Datex-Ohmeda S-5 Service Manual Datex S5

Datex-Ohmeda

Hemodynamic Modules

S/5TM PRESTN Module, M-PRESTN (Rev. 01)

S/5TM RESTN Module, M-RESTN (Rev. 01)

S/5TM PRETN Module, M-PRETN (Rev. 01)

Technical Reference Manual Slot

All specifications are subject to change without notice.

CAUTION: U.S. Federal law restricts this device to sale by or on the order of a licenced practitioner. Outside the USA, check local laws for any restriction that may apply.

		Document No. 8005571-1
		April 2004
	Datex-Ohmeda, Inc.	Datex-Ohmeda Division, Instrumentarium Corp.
	P.O. Box 7550, Madison	P.O. Box 900, FIN-00031
		DATEX-OHMEDA, FINLAND
	WI 53707-7550, USA
		Tel: [phone] Fax: [phone]
	Tel: [phone] Fax: [phone]
		www.datex-ohmeda.com
	www.us.datex-ohmeda.com	Instrumentarium Corp. All rights reserved.
	mailto:[e-mail]

			Table of contents
TABLE OF CONTENTS
S/5 Hemodynamic Modules
TABLE OF CONTENTS			i
TABLE OF FIGURES			iii
Introduction			1
1	Specifications		3
1.1	General specifications ..........................................................................................................................		3
1.2	Typical performance .............................................................................................................................		3
	1.2.1	NIBP ...........................................................................................................................................	3
	1.2.2	ECG.............................................................................................................................................	3
	1.2.3	Pulse oximetry .............................................................................................................................	4
	1.2.4	Temperature ................................................................................................................................	4
	1.2.5	Invasive blood pressure................................................................................................................	5
	1.2.6	Respiration..................................................................................................................................	5
1.3	Technical specifications........................................................................................................................		6
	1.3.1	NIBP ...........................................................................................................................................	6
	1.3.2	ECG.............................................................................................................................................	6
	1.3.3	Pulse oximetry .............................................................................................................................	6
	1.3.4	Temperature ................................................................................................................................	7
	1.3.5	Invasive blood pressure................................................................................................................	7
	1.3.6	Respiration..................................................................................................................................	7
2	Functional Description		8
2.1	Measurement principle.........................................................................................................................		8
	2.1.1	NIBP ...........................................................................................................................................	8
	2.1.2	ECG.............................................................................................................................................	8
	2.1.3	Pulse oximetry .............................................................................................................................	8
	2.1.4	Temperature ..............................................................................................................................	10
	2.1.5	Invasive blood pressure..............................................................................................................	10
	2.1.6	Respiration................................................................................................................................	10
2.2	Main components ..............................................................................................................................		11
	2.2.1	M-PRESTN/-RESTN/-PRETN modules .........................................................................................	11
	2.2.2	NIBP board................................................................................................................................	12
	2.2.3 ECG board in 12-lead measurement ...........................................................................................		15
	2.2.4	ECG filtering...............................................................................................................................	17
	2.2.5	STP board..................................................................................................................................	18
2.3	Connectors and signals ......................................................................................................................		23
	2.3.1 Module bus connector (on the NIBP board) .................................................................................		23
	2.3.2	Front panel connectors...............................................................................................................	25
	2.3.3 Test points on boards .................................................................................................................		26
3	Service Procedures		29
3.1	General service information ................................................................................................................		29
3.2	Service check.....................................................................................................................................		29
	3.2.1	Recommended tools..................................................................................................................	29
	3.2.2	Recommended parts..................................................................................................................	29
3.3	Disassembly and reassembly..............................................................................................................		39
	3.3.1	M-PRESTN/-RESTN/-PRETN modules .........................................................................................	39
3.4	Adjustments and calibrations .............................................................................................................		40

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	3.4.1	NIBP calibrations.......................................................................................................................	40
	3.4.2	Temperature calibration .............................................................................................................	42
	3.4.3	Invasive pressure calibration ......................................................................................................	42
4	Troubleshooting		43
4.1	Troubleshooting charts .......................................................................................................................		43
	4.1.1	NIBP .........................................................................................................................................	43
	4.1.2 NIBP error code explanation .......................................................................................................		46
	4.1.3	ECG ..........................................................................................................................................	47
	4.1.4	Pulse oximetry (SpO2) ................................................................................................................	47
	4.1.5	Temperature..............................................................................................................................	48
	4.1.6	Invasive blood pressure .............................................................................................................	49
	4.1.7	Impedance respiration...............................................................................................................	50
4.2	Troubleshooting flowcharts .................................................................................................................		51
	4.2.1 M-PRESTN module troubleshooting for NIBP parameter...............................................................		51
	4.2.2 M-PRESTN module troubleshooting for parameters ESTPR ...........................................................		52
5	Service Menu		53
5.1	NIBP service menu .............................................................................................................................		54
	5.1.2	NIBP demo menu.......................................................................................................................	55
	5.1.3	NIBP calibration menu ...............................................................................................................	56
	5.1.4 NIBP safety valve menu..............................................................................................................		57
	5.1.5 NIBP pulse valve menu ..............................................................................................................		58
	5.1.6	NIBP buttons/leds menu............................................................................................................	59
	5.1.7	NIBP pneumatics menu .............................................................................................................	60
	5.1.8	NIBP watchdog menu.................................................................................................................	61
	5.1.9	ECG service menu......................................................................................................................	62
	5.1.10	ECG setup menu....................................................................................................................	64
5.2	STP service menu...............................................................................................................................		65
	5.2.2	STP calibration menu .................................................................................................................	67
6	Spare Parts		68
6.1	Spare parts list...................................................................................................................................		68
	6.1.1 M-PRESTN rev. 01, M-RESTN rev. 01, M-PRETN rev. 01 ...............................................................		68
7	Earlier Revisions		71
APPENDIX A			73
Service Check Form			1

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		Table of contents
TABLE OF FIGURES
Figure 1 S/5 PRESTN Module, M-PRESTN...........................................................................................................		1
Figure 2 Absorption of infrared light in the finger probe parts layout and schematic diagram .................................		9
Figure 3 Front panel of M-PRESTN....................................................................................................................		11
Figure 4 NIBP board functional block diagram ..................................................................................................		12
Figure 5 NIBP pneumatics diagram ..................................................................................................................		14
Figure 6 12-lead ECG measurement block diagram ..........................................................................................		15
Figure 7 STP board block diagram ....................................................................................................................		18
Figure 8 Temperature measurement principle ...................................................................................................		19
Figure 9 Pressure measurement principle .........................................................................................................		20
Figure 10	Pulse oximetry measurement block diagram....................................................................................	21
Figure 11	Serial communication of NIBP board...............................................................................................	22
Figure 12	Serial Communication and Isolation of STP board............................................................................	22
Figure 13	Serial Communication and Isolation of ECG board ...........................................................................	22
Figure 14	Module bus connector (X1) pin layout .............................................................................................	23
Figure 15	ECG board connectors and test points.............................................................................................	26
Figure 16	NIBP board connectors and test points............................................................................................	27
Figure 17	STP board connectors and test points .............................................................................................	28
Figure 18	M-PRESTN module troubleshooting flowchart for NIBP Parameter.....................................................	51
Figure 19	M-PRESTN Module Troubleshooting Flowchart for Parameters ESTPR................................................	52
Figure 20	Exploded view of M-PRESTN Module ...............................................................................................	68

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INTRODUCTION

This Technical Reference Manual Slot provides information for the maintenance and service of the hemodynamic modules S/5 M-PRESTN/-RESTN/-PRETN. The modules are double width modules designed for use with S/5 monitors. Later in this manual modules may be referred to w/o the system name S/5 for simplicity.

Please also refer to Technical Reference Manual of the S/5 monitor for information regarding system specific information e.g. related documentation, conventions used, symbols on equipment, safety precautions, system description, system installation, interfacing, functional check and planned maintenance.

The M-PRESTN/-RESTN/-PRETN modules provide general hemodynamic parameters.

Auto	Start	Zero	Zero
On/Off	Cancel	P1	P2
NIBP		SpO2
ECG
	T1	P1
	T2	P2

NOTE: Do not use identical modules in the same monitor simultaneously.

The following modules are considered identical: M-ESTP/-EST/-ETP,

M-ESTPR/-ESTR/-ETPR, M-NESTPR/-NESTR/-NETPR, M-NE12STPR/-NE12STR/-NE12TPR M-PRESTN/M-RESTN/M-PRETN

Figure 1	S/5 PRESTN Module, M-PRESTN
Table 1	Options of S/5 hemodynamic modules
	Parameter	PRESTN	RESTN	PRETN
P	Two invasive blood pressures	•		•
R	Impedance respiration	•	•	•
E	ECG	•	•	•
S	Pulse oximetry	•	•
T	Two temperatures	•	•	•
N	NIBP	•	•	•

NOTE: 12-lead ECG measurement requires Display Controller, B-DISP or B-DISPX. Intended purpose (Indications for use)

The Datex-Ohmeda PRESTN module (model family M-PRESTN) and accessories are indicated for monitoring of hemodynamic parameters of all hospital patients. The hemodynamic parameters of the module comprise ECG including ST-segment and arrhythmia, Impedance respiration, NIBP, Temperature,SpO2 (including monitoring during conditions of clinical patient motion),and invasive blood pressure.

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Impedance respiration measurement is indicated for patients aged 3 and up. The NIBP measurement is indicated for patients who weigh 5kg (11 lb.) and up. This device is indicated for use by qualified medical personnel only.

Monitor software compatibility

Datex-Ohmeda PRESTN rev. 01 module is designed for use with Datex-Ohmeda monitors using software as follows:

AM: L-ANE01(A) or later versions;

CCM: S-00C01 rev. 10.5, S-00C02 rev. 10.5 or newer versions;

CAM: S-00A05 rev. 10.9, S-00A06 rev. 10.9, L-00A07 rev. 10.9, L-00A08 rev. 10.9 or newer versions and

CCCM: S-00C03 rev. 10.9, S-00C04 rev. 10.9 or newer versions.

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1	SPECIFICATIONS
1.1	General specifications
	Module size	75 ×180 ×112 mm
	W ×D ×H	3.0 ×7.1 ×4.4 in
	Module weight	0.7 kg / 1.5 lbs
	Power consumption	about 6 W
	Operation temperature	10 to 40 °C / 50 to 104 °F
1.2	Typical performance

1.2.1 NIBP

NOTE: Non-invasive blood pressure measurement is intended for patients weighing over 5 kg (11 lb.)

Oscillometric measurement principle.

Measurement range	adult	25 to 260 mmHg
	child	25 to 195 mmHg
	infant	15 to 145 mmHg
Pulse rate range accepted	30 to 250 bpm
Measurement interval	STAT (continuous 5 min), 1, 2.5, 3, 5, 10, 15, 30 and 60 min (1 h),
	2 and 4 h
Typical measuring time	adult	23 s
	infant	20 s
Initial inflation pressure	adult	170 ±10 mmHg
	child	150 ±10 mmHg
	infant	120 ±10 mmHg
Venous stasis	adult	40 ±5 mmHg / 2 min
	child	40 ±5 mmHg / 2 min
	infant	30 ±5 mmHg / 1 min
Cuff widths	please see User’s Guide

1.2.2 ECG

Lead selection, 12-lead ECG Lead selection, other modules Sweep speeds

DISPLAY FILTER

Diagnostic, 12-lead ECG Diagnostic, other modules

Monitoring

I, II, III, aVR, aVL, aVF, V1, V2, V3, V4, V5, V6 I, II, III, aVR, aVL, aVF, V

12.5, 25, 50 mm/sec

0.05to 150 Hz

0.05to 100 Hz

0.5to 30 Hz (-3 dB, with 50 Hz reject filter)

0.5to 40 Hz (-3 dB, with 60 Hz reject filter)

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ST filter	0.05 to 30 Hz (-3 dB, with 50 Hz reject filter)
	0.05 to 40 Hz (-3 dB, with 60 Hz reject filter)
HEART RATE FROM ECG
Range	30 to 250 bpm
Accuracy	±5 bpm or ±5 %, whichever is greater
Resolution	1 bpm
Update interval	5 s
Averaging time	10 s
ST LEVELS (in main software)
ST level range	-9 to +9 mm (-0.9 to +0.9 mV)
Resolution	0.1 mm (0.01 mV)
Averaging	calculated from 8 QRS
SYNCHRONIZATION
Direct ECG	analog output of ECG, 1 V/1 mV
Pacer	5 V and 0.5 to 2.5 ms pulse, < 30 ms after pacer peak
Defibrillator	5 V and 10 ms pulse, < 35 ms after R-point synchronization

1.2.3 Pulse oximetry

Measurement range	0 to 100 %
Calibration range	70 to 100 %
Accuracy1	100 to 70 %, ±2 digits
	±3 digits during clinical patient motion
	69 to 0 %, unspecified
Display resolution	1 digit = 1 % of SpO2
Display averaging time	20, 10 sec, beat-to-beat
Pulse beep pitch	varies with SpO2 level
The monitor is calibrated against functional oxygen saturation SpO2 func.
PULSE RATE FROM PLETH
Measurement range	30 to 250 bpm
Accuracy	30 to 100, ±5 bpm,
	100 to 250, ±5 %
Resolution	1 bpm
Display averaging	10 s
Adjustable pulse beep volume.
PLETH WAVEFORM
Scales	2, 5, 10, 20, 50 mod%, Auto
Start up scale is 20 mod% if AUTO is not selected to be the default setting.

1.2.4 Temperature

Measurement range	10 to 45 °C (50 to 113 °F)
Measurement accuracy	±0.1 °C (25 to 45.0 °C)

1 Accuracy is based on deep hypoxia studies with volunteered subjects during motion and non-motion conditions over a wide range of arterial blood oxygen saturations as compared to arterial blood CO-Oximetry.

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	±0.2 °C (10 to 24.9 °C)
Display resolution	0.1 °C (0.1 °F)
Temperature test	automatic (every 10 min)
Probe type	compatible with YSI 400 series
Single use sensors	±0.2 °C (25 to 45.0 °C)
	±0.3 °C (10 to 24.9 °C)

1.2.5 Invasive blood pressure

Measurement range	-40 to 320 mmHg
Measurement accuracy	±2 mmHg or ±5 %
Zero adjustment range	±150 mmHg
Calibration range	±20 %
Scales	upper limit is adjustable between 10 and 300 mmHg in steps of
	10. Lower limit is 10 % of selected upper limit below zero.
Sweep speed	12.5, 25, 50 mm/s
DIGITAL DISPLAY
Range	-40 to 320 mmHg
Resolution	±1 mmHg
WAVEFORM DISPLAY
Range	-30 to 300 mmHg
PULSE RATE FROM ARTERIAL PRESSURE
Measurement range	30 to 250 bpm
Resolution	1 bpm
Accuracy	±5 bpm or ±5 % whichever is greater

1.2.6 Respiration

NOTE: The respiration measurement is intended for patients over three years old

Measurement range	4 to 120 bpm
Accuracy	±5 bpm or ±5 %
Resolution	1 bpm
Averaging time	30 s
Update interval	10 s
RESPIRATION WAVEFORM
Sweep Speeds	6.25 mm/s and 0.625 mm/s

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1.3 Technical specifications

1.3.1 NIBP

Deflation rate, PR dep.	3 to 8 mmHg/s
Inflation time	20 to 185 mmHg, 1 to 5 s
Automatic software control, max. inflation pressure			±10 mmHg
	adult	280
	child	200	±10 mmHg
	infant	145	±5 mmHg
Over pressure limit, stops measurement after 2 seconds
	adult	320 mmHg
	child	220 mmHg
	infant	160 mmHg

The safety circuit limits the maximum cuff pressure to 320 mmHg in adult/child mode or 160 mmHg in infant mode. Independent timing circuit limits pressurizing (>15 mmHg) time to 3 minutes maximum in adult/child mode, and 90 seconds at (>5mmHg ) in infant mode.

Zeroing to ambient pressure is done automatically.

Inflation pressure is adjusted according to the previous systolic pressure, typically 40 mmHg above. If the systolic pressure is not found, inflation pressure is increased typically 50 mmHg.

Max. measurement time	adult	120 s
	child	120 s
	infant	75 s
Pressure transducer accuracy is better than ±3 mmHg or ±2 % whichever is greater.
Max. error ±4 mmHg.
Protection against electrical
shock	Type BF defibrillation proof

1.3.2 ECG

Defibrillation protection	5000 V, 360 J
Recovery time	5 s
Input impedance	>2.5 MΩ(10 Hz)
CMRR	≥95 dB (ST)
System noise	<30 µV (p-p, RTI)
Allowable offset	±800 mVDC
Gain range	0.2 to 5.0 cm/mV
Pacemaker pulse detection	2 to 700 mV, 0.5 to 2 ms pulses
Protection against electrical
shock	Type CF defibrillator proof

1.3.3 Pulse oximetry

Protection against electrical
shock	Type BF defibrillation proof

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Filter

Zero set accuracy Calibration resolution Zero time

Protection against electrical shock

S/5 M-PRESTN Modules

1.3.4 Temperature

Measurement accuracy	±0.1 °C (25.0 to 45.0 °C)
	±0.2 °C (10.0 to 24.9 °C)
Protection against electrical
shock	Type CF defibrillation proof

NOTE: The accuracy of the measurement may be different from the specified, depending on transducer/probe used. Please refer to the transducer/probe specification.

1.3.5 Invasive blood pressure

DIGITAL DISPLAY AVERAGING

Digital displays Art and P1 are averaged over 5 seconds and updated at 5 seconds intervals. All other pressures have respiration artifact rejection.

Accuracy ±5 % or ±2 mmHg, whichever is greater Transducer and input sensitivity

5 µV/V/mmHg, 5 VDC, 20 mA max current

0 to 4 - 22 Hz adjustable

±1 mmHg

±1 mmHg less than 15 s

Type CF defibrillation proof

NOTE: The accuracy of the measurement may be different from the specified, depending on transducer/probe used. Please refer to the transducer/probe specification.

1.3.6 Respiration

Excitation frequency,
12-lead ECG	31.25 kHz
Breath detection	automatic, range 0.3 to 6 Ωmanually adjustable minimum
	detection: 0.2, 0.4, 0.6, 0.8, 1.0
Input dynamic range	0.2 to 32 Ω
Input impedance range	100 to 5000 Ω
Respiration Rate	min. 4 bpm
	max. 120 bpm
Lead off detection	>3 MΩ

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2 FUNCTIONAL DESCRIPTION

2.1 Measurement principle

2.1.1 NIBP

NIBP (Non-Invasive Blood Pressure) is an indirect method for measuring blood pressure.

The NIBP measurement is performed according to the oscillometric measuring principle. The cuff is inflated with a pressure slightly higher than the presumed systolic pressure, and deflated at a speed based on the patient’s pulse, collecting data from the oscillations caused by the pulsating artery. Based on these oscillations, values for systolic, mean, and diastolic pressures are calculated.

The following parts are necessary for the NIBP measurement:

•M-PRESTN/-RESTN/-PRETN module

•twin hose (adult or infant model)

•blood pressure cuffs (various sizes)

2.1.2 ECG

Electrocardiography analyzes the electrical activity of the heart by measuring the electrical potential produced with electrodes placed on the surface of the body.

ECG reflects:

•electrical activity of the heart

•normal/abnormal function of the heart

•effects of anesthesia on heart function

•effects of surgery on heart function

See the User's Guide or the User’s Reference Manual for electrodes positions and other information.

2.1.3 Pulse oximetry

A pulse oximeter measures the light absorption of blood at two wavelengths, one in the near infrared (about 900 nm) and the other in the red region (about 660 nm) of the light spectrum. These wavelengths are emitted by LEDs in the SpO2 probe, the light is transmitted through peripheral tissue and is finally detected by a PIN-diode opposite the LEDs in the probe. The pulse oximeter derives the oxygen saturation (SpO2) using an empirically determined relationship between the relative absorption at the two wavelengths and the arterial oxygen saturation SaO2.

In order to measure the arterial saturation accurately, pulse oximeters use the component of light absorption giving variations synchronous with heart beat as primary information on the arterial saturation.

A general limitation of pulse oximetry is that due to the use of only two wavelengths only two hemoglobin species can be discriminated by the measurement.

The modern pulse oximeters are empirically calibrated either against fractional saturation SaO2frac;

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	SaO2frac =			HbO2		Formula 1
		HbO2 +Hb +Dyshemoglobin
	or against functional saturation SaO2func;
	SaO2func =		HbO2			Formula 2
			HbO2 +Hb

Functional saturation is more insensitive to changes of carboxyhemoglobin and methemoglobin concentrations in blood.

The oxygen saturation percentage SpO2 measured by the Datex-Ohmeda module is calibrated against functional saturation SaO2func. The advantage of this method is that the accuracy of SpO2 measurement relative to SaO2func can be maintained even at rather high concentrations of carboxyhemoglobin in blood. Independent of the calibration method, pulse oximeters are not able to correctly measure oxygen content of the arterial blood at elevated carboxyhemoglobin or methemoglobin levels.

Plethysmographic pulse wave

The plethysmographic waveform is derived from the IR signal and reflects the blood pulsation at the measuring site. Thus the amplitude of the waveform represents the perfusion.

Pulse rate

The pulse rate calculation is done by peak detection of the plethysmographic pulse wave. The signals are filtered to reduce noise and checked to separate artifacts.

Probe

The standard probe is a finger clamp probe which contains the light source LEDs in one half and the photodiode detector in the other half. Different kinds of probes are available from Datex-Ohmeda.

SpO2 sensor connector

SpO2 sensor cable

		6	GND
	Emitter	IRED
		7	ILED	of infrared.vsd
	RED	4	GND
		5	DEF_A
		8		_
			IS	PRSTN absorption
		9	DET_C
	Detector

Figure 2	Absorption of infrared light in the finger probe, parts layout and schematic
	diagram

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2.1.4 Temperature

The temperature is measured by a probe whose resistance varies when the temperature changes, called NTC (Negative Temperature Coefficient) resistor.

The resistance can be measured by two complementary methods:

•Applying a constant voltage across the resistor and measuring the current that flows through it

•Applying a constant current through the resistor and measuring the voltage that is generated across it.

In Datex-Ohmeda modules the two methods are combined in the form of a voltage divider. The NTCresistor is connected in series with a normal resistor and a constant voltage is applied across them. The temperature dependent voltage can be detected at the junction of the resistors, thus producing the temperature signal from the patient. The signal is amplified by analog amplifiers and further processed by digital electronics.

2.1.5 Invasive blood pressure

To measure invasive blood pressure, a catheter is inserted into an artery or vein. The invasive pressure setup, consisting of connecting tubing, pressure transducer, an intravenous bag of normal saline all connected together by stopcocks, is attached to the catheter. The transducer is placed at the same level with the heart, and is electrically zeroed.

The transducer is a piezo-resistive device that converts the pressure signal to a voltage. The monitor interprets the voltage signal so that pressure data and pressure waveforms can be displayed.

2.1.6 Respiration

Impedance respiration is measured across the thorax between ECG electrodes. The respiration signal is made by supplying current between the electrodes and by measuring the differential current from the electrodes. The signal measured is the impedance change caused by breathing. From these impedance changes, respiration rate is calculated, and the respiration waveform is displayed on the screen.

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2.2 Main components

2.2.1 M-PRESTN/-RESTN/-PRETN modules

Auto	Start	Zero	Zero
On/Off	Cancel	P1	P2
NIBP		SpO2
ECG
	T1	P1
	T2	P2
Figure 3		Front panel of M-PRESTN

The M-PRESTN, M-RESTN, and M-PRETN modules contain three main PC boards, the STP board, the ECG board, and the NIBP board. They work independently. Each of these has their own processor and software in the processor flash memory.

There are two small boards, the SP input and the ECG input board attached to the front panel of the module. The front panel has seven connectors and four keys. The connectors are two for temperature measurement, two for invasive blood pressure measurement, one for ECG, one for NIBP, and one for SpO2 measurement. The keys are for NIBP Auto On/Off, NIBP Start/Cancel, P1 zero, and P2 zero.

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2.2.2 NIBP board

PATIENT AND NIBP CUFF

NIBP TUBING

NIBP CONNECTOR

NIBP PNEUMATICS

PRESSURE SENSORS		DRIVERS FOR PUMP &
		VALVES

NIBP CONTROL KEYS

MAIN CPU		SAFETY CPU

NV MEMORY

RS 485 COMMUNICATION			POWER SUPPLY

NIBP BLOCK DIAGRAM

MODULE BUS CONNECTOR

Figure 4

NIBP board functional block diagram

Signal processing

Two signals from the pressure transducers are amplified and sent to the A/D converter. After the converter, digitized signals are sent to the microprocessor for data processing.

The NIBP board is controlled with a H8/3052 microprocessor at 16 MHz oscillator frequency.

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Memory

NIBP program memory (processor flash memory) size is 512k ×8. The processor has 4 kBytes RAM and there is also an external RAM memory the size of which is 128k x 8. Variable values of the NIBP measurement are stored into the external RAM. The EEPROM size is 512 x 8 and it is used to store the calibration values for the pressure transducers, the pulse valve constants gained during measurements, the PC board identification, and module serial number.

Software control

Software controls valves and pump. In addition to the individual on/off signals for each component there is a common power switch for the valves and the pump that can be used at pump/valve failures.

In addition to external RS485 reset line the microprocessor system is equipped with its own powerup reset. See the section in the ECG board’s description: “RS485 communication”

Safety circuit

The NIBP board is equipped with an independent safety circuit to disconnect supply voltages from the pump and the valves if the cuff has been pressurized longer than the preset maximum measurement time, or if the pressure of the cuff is inflated over the specified pressure limit. The maximum measurement time values and pressure limits for different measurement modes have been specified in the technical specification section of this manual.

Pneumatics

Pneumatics of PRESTN module has the following parts:

•Intake air filter; for preventing dust and other parts to enter the air pump and the valves.

•Air pump: for pumping the measuring pressure of the cuff.

•(Pulse) Valve; for producing a linear pressure fall (bleeding) in order to measure the blood pressure of the patient.

Note that there has been used also two other names Valve and Set valve to designate pulse valve in service menu.

•Safety valve; The safety valve has been intended to be used for deflating the cuff in single fault case, i.e. to prevent too long measurement time or too high inflation pressure of the cuff.

Note that there has been used also Exh2 valve to designate the Safety valve in service menu.

•Main pressure sensor; for measuring the pressure of the blood pressure cuff and the pressure fluctuations caused by arterial wall movement.

•Safety pressure sensor for detection of cuff hose type, cuff loose, cuff occlusion situations etc.and recognising the pressure sensor fault.

•Cuff connector; for connecting the cuff.

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Safety pressure sensor

Cuff connector

Proportional valve

Air pump

Dump valve

Main pressure sensor

Intake air filter

NIBP_pneum_diagr.vsd

Figure 5

NIBP pneumatics diagram

Power supply section of the NIBP board

All connections are established via 25-pin connector (D-type, female). The module needs +15 V (dirty) power supply to operate. The supply voltage (+15V) is generated in the power supply section of the S/5 monitor. The other voltages needed for the operation of the NIBP measurement are made on the NIBP board.

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2.2.3 ECG board in 12-lead measurement

The 12-lead ECG measurement consists of the elements shown in Figure 6. All functions are located in the ECG board except the ECG input unit .

PATIENT AND ECG ELECTRODES

ECG CABLE

-ECG LEAD SET

-ECG TRUNK CABLE

ECG INPUT UNIT

-ECG CONNECTOR

-INPUT PROTECTION RESISTORS

INPUT PROTECTION DIODES FOR ECG & RESPIRATION MEASUREMENT

INPUT FILTERING FOR ECG & RESPIRATION MEASUREMENTS

RESPIRATION		RESPIRATION		ECG PREAMPLIFIERS &		LEADS OFF & PACER &
MEASUREMENT		MEASUREMENT CURRENT				DEFIBRILLATION
				RLD CIRCUIT
AMPLIFIERS		SUPPLY				DETECTION

BASELINE

RESTORATION

ECG CPU

NV MEMORY

	RS 485 COMMUNICATION				POWER SUPPLY
	ISOLATION				ISOLATION

MODULE BUS CONNECTOR

ECG BLOCK DIAGRAM

Figure 6

12-lead ECG measurement block diagram

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ECG input unit

The ECG input unit consists of the front panel connector and the ECG input connector board with the high voltage protection resistors. The connector for the 12-lead ECG cable is a green 11-pin rectangle shaped connector.

Input protection and filtering

The input protection is implemented with high voltage protection resistors in the ECG input unit and with protection diodes in the ECG board. The input filtering for ECG measurement is done with passive RC filtering.

ECG preamplifiers

The buffer amplifiers are used for each lead. The “Leads off” detection is implemented by measuring the output level of the input buffer amplifiers with A/D converter of CPU. The ECG signals are measured using differential amplifiers.

ECG amplifiers and baseline restoration

The function of the ECG amplifiers and baseline restoration is to amplify the signal and to restore the baseline of the signal in the middle of the display after the change of the signal level e.g. after the change of the DC offset voltage.

Pacer detection

Pacer detection has been made by using three slew rate detector circuits. The pacer detection amplifiers have been realized at the front of the slew rate detectors independently from the ECG measuring channels.

Respiration impedance supply

The 31.25 kHz sine wave generator is used as the respiration measurement signal supply. Analog switches are used for connecting the sine wave to the ECG leads to be measured.

Respiration impedance amplifiers

Buffer amplifiers are used in respiration measurement. Analog switches are used for selecting the measurement leads. There are also additional amplifiers for increasing the respiration signal gain. When ECG measurement is 5/12-lead, the respiration measurement is always done between R and F, independently on the ECG lead selection. When ECG measurement is 3-lead, then the respiration measurement is done at the same lead as the ECG measurement (I, II or III).

ECG CPU

The CPU is a 16 bit H8/3052 single-chip microcomputer. It contains 128 kbytes of flash memory and 4 kbytes of RAM. The clock frequency is 16 MHz.

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RS485 communication

The communication to the CPU board of the monitor uses RS485 protocol. The RS485 driver circuits are optically isolated from the processor of the module. PWM signal is used for direct ECG signal. Direct ECG signal is available from the X2 connector of the UPI board or from the PT module.

Power supply

The ECG board has a driver controlled half bridge switching power supply with 5 kV isolation. The supply voltages have been regulated with linear regulators.

2.2.4 ECG filtering

The S/5 monitors have three ECG filtering modes:

MONITORING	0.5 to 30 Hz (with 50 Hz reject filter)
	0.5 to 40 Hz (with 60 Hz reject filter)
DIAGNOSTIC 12-lead ECG	0.05 to 150 Hz
ST FILTER	0.05 to 30 Hz (with 50 Hz reject filter)
	0.05 to 40 Hz (with 60 Hz reject filter)

The purpose of filtering is to reduce high frequency noise and low frequency (e.g. respiratory) movement artifacts.

Monitor filter is used in normal monitoring. Diagnostic filter is used if more accurate diagnostic information is needed. ST filter gives more accurate information of ST segment, but reduces high frequency noise.

The high-pass filters 0.5 Hz and 0.05 Hz are done with software. The monitor sends a command to the hemodynamic module determining which of the corner frequencies 0.5 Hz or 0.05 Hz is to be used.

The 50 Hz and 60 Hz reject filters are both low-pass filters with zero at 50 Hz or 60 Hz correspondingly. They are software based filters used for the mains supply filtering. With these filters the 3 dB value for low-pass filter is 30 Hz or 40 Hz.

In diagnostic mode the upper frequency is 150 Hz and it is limited by software.

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2.2.5 STP board

PATIENT AND SpO2 PROBE		PATIENT AND TEMPERATURE		PATIENT AND INVASIVE CANNULA
		SENSOR		OR CATHETER
SpO2 TRUNK CABLE		TEMPERATURE CONNECTOR		FLUSHING KIT & INVASIVE
				PRESSURE SENSOR WITH DOME
SpO2 CONNECTOR		INPUT PROTECTION CIRCUITRY		INV.PRESSURE CONNECTOR

SpO2 PROBE RECOGNITION & LED

DRIVE SELECTION MATRIX

	TEMPERATURE	SENSOR	INV: PRESSURE	SENSOR SIGNAL
		SIGNAL
	MEASUREMENT		MEASURE MENT	VOLTAGE
		CURRENT
	AMPLIFIER		AMPLIFIER	SOURCE
		SOURCE

SpO2 LED DRIVE

SpO2 AMPLIFIER

A/D CONVERSION

STP CPU

NV MEMORY

	RS 485 COMMUNICATION				POWER SUPPLY
	ISOLATION				ISOLATION

MODULE BUS CONNECTOR

STP BLOCK DIAGRAM

Figure 7

STP board block diagram

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Microprocessor unit

The CPU is a 16 bit H8/3052 single-chip microcomputer. It contains 128 kbytes of flash memory and 4 kbytes of RAM. The clock frequency is 16 MHz.

High speed I/O is used to obtain pulse control sequence necessary for pulse oximetry measurement. Timing for the clock is from the oscillator.

Temperature measurement unit

The NTC-resistor value in the probe depends on the patient’s temperature. It is measured with the following principle described below.

The constant current source is supplied about 7µA current through the temperature sensor (YSI 400-series NTC resistor). The constant current is caused a voltage over the temperature sensor (NTC resistor). The voltage over the temperature sensor is amplified in a differential amplifier stage. The amplified voltage is transferred to a controller of the STP board through an A/D converter.

Defibrillation/ESD protection	constant
	current
resistors and diodes	source
100k

Differential

10k

amplifier

0

0

To A/D

0C:7k36

Temperature

15C:3k54

d/dt

converter

25C:2k53

0

sensor

38C:1k30

45C: 984

0

10k

100k

temp_meas_principle.vsd

Figure 8

Temperature measurement principle

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Invasive blood pressure measurement unit

An isolated +5 V voltage is supplied to the pressure transducer. The differential voltage, which depends on the pressure and the supplied voltage, is calculated from the bridge connection (see the formula below).

Uout = Uin ×pressure ×5 V, where Uin is 5 VUout = 25 V ×pressure [mmHg]

Pressure amplification is realized in the instrumentation amplifier. The gain of the amplifier is set to keep the level of the signal transferred to A/D converter within the measurement range even when there are circumstantial offsets or offsets caused by the transducer. There is a filter before the amplifier to attenuate high frequency disturbances.

Vin	Pressure
	transducer
	Vout	Input
		Filter

Instrumentation

amplifier

G

to AD converter principle.vsd _meas _pressure

Figure 9

Pressure measurement principle

Pulse oximetry measurement section

LED control signals

The D/A converters of the microcontroller on STP board set the LED intensity adjustment values for the infraredand red LEDs of SpO2 probe. The microcontroller on the STP board switches ON ( to the adjusted intensity ) and OFF the SpO2 probe LEDs according to the predetermined sequence.

LED driving circuit

Differential amplifiers measure the LED currents (LED current indication) of SpO2 probe over the shunt resistors placed in the LED current paths. The LED driving voltages (LED voltage indication) are measured from the driver circuitry. The LED driving circuits also have MOSFET transistor matrix to enable the use of different probe configurations.

Measured signal preamplification

The preamplifier is bipolar/single-ended current-to-voltage converter with adjustable gain. A higher gain is used for measuring thin tissue. The preamplification stage has also ambient light reduction and second amplifier stage.

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