilation (TLV) is an alternative treatment for severe lung injury. High tidal volume is usually required for TLV to maintain adequate CO₂ clearance. However, high tidal volume may cause alveolar barotrauma. We aim to investigate the effect of low tidal volume on pulmonary inflammation in piglets with lung injury and under TLV. After the establishment of acute lung injury model by infusing lipopolysaccharide, 12 piglets were randomly divided into two groups, TLV with high tidal volume (25 mL/kg) or with low tidal volume (6 mL/kg) for 240 min, respectively. Extracorporeal CO₂ removal was applied in low tidal volume group to improve CO₂ clearance and in high tidal volume group as sham control. Gas exchange and hemodynamic status were monitored every 30 min during TLV. At the end of the study, pulmonary mRNA expression and plasmatic concentration of interleukin‐6 (IL‐6) and interleukin‐8 (IL‐8) were measured by collecting lung tissue and blood samples from piglets. Arterial blood pressure, PaO₂, and PaCO₂ showed no remarkable difference between groups during the observation period. Compared with high tidal volume strategy, low tidal volume resulted in 76% reduction of minute volume and over 80% reduction in peak inspiratory pressure during TLV. In addition, low tidal volume significantly diminished pulmonary mRNA expression and plasmatic level of IL‐6 and IL‐8. We conclude that during TLV, low tidal volume reduces lung inflammation in piglets with acute lung injury without compromising gas exchange.     

Cardiorespiratory Effects of Automatic Tube Compensation during Airway Pressure Release Ventilation in Patients with Acute Lung Injury

Background: Spontaneous breaths during airway pressure release ventilation (APRV) have to overcome the resistance of the artificial airway. Automatic tube compensation provides ventilatory assistance by increasing airway pressure during inspiration and lowering airway pressure during expiration, thereby compensating for resistance of the artificial airway. The authors studied if APRV with automatic tube compensation reduces the inspiratory effort without compromising cardiovascular function, end-expiratory lung volume, and gas exchange in patients with acute lung injury.

Methods: Fourteen patients with acute lung injury were breathing spontaneously during APRV with or without automatic tube compensation in random order. Airway pressure, esophageal and abdominal pressure, and gas flow were continuously measured, and tracheal pressure was estimated. Trans-diaphragmatic pressure time product was calculated. End-expiratory lung volume was determined by nitrogen washout. The validity of the tracheal pressure calculation was investigated in seven healthy ventilated pigs.

Results: Automatic tube compensation during APRV increased airway pressure amplitude from 7.7 +/- 1.9 to 11.3 +/- 3.1 cm H2O (mean +/- SD;P < 0.05) while decreasing trans-diaphragmatic pressure time product from 45 +/- 27 to 27 +/- 15 cm H2O [middle dot] s-1 [middle dot] min-1 (P < 0.05), whereas tracheal pressure am-plitude remained essentially unchanged (10.3 +/- 3.5 vs. 10.1 +/- 3.5 cm H2O). Minute ventilation increased from 10.4 +/- 1.6 to 11.4 +/- 1.5 l/min (P < 0.001), decreasing arterial carbon dioxide tension from 52 +/- 9 to 47 +/- 6 mmHg (P < 0.05) without affecting arterial blood oxygenation or cardiovascular function. End-expiratory lung volume increased from 2,806 +/- 991 to 3,009 +/- 994 ml (P < 0.05). Analysis of tracheal pressure-time curves indicated nonideal regulation of the dynamic pressure support during automatic tube compensation as provided by a standard ventilator.     

Set Positive End-expiratory Pressure during Protective Ventilation Affects Lung Injury

Background: The most appropriate method of determining positive end-expiratory pressure (PEEP) level during a lung protective ventilatory strategy has not been established.

Methods: In a lavage-injured sheep acute respiratory distress syndrome model, the authors compared the effects of three approaches to determining PEEP level after a recruitment maneuver: (1) 2 cm H2O above the lower inflection point on the inflation pressure-volume curve, (2) at the point of maximum curvature on the deflation pressure-volume curve, and (3) at the PEEP level that maintained target arterial oxygen partial pressure at a fraction of inspired oxygen of 0.5.

Results: Positive end-expiratory pressure set 2 cm H2O above the lower inflection point resulted in the least injury over the course of the study. PEEP based on adequate arterial oxygen partial pressure/fraction of inspired oxygen ratios had to be increased over time and resulted in higher mRNA levels for interleukin-8 and interleukin-1[beta] and greater tissue inflammation when compared with the other approaches. PEEP at the point of maximum curvature could not maintain eucapneia even at an increased ventilatory rate.     

Cerebral Blood Flow in the Acute Phase after Head Injury

In 40 comatose patients with severe head injury, cerebral blood flow (CBF) studies were performed with the 133Xenon washout technique over the most severely injured hemisphere. All patients were mildly sedated with diazepam, chlorpromazine and meperidine and subjected to respiratory support. Simultaneously with the CBF study, intraventricular pressure (IVP), systemic arterial pressure (SAP) and ventricular fluid (VF) lactate, pyruvate and pH were measured. The results indicate a positive correlation between CBF and lactate in patients with a good recovery, irrespective of the time after the trauma, and a positive correlation irrespective of outcome, if the measurements were performed more than 3 days after the trauma. In patients with mainly supratentorial lesions without signs of brain-stem lesions, CBF and CPP were positively correlated, while CBF and ICP were negatively correlated (lost autoregulation). In contradistinction, CBF was positively correlated to ICP and PaCO2 in patients with diffuse brain injury. In some cases of repeated dynamic studies, the clinical course seemed to be related to changes in the measured parameters.     

Pulmonary Blood Volume and Haemodynamic Changes During Steady Lung Inflations in Dogs

Zur Bewertung der Auswirkungen der kontinuierlichen positiven Druckatmung (CPAP) auf die Durchblutung der Lunge simulierten wir diese Situation bei 7 Hunden mit offenem und 5 Hunden mit geschlossenem Thorax durch endotracheale Anwendung konstanter Lungenblähung für kurze Perioden. Transpulmonaler Druck, sowie der transmurale linke Vorhofs- und Pulmonalarteriendruck wurden ebenso wie Blutdurchströmung von Pulmonalis und Aorta und Veränderungen des pulmonalen und des Volumens des linken Herzens Schlag für Schlag registriert.
Über transpulmonalen Drücken von 5.0 cm H₂O ± s.e. mean 1,1 waren die Anstiege des transmuralen pulmonalen enddiastolischen Drucks in linearer Beziehung zu den gleichlaufenden Erhöhungen des transpulmonalen Drucks (mittlere Neigung der Regressionsgeraden 0,73 ± s.e. mean 0,05), unabhängig von den pulmonalen Blutdurchsträmungswerten und dem Lungenabschnitt. Diese transpulmonalen Drücke bis zu 25 cm H₂O erzeugten auch lineare Verminderungen der Auswurfleistung des rechten Ventrikels und des Lungen-Linksherz-Blutvolumens. Das Verhältnis zwischen transpulmonalen Druck und dem transmuralen enddiastolischen Pulmonaldruck wird deshalb als praktisches Mass für den bei jedem Patienten zu bestimmenden optimalen Wert der CPAP vorgeschlagen, das vom Standpunkt der Kreislaufwirkung her vertreten werden kann.
Diese CPAP-Wirkungen auf die Lungendurchblutung und das pulmonale Blutvolumen stehen in Übereinstimmung mit der linearen Relation, die kärzlich für das mikrovaskulare Lungenstrombett zwischen transmuralem Kapillardruck und Abnahme der alveolaren Schichtdicke beschrieben wurde.     

Effects of Vaporized Perfluorocarbon on Pulmonary Blood Flow and Ventilation/Perfusion Distribution in a Model of Acute Respiratory Distress Syndrome

Background : Perfluorocarbon (PFC) liquids are known to improve gas exchange and pulmonary function in various models of acute respiratory failure . Vaporization has been recently reported as a new method of delivering PFC to the lung. Our aim was to study the effect of PFC vapor on the ventilation/perfusion ( A/ ) matching and relative pulmonary blood flow ( rel) distribution.

Methods : In nine sheep, lung injury was induced using oleic acid. Four sheep were treated with vaporized perfluorohexane (PFX) for 30 min, whereas the remaining sheep served as control animals. Vaporization was achieved using a modified isoflurane vaporizer. The animals were studied for 90 min after vaporization. A/ distributions were estimated using the multiple inert gas elimination technique. Change in rel distribution was assessed using fluorescent-labeled microspheres.

Results : Treatment with PFX vapor improved oxygenation significantly and led to significantly lower shunt values (P < 0.05, repeated-measures analysis of covariance). Analysis of the multiple inert gas elimination technique data showed that animals treated with PFX vapor demonstrated a higher A/ he-terogeneity than the control animals (P < 0.05, repeated-measures analysis of covariance). Microsphere data showed a redistribution of rel attributable to oleic acid injury. rel shifted from areas that were initially high-flow to areas that were initially low-flow, with no difference in redistribution between the groups. After established injury, rel was redistributed to the nondependent lung areas in control animals, whereas rel distribution did not change in treatment animals.     

失血性休克期间器官血流量的变化

本文研究了氯胺酮麻醉犬出血性休克期间器官血流量的变化。杂种犬７只，放血２６７±２０．５８ｍｌ，休克持续４５ｍｉｎ，用电磁血流量计测得失血性休克期间肝动脉血流量、门静脉血流量、右肾动脉血流量、颈内动脉血流量降低非常显著，心率显著增快。     

Pulmonary Arterial Contribution to Airway Blood Flow after Lung Transplantation in Dogs

Despite the improved success of lung transplantation, ischemia of the donor bronchus continues to be the most important factor influencing airway healing. Recent studies have shown that at the level of the mainstem bronchi the pulmonary contribution to the airway blood flow may be equivalent to or greater than the systemic contribution and could therefore assist early healing of the newly anastomosed bronchus and, in addition, might facilitate the improved healing associated with omentopexy. The aim of this study was to measure the pulmonary contribution to airway blood flow in dogs after allotransplantation of the left lung and to determine whether omentopexy might improve the healing process. Using the radioactive microsphere technique, we measured the pulmonary contribution to airway blood flow in 25 dogs l week after allotransplantation of the left lung. Half the dogs had an omental wrap around the anastomotic site. Results showed that pulmonary blood flow increased progressively from loner trachea to distal mainstem bronchus and supplied the left mainstem bronchus above as nell as below the anastomotic site. Omentopexy did not increase flow or enhance herding.