Blood, says Daedalus, gives a lot of trouble. The heart has the job of pumping it round the body all the time, and can fail or underperform in many ways. Replacement valves and pacemakers help out, as do complete replacement pumps. Sadly, artificial materials tend to encourage the blood to clot. Human hearts from donors are perhaps the best way to overcome this type of heart inadequacy, but have many problems of their own. Daedalus has a new idea.
Blood, he points out, is itself a magnetic fluid. It contains iron-loaded red blood cells, so it could be pumped around the body by a magnetic linear motor. In fact only the red cells really need to be moved, for they provide oxygen. But a fluid loaded with magnetic particles would be pumped as a whole, just as the heart pumps it. The best way of driving the blood around would use coils or magnetic linear motors attached to the arms or legs. Our limbs have central arteries taking blood outwards, and veins near the surface bringing it back in. The veins would be engaged by the motors; the arteries are too deep. One problem will be calibrating the whole system, to establish the correct rate of flow. Daedalus reckons that the carotid arteries in the neck, used as calibrators by the heart itself, could do this job. They will be given calibration coils to check that circulation is maintained. Indeed, the blood pressure could be held at a youthful 120/80 millimetres of mercury, even in very tense moments.
This arrangement has several advantages. No skin need be broken. Even a very inadequate heart can help the arrangement along. Indeed, all patients must have a functioning heart of some sort before inviting surgical help, and it would be a pity not to use it. Even a heart that can only maintain a resting body will still be doing most of the work needed most of the time. The carotid sensors will enable the magnetic accelerators to add just the extra capacity needed from moment to moment. Sadly, the motors on arms and legs will be heavy, even if DREADCO's engineers make the minimal use of copper and iron, and they will need a lot of power. The user will spend a great deal of time changing or recharging batteries. But thousands of customers will be very happy just to have a bit of extra heart-power available when needed. And surgeons will welcome any reduction in the long burden of seeking donors.
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Jones, D. Blood and iron. Nature 412, 695 (2001). https://doi.org/10.1038/35089179