Neutrophil accumulation is reduced during partial liquid ventilation

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.

High-frequency oscillatory ventilation combined with partial liquid ventilation in experimental lung injury: effects on lung cell apoptosis

Objective

To investigate the effects of high-frequency oscillatory ventilation (HFOV) and partial liquid ventilation (PLV) on apoptosis of lung tissue induced by steam inhalation injury in rabbit.

Design

A prospective, randomized, controlled, multiple-group study.

Setting

An animal research laboratory centre in a university burns centre.

Subjects

New Zealand rabbits (n = 32; 2.25 ± 0.25 kg) of either sex.

Interventions

The animals were ventilated by HFOV with a mean airway pressure of 10 cm H₂O, a frequency of 10 Hz, an amplitude of 20 cm H₂O, an inspiratory:expiratory ratio of 1:1, and an FiO₂ of 1.0. After the induction of acute lung injury (ALI) by steam inhalation, the animals were randomly divided into four groups: CMV, HFOV, CMV + PLV, HFOV + PLV group. Then they were ventilated for 4 h by CMV, HFOV, CMV + PLV and HFOV + PLV, respectively. After the experimental period, cell apoptosis and apoptosis indexes in the lung tissue were assessed with TUNEL FragELTM (Fragment End Labeling).

Results

Lung tissue apoptosis indexes in HFOV group and HFOV + PLV group were lower than that of in CMV group and CMV + PLV group; between-group comparison had significant difference (P < 0.01). HFOV + PLV group showed lowest apoptosis indexes.

Conclusion

HFOV combined with PLV can suppress lung tissue apoptosis induced by steam inhalation.

Intrarectal administration of oxygenated perfluorodecalin promotes healing of murine colitis by targeting inflammatory hypoxia

Intestinal inflammation is associated with enhanced mucosal hypoxia, which contributes to the ongoing inflammatory process and hampers appropriate mucosal healing. We questioned whether local treatment with an oxygen (O(2))-carrying and -releasing molecule (oxygenated perfluorodecalin, O(2)-PFD) could positively influence the course of experimental colitis. The impact of intrarectal (IR) treatment with O(2)-PFD was tested using the murine dextran sodium sulfate (DSS)-induced model of distal colitis, both in preventive and therapeutic settings. Colonic mucosal hypoxia was visualized by pimonidazole staining. Colonic permeability was evaluated with FITC-dextran. In the preventive study, mice treated with O(2)-PFD were protected against DSS colitis compared with saline-treated mice, as demonstrated by reduced shortening of colon length, reduced colonic tumor necrosis factor-alpha levels and a lower histological inflammation score (P<0.05 for all parameters). In the therapeutic study, administration of O(2)-PFD resulted in accelerated recovery of colitis compared with saline-treated littermates, and this was reflected by a better weight evolution, lower myeloperoxidase activity and a lower histological inflammation score (P<0.05 for all parameters). It was found that O(2)-PFD established its therapeutic effects through (1) intrinsic anti-inflammatory effects of the PFD molecule and (2) O(2)-induced preservation and healing of the intestinal epithelial surface. Further in vitro and in vivo studies showed that the barrier-protective activity of O(2)-PFD was obtained through prevention of colonocyte apoptosis and stimulation of colonocyte proliferation during inflammatory hypoxia. These data show that IR treatment with O(2)-PFD promotes colitis healing by the combined actions of direct anti-inflammatory effects and O(2)-induced restitution of the epithelial barrier. As such, O(2)-PFD enemas could be an attractive treatment option for patients with distal inflammatory bowel disease.

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.

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.

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

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

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.

Intrapulmonary perfluorooctyl bromide instillation in fetal rabbits

BACKGROUND

Instilling perfluorooctyl bromide (PFOB) into the fetal lung may lead to alveolar distension.

OBJECTIVE

The aim of the study was to evaluate the safety of PFOB instillation into fetal lungs and to determine the radiographic distribution and tissue concentration of PFOB in New Zealand white rabbits.

METHODS

Sibling fetuses of pregnant (day 27) New Zealand white rabbits were randomized to intratracheal instillation of 1 mL PFOB with tracheal ligation, instillation without ligation, and unmanipulated controls. The maternal animals were killed directly after instillation, at 3 or 6 hours (n = 10 each). For each study cohort, we determined fetal lung/body weight (FLBW) ratios, the radiographic distribution of PFOB, as well as pulmonary PFOB and water content by tissue distillation. PFOB concentrations in maternal and fetal tissues were assessed by gas chromatography.

RESULTS

The relative amount of fetal lung PFOB recovered by fractional distillation was highest in ligated (25%) and lower in unligated lungs (9%). Extrapulmonary PFOB was found in the fetal brain (2.0 +/- 0.7 ppm), but not in any other fetal or maternal tissues. Mean FLBW ratios were highest in ligated fetuses, followed by unligated fetuses and controls. PFOB partially displaced fetal lung water. PFOB was visible in the lungs of all treated fetuses. Fetal survival between manipulated and unmanipulated fetuses did not differ.

CONCLUSIONS

After prenatal intrapulmonary instillation, some PFOB remains in the lung, even if the trachea is not ligated, and may exert distending pressure on the alveoli.

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.

Partial liquid ventilation with FC-77 suppresses the release of lipid mediators in rat acute lung injury model

OBJECTIVE

To investigate whether the release of lipid mediators is suppressed in rats with experimentally induced acute lung injury managed with partial liquid ventilation (PLV) using FC-77.

DESIGN

Prospective, randomized controlled study.

SETTING

Research laboratory in a university.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

After tracheostomy was performed under general anesthesia, lung injury was induced by intratracheal instillation of HCl. The PLV group was then subjected to conventional gas ventilation for 30 mins, followed by PLV using FC-77. The control group was subjected to conventional gas ventilation throughout the study period.

MEASUREMENTS AND MAIN RESULTS

In the PLV group the following results were obtained: a) impaired oxygenation was markedly improved; b) the increase in the serum levels of lipid mediators such as leukotriene B4, thromboxane A2, and 6-keto-prostaglandin F1alpha was suppressed; and c) the increase in the concentrations of leukotriene B4, thromboxane A2, and 6-keto-prostaglandin F1alpha in the total lung homogenate at 180 mins after lung injury was also suppressed.

CONCLUSION

This study indicates that PLV using FC-77 suppresses the release of lipid mediators in our rat model of acute lung injury. However, further investigation is needed to clarify the precise mechanism of this effect.

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.

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.

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.

Transient increase in lung epithelial tight junction permeability: an additional mechanism for enhancement of lung transgene expression by perfluorochemical liquids

Intratracheal instillation of perfluorochemical (PFC) liquids enhances lung epithelial transgene expression by improved vector propulsion throughout lung airways. We now demonstrate that PFC liquids also facilitate gene transfer by increasing transepithelial permeability. Apical application of PFC liquid to well-differentiated human airway epithelial cells resulted in a transient decrease in transepithelial resistance peaking approximately 2 h after PFC liquid administration and returning to normal approximately 24 h later. The permeability change was sufficient to enhance access of apically applied 100-nm latex beads and adenoviral vectors to the basolateral side of the culture. Adenovirus-mediated gene expression was concurrently enhanced. Following intratracheal instillation of PFC liquid into mouse lungs, tight junction permeability, as assessed by electron microscopic evaluation of lanthanum deposition, was increased with peak effect between 6 h and 1 day after instillation. Importantly, alveolar-capillary permeability remained unchanged with the treatment. Administration of PFC liquid 6 h or 1 day, but not 3 days, prior to instillation of a recombinant adenovirus vector enhanced gene expression comparable to that observed with concurrent administration of PFC liquid and vector. We conclude that transient increase in epithelial permeability after PFC liquid administration contributes to the enhancement of adenovirus vector-mediated gene expression in lung epithelium.

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.

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.

Effect of partial liquid ventilation on bacterial clearance during Pseudomonas aeruginosa-induced lung injury in rats

OBJECTIVE

Partial liquid ventilation (PLV) has been shown to exhibit anti-inflammatory properties during non-infectious models of acute lung injury. The aim of this experimental study was to assess the effects of PLV on bacterial clearance during Pseudomonas aeruginosa-induced pneumonia in rats.

DESIGN

The rats were assigned to four groups 4 h after bacterial challenge according to the kind of mechanical ventilation [gas ventilation (GV) or PLV, 6 ml/kg perflubron plus 2 ml/kg per h] and to the level of PEEP used (3 or 8 cm of water). Physiologic measures were recorded during anesthesia (arterial blood gases, airway and blood pressures) for 4 subsequent hours until sacrifice.

RESULTS

No improvement of oxygenation was demonstrated in any group. The bacterial counts were higher in PLV-PEEP 8 rats compared to GV-PEEP 8 rats: median, 1.7.10(4) cfu (25th-75th percentiles, 1.2.10(4)-1.8.10(4)) versus 1.1.10(4) (8.7.10(3)-1.3.10(4))/ml of BAL fluid and 4.0.10(6) cfu (2.0.10(6)-5.5.10(6)) versus 1.7.10(6) cfu (9.7.10(5)-3.2.10(6))/ml of lung homogenate, respectively ( P<0.05, n=8/10 surviving rats per group). PEEP 8 was associated with a significant decrease in neutrophil recruitment in BAL fluid compared to PEEP 3 in both GV and PLV groups. Additional in vitro experiments demonstrated that perflubron induced a decrease in phagocytosis of P. aeruginosa by alveolar neutrophils.

CONCLUSIONS

These results demonstrate that PLV is associated with an impaired bacterial clearance during early pneumonia in rats, which could have been favored by decreased bacterial phagocytosis by neutrophils.

A prospective, randomized pilot trial of perfluorocarbon-induced lung growth in newborns with congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Initial laboratory and clinical data suggest that partial liquid ventilation (PLV) can enhance pulmonary function and that lung growth can be induced via distension of the newborn lung using perfluorocarbon in patients with congenital diaphragmatic hernia (CDH). The authors, therefore, performed a prospective, randomized pilot study evaluating PLV and perfluorocarbon-induced lung growth (PILG) in newborns with CDH on extracorporeal life support (ECLS) at 6 medical centers.

METHODS

Patients were selected randomly using a permuted block design to PLV/PILG (n = 8) or conventional mechanical ventilation (CMV/control, n = 5). Patients in the PILG group received daily doses which filled the lungs with perflubron for up to 7 days and were placed on continuous positive airway pressure of 5 to 8 cm H2O. CMV patients were treated with standard mechanical ventilation while on extracorporeal membrane oxygenation (ECMO).

RESULTS

A total of 13 patients were evaluated in this study. All 3 patients enrolled without being on ECLS rapidly transitioned to ECLS. The study, therefore, effectively evaluated PILG (n = 8) versus standard ventilation (control, n = 5) on ECLS. Mean (+/- SE) gestational age was 37 +/- 1 weeks and weight was 3.1 +/- 0.1 kg. Time on ECMO was 9.8 +/- 2.3 days in the PILG and 14.5 +/- 3.5 days (P =.58) in the control group. Survival rate in the PILG group was 6 of 8 (75%), whereas survival rate was 2 of 5 (40%) in the control group (P =.50). The number of days free from the ventilator in the first 28 days (VFD) was 6.3 +/- 3.3 days with PILG and 4.6 +/- 4.6 days with control (P =.9). Causes of death in the PILG group included sepsis and renal failure in one patient and pulmonary hypertension in the other. There were no safety issues, and the deaths in the PILG group did not appear to be related to the administration of perflubron.

CONCLUSIONS

These data show that PILG can be performed safely. The survival rate, VFD, and time on ECMO data, although not conclusive, are encouraging and indicate the need for a definitive trial of this novel intervention in these neonates with high mortality.

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.

Aerosolized perfluorocarbon reduces adhesion molecule gene expression and neutrophil sequestration in acute respiratory distress

In acute respiratory distress syndrome, neutrophil migration into the lung plays a key role in the development of lung injury. To study the effect of different modes of ventilation with perfluorocarbon (FC77), intrapulmonary neutrophil accumulation and mRNA expression of E-selectin, P-selectin and intercellular adhesion molecule-1 (ICAM-1), mediating leukocyte sequestration, were measured in surfactant depleted piglets. After bronchoalveolar lavage, 20 animals either received aerosolized perfluorocarbon (Aerosol-PFC), partial liquid ventilation (PLV) with perfluorocarbon at functional residual capacity filling volume (FRC-PLV) or at low volume (LV-PLV) or intermittent mandatory ventilation (control). After 2 h of perfluorocarbon application, intermittent mandatory ventilation was continued for 6 h. In the Aerosol-PFC group, all measured adhesion molecules showed a significantly reduced gene expression compared to controls. FRC-PFC treatment was effective in significantly diminishing P-selectin and ICAM-1 mRNA expression. Relative lung tissue neutrophil counts were significantly reduced in the Aerosol-PFC and the FRC-PLV group. Treatment with aerosolized perfluorocarbon is at least as effective as partial liquid ventilation at FRC volume in reducing pulmonary adhesion molecule expression and neutrophil accumulation in acute respiratory distress syndrome.

Support of respiratory failure in the pediatric surgical patient

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

Comparison of surfactant and perfluorochemical liquid enhanced adenovirus-mediated gene transfer in normal rat lung

Both surfactant- and perfluorochemical (PFC)-based vehicles enhance adenovirus-mediated gene transfer in the lung. To compare the relative effects of surfactant and PFC liquid, we infected orotracheally intubated Sprague-Dawley rats with 4 x 10(9) pfu of an E1a(-)/E3(-) adenovirus expressing either an Escherichia coli lacZ (AdlacZ) mini-gene or no cDNA (Adnull). Surfactant-mediated delivery was achieved via instillation of four, 200-microl aliquots of virus suspended in a 50% surfactant (Survanta) vehicle over a 15-minute period. PFC rats received virus in 100 microl of saline followed by instillation of the PFC liquid FC-75 (10 cc/kg body weight) over a 2- to 3- minute period. Lungs were collected 3 days later for measurement of beta-galactosidase (beta-gal) expression and indices of inflammation. Both PFC liquid and surfactant-based vehicles produced widespread beta-gal expression and increased total beta-gal activity over that observed with instillation of vector alone. Both vehicles comparably increased bronchoalveolar lavage fluid (BALF), total cell counts, neutrophils, total protein, and IFN(gamma). FC-75 was also associated with increased BALF IL1beta. In conclusion, surfactant and FC-75 are similarly effective vehicles for adenovirus-mediated gene transfer to the lung.

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.

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.

Effects of partial liquid ventilation on unilateral lung injury in dogs

STUDY OBJECTIVE

The overall physiologic effect of partial liquid ventilation (PLV) in the setting of unilateral lung injury remains unclear. Therefore, we evaluated the effect of PLV on gas exchange in unilateral lung injury.

DESIGN AND METHODS

Left unilateral lung injury was induced in 14 adult dogs by oleic acid instillation into a left pulmonary artery. The animals were divided into two groups: gas ventilation (GV) and PLV. During both GV and PLV, systemic blood gas levels were analyzed. Oxygen consumption (O(2)), carbon dioxide production (CO(2)) and pulmonary blood flow (Q) of both the right lung (uninjured lung) and left lung (injured lung) were measured.

RESULTS

During PLV, O(2) of the injured left lung (o(2)-injured), CO(2) of the injured left lung (CO(2)-injured), and Q of the injured left lung (Q-injured) were greater than those in GV (O(2)-injured, 41.6 mL/min vs 23.4 mL/min, p = 0.006; CO(2)-injured, 34.4 mL/min vs 25.5 mL/min, p = 0.026; and Q-injured, 0.47 L/min vs 0.22 L/min, p = 0.002, respectively). However, overall PaO(2) during PLV was less than that during GV, likely due to either a redistribution of Q toward the injured lung (PLV Q-injured, 0.47 L/min vs GV Q-injured, 0.22 L/min; p = 0.002) or reduced gas exchange efficiency in the healthy lung.

CONCLUSIONS

We conclude that in our model, PLV increases O(2) and VCO(2) in the injured lung. However, over all gas exchange efficiency is reduced.

Use of perflubron to enhance lung gene expression: safety and initial efficacy studies in non-human primates

Use of perflubron (LiquiVent) and other perfluorochemical liquids during intratracheal administration of adenovirus and AAV vectors has been shown to improve total gene expression as well as distribution of expression throughout lungs of spontaneously breathing rodents. To determine if this method could be safely and easily extended to non-human primates, we carried out a pilot investigation in six spontaneously breathing rhesus macaques. Two animals received bronchoscopic administration of recombinant adenovirus vector (type 5 E1-deleted AdCMVlacZ, 4.6 x 10(10) plaque forming units/animal), two animals received vector followed by instillation of perflubron, and two animals received perflubron alone. Instillation of perflubron was well tolerated by the animals and, once recovered from anesthesia, all animals behaved and fed normally until lung harvest. Serial X-rays demonstrated that the perflubron had cleared from lungs of three animals by 48 hours after administration; the fourth animal had a small amount of residual perflubron. Apart from a mild elevation in hepatocellular enzymes, no significant abnormality was noted in complete blood count or serum electrolytes and chemistries. In animals receiving either vector alone or vector with perflubron, in situ beta-galactosidase expression was observed in a variety of cells including large airway, bronchiolar, and alveolar epithelial cells. In summary, use of perflubron was well tolerated in spontaneously breathing macaques. Further studies in larger numbers of animals will help assess the potential efficacy of perflubron for enhancing gene expression and elucidate effects on local and systemic inflammatory responses.

Prevention of ventilator-induced lung injury with partial liquid ventilation

BACKGROUND/PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Clinical correlation with changing radiographic appearance during partial liquid ventilation

STUDY OBJECTIVES

To evaluate the chest radiographic filling pattern associated with partial liquid ventilation (PLV) with the perfluorochemical perflubron (LiquiVent; Alliance Pharmaceutical Corp; San Diego CA) as a function of dose and timing.

DESIGN

Post hoc review of chest radiographs by three independent observers with correlation to clinical variables.

SETTING

Phase II randomized, uncontrolled, prospective, multicenter clinical trial.

PATIENTS

Sixteen adult patients with diffuse bilateral infiltrates consistent with acute lung injury and a PaO(2)/fraction of inspired oxygen (FIO(2)) ratio < 300 with positive end-expiratory pressure of 13 cm H(2)O and FIO(2) > or = 0.5.

INTERVENTIONS

All patients were treated with either a 10-mL/kg or 20-mL/kg loading dose of perflubron followed by maintenance dosing at 3-h intervals to protocol-determined levels.

RESULTS

There was a significant relationship between inhomogeneous radiographic filling during the first 48 h of treatment and the use of the lower loading dose of perflubron. Inhomogeneous radiographic filling (in 5 patients) was associated with a lower high-dose/FIO(2) ratio at 24 h compared with the remaining patients. These differences resolved by 48 h. There were no other statistically significant correlations identified.

CONCLUSIONS

The radiographic appearance of PLV with perflubron appears to depend on the dose administered. Lower doses can be associated with both inhomogeneous radiographic filling and a transient deterioration in oxygenation during the first 24 to 48 h of treatment.

Use of Perfluorochemical Liquid Allows Earlier Detection of Gene Expression and Use of Less Vector in Normal Lung and Enhances Gene Expression in Acutely Injured Lung

One of the obstacles to successful lung gene transfer is effective delivery of vector to lung, particularly injured or diseased lung. We have previously demonstrated that intratracheal instillation of perfluorochemical (PFC) liquids along with instillation of recombinant adenovirus and adeno-associated virus vectors, or with cationic liposome vectors, increased total lung gene expression and enhanced distribution of gene expression throughout the lung. To further explore the potential benefits of PFC liquid use, we evaluated the effect of PFC liquid instillation on several other aspects of adenovirus-mediated gene expression in lung. Use of PFC liquid resulted in earlier detection of gene expression and allowed the use of less vector to achieve expression comparable to that observed with the use of higher amounts of vector alone. Using PFC liquid also enhanced gene expression in a rodent model of acute lung injury. PFC liquid did cause a transient inflammation when instilled into normal lungs but did not cause any additional inflammation when instilled alone or with adenovirus vector into acutely injured lungs. Thus, PFC liquid may be a useful adjunct for clinical lung gene transfer, particularly for injured or diseased lungs.

Liquid lung ventilation reduces neutrophil sequestration in a neonatal swine model of cardiopulmonary bypass

OBJECTIVE

Liquid lung ventilation has been demonstrated to improve cardiorespiratory function after cardiopulmonary bypass. We hypothesized that liquid lung ventilation (LLV) would decrease the pulmonary inflammatory response after cardiopulmonary bypass (CPB).

DESIGN

Prospective, randomized, experimental, controlled, nonblinded study.

SETTING

Animal research laboratory at a university setting.

SUBJECTS

A total of 24 neonatal piglets.

INTERVENTIONS

After intubation with a cuffed endotracheal tube, swine were conventionally ventilated. After surgical cannulation, each piglet was placed on conventional nonpulsatile CPB and cooled to 18 degrees C (64.4 degrees F). Subsequently, the animals were exposed to 90 mins of low-flow CPB (35 mL/kg/min). Animals were rewarmed to 37 degrees C (98.6 degrees F), removed from CPB, and ventilated for 90 min. Ten animals received conventional gas ventilation only (control), seven received initiation of LLV before CPB (prevention), and seven received initiation of LLV during the rewarming phase of CPB (treatment). After the animals were killed, the lungs were removed en bloc. The left lobe was dissected and formalin-fixed at 20 cm H2O overnight, followed by paraffin embedding. Sections were taken from the paraffin-embedded lungs. Neutrophil accumulation and lung injury were assessed by histochemical staining with leukocyte esterase and morphometrics, respectively. One hundred microscopic images were digitized from each tissue sample for lung morphometrics, and neutrophil counts were obtained from every fifth image.

MEASUREMENTS AND MAIN RESULTS

Lung tissue sections showed a significantly lower number of neutrophils per alveolar area in the prevention and treatment groups than in the control group (control 681 +/- 65, prevention 380 +/- 49, treatment 412 +/- 101 neutrophils per alveolar area [cells/mm2]; p <.05 for both prevention and treatment compared with control). There were no differences in lung injury as assessed with morphometrics or hemodynamic measurements between any of the three groups.

CONCLUSIONS

The data suggest that LLV reduces the CPB-induced neutrophil sequestration in the pulmonary parenchyma independent of its effects on the circulatory physiology or evidence of early lung injury.

Spontaneous breathing during partial liquid ventilation in animals with meconium aspiration

Partial liquid ventilation (PLV) has been shown to improve gas exchange in paralyzed animals and humans with lung disease. The present study tests the hypothesis that PLV improves gas exchange in spontaneously breathing animals with meconium aspiration supported by proportional assist ventilation. Twenty-five adult anesthetized intubated rabbits with experimental meconium aspiration were randomized to gas ventilation (GV) or PLV while being supported by proportional assist ventilation. Minute ventilation, tidal volume, respiratory rate, mean airway pressure, heart rate, and mean arterial and pulmonary arterial pressure were recorded continuously. Every 30 min, arterial blood gases were obtained, and lung compliance, airway resistance, work of breathing, and cardiac output were measured. Animals were sacrificed after 5 h to obtain lung histology. More PLV animals survived until the end of the study period. PaO(2) (14.5 +/- 4.5 versus 25.6 +/- 6.7 kPa; p < 0.01; GV versus PLV) and lung compliance (4.3 +/- 0.4 versus 6.1 +/- 1.2 mL.kPa(-1).kg(-1); p < 0.001) were improved during PLV, resulting in a lower work of breathing (5.3 +/- 2.8 versus 3.5 +/- 1.5 mL.kPa.kg(-1); p < 0.05) and less need for ventilatory support. Minute ventilation and respiratory rate were higher during GV versus PLV, resulting in a slightly lower PaCO(2) (3.9 +/- 0.5 versus 4.5 +/- 0.7 kPa; p < 0.05). Histologic evaluation showed more atelectasis, inflammatory changes, and hemorrhage in GV animals. Other parameters measured were similar. We conclude that PLV improves oxygenation, lung compliance, and survival and results in less lung injury in spontaneously breathing animals with meconium aspiration when supported by proportional assist ventilation.

Liquid ventilation

Partial liquid ventilation (PLV) developed considerably in the clinical and experimental fields during the past few years. In addition to improved oxygenation and lung mechanics by perfluorocarbon (PFC) administration, recent animal studies have tried to optimize PLV by evaluating the most appropriate ventilatory mode to use during PLV and by adjusting the best level of positive end-expiratory pressure (PEEP). Other pathophysiological aspects of acute lung injury that may be positively affected by liquid ventilation have been studied, including regional blood flow redistribution, reduction in ventilator-induced lung injury, and antiinflammatory properties of PFC. Although the precise dosing of PFC is debated, evidence from several experimental studies supports the use of smaller doses of PFC because larger doses increase the occurrence of baro- and volutrauma. In the clinical field, after promising data from preliminary studies, an international randomized controlled trial is on the verge of completion.

Partial liquid ventilation ventilates better than gas ventilation

Partial liquid ventilation (PLV) improves oxygenation in several models of lung injury. However, PLV has only been compared with conventional gas ventilation (GV) with low PEEP. Both PLV and GV can markedly improve oxygenation when PEEP is set above the lower corner pressure (Plc) on the inspiratory pressure-volume (P-V) curve of the total respiratory system. We questioned if the use of PEEP set above the Plc during PLV and GV would result in similar gas exchange. Lung injury was induced in 12 sheep by saline lavage before randomization to PLV (n = 6) or GV (n = 6). Animals in the PLV group were filled with perflubron (22 ml/kg) until a meniscus at the teeth was observed. Both groups were then ventilated with pressure control (FI(O(2)), 1.0; rate, 20/min; I:E, 1:1) and PEEP (1 cm H(2)O above the Plc on the inspiratory P-V curve). Peak inspiratory pressure (PIP) was limited to 35 cm H(2)O. Animals were ventilated for 5 h and then killed for histologic examinations. All 12 animals survived the 5-h ventilation period. After increasing PEEP above Plc, Pa(O(2)) increased significantly (p < 0.01) in both the GV and the PLV groups, but it did not differ significantly between groups (p = 0.86) at any time during the experiment. Pa(CO(2)) and VD/VT in GV increased markedly throughout the experiment after increasing PEEP (p < 0.001), but there was no significant change in Pa(CO(2)) in PLV (p = 0.13). Mean arterial blood pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, and central venous pressure, increased and SVR decreased in GV (p < 0.05). The extent and the severity of lung injury in the dependent regions was greater in the GV group (p < 0.05). Both PLV and GV improved oxygenation, but PLV resulted in better ventilation than GV while preserving lung structure when PEEP was set 1 cm H(2)O above the Plc and PIP limited to 35 cm H(2)O.

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

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

Partial liquid ventilation with perfluorocarbon in acute lung injury: light and transmission electron microscopy studies

Liquid ventilation using perfluorocarbon has been shown to improve gas exchange in animal models of acute lung injury as well as in children with acute respiratory distress syndrome. This study was designed to define structural features of lung injury following partial liquid ventilation (PLV) using light and transmission electron microscopy in a rabbit model of acute respiratory distress. Animals were treated with either conventional mechanical ventilation (CMV-gas) (n = 6) or PLV (n = 5) for 4 h after the induction of acute lung injury with saline lavage. Control animals were killed after the lung injury. PLV significantly improved alveolar-arterial oxygen tension and the oxygen index compared with CMV (P < 0.05). Morphometric studies using light microscopy show less alveolar hemorrhage, less edema, and fewer hyaline membranes in the PLV group (P < 0.05). Polymorphonuclear leukocyte sequestration in lung capillaries (11.4 +/- 1.5 versus 19.2 +/- 3 x 10(8)/ml, P < 0.05, PLV versus CMV) and migration into airspaces (3.1 +/- 1.2 versus 4.5 +/- 1.1 x 10(8)/ml, P < 0.05, PLV versus CMV) were lower in the gravity-dependent lung regions. There were fewer alveolar macrophages in the PLV group compared with other groups (P < 0.05). Fluorescence microscopy analysis shows fewer type II alveolar epithelial cells in the CMV group and brighter type II cells in the PLV group. Transmission electron microscopy studies show more alveolar wall damage in the CMV group, with type II cells detached from their basement membrane with fewer surfactant-containing lamellar bodies. We conclude that quantitative histologic analysis shows less lung damage and inflammation when perfluorocarbon is combined with CMV in the management of acute respiratory distress syndrome.

Partial liquid ventilation decreases serum tumor necrosis factor-alpha concentrations in a rat acid aspiration lung injury model

OBJECTIVE

To examine the hypothesis that partial liquid ventilation (PLV) with perfluorocarbon would decrease serum tumor necrosis factor-alpha concentrations in a rat acid aspiration lung injury model.

DESIGN

Prospective, controlled animal study.

SETTINGS

Research laboratory in a university setting.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Treatment with intratracheal perflubron or control mechanical ventilation beginning 30 mins after acid aspiration.

MEASUREMENTS AND MAIN RESULTS

PLV with perfluorocarbon compared with control ventilation resulted in significantly greater mean arterial blood pressures at 3 and 4 hrs and greater arterial Po2 at all times. Serum tumor necrosis factor-alpha at 2, 3, and 4 hrs was significantly less than that observed in the control group (4-hr values: 80+/-64 pg/mL vs. 658+/-688 pg/mL; p<.05), although no significant difference in tracheal fluid tumor necrosis factor-alpha concentrations (1425+/-1347 pg/mL vs. 2219+/-1933 pg/mL) was found.

CONCLUSION

We conclude that the effects of PLV with perfluorocarbon can extend beyond improvements in pulmonary physiology and that PLV may be beneficial in reducing systemic sequelae of acute lung injury and inflammation.

Advances in ventilatory support of the pediatric surgical patient

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

Newer ventilatory strategies

Over the past year a large number of innovations in mechanical ventilation have been evaluated. Three of the most exciting are non-invasive positive pressure ventilation, tracheal gas insufflation and partial liquid ventilation. Non-invasive positive pressure ventilation is now clearly a standard of care in the management of an acute exacerbation of chronic obstructive pulmonary disease. In addition, its use in other clinical settings is being actively explored. Tracheal gas insufflation appears to be a useful adjunct to mechanical ventilation for the management of carbon dioxide but requires manufacturer-designed devices for safe application. The effects of partial liquid ventilation on lung injury have been more clearly defined in the past year as well as approaches to provide gas ventilation during partial liquid ventilation.