The Equipment of the Intensive Care Unit JOHN
K.
VRIES, M.D., AND DONALD
P.
BECKER, M.D.
This paper describes a system for monitoring neurosurgical patients in the intensive care unit. The system has been in operation at the Medical College of Virginia for the past three years. It has proved to be practical, reliable, and effective. In addition, it has the flexibility necessary to meet a wide range of monitoring needs. ORGANIZATION
The basic organization of the monitoring system is shown in Figure 22.1. The physiological parameters to be monitored are converted to electrical analog signals by means of appropriate transducers. The transducer outputs are then amplified to levels which are suitable for operating output devices. Next, the amplified outputs are displayed visually for clinical use. Finally, the amplified outputs are stored on magnetic tape for computer analysis. The basic scheme remains the same regardless of the number or types of parameters monitored. The Patient Connection and the Transducer ARTERIAL BLOOD PRESSURE
Blood pressure is monitored from the femoral artery by means of an 18gauge Teflon (E. I. duPont de Nemours & Co., Wilmington, Del.) catheter (Richmond Surgical Supplies, Richmond, Va.). The catheter is inserted percutaneously and is threaded into the artery by means of a guide wire. The catheter is connected to a stopcock manifold by means of saline filled tubing. The electrical analog signal for blood pressure is generated by a strain gauge transducer connected to the arterial line through the stopcock manifold (1, 6). Clotting of the artery is prevented by a slow infusion of heparinized saline from an arterial infusion bag. The manifold system is shown in Figure 22.2. Blood pressure is occasionally monitored from other arteries. However, the femoral artery has three advantages: (1) the catheterization is very easy; (2) the patient does not require distal extremity restraints; and (3) the large lumen of the femoral catheter easily accepts p02 probes. To date there have been no thrombotic complications related to the use of the femoral artery for monitoring. 411
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CHAPTER 22
412
CLINICAL NEUROSURGERY
FIG.
DATA STORAGE SYSTEM
DATA ANALYSIS SYSTEM
22.1. The basic organization of a patient monitoring system.
CENTRAL VENOUS PRESSURE
Central venous pressure is monitored by means of an 18-gauge radiopaque catheter (Intrafusion model 210014, Sorenson Research Co., Salt Lake City, Utah) which is inserted percutaneously in the antecubital fossa and is threaded into the subclavian vein. The position of the catheter is confirmed by x-ray. The catheter is then connected to a stopcock manifold system which is identical to the one used for arterial blood pressure. For convenience the blood pressure and the central venous pressure lines occupy opposite ends of the same stopcock manifold (Fig. 22.2). INTRACRANIAL PRESSURE
Intracranial pressure is monitored by means of an intracranial pressure screw or a ventricular catheter. The technique for inserting an intracranial pressure screw has been described elsewhere and will not be repeated here (4). Ventricular catheters are placed using a modification of the Lundberg technique (3). The intracranial pressure screw or the ventricular catheter is connected by means of saline filled tubing to the same type of stopcock manifold used for the blood pressure and the central venous pressure. The analog electrical signal is also generated by a strain gauge transducer. The manifold system for intracranial pressure, containing a water manometer for calibration, is shown in Figure 22.3. The majority of intracranial pressure monitoring is performed using the intracranial pressure screw because of its lower incidence of infection in our hands. The ventricular catheter is reserved for situations where ventricular drainage is contemplated.
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DATA DISPLAY SYSTEM
INTENSIVE CARE UNIT: EQUIPMENT
413
TEMPERATURE
Temperature is monitored by means of a rectal probe (model SM 3605, Statham Instruments, Inc., Oxnard, Calif.). The tip of the probe contains a thermistor which is part of an electrical bridge circuit in the preamplifier module (6). Changes in temperature at the tip of the probe change the resistance of the thermistor, unbalance the bridge, and generate an electrical analog signal of the temperature. ELECTROCARDIOGRAM (EKG)
The EKG is monitored from a set of self adhering disposable chest electrodes (Monitoring Electrode, Model 65375-010, America Hospital
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.2. Manifold system for monitoring the blood pressure and the central venous pressure (Disposable Five Stopcock Manifold, Cobe Laboratories, Inc., Lakewood, Colo.).
414
CLINICAL NEUROSURGERY
Supply Corp., Evanston, Ill.) which pick up the electrical potential generated by cardiac activity (1, 2). Since the EKG is already in the form of an electrical analog signal, it is passed directly to the amplifier system without transduction. The Amplifier System
The electrical signals generated by the transducers have a very low level. In order to operate output devices such as oscilloscopes or recording charts, they must be amplified. This is usually accomplished by a two stage amplifier system (2). The first stage of the amplifier is known as the preamplifier
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FIG. 22.3. Manifold system for monitoring the intracranial pressure (transducer models P-37 and P-23 la, Statham Instruments, Inc., Oxnard, Calif.).
INTENSIVE CARE UNIT: EQUIPMENT
415
CALIBRATION AND RANGE
For accurate monitoring, the zero base line and the gain of each amplifier module must be calibrated against an external standard. The standard for
FIG. 22.4. Plug-in amplifier modules used to monitor the arterial blood pressure, the central venous pressure, the intracranial pressure, the temperature, and the EKG (models SM 1007, SM 1009, SM 1067, SM 1006, SM 1065, Statham Instruments, Inc., Oxnard, Calif.).
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
or the signal conditioner. The preamplifier is designed to match a specific type of transducer. Its function is to supply the special input circuitry required by the transducer, and to select the low level transducer signal from the electrical noise. The second stage of the amplifier system is known as the driver amplifier. Its function is to supply the power amplification required to operate the output devices. The amplifiers used to monitor the blood pressure, the central venous pressure, the intracranial pressure, the temperature, and the ERG are shown in Figure 22.4. In this particular system each preamplifier and corresponding driver amplifier are contained in a single plug-in unit. A very important feature of this system is the fact that these units can be interchanged in the bedside mounting rack to make up different monitoring configurations (1, 5). The modules are shown again in Figure 22.5, inserted into the bedside mounting rack.
416
CLINICAL NEUROSURGERY
blood pressure is a mercury manometer and the standard for central venous pressure and intracranial pressure is the water manometer. The standard for temperature is the water bath at known temperature. The standard for the EKG is a battery. Since the gain of the system is relatively stable compared to the drift of the zero base line, it is expedient to calibrate the gain once or twice a week and confine routine calibrations to zero balancing. This simplifies the calibration procedure for ancillary personnel with only a minimal loss of accuracy. Blood pressure is generally calibrated for a range of 0 to 300 mm. Hg. Central venous pressure is calibrated for 0 to 30 mm. Hg. The intracranial pressure is calibrated for two ranges: 0 to 60 mm. Hg. and 0 to 300 mm.
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FIG. 22.5. Bedside mounting rack containing the plug-in amplifier modules, power supply, and a four channel oscilloscope (models SM 1034 Power Supply and SM 1052 Monitor, Statham Instruments, Inc., Oxnard, Calif.).
INTENSIVE CARE UNIT : EQUIPMENT
417
The Alarm System If the physiological parameters monitored are above or below levels which are set by controls on the amplifier modules, an alarm unit is triggered (1, 5). The unit used with this system (Central Monitor, model SM 217B, Statham Instruments, Inc., Oxnard, Calif.) sounds a buzzer, indicates which patient triggered the alarm by a flashing light, and activates a small strip chart for detailed recording of ictal events.
The Switching Network The switching network is another feature giving flexibility to the monitoring system. The function of the switching network is to allow the output from any amplifier to be sent to any output device. This allows recorders, tapedecks, oscilloscopes, or computer terminals to be connected and disconnected from the system at will without wiring changes. In the system described in this paper this is accomplished by a phone jack matrix and a cable and plug system similar to a telephone switchboard.
The Display System Raw data from the amplifier outputs are distributed to three types of display devices by the switching network. The first display device is a four channel oscilloscope. It is mounted on the wall at bedside, as shown in Figure 22.5. The oscilloscope serves four purposes: (1) it allows the wave form of the pressure traces from the patient to be followed, which is essential to ensure the reliability of these measurements; (2) it displays the EKG for the detection and assessment of arrhythmias; (3) it provides a convenient bedside output for calibration purposes; and (4) it allows one nurse to keep a close eye on several different patients from a distance (1, 5, 6). The second type of display device is the meter. These devices are generally mounted on the front of the amplifier modules. The meters are connected to the output of the amplifier through various resistance-capacitance networks with special time constants to accentuate certain parts of the signal. Their purpose is to provide mean values, systolic and diastolic pressures, and, in the case of the ERG module, the heart rate (2). The third type of display device is the recording chart. Its purpose is to provide a permanent written record of the physiological parameters monitored (6). The chart used in this system is shown in Figure 22.6. It has an eight channel capacity, and a pressurized ink writing system. It is essential that recording charts be of the highest possible quality, since they are subjected
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Hg. The temperature is calibrated for 930 F. to 1070 F. The EKG is calibrated for full scale deflection at 1 mv. input.
418
CLINICAL NEUROSURGERY
to considerable wear and tear in intensive care unit situations. The chart recorder must also be able to function over a wide range of speeds so that low speed trend recording and high speed wave analysis are both possible. Computerization
The main weakness of the system described in this paper is that it can produce more raw physiological data than can usefully be assimilated. To overcome this problem it is necessary to computerize the system. The monitoring system is currently connected via the switching network
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.6. Eight channel recording chart for making permanent written records of patient data (Gould Brush model 200, Gould Inc., Brush Division, Cleveland, Ohio).
INTENSIVE CARE UNIT: EQUIPMENT
419
to a remote computer terminal located in the intensive care unit. The terminal is shown in Figure 22.7. Data from the monitoring system are fed through the terminal to the main computer facility which is located in an adjacent building. The keyboard of the terminal serves to send instructions to the computer. The screen of the terminal receives the output from the computer (1). Permanent copies of computer output are obtained by activating the line printer shown in Figure 22.8. When fully operational, the computer will receive up to 70 channels of input data simultaneously from seven intensive care unit beds. It is programmed to plot trends on data, to summarize data on variable time scales, to digitalize data and file them for later recall, to correlate data, to trigger the alarm system, and to calculate specialized functions including EEG spectrum analysis, sensory evoked responses, and regional cerebral blood flow in conjunction with the Harshaw system (Harshaw Chemical,
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FIG. 22.7. Computer terminal which forms the interface between the monitoring equipment and the main computer facility (Computek model 300, Computek, Inc., Cambridge, Mass.). Instructions are sent to the computer by the keyboard. Output from the computer is received on the screen.
420
CLINICAL NEUROSURGERY
Inc., Solon, Ohio). The general plan of the computerized intensive care unit monitoring system is shown in Figure 22.9. COMMENT
The monitoring system described in this paper can be adapted to meet a wide variety of monitoring needs. The system can be made smaller by eliminating the computer, reducing the number of amplifier modules per bed, and reducing the size of the central recording chart. The system can be expanded by doing the reverse. The type of physiological parameter monitored can be changed by changing the plug-in amplifier modules and substituting the appropriate transducers and patient connections. The system described in this paper has been used on occasion to monitor the arterial P02, the jugular venous P02, the end expiratory CO2, the respiratory rate, and the EEG (1, 2). It should also be emphasized that a considerable number of commercial manufacturers make equipment comparable to that shown in this paper, and that the system is not locked in to a brand name.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.8. Line printer used to make hard copies of computer outputs (Versatec Inc., Cupertino, Calif.).
INTENSIVE CARE UNIT: EQUIPMENT
s CHANNEL
I
,1------
FIG. 22.9. Basic organizational plan for a computerized monitoring system with multiple display capability.
SUMMARY
A system for monitoring neurosurgical patients in the intensive care unit is described. The system is very flexible, and can easily be adapted to small scale or large scale monitoring needs. The system is also suitable for computerization. REFERENCES 1. Cromwell, L., Weibell, F. J., Pfeiffer, E. A., and Usselman, L. B. Biomedical Instrumentation and Measurements, 446 pp. Prentice-Hall Inc., Englewood Cliffs, New Jersey, 1973. (See chapters 6,7, 10, 15.) 2. Geddes, L. A., and Baker, L. E. Principles of Applied Biomedical Instrumentation, 479 pp. John Wiley and Sons, Inc., New York, 1968. (See chapters 9-11,13.) 3. Lundberg, N. Continuous recording and control of ventricular fluid pressure in neurosurgical practice. Acta Psychiatr. Neurol. Scand., 36: suppl. 149, 1-193, 1960. 4. Vries, J. K., Becker, D. P., and Young, H. F. A subarachnoid screw for monitoring intracranial pressure. Technical note. J. Neurosurg., 39: 416-419, 1973. 5. Weiss, D. Biomedical Instrumentation, 286 pp. Chilton Book Company, Philadelphia, 1973. (See chapter 7.) 6. Yanof, H. M. Biomedical Electronics, 361 pp. F. A. Davis Co., Philadelphia, 1965. (See chapters 9 and 10.)
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
I
- - - - - - - - - - , TAPE DECK
421
K.
VRIES, M.D., AND DONALD
P.
BECKER, M.D.
This paper describes a system for monitoring neurosurgical patients in the intensive care unit. The system has been in operation at the Medical College of Virginia for the past three years. It has proved to be practical, reliable, and effective. In addition, it has the flexibility necessary to meet a wide range of monitoring needs. ORGANIZATION
The basic organization of the monitoring system is shown in Figure 22.1. The physiological parameters to be monitored are converted to electrical analog signals by means of appropriate transducers. The transducer outputs are then amplified to levels which are suitable for operating output devices. Next, the amplified outputs are displayed visually for clinical use. Finally, the amplified outputs are stored on magnetic tape for computer analysis. The basic scheme remains the same regardless of the number or types of parameters monitored. The Patient Connection and the Transducer ARTERIAL BLOOD PRESSURE
Blood pressure is monitored from the femoral artery by means of an 18gauge Teflon (E. I. duPont de Nemours & Co., Wilmington, Del.) catheter (Richmond Surgical Supplies, Richmond, Va.). The catheter is inserted percutaneously and is threaded into the artery by means of a guide wire. The catheter is connected to a stopcock manifold by means of saline filled tubing. The electrical analog signal for blood pressure is generated by a strain gauge transducer connected to the arterial line through the stopcock manifold (1, 6). Clotting of the artery is prevented by a slow infusion of heparinized saline from an arterial infusion bag. The manifold system is shown in Figure 22.2. Blood pressure is occasionally monitored from other arteries. However, the femoral artery has three advantages: (1) the catheterization is very easy; (2) the patient does not require distal extremity restraints; and (3) the large lumen of the femoral catheter easily accepts p02 probes. To date there have been no thrombotic complications related to the use of the femoral artery for monitoring. 411
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
CHAPTER 22
412
CLINICAL NEUROSURGERY
FIG.
DATA STORAGE SYSTEM
DATA ANALYSIS SYSTEM
22.1. The basic organization of a patient monitoring system.
CENTRAL VENOUS PRESSURE
Central venous pressure is monitored by means of an 18-gauge radiopaque catheter (Intrafusion model 210014, Sorenson Research Co., Salt Lake City, Utah) which is inserted percutaneously in the antecubital fossa and is threaded into the subclavian vein. The position of the catheter is confirmed by x-ray. The catheter is then connected to a stopcock manifold system which is identical to the one used for arterial blood pressure. For convenience the blood pressure and the central venous pressure lines occupy opposite ends of the same stopcock manifold (Fig. 22.2). INTRACRANIAL PRESSURE
Intracranial pressure is monitored by means of an intracranial pressure screw or a ventricular catheter. The technique for inserting an intracranial pressure screw has been described elsewhere and will not be repeated here (4). Ventricular catheters are placed using a modification of the Lundberg technique (3). The intracranial pressure screw or the ventricular catheter is connected by means of saline filled tubing to the same type of stopcock manifold used for the blood pressure and the central venous pressure. The analog electrical signal is also generated by a strain gauge transducer. The manifold system for intracranial pressure, containing a water manometer for calibration, is shown in Figure 22.3. The majority of intracranial pressure monitoring is performed using the intracranial pressure screw because of its lower incidence of infection in our hands. The ventricular catheter is reserved for situations where ventricular drainage is contemplated.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
DATA DISPLAY SYSTEM
INTENSIVE CARE UNIT: EQUIPMENT
413
TEMPERATURE
Temperature is monitored by means of a rectal probe (model SM 3605, Statham Instruments, Inc., Oxnard, Calif.). The tip of the probe contains a thermistor which is part of an electrical bridge circuit in the preamplifier module (6). Changes in temperature at the tip of the probe change the resistance of the thermistor, unbalance the bridge, and generate an electrical analog signal of the temperature. ELECTROCARDIOGRAM (EKG)
The EKG is monitored from a set of self adhering disposable chest electrodes (Monitoring Electrode, Model 65375-010, America Hospital
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.2. Manifold system for monitoring the blood pressure and the central venous pressure (Disposable Five Stopcock Manifold, Cobe Laboratories, Inc., Lakewood, Colo.).
414
CLINICAL NEUROSURGERY
Supply Corp., Evanston, Ill.) which pick up the electrical potential generated by cardiac activity (1, 2). Since the EKG is already in the form of an electrical analog signal, it is passed directly to the amplifier system without transduction. The Amplifier System
The electrical signals generated by the transducers have a very low level. In order to operate output devices such as oscilloscopes or recording charts, they must be amplified. This is usually accomplished by a two stage amplifier system (2). The first stage of the amplifier is known as the preamplifier
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.3. Manifold system for monitoring the intracranial pressure (transducer models P-37 and P-23 la, Statham Instruments, Inc., Oxnard, Calif.).
INTENSIVE CARE UNIT: EQUIPMENT
415
CALIBRATION AND RANGE
For accurate monitoring, the zero base line and the gain of each amplifier module must be calibrated against an external standard. The standard for
FIG. 22.4. Plug-in amplifier modules used to monitor the arterial blood pressure, the central venous pressure, the intracranial pressure, the temperature, and the EKG (models SM 1007, SM 1009, SM 1067, SM 1006, SM 1065, Statham Instruments, Inc., Oxnard, Calif.).
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
or the signal conditioner. The preamplifier is designed to match a specific type of transducer. Its function is to supply the special input circuitry required by the transducer, and to select the low level transducer signal from the electrical noise. The second stage of the amplifier system is known as the driver amplifier. Its function is to supply the power amplification required to operate the output devices. The amplifiers used to monitor the blood pressure, the central venous pressure, the intracranial pressure, the temperature, and the ERG are shown in Figure 22.4. In this particular system each preamplifier and corresponding driver amplifier are contained in a single plug-in unit. A very important feature of this system is the fact that these units can be interchanged in the bedside mounting rack to make up different monitoring configurations (1, 5). The modules are shown again in Figure 22.5, inserted into the bedside mounting rack.
416
CLINICAL NEUROSURGERY
blood pressure is a mercury manometer and the standard for central venous pressure and intracranial pressure is the water manometer. The standard for temperature is the water bath at known temperature. The standard for the EKG is a battery. Since the gain of the system is relatively stable compared to the drift of the zero base line, it is expedient to calibrate the gain once or twice a week and confine routine calibrations to zero balancing. This simplifies the calibration procedure for ancillary personnel with only a minimal loss of accuracy. Blood pressure is generally calibrated for a range of 0 to 300 mm. Hg. Central venous pressure is calibrated for 0 to 30 mm. Hg. The intracranial pressure is calibrated for two ranges: 0 to 60 mm. Hg. and 0 to 300 mm.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.5. Bedside mounting rack containing the plug-in amplifier modules, power supply, and a four channel oscilloscope (models SM 1034 Power Supply and SM 1052 Monitor, Statham Instruments, Inc., Oxnard, Calif.).
INTENSIVE CARE UNIT : EQUIPMENT
417
The Alarm System If the physiological parameters monitored are above or below levels which are set by controls on the amplifier modules, an alarm unit is triggered (1, 5). The unit used with this system (Central Monitor, model SM 217B, Statham Instruments, Inc., Oxnard, Calif.) sounds a buzzer, indicates which patient triggered the alarm by a flashing light, and activates a small strip chart for detailed recording of ictal events.
The Switching Network The switching network is another feature giving flexibility to the monitoring system. The function of the switching network is to allow the output from any amplifier to be sent to any output device. This allows recorders, tapedecks, oscilloscopes, or computer terminals to be connected and disconnected from the system at will without wiring changes. In the system described in this paper this is accomplished by a phone jack matrix and a cable and plug system similar to a telephone switchboard.
The Display System Raw data from the amplifier outputs are distributed to three types of display devices by the switching network. The first display device is a four channel oscilloscope. It is mounted on the wall at bedside, as shown in Figure 22.5. The oscilloscope serves four purposes: (1) it allows the wave form of the pressure traces from the patient to be followed, which is essential to ensure the reliability of these measurements; (2) it displays the EKG for the detection and assessment of arrhythmias; (3) it provides a convenient bedside output for calibration purposes; and (4) it allows one nurse to keep a close eye on several different patients from a distance (1, 5, 6). The second type of display device is the meter. These devices are generally mounted on the front of the amplifier modules. The meters are connected to the output of the amplifier through various resistance-capacitance networks with special time constants to accentuate certain parts of the signal. Their purpose is to provide mean values, systolic and diastolic pressures, and, in the case of the ERG module, the heart rate (2). The third type of display device is the recording chart. Its purpose is to provide a permanent written record of the physiological parameters monitored (6). The chart used in this system is shown in Figure 22.6. It has an eight channel capacity, and a pressurized ink writing system. It is essential that recording charts be of the highest possible quality, since they are subjected
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
Hg. The temperature is calibrated for 930 F. to 1070 F. The EKG is calibrated for full scale deflection at 1 mv. input.
418
CLINICAL NEUROSURGERY
to considerable wear and tear in intensive care unit situations. The chart recorder must also be able to function over a wide range of speeds so that low speed trend recording and high speed wave analysis are both possible. Computerization
The main weakness of the system described in this paper is that it can produce more raw physiological data than can usefully be assimilated. To overcome this problem it is necessary to computerize the system. The monitoring system is currently connected via the switching network
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.6. Eight channel recording chart for making permanent written records of patient data (Gould Brush model 200, Gould Inc., Brush Division, Cleveland, Ohio).
INTENSIVE CARE UNIT: EQUIPMENT
419
to a remote computer terminal located in the intensive care unit. The terminal is shown in Figure 22.7. Data from the monitoring system are fed through the terminal to the main computer facility which is located in an adjacent building. The keyboard of the terminal serves to send instructions to the computer. The screen of the terminal receives the output from the computer (1). Permanent copies of computer output are obtained by activating the line printer shown in Figure 22.8. When fully operational, the computer will receive up to 70 channels of input data simultaneously from seven intensive care unit beds. It is programmed to plot trends on data, to summarize data on variable time scales, to digitalize data and file them for later recall, to correlate data, to trigger the alarm system, and to calculate specialized functions including EEG spectrum analysis, sensory evoked responses, and regional cerebral blood flow in conjunction with the Harshaw system (Harshaw Chemical,
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.7. Computer terminal which forms the interface between the monitoring equipment and the main computer facility (Computek model 300, Computek, Inc., Cambridge, Mass.). Instructions are sent to the computer by the keyboard. Output from the computer is received on the screen.
420
CLINICAL NEUROSURGERY
Inc., Solon, Ohio). The general plan of the computerized intensive care unit monitoring system is shown in Figure 22.9. COMMENT
The monitoring system described in this paper can be adapted to meet a wide variety of monitoring needs. The system can be made smaller by eliminating the computer, reducing the number of amplifier modules per bed, and reducing the size of the central recording chart. The system can be expanded by doing the reverse. The type of physiological parameter monitored can be changed by changing the plug-in amplifier modules and substituting the appropriate transducers and patient connections. The system described in this paper has been used on occasion to monitor the arterial P02, the jugular venous P02, the end expiratory CO2, the respiratory rate, and the EEG (1, 2). It should also be emphasized that a considerable number of commercial manufacturers make equipment comparable to that shown in this paper, and that the system is not locked in to a brand name.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
FIG. 22.8. Line printer used to make hard copies of computer outputs (Versatec Inc., Cupertino, Calif.).
INTENSIVE CARE UNIT: EQUIPMENT
s CHANNEL
I
,1------
FIG. 22.9. Basic organizational plan for a computerized monitoring system with multiple display capability.
SUMMARY
A system for monitoring neurosurgical patients in the intensive care unit is described. The system is very flexible, and can easily be adapted to small scale or large scale monitoring needs. The system is also suitable for computerization. REFERENCES 1. Cromwell, L., Weibell, F. J., Pfeiffer, E. A., and Usselman, L. B. Biomedical Instrumentation and Measurements, 446 pp. Prentice-Hall Inc., Englewood Cliffs, New Jersey, 1973. (See chapters 6,7, 10, 15.) 2. Geddes, L. A., and Baker, L. E. Principles of Applied Biomedical Instrumentation, 479 pp. John Wiley and Sons, Inc., New York, 1968. (See chapters 9-11,13.) 3. Lundberg, N. Continuous recording and control of ventricular fluid pressure in neurosurgical practice. Acta Psychiatr. Neurol. Scand., 36: suppl. 149, 1-193, 1960. 4. Vries, J. K., Becker, D. P., and Young, H. F. A subarachnoid screw for monitoring intracranial pressure. Technical note. J. Neurosurg., 39: 416-419, 1973. 5. Weiss, D. Biomedical Instrumentation, 286 pp. Chilton Book Company, Philadelphia, 1973. (See chapter 7.) 6. Yanof, H. M. Biomedical Electronics, 361 pp. F. A. Davis Co., Philadelphia, 1965. (See chapters 9 and 10.)
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/22/CN_suppl_1/411/4099434 by guest on 24 October 2019
I
- - - - - - - - - - , TAPE DECK
421
