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. 相似文献
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. 相似文献
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). 相似文献
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. 相似文献
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). 相似文献
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. 相似文献
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. 相似文献
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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. 相似文献
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. 相似文献
Über transpulmonalen Drücken von 5.0 cm H
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. 相似文献
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. 相似文献