After Hours; 19; Electronics Instrumentation for Cardiology

I'm Dr. E. M. Bluestone, professor of public administration at New York University, teaching in the special fields of public health, hospital administration and organized medical care generally. And it will be my privilege to serve as the chairman for this discussion on some of the applications of electronic instrumentation to medicine. For in the practice of medicine, electric current is a precious ally. There are times when our very lives depend on it. In every area of health and medical activity, electronic devices have become indispensable. And this holds true for all of the specialties in preventive, diagnostic and clinical and research medicine. It would of course be impossible to consider covering this field in its entirety. So during the next hour, my guests will discuss and illustrate the use of two important medical electronic devices.

Dr. Russell W. Browncotto, who was sitting at my right, director of the Cardio Pomenari Laboratory at St. Michael's Hospital in Newark, New Jersey, will describe his use of a new type of intra-cardiac catheter for the diagnosis of heart disease. And Dr. Wilkowitz, who was sitting at my left, will describe the engineering and construction of this new catheter. And later in the program, we'll show you a new instrument for measuring blood pressure. Dr. Wilkowitz is general manager of the Instrumentation Division for Galton Industries, located in the touch in New Jersey. Our presentation is not intended for the specialist in cardiology or in medical electronics, but it is designed to better acquaint graduate scientists and engineers with some of the work presently being done in medical instrumentation. For medical electronics, we have a field which crosses all disciplinary lines and professions. And exemplifies an instance wherein the physicist, the mathematician, the engineer and the

physician are all standing at the patient's side. Dr. Brancato, will you lead the discussion and go ahead? Thank you very much, Dr. Bluestone. It's usually necessary or at least incumbent upon the first speaker to state that it's a pleasure to serve on this panel. The pleasure is probably similar to that enjoyed by the first batter up in the World series. At this moment, 60 minutes is a rather tremendous abyss. And to make this abyss entertaining seems rather formidable indeed. Nonetheless, we'll try and see what we can do by some preliminary remarks, which I think are important to make the subject comprehensible to the graduate students and the general listener. We have chosen, or at least I have chosen, the subject of phonocardiography. This will serve as a model upon which we can construct and see how both the engineering sciences and medicine get together.

Now, the fact that medicine and engineering have gotten together at all is rather strange indeed. And I would say that less than 20 years ago, this alliance would not have been possible. At that time, we professed to be an art and engineers were claiming to be a science. The unholy alliance has been formed for better or for worse, and I don't think it's possible to back off at this late stage. Getting on to the subject of phonocardiography. Phonocardiography is simply the graphic registration of heart sounds. Now, what do we mean by heart sounds? Heart sounds are what the doctor perceives when he puts the time on its stethoscope to your chest and puts it over the area in which your heart lies. These sounds now were known to the Greeks several thousand years ago, but to the best of our knowledge that Greeks did not make any great diagnostic import. It was probably as late as 1628 or as early as 1628 that William Harvey and his classical monograph on the circulation paid some attention to heart sounds.

It's rather interesting to note that Harvey's contemporaries at this time thought that he was hearing sounds in his head rather than sounds being generated within the chest. The subject was rather quiescent, I would say, until the early 1800s. When, as his frequent in science, the thing that gives a study, a general and great impetus, is the development of a transducer. This transducer came about in a rather interesting way. One of the great giants of early French medicine, Lenek, had as a patient a young modest girl who felt rather embarrassed about his putting his ear to our chest. Lenek, being cognizant of this embarrassment, simply rolled up a tube of paper and used this to listen to our chest. Then he was thoroughly delighted and the fact that the sounds were much enhanced, he had never heard them so well. This early stethoscope then was the transducer that led the brilliant age of discovery

in phonocardiography or rather, at that stage, cardiac oscillation over the next hundred years. The next major development came in the early 1900s when William Eindhoven developed a galvanometer and recorded heart sounds. Later on in the 20s and 30s of this century, we had our galvanometric and a silimetric recordings of heart sounds. So we come then to this new era of phonocardiography, the new era was introduced as a result of scientific endeavor of World War II, at which time it was necessary to develop new and miniature microphone pickups that could be used in the detection of undersea craft. These microphones, miniature as they are, were finally incorporated in 1954 by some early Japanese workers, later in 1957 and more recently improvements as early, excuse me, as late as 1960.

These miniature microphones were incorporated in the tip of a cardiac catheter. Now, that brings us to the second area of discussion, the cardiac catheter. What do we mean by the cardiac catheter, moreover what do we mean by cardiac catheterization? In 1854, a Frenchman by the name of Chavo was able to stick a tube in the heart of an experimental animal and measure pressures. This brilliant assault upon the problem of understanding cardiac dynamics seemed to die of warning, with the exception of some remarkable work done in laboratories in England, Germany and France. No clinical application was made until 1929, when a rather inquisitive German by the name of Forsman found himself with a tube in his hand, he being a urologist, decided there must be other places to put this tube. He opened up a vein in his arm, inserted the tube in through the vein, walked several flights of stairs to the X-ray department, had an X-ray taken of his chest, and lo and

behold, the catheter was located within his cardiac silhouette. At that moment, probably the most formidable events in cardiology had been taken. This was probably Forsman's last major contribution, yet it was sufficiently major to see that in later years he received recognition by means of a Nobel Prize. The subject of cardiac catheterization truly was born when it was made clinically applicable by Andre Cornand in his group in the early 1940s. They made this technique a relatively safe and benign one, and enabled this technique to now be practiced the world over. This technique is something that I would like to illustrate to you by means of a film clip that we will currently see. This film clip will show you the actual passage of the catheter into a vein.

Before we get to the film clip, I would like to illustrate a little bit what we're talking about, excuse me, the film clip is now on. You see a catheter being held over the field. The catheter is now being inserted into the vein. The technician now advances the catheter very gently into this vein. The vein leads to the heart and the animated sequence, which will follow, will show how this catheter goes through the vein. Note now if you will, this is an animated sequence of the same vein we saw, there's the catheter going through the vein into one of the great vessels, cardiac chambers and out into the lung field. In the next sequence, which will follow this, you will see an actual demonstration of this catheter being passed during an x-ray visualization. Notice the catheter coming up from the lower left hand corner entering the heart silhouette

and now it takes the turn out through the pulmonary artery and into the lung field. So much for that. Now what is the gigantic significance of all of that? Let us look at the heart a little more closely. The heart, if you will, in engineering terms, is simply a two-cycle pump. This being cycle one, cycle two. Blood which returns from the body via the venous system is illustrated as coming in through this passageway. It enters into this right atrial chamber, then into a right ventricular chamber and then is passed to the lung where it becomes aerated and gives up its content of CO2. It then returns from the lungs into the left atrium, passes into this high pressure ventricular chamber and then is expressed into the aorta for general distribution into the body. Now in cardiac catheterization, we are able to pass this catheter that we saw in the animated

sequence, in through this vein, into the heart and out into the lung field, similarly recent techniques have enabled us to go in a retrograde fashion from an arterial system through the aorta, left ventricle, into the left atrium. This all looks very simple, but I will remind you that these techniques are highly complicated, but as complicated as they are, they are at generally benign, do not cause the patient any pain or any difficulty whatsoever. Now catheterization enables us to do several things. It enables us to draw samples of blood from the heart to measure pressures within the various chambers of the heart, and more recently, by the installation of radial peg die, we can actually follow the transit of this die through the heart and outline the cardiac silhouette and its various dynamic activities that are engendered. Now cardiac catheterization and more specifically, intercardiac sound is simply an extension

of this technique. This very same catheter that you saw in the animated sequence and in the x-ray sequence, being passed into the heart, now has a small microphone built into its tip. Thus we are for the first time able to locate this microphone at the very source in which the sound energy is being generated. This is most important because in cardiac oscillation up until now, we always have had to listen through chest wall, through interposition of lungs, and have had to deal with the random and very distribution of sound, the filtration that occurs through the chest wall. Now we can actually put this microphone at the very site of sound genesis, and the true test of a valid and worthwhile instrument is, does it give us any new knowledge? Can it add to our diagnostic elementarium? It does.

The next question any instrument has asked to do is, is it reliable? How does it perform? How does it stand up? And I think Dr. Bluestone, I'd like to turn it over to you so that Dr. Welkewitz couldn't get in and tell us a little bit about the construction and the development of this catheter. Well, thank you very much, Dr. Brancardo. As you spoke, I was thinking of my teachers in cardiology years ago, and I can only tell you that I had to learn with the hard way, I wish that you would have been around in those days. Dr. Welkewitz, suppose you pick it up from here. Thank you, Dr. Bluestone and Dr. Brancardo. As Dr. Brancardo pointed out, catheterization is a technique to obtain physical and chemical measurements from within the hard itself. And as he further pointed out, one of the physical measurements that has diagnostic value to the physician is the measurement of sounds inside the heart. What I would like to do tonight is demonstrate an intracardiac catheter microphone developed

at Golden Industries and discuss its design parameters, its general operational characteristics, and why it can be used satisfactorily inside a catheter to measure the sounds within the heart. What I would like to do is first demonstrate this catheter microphone and give you some idea of how it works and why it works. Dr. Brancardo is holding a catheter microphone, which I think you can all see. What a microphone Dr. Brancardo is holding is similar to the one that I will now demonstrate. One, two, three, one, two, three, this is an intracardiac catheter microphone. The sounds you hear are picked up through the microphone, both sides of this catheter. As you can see, despite its small size, this intracardiac microphone is able to pick up

the sounds through a throat transmission. They can very easily pick up the sounds inside the heart, since the sounds generated inside the heart are quite a bit louder than those we hear on the outside. The general design of this intracardiac catheter microphone is shown on this chart. What we see here is a chart, which shows that this is essentially a ceramic microphone. The ceramic microphone is a piezoelectric ceramic device, which generates a voltage when the ceramic is bent. The sound is incident on the diaphragm. The diaphragm moves, pushes on the pointer. This causes the ceramic to bend and generate a voltage. This voltage is transmitted through the conductors to any type of recording instrument, such as was shown on the opening of the program. The important parameters in such a microphone, as we saw from looking at the catheter, are that it be very small and that it be very sensitive.

Generally a catheter microphone must have a size no more than somewhere between 25,000 and 50,000. This greatly restricts the size available. It must have a sensitivity somewhere in the order of minus 120 dB. This will allow it to pick up the sounds within the heart and transmit them satisfactorily to the instruments. The general use for such a catheter microphone is for measuring the sounds within the heart and therefore the microphone must be able to pass satisfactorily through the blood vessels and therefore must be inert to the activities of the blood and to the general salt water condition within the blood. What I'd like to do now is show some of the other characteristics of the microphone and see why it can be used within the heart. Heart sounds of interest generally lie in a frequency range somewhere between 20 cycles

per second and perhaps as much as 2,000 cycles per second. So that the microphone we use must have a frequency response that allows us to pick up such sounds. As you can see on this chart, the microphone that we demonstrated has such a frequency response and has a flat response at least up to about 3,000 cycles per second. This is important to get adequate fidelity. Again, we need the sensitivity. The sensitivity the unit demonstrated was approximately minus 120 dB. More recent units using newest ceramic are as sensitive as perhaps minus 115 dB. The instrument must operate into a high electrical impedance because we have a unit with a very low capacitance. The capacitance should be as high as possible however the very small size certainly limits this.

Particularly unit we've discussed has a capacitance of about 800 micro-microfarrots. The next characteristic of interest in getting fidelity in the response or accurate reproduction of heart sounds beside the frequency response is the linearity. As you can see from this chart, the response is quite linear in the range of heart sounds that are present within the heart. We have here measurements of millivolts output out of the microphone against a relative heart sound level where the heart sound level was chosen to equal the levels that have been measured within the heart. Within this range the microphone is linear. So what do we have now? We have a little microphone. It's a very small microphone that can fit within a catheter. Its size is somewhere between 25 and 50,000s of an inch depending upon the catheter being used. We have a microphone that's sensitive. Its sensitivity is sufficient to easily record the heart sounds within the heart and give them good fidelity and output.

We have a unit that has good frequency response so that the doctor can get an accurate picture of the sounds within the heart. We have a unit with good linearity again to give fidelity in the presentation of the heart sounds. Basically this is what we need. For the microphone of this type I think that Dr. Brancato and other physicians in this field have been able to measure sounds within the heart so that they can utilize these sounds in their diagnosis of cardiac disorders and in their analysis of the workings of the heart. At this time I'd like to turn the meeting back to Dr. Bluestone so that Dr. Brancato can present some of his clinical findings with this instrument. I think it's wonderful for people like Dr. Brancato and Dr. Rocawicz to be working in an age of invention and discovery. I imagine that what you said here this evening with the gladdened heart of the pioneer

of cardiology Dr. McKenzie if he could come back to this world to us. But one of the things that occurs to me as you two gentlemen speak is that what a pity it is that you can't see more of the patients who are benefited by this kind of instrumentation. You see an occasional patient but you really should see all of them so that you can actually have the joy of accomplishment. I'm sure you have a good deal of it. Dr. Brancato how about it? Well I was just thinking as you were talking that I could Bluestone how all of this science which is mounted the tip of a catheter then finally employs a technique which has probably been known to plumbers for the last hundred-some odd years because I'm thinking that if one had to analogize about cardiac catheterization it's nothing more than the passage of a plumbers snake into matter of fact the plumbers has it even worse he isn't able to visualize the pipes he's passing his snake into and with x-ray techniques of course we can see just where this catheter is going.

I wish that Dr. Welcoicz one day would be able to get a catheter that had a brain of its own and would go where it's supposed to go be that as it may. I think before we actually go into some of the clinical material that I brought along and I hope this is not going to bore our audience I think it may be made somewhat interesting because this is where all of this finally pays off what does it do for a patient and is it worth going through all the effort of putting this into a patient. I think we ought to call somewhat the attention of the group that a great deal of attention and a great deal of effort has gone into the faithful registration and recording of this don't have the feeling that we had the scientific devices for the recording of this material at our back in call the instruments in the early forties were rather crude and over the last twenty years they have become rather refined and we are able to record

pressures very adequately we are able to take samples very adequately and the interesting thing or the important thing of course is what to do with this information. I'm sure those who tune in at the beginning of the program notice these large charts which are to the rear of us. Here you see just one method of registration this is the graphic method of registration these are simply photographs taken off the face of a oscilloscopic beam you see four or five traces there some with pressure some with sound some of the electric cardiogram more recently we have been utilizing a technique provided to us by the electric metadine company Farmingdale Long Island which we have a four channel tape unit. In other words we are able to put the entire catheterization on tape and play it back at will examine any sequence we want to rather than simply taking a small burst of film and having to be content with that we can now review the entire cardiac sequence and

this is a great advantage in much of the analysis that may follow. Now I have brought along two cases which I hope to clarify for you I'll use again my little chart and I must apologize to the doctors looking in on this while this may be engineeringly correct I say that it loses all the beauty and all of the wonders of the true human heart and this thing would never function like a heart with all of the science ever put into it but nonetheless it does serve as an idea of how the blood passes through the body. In the first instance we're about to discuss the lesion in this 28 year old man who came to the cardiac clinic at Saint Michael's hospital was thought to exist by an abnormal communication between this blood vessel and this blood vessel that is there was a communication or channel that existed abnormally between the two of them.

This would play some degree of embarrassment upon his gentleman's heart and would eventually lead to serious difficulties in later life. It's of interest to know that this man went through military duty, this murmur that was associated with his lesion wasn't heard and as a consequence he came to us because his private physician had heard of murmur. Now we felt the murmur located itself in a rather an abnormal position and thought it would be wisest to catheterize this man. In this instance since we thought we were dealing with a patent ductus arteriosus we said it would be rather nice to put a sound catheter in when the sound catheter reached the pulmonary artery we should hear the characteristic murmur in the main pulmonary artery a certain the left pulmonary artery and the diagnosis would be clenched. Well to our amazement all we found in the pulmonary artery this is the electrocardiogram this is the sound tracing all we found in the pulmonary artery was a short non-specific

systolic murmur. This told us that our original impression was wrong. We pulled the catheter back from the pulmonary artery into the right ventricle and now we found a markedly enhanced diastolic murmur. At this point we should have been totally aware of what was going on but that awaited for the next pullback when the catheter now was withdrawn into the right atrium. At this point we heard the characteristic gibson murmur which is a continuous or machine remurma. We knew right then on there that we had an abnormal communication between some arterial chamber and the right atrium. Cineangeography then was performed and we found out this man had an abnormal communication between his coronary artery and his right atrium. This saved the surgeon and the patient a good deal of embarrassment because had he gone for the original proposed operation that would have entailed one incision while the surgery that was required for this abnormal communication entailed another surgical procedure.

So here in the cardiac catheter told us immediately what the diagnosis was and what ancillary diagnostic procedure should be embarked upon. So much for that case. Now one of the more difficult cases is to that presents itself for diagnosis is a branch to diagnosis of the pulmonary artery. This diagnosis is usually not made because the following chart, which I will put here, where we simply dependent upon pressure relationships, this low pressure in the more distal portion of the pulmonary artery, transitioning into this higher pressure in the pulmonary artery. One might have thought that the catheter was wedged or stuck or blocked in some way and that all we did by pulling the catheter back was unblocked. And as a consequence we would have thought no more of this, but look what the sound

catheter tells us. The sound catheter tells us that in this blocked position there is the murmur, loud, clear and strong as it unblocks itself and comes into this chamber, the murmur disappears, which means then there must have been some constriction between this area of the pulmonary artery and this area and the murmur properly identified it. When we pull the sound catheter back from the right pulmonary artery and I must apologize later for this slide, we found no transition or any variation of pressure as we went from the main pulmonary artery to the right ventricle. The main pulmonary artery pressure, of course, this simply shows continuous right ventricular pressure. The main pulmonary artery pressure had a systolic peak equivalent to the right ventricular pressure seen illustrated. So we knew immediately then that we had branched a diagnosis of pulmonary artery and we then proceeded with more and other techniques to delineate this condition and to distinguish

just what had to be done by way of a surgical program for this young patient. So you see then in these two simple instances the cardiac catheter gave us information immediately. Now this is to be distinguished from information that will come late. Many times during cardiac catheterization certain procedures will be done. The samples or results of which need analysis. The cardiac catheter tells the operator right on the spot then and there what his problem is and what procedures he should take to further clarify this problem. I think then Dr. Bluestone this gives one a little idea that the cardiac catheter or cardiac sound catheter truly adds to our diagnostic government area and the future, of course, I hope we will get to and what extensions I believe this technique will have. So thank you very much for the time you will all be.

I know the answer to the question that I'm going to ask you now but for the sake of those that are listening to us perhaps I better ask it but I'm sure that if you were stricken with illness of this sort which I hope will never happen to you of course that you would want your medical attendance to use this kind of instrumentation on you wouldn't you. You would feel very unhappy if they didn't. I think every physician has to answer that question in his own mind and while you can answer it for yourself to say yes or no I think that every time you do a case such as this the whole mock of the procedure is were this patient, mine, near, and dear would I do it. And that is a question that I think invariably is answered yes before any procedure is undertaken so I can only say very definite yes. I know the answer.

Dr. Wilkowitz. Less bar we've discussed one possible engineering application in medicine we've discussed the design of very small microphones and the utilization of these very small microphones in a catheterization procedure. As is generally known there are very many applications of electronics and very many applications of engineering in medicine. What I'd like to do is touch on a somewhat broader application which also fits into our general field of cardiology and the use of electronics in cardiology. This is the field of monitoring. Monitoring is a coming field it's a field in which we would expect to have more and more electronic equipment and more and more sensing equipment utilized in medicine for providing more information to the physician and to such physicians as Dr. Brancato and Dr. Bluestone to aid them in their diagnosis and to aid them in the general care of patients.

As in the work on miniaturized microphones much of the work on physiological monitoring started with early military program work and space program work in which it was necessary to design equipment and to build equipment that could be used to monitor pilots and monitor other people in space programs under extreme conditions and under remote conditions. This led to the design of a wide variety of instrumentation and to the reduction of size of much instrumentation and therefore led to the development of units that could be used on patients and that could be used comfortably on patients and could be used under extreme conditions on patients. From this work we went into the area of patient monitoring and we did this work in conjunction with the National Institutes of Health and the original work we did was for patient monitoring

of a wide variety of parameters on post-operative patients. Some of the parameters that we originally monitored were blood oxygen saturation, blood pressure, temperature, electrocardiographs and sounds. What I'd like to do tonight is discuss one aspect of this work and this is the aspect relating to blood pressure measurement. As you all know blood pressure measurement is one of the major measurements that are made on a patient to sick and the present techniques utilize essentially a pump up technique where the cuff on an arm or a cuff on a finger is occluded by pumping up and the physician listens for caractgoth sounds and notes the presence or absence of these sounds and determines the blood pressure from the equivalent pressure in the cuff. This is a somewhat unwieldy technique and also does not lend itself easily to continuous

monitoring. As we'd like to do more and more monitoring and monitoring without a doctor present and monitoring without a nurse present, we felt the need to develop an automatic blood pressure monitoring system and one that could be utilized continuously and one that was comfortable enough so that a patient could wear it for quite an extended period of time. In post-operative monitoring, it's essential that one monitor the patient for quite a number of hours to determine how the patient recovers from the operation. What I'd like to do is first show you a few photographs of the blood pressure monitoring system and then go into a technical description of how it works. The first photograph shows the monitoring system on a patient and in this case what we're looking at is a monitor to monitor systolic blood pressure, diastolic blood pressure

and to monitor heart rate. This is sufficient for many cases, in some cases one would add temperature or breathing. The next photograph shows this situation in a little more detail. In this particular photograph one can see the sensors on the patient and the sensors in this case are entirely on the patient's finger. What we see on the patient's finger are an including cuff and a plethysmograph pickup and this is all and in the background we can see the readings being taken on this patient. Just by using a finger cuff and a one sensor pickup we're able to monitor systolic blood pressure, diastolic blood pressure and heart rate. We thus see that what we have is an instrument that can be worn comfortably and worn for quite an extended period of time without bothering the patient. Now that we see what the instrument looks like, what I'd like to do is go into a little

more detail on how it works. I'd like to first look at the first chart. Basically the first chart shows the logic of the whole system. As we've seen the most important portion of the system is the sensor or pickup and in this case the pickup measures the plethysmogram within the tip of the finger and the plethysmogram pickup is just placed on the finger and controls the electronics. The signal from the plethysmogram pickup is fed into an amplifier and this amplifier also performs a function of differentiating the signal. We will later see the advantage of doing that. The differentiated signal controls a logic. The logic is an electronic logic and controls the whole operation of the system. The purpose of the logic is threefold. What we have is that the logic puts out a signal when there is a pressure in the cuff. Here's the cuff that's equal to diastolic pressure.

It puts out this signal which then samples the pressure within the cuff and holds it reads it out on a meter. As the pressure in the cuff is increased further it puts out another signal when the pressure in the cuff is equal to systolic pressure. Again the signal samples the pressure in the cuff and holds it and reads it out. Finally in order to repeat the cycle the logic also vents the cuff and brings it down to no pressure so that the cuff pressure can then start building up again. We have a situation where the cuff pressure is built up and built up and built up and while it's being built up we sample diastolic pressure, systolic pressure and then we vent it. One of the problems in such a measurement is that sometimes a patient thrashes around in bed and there's quite a bit of noise picked up on the finger as it rubs against the bed. In order to avoid erroneous readings and certainly in a monitor an erroneous reading would be a very bad thing to have. We have a system whereby when there is excessive noise picked up we automatically vent the

cuff back down to no pressure and retain the previous readings. In this case then all the noise does is delay a reading but does not present incorrect readings. We thus see that this logic shows that we can control the various pneumatic operations and by our transistori circuit logic we provide signals to provide output readings of diastolic systolic pressure and we can also provide a signal of heart rate from the plethysmogram. Now with this in mind probably the best thing to do is to go into a little more detailed description of how the unit operates and for this I'll look at the next chart. Before we go into it it might be better to explain the physical basis that we are using in this particular measurement.

The physical basis we're using is as follows. The plethysmogram that's normally picked up on a finger has a notch in it. This is a diagrammatic presentation. You can see a plethysmogram pressure pick up and here you see a notch. This is a typical pickup. Now as the cuff is inflated on the finger what do we find? We find that as the pressure in the cuff builds up and when the pressure reaches diastolic this particular notch disappears. The physical basis that we're using to measure diastolic blood pressure is the disappearance of the dichotic notch when the cuff is pressurized sufficiently and when it disappears it looks something like this again diagrammatically. We see here that when we have sufficient pressure and here is the pressure rising in the cuff we lose the dichotic notch and this is the point at which we have diastolic pressure. Again as the pressure builds up when the whole plethysmogram disappears this is the point

at which we have systolic pressure. In other words when the pressure in the cuff is such that it makes the plethysmogram waveform disappear this is equal to the systolic pressure. So this is the principle that we're using. Now we can look at it a little better on these curves. Basically then if you remember our logic system we had a pneumatic system, we had a diastolic measuring system and a systolic measuring system. The pressure in the pneumatic system is rising linearly continuously. Here we see the pressure rising, rising, rising, it's rising at a rate of 5 millimeters a mercury per second and its control is controlled from the electronic logic. When it reaches the point where the waveform disappears or starts to disappear the notch waveform we want to look at it. Well to make the looking a little easier we differentiate that waveform so we get a very sharp pulse here and what we find is a diastolic pressure instead of worrying about this little change the complete secondary pulse disappears and it's much easier electronically

to look for the pulse disappearance. When this pulse disappears we send out a diastolic command signal which then clamps and holds the pressure that was in the cuff and this is the diastolic command signal. Again the pressure keeps rising from that point and we don't do anything about that and it rises at 5 millimeters a mercury per second. What do we find now? We finally reach a point where the plethysmogram disappears. Again we look at the differentiated signal because it's easier to make measurements from and it's easier to run control circuits from. When the plethysmogram disappears we send out a systolic command we clamp a systolic pressure and read out that pressure. When we have excessive motion and this is shown here diagrammatically we get a motion pick up very sharp one in the differentiated signal we send out a motion command and we vent. In addition in order to keep this cycle going time and time again right after systolic pressure we get a vent command and the cuff vents back to ambient pressure.

This allows the thing to keep running time after time. One complete cycle takes approximately 30 seconds so that we're getting essentially a complete measurement of diastolic and systolic blood pressure in 30 seconds and then it repeats every 30 seconds so we get a 30 second reading and one 30 seconds later and a units like this have been worn certainly for 24 hours in postoperative monitoring and have been worn comfortably and have allowed for continuous monitoring for that length of time. To look at the waveforms a little better and perhaps get a little better feeling for the situation we might look at this chart. In this particular chart we see the waveforms analyzed somewhat better. What are we looking at? We're looking at basically the plethysmogram, we're looking at the first derivative and in terms of our logic we clamp the first derivative and then use that to operate pulsing circuits in this case Schmitt-Trigger pulsing circuits.

What do we see? We'll look mostly for the diastolic because that's a much more difficult reading. This stolic is when this whole thing disappears and that's not too hard to see. Diastolic what do we have? We have this dichotic notch. If we look at the differentiated signal we have a main pulse and we have a second pulse. We have a main pulse and a second pulse. If we look at the clamped again we have a main pulse and a second pulse. As the pressure approaches diastolic and that's at this point the dichotic notch disappears. Again, when we look at this we no longer have much of a second pulse and in fact the clamped second pulse never comes back down to the baseline. This is what we use in our logic. When this pulse doesn't come back down to the baseline we fire a trigger circuit and we get a command signal. As you can see here when we're above diastolic we don't get any second pulse and we certainly don't get any return to the baseline.

This shows you in a little more detail what we're doing. We're looking for the disappearance of this small dichotic notch and when this disappears we say we have diastolic pressure. When the overall pletismogram disappears we say we have systolic pressure. The system has been utilized at the National Institutes of Health and has been shown to be a satisfactory method of monitoring blood pressure. What I'd like to point out is that basically we're monitoring the blood pressure not by the normal technique of listening for carotchof sounds but rather by the technique of analyzing the pletismogram pickups. One question that arises is does this system give the same answer as the other system? It certainly would not be useful to the physician if it didn't give the same answers for blood pressure. A number of checks on the system indicate that it does give the same answer as that measured by the physician by his normal techniques.

In addition incidentally it gives the same techniques the same answer as those obtained by using intracodiac pressure waves some of which are shown in the background charts here. The peak pressures and the dip pressures which are the systolic pressures and the diastolic pressures are the same pressure values that are measured with this particular instrument. What we see from such an instrument basically is that electronic technology is progressing. It has reached the point where electronic instruments and electronic sensors can be used to satisfactorily monitor patients in a hospital and to provide the information the physician needs for the further treatment of these patients. With this in mind I'd like to turn the program back to Dr. Blueston. Well thank you Dr. Wilkowitz and particularly for the compliment when you classified me

as a clinician alongside of Dr. Brancato. I am not a clinician. You see my work was the direction of a large scientific hospital where we would build and equip and organize and administer in order to make it possible for men like you to do your best work and that's how we get inventions and discoveries so that much credit I will accept but not for clinical medicine. I must say that I envy you both and I actually wish that both of you could have been working with me on my staff during my active years in hospital administration. Well now that we have heard these presentations by Dr. Brancato and Dr. Wilkowitz, perhaps we can discuss a few questions here.

I don't exactly have the soul of a poet though I think there is just a little bit of it in me but as you gentlemen spoke I couldn't help looking into the future and wondering where the knowledge of all these electrical impulses might lead us someday. For example I was thinking of the affairs of the heart and was wondering whether perhaps someday some young lady might set her cap for a young man, stick a feather in it which might serve as an antenna and by having received an advance a proper wavelength galvanized Mr. Wright into action. But I imagine gentlemen that that's a long way off and perhaps at the moment if I can ask you both to try and look into the immediate future let us see what lies ahead. I am aware of the fact from long experience that when you ask profits to look too far into the future that you get a lot of confusion.

So just a few years let's look ahead and where what is all this leading to all this instrumentation. Have we reached the peak of our efforts or is there more to expect and if so what might these things be if we can look into the future and try to identify them Dr. Berncardo of you any thoughts on the subject? Yes and most of them are polimical. I thought some of the subject are that is leading us into a changing complexion and medicine. This dialogue between engineers and doctors of course is far from a complete one. There's no doubt that in large academic centers where physicians who are engaged in active research and have the availability of electronic engineers on their staff and have department of electronic engineering.

This dialogue has certainly been resolved and is going along smoothly. But a certain paradoxical situation is developing. This is going along so smoothly that it's almost becoming a dialogue between a minority while the majority is on the outside looking in. In short what is the problem confronting a community hospital, a hospital that has no great affiliation with the department of electronics? Number one the communication isn't there. What engineers do you deal with, who do you learn to speak with, what to whom do you learn to speak, and where do you develop the vocabulary? I can say that I'm certainly at my present age not venerable or archaic but I had no introduction to medical electronics. I have returned to my school of origin and I find now that they are getting some superficial courses and some of the brighter young men are going into fields which give them a greater

orientation in this problem. But by and large the same type of physician is being ground out, who is being ground out at my time. That is someone who has no great familiarity. So we then are at the mercy of detail men who sell medical instruments and medical devices. This is not necessarily a bad thing. These people are certainly trained and I don't think there's any hox tourism. They try to do a good job but certainly they don't have the ability to give us basic understanding and basic knowledge and a way of extending ourselves by means of this equipment. There's one more polimical remark if you will. I hope I'm not getting too far of what making a plea for what is to come. There is a cost obstacle. It may be very nice that we can talk to engineers. But I wish to remind you, Dr. Bluestone, that as nice as the dialogue is the costs are getting higher and higher and the newer things are coming along so fast that you wonder

how are we going to stay with it? How are we going to keep up? And it becomes a little disheartening recently and I know for an example that some $800,000 was spent to develop a system of monitoring such as Dr. Welkewitz described. Now, I can tell you that $800,000 buys a lot of brains and buys a lot of equipment. But how does the average community hospital that is trying to do a good job keep up with this? Now, I suppose the answer is they do it by brains after all it was done that way in the beginning. But this is becoming a very, very difficult thing and I don't want to occupy the entire discussion with this. But I want to show you that this very nice relationship also has ramifications which are clouding the picture and making practice a little more difficult for all of us. On the other hand, I have never known medical research to go bankrupt to want a funds.

There's more money available today from medical research than ever before in the history of medicine. And I'm just a bit more optimistic about it, Dr. Berncardo than you are and I'm hoping that the required money will be available and that progress will be possible. You didn't question the possibilities of progress. No, no. You know, it was a problem of finance and I understand your point very well but I, as I say, I'm a bit more optimistic about it. What do you think, Dr. Welkewitz? My feeling is money will be made available and it has been in the past. And from our end, if the money is available, we expect very great things. We expect that there's a big future in instrumentation in medicine. In the areas of catheters that Dr. Berncardo was talking about, we can see our way clear to develop catheters that simultaneously measure sounds, pressures, blood oxygen, and electrocardiograms and perhaps even measure some of the chemical functions in the blood

or within one little catheter. This is certainly technically possible and can be done if there is sufficient money available. In the other area I talked about physiological monitoring, this is certainly a more expensive problem but again, if it can be done, we expect that complete physiological monitoring can be installed in hospitals to monitor many of the patients, operative patients, post-operative patients, even ward patients. We also feel that much of the information can be tied into computers and that the information in computers can be analyzed, rerun, checked and can be utilized to provide the physician with very many aids to diagnosis not presently available. We expect this to be the kind of future ingeniously in the medical electronics business. There are so many questions that I have in mind but I'm afraid we're going to have

to break this discussion off but I wonder, Dr. Berncardo, perhaps we have another minute, could you give us an idea as to how all these things that we've been talking about influence the work of the surgeon? What does the operating room look like? What can the surgeon do without you, without you people standing by? I think to be very brief and get in within this one minute, I think that the case material we're sending to the surgeon, I was certainly better worked up the surgeon, no, he's exactly what he's going to find, where he's going to find it and his course of procedure is established. How about it, Dr. Walgmann? Well, I envision in future surgery more and more technical people being present. The surgeon cannot do the operation and also operate the instruments and read all the instruments. From the engineering point of view, we would expect to have engineers present in surgery

of the future to read the... I'm afraid I'll have to, I hate to do this to you, Dr. Wilkowitz, but we must break this discussion off at this point, there's no time left, our time is up and I want to thank you for your contribution to this presentation. Dr. Russell M. Brown-Cotto, director of the Cardiopulmonary Laboratory, it's St. Michael's Hospital in Newark, New Jersey, and Dr. Walto Walgowitz, the general manager of the instrumentation division for galtan industries in the touch of New Jersey. You're given us excellent evidence that with electronics, there is greater hope for the conquest of destructive disease than ever before. I am Dr. E. M. Bluestone, Professor of Public Administration at New York University, that has been my pleasure to serve as Chairman for this edition of Science and Engineering Television Journal. Thank you.