The provision of space for implantable prosthetic lungs: A feasibility study

Wosornu, Joseph Lade (1972) The provision of space for implantable prosthetic lungs: A feasibility study. MD thesis, University of Glasgow.

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Knowledge and techniques in medicine and surgery have reached the point that replacement of organs which formerly seemed impossible has today become a reality. The progress in organ replacement has taken two directions. One has led to transplantation of viable organs from one person to another; the other has led to implantation of prosthetic, functioning organs composed entirely of non-living and inert materials. Although problems have arisen in the development of prosthetic organs, the difficulties are not insurmountable. The search is challenging and must continue. Bodell and his colleagues (1965) showed that it was feasible to implant- prosthetic lungs, but only in shortlived experiments. Peirce (1966 and 1967) described, in theory, an implantable prosthetic lung which permanently occupied the pleural cavity. This concept implies many unsolved problems and I have performed experiments designed to provide possible solutions to four of them. First, there was the difficulty of making the pleural cavity equal to the task of housing safely and permanently a functioning foreign body such as implantable prosthetic lung. In other words a special place must be provided for it: the pleural cavity must be relined and exteriorised effectively. Secondly, the route by which the prosthetic lung could receive air remained to be established. On the assumption that it was possible, anatomically, to reline and exteriorise the pleural cavity, the third thing to consider was whether, functionally, the animal could ventilate such a cavity with natural breathing; and the fourth thing was to quantify the ventilation, if any. The possible solution to the first problem which Peirce (1966) had suggested did not work. He suggested the pleural cavity could be lined with silicone 'skin'. Unfortunately, I found in initial experiments in five dogs that silicone 'skin' provoked much pleural effusion which needed protracted drainage. In one dog the effusion became infected. Parts of the chest wall, including the diaphragm, fused with silicone 'skin' and gave the required result, but developed into hard plaques. Dacron is not a soft implant material although it gives the sensation of softness. It cannot be employed where permanent softness is needed, because the tissue which grows into the interstices of Dacron is fibrous and contracts with time to become hard and fixed. These remarks apply equally to Teflon, Velour, and other plastic fabrics in current use (Braley 1970). I therefore abandoned the use of plastics and sought a different lining for the pleural cavity in the use of skin grafts. From a series of experiments in 11 dogs I drew conclusions which formed the basis of further studies. I found that free skin grafts would 'take' on normal pleural surfaces even when the skin was applied as capsules in which the hair-bearing surfaces had been enclosed. when grafted into the normal pleural space the skin capsules were associated with pleural effusion which accumulated in and remained confined to the lumen of the capsules provided they had been completely closed initially. An experimental preparation was required in which the pleural space was lined fully with skin grafts so that the cavity was effectively exteriorised. A readily reproducible technique was developed for doing this in a series of experiments in rats. I grafted closed capsules of skin into the left pleural space of 150 SPF rats and 132 (88 per cent) survived the next four weeks (P < 0.001). In these rats the skin capsules enlarged to occupy the left hemithorax as judged by serial chest X-ray films, and the rats thrived. The skin-lined hemithorax was put forward as a cavity which could house a prosthetic lung. The route by which the prosthetic lung would receive air was next established when the skin-lined hemithorax was opened to the exterior without embarrassing respiration in the lung on the opposite side. Thus 59 out of 75 rats so exposed survived (P < 0.00l). In this experimental preparation the two halves of the chest behaved as separate ventilating chambers in phase. The normal hemithorax received air through the trachea and the skin-lined hemithorax received air from an independent opening in the chest wall. The answer to the third problem was that the rats could ventilate the skin-lined hemithorax with natural breathing.however, and as the answer to the fourth problem, the skin-lined hemithorax was a poorly ventilated gas cavity compared with the normal hemithorax. Its mean tidal air (0.93+/- 0.06 ml) and its mean minute-ventilation (271.6+/- 1 24.4 ml/kg/min) were about half of normal (P < 0.00l). The arteria pH, PO2 and PCO2 in the test rats were not significantly different from normal. I concluded from these series of experiments that a readily reproducible technique could transform the hemithorax into a stable skin-lined cavity which could be opened to the exterior without embarrassing respiration in the contralateral lung in rats.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: D G Melrose
Keywords: Medicine, Biomedical engineering
Date of Award: 1972
Depositing User: Enlighten Team
Unique ID: glathesis:1972-73826
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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