Prof William Mapleson: Physics in Anaesthesia | Association of Anaesthetists

Prof William Mapleson: Physics in Anaesthesia

Prof William Mapleson: Physics in Anaesthesia

Professor Emeritus William W Mapleson, has spent the last 60 years applying physics and maths to research and teaching in Anaesthesia in the Department of Anaesthetics in Cardiff.

After studying physics at the University of Durham, Prof Mapleson spent three years working in radar for the Royal Air Force, before returning to Durham to complete a PhD. In this interview, he discusses his work in anaesthesia and the research post in Cardiff he accepted, initally thinking it would last for five years. He is best-known for his work in rebreathing and ventilation, and for the five anaesthetic systems that bear his name.


I was fortunate to have a very good teacher for physics, mathematics and he was a career master, so it was an enormous benefit to me. When he first asked me in the sixth form ‘Well what do you want to be when you leave school? I was thinking of some sort of engineering after I got over wanting to be a steam train driver. In effect, he said ‘You will go to Durham and read physics’ and he was absolutely right, that’s just what I needed.

I went to Durham in 1944. I got delay of national service, though not to do a full degree, I was a radio bursar. They gave me a bursary of £120 a year to cover the lodging in the college and fees. We had it cushey in those days, compared to now. That was to be a two-year course of physics with a bias towards radio communication. But within the first week the professor called us into the lecture room to say ‘decision has been taken by the government that you could complete your full three-year BSc in physics and then go on and do your national service. So I really had the best of both worlds, my timing was perfect. And the degree I got was a BSc in physics, 1947. And then I had to go straight from there into the national service, for two years.

National Service

For some reason I tried the Navy first for a short service commission, which was a three year commitment instead of two but I think you got paid a bit better by opting for that. But they decided they didn’t want me so I had to go to the RAF and apply to be considered for a commission Fortunately I managed to scrape through the officer training course and in the RAF I learnt all about radar, which became very useful later on because the radio at the university was all sine wave electronics whereas radar was all pulse electronics, quite a different thing.

I attended a course on radar and I was then posted to teach that course but after preparing my lectures for it, they decided that: ‘we are not going to do that course anymore for UK air officers but we’re going to run a course for overseas air force.’ So eventually I did get to teach one course of overseas air force officers; about half of them from Norway and about half from India and a couple from Greece, all speaking very good English. It was a very interesting experience, very useful practice at lecturing and explaining complicated ideas to people not familiar with them, which stood me in good stead for explaining the principles of physics to anaesthetists.

I was stationed partly Debden in Essex, but mostly Yatesbury in Wiltshire. And that was splendid because my other obsession is theatre and they had a lovely small hangar that had been converted into a lovely theatre, it even had a Royal Box. An uncle of mine was an opera singer with Carl Rosa and so he put on wonderful operas when he was stationed there during the war … and then in the officer’s mess there was a frieze all the way around the wall of cartoons of officers including my uncle John who was immediately recognisable.

I’d taken a precaution before leaving Durham in ’47 to go and see my professor and to say goodbye and to thank him for what he had done for me. And so at that time I was thinking seriously of going on the stage professionally; not acting but stage management and lighting. But having done the work with radar in the RAF, I thought that this is all rather interesting and I wondered if I could do a PhD. So I made some enquiries and I seemed to be favourably received and then out of the blue I received a telegram that said ‘Come to the Durham on such and such a date for research studentship.’ So I thought well what’s that? Anyway I went and it appeared that this was a studentship for financial support that would support me through doing a PhD. So I told them a little bit about what I had learnt about radar and they decided that they’d like to take me on, so that was how I got on to do the PhD in Atmospheric Electricity.


The title of the thesis was “point discharge in atmospheric electricity” and most people would have heard of St. Elmo’s fire, which I believe can be seen in the high mountains of the Alps in a thunderstorm. And that occurs in thunderstorms because there are very intense electric fields between the ground and clouds, but even in fair-weather, there is an electric field throughout the atmosphere that the surface of the Earth is something like 100 volts per meter so that if you could pick up a voltage probe one metre above the surface of the Earth and another at the Earth, completely isolated, you could measure the voltage without draining it, you’d get 100 metres. So I built that machine to measure the electric field, then to get point discharge under those conditions, you have to raise your point to 50, 100 or 200 metres, which I did by means of a meteorological balloon filled with hydrogen, 365 cubic feet cylinders of hydrogen to fill the balloon. And then record the discharge current and the field and look for relationships between them.

“Wanted in the Anaesthetics Department in Cardiff, someone with a wide knowledge of physics, physiology or pharmacology…”

There were other PhD researchers; there was a chap, Wally Whitlock and I think the paper on the machine for measuring the electric field, I think that was a joint paper with him. There was another chap whose name I forget who was studying “Transition from laminar to turbulent flow in water” and he was injecting tiny drops of oil into the water and then using early electronic flash to take rapid sequence photographs so that he could say the path followed by each little drop of oil in the water, gradually increasing the flow to see how the transition occurred. At the time, I had no idea that it would be very relevant to anaesthesia.

I was getting towards the end of the PhD when my supervisor said:

‘Well what are you going to do when you’ve finished?’

‘Oh, well I hadn’t really thought about it much, maybe some sort of medical application in physics will be interesting.’

‘There’s something on the notice board, something in Cardiff, go and have a look.’

So I went and had a look and it said:

“Wanted in the Anaesthetics Department in Cardiff, someone with a wide knowledge of physics, physiology or pharmacology”.

“I said ‘I think it would do for five years’… that was fifty-eight years ago. I still go in twice a week”

So I thought ‘Well that should do to get some interviewing experience.’ I went and they seemed to like me even though almost every question they should ask me about ‘Have you done something’ or ‘Do you know anything about something else?’ I said ‘No, no sorry’. But I think he was impressed by the fact that I was a pure researcher and I think my rivals were more applied physics and he fancied the fundamental, probably, in the mould of Epstein in Oxford. So I was offered the job but to my acute embarrassment I had to make the first real decision of my life. Prior to that, I’d done what I was told, so my supervisor advised me ‘Remember, you’re interviewing them just as much as they’re interviewing you.’ We had it very cushy in those days so I said ‘Well I’d like to think about it overnight’, so I talked to my supervisor the next day and decided that ‘Well yes’ and I wrote to them and said ‘I think it would do for five years’. I started in Wales in 1952, October, and that was now fifty-eight years ago. I officially retired nineteen years ago now but I still go in twice a week.

Breathing Circuits & Research

The first project was to measure the relaxant action of Gallamine triethiodide, which was the first synthetic muscle relaxant for curare, and at that time it was thought important to have a relaxant that we had control over and weren’t dependant on importation. The way Mushin wanted it done was to stimulate the ulna nerve at the wrist to produce contractions of the short muscles of the thumb. So we needed a stimulator and a means of recording the force of the contractions. And Ken Hillard built up a device in consultation with me for recording the contractions, and Mushin had had a grant from the Association to buy a stimulator. And I said ‘Well, £250… you could buy an awful lot of electronic equipment for that. I could make one for you’. So I used the £250 to equip an electronics lab and buy some components and we made our own stimulator which could do what in those days were much more fancy things than the commercial machines. But it did the job. And the results were published in Anaesthesia.

“I had to have some means of distinguishing the breathing circuits, so I just labelled them A, B, C, D, E”

When I was waiting for volunteers for my real research Mushin came in and drew out, initially, four semi-closed breathing systems. He said ‘have a look at these Bill, and see if you can work out what conditions are required to eliminate or minimise breathing.’ That was a big worry at that time. And then later on I added the Jackson Rees modification of Ayre’sT-piece so if instead of a leak in the bag, you have a valve by the bag, then that becomes just a variation on the others so that gave the five systems. He didn’t tell me anything about it, he just drew the diagrams and said ‘See if you can find out how they work.’ Well I had to have some means of distinguishing them so I just labelled them A, B, C, D, E and as a result seemed to become the only person to make his reputation in anaesthesia on the strength of his knowledge of the alphabet. But I’m repeatedly accused of classifying the system. But just labelling them A, B, C, D is not a classification it’s just a nomenclature, it’s just a means of distinguishing them. There was a chap from South Africa, Donald Miller, who did classify them into afferent reservoir and efferent reservoir systems.

“I seem to have become the only person to make his reputation in anaesthesia on the strength of his knowledge of the alphabet”

The major thing of that time was automatic ventilators in the early days, there were automatic ventilation of the lungs which John Nunn of the department irreverently called The Puffing Bible. And that was in the days when automatic ventilation was a novelty and people were designing ventilation from all sorts of bits and pieces, anything that would make gas go forward under pressure for a time and then shut off and allow expiration, any possible mechanism that could do that was tried out. In fact in Cardiff we tried making one out of a milking machine by just reversing the action so instead of sucking intermittently it blew intermittently. I don’t think we ever got round to trying it on a patient but we established that the principle was possible.

But the fun in that time was looking at the mechanism, and Ken Hillard would draw out a good drawing, showing the relationship between the parts and how they moved, and I’m studying that, and worked out how all these different ventilators began to work in terms of flow and pressure and volume characteristics, which was something that I was very much familiar with in relation to valve characteristics in the days before transistors. You could hold books full of valve characteristics, how they related, how the current flow related to the voltages on the various electrodes. That led to the classification of flow generators and pressure generators and pressure-, volume- and time-cycling.

“In Cardiff we tried making a ventilator out of a milking machine”

I wrote a couple of chapters, one developing these concepts and explaining them, and then another saying the application of those concepts in general terms, and then for each ventilator there is a description of how it worked in mechanical terms and then I did a functional analysis. So aiming to make the ventilators more directly comparable with one with another, and that went on to a second edition in which I did some lab testing of some ventilators to show how well the actual performance matched what I had divined theoretically from the mechanical structure. And then the third edition included some more new ventilators but I don’t think we did any further testing. We did start on a fourth edition during Mushin’s lifetime, he was very keen to have another go and it usually came down to Mike Harmer and I working on that. And we had done accounts of perhaps ten or twelve ventilators or something like that but there were two problems; one was that at that stage Mike decided that he really must get on and finish his MD if he was going to have any hopes of getting the Chair when it became available and also we were losing heart a bit because instead of ventilators being a whole variety of mechanical gadgets, they were all becoming basically a device that would drive gas forward and then a lot of electronics, controlling how it did it so that if you worked out the functional analysis of a ventilator as its supplied now, next week they may change the software and do something entirely different.

It was just a little pot boiler theoretical thing while I was waiting to do my real research. Nobody remembers my real research at all. That was the measurement of the relaxant action.

I’ve had about one hundred peer review research publications and if I include everything like abstracts and letters to the editor, items in the church parish magazine and one or two themes in minor computer journals, I think I’ve just got up to two hundred and fifty.

“Nobody remembers my real research at all…”

I suppose I’m most proud of the original breathing system paper because of the notoriety it achieved. Other than that I think the theoretical papers and perhaps the experimental ones on uptake and distribution of volatile anaesthetic and even, I’ve done some on pethidine with one research assistant, Norman Davis and did quite a lot on Propofol in association with Barbara Weaver, the veterinary anaesthetist in Bristol. The basic modelling depends on the physiology of the subject and the solubility of the different agents in the various organs and blood in the body. Humans were quantified back in 1960. And when methoxyfluorane came in, the first incarnation of that model was the electronic model, the electronic arrangement passive network of capacitors and resistors; capacitors representing the storage capacity of the organs of the body to store anaesthetic and the resistors, the ability of the ventilation to transfer gas anaesthetic from mouth to lungs, and the conductance from the lungs to the capacitors representing the tissues to be proportional to the transporting ability of blood flow to the areas (organs and tissues).

That immediately translated to a new electronic analogue, which was fine for me because I understand electronics but for anaesthetists, at least at that time… I think these days most anaesthetists would be happy to make sense of the electronic analogue, but at the time it was not appropriate for that, and so I converted it to a water analogue which has proved invaluable for teaching. They’ve never existed physically; it’s always been diagrams, now it’s been a video.

Honours and Awards

I think that the first sort of real thrill came from getting my DSc in Durham in 1973. I thought that ok PhD’s are becoming two a penny now but yes that’s really something a bit special so I took the family with me to receive the degree but then in the same sort of way there was the Honorary Membership of the Association when I retired in 1991 and then some years later, Honorary Fellow of the Royal College of Anaesthetists. They had given me the faculty medal sometime ago and also the Dudley Buxton medal that was very nice.

The Faculty Medal and the gold medal from the Association I keep hidden in a draw to bring out for the Association and Royal College dinners each year. [Also] the Clover medal and the Elias Berg medal which was for the Clover lecture that I gave to the Royal College, [and I] was virtually asked to repeat as the Elias Berg Memorial lecture in New York. And they gave me a plant but they spelt my name wrong.

“The Anaesthetic Research Society decided they wanted to do a Mapleson medal. That was wonderful!”

The Anaesthetic Research Society decided they wanted to do a Mapleson medal. That was wonderful! I think that the awarding is done by the Committee or the Council of the Anaesthetic Research Society – and if I’m there at the time they will usually ask me to present it which is rather nice.

I was a founder member of the Anaesthetic Research Society. John Nunn and Ronny Walmer and one or two others and probably Dave Smith from the Research Department of Anaesthetics on the sixth floor of the Royal College of Surgeons, paid a visit to Cardiff once and I had had a letter from them about this proposal to form an anaesthetic research group and I’d been thinking about it and John Nunn talked to me about it during that visit and I said “well yes, I think I would like to join”, and he said can I take that as a verbal agreement to come and I said yes indeed and I never looked back.

Family Life

When I got to Cardiff I was still finishing writing my PhD and analysing the results so each lunchtime, I would go over to the Medical Statistics Department and use their electrical calculator which could add, subtract, multiply and divide! So I would churn away at that each lunchtime till I crunched all the observations and got that written up. I wanted an amateur theatre group to join in Cardiff and it soon became evident that Everyman Theatre was for one to join because they were doing the sort of plays that I was interested in. And one of the plays that they were doing, The Drunkard, a Victorian Miller drama and as the lady playing the lead female role was miming all her parts: ‘This loaf of bread, this jug of wine’. I thought this is a really avant garde company that don’t bother with props, certainly the one I will join when I finish my thesis. And when I joined it I saw the lady and I complimented her on this and she said oh that wasn’t planned, its just my stage manager let me down that night. This is a very remarkable woman if she can do that on the spur of the moment, I must get to know her better and for the first time in my life, I looked to see if there was a ring on her finger and there wasn’t, and so that was Doreen. So we married in ’54.

We had a daughter, Jenny, in 1955 and then, Doreen was an only child, and she said we mustn’t have an only child. So we tried for a second child and we tried and we tried and we did all the various tricks that are supposed to help. Eventually Doreen said this is not going to happen. Then, of course we had one that was Roger in 1963.

“Giving kids a sound beginning on maths is excellent work for a physicist to do…”

I did persuade Jenny to go to Durham and read Physics, I don’t know whether she’s quite forgiven me yet because her boyfriend went to Hull.

But I realise now that I was probably being too prescriptive but the sciences and maths, she was good at. And then she soon after got married, as soon as she had finished her degree, fairly soon started a family and then once that was established, she decided to go in for teaching, but only in a primary school. And I thought well that’s a bit of a waste of a physics degree, a primary school, but later I thought well I don’t know because if she’s giving those kids a sound beginning on maths then that’s excellent work for a physicist to do because if a child once gets left behind in maths, they’ll virtually never catch up.

“I’ve had a wonderful time and have lived a charmed life”

Quite a few papers that reached a fairly advanced stage, other things got crowded in and I felt like I better get on with those. I’ve got quite a few unfinished papers, which are not worth finishing now because they wouldn’t be of great interest. I would have liked to have been able to do more on updating the distribution of pharmacokinetics in general. I didn’t do badly; I had excellent support from Mushin, but there was no one, none of the anaesthetists in the department were especially keen on that. But I think I might’ve done more in that way if there had been someone like that. But I’m not complaining about it, I’ve had a wonderful time and have lived a charmed life.

Further reading