Partial liquid ventilation reduces pulmonary neutrophil accumulation in an experimental model of systemic endotoxemia and acute lung injury

The Role of HMGB1, a Nuclear Damage-Associated Molecular Pattern Molecule, in the Pathogenesis of Lung Diseases

Significance: High-mobility group protein box 1 (HMGB1), a ubiquitous nuclear protein, regulates chromatin structure and modulates the expression of many genes involved in the pathogenesis of lung cancer and many other lung diseases, including those that regulate cell cycle control, cell death, and DNA replication and repair. Extracellular HMGB1, whether passively released or actively secreted, is a danger signal that elicits proinflammatory responses, impairs macrophage phagocytosis and efferocytosis, and alters vascular remodeling. This can result in excessive pulmonary inflammation and compromised host defense against lung infections, causing a deleterious feedback cycle. Recent Advances: HMGB1 has been identified as a biomarker and mediator of the pathogenesis of numerous lung disorders. In addition, post-translational modifications of HMGB1, including acetylation, phosphorylation, and oxidation, have been postulated to affect its localization and physiological and pathophysiological effects, such as the initiation and progression of lung diseases. Critical Issues: The molecular mechanisms underlying how HMGB1 drives the pathogenesis of different lung diseases and novel therapeutic approaches targeting HMGB1 remain to be elucidated. Future Directions: Additional research is needed to identify the roles and functions of modified HMGB1 produced by different post-translational modifications and their significance in the pathogenesis of lung diseases. Such studies will provide information for novel approaches targeting HMGB1 as a treatment for lung diseases.

Perflubron Distribution During Transition From Gas to Total Liquid Ventilation

Total liquid ventilation (TLV) using perfluorocarbons has shown promising results for the management of neonatal respiratory distress. However, one important safety consideration for TLV is a better understanding of the early events during the transition to TLV, especially regarding the fate of residual air in the non-dependent-lung regions. Our objective was to assess perflubron distribution during transition to TLV using electrical impedance tomography, complemented by fluoroscopy, in a neonatal lamb model of induced surfactant deficiency. Eight lambs were anesthetized and ventilated in supine position. Surfactant deficit was induced by saline lung lavage. After deflation, lungs were filled with 25 ml/kg perflubron over 18 s, and TLV was initiated. Electrical impedance tomography data was recorded from electrodes placed around the chest, during the first 10 and at 120 min of TLV. Lung perfusion was also assessed using hypertonic saline injection during apnea. In addition, fluoroscopic sequences were recorded during initial lung filling with perfluorocarbons, then at 10 and 60 min of TLV. Twelve lambs were used as controls for histological comparisons. Transition to TLV involved a short period of increased total lung volume (p = 0.01) secondary to recruitment of the dependent lung regions. Histological analysis shows that TLV was protective of these same regions when compared to gas-ventilated lambs (p = 0.03). The non-dependent lung regions filled with perflubron over at least 10 min, without showing signs of overdistention. Tidal volume distribution was more homogenous in TLV than during the preceding gas ventilation. Perflubron filling was associated with a non-significant increase in the anterior distribution of the blood perfusion signal, from 46 ± 17% to 53 ± 6% (p = 0.4). However, combined to the effects on ventilation, TLV had an instantaneous effect on ventilation-perfusion relationship (p = 0.03), suggesting better coupling. Conclusion: transition to TLV requires at least 10 min, and involves air evacuation or dissolution in perflubron, dependent lung recruitment and rapid ventilation-perfusion coupling modifications. During that time interval, the total lung volume transiently increases. Considering the potential deleterious effect of high lung volumes, one must manage this transition phase with care and, we suggest using a real-time monitoring system such as electrical impedance tomography.

Apolipoprotein M Protects Against Lipopolysaccharide-Induced Acute Lung Injury via Sphingosine-1-Phosphate Signaling

It had been demonstrated that apolipoprotein M (apoM) is an important carrier of sphingosine-1-phosphate (S1P) in blood, and the S1P has critical roles in the pathogenesis of sepsis-induced acute lung injury (ALI). In the present study, we investigated whether apoM has beneficial effects in a mouse model after lipopolysaccharide (LPS)-induced ALI. Forty-eight mice were divided into two groups: male C57BL/6 wild-type (apoM^+/+) group (n = 24) and apoM gene-deficient (apoM^-/-) group (n = 24) and then randomly subdivided into four subgroups (n = 6 each) according to different intraperitoneal (i.p.) injection: control group, W146 group, LPS group, and LPS + W146 group. Serum levels of interleukin-1 beta (IL-1β) and mRNA levels of IL-1β, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), lung histology, wet/dry weight ratio, and immunohistochemistry were measured at 3 h after the baseline and compared in each group. Our results clearly demonstrated that IL-1β mRNA levels and other inflammatory biomarkers were significantly increased in the lungs of LPS-induced ALI apoM^-/- mice compared to those of the apoM^+/+ mice. Moreover, when apoM^+/+ mice were treated with W146, a S1P receptor (S1PR1) antagonist, these inflammatory biomarkers could be significantly upregulated by LPS-induced ALI. Therefore, it suggests that apoM-S1P-S1PR1 signaling might underlie the pathogenesis of ALI and apoM could have physiological benefits to alleviate LPS-induced ALI.

Effect of Perflubron-Induced Lung Growth on Pulmonary Vascular Remodeling in Congenital Diaphragmatic Hernia

PURPOSE

Congenital diaphragmatic hernia (CDH) involves lung hypoplasia and pulmonary hypertension (PH). Post-natal Perflubron ventilation induces lung growth. This phenomenon is called Perflubon-induced lung growth (PILG). However, it does not appear to ameliorate PH in CDH. We aim to determine the effect of PILG on pulmonary vascular remodeling in neonates with CDH and PH requiring extracorporeal membrane oxygenation (ECMO).

METHODS

Lung tissue from four patients was obtained, three treated with PILG + ECMO, and one maintained on conventional ventilation + ECMO (control). The distribution of collagen was assessed with Masson's trichrome stain. Immunohistochemistry was done to assess cell proliferation and immunofluorescence to assess vascular morphology.

RESULTS

Comparing PILG vs. control, there was an increase in vessel wall diameter (6.85 μm, 10.28 μm, and 10.35 μm vs. 4.34 μm), increase in collagen thickness in two PILG patients (35.66 μm, 14.23 μm, and 38.46 μm vs. 22.16 μm), and decrease in lumen diameter despite similar total area (48.99 μm, 41.74 μm, and 36.32 μm vs. 51.56 μm) for each PILG patient vs. the control patient, respectively.

CONCLUSION

PILG does not appear to improve pulmonary vascular remodeling that occurs with PH. The findings are descriptive and will require larger samples to validate the significance of the findings. Overall, further studies will be required to identify the mechanistic causes of PH in CDH to create effective treatments.

Nebulized perflubron and carbon dioxide rapidly dilate constricted airways in an ovine model of allergic asthma

Background

The low toxicity of perfluorocarbons (PFCs), their high affinity for respiratory gases and their compatibility with lung surfactant have made them useful candidates for treating respiratory diseases such as adult respiratory distress syndrome. We report results for treating acute allergic and non-allergic bronchoconstriction in sheep using S-1226 (a gas mixture containing carbon dioxide and small volumes of nebulized perflubron). The carbon dioxide, which is highly soluble in perflubron, was used to relax airway smooth muscle.

Methods

Sheep previously sensitized to house dust mite (HDM) were challenged with HDM aerosols to induce early asthmatic responses. At the maximal responses (characterised by an increase in lung resistance), the sheep were either not treated or treated with one of the following; nebulized S-1226 (perflubron + 12% CO₂), nebulized perflubron + medical air, 12% CO₂, salbutamol or medical air. Lung resistance was monitored for up to 20 minutes after cessation of treatment.

In additional naïve sheep, a segmental bronchus was pre-contracted with methacholine (MCh) and treated with nebulized S-1226 administered via a bronchoscope catheter. Subsequent bronchodilatation was monitored by real time digital video recording.

Results

Treatment with S-1226 for 2 minutes following HDM challenge resulted in a more rapid, more profound and more prolonged decline in lung resistance compared with the other treatment interventions. Video bronchoscopy showed an immediate and complete (within 5 seconds) re-opening of MCh-constricted airways following treatment with S-1226.

Conclusions

S-1226 is a potent and rapid formulation for re-opening constricted airways. Its mechanism(s) of action are unknown. The formulation has potential as a rescue treatment for acute severe asthma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0098-x) contains supplementary material, which is available to authorized users.

Toll-like receptor 4 monoclonal antibody attenuates lipopolysaccharide-induced acute lung injury in mice

Toll-like receptor 4 (TLR4) has an important role in the recognition of lipopolysaccharide (LPS) and in the activation of the inflammatory cascade. In the present study, the effect of TLR4 monoclonal antibody (mAb) on LPS-induced acute lung injury (ALI) was investigated in mice. A total of 45 male BALB/c mice were randomly divided into three groups, namely, the control (group C), sepsis (group S) and pretreatment groups (group P). Mice in group P were intraperitoneally treated with TLR4 mAb 1 h prior to the intraperitoneal administration of LPS. Following treatment with LPS for increasing times periods in groups S and P, the mRNA expression level of TLR4 in the lung tissue and the expression of inflammatory factors in the serum were analyzed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assays, respectively. The degree of pulmonary edema, expressed as (wet weight - dry weight)/wet weight, as well as the lung injury scores, observed using a light microscope, were also analyzed. The results demonstrated that intraperitoneal administration of LPS in mice increased the mRNA expression levels of TLR4, the secretion of inflammatory factors in the serum, the degree of pulmonary edema and the lung injury score in a time-dependent manner. However, pretreatment with TLR4 mAb effectively attenuated the increased mRNA expression of TLR4 and the overproduction of inflammatory factors to correct the pulmonary edema and the elevated lung injury score induced by LPS. Therefore, TLR4 plays a critical role in LPS-induced ALI, and the TLR4 mAb decreases the secretion of inflammatory factors and attenuates the degree of pulmonary edema, thereby protecting the lungs from LPS-induced ALI.

Neutrophil extracellular traps directly induce epithelial and endothelial cell death: a predominant role of histones

Neutrophils play an important role in innate immunity by defending the host organism against invading microorganisms. Antimicrobial activity of neutrophils is mediated by release of antimicrobial peptides, phagocytosis as well as formation of neutrophil extracellular traps (NET). These structures are composed of DNA, histones and granular proteins such as neutrophil elastase and myeloperoxidase. This study focused on the influence of NET on the host cell functions, particularly on human alveolar epithelial cells as the major cells responsible for gas exchange in the lung. Upon direct interaction with epithelial and endothelial cells, NET induced cytotoxic effects in a dose-dependent manner, and digestion of DNA in NET did not change NET-mediated cytotoxicity. Pre-incubation of NET with antibodies against histones, with polysialic acid or with myeloperoxidase inhibitor but not with elastase inhibitor reduced NET-mediated cytotoxicity, suggesting that histones and myeloperoxidase are responsible for NET-mediated cytotoxicity. Although activated protein C (APC) did decrease the histone-induced cytotoxicity in a purified system, it did not change NET-induced cytotoxicity, indicating that histone-dependent cytotoxicity of NET is protected against APC degradation. Moreover, in LPS-induced acute lung injury mouse model, NET formation was documented in the lung tissue as well as in the bronchoalveolar lavage fluid. These data reveal the important role of protein components in NET, particularly histones, which may lead to host cell cytotoxicity and may be involved in lung tissue destruction.

Pathophysiology of fat embolism: a rabbit model

OBJECTIVES

The objective of this study was to assess the effects of fat embolism on rabbit physiology.

METHODS

After anesthetic administration, both femoral condyles of the right knee only of 23 New Zealand white rabbits were exposed through a medial parapatellar approach to the knee. In the pulmonary fat embolism group (n = 15), the femoral canal was drilled in a retrograde fashion and then reamed and pressurized with a 1- to 1.5-mL cement injection. In the no-pressurization group (n = 4), after reaming, no cement was injected. In the control group (n = 4), the knee incision was immediately closed. Animals were then observed for 5 hours. Hemodynamics and blood gases were recorded at standard intervals. Postmortem, the lungs were removed en bloc and fixed for histologic assessment and quantitative histomorphometry.

RESULTS

Four intraoperative deaths occurred in the pulmonary fat embolism group immediately after pressurization and may have been associated with hypotension and cardiac arrest. In the pulmonary fat embolism group, pulmonary artery pressure increased, and both mean arterial pressure and PaO2 decreased after pressurization. Approximately 2% of lung volume was occupied by intravascular fat and there were no signs of perivascular inflammation. Control and no-pressurization animals remained stable throughout the experiment.

CONCLUSIONS

This model simulates pulmonary fat embolism after long-bone fractures. Despite cardiorespiratory dysfunction, there was no evidence of fat initiating pulmonary inflammation based on histologic data within the timeframe of the investigation.

An official American Thoracic Society workshop report: features and measurements of experimental acute lung injury in animals

Acute lung injury (ALI) is well defined in humans, but there is no agreement as to the main features of acute lung injury in animal models. A Committee was organized to determine the main features that characterize ALI in animal models and to identify the most relevant methods to assess these features. We used a Delphi approach in which a series of questionnaires were distributed to a panel of experts in experimental lung injury. The Committee concluded that the main features of experimental ALI include histological evidence of tissue injury, alteration of the alveolar capillary barrier, presence of an inflammatory response, and evidence of physiological dysfunction; they recommended that, to determine if ALI has occurred, at least three of these four main features of ALI should be present. The Committee also identified key "very relevant" and "somewhat relevant" measurements for each of the main features of ALI and recommended the use of least one "very relevant" measurement and preferably one or two additional separate measurements to determine if a main feature of ALI is present. Finally, the Committee emphasized that not all of the measurements listed can or should be performed in every study, and that measurements not included in the list are by no means "irrelevant." Our list of features and measurements of ALI is intended as a guide for investigators, and ultimately investigators should choose the particular measurements that best suit the experimental questions being addressed as well as take into consideration any unique aspects of the experimental design.

Effect of perfluorohexane on the expression of cellular adhesion molecules and surfactant protein A in human mesothelial cells in vitro

The intraperitoneal instillation of perfluorocarbons augmented systemic oxygenation and was protective in mesenteric ischemia-reperfusion and experimental lung injury. To study biocompatibility and potential anti-inflammatory effects of intraperitoneal perfluorocarbons, we evaluated the influence of perfluorohexane and/or inflammatory stimuli on human mesothelial cells in vitro. Perfluorohexane exposure neither impaired cell viability nor induced cellular activation. TNFα enhanced ICAM-1 expression, which was not attenuated by simultaneous perfluorohexane treatment. Concentration of intracellular surfactant protein A tended to be higher in perfluorohexane treated cells compared to controls. Our in vitro data add further evidence that intraperitoneal perfluorocarbon application is feasible without adverse local effects.

Pulmonary toxicity of chronic exposure to tobacco and biomass smoke in rats

OBJECTIVE

The objective of this study was to examine the separate and combined effects of tobacco and biomass smoke exposure on pulmonary histopathology in rats.

INTRODUCTION

In addition to smoking, indoor pollution in developing countries contributes to the development of respiratory diseases.

METHODS

Twenty-eight adult rats were divided into four groups as follows: control group (Group I, no exposure to tobacco or biomass smoke), exposed to tobacco smoke (Group II), exposed to biomass smoke (Group III), and combined exposure to tobacco and biomass smoke (Group IV). After six months the rats in all four groups were sacrificed. Lung tissue samples were examined under light microscopy. The severity of pathological changes was scored.

RESULTS

Group II differed from Group I in all histopathological alterations except intraparenchymal vascular thrombosis. There was no statistically significant difference in histopathological changes between the subjects exposed exclusively to tobacco smoke (Group II) and those with combined exposure to tobacco and biomass smoke (Group IV). The histopathological changes observed in Group IV were found to be more severe than those in subjects exposed exclusively to biomass smoke (Group III).

DISCUSSION

Chronic exposure to tobacco and biomass smoke caused an increase in severity and types of lung injury.

CONCLUSION

Exposure to cigarette smoke caused serious damage to the respiratory system, particularly with concomitant exposure to biomass smoke.

Pretreatment with perfluorohexane vapor attenuates fMLP-induced lung injury in isolated perfused rabbit lungs

The authors investigated the protective effects and dose dependency of perfluorohexane (PFH) vapor on leukocyte-mediated lung injury in isolated, perfused, and ventilated rabbit lungs. Lungs received either 18 vol.% (n = 7), 9 vol.% (n = 7), or 4.5 vol.% (n = 7) PFH. Fifteen minutes after beginning of PFH application, lung injury was induced with formyl-Met-Leu-Phe (fMLP). Control lungs (n = 7) received fMLP only. In addition 5 lungs (PFH-sham) remained uninjured receiving 18 vol.% PFH only. Pulmonary artery pressure (mPAP), peak inspiratory pressure (P(max)), and lung weight were monitored for 90 minutes. Perfusate samples were taken at regular intervals for analysis and representative lungs were fixed for histological analysis. In the control, fMLP application led to a significant increase of mPAP, P(max), lung weight, and lipid mediators. Pretreatment with PFH attenuated the rise in these parameters. This was accompanied by preservation of the structural integrity of the alveolar architecture and air-blood barrier. In uninjured lungs, mPAP, P(max), lung weight, and lipid mediator formation remained uneffected in the presence of PFH. The authors concluded that pretreatment with PFH vapor leads to an attenuation of leukocyte-mediated lung injury. Vaporization of perfluorocarbons (PFCs) offers new therapeutic options, making use of their protective and anti-inflammatory properties in prophylaxis or in early treatment of acute lung injury.

Acute pathophysiological effects of intratracheal instillation of budesonide and exogenous surfactant in a neonatal surfactant-depleted piglet model

BACKGROUND

Chronic lung disease continues to be a major complication in premature infants with severe respiratory distress syndrome (RDS). This is despite having advanced ventilatory care, prenatal corticosteroids, and postnatal surfactant therapies. The combined use of intratracheal corticosteroids and surfactant may not only recruit the lungs, but also alleviate pulmonary inflammation in severe RDS.

METHODS

Fifteen newborn piglets received repeated pulmonary saline lavage to induce surfactant-depleted lungs, mimicking neonatal RDS. They were randomly divided into three groups: control group receiving no treatment; surfactant (Surf) group, treated with standard intratracheally instilled surfactant (100 mg/kg); and Budesonide plus surfactant (Bude + Surf) group, treated with intratracheally administered mixed suspension of budesonide (0.5 mg/kg) and surfactant (100 mg/kg). Blood samples were taken every 30 minutes for 4 hours. Lung tissue was examined after the experiment.

RESULTS

Significantly better oxygenation with higher PaO(2) and alveolar-arterial oxygen difference was noted in the Surf and Bude + Surf groups, compared with the control group (p < 0.05), but there were no significant differences between the Surf and Bude + Surf groups. Pulmonary histologic damage was also markedly alleviated in both the Surf and Bude + Surf groups, compared with the control group, and lung injury scores were significantly decreased in the Surf and Bude + Surf groups, compared with the control group (p < 0.05).

CONCLUSIONS

Intratracheal instillation of surfactant or surfactant plus budesonide can improve oxygenation and pulmonary histologic outcome in neonatal surfactant-depleted lungs. The additional use of budesonide does not disturb the function of the exogenous surfactant. Intratracheal administration of a corticosteroid combined with surfactant may be an effective method for alleviating local pulmonary inflammation in severe RDS.

Effects of perfluorocarbons on surfactant exocytosis and membrane properties in isolated alveolar type II cells

Background

Perfluorocarbons (PFC) are used to improve gas exchange in diseased lungs. PFC have been shown to affect various cell types. Thus, effects on alveolar type II (ATII) cells and surfactant metabolism can be expected, data, however, are controversial.

Objective

The study was performed to test two hypotheses: (I) the effects of PFC on surfactant exocytosis depend on their respective vapor pressures; (II) different pathways of surfactant exocytosis are affected differently by PFC.

Methods

Isolated ATII cells were exposed to two PFC with different vapor pressures and spontaneous surfactant exocytosis was measured. Furthermore, surfactant exocytosis was stimulated by either ATP, PMA or Ionomycin. The effects of PFC on cell morphology, cellular viability, endocytosis, membrane permeability and fluidity were determined.

Results

The spontaneous exocytosis was reduced by PFC, however, the ATP and PMA stimulated exocytosis was slightly increased by PFC with high vapor pressure. In contrast, Ionomycin-induced exocytosis was decreased by PFC with low vapor pressure. Cellular uptake of FM 1-43 - a marker of membrane integrity - was increased. However, membrane fluidity, endocytosis and viability were not affected by PFC incubation.

Conclusions

We conclude that PFC effects can be explained by modest, unspecific interactions with the plasma membrane rather than by specific interactions with intracellular targets.

Effective lavage volume of diluted surfactant improves the outcome of meconium aspiration syndrome in newborn piglets

Meconium aspiration syndrome (MAS) is one of the top causes of severe respiratory failure in neonates. This study was designed to investigate the effective volume of therapeutic bronchoalveolar lavage (BAL) with diluted surfactant in the treatment of MAS in newborn piglets. Human meconium was instilled in 24 piglets to induce MAS, and the piglets were randomly divided into four groups: 1) control, no lavage; 2) lavage-10, BAL with diluted surfactant (5 mg/mL, Survanta) 10 mL/kg in two aliquots; 3) lavage-20, 20 mL/kg in two aliquots; 4) lavage-30, 30 mL/kg in two aliquots. Cardiopulmonary parameters were monitored, and the lung tissue was histologically examined after experiments. The changes in oxygenation and lung compliance of lavage-20 and lavage-30 groups were significantly better than control and lavage-10 groups (p < 0.05), but there was no significant difference between lavage-20 and lavage-30 groups. The lung injury scores were significantly lower in the dependent site of lavage-20 and lavage-30 groups than the other two groups. In conclusion, using 20 mL/kg diluted surfactant in two aliquots to perform therapeutic BAL was as effective as 30 mL/kg in improving the pathophysiological outcomes in MAS and may warrant consideration clinically in treating MAS.

Optimal expiratory volume profile in tidal liquid ventilation under steady state conditions, based on a symmetrical lung model

Liquid-assisted ventilation (LAV) using perfluorochemicals (PFC) offers clear theoretical advantages over gas ventilation. During tidal liquid ventilation (TLV) the residual capacity of the lungs is filled with PFC and a liquid ventilator is necessary to inhale and exhale the tidal volume of PFC. However, during the expiration phase, a flow limitation (choked flow) can be observed, which compromises minute ventilation and consequently the gas exchange. The hypothesis of the presented works is that the choked flow can be avoided by profiling the expiratory volume. To validate this concept, an elastic symmetrical lung numerical model, used to characterize forced expiration in gas ventilation, was transposed to TLV. The parameters of the developed numerical model were fitted from experimental data obtained on a newborn lamb. The results obtained demonstrate that general observations made with gas ventilation still hold, however, in TLV: flow limitation in the central airways is the result of a coupling between viscous pressure losses and airway compliance, and the flow limiting segment is located in the central airways. Using the model results, an optimal theoretical expiratory profile seems to be exponential as first approximation, and its time constant is dependent on the chocked flow mechanism and not on the product of resistance by compliance. This optimal profile is used to compute the maximal minute ventilation allowable with an acceptable risk of collapse. Also, the sensitivity of minute ventilation to different parameter variations were analyzed and practical recommendations are proposed.

Leukocyte antibacterial functions are not impaired by perfluorocarbon exposure in vitro

Application of liquid, aerosolized, and vaporized perfluorocarbons (PFC) in acute lung injury has shown anti-inflammatory effects. Although this may be beneficial in states of pulmonary hyperinflammation, it also could increase susceptibility to nosocomial lung infection. We hypothesized that PFC impair cellular host defense and therefore investigated in an in vitro model the influence of perfluorohexane (PFH) on crucial mechanisms of bacterial elimination in human neutrophils and monocytes. Using scanning and transmission electron microscopy, we could show membrane-bound and ingested PFH particles that morphologically did not alter adherence and phagocytosis of Escherichia coli or leukocyte viability. The amount of adherent and phagocytosed bacteria as determined by flow cytometry was not influenced in cells only pretreated with PFH for 1 and 4 h. When PFH was present during E. coli challenge, bacterial adherence was decreased in polymorphonuclear neutrophils, but respective intracellular uptake was not impaired and was even significantly promoted in monocytes. Overall, E. coli-induced respiratory burst capacity was not reduced by PFH. Our findings provide evidence that key functions of innate host defense are not compromised by PFH treatment in vitro.

Intratracheal perfluorocarbons diminish LPS-induced increase in systemic TNF-alpha

Perfluorocarbons (PFC) reduce the production of various inflammatory cytokines, including TNF-alpha. The anti-inflammatory effect is not entirely understood. If anti-inflammatory properties are caused by a mechanical barrier, PFC in the alveoli should have no effect on the inflammatory response to intravenous LPS administration. To test that hypothesis, rats (n=31) were administered LPS intravenously and were either spontaneously breathing (Spont), conventionally ventilated (CMV), or receiving partial liquid ventilation (PLV). Serum concentration of TNF-alpha was measured. The pulmonary expressions of TNF-alpha and TNF-alpha receptor 1 protein and of TNF-alpha and ICAM-1 mRNA were determined. LPS caused a significant (P<0.001) increase in serum TNF-alpha. Serum TNF-alpha concentration was similar in LPS/Spont (525+/-180 pg/ml) and LPS/CMV (504+/-154 pg/ml) but was significantly (P<0.001) lower in animals of the LPS/PLV group (274+/-101 pg/ml). Immunohistochemical data on TNF-alpha protein expression showed a LPS-induced increase in TNF-alpha and TNF-alpha receptor 1 expression that was diminished by partial liquid ventilation. PCR measurements revealed a lower expression of TNF-alpha and ICAM-1 mRNA in LPS/PLV than in LPS/CMV or LPS/Spont animals. Semiquantitative histological evaluation revealed only minor alveolar inflammation with no significant differences between the groups. Low serum TNF-alpha concentration in PFC-treated animals is most likely explained by a decreased production of TNF-alpha in the lung.

Perfluorochemical (PFC) liquid enhances recombinant adenovirus vector-mediated viral interleukin-10 (AdvIL-10) expression in rodent lung

Adenovirus and cationic liposome mediated transfer of Interleukin-10 (IL-10), a potent anti-inflammatory cytokine, has been shown to decrease pro-inflammatory cytokine levels and overall lung inflammation in models of lung transplantation and injury. Limitations to current approaches of IL-10 gene therapy include poor vector delivery methods and pro-inflammatory properties of human IL-10 under certain conditions. We hypothesize that using perfluorochemical (PFC) liquid to deliver the highly homologous viral IL-10 (vIL-10), which is predominantly anti-inflammatory with minimal pro-inflammatory activities, can potentially be a more effective strategy to combat inflammatory lung diseases. In this study, we compare the use of PFC liquid versus aerosolized method to deliver adenovirus encoding the vIL-10 gene (AdvIL-10) in C57Bl6 mice. Detectable vIL-10 levels were measured from bronchoalveolar lavage fluid and lung homogenates at one, four, ten and thirty days after AdvIL-10. Furthermore, we determined if use of PFC liquid could allow for the use of a lower dose of AdvIL-10 by comparing the levels of detectable vIL-10 at different doses of AdvIL-10 delivered +/- PFC liquid. Results showed that PFC liquid enhanced detectable vIL-10 by up to ten fold and that PFC liquid allowed the use of ten-fold less vector. PFC liquid increased detectable vIL-10 in lung homogenates at all time points; however, the increase in detectable vIL-10 in BAL fluid peaked at four days and was no longer evident by thirty days after intratracheal instillation. In summary, this is the first report utilizing PFC liquid to enhance the delivery of a potentially therapeutic molecule, vIL-10. We believe this strategy can be used to perform future studies on the use of the predominantly anti-inflammatory vIL-10 to treat inflammatory lung diseases.

Antenatal vitamin A decreases ventilation-induced lung injury in the lamb model of congenital diaphragmatic hernia

OBJECTIVE

Infants with congenital diaphragmatic hernia (CDH) are susceptible to ventilation-induced lung injury. Vitamin A may protect the lung from injury during ventilation. The authors investigated the effects of antenatal vitamin A on ventilation-induced lung injury in CDH lambs using lung myeloperoxidase (MPO) activity as an indicator of lung injury.

METHODS

Left-sided diaphragmatic defects were created in 10 lambs at 79-81 days' gestation. Six CDH lambs had right jugular venous catheters inserted at 120 days' gestation and were given vitamin A until 135 days' gestation. Four CDH lambs were not treated. Twin littermates (n = 3) served as controls. All lambs were delivered at 136-139 days of gestation and ventilated for 2 hours. Lambs were sacrificed following ventilation and samples of left lung were snap frozen. MPO was extracted from lung tissue and MPO activity was assayed.

RESULTS

CDH lambs treated with antenatal vitamin A demonstrated significantly lower MPO activity than untreated CDH lambs (0.0477 +/- 0.0150 vs. 0.1106 +/- 0.0230 units/mg protein, p < 0.05).

CONCLUSION

This is the first study to look at the effect of vitamin A on lung injury in CDH. In the lamb model of CDH, antenatal vitamin A decreases ventilation-induced lung injury.

A Prototype of Volume-Controlled Tidal Liquid Ventilator Using Independent Piston Pumps

Liquid ventilation using perfluorochemicals (PFC) offers clear theoretical advantages over gas ventilation, such as decreased lung damage, recruitment of collapsed lung regions, and lavage of inflammatory debris. We present a total liquid ventilator designed to ventilate patients with completely filled lungs with a tidal volume of PFC liquid. The two independent piston pumps are volume controlled and pressure limited. Measurable pumping errors are corrected by a programmed supervisor module, which modifies the inserted or withdrawn volume. Pump independence also allows easy functional residual capacity modifications during ventilation. The bubble gas exchanger is divided into two sections such that the PFC exiting the lungs is not in contact with the PFC entering the lungs. The heating system is incorporated into the metallic base of the gas exchanger, and a heat-sink-type condenser is placed on top of the exchanger to retrieve PFC vapors. The prototype was tested on 5 healthy term newborn lambs (<5 days old). The results demonstrate the efficiency and safety of the prototype in maintaining adequate gas exchange, normal acido-basis equilibrium, and cardiovascular stability during a short, 2-hour total liquid ventilator. Airway pressure, lung volume, and ventilation scheme were maintained in the targeted range.

Combining lung-protective strategies in experimental acute lung injury: The impact of high-frequency partial liquid ventilation

OBJECTIVE

To evaluate the independent and combined effects of high-frequency oscillatory ventilation (HFOV) and partial liquid ventilation (PLV) on gas exchange, pulmonary histopathology, inflammation, and oxidative tissue damage in an animal model of acute lung injury.

DESIGN

Prospective, randomized animal study.

SETTING

Research laboratory of a health sciences university.

SUBJECTS

Fifty New Zealand White rabbits.

INTERVENTIONS

Juvenile rabbits injured by lipopolysaccharide infusion and saline lung lavage were assigned to conventional ventilation (CMV), PLV, HFOV, or high-frequency partial liquid ventilation (HF-PLV) with a full or half dose (HF-PLV1/2) of perfluorochemical (PFC). Uninjured ventilated animals served as controls. Arterial blood gases were obtained every 30 mins during the 4-hr study. Histopathologic evaluation was performed using a lung injury scoring system. Oxidative lung injury was assessed by measuring malondialdehyde and 4-hydroxynonenal in lung homogenates.

MEASUREMENTS AND MAIN RESULTS

HFOV, PLV, or a combination of both methods (HF-PLV) resulted in significantly improved oxygenation, more favorable lung histopathology, reduced neutrophil infiltration, and attenuated oxidative damage compared with CMV. HF-PLV with a full PFC dose did not provide any additional benefit compared with HFOV alone. HF-PLV1/2 was associated with decreased pulmonary leukostasis compared with HF-PLV.

CONCLUSIONS

The combination of HFOV and PLV (HF-PLV) does not provide any additional benefit compared with HFOV or PLV alone in a combined model of lung injury when lung recruitment and volume optimization can be achieved. The use of a lower PFC dose (HF-PLV1/2) is associated with decreased pulmonary leukostasis compared with HF-PLV and deserves further study.

Partial Liquid Ventilation in Adult Patients with Acute Respiratory Distress Syndrome

RATIONALE

Despite recent clinical trials demonstrating improved outcome in acute respiratory distress syndrome (ARDS), mortality remains high. Partial liquid ventilation (PLV) using perfluorocarbons has been shown to improve oxygenation and decrease lung injury in various animal models.

OBJECTIVE

To determine if PLV would have an impact on outcome in patients with ARDS.

METHODS

Patients with ARDS were randomized to (1) conventional mechanical ventilation (CMV; n=107), (2) "low-dose" perfluorocarbon (10 ml/kg; n=99), and (3) "high-dose" perfluorocarbon (20 ml/kg; n=105). Patients in all three groups were ventilated using volume ventilation, Vt <or= 10 ml/kg predicted body weight, rate <or= 25/min, inspiratory-to-expiratory ratio <or= 1:1, Fi(O(2)) >or= 0.5, and positive end-expiratory pressure >or= 13 cm H(2)O.

RESULTS

The 28-d mortality in the CMV group was 15%, versus 26.3% in the low-dose (p=0.06) and 19.1% in the high-dose (p=0.39) PLV groups. There were more ventilator-free days in the CMV group (13.0+/-9.3) compared with both the low-dose (7.4+/-8.5; p<0.001) and high-dose (9.9+/-9.1; p=0.043) groups. There were more pneumothoraces, hypoxic episodes, and hypotensive episodes in the PLV patients.

CONCLUSIONS

PLV at both high and low doses did not improve outcome in ARDS compared with CMV and cannot be recommended for patients with ARDS.

Effect of low-bias flow oscillation with partial liquid ventilation on fluoroscopic image analysis, gas exchange, and lung injury

OBJECTIVE

To evaluate the effect of low-bias flow oscillation (LBFO) with partial liquid ventilation (PLV) on perfluorochemical evaporation, histopathology, and oxidative tissue damage in an animal model of acute lung injury.

DESIGN

Prospective, randomized animal study.

SETTING

Research laboratory of a health sciences university.

SUBJECTS

Twelve New Zealand White rabbits.

INTERVENTIONS

Juvenile rabbits were anesthetized, paralyzed, and ventilated through a tracheostomy with either high-frequency oscillatory ventilation or LBFO. Lung injury was induced by repeated saline lavage, after which perflubron was instilled through a side port of the endotracheal tube. Lateral fluoroscopic images were performed at baseline and at various postfill intervals of animals in the high-frequency oscillatory ventilation-PLV and LBFO-PLV groups. The images were digitalized for computer analysis of the Lung Lucency Index, a surrogate marker of perflubron evaporation. Histopathologic evaluation was performed using a lung-injury scoring system. Malondialdehyde was measured in lung homogenates to assess oxidative damage.

MEASUREMENTS AND MAIN RESULTS

There were no significant differences in gas exchange and ventilator settings between groups throughout the experiment. At 300 mins, the high-frequency oscillatory ventilation-PLV group had a significantly higher Lung Lucency Index compared with the LBFO-PLV group in both dependent and nondependent lung regions (a high Lung Lucency Index correlates with increased perflubron loss). Malondialdehyde measurements were not different between groups. Animals treated with LBFO-PLV had a lower histopathologic lung-injury score compared with high-frequency oscillatory ventilation-PLV.

CONCLUSION

LBFO-PLV is a viable mode of ventilation in a model of acute lung injury and is associated with significant preservation of perflubron in comparison with high-frequency oscillatory ventilation-PLV. The lower evaporative losses during LBFO-PLV were associated with improved histology scores.

Pulmonary applications of perfluorochemical liquids: ventilation and beyond

In this review of liquid ventilation, concepts and applications are presented that summarise the pulmonary applications of perfluorochemical liquids. Beginning with the question of whether this alternative form of respiratory support is needed and ending with lessons learned from clinical trials, the various methods of liquid assisted ventilation are compared and contrasted, evidence for mechanoprotective and cytoprotective attributes of intrapulmonary perfluorochemical liquid are presented and alternative intrapulmonary applications, including their use as vehicles for drugs, for thermal control and as imaging agents are presented.

Differential impact of perfluorochemical physical properties on the physiologic, histologic, and inflammatory profile in acute lung injury

OBJECTIVE

To evaluate the differential effects of physical properties of combinational perfluorochemical liquids (PFC) during partial liquid ventilation (PLV) on inflammatory indexes in the injured lung.

DESIGN

: Interventional laboratory study.

SETTING

Academic medical research laboratory.

SUBJECTS

Seventeen saline lavage-injured juvenile rabbits.

INTERVENTIONS

Rabbits were anesthetized, ventilated, saline lavage-injured, and randomized into groups: group 1 (conventional mechanical ventilation alone-no PFC), group 2 (PLV: lowest viscosity, highest vapor pressure), group 3 (PLV: mid-viscosity, mid-vapor pressure), group 4 (PLV: highest viscosity, lowest vapor pressure).

MEASUREMENTS AND MAIN RESULTS

Arterial blood chemistry and pulmonary mechanics were monitored throughout the protocol. Following 4 hrs, lung tissue was harvested for interleukin-8, myeloperoxidase, and histologic analyses. Oxygenation (Pao2), ventilation (ventilation efficiency index), and respiratory compliance were not significantly different between groups before or following injury. Pao2 increased significantly following treatment in groups 3 and 4. Oxygenation index was significantly lower and respiratory compliance and ventilation efficiency index were significantly higher for group 4 following 4 hrs than all other groups. Total lung tissue interleukin-8 was significantly lower in groups 3 and 4 than groups 1 and 2, and lung myeloperoxidase was significantly lower in all PLV-treated groups than CMV alone. Histologic examination showed increased recruitment of the dependent lung in groups 3 and 4, with significantly greater lung expansion index, than groups 1 and 2.

CONCLUSIONS

PLV, with a single dose of higher viscosity and lower vapor pressure PFC, resulted in significantly improved gas exchange and lung mechanics with significant reduction in lung inflammation compared with conventional mechanical ventilation alone and PLV with lower viscosity and higher vapor pressure liquid. Since PFC evaporative loss and redistribution are minimized by lower VP and higher viscosity, these data suggest that greater mechanoprotection and cytoprotection of the lung are conferred during PLV with PFC liquids that remain distributed throughout the entire lung for a longer duration.

Hyperoxia-induced changes in human airway epithelial cells: the protective effect of perflubron

OBJECTIVE

To determine the protective effect of perflubron (PFB), a type of perfluorochemical liquid, in hyperoxia-induced cellular injury in the human airway epithelial cells.

DESIGN

A controlled, in vitro laboratory study.

SETTING

Tertiary-care children's hospital.

SUBJECTS

Human airway epithelial cells.

INTERVENTIONS

Human airway epithelial cells, Calu-3 cells, grown on polycarbonate porous filters at an air-liquid interface culture were exposed to normoxic (Fico(2) = 5%, balance air) or hyperoxic (Fio(2) = 95%, balance CO(2)) conditions. Hyperoxia-induced cellular changes were monitored by measuring transepithelial resistance (TER) of monolayers, histology of cells, total protein, and interleukin-8 (IL-8) secretion in apical surface fluid (ASF) washings. Under hyperoxic conditions, the protective effect of PFB was assessed by directly adding PFB liquid to the apical surface of monolayers.

MEASUREMENTS AND MAIN RESULTS

During hyperoxic gas-liquid interface culture, Calu-3 monolayers exhibited a loss of cellular integrity morphologically, decreased protein concentration, and IL-8 level in ASF washings. During hyperoxic PFB-liquid interface culture, there was an overall increase in TER value of monolayers, improved histology, decreased total protein secretion in ASF washings, and unaltered IL-8 secretion. Cytomorphologic observations of PFB-treated Calu-3 cells indicated the presence of varying numbers of differently sized intracellular vacuoles during both normoxic and hyperoxic conditions.

CONCLUSIONS

We conclude that the air-liquid interface culture of Calu-3 may be helpful in understanding mechanisms of lung injuries caused in clinical practice, and PFB protects against hyperoxia-induced airway epithelial cell injury by promoting cellular integrity as well as cytologic modifications. PFB-liquid interface culture of Calu-3 may be a useful in vitro model for studying the cytoprotective role of liquid ventilation.

A comparison of biologically variable ventilation to recruitment manoeuvres in a porcine model of acute lung injury

Background

Biologically variable ventilation (return of physiological variability in rate and tidal volume using a computer-controller) was compared to control mode ventilation with and without a recruitment manoeuvre – 40 cm H₂O for 40 sec performed hourly; in a porcine oleic acid acute lung injury model.

Methods

We compared gas exchange, respiratory mechanics, and measured bronchoalveolar fluid for inflammatory cytokines, cell counts and surfactant function. Lung injury was scored by light microscopy. Pigs received mechanical ventilation (F_IO₂ = 0.3; PEEP 5 cm H₂O) in control mode until PaO₂ decreased to 60 mm Hg with oleic acid infusion (PaO₂/F_IO₂ <200 mm Hg). Additional PEEP to 10 cm H₂O was added after injury. Animals were randomized to one of the 3 modes of ventilation and followed for 5 hr after injury.

Results

PaO₂ and respiratory system compliance was significantly greater with biologically variable ventilation compared to the other 2 groups. Mean and mean peak airway pressures were also lower. There were no differences in cell counts in bronchoalveolar fluid by flow cytometry, or interleukin-8 and -10 levels between groups. Lung injury scoring revealed no difference between groups in the regions examined. No differences in surfactant function were seen between groups by capillary surfactometry.

Conclusions

In this porcine model of acute lung injury, various indices to measure injury or inflammation did not differ between the 3 approaches to ventilation. However, when using a low tidal volume strategy with moderate levels of PEEP, sustained improvements in arterial oxygen tension and respiratory system compliance were only seen with BVV when compared to CMV or CMV with a recruitment manoeuvre.

Hydrochloric acid-induced lung injury: effects of early partial liquid ventilation on survival rate, gas exchange, and pulmonary neutrophil accumulation

OBJECTIVE

Partial liquid ventilation can improve respiratory functions in acid-induced lung injury. We studied the effects of the interval between induction of injury and initiation of partial liquid ventilation on survival, gas exchange, and pulmonary neutrophil accumulation.

MATERIAL AND METHODS

Anesthetized rats were randomly assigned to one of five groups ( n = 6 per group). Group 1 served as the control group, in the other groups an extended lung injury was induced by intratracheal instillation of hydrochloric acid. Whereas lungs of group 2 were gas-ventilated, group 3 received an early partial liquid ventilation (5 min after acid instillation) and group 4 a delayed partial liquid ventilation (30 min after acid instillation, 5 ml/kg perfluorocarbon). Group 5 received an additional continuous perfluorocarbon application of 5 ml x kg(-1) x h(-1) (30 min after acid instillation). Blood gases were measured with an intravascular blood gas sensor.

RESULTS

Acid instillation resulted in a marked decrease in PO(2)-values within 30 min (from 481+/-37 mmHg to 128+/-71 mmHg, FiO(2) 1.0). Survival rate of the study period (12 h) was higher with early partial liquid ventilation. We observed no differences between groups in peak PO(2)-values during treatment. Histopathological examination, however, showed less pulmonary neutrophil accumulation in lungs of the early partial liquid ventilation group when compared to the delayed partial liquid ventilation group.

CONCLUSIONS

Our results suggest that early partial liquid ventilation increases survival after extended acid-induced lung injury. While effects on arterial oxygenation appear not to predict acute survival we observed less intrapulmonary neutrophil accumulation with early partial liquid ventilation.

Effects of partial liquid ventilation on lipopolysaccharide-induced inflammatory responses in rats

To determine whether partial liquid ventilation (PLV) modified lung inflammatory response, we analyzed blood cytokine levels and cytokine mRNA expression in the lungs, using a rat model of endotoxemia. Thirty-six rats were allocated into one of four groups. The first group received conventional gas ventilation (CV group), the second group received 10 ml/kg perflubron intratracheally in combination with mechanical gas ventilation (PLV group), the third group received 20 mg/kg Escherichia coli lipopolyssacharide (LPS) intravenously in combination with mechanical gas ventilation (LPS group), and the fourth group received PLV and LPS (PLV + LPS group). Blood levels of TNF-alpha, IL-1beta, IL-6, IL-10, INF-gamma and IL-1 receptor antagonist were significantly increased in LPS and PLV + LPS groups. mRNA expression of pro- and anti-inflammatory cytokines in the lung tissue was also significantly increased in these groups. mRNA expression of IL-6 in PLV + LPS group was significantly increased in comparison with LPS group. Other cytokine mRNA expression including IL-10 and IL-1beta was also potentiated in PLV + LPS group, however this was not significant. Our results suggest that PLV does not protect the lungs against inflammation in systemic endotoxemia in rats.

Perfluorocarbon attenuates response of concanavalin A-stimulated mononuclear blood cells without altering ligand-receptor interaction

Intrapulmonary application of perfluorocarbons (PFC) in acute lung injury is associated with anti-inflammatory effects. A direct impact on leukocytic function may be involved. To further elucidate PFC effects on cellular activation, we compared in an in vitro model the response of concanavalin A (ConA)-stimulated lymphocytes and monocytes exposed to perfluorohexane. We hypothesized that perfluorohexane attenuates the action of the lectin ConA by altering stimulant-receptor interaction on the cell surface. Mononuclear blood cells were stimulated by incubation with ConA in the presence of different amounts of perfluorohexane. The response of lymphocytes and monocytes was determined by means of IL-2 secretion and tissue factor (TF) expression, respectively. The influence of perfluorohexane on cell-surface binding of fluorescence-labeled ConA was studied using flow cytofluorometry and fluorescence microscopy. Perfluorohexane itself did not induce a cellular activation but significantly inhibited both monocytic TF expression and, to a far greater extent, IL-2 secretion of ConA-stimulated mononuclear blood cells. The effect of perfluorohexane was due neither to an alteration of cell viability nor to a binding of the stimulant. The amount of cell surface-bound ConA was not altered by perfluorohexane, and the overall pattern of ConA receptor rearrangement did not differ between controls and treated cells. In the present study, we provide further evidence for an anti-inflammatory effect of PFC that might be beneficial in states of pulmonary hyperinflammation. A PFC-induced alteration of stimulant-receptor interaction on the surface membrane does not seem to be the cause of attenuated cell activation.

Comparison of aerosol therapy with different perfluorocarbons in surfactant-depleted animals

OBJECTIVE

The study investigates the effectiveness of aerosol treatment on gas exchange and pulmonary inflammatory reaction using perfluorocarbons with different molecular structure and vapor pressure.

DESIGN

Experimental, prospective, randomized, controlled study.

SETTING

Experimental laboratory at a university hospital.

SUBJECTS

Twenty anesthetized neonatal piglets assigned to four groups.

INTERVENTIONS

After establishment of lung injury by bronchoalveolar lavage, piglets either received aerosolized FC77 (n = 5), perfluorooctylbromide (n = 5), or FC43 (n = 5, 10 mL x kg(-1) x hr(-1) for 2 hrs) or intermittent mandatory ventilation (control, n = 5). Thereafter, animals were supported for another 6 hrs.

MEASUREMENTS AND MAIN RESULTS

Pao2 significantly improved in the perfluorocarbon groups compared with control (p < .01). Final Pao2 (mean +/- SEM) was FC77, 406 +/- 27 mm Hg; perfluorooctylbromide, 332 +/- 32 mm Hg; FC43, 406 +/- 19 mm Hg; control, 68 +/- 8 mm Hg. Paco2 and mean pulmonary arterial pressure were lower in all perfluorocarbon groups compared with control. The ratio of terminal dynamic compliance to total compliance was significantly higher in the FC77 than in the FC43, perfluorooctylbromide, and control groups. Relative gene expression of interleukin-1beta, interleukin-8, P-selectin, E-selectin, and intercellular adhesion molecule-1 in lung tissue was determined by TaqMan real time polymerase chain reaction normalized to hypoxanthineguanine-phosphoribosyl-transferase and was shown to be reduced by all perfluorocarbons.

CONCLUSIONS

Aerosol treatment with all the perfluorocarbons investigated improved gas exchange and reduced pulmonary inflammatory reaction independently from molecular structure and vapor pressure of the perfluorocarbons. Although differences in vapor pressure and molecular structure may account for varying optimal dosing strategies, several different perfluorocarbons were shown to be principally suitable for aerosol treatment.

Efficacy of partial liquid ventilation in improving acute lung injury induced by intratracheal acidified infant formula: determination of optimal dose and positive end-expiratory pressure level

OBJECTIVES

Partial liquid ventilation with fluorocarbon was successfully used for acute lung injury induced by oleic acid or lung lavage. Positive end-expiratory pressure (PEEP) during partial liquid ventilation enhances the efficacy of fluorocarbon. The aim of the current study was to assess whether partial liquid ventilation can repair lung damage induced by intratracheal acidified infant formula and to determine the optimal fluorocarbon dose and PEEP level.

DESIGN

Prospective, randomized animal study.

SETTING

University research laboratory.

SETTING AND SUBJECTS

Seventy-six male anesthetized rabbits.

INTERVENTIONS

For study 1, acute lung injury was induced by intratracheal acidified infant formula in four groups. Next, three groups received 10, 15, or 20 mL/kg fluorocarbon, and the fourth group was conventionally gas ventilated. For study 2, acute lung injury was induced in five groups. One group was gas ventilated at a PEEP of 5 cm H2O, whereas the other four groups received fluorocarbon (15 mL/kg) and were assigned to one of four PEEP levels (5, 7.5, 10, or 12.5 cm H2O). The lungs were ventilated with 100% oxygen for 4 hrs after acute lung injury.

MEASUREMENTS AND MAIN RESULTS

In study 1, fluorocarbon at doses of 15 and 20 mL/kg attenuated lung leukosequestration and edema and superoxide production of neutrophils, resulting in similar improvements in oxygenation, lung mechanics, and pathologic changes. The highest fluorocarbon dose caused mortality from pneumothorax. In study 2, the combination of PEEP with partial liquid ventilation improved gas exchange, lung compliance, pulmonary edema, and histologically observed damage. The beneficial effects of PEEP at 10 and 12.5 cm H2O were similar. Adverse side effects of 12.5 cm H2O PEEP included pneumothorax and hemodynamic instability.

CONCLUSIONS

The combination of fluorocarbon and PEEP improved the physiologic, biochemical, and histologic lung injury induced by acidified infant formula. The beneficial effects of partial liquid ventilation are due, in part, to inhibition of pulmonary neutrophil accumulation and activation with fluorocarbon. The optimal fluorocarbon dose and PEEP level in our model were 15 mL/kg and 10 cm H2O, respectively.

High frequency oscillatory ventilation suppresses inflammatory response in lung tissue and microdissected alveolar macrophages in surfactant depleted piglets

The impact of high frequency oscillatory ventilation (HFOV) compared with intermittent mandatory ventilation (IMV) on oxygenation and pulmonary inflammatory response was studied in a surfactant depleted piglet model. After establishment of lung injury by bronchoalveolar lavage, piglets either received HFOV (n =5) or IMV (control; n = 5) for eight hours. PaO(2) was higher and mean pulmonary arterial pressure (MPAP) was lower with HFOV (HFOV versus control, mean +/- SEM; endpoint PaO(2): 252 +/- 73 versus 68 +/- 8.4 mm Hg; p < 0.001; MPAP: 22 +/- 2.3 versus 34 +/- 2.5 mm Hg; p < 0.01). mRNA expression of interleukin (IL)-1 beta, IL-6, IL-8, IL-10, TGF-beta 1, Endothelin-1, and adhesion molecules (E-selectin, P-selectin, ICAM-1) in lung tissue was quantified by real time PCR normalized to beta-actin and hypoxanthine-guanine-phosphoribosyl-transferase (HPRT). mRNA expression of all cytokines and adhesion molecules/HPRT was higher in controls (e.g.: HFOV versus control, mean +/- SEM; IL-1 beta/HPRT: 1.6 +/- 0.3 versus 23.1 +/- 8.6 relative units (RU), p < 0.001; IL-8/HPRT: 8.5 +/- 2.0 versus 63.5 +/- 15.2 RU, p < 0.001). IL-8/HPRT gene expression was quantified in microdissected single cells. With HFOV, IL-8 gene expression was highly reduced in alveolar macrophages: 10 +/- 3.4 copies IL-8 mRNA/copy HPRT mRNA versus 356 +/- 142; p < 0.05 (bronchiolar epithelial cells: 33 +/- 16 versus 208 +/- 108; alveolar septum: 2.1 +/- 1.3 versus 26 +/- 11; bronchiolar smooth muscle cells: 1.3 +/- 0.3 versus 2.8 +/- 1.0; vascular smooth muscle cells: 0.7 +/- 0.3 versus 1.1 +/- 0.4). In conclusion, HFOV improved oxygenation, reduced pulmonary arterial pressure and attenuated pulmonary inflammatory response.

Inhibition of inflammatory responses by ambroxol, a mucolytic agent, in a murine model of acute lung injury induced by lipopolysaccharide

OBJECTIVE

The aim of this study is to investigate whether ambroxol inhibits inflammatory responses in a murine model of lipopolysaccharide-induced acute lung injury (ALI).

METHODS

Mice (n=295) were first intratracheally instilled with lipopolysaccharide (LPS) to induce ALI and then received an intraperitoneal (i.p.) injection of either normal saline (NS), ambroxol (30 or 90 mg/kg per day) or dexamethasone (2.5 or 5 mg/kg per day) for 7 days. Metabolism (n=10, each), lung morphology (n=5, each) and wet-to-dry lung weight ratio (n=10, each) were studied. The levels of tumor necrosis factor (TNF-alpha), interleukin-6 (IL-6) and transforming growth factor (TGF-beta1) and the protein concentration (n=5 or 7, each) in bronchoalveolar lavage (BAL) were measured.

RESULTS

Mice with LPS-induced ALI that were treated with ambroxol at a dosage of 90 mg/kg per day significantly gained weight compared to the control and dexamethasone-treated groups. Ambroxol and dexamethasone significantly reduced the lung hemorrhage, edema, exudation, neutrophil infiltration and total lung injury histology score at 24 and 48 h. In addition, ambroxol and dexamethasone significantly attenuated the lung wet-to-dry weight ratio at 24 and 48 h (p<0.05). Compared to the control group, TNF-alpha, IL-6 and TGF-beta1 levels in the BAL in both ambroxol- and dexamethasone-treated groups were significantly reduced at 24 and 48 h. The protein in BAL, an index of vascular permeability, was also significantly decreased in the ambroxol- and dexamethasone-treated groups (p<0.05).

CONCLUSION

Ambroxol inhibited proinflammatory cytokines, reduced lung inflammation and accelerated recovery from LPS-induced ALI.

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.

Influence of partial liquid ventilation on bacterial growth and alveolar expansion in newborn rabbits with group B-streptococcal pneumonia

Partial liquid ventilation (PLV) with perfluorocarbons has been considered as an alternative therapy for severe inflammatory lung disease. The present study was performed to test whether PLV influences bacterial growth and lung histology in a rabbit model of congenital pneumonia caused by group B streptococci. Near-term newborn rabbits were tracheotomized, inoculated via the airways with group B streptococci, and subsequently ventilated for 5 h with either PLV or conventional ventilation. At 30 min after group B streptococci administration, animals in the PLV group (n = 16) received 30 mL/kg body weight of perfluorocarbon (PF 5080) via the tracheal tube. Evaporative losses were substituted with 20 mL/kg perfluorocarbon at hourly intervals. Identical volumes of air were injected in control animals at the same times (n = 15). The number of colony-forming units in left lung homogenate, evaluated at the end of the experiments, tended to be lower in PLV-treated animals than in controls (6.8 x 109 versus 6.4 x 1010 colony-forming units/g body weight; p = 0.06). Comparison of these numbers with the colony-forming units injected at the beginning of the experiments revealed a reduction in bacterial number in the PLV group and proliferation in the controls (-2.2 x 108 versus +5.6 x 1010 colony-forming units/g body weight; p < 0.05). Histologic examination demonstrated less inflammation and more homogeneous lung expansion in PLV-treated animals. Two animals in the PLV group had focal interstitial emphysema. Our results suggest that PLV with PF 5080 reduces bacterial proliferation in experimental group B streptococcal pneumonia.

Perfluorocarbons attenuate oxidative lung damage

The aim of this study was to investigate the effect of tidal liquid ventilation (TLV) compared to conventional mechanical ventilation (CMV) on oxidative lung damage in the setting of acute respiratory distress syndrome (ARDS). After repeated lung lavages, 10 minipigs were treated with CMV or TLV for 4 hr before the animals were sacrificed. Samples for blood gas analysis and bronchial aspirate samples were withdrawn before the induction of lung injury, and at 10 min, 2 hr, and 4 hr after the beginning of ventilatory support. To assess lung oxidative damage, total hydroperoxide (TH) and advanced oxidation protein product (AOPP) concentrations were measured in bronchial aspirate samples. After 2 and 4 hr of ventilatory support, partial oxygen tension (PaO(2)) and base excess (BE) were significantly higher in the TLV group than in the CMV group, while PaCO(2) was slightly higher, but with no statistical significance. In the CMV group, the AOPP level was significantly higher at 4 hr than at baseline. TH and AOPP bronchial aspirate concentrations were higher in the CMV group than in the TLV group at 2 and 4 hr of ventilation. We conclude that animals treated with TLV showed lower oxidative lung damage compared to animals treated with CMV.

Extended high-frequency partial liquid ventilation in lung injury: gas exchange, injury quantification, and vapor loss

High-frequency oscillatory ventilation with perflubron (PFB) reportedly improves pulmonary mechanics and gas exchange and attenuates lung injury. We explored PFB evaporative loss kinetics, intrapulmonary PFB distribution, and dosing strategies during 15 h of high-frequency oscillation (HFO)-partial liquid ventilation (PLV). After saline lavage lung injury, 15 swine were rescued with high-frequency oscillatory ventilation (n = 5), or in addition received 10 ml/kg PFB delivered to dependent lung [n = 5, PLV-compartmented (PLV(C))] or 10 ml/kg distributed uniformly within the lung [n = 5, PLV(U)]. In the PLV(C) group, PFB vapor loss was replaced. ANOVA revealed an unsustained improvement in oxygenation index in the PLV(U) group (P = 0.04); the reduction in oxygenation index correlated with PFB losses. Although tissue myeloperoxidase activity was reduced globally by HFO-PLV (P < 0.01) and regional lung injury scores (lung injury scores) in dependent lung were improved (P = 0.05), global lung injury scores were improved by HFO-PLV (P < 0.05) only in atelectasis, edema, and alveolar distension but not in cumulative score. In our model, markers of inflammation and lung injury were attenuated by HFO-PLV, and it appears that uniform intrapulmonary PFB distribution optimized gas exchange during HFO-PLV; additionally, monitoring PFB evaporative loss appears necessary to stabilize intrapulmonary PFB volume.

Laser-assisted microdissection and real-time PCR detect anti-inflammatory effect of perfluorocarbon

The aim of this study was to identify cell types involved in the anti-inflammatory effect of ventilation with perfluorocarbon in vivo. Fifteen anesthetized, surfactant-depleted piglets received either aerosolized perfluorocarbon (Aerosol-PFC), partial liquid ventilation (rLV) at functional residual capacity (FRC) volume (FRC-PLV), or intermittent mandatory ventilation (control). After laser-assisted microdissection of different lung cell types, mRNA expression of IL-8 and ICAM-1 was determined using TaqMan real-time PCR normalized to hypoxanthine phosphoribosyltransferase (HPRT). IL-8 mRNA expression (means +/- SE; control vs. Aerosol-PFC) was 356 +/- 142 copies IL-8 mRNA/copy HPRT mRNA vs. 3.5 +/- 1.8 in alveolar macrophages (P <0.01); 208 +/- 108 vs. 2.7 +/- 0.8 in bronchiolar epithelial cells (P <0.05); 26 +/- 11 vs. 0.7 +/- 0.2 in alveolar septum cells (P <0.01); 2.8 +/- 1.0 vs. 0.8 +/- 0.4 in bronchiolar smooth muscle cells (P <0.05); and 1.1 +/- 0.4 vs. 0.2 +/- 0.05 in vascular smooth muscle cells (P <0.05). With FRC-PLV, IL-8/HPRT mRNA expression was significantly lower in macrophages, bronchiolar epithelial, and vascular smooth muscle cells. ICAM-1 mRNA expression in vascular endothelial cells remained unchanged. Predominantly, alveolar macrophages and bronchiolar epithelial cells were involved in the inflammatory pulmonary process. The anti-inflammatory effect of Aerosol-PFC was most pronounced.

Perfluorooctyl bromide (perflubron) attenuates oxidative injury to biological and nonbiological systems

OBJECTIVE

To examine whether perfluorooctyl bromide (perflubron) is capable of protecting biological and nonbiological systems against oxidative damage through a mechanism independent of its known anti-inflammatory property.

DESIGN

A controlled, in vitro laboratory study.

SETTING

Research laboratory of a health sciences university.

SUBJECTS

Rat pulmonary artery endothelial cell cultures (biological system) and linoleic acid in sodium dodecyl sulfate micelles (nonbiological system).

INTERVENTIONS

Rat pulmonary artery endothelial cells labeled with dichlorofluorescein diacetate and incubated with perflubron or culture media (control) were exposed to H2O2. H2O2-induced fluorescence of dichlorofluorescein diacetate was measured as an index of intracellular oxidative stress. In another experiment, linoleic acid in sodium dodecyl sulfate micelles was exposed to various concentrations of the azo initiator 2,2'-diazo-bis-(2-amidinopropane) dihydrochloride (2, 4, 20, and 50 mM) in the presence or absence of perflubron. Malondialdehyde measurements were obtained as a marker of oxidative damage to linoleic acid.

MEASUREMENTS AND MAIN RESULTS

Cell monolayers incubated with perflubron exhibited 66.6% attenuation in intracellular fluorescence compared with controls (p < .05). Linoleic acid in sodium dodecyl sulfate micelles incubated with perflubron and exposed to 2, 4, 20, or 50 mM of 2,2'-diazo-bis-(2-amidinopropane) dihydrochloride showed less evidence of lipid peroxidation as indicated by lower malondialdehyde measurements at 240 mins (10.6%, 16%, 41%, and 14.2%, respectively) compared with controls.

CONCLUSIONS

Perflubron attenuates oxidative damage to both biological and nonbiological systems. This newly recognized property of perflubron is independent of its anti-inflammatory properties.

Effects of exogenous surfactant supplementation and partial liquid ventilation on acute lung injury induced by wood smoke inhalation in newborn piglets

OBJECTIVE

To investigate the beneficial effects of exogenous surfactant supplementation (ESS) and partial liquid ventilation (PLV) in treating acute lung injury induced by wood smoke inhalation.

DESIGN

A prospective, randomized, controlled, multigroup study.

SETTING

An animal research laboratory at a medical center.

SUBJECTS

Newborn piglets (n = 29; 1.80 +/- 0.06 kg) of either sex.

INTERVENTIONS

Animals were ventilated with a tidal volume of 15 mL/kg, a rate of 30 breaths/min, a positive end-expiratory pressure of 5 cm H(2)O, and an Fio(2) of 1.0. After the induction of acute lung injury by wood smoke inhalation, animals were randomly assigned to receive either conventional mechanical ventilation (CMV) or PLV with or without ESS pretreatment. Animals were grouped as CMV, ESS-CMV, PLV, and ESS-PLV.

MEASUREMENTS AND MAIN RESULTS

Arterial blood gases, cardiovascular hemodynamics, dynamic lung compliance, and total lung injury scores were measured. After smoke inhalation, all four groups displayed similar high arterial carboxyhemoglobin levels, low Pao(2) (<150 mm Hg), and low dynamic lung compliance (<66% of its baseline). In the CMV group, these deleterious conditions remained during the 4-hr observation period, and severe lung injury was noted histologically. All treatment groups demonstrated a significant increase in Pao(2) compared with the CMV group. In addition, both the PLV and ESS-PLV groups displayed significant improvements in dynamic lung compliance and in their histologic outcomes. Nevertheless, none of the variables measured in the PLV group differed from those measured in the ESS-PLV group.

CONCLUSIONS

In a newborn piglet model of smoke inhalation injury, PLV or ESS improved oxygenation. PLV compared favorably with ESS in its greater improvements in lung compliance and lung pathology. However, the combined therapy of ESS and PLV was not clearly superior to PLV alone during the observation period.

Real-time visualization of partial liquid ventilation in a model of acute lung injury

BACKGROUND

To clarify the effects of partial liquid ventilation, we visualized and morphologically analyzed real-time alveolar recruitment in a model of acute lung injury.

METHODS

Male Wistar rats were divided into 3 groups: a group that underwent hydrochloric acid aspiration and mechanical gas ventilation (ALI group, n = 15), a group that underwent acid aspiration and partial liquid ventilation beginning 90 minutes after acid aspiration (PLV group, n = 15), and a group that underwent mechanical ventilation without acid aspiration (control group, n = 5). The number of ventilated alveoli and the diameter of the largest ventilated alveolus in each of 10 high-power fields observed on fluorescence micrographs with a tracer of labeled albumin were determined and averaged from 90 to 210 minutes after acid aspiration.

RESULTS

The number of alveoli in the PLV group significantly increased in comparison to that in the ALI group. The diameter of the largest alveolus in the PLV group decreased from 103.7 +/- 16.3 microm to 76.3 +/- 6.5 microm until the end of the experiment. This diameter was equivalent to that in the control group.

CONCLUSIONS

The excellent alveolar recruitment suggests that liquid ventilation ameliorates ventilator-associated lung injury.

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.

Diffuse pulmonary hemorrhage: evolutionary 'flaw' or consequence of evolutionary progress?

Diffuse alveolar hemorrhage (DAH), a serious and frequently life-threatening process, can occur in a wide variety of disorders, including mitral stenosis, systemic autoimmune diseases, conditions associated with anti-neutrophil cytoplasmic antibodies, anti-glomerular basement membrane antibody, inhaled toxins or infection, and drug allergies. These causes have no common denominator, but the end result, of capillary inflammation and hemorrhage, is the same. The capillaritis seen in DAH is present exclusively in the lung and is not part of a more generalized systemic vasculitis. In a recent article, I highlighted the central role of the neutrophils in this process, and suggested that in DAH the neutrophils present in the lung may sift the associated immune complexes and transfer them out of the vascular system into the alveoli. In this article, we document the inflammation seen during the remission period and during the acute lung bleeding of DAH in 2 patients. Because DAH is a common finding in a variety of pathological conditions, we then explore the possible evolutionary mechanisms behind DAH.