Transcript
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Complete Biomedical Equipment Designed for Stress Tests Beriliu ILIE Abstract: The aim of this paper is to present a complete equipment for use in stress test – laboratories, based on LabVIEW® graphical programming environment. The equipment is composed of a treadmill stress test device, an ECG, a respiratory gases analyzer and a data acquisition system, connected to a computer. In addition to offering a practical equipment, it has also been attempted to develop an ergonomic and user-friendly graphical interface, easily understood and used by medical staff. Keywords: Stress test; LabVIEW® graphical programming environment; Treadmill; Respiratory gases analyzer.
1. Introduction
2. Design
It has lately been noted that medical equipments based on computers are becoming more and more popular, to the expense of dedicated equipments. This is possible due to an increase in the performance of computers and an improvement of the performance/price ratio, which is clearly in favour of performances and, implicitly, of the end-user. Moreover, a computer-based equipment is much more versatile than its dedicated counterpart, and, in most cases, a software upgrade ensures the compatibility with the new working methods.
In this paper, I will present a complete biomedical equipment used for stress tests. It is composed of: A. Treadmill stress test equipment B. ECG C. Respiratory gases analyzer D. Data acquisition system E. Computer program for data processing The block diagram of the equipment is shown in picture 1. A. The treadmill stress test equipment is controlled by an RISC microcontroller PIC16F877 and uses an asynchronous triphase motor powered by a frequency inverter type Mitsubishi FR-S500 for speed, and a DC
%CO2 CAPNOLYSER CB 68 LP BOARD
NATIONAL INSTRUMENTS ACQUISITION EQUIPMENT
ECG BIOSET 6000 INPUT TREADMILL MONITOR
COMPUTER OUTPUT
TREADMILL CONTROL
Picture 1.
LabView® Program
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motor for actuating the slope. The information regarding the program status, the actual and programmed speed, actual and programmed slope, and the remaining time, is displayed on an alphanumeric LCD display. The equipment has three working-modes: 1. Manual: in this mode there is the possibility of continuously adjusting the slope and velocity of the treadmill using the front panel buttons 2. Local automated: the user can chose between five predetermined programs (protocols) for stress tests shown in the next tables or, can create and save a custom test protocol. The equipment sends the actual slope and speed parameters to the computer. Bruce Protocol Seq. no 1 2 3 4 5 6 7 8 9
speed [km/h] 2,7 2,7 2,7 4,0 5,5 6,7 8,0 8,8 9,6
slope [%] 0 5 10 12 14 16 18 20 22
Time [min] 3 3 3 3 3 3 3 3 3
Low-Level Protocol Seq.no speed [km/h] 1 1,9 2 1,9 3 1,9 4 2,7
slope [%] 0 3 6 6
Time [min] 2 1 1 1
Ellestad Protocol Seq.no speed [km/h] 1 2,7 2 4,8 3 6,4 4 8,0 5 8,0 6 9,6
slope [%] 10 10 10 10 15 15
Time [min] 4 2 2 2 2 2
Mc Henry Protocol Seq.no speed [km/h] 1 4,0 2 5,3 3 5,3 4 5,3 5 5,3 6 5,3 7 5,3
slope [%] 3 6 9 12 15 18 22
Time [min] 3 3 1 2 2 1 2
Balke Protocol Seq.no 1 2 3 4 5 6 7 8 9 10
slope [%] 0 2,5 5 7,5 10 12,5 15 17,5 20 22,5
Time [min] 2 2 2 2 2 2 2 2 2 2
speed [km/h] 1,9 1,9 1,9 1,9 1,9 1,9 1,9 1,9 1,9 1,9
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3. Remote (distance operated): in this mode the equipment follows the instructions (velocity and slope) sent by the main computer or by a stress test-specialized ECG. The block diagram of the treadmill stress test equipment is shown in picture 2. Panou de comandă Pornit \ Oprit
Butoane de comandă Comandă viteză
Interfaţă serială
B3
B2
B1
Comandă înclinaţie
Stop de Urgenţă
Afişaj LCD
Microcontroller
Buffer
Stop de urgenţa
Sursă de alimentare
Control înclinaţie Mărire înclinaţie
Invertor
Micşorare înclinaţie
Citire înclinaţie Traductor viteză + sens
Motor de c.c.
Motor asincron
Înclinaţie
(înclinaţie)
(viteza )
Înclinaţie minimă
Picture 2.
The main functional controls will be more specifically presented, starting with speed control. The block diagram is shown in picture 3, and the electrical diagram in picture 4. The inverter speed control is driven by a low pass buffered filter, used for converting the 8 bit PWM type output of the microcontroller CCP1 pin, in DC voltage between 0 to 4V, corresponding to a speed between 0 to 12 km/h. For safety reason, the inverter idle state is forced by a supplementary on-off signal from microcontroller CCP2 pin. Microcontroller
Buffer
Picture 3.
Invertor
Motor
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MCLR/Vpp OSC1/CLKIN
RCO/T1OSO/T1CKI RC1/T1OSI/CCP2 RC2/CCP1 RC3/SCK/SCL RC4/SDI/SDA RC5/SDO RC6/TX/CK RC7/RX/DT RD0/PSP0 RD1/PSP1 RD2/PSP2 RD3/PSP3 RD4/PSP4 RD5/PSP5 RD6/PSP6 RD7/PSP7
PIC16F877
RE0/RD/AN5 RE1/WR/AN6 RE2/CS/AN7
1
33 34 35 36 37 38 39 40 15 16 17 18 23 24 25 26
U4A 4093
2
3
PWM R2
U3 3
100K
+
TL071
C8 100n 2
19 20 21 22 27 28 29 30
-
1
O
F
+12V
Control v iteza
7
1 13
+5V
V+
RBO/INT RB1 RB2 RB3 RB4 RB5 RB6 RB7
2 3 4 5 6 7
OS1
OUT
V-
RA0/AN0 RA1/AN1 RA2/AN2 RA3/AN3/VREF RA4/TOCKI RA5/AN4/SS
U8
14
OS2
1
2 R4 100K
6
3 5 4
on-of f Gnd R +5v
4
OSC2/CLKOUT
Invertor
U V W
S R5 1K5
C9 100p
R3 10K
T
M 3~
-12V
Motor asincron
8 9 10
Picture 4.
1 13
MCLR/Vpp OSC1/CLKIN
RCO/T1OSO/T1CKI RC1/T1OSI/CCP2 RC2/CCP1 RC3/SCK/SCL RC4/SDI/SDA RC5/SDO RC6/TX/CK RC7/RX/DT
PIC16F877
RD0/PSP0 RD1/PSP1 RD2/PSP2 RD3/PSP3 RD4/PSP4 RD5/PSP5 RD6/PSP6 RD7/PSP7 RE0/RD/AN5 RE1/WR/AN6 RE2/CS/AN7
15 16 17 18 23 24 25 26
U6C 4093
8
4
33 34 35 36 37 38 39 40
+5V 9 10
2
Q
U12
R
RBO/INT RB1 RB2 RB3 RB4 RB5 RB6 RB7
2 3 4 5 6 7
4013 U11A CLK 1
Q
S
RA0/AN0 RA1/AN1 RA2/AN2 RA3/AN3/VREF RA4/TOCKI RA5/AN4/SS
U8
14
D
3
C2 E C1
5
A K
Traductor rotatie R11 100K
6
OSC2/CLKOUT
R12 100K
R10
Comanda viteza
750
19 20 21 22 27 28 29 30 8 9 10
Picture 5.
Adaptor
Motor
Microcontroller Adaptor
Traductor înclinaţie
Picture 6.
In manual mode or in the programming mode, the speed is set by a digital rotating knob like in picture 5, where the gate U6A generates pulse and the D flip-flop U11A generates direction, according to the rotation of the knob.
The block diagram for the slope control is shown in picture 6, and the electrical diagram in picture 7. The slope motor is driven by the two relays K1 and K2, interfaced by a power driver ULN2003. The slope is read by an incremental transducer similar to the ‘digital
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PIC16F877
RD0/PSP0 RD1/PSP1 RD2/PSP2 RD3/PSP3 RD4/PSP4 RD5/PSP5 RD6/PSP6 RD7/PSP7
8 9 10
100n 10K 2
limitator maxim
3
+5V
2 1
1
3
5
2 1
U4B 4093
K2
K1
9 10
U4C 4093
C18
8
2 3
19 20 21 22 27 28 29 30
C17
6 4
U6A 4093
100n
R17 1
2
1 limitator minim 10K
+24V +5V
2
Q
U17
4013 U7A CLK 1
Q
D
3
C2 E C1
5
6 14
RE0/RD/AN5 RE1/WR/AN6 RE2/CS/AN7
15 16 17 18 23 24 25 26
R18
5
RCO/T1OSO/T1CKI RC1/T1OSI/CCP2 RC2/CCP1 RC3/SCK/SCL RC4/SDI/SDA RC5/SDO RC6/TX/CK RC7/RX/DT
33 34 35 36 37 38 39 40
2
4
MCLR/Vpp OSC1/CLKIN
1
5
1 13
Motor 24v c.c.
ULN2003
4
RBO/INT RB1 RB2 RB3 RB4 RB5 RB6 RB7
inclinatie -
4 7
U8
2 3 4 5 6 7
inclinatie +
16 15 14 13 12 11 10 9
O1 O2 O3 O4 O5 O6 O7 D
R VSS
RA0/AN0 RA1/AN1 RA2/AN2 RA3/AN3/VREF RA4/TOCKI RA5/AN4/SS
14
I1 I2 I3 I4 I5 I6 I7 Gnd
S VDD
OSC2/CLKOUT
1 2 3 4 5 6 7 8
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R20 10K
R19 10K
A K
Traductor rotatie
Citire inclinatie
R21 10K
Picture 7.
knob’, and the limits maximum and minimum slope are read by two micro switches. All the information regarding working modes, controls and functional keys are displayed on an LCD display with 4 rows and 20 columns. B. The ECG used is a BIOSET 6000, for which, from the numerous output leads, the D2 lead has been selected to be acquired in program. The output signal is buffered by an optical insulated amplifier and connected to the PCI 6024 E acquisition board via a CB68LP extension board, on pin AI2. The role of this insulated amplifier is to galvanic insulate the ECG from the equipment, for maintaining the requirements of EN 60601 standard, provided by ECG. The acquired signal is shown in picture 8.
Picture 8.
C. The respiratory gas analyzer is a continuous CAPNOLYZER analyzer, with a
measuring area for CO2 concentration of 0 to 10 %, corresponding to an output voltage of 0 to 1V. The analogue output is connected to the CB68LP extension board on pin AI0. D. The data acquisition system is created around a PCI 6024 E National Instruments acquisition board, with a CB68LP extension board. This board provides 12 bit successive approximation analogue to digital converter with a rate of 200k samples per second and 16 input in range of 10V or 20 V in nondifferential mode, or 8 input in range of +5V or +10V in differential mode. The interface with treadmill stress test equipment is made via an RS232c standard interface E. All these components of the equipment are controlled using the LabView® programming environment, which yielded a reliable and extremely user-friendly virtual instrument. The virtual instrument created in a LabVIEW® graphical programming environment has five functional blocks corresponding to the implemented functions.
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1. The first functional block is the signal acquisition block, which uses the time multiplexing signals method with constant sampling rate. Taking notice that the widest band among the input signals is the one of the ECG – the maximum is 50 Hz – a sampling frequency of 100 Hz is completely between the boundaries set by the Sampling Theorem. 2. The second functional block is destined to save the acquired data in a special file, which can later be accessed in order to post-process the data. 3. The third block has the purpose of real time data processing. This includes: For the ECG channel: the filtering of the signal (so that the noise created by the power supplies - 50Hz and the muscles do not interfere with the signal), the detection of the QRS complex and the calculation of the HR; For the %CO2 Capnolyser: the filtering of the input signal, the detection of the local maximum values (END TIDAL) and the minimum ones (INSPIR), and the calculation of the respiratory rate RR. The cardiac anaerobic threshold is detected from the filtered peak signal, using the correlation between HR and the peaks of the seven points Givens polynomial interpolating
signal technique, like in picture 9 a,b and c. For the velocity and slope channels: the input signals are used for displaying the treadmill’s actual value of velocity and slope. These signals also help determine the work rate done by the patient. 4. The functional block 4 is designed for graphical user interface. This comprises data patient input interface, physician name, and graphical drawings for ECG, %CO2, Respiration, HR, RR, MW, Time, Cardiac Anaerobic Threshold as output interface, as shown in picture 10.
Picture 10.
5. The fifth functional block is created for interfacing with the treadmill device. It comprises in RS232c serial interfaces for controlling the treadmill’s parameters in the computer connected mode. 4. Conclusion
Picture 9a.
Picture 9b.
Picture 9c.
This biomedical stress test equipment is quite useful for Clinical Stress Test Laboratories in order to become a daily used instrument with easy to use features and a friendly user interface. Furthermore, this biomedical stress test equipment comes as a reliable device for both strictly medicinal purposes and sports-related tests, in order to determine the degree of training for the top sportspersons.
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5. References. 1. K. SVEDAHL, B.R. MACINTOSH, Anaerobic Threshold: the Concept and Methods of Measurement, the Can. J. Appl. Physiol. (April, 2002). 2. Dr. H.-CH. HEITKAMP, Anaerobic Threshold: Methods And Reproductibility. 3. RILEY, M. S., and C. B. COOPER, Ventilatory and gas exchange responses during heavy constant work-rate exercise. Med. Sci. SportsExerc., Vol. 34, No. 1, 2002, pp. 98–104. 4. K.WASSERMAN, Anaerobic threshold and cardiovascular function, Monaldi Arch Chest Dis 2002; 58: 1, 1–5.
5. P.G. AGOSTONI, K. WASSERMAN, G.B. PEREGO, M. GUAZZI, G. CATTADORI, P. PALERMO, G. LAURI, G. MARENZI, Noninvasive measurement of stroke volume during exercise in heart failure patients. The Biochemical Society and the Medical Research Society. 6. W.L. BEAVER, K. WASSERMAN, B.J. WHIPP, A new method for detecting anaerobic threshold by gas exchange. J. Appl. Physiol. 60, 2020±2027 (1986). 7. T.M. MCLELLAN, I. JACOBS. Reliability, reproducibility and validity of the individual anaerobic threshold. Eur. J. Appl. Physiol. 67: 125-131, 1993.
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8. B. ILIE, O. SPATAR, R. MANITIU, The determination of the anaerobic threshold from breathing gases during effort test. ECIT 97 :45-48, 1997. 9. I. MANITIU. B. ILIE, Studiu privind determinarea pragului anaerobic la testul de efort din gazele respiratorii. Analele Universitatii Oradea, fascicola Electrotehnica 1997. 10. F.C. HOPPENSTEADT, C.S. PESKIN, Modelling And Simulation In Medicine And The Life Sciences. Springer-Verlag 2002 ISBN 0-38795072-9. 11. B. ILIE, Biomedical Signal Acquisition Equipment Using LabView® Environment. Sintes 11 519-522 2003 Craiova. 12. B. ILIE, Respiratory Gases Concentration Responses During Incremental Stress Test Exercise - 5th European Symposium on BioMedical Engineering ESBME 2006 - Patras, Ellas University of Patras.
Beriliu ILIE “Lucian Blaga” University of Sibiu “Hermann Oberth” Engineering Faculty Electrical and Electronical Department Email:
[email protected]
