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Filtration & fluid control Tubes transformed


Used to ventilate the middle ear and drain fluid or enable the delivery of antibiotics, tympanostomy tubes have remained largely unchanged in their design for 50 years or more, though they are known to have shortcomings. That is now changing thanks to a new study by Harvard’s Wyss Institute, the John A. Paulson School of Engineering and Applied Science, and the Massachusetts Eye and Ear (MEE) teaching hospital. Jim Banks speaks to MEE investigator Dr Aaron Remenschneider about a new approach to designing fluid-transporting implantable medical conduits.


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nfections of the middle ear – the air-filled space behind the eardrum that contains the tiny bones essential to hearing – are believed to affect more than 700 million people worldwide every year. Many require surgery, and the insertion of ear tubes is a common procedure. In the US, more than 600,000 children each year have tympanostomy tubes (TT) implanted. TTs are commonly used to treat otitis media, a middle ear disorder that frequently occurs in infants and children. It presents with earaches, impaired hearing, and fever, and if antibiotics or decongestants are ineffective, a myringotomy to create a slit in the tympanic membrane might be performed to aerate the middle ear and remove fluid. If the problem persists, insertion of a TT can create continuous aeration. Children are especially prone to ear infections – Harvard Medical School reports that 40% develop recurrent or chronic infections – creating risk of impaired hearing, speech and language delays, perforation of the eardrums, or even meningitis. The success of these operations is crucial, so one would think that any major problems with TTs would have been resolved through advances in technology, but this is not the case.


“The design of TTs is an important and popular conversation point and there is an impetus to innovate in this space,” says Dr Aaron Remenschneider, lecturer in head and neck surgery at Harvard Medical School and Investigator at Massachusetts Eye and Ear (MEE). “Many children have persistent ear infections or fluid behind the eardrum, and TTs provide a very good outcome for most by decreasing the frequency of infections, clearing fluid and ventilating the space behind the eardrum,” he adds. “But some patients have issues with TTs becoming blocked. They can end up with a hole in the eardrum and scarring.” Attending a presentation at a meeting of engineers, Remenschneider heard about the innovative materials science work at the Wyss Institute for Biologically Inspired Engineering at Harvard University. Wyss has focused on surface coatings to reduce algae and the adherence of molluscs to the boat hulls by impregnating them with a silicone oil. This provided the germ of an idea to impart non-stick properties to TTs.


Medical Device Developments / www.nsmedicaldevices.com


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