Reliability and medical equipment One of the many advantages that might accrue from doctors and engineers getting together would be an opportunity to explain to the medical profession, particularly those consultants involved with medical equipment, the true meaning of reliability. In the engineering world a guarantee of reliability for a definite period of time has been an accepted part of the bill of sale for many years. In fact it is often said flippantly that in the motor accessory field, where articles such as car batteries have a standard guarantee of two years, the problem is not to guarantee the two years but to ensure failure in the third. This sort of reliability is obviously based on science, not wishful thinking. In the medical profession such reliability is unheard of and not understood. One could cite many examples. In the operating theatre surgeons for many years used a system of lighting to illuminate the inside of the chest or the bladder, the reliability of which would have incensed even a ten year old. When the surgeon peered into the bronchoscope or cytoscope and there was no light, he would complain, and the theatre sister would reply that it was working a minute ago: a standard which would make any potential electric light user revert to gas. A more current example is when a small bit of equipment becomes lost inside a patient, its having come adrift from a piece of equipment inserted into the patient during an emergency, possibly the end of a suction apparatus used to remove dangerou’s liquids from the body. ‘It did not come off when I tested it’ is the excuse or plea of the surgeon or theatre sister. And if this is not accepted, then it is for the patient t o sue for negligence. But does the whole health care industry have to start its reliability tests, rules and legal decision de novo? Cannot it learn from other professions? Must it still have the historical bogey of charity behind it, when the patient should be grateful for anything and if something goes wrong through a lack of responsibility that is just too bad for the patient? Nowadays many sick patients are nursed in intensive care units where machines are used t o breathe for them as well as to monitor their general medical condition. Machines are used because the health care industry cannot afford to pay the number of qualified people, at least five or six, necessary to look after one sick patient continuously. So it is essential that the machines become more reliable. All equipment has a finite life and reliability is related to this. A machine can only be predicted t o be safe if it is tested within its expected life and then nearer the end, the greater the predictability of failure. In this issue Mr Eames puts the facts clearly. The science of predicting reliability emerged from the problem of handling atomic energy. Now it is freely available to all and there is no problem, but, as is pointed out, medicine appears to show little interest.

Downloaded from eim.sagepub.com at University of Leeds on June 4, 2016

30

Engineering in Medicine

@ IMechE 1976