Touching Lives - March 2006
Improving speech valves
It is hard to imagine the frustration of suddenly being unable to speak, but this is the unfortunate reality faced by thousands of throat cancer patients every year. As many as 50 per cent of people with throat cancer may need their voice box removed, which includes the vocal cords, meaning that air can no longer pass from their lungs into the throat and mouth to aid speech.
The procedure for removing the voice box is called a laryngectomy, and involves a permanent opening being made in the front of the neck to enable the patient to breathe. To help people regain their voices, a small silicone valve is installed in the back of the throat, which diverts air from the lungs into the throat so that speech can be formed.
So far so good, but there is one big drawback. The silicone valves only last on average three months, and in some patients they may wear out in a matter of weeks. The procedure for replacing them can be uncomfortable, and it is expensive — the 16,500 or so replacements that take place every year in the UK cost the NHS just less than £10 million.
In March 2002, Action Medical Research awarded Stephen Ell, consultant surgeon at Hull Royal Infirmary, and Dr Mike Fagan, a biomedical engineer at the Centre for Medical Engineering and Technology at Hull University, a grant of almost £68,000 to look at why the valves fail after such a short period of time, and how the current design could be improved to make them last longer.
The team created an artificial throat which could simulate food being swallowed. Inside the throat they placed a number of silicone discs, and as the simulated food passed down the throat, a film of bacteria, known as a ‘biofilm’, began to develop on the discs, just as it would on the surface of a valve in a real human throat. The team were then able to analyse the biofilm to see which elements were leading to the erosion of the silicone valves.
At the University, Dr Fagan used advanced computer modelling techniques to identify the weaknesses in the current design. Mr Ell explains, “In the same way that car and aeroplane designs are tested, we were able to enter the design details of the current valve into the programme and determine how its operation was affected by the biofilm. But more importantly we were able to optimise the valve design in the computer so that it became more tolerant to the biofilm, and therefore less likely to fail.”
The findings have led the team to identify ways in which the life-span of the current valves could be improved, and have given them vital clues as to how a long-lasting valve might function. They plan to use the computer system to check the performance of any prototypes before testing them in patients.
Alongside improving valve design, the team has also been looking at the possibility of developing a computer system that could replicate speech, restoring a patient’s own voice and superseding valves altogether. “It’s a long way off,” says Mr Ell, “and relies a lot on advances in computer technology, but it would make a huge difference. Men tend to develop more acceptable valved speech than women because their voices are low-pitched and fairly gruff. But looking ahead, and particularly with the increase in the number of women smokers, computer-aided speech might be more of a requirement in years to come.”
Mr Ell concludes, “The funding from Action Medical Research has been a real boost to our work. We’ve clarified our understanding of the problem with speech valve failure and we’re now able to think in more advanced terms about how we can help these patients.”