Engineering saving lives Part 2
The last post told how customers, scientists and engineers interact. This is the story of the engineer.
The surgeon and the scientist asked the design engineers, Team Consulting, to design and make a machine to do the job in the real world. This was to become the OrganOx® metra™. The finances meant the prototype must be operating in 9 months.
Stuart Kay, Project Manager, led the engineers’ design team. There was a lot to learn about the problem.
“[The customer] had some outline user and product requirements,” Stuart told The Lad. “ and knew what the basic fluid circuit needed to be like, there were a lot of verifiable requirements that needed to be un-earthed in order to ensure that [the customer and designers] had a common understanding of the end goal.”
To avoid problems later the Project Manager always writes a Design Specification. This records all the many dimensions, operating features and power requirements.
In existing transplant technology, the liver sits at 4˚C without nutrition or oxygenation for up to 12hrs. Some livers have features that mean, although they are otherwise perfectly usable, they cannot be cooled like that and still be re-used. Cooling can itself sometimes damage a healthy liver; and, during its journey, certainly no one can tell how well it is surviving.
The new technology keeps the liver at body-heat, ‘feeds’ it and supplies it with oxygen. This alows more livers to be usable; they last for up to twice as long and can be checked for survival during the journey. In simple terms, the plan is to keep the liver beavering away outside the body doing what livers do inside the body, while it was being moved. That way we can even measure that it is doing a digestive job properly.
Any design of a machine using body fluids has special problems. Blood can clot on surfaces or be damaged in a pump. Everything must be kept absolutely sterile. These problems are not new though: some have been overcome before by designers of heart-lung and dialysis machines. So they save time and money by using existing, proven pumps, valves and pipework. All wetted parts are single use and disposable to keep everything sterile.
The blood circulating has to have quite a lot of oxygen as it is used up by the liver. Normal, steel, bottles of compressed oxygen are too heavy. What’s to do? Extract it from the air as we go along-that’s what. The existing, brilliant, engineering idea of a Concentrator leads to a much lighter assembly. That will be another post soon.
The machine has to feed, preserve and monitor the health of the liver. Firstly, there is the rather beefy power for the pumps and heater; and, secondly, the delicate listening and sampling systems checking the performance of the liver. The electronic system engineers have to take great design care that the great, bouncy, power supply does not electronically deafen and interfere with the sensors.
Then there is the system engineering. The engineer cannot just plan to have all the components bolted together. She has to think clearly and deeply about how to get them to work together. Standard parts may need ‘tuning’. As a very simple example, think of a system full of liquid that has a standard temperature-measuring switch for a standard heater. If that system contains a transplant organ, a simple switch off at the right temperature could result the organ temperature overshooting or undershooting. The engineer may have to arrange always to switch off a little ‘early’ or a little ‘late’. Only this way can the possibility of damage to the transplant organ be avoided.
This kit does not sit lazily in a laboratory; it has got to be moved safely from hospital to hospital. There must be not the slightest damage either to the system or the payload. It all has to fit into one trolley with a protective shell. They designed an elegant transport and protection frame which is lowered into a neat, tubular chassis with castors.
There are other functions too. The hospital technicians need to boot the machine simply and absolutely reliably. There are several possible power supplies: on-board battery or a 12v vehicle power supply or by hospital mains power. Clinicians can monitor an on-board screen continuously for pressures, flows, temperature, blood gases, and pH and bile production?
The designer has to decide how best to manufacture machine parts, and, vitally, how the technicians can service the machine to high standards. As Stuart wrote to The Lad, “The only way to achieve this is with a dedicated and highly skilled engineering and design team, and we had one. We hit the 9 months target, and the system worked beautifully.”
All in all, this is a marvellous piece of engineering. If this stuff appeals, remember that you, female or male, could join such a team.
The Lad is grateful to Stuart Kay, Project Manager and Team Consulting for their informative help. Top notch engineers.
Engineering is one of the three drivers advancing the human race. This blog describes professional engineering in the real world as it is not well served by the current media. An engineer is posting: not a ‘scientist’. Its target is the career seeker and also the general public.