Nellcor N-400 User manual

SERVICE MANUAL

NELLCOR PURITAN BENNETT

Fetal Oxygen Saturation Monitor (Fetal Pulse Oximeter)

N-400

To contact Nellcor’s representative: In the United States, call 1-800-NELLCOR or 925 463-4000; outside the United States, call

Nellcor Puritan Bennett’s local representative.

United States Office

Nellcor Puritan Bennett Incorporated 4280 Hacienda Drive Pleasanton, California 94588 U.S.A. Tel. 925 463-4000 1-800-635-5267

European Office

Nellcor Puritan Bennett BV Hambakenwetering 1 5231 DD ’s-Hertogenbosch The Netherlands Tel. +31.73.6485200

To obtain information about a warranty, if any, for this product, contact Nellcor Puritan Bennett Technical Services or your local Nellcor Puritan Bennett representative.

NELLCOR PURITAN BENNETT is a trademark of Nellcor Puritan Bennett Incorporated.

Covered by one or more of the following U.S. Patents (and foreign equivalents): 4,621,643; 4,653,498; 4,700,708; 4,770,179; 4,802,486; 4,869,254; 4,911,167; 4,928,692; 4,934,372; 5,228,440; and 5,247,932.

CONTENTS

Section 1: Introduction

1.1 Manual Overview........................................................................... 1-1

1.2 Warnings, Cautions, And Notes .................................................... 1-1

1.3 Device Description......................................................................... 1-1

1.4 Routine Maintenance..................................................................... 1-2

1.5 Cleaning ........................................................................................ 1-3

1.6 Spare Parts ................................................................................... 1-3

Section 2: Troubleshooting

2.1 Introduction.................................................................................... 2-1

2.2 Error Codes ................................................................................... 2-1

2.3 Troubleshooting Guide .................................................................. 2-4

Section 3: Packing for Shipment

3.1 General Instructions ...................................................................... 3-1

3.2 Repacking In Original Carton ........................................................ 3-1

3.3 Repacking In A Different Carton.................................................... 3-1

Section 4: Specifications

4.1 Performance .................................................................................. 4-1

4.2 Controls ......................................................................................... 4-2

4.3 Alarms ........................................................................................... 4-2

4.4 Audio Pulse ................................................................................... 4-2

4.5 Response Modes .......................................................................... 4-2

4.6 ECG ............................................................................................... 4-2

4.7 Switches ........................................................................................ 4-2

4.8 Data I/O ......................................................................................... 4-3

4.9 Connectors .................................................................................... 4-3

4.10 Electrical ........................................................................................ 4-3

4.11 Physical ......................................................................................... 4-4

4.12 Environmental ............................................................................... 4-4

Technical Support

5.1 Theory of Operation ...................................................................... 5-1

5.2 Block Diagram Analysis................................................................. 5-4

5.3 Circuit Descriptions........................................................................ 5-7

5.5 Schematic, Assembly, and Block Diagrams .................................. 5-36

iii

SECTION 1: INTRODUCTION

1.1 Manual Overview

1.2 Warnings, Cautions, and Notes

1.3 Device Description

1.4 Routine Maintenance

1.5 Cleaning

1.6 Spare Parts

1.1 MANUAL OVERVIEW

This manual contains information about servicing the N-400 Fetal Oxygen Saturation Monitor. Only qualified service personnel should service this product. Before servicing the device, read the operator’s manual carefully for a thorough understanding of operation.

1.2 WARNINGS, CAUTIONS, AND NOTES

This manual uses three terms that are important for proper operation of the device: Warning, Caution, and Note.

1.2.1 Warning

A warning precedes an action that may result in injury or death to the patient or user. Warnings are boxed and highlighted in boldface type.

1.2.2 Caution

A caution precedes an action that may result in damage to, or malfunction of, the device. Cautions are highlighted in boldface type.

1.2.3 Note

A note gives information that requires special attention.

1.3 DEVICE DESCRIPTION

The NELLCOR PURITAN BENNETT® Fetal Oxygen Saturation Monitor, model N-400, measures functional oxygen saturation of arterial hemoglobin (FSpO2) and pulse rate in fetuses. The N-400 monitors fetal FSpO2 and pulse rate noninvasively to the fetus during labor and delivery, with measurements updated at each qualified pulse.

The system consists of three components: N-400 Fetal Oxygen Saturation Monitor, N-400 Fetal Patient Module, and a NELLCOR PURITAN BENNETT Fetal Oxygen Sensor. The N-400 also provides analog and digital outputs for external data recording devices. The N-400 Fetal Patient Module provides initial amplification of the fetal oximetry signal. This patient module has a connector for the sensor and a cable that connects into the N-400 front panel.

1-1

Section 1: Introduction

The N-400 provides immediate use after power-up, without need for operator calibration. Features include:

• Automatic self-test and error messages.

• Automatic oximetry calibration.

• Visible oximetry displays.

The N-400 provides the operator with the capability to tailor the operating parameters for specific clinical applications.

Capabilities include:

• Audible alarm (default state is OFF), with adjustable alarm volume.

• Operator-configured visible and audible low-saturation alarm limit (the default alarm limit is set to zero).

• An audible indicator for both FSpO2 and pulse rate: a tone signals each pulse and its pitch varies with changes in FSpO2. This audible indicator has an adjustable volume. (The default state of this feature is OFF.)

• Two oximetry operating modes that change measurement averaging time to suit varied clinical applications.

• Analog output of FSpO2 saturation and pleth waveform data.

• Digital output of FSpO2 saturation, pulse rate, pleth, and signal quality data.

1.4 ROUTINE MAINTENANCE

Nellcor Puritan Bennett recommends the following inspection, performance and safety checks once every two years. These checks should be performed by qualified service personnel.

Inspection Checks:

• Inspect the monitor for any mechanical and/or functional damage

• Inspect the safety relevant labels for legibility

• Inspect the fuse to verify compliance with the rated current and breaking

characteristics

Performance Checks:

• Verify that the alarms function as described in the Operator’s Manual

• Using the FSpO2 Tester, Model SRC-4, verify the operation of the

monitor by following the instructions in the SRC-4 Technical Manual, Guide to Operation.

1-2

1.5 CLEANING

1.6 SPARE PARTS

Section 1: Introduction

Safety Checks: Using a Safety Analyzer, check the following limits:

• Ground Wire Resistance to a limit of ≤ 0.2 Ohms

• Enclosure Leakage Current in normal conditions to a limit of ≤100µAmps

• Patient Leakage Current in normal conditions to a limit of ≤20µAmps

with Patient Module connected

• Patient Leakage Current in a single fault condition, Mains voltage on the applied part, to a limit of ≤100µAmps

CAUTION: Do not immerse the N-400 in liquid or use caustic or abrasive cleaners.

To clean the surface of an N-400, dampen a cloth with a commercial nonabrasive cleaner and wipe all monitor surfaces. Do not spray or pour liquid directly on the N-400 or its accessories. Do not allow any liquid to come in contact with the power connector, fuse holder, or switches. Do not allow any liquid to penetrate switches, connectors, or openings in the chassis.

Contact Nellcor Puritan Bennett Technical Services or your local Nellcor Puritan Bennett representative to obtain information about the availability of spare parts for the N-400.

1-3

SECTION 2: TROUBLESHOOTING

2.1 Introduction

2.2 Error Codes

2.3 Troubleshooting Guide

2.1 INTRODUCTION

This section contains instrument indications, and trouble symptoms and probable causes. There are two primary symptoms of malfunctions: those that cause the instrument to not operate at all, and those that cause erratic behavior. The first kind is a result of internal failures; the second can be caused by external factors, such as improper sensor use or external electrical interference, as well as by internal failures. All internal failure service needs must be performed by an authorized Nellcor Puritan Bennett Service Center. Contact Nellcor Puritan Bennett Technical Services or your local Nellcor Puritan Bennett representative for assistance.

2.2 ERROR CODES

Table 1 lists error codes, their probable cause, and recommended action.

ERROR CODE PROBABLE CAUSE INSTRUCTIONS

ERR 1 Line Voltage selection incorrect; or

RAM chip failure.

ERR 2 ROM Failure; Defective Memory Contact NPB Technical Services

ERR 3 Defective display segment or

indicator

ERR 4 Clock battery failure. Will occur

during the installation of new PROMs.

ERR 5 Communications failure. UART

failure during Power On Self Test (POST).

ERR 6 Clock battery failure. May occur

during the installation new PROMs.

ERR 7 A front panel button is stuck or held

in position during the monitor POST.

ERR 8 Line Voltage selection is not the

same as the AC supply voltage.

ERR 9 Memory Failure or a Processor

80C186 problem.

Table 1: Error Codes

If changing the Line Voltage selection does not correct the error, contact NPB Technical Services.

The error can be cleared by pressing any front panel button. Contact NPB Technical Services.

While installing new PROMs, the error can be cleared by pressing any front panel button. If the error occurs in the field, contact NPB Technical Services.

The error can be cleared by pressing any front panel button. In the field, contact NPB Technical Services.

While installing new PROMs, the error can be cleared by pressing any front panel button. If the error occurs in the field, contact NPB Technical Services.

Check all front panel buttons for proper operation. If the error does not clear, contact NPB Technical Services.

Change line voltage selection.

Contact NPB Technical Services

2-1

Section 2: Troubleshooting

Table 1: Error Codes (continued)

ERROR CODE PROBABLE CAUSE INSTRUCTIONS

ERR 10 Memory Failure or a Processor

80C186 problem.

ERR 119 ROM run-time failure (Memory

Failure)

ERR 120 RAM run-time failure (Memory

Failure)

ERR 121 Clock Failure. The error can be cleared by pressing

ERR PB Internal communications problem. Turn the ON/Standby Switch to

ERR SEN The sensor is not compatible with

the system configuration.

Contact NPB Technical Services

Turn the ON/Standby Switch to Standby and the mains ON/OFF switch to OFF. Turn back to ON after 5 seconds. If error is not cleared, contact NPB Technical Services.

any front panel button. In the field, contact NPB Technical Services.

Standby and the mains ON/OFF switch to OFF. Turn back to ON after 5 seconds. If error is not cleared, contact NPB Technical Services.

Replace with the correct sensor.

The error codes in Tables 2 and 3 are for information use only by NPB Technical Services personnel and are divided into two categories.

INFORMATIONAL—The instrument continues to operate, but does not post numbers. The ERR code may be cleared with the push of any front panel button and it would be desirable for the clinician to record the ERR number for our information.

OPERATIONAL—The instrument stops posting numbers, shuts down the LEDs and must be reset by turning the Mains AC Switch OFF and then ON again after approximately 5 seconds. It is also desirable to record the ERR number for information purposes.

Table 2: Informational—Service Only

ERROR CODE PROBABLE CAUSE INSTRUCTIONS

ERR 122 Software ring buffer supporting

external communications is filled. Data may be discarded.

Slow running Processor clock, or a memory problem, or an internal software error. See above for clearing of error.

2-2

Section 2: Troubleshooting

Table 3 - Operational—Service Only

ERROR CODE PROBABLE CAUSE INSTRUCTIONS

ERR 101, 201,

301, 401, 501,

802

ERR 102, 203,

302, 402, 503

ERR 103, 104,

105, 205, 305, 404, 505, 601,

801

ERR 106, 206,

306, 406, 506

ERR 107, 207,

307, 407, 507

ERR 108, 208,

308, 408, 508

ERR 109 RTDIAG: Ping Failure S/W Failure

ERR 110 RTDIAG: Told to halt via IPC

ERR 112 RTDIAG: Interrupt vector error See ERR 101

ERR 113 POST: Bad A/D start A/D converter problem

ERR 114 RTDIAG: Stack check S/W Failure or may be a bad

ERR 115 Non-volatile log error in the Header

ERR 116 Non-volatile log error in the Data S/W Failure or Smartwatch

ERR 117 Release of a long message buffer S/W Failure

ERR 202 IPC Release Long Message Buffer See ERR 101

ERR 209, 511 Invalid Parameter See ERR 101

ERR 210 Invalid Offset See ERR 101

ERR 211 No Ping Message See ERR 101

ERR 409, 502 Release Long Message Buffer See ERR 101

ERR 512 Invalid SpO2 Mode See ERR 101

ERR 602 TIMER_INV_MSGINIT S/W Error

ERR 603 TIMER_INV_RESTART S/W Error

ERR 604 TIMER_INV_CANCEL S/W Error

ERR 701 IPC Send Error See ERR 101

ERR 702 IPC Get Long Message Buffer See ERR 101

ERR 703 Internal programming error in

ERR 704 Invalid data to a case statement.

ERR 705 A/D Overrun A/D chip failure

ERR 803 IPC Release Long Message Buffer,

IPC Get Long Message Buffer, Internal Error, Buffer Starvation

IPC Invalid Message See ERR 101

IPC Send See ERR 101

IPC Reply See ERR 101

IPC Queue Create See ERR 101

IPC Receive See ERR 101

message (test hook)

format

devices programming

Default executed.

Internal Error, corrupt pointer

Slow running Processor clock, or a memory problem, or an internal software error. See above for clearing of error.

S/W Failure

memory chip

S/W Failure or Smartwatch

S/W Error

2-3

Section 2: Troubleshooting

Table 3 - Operational—Service Only (continued)

ERROR CODE PROBABLE CAUSE INSTRUCTIONS

ERR 804 IPC Routing Problem - Destination

ERR 901 Interrupt occurred SYS_DIVIDE_0 S/W Error

ERR 903 Interrupt occurred

ERR 904 Interrupt occurred

ERR 905 Assert macro SYS_ASSERT S/W Error

ERR 906 Internal coding error in IPC

ERR 907 RTXC returned an error SYS_RTXC S/W Error

ERR 908 Non-volatile log memory integrity

ERR 999 Could not convert the major and

2.3 TROUBLESHOOTING GUIDE

CPU incorrect

SYS_INVALID_OPCODE

SYS_INVALID_INT

SYS_XRECV_TIMEOUT

failure

minor error codes to a number between 0 and 998

S/W Error

H/W Error; Bad memory or memory controller

S/W Error

H/W Error; Smartwatch failure.

S/W Error

The following paragraphs discuss potential difficulties and suggestions for resolving them. Refer to the Sensor Quick Guide and the Sensor Placement Guide for complete instructions on sensor use. If the difficulty persists, contact Nellcor Puritan Bennett Technical Services or your local Nellcor Puritan Bennett representative.

Potential Problems and Resolutions

1. N-400 does not turn on (that is, after the front panel ON/STANDBY switch is placed in the ON position).

• Check that the mains (AC) ON/OFF switch is set to ON.

• Check mains (AC) connection. Check that N-400 is connected properly to mains (AC) supply.

• Check mains (AC) fuses.

2. Patient module cannot be connected.

• Use only a NELLCOR PURITAN BENNETT N-400 Fetal Patient Module.

• Connector pins may be bent; replace with another N-400 Fetal Patient Module.

2-4

Section 2: Troubleshooting

3. Sensor Unplugged indicator is On.

• Check connection between the sensor and patient module.

• Check connection of patient module cable to N-400.

• If connections are okay, use a new sensor.

• If problem persists, use a new patient module.

4. Sensor Lifted indicator is On.

• Sensor is not making adequate contact at the sensor site on the fetus.

» Assess sensor placement relative to fetal head position.

» Assess sensor depth relative to the fetal presenting part;

advance or withdraw the sensor as indicated in Sensor Placement Guide.

» If the indicator does not respond to advancing or withdrawing

the sensor, remove the sensor and place a new sensor, as directed in the Sensor Placement Guide.

5. Searching indicator is on; Pulse Amplitude appears to indicate pulses, but there is no FSpO2 or pulse rate displayed.

• Check the fetus.

• The signal quality is below the acceptable threshold requirement necessary to post data on the display.

» Excessive maternal or fetal motion may be interfering

with signal quality. If possible, keep the patient still.

» The sensor may be improperly positioned. Assess sensor

location and determine appropriate adjustment.

» The fetus’s perfusion may be too low for the N-400 to detect

an acceptable pulse.

• If searching indicator continues to display after evaluations and adjustments:

» The sensor may be damaged; replace it.

» The patient module may be damaged; try another Fetal

Patient Module.

2-5

Section 2: Troubleshooting

6. FSpO2 or pulse rate change rapidly; Pulse Amplitude indicator is

7. Displayed pulse rate does not agree with that of an electronic

erratic.

• Check the fetus.

• Excessive maternal or fetal patient motion may be making it impossible for the N-400 to find a pulse pattern. If possible, keep the patient still.

• Check whether the sensor is positioned properly, and reposition it if necessary.

• Set the N-400 response time for Mode 1.

WARNING: Do not use an Electrosurgical Unit (ESU) with the N-400 in use. An improperly grounded ESU could cause surface skin burns on the fetus.

• A nearby electrosurgical unit (ESU) may be interfering with performance.

fetal heart rate monitor.

• Excessive maternal or fetal motion may be making it impossible for the N-400 to find a pulse pattern. If possible, minimize patient movement.

• Ensure that the sensor is properly positioned on the fetus.

• Oxygen saturation greater than 80% and/or pulse rate less than 100 could indicate that the values are maternal in origin. Check sensor placement to ensure that it is properly positioned on the fetus.

8. Displayed fetal FSpO2 does not correlate with the SaO2 value calculated from a fetal scalp blood sample measurement on a blood gas analyzer.

• Close correlation requires simultaneous blood sampling and pulse oximeter measurements from the same arterial supply. Blood samples exposed to air during the sampling process or taken from the scalp may not accurately reflect true arterial values.

• The SaO2 calculation may not have been correctly adjusted for the effects of pH, temperature, PaCO2, 2,3-DPG, or the presence of fetal hemoglobin. Check whether calculations have been corrected appropriately for relevant variables. (See the Principles of Operation section of the N-400 operator’s manual for more information.) In general, calculated SaO2 values are not as reliable as direct CoOximeter or pulse oximeter measurements.

• N-400 FSpO2 accuracy can be affected by incorrect sensor application or use, significant levels of dysfunctional hemoglobins, excessive patient movement, venous pulsation, or nearby electrosurgical interference. Observe all instructions, warnings, and cautions in the N-400 operator’s manual and in the Sensor Placement Guide.

2-6

Section 2: Troubleshooting

9. Displayed fetal FSpO2 does not correlate with the SaO2 value calculated from a fetal scalp blood sample measurement on a CoOximeter.

• Fractional measurements may not have been converted to functional measurements before the comparison was made. The N-400, as well as other two-wavelength oximeters, measures functional saturation. Multi-wavelength oximeters measure fractional saturation. Fractional measurements must be converted to functional measurements for comparison. Refer to the equation for this conversion in the Principles of Operation section of the N-400 operator’s manual.

10. FSpO2 saturation greater than 80%.

• Check sensor placement to ensure that it is properly positioned on the fetus.

• Ensure that the displayed FSpO2 is fetal and not maternal in origin.

2-7

SECTION 3: PACKING FOR SHIPMENT

3.1 General Instructions

3.2 Repacking in Original Carton

3.3 Repacking in a Different Carton

Should you need to ship the N-400 monitor for any reason, follow the instructions in this section.

3.1 GENERAL INSTRUCTIONS

Prior to shipping the device, contact Nellcor Puritan Bennett Technical Services for a returned goods authorization (RGA) number. Mark the shipping carton and any shipping forms with the RGA number.

Pack the monitor carefully. Failure to follow the instructions in this section may result in loss or damage not covered by the Nellcor Puritan Bennett warranty. If the original shipping carton is not available, use another suitable carton or call Nellcor Puritan Bennett Technical Services to obtain a shipping carton.

3.2 REPACKING IN ORIGINAL CARTON

If available, use the original carton and packing materials. Pack the monitor as follows:

1. Place the monitor and, if necessary, accessory items in original packaging.

2. Place in shipping carton and seal carton with packaging tape.

3. Label carton with shipping address, return address, and RGA number.

3.3 REPACKING IN A DIFFERENT CARTON

If the original carton is not available:

1. Place the monitor in plastic bag.

2. Locate a corrugated cardboard shipping carton with at least 200 pounds per square inch (psi) bursting strength.

3. Fill the bottom of the carton with at least two inches of packing material.

4. Place the bagged unit on the layer of packing material and fill the box completely with packing material.

5. Seal the carton with packing tape.

6. Label carton with shipping address, return address, and RGA number.

3-1

SECTION 4: SPECIFICATIONS

4.1 Performance

4.2 Controls

4.3 Alarms

4.4 Audio Pulse

4.5 Response Modes

4.6 ECG

4.7 Switches

4.8 Data I/O

4.9 Connectors

4.10 Electrical

4.11 Physical

4.12 Environmental

4.1 PERFORMANCE

4.1.1 Display Ranges:

Pulse Rate: 0 to 250 beats/minute

FSpO2: 0% to 100%

4.1.2 Accuracy:

Pulse Rate: 30 to 240 beats/minute, ±3 bpm

4.1.3 Sensor:

FSpO2 Calibration and Reproducibility:

Calibration of the NELLCOR PURITAN BENNETT N-400 Fetal Oxygen Saturation Monitor was accomplished through controlled hypoxia studies in a piglet model. The calibration was validated in an independent animal study of a different group of piglets and in a multi-center human study comparing N-400 readings to simultaneous laboratory arterial blood saturation values obtained on severely cyanotic human infants and children.

Reproducibility of system was evaluated under conditions of actual use in a series of dual sensor studies, in which two sensors were placed simultaneously on a human fetus during active labor.

The resulting reproducibility was 1 SD = 6.0%. Nominally, 68% of the measurements across the population will be within ±1 SD (standard deviation).

Type:NELLCOR PURITAN BENNETT Fetal Oxygen Sensor (reflectance sensor)

Heating: Sensor power dissipation is less than 80 mW total heat dissipation by LEDs (less than 3.0˚C temperature rise).

4-1

Section 4: Specifications

4.2 CONTROLS

Front Panel: ON/STANDBY switch, control knob, Audio Alarm Off button, Low Saturation Limit button, ECG Display button, Response Time button

Rear Panel: Mains (AC) ON/OFF switch, Decrease (zero) button, Increase (full-scale) button, DIP switches (used to set analog output scale, RS-232 format, and baud rate)

4.3 ALARMS

The audible alarm default state is OFF. Audible and visible alarms for low oxygen saturation; audible alarm and visual indicators for loss of pulse. Audible alarms are interrupted briefly for detected pulses; the volume is adjustable. See Alarms in the N-400 operator’s manual.

4.4 AUDIO PULSE

Default volume is OFF. If enabled, and a signal from the sensor is present, an audible beep sounds with each detected pulse; volume is adjustable with control knob; pitch varies to reflect changes in oxygen saturation.

4.5 RESPONSE MODES

4.6 ECG

4.7 SWITCHES

Two response modes, selected by the Response Time button: Mode 1 (default), slow, 50 seconds (at 150 bpm); Mode 2, fast, 11 seconds (at 150 bpm). See Response Time in the Guide to Operation section of the N-400 operator’s manual.

Via rear-panel ECG input jack

• Input: High-level ECG output signal from EFM through an ECG interface cable. For optimum performance, a signal with positive deflection is recommended.

• Input Range: 0.05 V minimum input signal; should not exceed ±15 V. Minimum of 10 ms wide at 50% of peak amplitude.

Ten for digital output format and analog output voltage range.

Switch Section Function

1 analog output voltage range 2,5,9,10 not used 3,4 baud rate select 6,7,8 RS-232 format

4-2

4.8 DATA I/O

Digital

Analog

FSpO2 Accuracy: ±20 mV at zero (0), ±0.5% of full scale,

4.9 CONNECTORS

Section 4: Specifications

Type: RS-232 format Connector: 9-pin D-type, female Baud Rate: Switch-selectable, 1200, 2400, 9600, and 19,200

Formats: Conversation, beat-to-beat

3 each; 3/32-inch subminiature phone jacks

Outputs: FSpO2 and Plethysmographic Waveform

Voltage: 0-1 or 0-10 V (switch-selectable, DIP switch 1)

Maximum voltage output: 10 V

referred to front panel display

Input: High-level ECG output signal from an EFM

Front Panel: N-400 Fetal Patient Module Connector

4.10 ELECTRICAL

Voltage Requirement: 100 – 120 V~ ±10% at 50/60 Hz

Current Requirement: 300 mA, maximum

Power Consumption: Maximum rating: 30 VA

Rear Panel: FSpO2 analog output jack (3/32”)

Plethysmographic Waveform analog output jack (3/32”) Fetal High-level ECG input jack (3/32”) Serial Communications connector (9-pin, D-type connector) Mains (AC) power input

200 – 240 V~ ±10% at 50 Hz

Fuses: 115 V~: 2 x T 500 mA, 250 V

230 V~: 2 x T 250 mA, 250 V

Classification: Protective Class: IEC Class I

Degree of Protection: Type BF Enclosure Degree of Protection: Ordinary (IPXO) Mode of Operation: Continuous

4-3

Section 4: Specifications

4.11 PHYSICAL

Monitor

Patient Module

panel; Fetal Sensor connector, mates with 9-pin connector

4.12 ENVIRONMENTAL

Transport (in shipping container)

Dimensions: 12.6” wide x 12” deep x 3” high

(32 cm x 30 cm x 8 cm)

Weight: 9 lb

(4.1 kg)

Cable length: 13 ft (4 m) cable

Connectors: Lemo B-series, mates with 12-pin connector on N-400 front

on Fetal Oxygen Sensor

Temperature: –40°C to +70°C (–40°F to +158°F)

Storage (not in shipping container)

Operating

Emissions Compliance

Altitude/Barometric Pressure:

–390 m to +6,096 m (–1280 ft to +20,000 ft) +1060 hPa to +500 hPa (+31.1 in. Hg to +14 in. Hg)

Relative Humidity: 15% to 95% (noncondensing)

Temperature: –40°C to +60°C (–40°F to +140°F)

Altitude/Barometric Pressure:

–390 m to +6,096 m (–1280 ft to +20,000 ft) +1060 hPa to +500 hPa (+31.1 in. Hg to +14 in. Hg)

Relative Humidity: 15% to 95% (noncondensing)

Temperature: +5°C to +40°C (+41°F to +104°F) Altitude/Barometric Pressure:

–390 m to +6,096 m (–1280 ft to +20,000 ft) +1060 hPa to +500 hPa (+31.1 in. Hg to +14 in. Hg)

Relative Humidity: 15% to 95% (noncondensing)

4-4

EN55011 Emissions Classification CISPR II, Group I, Class B

SECTION 5: TECHNICAL SUPPORT

5.1 Theory of Operation

5.2 Block Diagram Analysis

5.3 Circuit Descriptions

5.4 Schematic, Part Locator, and Block Diagrams

5.1 THEORY OF OPERATION

Operation of the N-400 Fetal Oxygen Saturation system is based on the principles of pulse oximetry, which in turn is based on spectrophotometry and plethysmography. The system includes an electro-optical sensor and a microprocessor-based monitor.

Oxyhemoglobin and deoxyhemoglobin have different light absorption characteristics in the far red and infrared wavelength spectrums. Less red light is absorbed by oxyhemoglobin than by deoxyhemoglobin. Relatively more infrared light is absorbed by oxyhemoglobin than by deoxyhemoglobin. Arterial blood in a well-oxygenated fetus will typically contain a higher concentration of oxyhemoglobin than deoxyhemoglobin.

The N-400 uses these differences in the absorption of far red and infrared light by oxy- and deoxyhemoglobin to determine fetal oxygen saturation by measuring the change in light levels caused by pulsating arterial blood in the tissue.

The fetal oxygen sensor has two low-voltage light-emitting diodes (LEDs). One of these LEDs emits red light (nominal 735 nm wavelength) and the other emits infrared light (nominal 890 nm wavelength). When the sensor has been properly positioned on the fetal temple or cheek, light from each of these LEDs is alternately sent through the fetal skin into the underlying tissues at the sensor site. The amount of light absorbed by the tissue or blood underlying the fetal sensor is determined from the amount of light that scatters back to the tissue surface and is picked up by the photo detector (photo diode) on the sensor.

Light absorption is first measured by the N-400 at each wavelength when no pulsatile blood is present. This reflects the background light absorption of bone, tissue, and venous blood, which are generally considered non-pulsating. This measurement is analogous to the reference measurement of a spectrophotometer.

With each fetal heart beat, a pulse of arterial blood flows to the oxygen sensor site. Red and infrared light absorption are then measured by the N-400 at each wavelength when this pulsatile, arterial blood is in the tissue. The N-400 microprocessor compares the background light absorption measurements to the absorption measured at both light wavelengths during each arterial pulse. The ratio of the corrected absorption at each wavelength is used to determine fetal oxygen saturation (FSpO2).

5-1

Section 5: Technical Support

5.1.1 Auto Calibration

The N-400 oximetry subsystem is automatically calibrated each time the monitor is turned on, at periodic intervals thereafter, and whenever a new sensor is connected. The intensities of the sensor LEDs are adjusted automatically to compensate for differences in tissue light absorption characteristics, or other sources of light attenuation.

Each fetal oxygen sensor is calibrated when manufactured: the effective mean wavelength of the LEDs is determined and encoded into a calibration resistor in the sensor. The N-400 software reads this calibration resistor when the sensor is connected to determine the appropriate calibration coefficients for the measurements obtained by that specific sensor.

5.1.2 Functional vs Fractional Saturation

Because the N-400 measures functional SaO2, it may produce measurements that differ from those of instruments that measure fractional SaO2. Functional SaO2 is oxygenated hemoglobin expressed as a percentage of the hemoglobin that is capable of transporting oxygen. Because the N-400 uses two wavelengths, it measures oxygenated and deoxygenated hemoglobin, yielding functional SaO2. It does not detect dysfunctional hemoglobins, such as carboxyhemoglobin or methemoglobin.

In contrast, some laboratory instruments such as the Instrumentation Laboratory 282 or 482 CO-Oximeter report fractional SaO2 - oxygenated hemoglobin expressed as a percentage of all measured hemoglobin, whether or not that hemoglobin is available for oxygen transport. Measured dysfunctional hemoglobins are included.

Consequently, to compare N-400 measurements directly with those of another instrument, that other instrument must measure functional SaO2. If the other instrument measures fractional SaO2, those measurements can be converted to functional SaO2 using the following equation.

functional saturation =

100 - (% carboxyhemoglobin + % methemoglobin)

fractional saturation

x100

5-2

+ 56 hidden pages

Nellcor N-400 User manual

Specifications and Main Features

Frequently Asked Questions

User Manual

1.1 Manual Overview

1.2.1 Warning

1.2.2 Caution

1.2.3 Note

1.3 DEVICE DESCRIPTION

1.4 ROUTINE MAINTENANCE

1.5 CLEANING

1.6 SPARE PARTS

2.1 Introduction

2.2 Error Codes

2.3 TROUBLESHOOTING GUIDE

3.1 General Instructions

3.2 Repacking in Original Carton

3.3 Repacking in a Different Carton

4.1 Performance

4.2 CONTROLS

4.3 ALARMS

4.4 AUDIO PULSE

4.5 RESPONSE MODES

4.6 ECG

4.7 SWITCHES

4.8 DATA I/O

4.9 CONNECTORS

4.10 ELECTRICAL

4.11 PHYSICAL

4.12 ENVIRONMENTAL

5.1 Theory of Operation

5.1.1 Auto Calibration

5.1.2 Functional vs Fractional Saturation