About science; About engineering aspects of the cardiovascular system

This is about science produced by the California Institute of Technology in cooperation with station KPP C. Pasadena California. The programs are made available to the station by national educational radio. This program is about engineering aspects of the cardiovascular system. We host Dr. Peter Letterman and his guest Dr. Michael Taylor. Here now is Dr. Lawson. It is a common place these days that as scientific knowledge grows the lines between the different studies one science merges into the next. And knowledge gained in one field provides the key to unlock age old mysteries of another. As we discover more about the fundamental processes and the wonderful interconnection and linking of the skeins of knowledge and discovery. Our interest in aircraft and rockets has led to major developments in fluid mechanics. That is the study of the laws governing the flow and motion of liquids and gases either

around bodies or in tubes and recently this knowledge has been extended to the study of man's most basic fluid the blood in its life giving course through the human body. It seems unusual to find a medical doctor working in an engineering department but our guest today is an unusual doctor himself being both a Ph.D. and an M.D.. Dr. Michael Taylor our guest from the antipathies more commonly known as Australia turkies M.D. at the University of South Australia. After his in turn ship he lived for five years in England where he was a lecturer in physiology at St. Bartholomew's Hospital. He obtained his Ph.D. in physiology from the University of London and is now professor of physiology at the University of Sydney Australia. Dr. Taylor is currently working at the California Institute of direct technology where he is visiting professor of engineering science. Michael I must ask you

the first and most obvious question how did you as a doctor become interested in engineering. Well it was a long story. It began in fact when I was given the topic to work on for my M.D. this was a study of blood flow in inflammatory tissue repair tissue. And so I looked down the microscope for some months at the way small vessels repaired themselves and so on. And the more I looked at the small vessels the more I saw of the blood flow and the more interested I got in that rather than in what I was supposed to be doing. And you know to to understand the blood flow itself I found I had to do some mathematics and engineering and so on and that's how we began. That was the trouble Michael. That's a musing story one way seems to be diverted from one's main purpose into something else which frequently proves more interesting and more fruitful. You said that this was your thesis for an M.D.

That's a slightly unusual I think in American terms to do a thesis for a name D. Well I think it is the M.D. here is a degree on graduation and people practice on it. In Australia we follow the English path and there the graduate better medicine and better of surgery and the M.D. is a high degree and you get that for a thesis on research work it usually takes about about 3 years work to write a thesis for an M.D.. In fact I think there are regulations in Adelaide were that you couldn't even present a thesis for the M.D. until you'd been graduated for five years I think that's the that's the rule. This follows the same pattern as they do in England. As a matter of interest do the men who do their M.D. That's the thesis type of M.D. do they practice as doctors or do they normally go into research. Oh no no it's quite commonly. In fact I was intending to go into medical practice and I began on research with the with the idea that it would be good for me.

To see some of the basic work and then go back and be a proper doctor. But the science became so interesting that I gave up a proper doctoring and I've been doing research ever since. And so now you are performing as an improper doctor. That's right very rare indeed. Most Intriguing. Michael what exactly is this relationship between engineering and physiology which is your particular interest. Well it goes back a long way since people saw that shall we say mathematics and mathematical principles were useful in explaining astronomical phenomena. They then thought it might be useful to see where the mathematics and physics could explain some of the biological phenomena. And it all began really back at the end of the 17th century. It was quite a burst of activity then. The most famous name of course is Borelli who did a great deal of

mechanical examination of living structures the action of the hot flight of the swimming of mammals and so forth. And his book which was published about 16 86 that was a it's a mountainous picture book with all sorts of little creatures including a man in a submarine and all sorts of things like that so there was a lot of historical background to the parallel between engineering and biological problem particularly in circulation. And of course I had to reverse the analogy there is a considerable parallel today between Alvar Aust engineering systems and systems of the body they all have the common systematic quality upon them I imagine. Well yes I think once you get a luggage thing that has to be controlled and looked after all of our like shall we say high tension power system or the the water mines or something like this where you

have a very large assembly of bits and pieces then you become. You have some sort of parallel with a biological situation that you have a very complicated thing to control. Of course your remark about the bits and pieces and the complication is I mention the key word to this because one would expect that the body was a fabulously complicated system with a myriad of interactions between all the different little parts of each system. Well this is true yes there's a tremendous interdependence between one part of the body and another it's marvelous what you can do without that. On the other hand there is a tremendous organization and interdependence of one thing on another. In fact the body is such a complicated thing that it would seem to a layman absolutely impossible to attempt to make any model which represented the body in any way.

Well this requires a lot of care one has to simplify and abstract things I mean the same way is aeronautical engineers for instance will will simplify the shape of an airplane or the shape of a wing. You have to make certain abstractions and you have to be terribly careful about them. You can't just pluck them out of the air they have to be very carefully tied to the to the real situation. But of course without the abstractions you can do anything at all. You have to begin with a simple model and build up from there and hope for the best. Now when you talk about models Michael do you refer to actual little pumping systems for example to model the flow of the blood or do you refer to more abstract ideas or models. Well could be because generally by model I mean a mathematical one or a physical description of the system.

Generally in mathematical terms that one can do something with it. One may go on to construct a little working models of the circulation men would have pipes and pumps and elastic tubes and valves and so on but generally these won't do anything much that you couldn't have predicted from a mathematical description of the same thing. So much of your work is really concerned with attempting to write down equations which mathematically describe what you believe goes on and then trying to solve them which I suppose is an extremely difficult task. Well it varies some of the equations are relatively simple and have none solutions and others are perfectly horrible and have no standard solutions and have to be solved on the computer this is made a tremendous difference in the last. Well in my living memory which isn't a long one there's a tremendous difference between the way we went about problems in

London in 1955 and the way we go about them nowadays in nineteen sixty or sixty six now but sixty five ten years later problems that before in London we would do by hand with a desk machine that would take perhaps two or three days and now done in a few seconds on the big machines. And I just made a tremendous difference. I suppose equally sort of problems which would take theoretically thousands of man years can be handled with hardly any serious problems on a computer in a matter of days. Well this is this is true and the other thing is of course that with computers with the big machines no one will attempt problems that one wouldn't even begin on before. One can see elaborate systems and put them on the computer and get out the solution in perhaps an hour later say whereas before this would represent perhaps a hundred years work and I want to even begin on it. It's opened up a whole range of topics and complications of models that we

couldn't possibly envisage So we say a few years ago not even of attempted and of course not. Michael I must ask you the question which is asked always to embarrass theoreticians when you've solved the scratchings on a piece of paper. How do you know that they bear any relationship to life. This is where one has to go back a ways to experiment. And of course in this case one goes back to animal experiment and in fact I like to work about half and half half the time in the laboratory with animal experiments and half the time in the computing room with the with the computer. So that one's working backwards and forwards between these two realms if you like comparing one set of solutions with the animal situation and then trying to solve the complications of the rise in the animal work via the theoretical studies and so on backwards and forwards between the two.

In other words you will be steadily refining the input into your computer and the computer is then in turn giving you more information about what you should try to measure in the actual animal experiments that you're conducting. Well if that's the general idea. In fact there are a number of laboratories in this country where the computer solution is in fact used to run part of the animal experiment that they had to do together. And we have got to that stage in Sydney it but it may come it may come. So that you have the animal experiment actually coupled into the computer with a computer in a sense directing the solution. Michael what special problems are you working on currently What are the current problems of interest. Well the current problems of interest to me are not now exactly what I have been working on but I have over the last few years been working on the behavior of our trees particularly the description of blood

flow in trees and the elastic properties of our trees and the way that these elastic properties related to the design of the whole system. This is occupied a number of us for some years not only in Sydney but in other laboratories and in England and in Europe and in America. I mean in this country and. A good deal of work's been done on this over about the last 10 15 years. I take it that the arteries are nothing like what we normally think of as a pipe. I imagine that they are rather flexible spongy rough lumpy sort of tube says no not a bit of it they're very smooth there or they're flexible but they're not spongy they're quite they're quite solid. They're rather like a piece of hose pipe really. I don't know whether you have eight Irish do but in Irish do you one frequently encounters bits about three in the yellow gristly

rubbery pieces of material and they squeak when you eat them if you like that sort of thing. The trees are really quite quite solid pieces of tissue except that as you mentioned they're flexible defrosted is very important very very important. And what about the blood itself. Michael is that just like a sort of thick oil. Well it's not terribly sick it's about four times thicker than water as they say blood is thicker than water and they're absolutely right precisely for a time precisely four times well it depends where you measure it you see the blood is a very peculiar substance as good I once remarked but. It's got these lumps in it it's got cells in it and the fact that it is a suspension that is it's it's not just a homogeneous liquid of identical properties throughout it's got cells floating in it the red cells. And when these floated very narrow tubes

all sorts of interesting things happen and the sills move away just a little from the wall. And when that happens you have a thin sort of lubricating layer near the wall and this effectively makes the viscosity all the resistance to flow of the blood rather less in small tubes than it is in large tubes which is a rather peculiar situation. But it's very beneficial as far as the body is concerned because it reduces the amount of work that the heart has to do to pump blood through the tissues. In other words you are saying that the properties of blood make it easier to pump it through narrow tubes then through through white tubes. That's right. That is quite contrary to most engineering experience. Magine Well it's relatively easy to put it that way. Obviously the the wider the tube the less for a given flow the less pressure you have to apply to get flow through it.

But on the other hand in the body there are miles and miles and miles of very very small tubes for blood to be pumped through. And obviously the less work the heart has to do to pump through these tubes the happier everyone is and the reduction in viscosity is in fact almost to about half its value as measured in very large tubes and so the human body is. I suppose I'm others and various other people have always been telling us is a very beautifully designed system to minimize the work done by the hot in pumping the blood through this great coarse network of the body. Yes it's a very remarkable very remarkable system indeed and not only of course is it the is it remarkable in this funny business about the presence of cells in the blood but also the elastic properties of the of the arteries as it were to Tiriel system in such a way that the. The hot dogs rather less work than it would

otherwise have had to do. It's a very extraordinary state of affairs and it holds as far as we can see throughout all the the mammals that we have looked at. Birds are a little bit different but in the mammals there seems to be the case. How do birds differ. Michael Well they differ in having a different arrangement of elastic properties in the in their Tiriel system in the mammals there is a gradual transition. The vessels very near the hot quite distant symbol that is they can be inflated over quite large ranges without much much difficulty. The vessels near the periphery that is the vessels out in the limbs are much more rigid. Their walls are much different and there's a gradual transition between these two whereas in birds there's a sort of sudden transition. There is a very distant simple system of vessels inside the chest and the moment you leave the chest you arrive in very stiff vessels indeed and it's

a very peculiar state of affairs is the reason for that. I understood it all. You know it isn't at least not a not by me I wish I knew. There's maybe something about the way in which the circulation in birds. It has to be adjusted to the rapid changes in activity in flight and so full that I just and I there's something mysterious about that and I hope we'll find out one of these days when your interesting problem. I suppose Darwin would say that this is all tied into the evolution of the different species. Yes well I think you'd be right. The presumably an animal with and efficiently designed heart and cardiovascular system and will be a successful animal in the sense that it will catch its food or avoid being somebody else's food and one with a badly designed one will not be able to get away or will not be able to pursue its dinner at the swish and speed. This is this is what one argues anyway.

And so Michael you talked about the fascinating design of the arteries and the way that they are matched into the pumping properties of the heart. But these studies of the structure of the arteries in the flower of the blood. How can we use them directly in in medical research. Well what one aims to do here of course is to provide basic physiological knowledge of all biological knowledge and naturally in the practice of medicine. One has to know what the normal state of affairs is before one can go about trying to diagnose or to ascertain the causes of disease. One has to know what the normal properties are one has to know what are the important things to measure and one has to know how to go about measuring them and how to interpret the results when they're being measured.

So you must have the underlying physiological knowledge to begin with. This is the this is not the only reason for doing physiology but it's an important aspect of it. In other words in the simplest of terms. If you know exactly how the system works you can just go into it at one point and measure things and if they are not what they should be you can get a pretty good idea of what might be wrong and yeah right. Yes that's right and I suspect that you can also get a pretty good idea if something is wrong of how you should repair it. Well it certainly it's certainly important if you're going to take something out and replace it with something else or we say to know what it is you've taken out and how it should be replaced if a surgeon is replacing. An organization aim to be doing these days or about to do some mechanical device then obviously the mechanical device must match as far as possible the

biological device that's been removed if you're putting in an artificial heart. It must resemble as far as possible in its activity the organ which is being removed and will and serve a proper understanding of of its structure will enable us to design the artificial replacement so that they will work in the same way that the original ones did. Yes I think I think that it sounds a bit grand but that's the that's the general idea. Michael Ware what other directions is this sort of work leading. Well. I think first the obviously one wants to go on finding out more and more about biological systems anyway as I have one thing left hanging in the air here is the secularization in birds we really don't understand the biological basis which we say all the functions of the circulation in birds that have demanded the peculiar properties that they

have. Well that's just the sort of knowledge for its own sake. And the more and in general terms the more refined understanding is of the the basic physiology of the system the better will be diagnosis of diseases and their treatment of them. And I imagine that this understanding of the basic mechanisms we've we've come a long way in the matter would you still suggest that there's a great deal which remains completely not understood to tour. Well is a fair bit that isn't fully understood but I think at the moment. As far as the mechanics of the circulation is concerned we've got a fairly good idea of the the basic physical properties involved and I think there's there is still work to be done but I think the advances over the last 15 years or so have been very considerable under a

very rapid and well personally I think the field is running dry just a little bit on the dynamics. And in fact I'm not going to work very much on it much more and I'm proposing to move into another area. What do you fear is that. Well this is the this is the area of control control theory which has been widely developed over the last few years particularly in relation to aircraft control and guided missiles and satellites and all the rest of it. All these technological. Advances depend on an extremely sophisticated mathematical background of well look what looks like pure theory but in fact works as as a way of designing control systems. Fact I was reading in the newspaper now of flight control systems in Great

Britain which will land and take off aircraft completely unattained in complete dense fog. Either way you read that the paper has a very remarkable that this is the kind of control system that people are now building and you don't build those things without a very substantial mathematical theoretical basis. You couldn't build something like that just by trial and error. But your object Michael is not to control systems ports per se it is the control systems and their relation to the human body is you not. Yes well you see the whole body is full of them. We started off by saying how the many functions of the body were interrelated and in a sense many functions of the body. Controlled by many other functions and it's this interaction that amounts to a control system that I find very interesting particularly as regards the control of the circulation because the blood doesn't just go around at a

steady rate it's varying all the time in response to varying demands on the circulation exercise and gesture and so on. And how would you apply this knowledge of the control systems of the body to Madson. Well again I think it's more at the moment in the nature of trying to get some basic understanding of what's going on. It may come later on to have a practical application. Shall we say in such a situation as replacing the human heart that obviously it's no good just putting in a pump that will they will pump a constant volume of blood per minute. One would have to supply a pump that would adapt its function to the varying activities of the of the person. Otherwise he'd be. Will to do a very limited amount. In other words you were talking about designing a hot replacement heart in which not only is the heart matched to to model the pumping

of the original hock but its control system is also matched into the body system so that it pumps the right amount at the right time depending upon the needs of the individual. Well that's right this isn't the specific goal of what I'm doing but it is the sort of thing that could possibly flow from it. If anyone is going to replace the whole organs Well then I'll have to replace their control systems as well. And since we don't know what the control systems are in the loop all the necessary detail as I want to find out. Well I think that's a fascinating and most ambitious project. Michael I'd like to ask you a slightly unusual personal question. It's always so striking to us to have an M.D. working in engineering that I'd be interested in your views about whether it is easier for example for doctors that is medical doctors to learn about physics or for

physicists to teach themselves a little bit about medicine to enter into this fascinating field in which you are. Well that's a dynamite question really the I think it's probably easier although opinions will differ on this. I will say that in advance I think it's probably easier for a physicist or a mathematician to learn the necessary biology than it is for the medical man to learn the necessary mathematics and physics. The main thing is I think that whereas the mythical man is always acutely aware of his lack of knowledge of physics and mathematics the mathematician and the engineer I regret to say is not always so aware of his lack of knowledge of biology. There are some dangerous gaps in the end result. Well I think that's a very charmingly put put little comment Michael and I

must confess that I agree with you myself on this. And so we see yet another area in which the sciences relate how the tools of fluid mechanics and Applied Mathematics coupled with the vast arithmetical capacity of modern computers is leading us into increased understanding of the flow of our own life blood and how this knowledge can be used for the benefit of mankind. Thank you Michael. It's been a great pleasure. This was about science with host Dr. Peter Letterman and his guest Dr. Michael Taylor joined us for our next program when host Dr. Albert hims will lead a discussion about Africa about science is produced by the California Institute of Technology in cooperation with station KPP C. Pasadena California. The programs are made available to the station by national educational radio. This is the national educational radio network.