Artificial Lungs

Bioreactors are the apparatus in which practical biochemical reactions are performed, often with the use of enzymes and/or living cells. Bioreactors that use living cells are usually called fermentors, and specific aspects of these are discussed in Chapter 12. Ihe apparatus applied to waste water treatment using biochemical reactions is another example of a bioreactor. Even blood oxygenators, that is, artificial lungs as discussed in Chapter 15, can also be regarded as bioreactors. 

Medical applications of membranes Artificial kidneys Artificial lungs Controlled drug delivery Well-established processes. Still the focus of research to improve performance, for example, improving biocompatibility... 

In this chapter, the use of membranes in medical devices is reviewed briefly. In terms of total membrane area produced, medical applications are at least equivalent to all industrial membrane applications combined. In terms of dollar value of the products, the market is far larger. In spite of this, little communication between these two membrane areas has occurred over the years. Medical and industrial membrane developers each have their own journals, societies and meetings, and rarely look over the fence to see what the other is doing. This book cannot reverse 50 years of history, but every industrial membrane technologist should at least be aware of the main features of medical applications of membranes. Therefore, in this chapter, the three most important applications—hemodialysis (the artificial kidney), blood oxygenation (the artificial lung) and controlled release pharmaceuticals—are briefly reviewed. 

Figure 12 shows examples of the potential applications of substituted polyacetylenes studied, especially poly(4a). Oxygen enrichment (26-28, 31-33) is applicable to combustion furnaces, car engines, and respiration-aiding apparatus. The transport of oxygen dissolved in water (33, 34) can be applied to contact lenses and artificial lungs. Liquid-mixture separation (30,... 

Clowes GHA, Hopkins AL, and Neville WE. An artificial lung dependent upon diffusion of oxygen and carbon dioxide through plastic membranes. J. Thorac. Surg. 1956 32 630-637. 

ALEC = artificial lung expanding compound CLSE = calf lung surfactant extract protein B SP-C = surfactant protein C. Doses reported per milligram of phosphol... 

Lung. No implantable, artificial lung exists, and transplantation of this organ is relatively rare. Much work has been done, however, on extracorporeal oxygenators, which are used in over 100,000 operations each year. These oxygenators add fresh oxygen to the blood and permit removal of carbon dioxide. Several designs have... 

Wo Implantable, artificial lungs exist at this time hut some research has been done on polymeric membranes that could be used In such a device. Extracorporeal blood oxygenators are, however, used In excess of 100,000 times a year (l) and contain a thin, polymeric membrane thru which O2 and CO2 are exchanged. These oxygenators, which exist in several different styles are widely used In by-pass and other operations. The main polymers used are silicone rubber but poly(alkyIsulfones) and some others show promise (l, 50, 5l). 

Certainly with the modern emphasis on artificial body replacement parts and the success of implanted bits of hardware and assist devices for the heart (valves, heart bypass and pacemakers) and kidneys (renal dialysis), a substitute device for the natural lung should be considered. Artificial lungs are used daily for short-term (3- hours) heart-lung bypas in large, specialized health care centers. These are extracorporeal... 

Fortunately, artificial membrane lungs can function to achieve adequate gas exchange with lower surface areas because, while the natural lung receives inspired air containing only 21 oxygen, the membrane of the artificial lung sees 100% oxygen. 

A number of configurations are used for commercial membrane lungs those based on flat sheets are Bramson, 6.E.-Pierce, Lande-Edwards and Travenol. A modification of the flat sheet configuration is the Kolobow/Sci-Med spiral coil membrane lung. Hollow fiber membrane lungs are represented by the Dow and the Terumo artificial lungs. 

Since membrane lungs as extracorporeal devices are in wide use, thoughts have turned to an implantable artificial lung prosthesis based on membrane technology. Developing such a device with the adequate characteristics and long-term reliability is a much more difficult task than encountered with the extracorporeal device developed for intermittent use. However, a small prototype device made of porous Teflon has been fabricated and tested by Richardson and Galletti. ... 

Galletti, P.M., Artificial Lungs for Acute Respiratory Fai 1 ure, edited by Warren M. Zap>ol and Jesper (Jvist,... 

An artificial lung has been developed based upon principles of gas exchange with the blood exhibited in a natural lung (Thieme, 2001b). A balloon wrapped with hollow fibers is implanted in the vena cava by means of a catheter inserted in the leg (Figure 8.2.7). The balloon inflates and deflates as many as 300 times a minute. This causes blood to pump back and forth over the fibers, allowing oxygen to enter the blood and carbon dioxide to be removed. 

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