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SEMIAUTOMATIC ELECTROCARDIOGRAPHIC MONITORING
501
clinical measles, while not preventing the persistence of measles virus genomic material in certain cells. The abberrant immune response then acts as a selective pressure encouraging the evolution of a non-lytic infection, perhaps with an incomplete or defective " measles virus. This could explain the requirement for trypsinisation and co-cultivation for recovery of the measles virus from the brains of s.s.l’.E. "
Methods and Devices SEMIAUTOMATIC ELECTROCARDIOGRAPHIC MONITORING
J. TINKER Hospital
Hammersmith
1
patients. We suggest that this phenomenon represents the first step in the pathogenesis of S.S.P.E. Measles infection early in life, however, is fairly common and is thus not a sufficient explanation. In Chicago alone no fewer than 400 cases of measles have occurred under the age of 1 year in the past four years. 12Yet our series and all other reported series demonstrate a higher rate of S.S.P.E. in rural populations. The well-documented excess of measles patients, taken together with the geographical case distribution, is compatible with a zoonotic disease. Conversely, the paucity of urban cases might represent a protective mechanism, such as frequent and repeated reexposure to measles, operative in areas of high population density. We doubt this, because the pattern of S.S.P.E. occurrence among rural males has not changed since the late 1950s when the Brazilian and Belgium studies were conducted, although the use of measles vaccine since 1964 has appreciably reduced the exposure-rate to this agent. The second step in our hypothesis involves a zoonotic infection as the precipitating event. This secondary agent is probably an animal virus with low infectivity which penetrates those with maximum contact-males in rural areas. The natural host could be a fowl or farm animal or, alternatively, animals such as dogs or rats whose flora and diseaseexposure patterns differ from those of their urban
counterparts.
P. STINTON and Royal Postgraduate Medical London W.12
S. P. VAHL
Engineering
School,
J. C. VICKERY Imperial College,
in Medicine Laboratory, London S.W.7
CONTINUOUS patient-monitoring systems generate a lot of data, but this information is largely valueless unless it can be effectively assimilated by the clinician. The electrocardiogram (E.C.G.) is difficult to evaluate when it is moving across an oscilloscope screen. If the record is written out continuously on to paper, the significance of any one part of it tends to be submerged by the vast total output. There is no general agreement about which are the most significant variables which may be derived from the continuous E.C.G. record, so it is desirable to keep the data in some form in which future detailed analysis for research purposes is possible. In order to present the data to the clinician in an acceptable form and to store it for future reference, we have developed a two-stage system. The first stage is " on-line " from the patient to his attendants in the intensive-care unit, and the second is " off-line " to the computer in the laboratory. The essential feature of both parts of the system is that the equipment itself is designed to perform some relatively crude pattern recognition on the waveform and that only those parts of the record which are considered abnormal are presented for further evaluation. ON-LINE SYSTEM
The on-line system consists of a multichannel tape recorder with a 14-second time-delay between record and " reproduce heads, an instantaneous " heart-rate meter
injury and subsequent disease state the simultaneous infection of brain cells with both agents. From existing data it seems that the animal virus may be the papova-like agent observed in tissue-culture cells inoculated with S.S.P.E. brain material. With the development of a tissueculture system for identifying the papovavirus-like agent, ecological studies carried out where cases of S.S.P.E. have occurred could provide the critical The actual cell
depend, then,
on
information. Requests for reprints should be addressed to J. A. B., Epidemiology Branch, Collaborative and Field Research, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Building 36 Room 4A-05, Bethesda, Maryland 20014. REFERENCES 1.
Horta-Barbosa, L., Fuccillo, D. A., Sever, J. L., Zeman, W. Nature, Lond. 1969, 221, 974. 2. Payne, F. E., Baublis, J. V., Itakashi, H. H. New Engl. J. Med. 1969, 281, 585. 3. Katz, S. L. ibid. p. 615. 4. Horta-Barbosa, L., Fuccillo, D. A., Hamilton, R., Traub, R., Ley, A., Sever, J. L. Proc. Soc. exp. Biol. Med. 1970, 134, 17. 5. Koprowski, H., Barbanti-Brodano, G., Katz, M. Nature, Lond. 1970, 225, 1045. 6. Barbanti-Brodano, G., Oyanagi, S., Katz, M., Koprowski, H. Proc. Soc. exp. Biol. Med. 1970, 134, 230. 7. Huang, A. S., Baltimore, D. Nature, Lond. 1970, 226, 325. 8. Jabbour, J. T., Sever, J. L., Horta-Barbosa, L. Presented at the 97th annual meeting of the American Public Health Association, Philadelphia, Pennsylvania, November, 1969.
Fig. 1-On-line system.
which indicates the rate between successive heart beats, and a pen recorder with some electronically operated controls. To simplify the location of specific sections of record, the tape has coded time markers recorded on one track. The equipment is connected to the conventional bedside E.C.G. amplifier and oscilloscope. DR.
BRODY,
DR. DETELS:
REFERENCES—continued
Jabbour, J. T., Duenas, D. A., Krebs, H., Sever, J. L., HortaBarbosa, L. Presented in part at World Congress of Neurology, New York City, 1969, and the American Public Health Association, Philadelphia, Pennsylvania, November, 1969. 10. Canal, N., Torck, P. J. neurol. Sci. 1964, 1, 380. 11. Canelas, H. M., Lefevre, A. B., Tognola, W. A., Fonesca, L. C., Juliao, O. F., de Assis, J. L., de Jorge, F. B., Xavier-Lima, A. Archos Neuropsiquiat., S. Paulo, 1967, 25, 255. 12. Nelson, K. E. Personal communication. 9.
502 The
input fiom the E.c.G. amplifier is fed to the rateand to the tape recorder simultaneously (fig. 1); the output of the tape recorder being connected to the pen recorder which in turn is started and stopped by the meter
rate-meter.
If the instantaneous heart-rate falls outside certain rate-meter triggers the control circuits which, after a 7-second delay, start the pen recorder which runs for 14 seconds. As the pen recorder is connected to the tape recorder, the output of which is delayed fourteen seconds from its input, the trace which is written on to paper consists of a seven-second portion of record immediately preceding the aberrant beat, then the irregular beat itself, then a further seven-second " portion of normal record. Accompanying the E.c.G. are any other physiological signals that might be required and a trace of the code from the timing track, which accurately locates the piece of data both in time and in position on the magnetic tape. In practice, this system is very convenient; the volume of written data is greatly reduced and the clinician has his attention drawn only to those parts in which he is interested.
predefined limits, the
Both the on-line and the off-line parts of the monitoring system have been designed to allow pre-editing by the machinery and to give the clinician the opportunity of overriding and validating the process himself if required. It has been found in practice that it is much easier to obtain reliable information from large quantities of data by this semiautomatic method than by either fully manual or fully automatic procedures. We thank the Medical Research Council for the use of the computer facilities in the engineering and medicine laboratory, at Imperial College, and the British Heart Foundation for a grant to purchase the magnetic tape recorder. S. P. V. is supported by a grant from the Leverhulme Foundation. Requests for reprints should be addressed to J. T.
"
OFF-LINE SYSTEM
The foregoing recording procedure also serves as the basis for producing a data bank " of E.C.G. signals suitable for detailed analysis. For such data to have value, they must be edited to remove the artefacts. The off-line svstem is a comDuter-based Drocedure for oerformins this "
PNEUMATIC INTERMITTENT-COMPRESSION LEGGING SIMULATING CALF-MUSCLE PUMP
J. S. CALNAN
J. J. PFLUG C.
J. MILLS
Department of Plastic
and Reconstructive Surgery, and Medical Research Council Cardiovascular Unit, Royal Postgraduate Medical School, London W.12
A CENTURY ago, Virchowconcluded that there were three factors responsible for venous thrombosis-stasis of blood-flow, hypercoagulability of blood, and vessel intimal damage. Modern opinion agrees. Anticoagulants have been moderately successful for therapy,2 but in prophylaxis for surgery they have been found to be unmanageable. Surgeons have, therefore, concentrated on methods for preventing venous stasis. Early patient mobilisation after operations has reduced the incidence of fatal pulmonary emboli,3 but this level is unacceptably high. The use of the 125I-labelled fibrinogen technique 4,5 has made it clear that venous thrombosis in the legs is much more prevalent than had previously been thought. Venous return from the legs depends on three pumping mechanisms-the vis-a-tergo from the heart, the thoracic and abdominal pressure during respiration, and the soleal muscle sinuses in the calf during walking. All three are less 1. 2. 3. 4.
Virchow, R. L. K. Thrombose and Emboli. Frankfurt, Sevitt, S., Gallagher, N. Br. J. Surg. 1961, 48, 473.
1856.
Murley, R. S. Ann. R. Coll. Surg. 1950, 6, 283. Negus, D., Pinto, D. J., Le Quesne, L. P., Brown, N., Chapman, M. Br. J. Surg. 1968, 55, 835. 5. Flanc, C., Kakkar, V. V., Clarke, M. B. ibid. p. 742.
Fig. 2-Off-line system.
equipment consists of a digital computer with input/output facilities, including a special terminal which enables the computer to display stored information on an oscilloscope screen. Part of this terminal is a light-operated pen " which allows the user to interact with the display and to modify the contents of the computer memory (fig. 2). A programme has been developed to write recorded E.C.G. data on to digital magnetic tape and to enable the user to replay this tape on to the graphical output oscillofreeze " the display at any time to look scope. He can at any portion of the data in more detail. This programme can detect the position of each heart beat and marks this position on the oscilloscope screen. Should the pro-
task. The
"
"
gramme make an error, it will be evident to the user who, using the light pen, can correct it. The presence of the time markers on those parts of the record which have been written out on paper greatly simplifies the procedure, since it again draws attention to sections containing abnormalities. The final output from the system is a digital magnetic tape free from artefact with interesting features of the record marked and available for manual or automatic
analysis.
Fig. 1-pneumatic legging.
clinical measles, while not preventing the persistence of measles virus genomic material in certain cells. The abberrant immune response then acts as a selective pressure encouraging the evolution of a non-lytic infection, perhaps with an incomplete or defective " measles virus. This could explain the requirement for trypsinisation and co-cultivation for recovery of the measles virus from the brains of s.s.l’.E. "
Methods and Devices SEMIAUTOMATIC ELECTROCARDIOGRAPHIC MONITORING
J. TINKER Hospital
Hammersmith
1
patients. We suggest that this phenomenon represents the first step in the pathogenesis of S.S.P.E. Measles infection early in life, however, is fairly common and is thus not a sufficient explanation. In Chicago alone no fewer than 400 cases of measles have occurred under the age of 1 year in the past four years. 12Yet our series and all other reported series demonstrate a higher rate of S.S.P.E. in rural populations. The well-documented excess of measles patients, taken together with the geographical case distribution, is compatible with a zoonotic disease. Conversely, the paucity of urban cases might represent a protective mechanism, such as frequent and repeated reexposure to measles, operative in areas of high population density. We doubt this, because the pattern of S.S.P.E. occurrence among rural males has not changed since the late 1950s when the Brazilian and Belgium studies were conducted, although the use of measles vaccine since 1964 has appreciably reduced the exposure-rate to this agent. The second step in our hypothesis involves a zoonotic infection as the precipitating event. This secondary agent is probably an animal virus with low infectivity which penetrates those with maximum contact-males in rural areas. The natural host could be a fowl or farm animal or, alternatively, animals such as dogs or rats whose flora and diseaseexposure patterns differ from those of their urban
counterparts.
P. STINTON and Royal Postgraduate Medical London W.12
S. P. VAHL
Engineering
School,
J. C. VICKERY Imperial College,
in Medicine Laboratory, London S.W.7
CONTINUOUS patient-monitoring systems generate a lot of data, but this information is largely valueless unless it can be effectively assimilated by the clinician. The electrocardiogram (E.C.G.) is difficult to evaluate when it is moving across an oscilloscope screen. If the record is written out continuously on to paper, the significance of any one part of it tends to be submerged by the vast total output. There is no general agreement about which are the most significant variables which may be derived from the continuous E.C.G. record, so it is desirable to keep the data in some form in which future detailed analysis for research purposes is possible. In order to present the data to the clinician in an acceptable form and to store it for future reference, we have developed a two-stage system. The first stage is " on-line " from the patient to his attendants in the intensive-care unit, and the second is " off-line " to the computer in the laboratory. The essential feature of both parts of the system is that the equipment itself is designed to perform some relatively crude pattern recognition on the waveform and that only those parts of the record which are considered abnormal are presented for further evaluation. ON-LINE SYSTEM
The on-line system consists of a multichannel tape recorder with a 14-second time-delay between record and " reproduce heads, an instantaneous " heart-rate meter
injury and subsequent disease state the simultaneous infection of brain cells with both agents. From existing data it seems that the animal virus may be the papova-like agent observed in tissue-culture cells inoculated with S.S.P.E. brain material. With the development of a tissueculture system for identifying the papovavirus-like agent, ecological studies carried out where cases of S.S.P.E. have occurred could provide the critical The actual cell
depend, then,
on
information. Requests for reprints should be addressed to J. A. B., Epidemiology Branch, Collaborative and Field Research, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Building 36 Room 4A-05, Bethesda, Maryland 20014. REFERENCES 1.
Horta-Barbosa, L., Fuccillo, D. A., Sever, J. L., Zeman, W. Nature, Lond. 1969, 221, 974. 2. Payne, F. E., Baublis, J. V., Itakashi, H. H. New Engl. J. Med. 1969, 281, 585. 3. Katz, S. L. ibid. p. 615. 4. Horta-Barbosa, L., Fuccillo, D. A., Hamilton, R., Traub, R., Ley, A., Sever, J. L. Proc. Soc. exp. Biol. Med. 1970, 134, 17. 5. Koprowski, H., Barbanti-Brodano, G., Katz, M. Nature, Lond. 1970, 225, 1045. 6. Barbanti-Brodano, G., Oyanagi, S., Katz, M., Koprowski, H. Proc. Soc. exp. Biol. Med. 1970, 134, 230. 7. Huang, A. S., Baltimore, D. Nature, Lond. 1970, 226, 325. 8. Jabbour, J. T., Sever, J. L., Horta-Barbosa, L. Presented at the 97th annual meeting of the American Public Health Association, Philadelphia, Pennsylvania, November, 1969.
Fig. 1-On-line system.
which indicates the rate between successive heart beats, and a pen recorder with some electronically operated controls. To simplify the location of specific sections of record, the tape has coded time markers recorded on one track. The equipment is connected to the conventional bedside E.C.G. amplifier and oscilloscope. DR.
BRODY,
DR. DETELS:
REFERENCES—continued
Jabbour, J. T., Duenas, D. A., Krebs, H., Sever, J. L., HortaBarbosa, L. Presented in part at World Congress of Neurology, New York City, 1969, and the American Public Health Association, Philadelphia, Pennsylvania, November, 1969. 10. Canal, N., Torck, P. J. neurol. Sci. 1964, 1, 380. 11. Canelas, H. M., Lefevre, A. B., Tognola, W. A., Fonesca, L. C., Juliao, O. F., de Assis, J. L., de Jorge, F. B., Xavier-Lima, A. Archos Neuropsiquiat., S. Paulo, 1967, 25, 255. 12. Nelson, K. E. Personal communication. 9.
502 The
input fiom the E.c.G. amplifier is fed to the rateand to the tape recorder simultaneously (fig. 1); the output of the tape recorder being connected to the pen recorder which in turn is started and stopped by the meter
rate-meter.
If the instantaneous heart-rate falls outside certain rate-meter triggers the control circuits which, after a 7-second delay, start the pen recorder which runs for 14 seconds. As the pen recorder is connected to the tape recorder, the output of which is delayed fourteen seconds from its input, the trace which is written on to paper consists of a seven-second portion of record immediately preceding the aberrant beat, then the irregular beat itself, then a further seven-second " portion of normal record. Accompanying the E.c.G. are any other physiological signals that might be required and a trace of the code from the timing track, which accurately locates the piece of data both in time and in position on the magnetic tape. In practice, this system is very convenient; the volume of written data is greatly reduced and the clinician has his attention drawn only to those parts in which he is interested.
predefined limits, the
Both the on-line and the off-line parts of the monitoring system have been designed to allow pre-editing by the machinery and to give the clinician the opportunity of overriding and validating the process himself if required. It has been found in practice that it is much easier to obtain reliable information from large quantities of data by this semiautomatic method than by either fully manual or fully automatic procedures. We thank the Medical Research Council for the use of the computer facilities in the engineering and medicine laboratory, at Imperial College, and the British Heart Foundation for a grant to purchase the magnetic tape recorder. S. P. V. is supported by a grant from the Leverhulme Foundation. Requests for reprints should be addressed to J. T.
"
OFF-LINE SYSTEM
The foregoing recording procedure also serves as the basis for producing a data bank " of E.C.G. signals suitable for detailed analysis. For such data to have value, they must be edited to remove the artefacts. The off-line svstem is a comDuter-based Drocedure for oerformins this "
PNEUMATIC INTERMITTENT-COMPRESSION LEGGING SIMULATING CALF-MUSCLE PUMP
J. S. CALNAN
J. J. PFLUG C.
J. MILLS
Department of Plastic
and Reconstructive Surgery, and Medical Research Council Cardiovascular Unit, Royal Postgraduate Medical School, London W.12
A CENTURY ago, Virchowconcluded that there were three factors responsible for venous thrombosis-stasis of blood-flow, hypercoagulability of blood, and vessel intimal damage. Modern opinion agrees. Anticoagulants have been moderately successful for therapy,2 but in prophylaxis for surgery they have been found to be unmanageable. Surgeons have, therefore, concentrated on methods for preventing venous stasis. Early patient mobilisation after operations has reduced the incidence of fatal pulmonary emboli,3 but this level is unacceptably high. The use of the 125I-labelled fibrinogen technique 4,5 has made it clear that venous thrombosis in the legs is much more prevalent than had previously been thought. Venous return from the legs depends on three pumping mechanisms-the vis-a-tergo from the heart, the thoracic and abdominal pressure during respiration, and the soleal muscle sinuses in the calf during walking. All three are less 1. 2. 3. 4.
Virchow, R. L. K. Thrombose and Emboli. Frankfurt, Sevitt, S., Gallagher, N. Br. J. Surg. 1961, 48, 473.
1856.
Murley, R. S. Ann. R. Coll. Surg. 1950, 6, 283. Negus, D., Pinto, D. J., Le Quesne, L. P., Brown, N., Chapman, M. Br. J. Surg. 1968, 55, 835. 5. Flanc, C., Kakkar, V. V., Clarke, M. B. ibid. p. 742.
Fig. 2-Off-line system.
equipment consists of a digital computer with input/output facilities, including a special terminal which enables the computer to display stored information on an oscilloscope screen. Part of this terminal is a light-operated pen " which allows the user to interact with the display and to modify the contents of the computer memory (fig. 2). A programme has been developed to write recorded E.C.G. data on to digital magnetic tape and to enable the user to replay this tape on to the graphical output oscillofreeze " the display at any time to look scope. He can at any portion of the data in more detail. This programme can detect the position of each heart beat and marks this position on the oscilloscope screen. Should the pro-
task. The
"
"
gramme make an error, it will be evident to the user who, using the light pen, can correct it. The presence of the time markers on those parts of the record which have been written out on paper greatly simplifies the procedure, since it again draws attention to sections containing abnormalities. The final output from the system is a digital magnetic tape free from artefact with interesting features of the record marked and available for manual or automatic
analysis.
Fig. 1-pneumatic legging.