Whatever the ultimate decision on the permanence of the results of electric convulsive therapy, there can be no doubt as to the present widespread popularity of this treatment in psychiatry. To meet the big demand there have become available in the last few years a number of different convulsant machines, most of which are fairly efficient, but not one being free from defects when exposed to the test of practical application. Some are too heavy and cumbersome, most are liable to minor technical breakdowns, which are the source of much annoyance because they disrupt the hospital routine, one has a faulty time switch which has caused the writer a considerable amount of anxiety when it jammed and allowed the current to flow for about 5 seconds—the patient developed a prolonged period of post-convulsive apnoea, but fortunately came round eventually and suffered no lasting ill-effects. Most machines incorporate one or more instruments to measure the current or the patient's resistance. Neymann et al. have shown the inaccuracy of such simple instruments, and it is doubtful whether they serve any useful purpose. The ammeters are relics of the early days of this treatment, when we were not sure about the safety range of the current, and they were included in the circuit as an extra safeguard. Our experience over the last five years has taught us what currents can be safely used, and an efficient convulsant machine can now be designed whose maximum voltage and maximum time give an output which is well within the limits of safety. A knowledge of the current used is of interest while the machine is undergoing the initial tests, but once this period is over its evaluation, even by an accurate method, is of little academic interest, and a waste of time from the point of view of the practical psychiatrist. The resistance measurements, too, are unnecessary in practice. They were originally made in the hope that they would enable the dosage to be correctly adjusted so as always to ensure a convulsion. But we now know, as Grey Walter has recently pointed out, that the convulsive threshold varies from individual to individual by as much as 1,000 per cent., and since it is a value which can only be found by a method of trial and error, the resistance instruments are of little use. Moreover, no great harm is done if an underdose actually is given—all that happens is that the patient has a temporary period of unconsciousness, and after a short interval a higher dose can be given, which will produce the desired convulsion. It is true, of course, as Kalinowsky (1939) said, that resistance measurements enable one to ensure that the electrodes are making good contact with the patient's skin, but one feels that this is an elaborate and costly method of doing something which could be more easily and quickly accomplished by training the nursing staff always to clean the patient's skin thoroughly before applying the dampened electrodes.
Ferrier Lecture - Some observations on the cerebral cortex of man
