The International Journal of Artificial Organs

Membrane Distillation (MD) is a technique that allows the extraction of water from aqueous solutions. The basic principle is that vapour, but not liquid water, can pass through hydrophobic micro-porous membranes, along a temperature gradient, with consequent separation of water from solutes. In this study we evaluated the possibility to utilise MD to extract water from Plasma Ultrafiltrate (PU) of patients with Chronic Renal Failure (CRF). The experiments were carried out in vitro by a hydro-phobic polypropylene hollow-fibre distillation module; PU was obtained by a CRF patient utilising a high permeability polisulphone membrane. The results show that water can be extracted by MD from PU of CRF subjects at a constant rate and that none of the substances analysed in PU was able to pass through the polypropilene membrane. In the future MD could integrate extra-corporeal blood purification techniques allowing the re-utilisation of plasmatic water thus ameliorating the treatment of uraemia.

Increase in systemic uric acid occurs in renal insufficiency, gout, chemotherapy, and other diseases. Dialysis can lower this metabolite but is expensive. The use of drugs can, sometime, result in side effects. Therefore, a suitable affordable method for this is required. In this article, for the first time, we report the use of artificial cells containing micro encapsulated genetically engineered E. Coli DH5 cells for lowering uric acid in vitro and in vivo. Results show that this novel approach has the ability to significantly lower uric acid from 84.80±3.40 mg/dl to 9.32±0.05 mg/dl in vitro and from the plasma of the experimental animals from the control levels of 71.00±27.49 mg/dl to 20.33+17.92 mg/dl in vivo. Continued daily oral administration maintained the plasma uric acid concentration of experimental uremic rats to the normal plasma uric acid level range during the entire test period.

Patients with mechanical heart valve prostheses show significantly enhanced numbers of HITS detected by transcranial Doppler ultrasound. In order to assess the origin of HITS formation, an in vitro study was set out to quantify valve induced microemboli for mechanical and bioprosthetic valves under various circulatory conditions by means of Ultrasound-Doppler-Sonography. At the same time the influence of CO₂ partial pressure on HITS rate vas investigated. It can be summarised that for mechanical heart valve prostheses a strong correlation exists between left ventricular dp/dt_max and the detected HITS rates. It was also demonstrated that a bioprosthesis generates significantly less HITS than a mechanical valve. The origin of HITS is gaseous since the tests were carried out using a cell-free filtered water-glycerol test fluid. The HITS rate could be increased by increasing the amount of dissolved gas within the test fluid. The results support the hypothesis that cavitation is the key factor in the appearance of gaseous microemboli at heart valve prostheses.

We studied the effects of a hybrid artificial liver support system we developed on dogs with hepatic failure. The system consisted of a multi-channel polyurethane foam packed-bed culture module, including primary dog hepatocyte spheroids.

Blood ammonia was well metabolized by 20 g hepatocytes, but the other functions such as glucose concentration, total bile acid concentration, and survival time required 30 g hepatocytes to improve conditions. We found that we should use a culture substratum that easily forms spheroids, and that an artificial liver module should be used as soon as possible after spheroid formation by hepatocytes in the module.

Fulminant hepatic failure is a rare, but often fatal complication of acute viral hepatitis. This condition, in absence of orthotopic liver transplantation (OLTx) surgery, is associated with a high mortality rate, despite the improvement of general intensive care.

Plasma-exchange (PEx) therapy has been long used to treat FHF, in particular by removing toxic substances and correcting the severe coagulopathy.

In this study we describe our experience with PEx treatment of FHF, beginning in 1982. Seventy patients affected with FHF due to various causes (HBV=40; cryptogenic/non-A, non-E=15; Amanita phalloides=8; other=7) were treated with PEx (altogether 348 sessions).

Overall survival rate, comprising patients undergoing OLTx, was 51%, a little higher than what we observed in patients (N=49) treated solely by PEx, i.e., 41%.

The best outcome predictor was FHF aetiology, owing to the good survival rate in patients with Amanita phalloides intoxication and the very poor prognosis of patients suffering from cryptogenic/non-A, non-E FHF. Moreover, the marked increase in prothrombin time and alpha-fetoprotein levels after 48 hours from admission was associated with a good prognosis, whereas the patient's age and coma grade were not clearly predictive of survival. Additionally, lymphocyte subpopulation, resulting in a CD4/CD8 ratio lower than 1.0 along with CD8 activation with HLA-DR strong expression, were associated with a high rate of mortality and morbidity.

Our data indicate that PEx therapy can improve survival in patients with sufficient residual capacity of liver regeneration. Moreover, the identification of certain prognostic factors may be useful for the rational planning of therapeutic strategy in FHF.

A voice-producing element has been developed to improve speech quality after laryngectomy. The design process started with the formulation of a list of requirements. The lip principle has the best potential for fulfilling the requirements. A numerical model was made to find the optimal geometry of an element based on the lip principle. Extensive in vitro tests were performed to check all requirements. For this a test set-up with realistic acoustic and aerodynamic properties was developed. Results show that the protruding lip length dominates fundamental frequency, cross-sectional area dominates flow resistance and relation between flow and fundamental frequency. Most requirements have been fullfilled; both for males and females a potentially good functioning prototype could be selected.

Clinical experiments will be performed to confirm the quality of the voice-producing prosthesis.