Perfluorochemical rescue after surfactant treatment: effect of perflubron dose and ventilatory frequency

Perfluorocarbons in Research and Clinical Practice: A Narrative Review

Perfluorocarbons (PFCs) are organic liquids derived from hydrocarbons in which some of the hydrogen atoms have been replaced by fluorine atoms. They are chemically and biologically inert substances with a good safety profile. They are stable at room temperature, easy to store, and immiscible in water. Perfluorocarbons have been studied in biomedical research since 1960 for their unique properties as oxygen carriers. In particular, PFCs have been used for liquid ventilation in unusual environments such as deep-sea diving and simulations of zero gravity, and more recently for drug delivery and diagnostic imaging. Additionally, when delivered as emulsions, PFCs have been used as red blood cell substitutes. This narrative review will discuss the multifaceted utilization of PFCs in therapeutics, diagnostics, and research. We will specifically emphasize the potential role of PFCs as red blood cell substitutes, as airway mechanotransducers during artificial placenta procedures, as a means to improve donor organ perfusion during the ex vivo assessment, and as an adjunct in cancer therapies because of their ability to reduce local tissue hypoxia.

Administration of Drugs/Gene Products to the Respiratory System: A Historical Perspective of the Use of Inert Liquids

The present review is a historical perspective of methodology and applications using inert liquids for respiratory support and as a vehicle to deliver biological agents to the respiratory system. As such, the background of using oxygenated inert liquids (considered a drug when used in the lungs) opposed to an oxygen-nitrogen gas mixture for respiratory support is presented. The properties of these inert liquids and the mechanisms of gas exchange and lung function alterations using this technology are described. In addition, published preclinical and clinical trial results are discussed with respect to treatment modalities for respiratory diseases. Finally, this forward-looking review provides a comprehensive overview of potential methods for administration of drugs/gene products to the respiratory system and potential biomedical applications.

PFOB sonosensitive microdroplets: determining their interaction radii with focused ultrasound using MR thermometry and a Gaussian convolution kernel computation

Purpose: Micron-sized perfluorocarbon droplet adjuvants to focused ultrasound therapies allow lower applied power, circumvent unwanted prefocal heating, and enhance thermal dose in highly perfused tissues. The heat enhancement has been shown to saturate at increasing concentrations. Experiments were performed to empirically model the saturating heating effects during focused ultrasound.Materials and methods: The measurements were made at varying concentrations using magnetic resonance thermometry and focused ultrasound by circulating droplets of mean diameter 1.9 to 2.3 µm through a perfused phantom. A simulation was performed to estimate the interaction radius size, empirically.Results: The interaction radius, representing the radius of a sphere encompassing 90% of the probability for the transformation of acoustic energy into heat deposition around a single droplet, was determined experimentally from ultrasonic absorption coefficient measurements The simulations suggest the interaction radius was approximately 12.5-fold larger than the geometrical radius of droplets, corresponding to an interaction volume on the order of 2000 larger than the geometrical volume.Conclusions: The results provide information regarding the dose-response relationship from the droplets, a measure with 15% precision of their interaction radii with focused ultrasound, and subsequent insights into the underlying physical heating mechanism.

Perfluorochemical-facilitated plasminogen activator delivery to the airways: A novel treatment for inhalational smoke-induced acute lung injury

BACKGROUND

Effective clinical management of airway clot and fibrinous cast formation of severe inhalational smoke-induced acute lung injury (ISALI) is lacking. Aerosolized delivery of tissue plasminogen activator (tPA) is confounded by airway bleeding; single-chain urokinase plasminogen activator (scuPA) moderated this adverse effect and supported transient improvement in gas exchange and lung mechanics. However, neither aerosolized plasminogen activator (PA) yielded durable improvements in physiologic responses or reduction in cast burden. Here, we hypothesized that perfluorochemical (PFC) liquids would facilitate PA distribution and sustain improvements in physiologic outcomes in ISALI.

METHODS

Spontaneously breathing adult sheep (n = 36) received anesthesia and analgesia and were instrumented, exposed to cotton smoke inhalation, and supported by mechanical ventilation for 48 h. Groups (n = 6/group) were studied without supplemental treatment, or, starting 4 h post injury, they received intratracheal low volume (8 mL) PFC liquid alone or a dose range of tPA/PFC or scuPA/PFC suspensions (4 or 8 mg in 8 mL PFC) every 8 h. Outcomes were evaluated by sequential measurements of cardiopulmonary parameters, lung histomorphology, and biochemical analyses of bronchoalveolar lavage fluid.

RESULTS

Dose-response and PA-type comparisons of outcomes demonstrated sustained superiority with low-volume PFC suspensions of scuPA over tPA or PFC alone, favoring the highest dose of scuPA/PFC suspension over lower doses, without airway bleeding.

CONCLUSIONS

We propose that this improved profile over previously reported aerosolized delivery is likely related to improved dose distribution. Sustained salutary responses to scuPA/PFC suspension delivery in this translational model are encouraging and support the possibility that the observed outcomes could be of clinical importance.

Overcoming inactivation of the lung surfactant by serum proteins: a potential role for fluorocarbons?

In many pulmonary conditions serum proteins interfere with the normal adsorption of components of the lung surfactant to the surface of the alveoli, resulting in lung surfactant inactivation, with potentially serious untoward consequences. Here, we review the strategies that have recently been designed in order to counteract the biophysical mechanisms of inactivation of the surfactant. One approach includes protein analogues or peptides that mimic the native proteins responsible for innate resistance to inactivation. Another perspective uses water-soluble additives, such as electrolytes and hydrophilic polymers that are prone to enhance adsorption of phospholipids. An alternative, more recent approach consists of using fluorocarbons, that is, highly hydrophobic inert compounds that were investigated for partial liquid ventilation, that modify interfacial properties and can act as carriers of exogenous lung surfactant. The latter approach that allows fluidisation of phospholipid monolayers while maintaining capacity to reach near-zero surface tension definitely warrants further investigation.

A comparison of conventional surfactant treatment and partial liquid ventilation on the lung volume of injured ventilated small lungs

As an alternative to surfactant therapy (ST), partial liquid ventilation (PLV) with perfluorocarbons (PFC) has been considered as a treatment for acute lung injury (ALI) in newborns. The instilled PFC is much heavier than the instilled surfactant and the aim of this study was to investigate whether PLV, compared to ST, increases the end-expiratory volume of the lung (VL). Fifteen newborn piglets (age <12 h, mean weight 678 g) underwent saline lung lavage to achieve a surfactant depletion. Thereafter animals were randomized to PLV (n = 8), receiving PFC PF5080 (3M, Germany) at 30 mL kg(-1), and ST (n = 7) receiving 120 mg Curosurf®. Blood gases, hemodynamics and static compliance were measured initially (baseline), immediately after ALI, and after 240 min mechanical ventilation with either technique. Subsequently all piglets were killed; the lungs were removed in toto and frozen in liquid N2. After freeze-drying the lungs were cut into lung cubes (LCs) with edge lengths of 0.7 cm, to calculate VL. All LCs were weighed and the density of the dried lung tissue was calculated. No statistically significant differences between treatment groups PLV and ST (means ± SD) were noted in body weight (676 ± 16 g versus 679 ± 17 g; P = 0.974) or lung dry weight (1.64 ± 0.29 g versus 1.79 ± 0.48 g; P = 0.48). Oxygenation index and ventilatory efficacy index did not differ significantly between both groups at any time. VL (34.28 ± 6.13 mL versus 26.22 ± 8.1 mL; P < 0.05) and the density of the dried lung tissue (48.07 ± 5.02 mg mL(-1) versus 69.07 ± 5.30 mg mL(-1); P < 0.001), however, differed significantly between the PLV and ST groups. A 4 h PLV treatment of injured ventilated small lungs increased VL by 30% and decreased lung density by 31% compared to ST treatment, indicating greater lung distension after PLV compared to ST.

Persurf, a new method to improve surfactant delivery: a study in surfactant depleted rats

PURPOSE

Exogenous surfactant is not very effective in adults with ARDS, since surfactant does not reach atelectatic alveoli. Perfluorocarbons (PFC) can recruit atelectatic areas but do not replace impaired endogenous surfactant. A surfactant-PFC-mixture could combine benefits of both therapies. The aim of the proof-of-principal-study was to produce a PFC-in-surfactant emulsion (Persurf) and to test in surfactant depleted Wistar rats whether Persurf achieves I.) a more homogenous pulmonary distribution and II.) a more homogenous recruitment of alveoli when compared with surfactant or PFC alone.

METHODS

Three different PFC were mixed with surfactant and phospholipid concentration in the emulsion was measured. After surfactant depletion, animals either received 30 ml/kg of PF5080, 100 mg/kg of stained (green dye) Curosurf™ or 30 ml/kg of Persurf. Lungs were fixated after 1 hour of ventilation and alveolar aeration and surfactant distribution was estimated by a stereological approach.

RESULTS

Persurf contained 3 mg/ml phospholipids and was stable for more than 48 hours. Persurf-administration improved oxygenation. Histological evaluation revealed a more homogenous surfactant distribution and alveolar inflation when compared with surfactant treated animals.

CONCLUSIONS

In surfactant depleted rats administration of PFC-in-surfactant emulsion leads to a more homogenous distribution and aeration of the lung than surfactant alone.

Efficacy of intratracheal instillation of a meropenem/perfluorochemical suspension in acute lung injury

Perfluorochemical (PFC) is theoretically a good vehicle for delivering biological agents to the lungs. This study was designed to investigate the efficacy of intratracheal (IT) instillation of meropenem using PFC liquid as a vehicle in a piglet model of acute lung injury (ALI). Eighteen piglets were injured with lung lavages to induce ALI, and randomly assigned to intravenous (IV) infusion or IT instillation groups, the latter using either PFC or normal saline (NS) as a delivery vehicle for meropenem. Blood samples were obtained at 0, 15, 30, and 60 min, and then hourly for 6 hr. Sera and extracts of lung tissues were assayed for meropenem content using high-performance liquid chromatography. We found that the IV group had significantly higher serum concentrations of meropenem during the first hour after dosing (P < 0.05). There was no significant difference between IT-PFC and IT-NS groups regarding changes in serum meropenem concentrations during the experimental period. Meropenem content in lung tissue was highest in the IT-PFC group, lower in the IT-NS group, and undetectable in the IV group (P < 0.05). The IT-NS group had the highest peak inspiratory pressure (P < 0.05), but there were no significant differences in other cardiopulmonary parameters among the three groups studied. In conclusion, meropenem can be safely administered to injured lungs by IT instillation in a meropenem/PFC suspension. Using PFC liquid as an IT vehicle to carry meropenem provides better pulmonary drug depositions than IV injection or IT instillation with NS in ALI.

Perfluorochemical liquid-adenovirus suspensions enhance gene delivery to the distal lung

WE COMPARED LUNG DELIVERY METHODS OF RECOMBINANT ADENOVIRUS (RAD): (1) rAd suspended in saline, (2) rAd suspended in saline followed by a pulse-chase of a perfluorochemical (PFC) liquid mixture, and (3) a PFC-rAd suspension. Cell uptake, distribution, and temporal expression of rAd were examined using A549 cells, a murine model using luciferase bioluminescence, and histological analyses. Relative to saline, a 4X increase in transduction efficiency was observed in A549 cells exposed to PFC-rAd for 2-4 h. rAd transgene expression was improved in alveolar epithelial cells, and the level and distribution of luciferase expression when delivered in PFC-rAd suspensions consistently peaked at 24 h. These results demonstrate that PFC-rAd suspensions improve distribution and enhance rAd-mediated gene expression which has important implications in improving lung function by gene therapy.

Protection against sepsis-induced lung injury by selective inhibition of protein kinase C-δ (δ-PKC)

Inflammation and proinflammatory mediators are activators of δ-PKC. In vitro, δ-PKC regulates proinflammatory signaling in neutrophils and endothelial and epithelial cells, cells that can contribute to lung tissue damage associated with inflammation. In this study, a specific δ-PKC TAT peptide inhibitor was used to test the hypothesis that inhibition of δ-PKC would attenuate lung injury in an animal model of ARDS. Experimental ARDS was induced in rats via 2CLP, a model of polymicrobial sepsis. Following 2CLP surgery, the δ-PKC TAT inhibitory peptide (2CLP+δ-PKC TAT in PBS) or PBS (2CLP+PBS) was administered intratracheally. Controls consisted of SO, where animals underwent a laparotomy without 2CLP. Twenty-four hours after SO or 2CLP, blood, BALF, and lung tissue were collected. 2CLP induced δ-PKC phosphorylation in the lung within 24 h. Treatment with the δ-PKC TAT inhibitory peptide significantly decreased pulmonary δ-PKC phosphorylation, indicating effective inhibition of δ-PKC activation. Plasma and BALF levels of the chemokines CINC-1 and MIP-2 were elevated in 2CLP + PBS rats as compared with SO rats. Treatment with δ-PKC TAT reduced 2CLP-induced elevations in chemokine levels in BALF and plasma, suggesting that δ-PKC modulated chemokine expression. Most importantly, intratracheal administration of δ-PKC TAT peptide significantly attenuated inflammatory cell infiltration, disruption of lung architecture, and pulmonary edema associated with 2CLP. Thus, δ-PKC is an important regulator of proinflammatory events in the lung. Targeted inhibition of δ-PKC exerted a lung-protective effect 24 h after 2CLP.

Potential Use of Fluorocarbons in Lung Surfactant Therapy

Exogenous surfactant therapy based on animal lung extract preparations has been developed successfully for the treatment of neonatal respiratory distress syndrome. However, because of the inherent limitations of these natural preparations, the development of new synthetic surfactants is a major objective. We report here that a perfluorocarbon gas (perfluorooctyl bromide, gPFOB) inhibits the formation of the semi-crystalline domains that occur during compression of a Langmuir monolayer of dipalmitoyl phosphatidylcholine (DPPC), taken as a simplified model of lung surfactant. gPFOB also facilitates the re-spreading of the DPPC monolayer. These results suggest that PFOB, a fluorocarbon already investigated for oxygen delivery, may be useful in lung surfactant replacement compositions.

Alterations of alveolar type II cells and intraalveolar surfactant after bronchoalveolar lavage and perfluorocarbon ventilation. An electron microscopical and stereological study in the rat lung

Background

Repeated bronchoalveolar lavage (BAL) has been used in animals to induce surfactant depletion and to study therapeutical interventions of subsequent respiratory insufficiency. Intratracheal administration of surface active agents such as perfluorocarbons (PFC) can prevent the alveolar collapse in surfactant depleted lungs. However, it is not known how BAL or subsequent PFC administration affect the intracellular and intraalveolar surfactant pool.

Methods

Male wistar rats were surfactant depleted by BAL and treated for 1 hour by conventional mechanical ventilation (Lavaged-Gas, n = 5) or partial liquid ventilation with PF 5080 (Lavaged-PF5080, n = 5). For control, 10 healthy animals with gas (Healthy-Gas, n = 5) or PF5080 filled lungs (Healthy-PF5080, n = 5) were studied. A design-based stereological approach was used for quantification of lung parenchyma and the intracellular and intraalveolar surfactant pool at the light and electron microscopic level.

Results

Compared to Healthy-lungs, Lavaged-animals had more type II cells with lamellar bodies in the process of secretion and freshly secreted lamellar body-like surfactant forms in the alveoli. The fraction of alveolar epithelial surface area covered with surfactant and total intraalveolar surfactant content were significantly smaller in Lavaged-animals. Compared with Gas-filled lungs, both PF5080-groups had a significantly higher total lung volume, but no other differences.

Conclusion

After BAL-induced alveolar surfactant depletion the amount of intracellularly stored surfactant is about half as high as in healthy animals. In lavaged animals short time liquid ventilation with PF5080 did not alter intra- or extracellular surfactant content or subtype composition.

Effects of recombinant Clara cell secretory protein (rhCC10) on inflammatory-related matrix metalloproteinase activity in a preterm lamb model of neonatal respiratory distress

OBJECTIVE

To test the hypothesis that recombinant Clara cell secretory protein (rhCC10) instillation would foster improved lung function, acute structural preservation, and attenuation of matrix metalloproteinase (MMP) activity in a surfactant-deficient, mechanically ventilated lung.

DESIGN

Interventional laboratory study.

SETTING

An academic medical research facility in the northeastern United States.

SUBJECTS

Sedated, ventilated premature lambs.

INTERVENTIONS

Preterm lambs (n = 18; 126 +/- 3 days gestation) were instrumented, ventilated, and treated with 100 mg/kg exogenous surfactant. Lambs were randomized to receive 0, 0.5, or 5.0 mg/kg rhCC10 (n = 6 per group) and were ventilated for 4 hrs.

MEASUREMENTS AND MAIN RESULTS

Posttreatment, lung function and cardiopulmonary stability were monitored for the ventilation period and then animals were killed for in vitro surfactant function analysis, lung histomorphometry, and analysis of MMP-2, -7, and -9 as well as their tissue inhibitors (TIMP)-1 and -2. Ventilation efficiency and pulmonary compliance were improved in the 5.0-mg/kg rhCC10 group by 4 hrs. Lung expansion was variable in the apical regions only. MMP-2 quantity was greater in the apical than the base lung regions of rhCC10-treated groups, and rhCC10 decreased MMP-7 in the base of the lung.

CONCLUSIONS

These data suggest that improved lung function in the surfactant-treated preterm lamb following intratracheal rhCC10 may be related to the reduction of proteolytic activity of MMP-7.

Effects of perfluorochemical evaporative properties on oxygenation during partial liquid ventilation

BACKGROUND

The physical-chemical properties of perfluorochemical (PFC) liquids have been shown to influence physiological and cellular responses during partial liquid ventilation (PLV). The aim of this study is to compare the relationship between patho-physiological endpoints and the physical properties of three PFC liquids used in treating acute lung injury.

METHODS

A total of 18 juvenile rabbits were randomized into conventional mechanical ventilation or PLV groups after lung saline lavages. Three PFC liquids, including Flutec perfluoro-1,3,5-trimethylcyclohexane (PP4; vapor pressure, 28.8 mmHg at 37 degrees C), Perfluorodecalin (PFD; vapor pressure, 13.6 mmHg at 37 degrees C), and Perflubron (PFB; vapor pressure, 10.4 mmHg at 37 degrees C) were used for PLV with no replacement for 4 h. A thermal detector was used to measure PFC loss rate. Physiological measurements and evaporative loss rate of PFC were done every 30 min, and lung histology was examined.

RESULTS

The mean evaporative loss rate was significantly higher in the PP4 group (4.75 +/- 0.24 mL/kg per h) than in either the PFD (1.43 +/- 0.11 mL/kg per h) or the PFB (1.18 +/- 0.05 mL/kg per h) group (P < 0.05). The oxygenation of PFD and PFB was maintained good for 4 h, however, the PP4 group showed a fast deterioration since 2 h post-treatment due to fast dropping of the residual PP4 amount in lungs. Histology showed good alveolar integrity in the PFD and PFB groups.

CONCLUSIONS

The effects of PLV are directly influenced by the evaporative property of the PFC liquid. With no replacement over 4 h, PLV effects could be maintained with utilizing a PFC liquid with low, rather than high, vapor pressure. PFC with high vapor pressure has a high loss rate and low residual volume that causes poor maintenance on oxygenation during PLV. Therefore, measuring PFC loss rate is important in future studies and clinical application of PLV.

Perfluorochemical liquids enhance delivery of superoxide dismutase to the lungs of juvenile rabbits

Previous studies suggest acute lung injury (ALI) in premature newborns is associated with relative deficiency of antioxidant enzymes that may be ameliorated by recombinant human superoxide dismutase (rhSOD). Perfluorochemicals (PFCs) are distributed homogeneously and support gas exchange in diseased lungs. We investigated whether PFCs could provide an effective delivery system for rhSOD. Juvenile rabbits were lung-lavaged, treated with surfactant, and randomized: group I: fluorescently labeled rhSOD (5 mg/kg in 2 mL/kg saline); group II: fluorescently labeled rhSOD (5 mg/kg in 18 mL/kg PFC). Animals were ventilated with oxygen for 4 h; the lungs were harvested for analysis of SOD distribution and oxidative injury. Cardiopulmonary indices remained stable and similar between groups. Qualitative assessment (QA) showed a more homogeneous lung SOD distribution in group II and a better histologic profile. QA of lung SOD distribution showed significant increase in SOD concentrations in group II (7.37 +/- 1.54 microg/mg protein) compared with group I (1.65 +/- 0.23 microg/mg protein). Oxidative injury as assessed by normalized protein carbonyl was 149.1 +/- 26.8% SEM in group II compared with 200.5 +/- 7.3% SEM in group I. Plasma SOD was significantly higher in group II. Administration of rhSOD with or without PFCs does not compromise cardiovascular function or impede lung recovery after ALI. PFCs enhance rhSOD delivery to the lungs by 400% while decreasing lung oxidative damage by 25% compared with rhSOD alone. These data suggest that PFCs optimize lung rhSOD delivery and might enhance the beneficial effects of rhSOD in preventing acute and chronic lung injury.

Fluidization of a dipalmitoyl phosphatidylcholine monolayer by fluorocarbon gases: potential use in lung surfactant therapy

Fluorocarbon gases (gFCs) were found to inhibit the liquid-expanded (LE)/liquid-condensed (LC) phase transition of dipalmitoyl phosphatidylcholine (DPPC) Langmuir monolayers. The formation of domains of an LC phase, which typically occurs in the LE/LC coexistence region upon compression of DPPC, is prevented when the atmosphere above the DPPC monolayer is saturated with a gFC. When contacted with gFC, the DPPC monolayer remains in the LE phase for surface pressures lower than 38 mN m(-1), as assessed by compression isotherms and fluorescence microscopy (FM). Moreover, gFCs can induce the dissolution of preexisting LC phase domains and facilitate the respreading of the DPPC molecules on the water surface, as shown by FM and grazing incidence x-ray diffraction. gFCs have thus a highly effective fluidizing effect on the DPPC monolayer. This gFC-induced fluidizing effect was compared with the fluidizing effect brought about by a mixture of unsaturated lipids and proteins, namely the two commercially available lung surfactant substitutes, Curosurf and Survanta, which are derived from porcine and bovine lung extracts, respectively. The candidate FCs were chosen among those already investigated for biomedical applications, and in particular for intravascular oxygen transport, i.e., perfluorooctyl bromide, perfluorooctylethane, bis(perfluorobutyl)ethene, perfluorodecalin, and perfluorooctane. The fluidizing effect is most effective with the linear FCs. This study suggests that FCs, whose biocompatibility is well documented, may be useful in lung surfactant substitute compositions.

Recombinant human Clara cell secretory protein in acute lung injury of the rabbit: effect of route of administration

OBJECTIVE

To test the hypothesis that intratracheal instillation of Clara cell secretory protein (CC 10) to the lung may afford greater protection than intravenous administration from ventilator-induced lung inflammation.

DESIGN

Interventional laboratory study.

SETTING

An academic medical research facility in northeastern United States.

SUBJECTS

Sedated, lavage-injured juvenile rabbits.

INTERVENTIONS

A total of 18 juvenile rabbits were anesthetized, ventilated, injured with saline lavage (Pao2 of <100 mm Hg; respiratory compliance of <0.50 mL.cm H2O.kg and <50% baseline), and randomized to receive intratracheally administered surfactant plus no recombinant human CC 10 (rhCC 10, control), intravenous rhCC 10, or intratracheal rhCC 10.

MEASUREMENT AND MAIN RESULTS

Arterial blood chemistry and pulmonary mechanics were monitored; plasma and urine were collected serially. After 4 hrs of ventilation, lungs were lavaged and harvested. Surfactant function was analyzed from bronchoalveolar lavage samples (surfactometry); rhCC 10, interleukin-8, and lung myeloperoxidase concentrations were measured. Pao2, oxygenation index, ventilatory efficiency index, and respiratory compliance were not different across time or group beyond injury. Surfactometry data identified no differences as a function of group or time. Plasma, bronchoalveolar lavage, and lung interleukin-8 concentrations, lung myeloperoxidase concentrations, and inflammatory cell counts in the alveolar and interstitial spaces of intravenous and intratracheal groups were lower than in the control group (p < .05) but not statistically different from each other. Concentrations of rhCC 10 in lung, bronchoalveolar lavage, and plasma were greater in the intratracheal group than in the intravenous group (p<.05). Urine rhCC 10 concentrations were greater for the intravenous group than for the intratracheal group (p<.05) at 1, 3, and 4 hrs after treatment. No group differences in histomorphometry were noted.

CONCLUSIONS

Both intravenous and intratracheal rhCC 10 delivery, after surfactant therapy, effectively decrease lung inflammation vs. surfactant alone. While supporting the physiologic profile, intratracheal instillation results in greater, maintained lung and plasma rhCC 10 pools compared with intravenous administration. As such, intratracheal instillation of rhCC 10 may afford more prolonged protection against lung inflammation than intravenous administration.

Effects of an intratracheally delivered anti-inflammatory protein (rhCC10) on physiological and lung structural indices in a juvenile model of acute lung injury

BACKGROUND

Mechanical ventilation results in acute lung trauma that can stimulate processes that alter lung development. Activation of matrix metalloproteinases (MMPs) and their tissue-produced inhibitors (TIMPs) is initiated by the inflammatory response to mechanical ventilation and are involved in breakdown of the basement membrane and parenchymal modeling.

OBJECTIVES

The aim of this study was to test the hypothesis that rhCC10, a lung anti-inflammatory mediator, would foster improved lung function, structural preservation, and a reduction in net MMP activity in a juvenile model of acute lung injury.

METHODS

Twenty-four juvenile rabbits were saline-lavage-injured and treated with 100 or 25 mg/kg surfactant (Survanta, Ross Labs) with or without rhCC10 (Claragen, Inc.; n=6 per group). Animals were ventilated for 4 h, then euthanized for in vitro surfactant function analysis, lung histomorphometry, and analysis of MMP-2, MMP-7, and MMP-9 and TIMPs 1 and 2 in the lung.

RESULTS

Apical lung expansion, reduced with the lower dose of surfactant, was partially restored with the addition of rhCC10. Alveolar septal wall thickness was reduced (p<0.05) with low-dose surfactant plus rhCC10 compared to high-dose surfactant alone. Increased within-group variance in MMP-2 and MMP-9 proteolytic activity was found with the low-dose surfactant and was abolished with rhCC10. MMP-7 was reduced (p<0.05) with rhCC10 administration, independent of surfactant dose.

CONCLUSIONS

Intratracheal administration of the anti-inflammatory rhCC10 resulted in preserved lung structure and MMP/TIMP profile after 4 h of mechanical ventilation, in a surfactant dose-dependent manner.

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.

The Efficacy of Fluorocarbon, Surfactant, and Their Combination for Improving Acute Lung Injury Induced by Intratracheal Acidified Infant Formula

We conducted the current study to compare the efficacy of partial liquid ventilation (PLV), pulmonary surfactant (PSF), and their combination in ameliorating the acidified infant-formula-induced acute lung injury (ALI). In the Part I study, 42 rabbits receiving volume-controlled ventilation with positive end-expiratory pressure 10 cm H(2)O were randomly divided into 6 groups (groups noninjuryI, gas ventilation [GVi], PLVi, PSFi, PLVi-->PSFi, and PSFi-->PLVi). ALI was induced by intratracheal acidified infant formula (2 mL/kg, pH 1.8). Group GVi received neither PLV nor PSF therapy. Groups PLV and PSF received intratracheal fluorocarbon 15 mL/kg or surfactant 100 mg/kg, respectively, 30 min after acidified infant formula. Groups PLVi-->PSFi and PSFi-->PLVi received both treatments at 30-min intervals. In Part II, 42 rabbits (in 6 groups) undergoing pressure-controlled ventilation received the same drug therapies as in Part I. The lungs were excised to assess biochemical and histological damage 150 min after induction of ALI. In Parts I and II, PSF, fluorocarbon, and their combination attenuated lung leukosequestration and edema and superoxide production of neutrophils, consequently improving oxygenation, lung mechanics, and pathological changes. Independent of ventilation mode, PSF followed by fluorocarbon provided the most beneficial effects and fluorocarbon followed by PSF produced the least efficacy.

Dose response to aerosolized perflubron in a neonatal swine model of lung injury

Aerosolized perfluorocarbon (PFC) improves gas exchange, lung mechanics, and pulmonary artery pressure. The objective of this intervention was to study the dose-response effect to aerosolized perfluorooctylbromide (PFOB; perflubron, LiquiVent, Alliance Pharmaceutical Corp.) in surfactant-depleted piglets. After induction of lung injury by saline lavage, 25 newborn piglets were randomly assigned to receive 0, 1.25, 2.5, 5.0, or 7.5 mL/kg aerosolized PFOB per hour. A 2-h therapy period was followed by a 3-h observation period. In all animals, respiratory support was performed with intermittent mandatory ventilation. After aerosol treatment and 3 h of observation, arterial oxygen pressure was similarly improved in the 2.5-, 5.0-, and 7.5-mL. kg(-1). h(-1) aerosol-PFOB groups and higher compared with the 1.25-mL. kg(-1). h(-1) aerosol-PFOB (P < 0.01) and the control groups (P < 0.001). Compared with the control group, arterial carbon dioxide pressure was significantly reduced with 2.5-, 5.0-, and 7.5-mL. kg(-1). h(-1) aerosol-PFOB (P < 0.001). Treatment with 1.25 mL. kg(-1). h(-1) aerosol-PFOB did not significantly affect arterial carbon dioxide pressure. The 20% terminal dynamic compliance/dynamic compliance was significantly improved in the groups that received 2.5, 5.0, and 7.5 mL. kg(-1). h(-1) aerosol-PFOB compared with control animals. Mean pulmonary artery pressure was lower after therapy with 5.0 and 7.5 mL. kg(-1). h(-1) aerosol-PFOB (P < 0.01) than in the control group. IL-1beta gene expression in lung tissue was significantly reduced with PFOB 1.25 mL. kg(-1). h(-1). In summary, aerosolized PFOB improved terminal dynamic compliance, pulmonary gas exchange, and pulmonary artery pressure in a dose-dependent manner. In terms of oxygenation and lung mechanics, the optimum dose was between 2.5 and 5 mL. kg(-1). h(-1).

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.

Continuous tracheal gas insufflation during partial liquid ventilation in juvenile rabbits with acute lung injury

To examine the hypothesis that combined treatment with tracheal gas insufflation (TGI) and partial liquid ventilation (PLV) may improve pulmonary outcome relative to either treatment alone in acute lung injury (ALI), saline lavage lung injury was induced in 24 anesthetized, ventilated juvenile rabbits that were then randomly assigned to receive ( n = 6/group) 1) conventional mechanical ventilation (CMV) alone, 2) continuous TGI at 0.5 l/min, 3) PLV with perfluorochemical liquid, and 4) combined TGI and PLV (TGI + PLV), and subsequently ventilated with minimized pressures and tidal volume (Vt) to keep arterial Po2 (PaO2) >100 Torr and arterial Pco2 (PaCO2) at 45-60 Torr for 4 h. Gas exchange, lung mechanics, myeloperoxidase, IL-8, and histomorphometry [including expansion index (EI)] were assessed. The CMV group showed no improvement in lung mechanics and gas exchange; all treated groups had significant increases in compliance, PaO2, ventilation efficacy index (VEI), and EI, and decreases in PaCO2, oxygenation index, physiological dead space-to-Vt ratio (Vd/Vt), myeloperoxidase, and IL-8, relative to the CMV group. TGI resulted in lower peak inspiratory pressure, Vt, Vd/Vt, and greater VEI vs. PLV group; PLV resulted in greater compliance, PaO2, and EI vs. TGI. TGI + PLV resulted in decreased peak inspiratory pressure, Vt, Vd/Vt, and increased VEI compared with TGI, improved compliance and EI compared with PLV, and a further increase in PaO2 and oxygenation index and a decrease in PaCO2 vs. either treatment alone. These results indicate that combined treatment of TGI and PLV results in improved pulmonary outcome than either treatment alone in this animal model of 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.

Measurement of changes in respiratory mechanics during partial liquid ventilation using jet pulses

OBJECTIVE

To compare the changes in respiratory mechanics within the breathing cycle in healthy lungs between gas ventilation and partial liquid ventilation using a special forced-oscillation technique.

DESIGN

Prospective animal trial.

SETTINGS

Animal laboratory in a university setting.

SUBJECTS

A total of 12 newborn piglets (age, <12 hrs; mean weight, 725 g).

INTERVENTIONS

After intubation and instrumentation, lung mechanics of the anesthetized piglets were measured by forced-oscillation technique at the end of inspiration and the end of expiration. The measurements were performed during gas ventilation and 80 mins after instillation of 30 mL/kg perfluorocarbon PF 5080.

MEASUREMENTS AND MAIN RESULTS

Brief flow pulses (width, 10 msec; peak flow, 16 L/min) were generated by a jet generator to measure the end-inspiratory and the end-expiratory respiratory input impedance in the frequency range of 4-32 Hz. The mechanical variables resistance, inertance, and compliance were determined by model fitting, using the method of least squares. At least in the lower frequency range, respiratory mechanics could be described adequately by an RIC single-compartment model in all piglets. During gas ventilation, the respiratory variables resistance and inertance did not differ significantly between end-inspiratory and end-expiratory measurements (mean [sd]: 4.2 [0.7] vs. 4.1 [0.6] kPa x L(-1) x sec, 30.0 [3.2] vs. 30.7 [3.1] Pa x L(-1) x sec2, respectively), whereas compliance decreased during inspiration from 14.8 (2.0) to 10.2 (2.4) mL x kPa(-1) x kg(-1) due to a slight lung overdistension. During partial liquid ventilation, the end-inspiratory respiratory mechanics was not different from the end-inspiratory respiratory mechanics measured during gas ventilation. However, in contrast to gas ventilation during partial liquid ventilation, compliance rose from 8.2 (1.0) to 13.0 (3.0) mL x kPa(-1) x kg(-1) during inspiration. During expiration, when perfluorocarbon came into the upper airways, both resistance and inertance increased considerably (mean with 95% confidence interval) by 34.3% (23.1%-45.8%) and 104.1% (96.0%-112.1%), respectively.

CONCLUSIONS

The changes in the respiratory mechanics within the breathing cycle are considerably higher during partial liquid ventilation compared with gas ventilation. This dependence of lung mechanics from the pulmonary gas volume hampers the comparability of dynamic measurements during partial liquid ventilation, and the magnitude of these changes cannot be detected by conventional respiratory-mechanical analysis using time-averaged variables.

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.

Perfluorochemical (PFC) combinations for acute lung injury: an in vitro and in vivo study in juvenile rabbits

Perfluorochemical (PFC) fluids of different physical properties were titrated and tested in vitro for physical properties that are appropriate for respiratory application. Two PFC liquids were studied: perfluoromethylcyclohexane (PP2), a liquid with high vapor pressure and low viscosity, and perfluoromethyldecalin (PP9), a fluid with low vapor pressure and high viscosity. Eighteen rabbits (2.05 +/- 0.07 kg; mean +/- SEM) were lung-lavaged and randomized: group I, control group; group II, partial liquid ventilation with 75% PP2 and 25% PP9; group III, partial liquid ventilation with 50% PP2 and 50% PP9; and group IV, partial liquid ventilation with 25% PP2 and 75% PP9. Ventilator volumes were kept constant during the 4-h experiment. Cardiopulmonary measurements were performed every 30 min. The lung histology was examined. The in vitro study showed PFC [viscosity/vapor pressure (in cS and mm Hg, respectively)] as follows: 100% PP2 (0.88/141); 100% PP9 (3.32/2.9); 75% PP2 and 25% PP9 (1.26/107); 50% PP2 and 50% PP9 (1.63/13.7); and 25% PP2 and 75% PP9 (2.21/4.4). The in vivo experiments found that combinations of moderate vapor pressure (groups 3 and 4) demonstrated good gas exchange, compliance, and histologic findings. Thus, combinations of PFC liquids can be formulated to modulate the physiologic outcome in acutely injured lungs, and may prove useful for alternative PFC liquid applications.

Managing our first breaths: a reflection on the past several decades of neonatal pulmonary therapy

Lung disease has been a leading cause of significant morbidity and mortality since neonates first drew breath. Over the past few decades, many treatment options have evolved to aid us in our ability to support neonatal breathing. The history of neonatal pulmonary care, both its successes and controversies, can teach us a great deal about the future of this dynamic field. As new developments occur, we constantly modify the therapies we offer to preterm and term infants. Understanding traditional therapeutic options and knowing what may be on the horizon can help caregivers to better match treatment plans with individual infants. This article reviews advances in mechanical ventilation, adjuvant therapies, and respiratory drugs through the past few decades and speculates on future directions in this field.

Liquid ventilation: Gas exchange, perfluorochemical uptake, and biodistribution in an acute lung injury

OBJECTIVE: Compare the physiologic, histologic, and biochemical findings of tidal and partial liquid ventilation (PLV) with gas ventilated lambs with an acute lung injury. DESIGN: Experimental, prospective randomized controlled study. SETTING: School of medicine, department of physiology. SUBJECTS: Eighteen newborn lambs (</=1 wk old). INTERVENTIONS: Injury was established by using HCl saline lavages. Seven lambs underwent tidal liquid ventilation (TLV), five underwent PLV, and six underwent gas ventilation (GV) for 4 hrs. Measurements: Sequential arterial blood chemistries were performed. Ventilation efficiency index, arterial-alveolar Po(2), and physiologic shunt were calculated. Blood and tissue were analyzed for perfluorochemical fluid. Histologic examinations of lungs were performed. MAIN RESULTS: TLV oxygenation was significantly better (p <.001) than PLV and GV. Paco(2) was similar in all three groups. Ventilation efficiency index was significantly better (p <.01) in the TLV group as compared with the PLV and GV groups. Physiologic shunt was significantly less in the TLV injury group (p <.01) than the PLV and GV groups. Perfluorochemical fluid blood level of 2.3 +/- 0.32 &mgr;g/mL in the PLV group was significantly lower (p <.01) than TLV of 7.8 +/- 0.71 &mgr;g/mL; there was a difference (p <.01) as function of time in the TLV and no difference in the PLV injury group. There were no differences in tissue perfluorochemical fluid levels as a function of ventilation ([mean +/- sem] TLV, 219 +/- 26 &mgr;g/g; PLV injury, 184 +/- 26 &mgr;g/g). There was a significant difference in perfluorochemical fluid levels as a function of tissue (p <.001). CONCLUSION: In severe lung injury, this study demonstrates that physiologic gas exchange can be maintained with TLV or PLV. Physiologic shunt was less in the TLV group as compared with PLV or GV. Additionally, perfluorochemical fluid in the blood and tissue is low during PLV and TLV relative to that associated with intravenous administration of perfluorochemical fluid emulsion.

Partial liquid ventilation: Effect of initial dose and redosing strategy in acute lung injury

OBJECTIVE: Partial liquid ventilation (PLV) with perfluorochemicals has been shown to be effective in treating acute respiratory failure in animal studies and human trials. To determine the influences of perfluorochemicals on initial dose and redosing strategy, we studied their effects on gas exchange, pulmonary mechanics, and lung architecture. DESIGN: After lung injury was induced by repeated warm saline lavages, the animals were instilled endotracheally with different doses of perflubron during 5-10 mins in PLV-treated groups. The animals were randomized to five groups: PLV-12S (12 mL/kg perflubron, single dose), PLV-12M (12 mL/kg perflubron, multiple replacement doses), PLV-18S (18 mL/kg perflubron, single dose), PLV-18M (18 mL/kg perflubron, multiple replacement doses), and the control group (conventional mechanical ventilation only). Ventilator settings were kept constant during the 4-hr experiment. SETTING: An animal laboratory affiliated with Temple University School of Medicine. SUBJECTS: Twenty-eight New Zealand White juvenile rabbits (weight, 1.96 +/- 0.03 kg). INTERVENTIONS: Physiologic data were recorded every 30 mins. A constant volume (1.3 mL/kg/hr) of perflubron was replaced hourly in the PLV-12M and PLV-18M groups. The perflubron in the expired gas was measured with a thermal detector device. The hourly evaporative loss rate and the estimated residual perfluorochemical amount were calculated and analyzed. Histologic examinations of the lungs were performed. MEASUREMENTS AND MAIN RESULTS: All animals in the PLV-treated groups (PLV-12S, n = 4; PLV-12M, n = 5, PLV-18S, n = 5; PLV-18M, n = 4) demonstrated improvements in gas exchange and respiratory compliance that were significantly (p <.05) better than the control group (n = 8). However, the PLV-12S group demonstrated progressive deterioration after the initial improvement. The loss rate of perflubron did not differ among the PLV-treated groups (1.17 +/- 0.03 mL/kg/hr), but the residual perfluorochemical volume in the lungs decreased progressively and significantly in the PLV-12S and PLV-18S groups as a function of time (p <.05). Histologic examination showed good alveolar protection in the PLV-12M, PLV-18S, and PLV-18M groups. CONCLUSIONS: We conclude that the low initial dose (12 mL/kg, about two thirds the functional residual capacity volume of rabbits) of perflubron required hourly replacement to maintain the effects of PLV. With a high initial dose of 18 mL/kg perflubron (equal to a full functional residual capacity volume in rabbits), the responses are potentiated in both single and multiple dosing groups up to 4 hrs.

Aerosolized perfluorocarbon suppresses early pulmonary inflammatory response in a surfactant-depleted piglet model

The effect of new ventilation strategies on initial pulmonary inflammatory reaction was studied in a surfactant-depleted piglet model. Sixty minutes after induction of lung injury by bronchoalveolar lavage, piglets received either aerosolized FC77 (aerosol-PFC, 10 mL/kg/h, n = 5) or partial liquid ventilation (PLV) with FC77 at functional residual capacity volume (FRC-PLV, 30 mL/kg, n = 5), or at low volume (LV-PLV, 10 mL/kg per hour, n = 5), or intermittent mandatory ventilation (control, n = 5). After 2 h, perfluorocarbon application was stopped and intermittent mandatory ventilation continued for 6 h. After a total experimental period of 8 h, animals were killed and lung tissue obtained. mRNA expression of IL-1beta, IL-6, IL-8, and TGF-beta in porcine lung tissue was quantified using TaqMan real-time PCR and normalized to beta-actin (A) and hypoxanthine-guanine-phosphoribosyl-transferase (H). In the aerosol-PFC group, IL-1beta, IL-6, IL-8, and transforming growth factor (TGF)-beta mRNA expression in lung tissue was significantly lower than in the control group. Reduction was 95% for IL-1beta/H (p < 0.001), 73% for IL-6/H (p < 0.05), 87% for IL-8/H (p < 0.001), and 38% for TGF-beta/H (p < 0.01). A lower mRNA gene expression was also determined for IL-1beta and IL-8 when the aerosol-PFC group was compared with the LV-PLV group [91% for IL-1beta/H (p < 0.001), 75% for IL-8/H (p < 0.001)]. In the FRC-PLV group, mRNA expression of IL-1beta was significantly lower than in the control (p < 0.05) and LV-PLV (p < 0.01) group. In a surfactant-depleted piglet model, aerosol therapy with perfluorocarbon but not LV-PLV reduces the initial pulmonary inflammatory reaction at least as potently as PLV at FRC volume.

Physiologic characteristics of cold perfluorocarbon-induced hypothermia during partial liquid ventilation in normal rabbits

Because perfluorocarbon (PFC) liquid contacts closely with the alveolar capillaries during partial liquid ventilation (PLV), PLV with cold PFC may be used for the induction of hypothermia. Twenty rabbits were randomized to PFC-induced hypothermia (PH) (n = 7; core temperature 35 degrees +/- 1 degrees C), surface hypothermia (SH) (n = 7; 35 degrees +/- 1 degrees C), or normothermia (n = 6; 39 degrees +/- 1 degrees C). We induced PH by repeated in situ exchanges of 0 degrees C perfluorodecalin during PLV. At the establishment (0 min) of hypothermia in the PH group, oxygen consumption (P = 0.04) and oxygen extraction ratio (P = 0.01) decreased from normothermic condition. Metabolic (oxygen consumption, oxygen extraction ratio, serum lactate level) and hemodynamic variables (heart rate, blood pressure, cardiac output, pulmonary artery pressure) of the PH group were not different from those of the SH group at 0, 30, 60, 90, and 120 min of hypothermia. The difference in temperature between the pulmonary artery and rectum during the hypothermic period was smaller in the PH group compared with the SH group (P = 0.033). In conclusion, hypothermia may be induced during PLV by using cold PFC. This "pulmonary method" of cooling was comparable to a systemic method of cooling with regard to a few important physiologic variables, while maintaining a narrower interorgan temperature difference.

IMPLICATIONS

The induction of moderate hypothermia was feasible in rabbits by administrating cold perfluorocarbon liquid into the lung. Physiologic changes induced by this pulmonary cooling were comparable to those induced by systemic cooling. Our method may be regarded as a methodological advance in the field of therapeutic hypothermia.

Effects of partial liquid ventilation with FC-77 on acute lung injury in newborn piglets

Partial liquid ventilation (PLV) with various types of perfluorochemicals (PFC) has been shown to be beneficial in treating acute lung injury. FC-77 is a type of PFC with relatively high vapor pressure and evaporative losses during PLV. This study tested the hypothesis that using FC-77 for PLV with hourly replacement is effective in treating acute lung injury. Fifteen neonatal piglets were randomly and evenly divided into 3 study groups: 1) lavage-induced lung injury followed by conventional mechanical ventilation (Lavage-CMV); 2) lavage-induced lung injury followed by PLV using FC-77 with hourly replacement (11.2 +/- 1.5 mL/kg/hr) (Lavage-PLV); and 3) sham lavage injury followed by conventional mechanical ventilation (Control). Immediately after induction, repeated saline lavages induced acute lung injury characterized by decreases in dynamic lung compliance, arterial oxygen tension, and arterial pH, and increases in arterial CO(2) tension and oxygenation index, whereas the sham lavage procedure failed to do so. During the 3-hr period of CMV, these pulmonary and cardiovascular parameters remained stable in the Control group, but deteriorated in the Lavage-CMV group. In contrast, after acute lung injury, low lung compliance, abnormal gas exchange, acidosis, and inadequate oxygenation significantly improved in the Lavage-PLV group. Histological analysis of these 3 study groups revealed that the Lavage-CMV group had the highest lung injury score and the Control group had the lowest. These results suggest that, in comparison to CMV, PLV with FC-77 and hourly replacement of FC-77 promotes more favorable pulmonary mechanics, gas exchange, oxygenation, and lung histology in a piglet model of acute lung injury.

Pulmonary administration of perfluorodecaline- gentamicin and perfluorodecaline- vancomycin emulsions

The aim of this study was to examine pharmacokinetics and pulmonary antibiotic tissue concentrations (PATC) of gentamicin and vancomycin after intrapulmonary administration of a perfluorodecaline (PFD)-gentamicin and a PFD-vancomycin emulsion during partial liquid ventilation (PLV). PLV was initiated in 19 healthy rabbits and 18 surfactant-depleted rabbits. The animals were randomized to receive either 5 mg/kg gentamicin and 15 mg/kg vancomycin intravenously, or 5 mg/kg gentamicin intrapulmonary, or 15 mg/kg vancomycin intrapulmonary. Antibiotic plasma levels were measured after 15, 30, 45, and 60 min, and hourly thereafter. After 5 h animals were sacrificed and lungs were removed to evaluate PATC and histology. PATC were significantly higher after intrapulmonary administration of both gentamicin and vancomycin. In healthy rabbits, peak plasma concentrations were lower and 5 h plasma concentrations were higher after intrapulmonary administration, whereas plasma concentrations were not different in surfactant-depleted rabbits. There were no differences in lung histology, hemodynamics, lung mechanics, or gas exchange between the treatment groups. We conclude that during PLV, higher PATC can be achieved after intrapulmonary administration of PFD-antibiotic emulsions compared with intravenous administration of the same dose without apparent short-term adverse effects. We speculate that intrapulmonary antibiotic administration during PLV may be beneficial in treating severe pneumonia.

Small dose of exogenous surfactant combined with partial liquid ventilation in experimental acute lung injury: effects on gas exchange, haemodynamics, lung mechanics, and lung pathology

A combination of exogenous surfactant and partial liquid ventilation (PLV) with perfluorocarbons should enhance gas exchange, improve respiratory mechanics and reduce tissue damage of the lung in acute lung injury (ALI). We used a small dose of exogenous surfactant with and without PLV in an experimental model of ALI and studied the effects on gas exchange, haemodynamics, lung mechanics, and lung pathology. ALI was induced by repeated lavages (PaO2/FIO2 less than 13 kPa) in 24 anaesthesized, tracheotomized and mechanically ventilated (FIO2 1.0) juvenile pigs. They were treated randomly with either a single intratracheal dose of surfactant (50 mg kg(-1), Curosurf, Serono AG, München, Germany) (SURF-group, n=8), a single intratracheal dose of surfactant (50 mg kg(-1), Curosurf) followed by PLV with 30 ml kg(-1) of perfluorocarbon (PF 5080, 3M, Germany) (SURF-PLV-group, n=8) or no further intervention (controls, n=8). Pulmonary gas exchange, respiratory mechanics, and haemodynamics were measured hourly for a 6 h period. In the SURF-group, the intrapulmonary right-to-left shunt (QS/QT) decreased significantly from mean 51 (SEM 5)% after lavage to 12 (2)%, and PaO2 increased significantly from 8.1 (0.7) to 61.2 (4.7) kPa compared with controls and compared with the SURF-PLV-group (P<0.05). In the SURF-PLV-group, QS/QT decreased significantly from 54 (3)% after induction of ALI to 26 (3)% and PaO2 increased significantly from 7.2 (0.5) to 30.8 (5.0) kPa compared with controls (P<0.05). Static compliance of the respiratory system (C(RS)), significantly improved in the SURF-PLV-group compared with controls (P<0.05). Upon histological examination, the SURF-group revealed the lowest total injury score compared with controls and the SURF-PLV-group (P<0.05). We conclude that in this experimental model of ALI, treatment with a small dose of exogenous surfactant improves pulmonary gas exchange and reduces the lung injury more effectively than the combined treatment of a small dose of exogenous surfactant and PLV.

Perfluorochemical liquids modulate cell-mediated inflammatory responses

OBJECTIVE

To examine whether chemically different perfluorochemical liquids (PFC) (perfluorodecalin [PFD]; perflubron [PFB]) induce inflammatory responses in blood leukocytes.

SETTING

University research laboratory.

DESIGN

Whole blood from 12 healthy adults was incubated with increasing PFC concentrations and/or bacterial lipopolysaccharide.

MEASUREMENTS AND MAIN RESULTS

Adhesion molecules (CD62L, CD11b), reactive oxygen species, and cytokine responses in resting and activated leukocyte subtypes were studied. Scanning and transmission electron microscopies were performed. At the highest concentrations, PFB stimulated a significant increase in resting monocytic reactive oxygen species production; all types of blood leukocytes were unresponsive to PFD. Neither PFB nor PFD changed CD62L expression; PFB increased CD11b expression in monocytes and granulocytes. PFD induced a small though significant increase in interleukin-8 secretion. When simulating a condition in which patients with severe lung disease or sepsis would be ventilated with PFC, neither PFB nor PFD plus lipopolysaccharide stimulated tumor necrosis-alpha or interleukin-8 production above levels induced by lipopolysaccharide alone, but rather demonstrated a trend for decreased tumor necrosis factor-alpha production. Expression of CD11b and CD62L and the production of reactive oxygen species were not changed beyond the levels induced by lipopolysaccharide alone. As a morphologic correlate to the above proinflammatory changes, surface-bound blebs and intracellular vacuoles were seen by electron microscopy.

CONCLUSIONS

At PFC concentrations comparable with those in blood during liquid ventilation, PFC liquids did not induce variables associated with inflammation. In the presence of high PFC concentrations, simulating the condition in which bronchoalveolar cells are exposed to PFC, monocytes may be induced by PFB to produce reactive oxygen species, and blood leukocytes induced by PFB to express CD11b and by PFD to secrete interleukin-8; the presence of either PFC attenuated tumor necrosis factor-alpha production after lipopolysaccharide stimulation.

Effects of perfluorocarbons and perfluorocarbons/surfactant emulsions on growth and viability of group B streptococci and Escherichia coli

OBJECTIVE

Partial liquid ventilation with perfluorocarbons (PFC) might be used as a new ventilatory strategy to treat respiratory insufficiency in congenital pneumonia. The present study investigates for the first time effects of PFC on growth and viability of group B streptococci (GBS) and Escherichia coli, bacteria frequently causing congenital pneumonia.

DESIGN

Prospective, in vitro study.

SETTING

Research laboratory in a university.

MATERIAL

Group B streptococci 090 Ia HD Colindale and E. coli K12, JM 101.

INTERVENTIONS

E. coli (10(7)/mL) were grown in the absence or presence of different PFC (RM 101, PF 5080, FO 6167) for up to 6 hrs. To study bacterial viability, GBS (5 x 10(7)/mL) were incubated in saline with or without different PFC, PFC/surfactant emulsions, or surfactant (Curosurf) for up to 5 hrs. Every 2 hrs, the colony forming units were determined by plating different dilutions of bacteria on agar.

MEASUREMENTS AND MAIN RESULTS

RM 101 or PF 5080 alone and in emulsions with surfactant had no effect on viability of GBS or growth of E. coli. For FO 6167, a previously described toxicity was found, even if 1 mL of GBS suspension was incubated with only 100 microL of FO 6167, verifying the experimental design that guarantees a PFC bacteria contact. The toxic effects were almost prevented by forming a PFC-in-surfactant emulsion but not by preincubation of GBS with surfactant and subsequent FO 6167 exposure.

CONCLUSION

RM 101 and PF 5080 did not influence bacterial growth in vitro; direct effects on bacterial proliferation during partial liquid ventilation in congenital pneumonia seem, therefore, unlikely. Interestingly, we found that the known toxic effects of FO 6167 can be prevented by covering PFC with a surfactant film. Surfactant reduced the cytotoxic effects of FO 6167, probably by preventing a direct contact between FO 6167 and the bacterial cell wall.

Hemodynamic effects of positive end-expiratory pressure during partial liquid ventilation in newborn lambs

BACKGROUND/PURPOSE

The aim of this study was to compare the effect of positive end-expiratory pressure (PEEP) application on hemodynamics, lung mechanics, and oxygenation in the intact newborn lung during conventional ventilation (CV) and partial liquid ventilation (PLV) at functional residual capacity (FRC). CV or PLV modes of ventilation do not affect hemodynamics nor the optimum PEEP for oxygenation.

METHODS

Seven newborn lambs (1 to 3 days old) were instrumented to measure pulmonary hemodynamics and airway mechanics. Each lamb was used as their own control to compare different modes of ventilation (CV followed by PLV) under graded variations of PEEP (4, 8, 12, and 16 cm H(2)O) on the influence on pulmonary blood flow and pulmonary vascular resistance.

RESULTS

There was a significant drop in pulmonary blood flow (PBF) from baseline (PEEP of 4 cm H(2)O on CV, 1,229 +/- 377 mL/min) in both modes of ventilation on a PEEP of 16 cm H(2)O (CV, 750 +/- 318 mL/min v PLV, 926 +/- 396 mL/min, respectively; P <.05). Peak inspiratory pressure (PIP) was higher on PLV at PEEP states of 4 cm H(2)O (16.5 +/- 1.3 cm H(2)O to 10.6 +/- 2.1 cm H(2)O; P <.05) and 8 cm H(2)O (18.8 +/- 2.2 cm H(2)O to 15.1 +/- 2.6 cm H(2)O; P <.05) when compared with CV. Conversely, PIP required to maintain the pCO(2) was lower on PLV at PEEP states of 12 (22.5 +/- 3.6 cm H(2)O to 24.2 +/- 3.8 cm H(2)O; P <.05) and 16 cm H(2)O (27.0 +/- 1.6 cm H(2)O to 34.0 +/- 5.9 cm H(2)O; P <.05).

CONCLUSIONS

Hemodynamically, CO is impaired at a PEEP above 12 cm H(2)O in intact lungs. PFC at FRC does provide an advantage in lung mechanics more than 10 to 12 cm H(2)O of PEEP by decreasing the amount PIP needed to achieve the similar levels of gas exchange and minute ventilation, implying a reduced risk for barotrauma with chronic ventilation. Thus, selection of the appropriate level of PEEP appears to be important if PLV is to be utilized at FRC. The best strategy for PLV, including the selection of PEEP, remains to be determined.

Intratracheal administration of perfluorochemical-gentamicin suspension: a comparison to intravenous administration in normal and injured lungs

Respiratory infections can lead to acute lung injury and perfusion abnormalities. We hypothesized that intratracheal (IT) administration of a perfluorochemical (PFC) gentamicin (G) suspension as compared to intravenous (IV) administration of gentamicin will result in higher lung tissue levels of gentamicin, while maintaining safe serum levels. To test this hypothesis, 21 lambs with normal and acid injured lungs were studied for 4 hr, using 2 different drug delivery methods, IT and IV. Lungs were injured with warm HCl acid in saline lavage, followed by partial liquid ventilation with perflubron (bolus FRC = 20 mL/kg). G at a dose of 5 mg/kg was delivered either IT (G-PFC; 20 mL/kg) or IV (aqueous injection with IT 20 mL/kg PFC alone). Throughout the study, serum G levels, arterial blood gases, respiratory system compliance, and mean arterial blood pressure were measured. Lung tissue G levels were measured at 4 hr and averaged across lobes. Physiologic gas exchange and pulmonary function were maintained throughout the protocol for both the normal and injured lungs. Intravenously administered G resulted in an initial 5-min serum concentration of 43 +/- 2.5 mcg/mL, followed by an exponential decline over the 4-hr protocol to a level of 2.1 +/- 0.23 mcg/mL at hr 4. The intratracheally administered G suspension resulted in a 5-min serum concentration of 1.8 +/- 0.98 mcg/mL and remained relatively constant throughout the protocol, with a 4-hr level of 1.6 +/- 0.29 mcg/mL. With respect to lung tissue G levels, IT administration was significantly more effective in delivering the drug to the normal lungs than IV (31.4 +/- 3.3 mcg/g vs. 4.0 +/- 0.7 mcg/g) 4 hr after administration. In the lung injury group, there was a small but significant difference in lung tissue G levels, with the IT-administered perfluorochemical-G suspension achieving greater levels than the IV-administered G (11.9 +/- 0.52 mcg/g vs. 10.1 +/- 0.8 mcg/g). Additionally, the drug delivered IV and IT in both the normal and injured lung models was homogeneously distributed throughout the lung. These data show that G lung tissue levels in both normal and injured lungs were higher in the IT group when compared to IV administration. The results of this study demonstrate that in normal and injured lungs, homogeneous G lung tissue levels can be more effectively achieved at lower serum levels when delivered IT in a G-PFC suspension as compared to IV administration.

Persistent improvement of gas exchange and lung mechanics by aerosolized perfluorocarbon

The effect of aerosolized perfluorocarbon (PFC) (FC77) on pulmonary gas exchange and lung mechanics was studied in a surfactant depleted piglet model. Sixty minutes after induction of lung injury by bronchoalveolar lavage, 20 piglets were randomized to receive aerosolized PFC (Aerosol-PFC, 10 ml/kg/h, n = 5), partial liquid ventilation (PLV) at FRC capacity volume (FRC-PLV, 30 ml/kg, n = 5) or low volume (LV-PLV, 10 ml/kg/h, n = 5), or intermittent mandatory ventilation (IMV) (Control, n = 5). After 2 h, perfluorocarbon application was stopped and IMV was continued for 6 h. Sixty minutes after the onset of therapy, PaO2 was significantly higher and PaCO2 was significantly lower in the Aerosol-PFC and the FRC-PLV groups than in the LV-PLV and the Control groups; p < 0.001. Six hours after treatment, maximum PaO2 was found in the Aerosol-PFC group: 406.4 +/- 26.9 mm Hg, FRC-PLV: 217.3 +/- 50.5 mm Hg, LV-PLV: 96.3 +/- 18.9 mm Hg, Control: 67.6 +/- 8.4 mm Hg; p < 0.001. PaCO2 was lowest in the Aerosol-PFC group: 24.2 +/- 1.7 mm Hg, FRC-PLV: 35.9 +/- 2.8 mm Hg, LV-PLV: 56.7 +/- 12.4 mm Hg, Control: 60.6 +/- 5.1 mm Hg; p < 0.01. Dynamic compliance (C20/c) was highest in the Aerosol-PFC group; p < 0.01. Aerosolized perfluorocarbon improved pulmonary gas exchange and lung mechanics as effectively as PLV did in surfactant-depleted piglets, and the improvement was sustained longer.

A comparison of surfactant delivery with conventional mechanical ventilation and partial liquid ventilation in meconium aspiration injury

The objective of this study was to compare surfactant (SF) distribution and physiological effects after standard SF delivery during conventional mechanical ventilation (CMV) with that using partial liquid ventilation (PLV). A model of meconium aspiration syndrome (MAS) was developed using two groups of adult rats (n = 14). After meconium instillation of 2.5 ml kg(-1) (20% v/w), SF/CMV: (n = 7) CMV and SF/PLV: (n = 7) PLV, received 14C-labeled surfactant (4 ml kg(-1)) delivered intratracheally in four aliquots over 20 min in both groups. Sequential measurements of arterial blood chemistry and lung mechanics were performed in all animals. At the conclusion of experiments, lungs were inflated (30 cmH2O), dried, sectioned and evaluated for radioactivity in disintegrations per minute (DPM). Surfactant distribution was improved (P< 0.01) with PLV as compared to CMV with 48.8% of the pieces vs. 30.9% of the pieces receiving within 25% of the mean amount of surfactant, respectively. Further, regional distribution was also significantly more uniform with PLV than CMV: left vs right (P<0.01) lung and ventral vs. dorsal (P<0.01) regions. Finally, arterial PO2 and ventilation efficiency index were significantly (P<0.01) greater post-treatment in SF/PLV than SF/CMV. These data demonstrate surfactant delivery with PLV, as compared to CMV alone, to be an improved method of delivering surfactant in MAS and suggest the possible utility of SF/PLV combination therapy for its treatment of other etiologies of neonatal respiratory distress.

Partial liquid ventilation in severely surfactant-depleted, spontaneously breathing rabbits supported by proportional assist ventilation

OBJECTIVE

We hypothesized that partial liquid ventilation (PLV) would improve oxygenation in nonparalyzed, surfactant-deficient rabbits breathing spontaneously while supported by proportional assist ventilation (PAV). This ventilation mode compensates for low pulmonary compliance and high resistance and thereby facilitates spontaneous breathing.

DESIGN

Randomized trial.

SETTING

University animal research facility.

SUBJECTS

Twenty-six anesthetized New Zealand white rabbits weighing 2592 +/- 237g (mean +/- sd).

INTERVENTIONS

After pulmonary lavage (target Pao2 <100 mm Hg on mechanical ventilation with 6 cm H2O of positive end-expiratory pressure [PEEP] and an Fio2 of 1.0), rabbits were randomized to PAV (PEEP of 8 cm H2O) with or without PLV. PLV rabbits received 25 mL/kg of perfluorocarbon by intratracheal infusion (1 mL/kg/min). Pao2, Paco2, tidal volume, respiratory rate, minute ventilation, mean airway pressure, arterial blood pressure, heart rate, pulmonary compliance, and airway resistance were measured. Evaporated perfluorocarbon was refilled every 30 mins in PLV animals. After 5 hrs, animals were killed and lungs were removed. Lung injury was evaluated using a histologic score.

MAIN RESULTS

Pao2 and compliance were significantly higher in PLV rabbits compared with controls (p <.05, analysis of variance for repeated measures). All other parameters were similar in both groups.

CONCLUSIONS

PLV improved oxygenation and pulmonary compliance in spontaneously breathing, severely surfactant-depleted rabbits supported by PAV. The severity of lung injury by histology was unaffected.

Thermal stability and transition studies with a hybrid warming device for neonates

OBJECTIVE

The use of both warmer beds and incubators is common in neonatal intensive care units (NICU), and transferring between these two warming devices is a routine and necessary event. This study was designed to evaluate the efficacy of a new hybrid-warming device, the Versalet, in transitioning a preterm animal from a warmer bed to an incubator mode and back.

STUDY DESIGN

Nine premature lambs were randomized, following delivery, to receive thermal support from a conventional warming bed and an incubator (control group), or from the Versalet (study group) in the warmer bed and incubator modes. Core and various surface temperatures, as well as physiological parameters were measured first during warming in the radiant warmer bed mode, Versalet or Resuscitaire and then during transition to the incubator mode, Versalet or Isolette, and then back to the warmer bed mode.

RESULTS

The animals remained stable during all the transitions. Despite careful planning, adverse events occurred in the control group during transfers. There were no significant differences in the temperature or physiologic profiles during any of the transitions in either group.

CONCLUSION

Compared with the standard warming technique used in NICUs (separate warmer bed and incubator), the Versalet provides similar thermal and cardiovascular stability without adverse events during transition to different modes of warming. The degree to which this device would contribute to ease of management and improved outcomes in humans needs to be evaluated in a clinical trial.