...that scientists are in the final stages of developing a fully artificial lung ?
An implantable artificial lung would allow a patient with advanced respiratory failure to move freely and to live at home. Consequently, an artificial lung - in a similar fashion to what dialysis does for the kidneys - could be a bridge to lung transplantation (Figure 1).
The primary role of the lungs is the extraction of oxygen from the environment and the elimination of carbon dioxide. This occurs when the lungs inflate and deflate, respectively; and ever since the Greek physician Galen (A.D. 175) used bellows to inflate the lungs of dead animals , scientists have attempted to replace the lung function with non-living, inert materials.
The first to report the successful inflation of the lungs by artificial means, which sustained life, was the Dutch physician Andreas Vesalius (1514-1564). He blew air into a tube of cane that had been implanted in an animal's trachea. By doing so, Vesalius was able to sustain the animal's life and observe the motions of the heart directly . Two centuries later, the British surgeon John Hunter (1728-1793) - building upon Vesalius' work - invented the first device for artificially assisted respiration. He built an apparatus with double-chambered bellows (one chamber inflated the lungs, the other deflated them) and used it successfully in dogs .
The Scottish physician John Dalziel is credited with the first effort to develop a fully automated respirator in 1832 . The principle behind this device was to cause subatmospheric pressures to be exerted outside of the thorax, thus allowing the more positive pressure of the atmosphere to inflate the lungs. A pair of bellows operated by a piston rod created the subatmospheric pressure . Over the next century, different variations of this apparatus were developed including the famous "iron lung" [5, 6]. These advances eventually evolved into the modern mechanical ventilator, a device that is now routinely used in intensive care units around the world. But since patients on mechanical ventilation have to be bedridden, intubated, and sedated - it follows that a mechanical ventilator is not an ideal artificial lung.
The concept behind an implantable lung stems from the first heart-lung machines developed for open heart surgery . It was proposed by Bodell et al. in 1965 as an implantable "third lung" . It consisted of a 20-inch-long polytetrafluoroethylene graft and was successfully tested in dogs and sheep. Since then, scientists have improved its design, its gas exchange capabilities, its biocompatibility, and the implantation techniques . Scientific collaborations eventually yielded a consortium formed by the University of Michigan and MC3 Corporation, which conceived the BioLung ® (Figure 2). This prototype has sustained a sheep's life for 30 days  and more recently, it allowed animals to engage in moderate exercise . These studies have moved the artificial lung closer to clinical trials.
This is important, because the only alternative available to treat non-reversible chronic lung disease is lung transplantation. But a significant percent of patients waiting for lung transplants die while waiting for a donor . The artificial lung is expected to improve and extend the life of those patients waiting to be transplanted. In consequence, an artificial lung is urgently needed; and with continued advances, it is expected to be available soon.
Author: Cristhiaan Ochoa
Chief Editor: Donna Cioffi, Ph.D. Feb. 2011
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