Pulmonary applications of perfluorochemical liquids: ventilation and beyond

Perfluorocarbon compounds as vehicles for pulmonary drug delivery

Drug delivery to the diseased lung is hindered by the buildup of fluid and shunting of blood flow away from the site of injury. The use of perfluorocarbon compounds (PFCs) as drug delivery vehicles has been proposed to overcome these obstacles. This drug delivery approach is based on the unique properties of PFCs. For example, PFCs can homogeneously fill the lung and recruit airways by replacing edematous fluid. Analogously, drugs administered with a PFC vehicle are expected to be homogeneously distributed throughout the lung. At the same time, intrapulmonary administration of the drug will achieve higher drug concentrations in the lung than conventional approaches, while reducing systemic exposure. Unfortunately, PFCs are poor solvents for typical drug molecules. To overcome this obstacle, several approaches, such as dispersions, prodrugs, solubilizing agents and (micro)emulsions, are under investigation to develop homogeneous PFC-drug mixtures suitable for intrapulmonary administration.

Towards improved artificial lungs through biocatalysis

Inefficient CO(2) removal due to limited diffusion represents a significant barrier in the development of artificial lungs and respiratory assist devices, which use hollow fiber membranes (HFMs) as the blood-gas interface and can require large blood-contacting membrane area. To offset the underlying diffusional challenge, "bioactive" HFMs that facilitate CO(2) diffusion were prepared via covalent immobilization of carbonic anhydrase (CA), an enzyme which catalyzes the conversion of bicarbonate in blood to CO(2), onto the surface of plasma-modified conventional HFMs. This study examines the impact of enzyme attachment on the diffusional properties and the rate of CO(2) removal of the bioactive membranes. Plasma deposition of surface reactive hydroxyls, to which CA could be attached, did not change gas permeance of the HFMs or generate membrane defects, as determined by scanning electron microscopy, when low plasma discharge power and short exposure times were employed. Cyanogen bromide activation of the surface hydroxyls and subsequent modification with CA resulted in near monolayer enzyme coverage (88%) on the membrane. The effect of increased plasma discharge power and exposure time on enzyme loading was negligible while gas permeance studies showed enzyme attachment did not impede CO(2) or O(2) diffusion. Furthermore, when employed in a model respiratory assist device, the bioactive membranes improved CO(2) removal rates by as much as 75% from physiological bicarbonate solutions with no enzyme leaching. These results demonstrate the potential of bioactive HFMs with immobilized CA to enhance CO(2) exchange in respiratory devices.

Effect of different ventilation modes with FC-77 on pulmonary inflammatory reaction in piglets after cardiopulmonary bypass

RATIONALE

Cardiopulmonary bypass (CPB) causes pulmonary inflammatory reaction. Liquid ventilation with perfluorocarbon has shown an anti-inflammatory effect on severely injured lungs. The aim of this study is to investigate the treatment effect of different ventilation modes with perfluorocarbon on pulmonary inflammatory reaction in piglets after CPB.

METHODS

After receiving CPB and subsequent infusion of lipopolysaccharide (1 microg/kg), 18 piglets were randomly treated with conventional gas ventilation, total liquid ventilation (TLV), or partial liquid ventilation (PLV) for 240 min. The lung tissue and blood samples were collected at the end of observation period. The pulmonary mRNA expressions and plasmatic concentrations of interleukin-6 (IL-6) and interleukin-8 (IL-8) were measured. Histological neutrophil count in lung parenchyma was performed.

RESULTS

Hemodynamics, PaCO2 and PH did not differ among groups during the observation period. Both TLV and PLV showed significantly improved oxygenation, reduced pulmonary mRNA expressions and plasmatic levels of IL-6 and IL-8, and decreased total neutrophil count in lung parenchyma when compared with conventional gas ventilation. Furthermore, TLV resulted in significantly better oxygenation, lower pulmonary mRNA expressions of IL-6 and IL-8, and less total neutrophil count when compared with PLV.

CONCLUSION

Both TLV and PLV improved oxygenation and reduced pulmonary inflammatory reaction in piglets after CPB, whereas TLV is more effective than PLV.

Islet isolation and transplantation outcomes of pancreas preserved with University of Wisconsin solution versus two-layer method using preoxygenated perfluorocarbon

BACKGROUND

Previous small clinical trials indicate that the two-layer method (TLM) for pancreas preservation improves islet isolation outcome. However, the effect of TLM has not been evaluated in large-scale study. In addition, a direct benefit of TLM on islet transplantation outcome has not been addressed in the setting of any randomized controlled trials.

METHODS

Between April 2003 and October 2005, human pancreata from brain-dead donors were preserved by TLM using preoxygenated perfluorocarbon (n = 75) or in University of Wisconsin (UW) solution (n = 91) prior to islet isolation. Islet isolation and transplantation outcomes were compared between the two groups.

RESULTS

We did not find any significant differences in adenosine triphosphate content in pancreatic tissue after preservation, pre and postpurification islet yields, in vitro insulin secretory function, or utilization ratio of transplantation between the two groups. Transplanted mass and functional viability of islet isolated from TLM-preserved pancreas were similar to those from UW-preserved pancreas. Patients receiving the TLM-islet or the UW-islet showed a marked decrease in insulin requirement after transplantation. However, no significant difference was observed in a decrease in insulin requirement between patients receiving the TLM-islet and the UW-islet.

CONCLUSIONS

No beneficial effect of TLM on islet isolation and transplantation outcomes was observed. Our findings bring into question the true merit of routine use of TLM prior to islet isolation.

Biochemistry, physiology, and complications of blood doping: facts and speculation

Competition is a natural part of human nature. Techniques and substances employed to enhance athletic performance and to achieve unfair success in sport have a long history, and there has been little knowledge or acceptance of potential harmful effects. Among doping practices, blood doping has become an integral part of endurance sport disciplines over the past decade. The definition of blood doping includes methods or substances administered for non-medical reasons to healthy athletes for improving aerobic performance. It includes all means aimed at producing an increased or more efficient mechanism of oxygen transport and delivery to peripheral tissues and muscles. The aim of this review is to discuss the biochemistry, physiology, and complications of blood doping and to provide an update on current antidoping policies.