Partial liquid ventilation decreases albumin leak in the setting of acute lung injury

Perfluorocarbons decrease Chlamydophila pneumoniae-mediated inflammatory responses of rat type II pneumocytes in vitro

Chlamydophila pneumoniae alter the expression of Toll-like receptor (TLR) 4 in alveolar type II (ATII)-cells. Subsequently nuclear factor kappaB (NF-kappaB) is activated and tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein 2 (MIP-2) are produced. Perfluorocarbons (PFC) are beneficial in animals with bacterial pneumonia and reduce production of TNF-alpha. Using isolated ATII-cells, it was studied whether PFC prevent C. pneumoniae-induced TNF-alpha and MIP-2 release and what the underlying pathway is. PF5080 preincubation prevented C. pneumoniae-induced secretion of TNF-alpha (43 +/- 10 versus 661 +/- 41 pg/mL) and MIP-2 (573 +/- 41 versus 4786 +/- 502 pg/mL). The C. pneumoniae-induced 2.2-fold increase of TNF-alpha Receptor 1 expression was reduced by PF5080. C. pneumoniae reduced cytoplasmatic IkappaBalpha (3.7 +/- 0.3 versus 14 +/- 1) and increased NF-kappaB p65 (31 +/- 7.5 versus 3.6 +/- 1.1) compared with control. PF5080 prevented NF-kappaB activation. TLR4 expression was 1.5-fold higher after C. pneumoniae incubation, but remained at control levels after PF5080 pretreatment. After 24 h of C. pneumoniae incubation, in 88 +/- 6% of cells bacteria were found in the perinuclear region and in 50% of these cells bacteria adhered to cellular surface. After PF5080 preincubation, C. pneumoniae were in 32 +/- 4% attached to and in 5 +/- 1% internalized in ATII-cells. Since PF5080 was found in ATII-cell membranes, PF5080 effect could be explained by an alteration of the cellular membrane, preventing activation of the inflammatory cascade.

Liquid ventilation: an adjunct for respiratory management

Although significant advances in respiratory care have reduced mortality of patients with respiratory failure, morbidity persists, often resulting from iatrogenic mechanisms. Mechanical ventilation with gas has been shown to initiate as well as exacerbate underlying lung injury, resulting in progressive structural damage and release of inflammatory mediators within the lung. Alternative means to support pulmonary gas exchange while preserving lung structure and function are therefore required. Perfluorochemical (PFC) liquids are currently used clinically in a number of ways, such as intravascular PFC emulsions for volume expansion/oxygen carrying/angiography and intracavitary neat PFC liquid for image contrast enhancement or vitreous fluid replacement. As a novel approach to replace gas as the respiratory medium, liquid assisted ventilation (LAV) with PFC liquids has been investigated as an alternative respiratory modality for over 30 years. Currently, there are several theoretical and practical applications of LAV in the immature or mature lung at risk for acute respiratory distress and injury associated with mechanical ventilation.

Segmental hemodynamics during partial liquid ventilation in isolated rat lungs

Partial liquid ventilation (PLV) is a means of ventilatory support in which gas ventilation is carried out in a lung partially filled with a perfluorocarbon liquid capable of supporting gas exchange. Recently, this technique has been proposed as an adjunctive therapy for cardiac arrest, during which PLV with cold perfluorocarbons might rapidly cool the intrathoracic contents and promote cerebral protective hypothermia while not interfering with gas exchange. A concern during such therapy will be the effect of PLV on pulmonary hemodynamics during very low blood flow conditions. In the current study, segmental (i.e. precapillary, capillary, and postcapillary) hemodynamics were studied in the rat lung using a standard isolated lung perfusion system at a flow rate of 6 ml/min ( approximately 5% normal cardiac output). Lungs received either gas ventilation or 5 or 10 ml/kg PLV. Segmental pressures and vascular resistances were determined, as was transcapillary fluid flux. The relationship between individual hemodynamic parameters and PLV dose was examined using linear regression, with n=5 in each study group. PLV at both the 5 and 10 ml/kg dose produced no detectable changes in pulmonary blood flow or in transcapillary fluid flux (all R(2) values<0.20).

CONCLUSION

In an isolated perfused lung model of low flow conditions, normal segmental hemodynamic behavior was preserved during liquid ventilation. These data support further investigation of this technique as an adjunct to cardiopulmonary resuscitation.

Support of respiratory failure in the pediatric surgical patient

Severe respiratory failure in newborn and pediatric patients is associated with significant morbidity and mortality. Basic science laboratory investigation has led to advances in the understanding of ventilator-induced lung injury and in optimizing the supportive use of conventional ventilation strategies. Over the past few years, progress has been made in alternative therapies for supporting children and adults with severe respiratory failure. This review will focus on recent laboratory and clinical data regarding the techniques of lung protective ventilator strategies, inhaled nitric oxide, liquid ventilation, and extracorporeal life support (ECLS, ECMO). Some of these modalities are commonplace, while others may have much to offer the pediatric clinician if their benefit is clearly demonstrated in future clinical trials.

Changes in pulmonary function and oxygenation during application of perfluorocarbon vapor in healthy and oleic acid-injured animals

OBJECTIVES

To investigate the changes in pulmonary function and gas exchange during application of 18% perfluorohexane vapor in healthy and in oleic acid-injured animals and compare it with an injured control group.

DESIGN

Prospective randomized controlled study.

SETTING

Experimental research laboratory at a university medical center.

SUBJECTS

Nineteen sheep weighing 31.4 +/- 4.1 kg.

INTERVENTIONS

Lung injury was induced in 14 sheep by the intravenous injection of 0.1 mL/kg oleic acid. After establishment of lung injury (PaO(2)/F(IO(2)) ratio, <200; pulmonary artery occlusion pressure, <19 torr), seven animals were treated with 18% perfluorohexane vapor for 30 mins whereas seven animals served as controls. After the start of perfluorohexane treatment, blood gases and respiratory and hemodynamic data were collected in 10-min intervals throughout the study period of 1 hr. In addition, five healthy animals received perfluorohexane vapor for 30 mins and were followed up for 2 hrs to exclude delayed negative effects.

MEASUREMENTS AND MAIN RESULTS

Treatment of healthy animals with 18% perfluorohexane vapor was not accompanied by any significant adverse effects. It was associated with a significant decrease of alveolar-arterial oxygen difference during perfluorohexane application (p <.05). In injured animals, 18% perfluorohexane led to a sustained improvement of peak inspiratory pressures within 10 mins of treatment (p <.001). The concomitant increase in compliance was equally significant (p <.001). Significant improvements in PaO(2) occurred despite a decrease in F(IO(2)) to 0.81 at the end of vaporization.

CONCLUSION

Healthy animals tolerated perfluorohexane vapor well without significant changes in oxygenation and mechanical lung function for 2 hrs. In injured animals, application of perfluorohexane vapor primarily improved peak inspiratory pressure and compliance. The increase of oxygenation therefore could be secondary to an improvement in compliance.

Prospective, randomized, controlled pilot study of partial liquid ventilation in adult acute respiratory distress syndrome

We evaluated the safety and efficacy of partial liquid ventilation (PLV) with perflubron in adult patients with acute lung injury and the acute respiratory distress syndrome (ARDS) in a multicenter, prospective, controlled, randomized exploratory clinical trial. Ninety adult patients with PaO2/FIO2 ratios > 60 and < 300 with ARDS for no more than 24 hours were randomized to receive PLV (n = 65) with administration of perflubron through an endotracheal tube sideport or conventional mechanical ventilation (CMV, n = 25) for a maximum of five days. Although a significant reduction in progression to ARDS was noted among patients with PLV, no significant differences in the number of days free from the ventilator at 28 days (CMV = 6.7 +/- 1.8, PLV = 6.3 +/- 1.0 days, p = 0.85), the incidence of mortality (CMV = 36%, PLV = 42%, p = 0.63), or any pulmonary-related parameter were observed. During a post hoc subgroup analysis, significantly more rapid discontinuation of mechanical ventilation (p = 0.045) and a trend toward an increase in the number of days free from the ventilator at 28 days (CMV = 3.2 +/- 1.9, PLV = 8.0 +/- 2.2 days, p = 0.06) were observed during PLV among those patients under 55 years of age with acute lung injury or ARDS. Episodes of hypoxia, respiratory acidosis, and bradycardia occurred more frequently in the PLV group, but these were transient and self-limited. Further evaluation of PLV is warranted to further define beneficial effects in well-defined groups of patients and also to gain additional information regarding safety.

Partial liquid ventilation reduces release of leukotriene B4 and interleukin-6 in bronchoalveolar lavage in surfactant-depleted newborn pigs

Perfluorocarbons have been shown to reduce the inflammatory process generated by alveolar macrophages in vitro. The aim of this study was to evaluate the impact of different ventilator modalities such as partial liquid ventilation (PLV), conventional ventilation (CV), and high-frequency oscillatory ventilation (HFOV) on the release of inflammatory mediators in vivo. Acute lung injury was induced in 30 male piglets by repeated saline lavage (arterial oxygen tension, <60 mm Hg; fraction of inspired oxygen, 1.0). Thereafter, animals were randomly assigned to one of five groups of six animals each: 1) 24 h of CV; 2) 24 h of CV plus surfactant therapy (S+CV); 3) 24 h of HFOV plus surfactant therapy (S+HFOV); 4) 1 h of PLV followed by 23 h of CV (PLV); and 5) 24 h of CV without previous lung injury (control group). Piglets randomized to S+CV or S+HFOV received natural surfactant (100 mg/kg). PLV with FC-77 was started in an initial dose of 30 mL/kg over 30 min followed by 0.5 mL x kg(-1) x min(-1) for another 30 min. After 1 h of PLV the animals were conventionally ventilated for 23 h. Before acute lung injury and after 24 h the number of inflammatory cells and the levels of IL-6, leukotriene B4, and tumor necrosis factor-alpha were measured in the bronchoalveolar lavage fluid. Additionally, the oxygenation index and the histopathologic damage were evaluated. Before acute lung injury, the number of inflammatory cells and the levels of mediators in bronchoalveolar lavage fluid were not different among the groups. After 24 h, the number of granulocytes in the PLV group was as low as in the control group. leukotriene B4 and IL-6 levels were found to be elevated in all groups except the control group (p < 0.01). The release of leukotriene B4 and IL-6 was lowest in the PLV group when compared with S+HFOV, S+CV, or CV (p < 0.05). No differences among the groups were detected for tumor necrosis factor-alpha. Although the concentrations of leukotriene B4 and IL-6 after PLV were lowest in the PLV group, histopathologic evidence of damage and the oxygenation index in the PLV group did not differ from that found in the S+CV or S+HFOV groups. In conclusion, PLV with perfluorocarbons may protect the lung from acute pulmonary inflammation more effectively than CV or HFOV does.

Prevention of ventilator-induced lung injury with partial liquid ventilation

BACKGROUND/PURPOSE

Pulmonary injury from mechanical ventilation has been attributed to application of excess alveolar pressure (barotrauma) or volume (volutrauma). The authors questioned whether partial liquid ventilation (gas ventilation of the perfluorocarbon filled lung, PLV) would reduce ventilator-induced lung injury.

METHODS

A tracheostomy tube and carotid artery catheter were placed in anesthetized Sprague-Dawley rats (500 +/- 50 g). Bovine serum albumin (BSA) labeled with Iodine (I) 125 was administered intraarterially. Ventilation with tidal volume (TV) of 5 mL/kg was initiated. The rats were then selected randomly to a 30-minute experimental period of one of the following ventilation protocols: continued atraumatic gas ventilation (GV, TV, 5 mL/kg; n = 10); atraumatic gas ventilation combined with intratracheal administration of 10 mL/kg perfluorocarbon (GV-PLV, TV, 5 mL/kg, n = 10); barotrauma (BT, peak inspiratory pressure [PIP], 45 cm H(2)O; n = 10); barotrauma with PLV (BT-PLV, PIP, 45 cm H(2)O; n = 8); volutrauma (VT, TV, 30 mL/kg; n = 8); or volutrauma with PLV (VT-PLV, TV, 30 mL/kg; n = 10). Animals were killed and the amount of radiolabeled BSA in both lungs was measured and normalized to the counts in 1 mL of blood from that animal (injury index). Data were analyzed by analysis of variance (ANOVA) with post-hoc t test comparison between groups.

RESULTS

There was a significant difference in the (125)I-BSA injury index when all groups were compared (P <.001 by ANOVA). Post-hoc analysis showed a significant decrease in the injury index when comparing BT versus BT-PLV (P =.024) and VT versus VT-PLV (P =.014).

CONCLUSION

(125)I-BSA leak produced during high-pressure or high-volume mechanical ventilation is reduced by partial liquid ventilation.

Partial liquid ventilation for acute respiratory distress syndrome

PLV represents an intriguing alternative paradigm in the approach to the patient with ALI. Within the past decade, substantial information has become available regarding this technique. Clearly, PLV is feasible in patients with ALI and ARDS, and it appears to be safe with respect to short-term effects on hemodynamics and lung physiology, as well as long-term toxicity (although further research in this area is warranted). Although PLV has not yet been proven to be superior to traditional mechanical ventilation for patients with ALI or ARDS, PLV possesses an intriguing combination of physical, physiologic, and biologic effects: "Liquid PEEP" effect--e.g., more effective recruitment of dependent lung zones than achieved by gas ventilation Anti-inflammatory effects Lavage of alveolar debris Mitigation of ventilator-induced lung injury Direct anti-inflammatory effects--e.g., decreased macrophage release of proinflammatory cytokines, etc. Prevention of nosocomial pneumonia Combination with other modalities--e.g., exogenous surfactant replacement, inhaled NO, prone position Enhanced delivery of drugs or gene vectors into the lung. The results of ongoing and future clinical trials will be necessary to establish whether PLV improves clinical outcomes in patients with ALI or ARDS, or specific subgroups of such patients. Significant work also remains to be done to define the optimum dose level of PLV and the most appropriate ventilatory strategies.

Partial liquid ventilation shows dose-dependent increase in oxygenation with PEEP and decreases lung injury associated with mechanical ventilation

PURPOSE

The purpose of this article is to evaluate the effect of positive end-expiratory pressure (PEEP) during partial liquid ventilation (PLV) and to investigate if lung damage associated with mechanical ventilation can be reduced by PLV.

MATERIALS AND METHODS

Twenty-two New-Zealand white rabbits were ventilated in pressure-controlled mode maintaining constant tidal volume (10 mL/kg). Lung injury was induced by repeated saline lavage (PaO2 < 100 mm Hg). Two incremental PEEP steps maneuvers (IPSMs) from 2 to 10 cm H2O in 2 cm H2O steps were performed sequentially. The control group received the first IPSM in the supine position and were turned prone for the second IPSM. In the PLV group (n = 7), 12 mL/kg of perfluorodecalin was instilled after lung injury before the two IPSMs. The early prone group (n = 7) received both IPSMs in the prone position. Parameters of gas exchange, lung mechanics, and hemodynamics as well as pathology were examined.

RESULTS

During the first IPSM, the PLV group showed a significant increase in PaO2 after instillation of perfluorodecalin (P < .05) and then showed a dose-dependent increase in PaO2 with PEER. The control and EP groups showed improvement in PaO2 only at higher PEEP, eventually showing no intergroup differences at PEEP of 10 cm H2O. During the second IPSM only the PLV group retained its ability to increase PaO2 to the level obtained during the first IPSM (P < .05 compared with control and EP groups). During the first IPSM all three groups showed increasing trend in static compliance (Cst) with PEEP peaking at PEEP of 8 cm H2O. During the second IPSM, only the PLV group showed increase in static compliance with PEEP (P < .05 compared with other groups). Lung histology revealed significantly less hyaline membrane formation in the PLV group (P < .05).

CONCLUSION

PLV shows dose-dependent increase in oxygenation with PEEP and may reduce lung damage associated with mechanical ventilation.

Effect of partial liquid ventilation on pulmonary vascular permeability and edema after experimental acute lung injury

We evaluated the effects of partial liquid ventilation (PLV) with two different dosages of the perfluorocarbon LiquiVent (perflubron) on pulmonary vascular permeability and edema formation after oleic acid (OA)-induced acute lung injury in dogs. We used imaging with positron emission tomography to measure fractional pulmonary blood flow, lung water concentration (LWC), and the pulmonary transcapillary escape rate (PTCER) of (68)Ga-labeled transferrin at 5 and 21 h after lung injury in five dogs undergoing conventional mechanical ventilation (CMV), five dogs undergoing low-dose PLV (perflubron at 10 ml/kg), and four dogs undergoing high dose PLV (perflubron at 30 ml/kg). A positive end-expiratory pressure of 7.5 cm H(2)O was used in all dogs. After OA (0.08 ml/kg)- induced lung injury, there were no significant differences or trends for PTCER or LWC at any time when the PLV groups were compared with the CMV group. However, lung tissue myeloperoxidase activity was significantly lower in the combined PLV group than in the CMV group (p = 0.016). We conclude that after OA-induced lung injury, the addition of PLV to CMV does not directly attenuate pulmonary vascular leak or lung water accumulation. Rather, the benefits of such treatment may be due to modifications of the inflammatory response.

Advances in ventilatory support of the pediatric surgical patient

Severe respiratory failure in newborn and pediatric patients is associated with significant morbidity and mortality. Basic science laboratory investigation has led to advances both in our understanding of ventilator-induced lung injury and in optimizing the supportive use of conventional ventilation strategies. Over the past few years, progress has been made in alternative therapies for ventilating both children and adults with severe respiratory failure. This review focuses on recent laboratory and clinical data detailing the techniques of permissive hypercapnia, high frequency oscillatory ventilation, inhaled nitric oxide, intratracheal pulmonary ventilation, and liquid ventilation. Some of these modalities are becoming commonplace, and others may have much to offer the clinician if their benefit is clearly demonstrated in future clinical trials.