Nellcor ULTRA CAP N-6000 User manual

SERVICE MANUAL
NELLCOR® ULTRA CAP™
PULSE OXIMETER AND CAPNOGRAPH,
MODEL N-6000
Caution: Federal law (U.S.) restricts this device
to sale by or on the order of a physician.
Nellcor Incorporated
25495 Whitesell Street
Hayward, California 94545 U.S.A.
510 887-5858
1-800-NELLCOR
© 1993 Nellcor Incorporated . 028065A-0193

Corporate Headquarters
Nellcor Incorporated
25495 Whitesell Street
Hayward, California 94545
USA
Tel [phone]
ii
European Office Asia/Pacific Headquarters
Nelleor BV
Hambakenwetering 1
5231 DD ’s-Hertogenbosch
The Netherlands
Tel. [phone]
Nellcor Limited
Suite 1204C
Admiralty Centre, Tower 1
18 Harcourt Road
Hong Kong
Tel. [phone]
European Regional Offices
Northwest Europe
Nellcor Europe BV
Hambakenwetering 1
5231 DD ‘s-Hertogenbosch
The Netherlands
Tel. [phone]
Middle and Central Europe
Nelleor GmbH .
Black-&-Decker-Strasse 28
W-6270 Idstein
Germany
| Tel. [phone]
Southern Europe
Nellcor Sarl
3, rue du Petit Robinson
78353 Jouy-en-Josas Cedex
France
Tel. [phone]
European Local Offices
Nellcor (UK) Limited
University of Warwick
Science Park
Coventry CV4 7EZ
United Kingdom
Tel. [phone]
Nelleor (Belgium) NV/SA
Interleuvenlann 62/8 .
B-3001 Leuven
Belgium
Tel. [phone]

11
12
13
2.1
2.2
2.3
2.4
2.5
3.1
3.2
3.3
3.4
TABLE OF CONTENTS
Symbols AAA
We
Introduction... 나
Introduction......................... … 1-1
Warnings, Cautions, and Notes ... … 1-1
Description..................,..,............,... .. 1-2
1.8.1 Visible and Audible Indicators. „12
13.2 Audible Indicator....................... .. 1-2
13.3 Visible and Audible Alarms. 12
13.4 StatusMessages.............................. . 1-2
1.3.5 Automatic Self-Test and Warm-Up Time.. .. 1-3
1.3.6 On-Screen Menus..................,...,,,....... … 13
1.3.7 N-6000 Default and Custom Default Set-Up . .... 13
18.8 Trend Memory......:...,...............,,,,,...... レレ くく レト ニュ レッ くく トー トト ャ ッッ て と と ャ て て と て て とく ここ 13
1.3.9 Automatic Calibration..…..............,........,.,.......ss ss 13
1.3.10 Battery Operation .................. 13
1.3.11 Noninvasive Oximetry Sensors......................... 1-4
13.12 C-LOCK™ ECG Synchronization for Pulse Oximetry..
Principles of Operation. . 2-1
Overview......................... .. 21
PulseOximetrySubsystem....................... ‚... 2-1
2.2.1 C-LOCK ECG Synchronization „21
2.2.2 Automatic Calibration.................. „22
2.2.8 Functional versus Fractional Saturation...
2.2.4 - Measured versus Calculated Saturation .... ーー
Capnography Subsystem ............................ . 2-3
N20/02 Compensation ............ .. 2-5
24.1 Standard Gas Conditions ... .. 25
2.4.2 Pressure Broadening Compensation... 2-5
2.4.3. N20 Collision Broadening........... . 2-6
2.4.4 O2 Collision Broadening.........................,.,...........ss 2-6
2.4.5 Water Vapor Effect... issues 2-6
2.4.6 BTPS/ATPS Compensation. 2-6
2.4.7 Summary: Reported CO2 Values... .. 2-6
. Factory Calibrated Sensor μμ ΕΟΟ ρου .. 2-7
Circuit Analysis
Introduction................. . 3-1
CO2 Module Circuit Details. .. 3-2
3.2.1 Sensor Operation......... .. 3-2
3.2.2 CO2 Module Hardware .... ... .. 3-2
3.2.3 bDigital..................... ... .. 3-2
8.2.4 Motor Control........ 3-3
3.2.5 Signal Amplifier.. … 3-8
3.2.6 Heater 22220 … .. 3-8
3.2.7 Source.... 3-3
8.2.8 Barometer... ..
3.2.9 StatusLEDs.................... … 3-3
3.2.10 Status LED Summary............ ... BA
Oximetry Module Block Diagram Analysis … 3-4
© 8.8.1 OximetryModule........................ ... 3-4
Detailed Oximetry Module Circuit Analysis 3-6
3.4.1 Oximetry Module sense ας 3-6

3.5
3.6
4.1
4.2
4.3
4.4
5.1
5.2
5.3
6.1
6.2
7.1
7.2
7.3
8.1
8.2
8.3
9.1
iv
TABLE OF CONTENTS (continued)
Main Processor PCB Circuit Details. essences
8.5.1 Microprocessor Section.......,...............,....,......,
8.5.2 Power. Control.........
3.5.3 Reset and Watehdog......................
3.5.4 Battery Backup and Memory Retention............
8.5.5 Internal and External Serial Communications..
8.5.6 Graphical Display ..................,....,,.....,..,.
3.5.7 BEPROM..............
8.5.8 FLASH Memory.
8.5.9 Real Time Clock....
3.5.10 Audio Generation ....
3.5.11 Charging Indicator................
3.5.12 Patient Isolation Power Supply...
3.5.13 Front Panel Display Controller..
Power Supply-Charger PCB Circuit Details.........
3.6.1 Power Supply Charger Theory of Operation..
3.6.2 AC Rectifier and +12 volt Battery Charger...........
3.6.3 +5 Volt Logic and Display Power Supply ....
3.6.4 C-LOCK QRS Sync Input Circuit... …
Routine Maintenance ......................
Introduction............
Cleaning Instructions............
Changing Mains Voltage Input ....
Replacing or Changing the Fuse...
Packing and Shipping......
Överview...........................
Repacking In Original Carton..
Repacking In New Carton .......
Testing and Calibration ............
Description.....................
COs Display ConventionS 0
Disassembly Guide........
Introduction............ ..
”Disassempbly Procedure ees enten ennen nernnse
6.2.1 RemovinginstrumentCover........................... eker
6.2.2 Removing 了 attery. < scccrcre*
6.2.3 Removing Oximetry and C02 Subassembly.. „
6.2.4 Removing Main Processor PCB........................... 0040000400000 000000e0 en
6.2.5 Removing Front Panel Assembly .............................,................,.....
6.2.6 Removing Pull-Out Card Tray...
6.2.7 Removing Speaker............................
6.2.8 Removing Power Supply-Charger Assembly.
6.2.9 Removing Transformer..........
7.2.1 Service Screen and Display Conventions...................
7.2.2 Breath Detection and Display of End-Tidal CO2 Values.. … 72
Calibration and Accuracy Check ui iii .. 7-6
Troubleshooting........................ . 8-1
Introduction....... . 8-1
Advisory Messages. ーー .. 8-6
Status Messages..... ... .. 8-7
Spare Parts........ … .. 9-1
In го ас 6101... sise 9-1

TABLE OF CONTENTS (continued)
10 ¡ACA essences
10.1 Overview.........
1 Specifications.............
11.1 Physical/Environmental.........
11.2 Components and User Interface..
113 Controls and Indicators...........
114 Connectors................
185 Performance.
11.6. Calibration.....
11.7. Airway Adapter EP O KO KO R O R K KK O RR ek 6
11.8 再 jectrical. 0 0000 Koh OK S KO RS O O KOK KK P KKK oP P een εως
2 Schematic Diagrams.. .
12.1 Introduction...................,......,................. see K R PK O v Kone
LIST OF FIGURES
2-1 Oxyhemoglobin Dissociation Curve.......................................... 0.0000 öseeeeeea
2-2 Nondispersive Infrared CO2 Analyzer..
3-1 Overall Block Diagram..........................
3-2 Oximetry Module Overall Block Diagram...
3-3 LRD Driver Cireuit に し に に に に レート ーーー・
3-4 Input Signal Processing.
3-5 Input Amplifier, Synchronous Detector, and Filter/Amplifier
8-6 A:D Conversion Circuits.......................,.......,,,...........
8-7 Support Circuits................... ..
4-1 North American Fuse Аттапветейв............. линии нии ини тни низине нение
4-2 European Fuse Атгапретейф............... ss наити
6-1 Disassembly Diagram..............
7-1 Failed LED Digits
7-1 Service Screen IndicatiomS レレ ーー トレ ーー トト ーー スー スト ドー くに トー トト トト トス スレ (レレ に レレ に トス レト ストー て
8-1 Troubleshooting Guide
The following are trademarks of Nellcor Incorporated: NELLCOR, which is registered in the
United States and other countries; C-LOCK, which is registered in the United States;
OXISENSOR;; and ULTRA CAP, which is a commercial trademark.
The N-6000 is covered by the following patents: U.S. Patent No. 4,621,643; 4,653,498; 4,700,708;
4,770,179; 4,802,486; 4,869,254; 4,928,692; 4,934,372; and corresponding patents in other countries,

O/O
Sc
nx
el
κ
SYMBOLS
FRONT PANEL
On/Standby eke
Pulse tone volume MENU
Audible alarm off A
+ ni
C-LOCK signal lost
Low battery
Battery charging
220/240V~ INSTRUMENT ONLY
FRONT PANEL
A
vi
Attention: Refer to operator’s
manual!
Freeze
Menu
Audible alarm on
C-LOCK in use
Battery in use
Type BF equipment,
(patient electrically isolated)

SYMBOLS
BACK PANEL
= Battery fuse Fuse replacement
AS ECG input O Eguipotential ground
MO
On/Off
<>
RS232
RS232inputoutput
port
Type
BF
equipment,
À
(patient
electrically
isolated)
110/120 VOLT INSTRUMENTS ONLY
BACK PANEL
Attention: Refer to operator’s
Instrument not anesthetic VAN manual!
proof.
vii

WARNINGS
The N-6000 contains no user-serviceable parts. For protection against electrical hazard, all
service must be performed by qualified personnel.
. [For protection against fire hazard, replace fuses only with the same type and rating.
The N-6000 is a patient-connected medical device. Isolated patient connectors protect the patient
from potentially dangerous electrical potentials or ground paths. To protect the integrity of this
connection, the procedures and part specifications contained in this manual must be adhered to.
viii

SECTION I
Introduction
1.1 INTRODUCTION
This manual contains information for servicing the NELLCOR® ULTRA CAP™ pulse oximeter
and capnograph, model N-6000. Service of this product must be done by qualified service
personnel, who have a technical background in analog and digital electronics.
Note: This manual is written for an N-6000 configured for English-language displays and
service screens. If the unit is configured for French or German, the technician must change the
language option to English. To reach the language selection menu from the main monitoring
screen, press the Freeze button on the front panel while the main monitoring screen is displayed,
and then press the second and fourth soft keys from the left at the same time. The legend
“LANGUAGE” (LANGUE in French and SPRACHE in German) appears above the fourth soft key
from the left. Press this key to gain access to the language selection menu and select “ANGLAIS”
or “ENGLISCH.”
ㆍ The N-6000 is a compact, microprocessor-controlled instrument used for continuous real-
time monitoring of oxygen saturation (SpO2), pulse rate (PR), inspired CO2 (ins.), end-tidal
carbon dioxide (ETCO2), and respiratory rate (RR).
. SpO2 is noninvasively and continuously measured using Nellcor's reusable or adhesive
SpO2 sensors which are available for a variety of patient sites. SpO2 values are displayed
numerically, while the plethysmograph is displayed as a waveform, A bar graph indicator
shows the patient’s relative pulse strength as measured by the pulse oximetry circuits.
ㆍ ETCOs is determined by positioning an infrared mainstream CO2 sensor across an
intubated patient’s airway (15 mm diameter). The amount of CO2 present at the end of
exhalation is displayed numerically, while CO2 is displayed as a waveform.
This manual is intended for use by authorized service personnel, trained in servicing analog and
digital patient monitoring equipment. Service personnel must have read ahd understood the
N-6000 operator’s manual and be familiar with instrument operation before attempting
maintenance or repair.
12 WARNINGS, CAUTIONS, AND NOTES
Before you read the N-6000 service manual, it is important to understand the following terms.
These terms identify information that pertains to technician and patient safety, and indicates
proper operation of this instrument.
WARNING: A warning describes a condition that may result in injury to the patient, operator or
service technician. WARNINGS are always in boldface type and boxed.
Caution: Cautions describes a condition that may result in damage to the instrument. Cautions are
always in boldface type.
Note: A note gives information that warrants special attention.
1-1

1.3 DESCRIPTION
The following paragraphs describe the N-6000 and list important features.
1.3.1 Visible and Audible Indicators
The N-6000 features numeric displays of SpO2, PR, RR, and ETCO2:
. C02 and plethysmographic waveform displays: and a pulse amplitude bar graph, which
* provides a qualitative indication of pulse strength at the oximetry sensor.
9 Trends are acquired for all parameters, and the following five trend screens can be
displayed: SpO2 trend alone; CO2 trend alone; SpO2 and CO2 trends; pulse rate and
respiratory rate trends; SpOz, CO2, pulse rate, and respiratory rate trends.
ㆍ When the operator connects the monitor to AC power and turns on the rear-panel on/off
switch, a battery charging indicator lights.
1.3.2 Audible Indicator
Pulse rate and oxygen saturation are indicated audibly with a tone that signals each pulse. The
pitch of this tone changes with variation in SpO2, rising as saturation increases and falling as it
decreases. This. early warning system encourages prompt corrective action since the clinician
can watch the patient and listen for SpO2 changes simultaneously.
1.3.3 Visible and Audible Alarms
The monitor has both visible and audible alarms. These alarms are activated when a variable
moves outside an adjustable limit (operator-defined), when the monitor detects loss of pulse or
apnea, or when a sensor gets disconnected. The tone and pattern of the audible alarm depend on the
priority of the alarm state. Pressing the ALARM SILENCE button turns off the audible portion of
the alarm temporarily. A flashing ALARM SILENCE indicator adjacent to the ALARM SILENCE
button alerts the operator that the alarm tone has been silenced temporarily. A steady ON of the
ALARM SILENCE indicator warns that one or more parameters have had their audible alarm
function disabled. Visible alarms appear on the monitor sereen, and unlike audible alarms, they
are always operational.
Note: The SpO2 and ETCO2 numeric indicators change from green to red when an alarm occurs.
Note: When the French language is chosen and one or more of the parameters have had the error
audible alarm function disabled, a single tone occurs every three minutes.
1.3.4 Status Messages
A status message is displayed in case an error condition occurs. An error condition will be
identified by a module identifier and an error code number that assists service personnel in
troubleshooting the problem. (See section VIII for more information.)

1.3.5 Automatic Self-Test and Warm-Up Time
The monitor automatically performs a series of diagnostic tests when turned on. The system self-
test takes approximately 15 seconds after the operator turns on the monitor. These tests confirm
that the program memory, data memory, and internal circuitry are functioning properly, while
allowing the mainstream COz sensor to warm. The CO2 sensor warm-up time is approximately
45 seconds. If an error is detected, a status message appears. (Refer to Section 8,
“Troubleshooting,” for more information.) —
1.8.6 On-Screen Menus
The on-screen menu guides the operator through all system functions. Menu items are displayed
at the bottom of the screen just above the four function keys that are used to select an item. When a
function key is pressed, the screen displays a new menu with additional functions. Press the
MENU button to display the top level menu, or to return to the main monitoring screen.
1.8.7 N-6000 Default and Custom Default Set-Up
The N-6000 power-on default settings can be customized according to institutional requirements,
Once configured, the custom alarm limits will always be in place, even after power-down.
1.3.8 Trend Memory
The N-6000 stores up to 24 hours of trend data for CO2, SpO2, pulse rate, and respiratory rate. Trend
memory can be viewed in 30-minute, 2-hour, 4-hour, 8-hour, 12-hour, or 24-hour segments. When
the memory is full, the oldest data are automatically erased as new data are stored. Data stored in
memory can be viewed on the sereen and can be printed with a printer. Patient monitoring
continues while the trend data are being printed.
1.3.9 Automatic Calibration
The SpO2 subsystem of the N-6000 is fully self-calibrating. It is calibrated automatically whenever
the system is turned on and periodically thereafter. Additionally, it is recalibrated automatically
whenever a new oximetry sensor is connected. The capnography subsystem of the N-6000 is factory
calibrated.
1.3.10 Battery Operation
If external power is lost or transportable operation is necessary, the N-6000 can operate up to
90 minutes on its rechargeable internal battery. This operating time can be extended up to 180
minutes by using the GRAPHICS w/BATTERY power saver option.
ㆍ By choosing GRAPHICS w/BATTERY ON in the SYSTEM menu, the display graphics
(including all waveforms, messages, etc.) will continue to operate. By choosing GRAPHICS
w/BATTERY OFF, the display remains blank during battery operation. The N-6000
displays only the numerical values of SpO2 and ETCO2, This allows up to 180 minutes of
battery life.
. When the GRAPHICS w/BATTERY option is selected to be OFF and the unit is operating on
AC MAINS power, the display will only blank when the unit transfers to battery power. Press
the MENU button to turn the GRAPHIC w/BATTERY option ON. The display returns when
the operator reapplies AC power to the monitor.

1.3.11 Noninvasive Oximetry Sensors
Noninvasive NELLCOR oximetry sensors obtain measurements by optical means alone, using
two light-emitting diodes (LEDs) as light sources. The N-6000 adjusts automatically for
differences in tissue thickness or skin pigmentation. Specific sensors are available for neonates,
infants, children, and adults. Refer to specific sensor directions for use for complete information.
1.3.12 C-LOCK™ ECG Synchronization for Pulse Oximetry
If a patient is moving or has poor perfusion, C-LOCK ECG synchronization can enhance signal
quality for measurements of oxygen saturation. When this feature is used, the N-6000 receives two
separate signals that reflect cardiac activity: an optical signal from the sensor and an electrical
signal from the ECG. The N-6000 uses the ECG QRS complex to help identify the pulse and
synchronize the SpOz measurements.
When C-LOCK ECG synchronization is used, the C-LOCK IN USE symbol appears on the display.
If the ECG signal is lost or deteriorates to the point that it can no longer be used, the C-LOCK
SIGNAL LOST symbol appears on the display. No symbol is displayed if the C-LOCK feature of the
N-6000 is not being used. :

SECTION II
Principles of Operation
2.1 OVERVIEW
This section describes, in general terms, operating principles for the N-6000.
2.2 PULSE OXIMETRY SUBSYSTEM
The N-6000 oximetry subsystem is based on the principles of spectrophotometry and
plethysmography. It includes an ‘electro-optical sensor and a microprocessor-based module. The
sensor has two low-voltage light-emitting diodes (LEDs) as light sources, and one photodiode as a
photodetector. One LED emits red light (nominal 660 nm) and the other emits infrared (nominal
920 nm). When the light from the LEDs passes through the sensor site, part of the light is absorbed.
The photodetector measures the light that passes through, which indicates red and infrared
absorption.
With each heartbeat, a pulse of oxygenated arterial.blood flows to the sensor site. Oxygenated
hemoglobin
differs from deoxygenated hemoglobin in its relative red and infrared absorption.
The N-6000 measures red and infrared absorption to determine the percentage of functional
hemoglobin that is saturated with oxygen.
In principle, a pulse oximeter measures the light absorption by tissues and nonpulsatile blood.
Absorption is also measured when pulsatile arterial blood is in the tissue. The ratio of absorption at
both wavelengths results in a value for the arterial oxygen saturation (SpO2).
2.2.1 C-LOCK ECG Synchronization
Through C-LOCK ECG synchronization, the N-6000 uses an ECG signal as a reference point for
identifying the pulse and synchronizing SpO2 measurements. This enhances signal quality
during patient movement and when the patient’s perfusion is poor.
When provided with an ECG signal, the N-6000 receives two signals that reflect cardiac activity:
an optical signal from the sensor and an electrical signal from the ECG. A short time after a QRS
complex is detected, an optical pulse is detected at the sensor site. The length of this delay varies
with the patient’s physiology and with the location of the sensor. However, for a given patient, the
length of the delay is relatively stable. Through C-LOCK ECG synchronization, that time -
relationship is used to identify “good” pulses and reject nonsynchronized artifacts such as
random motion.
If an ECG signal is not provided, or if that signal deteriorates so that it can no longer be used, the
optical pulse alone is used to determine the pulse rate and to initiate saturation measurements.
C-LOCK ECG synchronization resumes when an adequate ECG signal is available.
2-1

2.2.2 Automatic Calibration
The oximetry subsystem incorporates automatic calibration mechanisms. It is automatically
calibrated each time it is turned on, at periodic intervals thereafter, and whenever a new sensor is
connected. Also, the intensity of the sensors LEDs is adjusted automatically to compensate for
differences in tissue thickness and pigmentation.
Each sensor is calibrated when manufactured: the effective mean wavelength of the red LED is
determined and encoded into a calibration resistor. The instrument’s software reads this
calibration resistor to determine the appropriate calibration coefficients for the measurements
obtained by that sensor.
2.2.3 Functional versus Fractional Saturation
Because the N-6000 measures functional SaO2, it may produce measurements that differ from
those of instruments that measure fractional SaO2. Functional SaQ2 is oxygenated hemoglobin
expressed as a percentage of the hemoglobin that is capable of transporting oxygen. Because the
N-6000 uses two wavelengths, it measures oxygenated and deoxygenated. hemoglobin, yielding
functional SaO2. It does not detect significant amounts of dysfunctional hemoglobin, such as
carboxyhemoglobin or methemoglobin.
In contrast, some laboratory instruments such as the Instrumentation Laboratory 282 CO-
Oximeter report fractional SaQ2-—~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 directly compare N-6000 measurements with those of another instrument, that
other instrument must measure functional SaO2. If it measures fractional Sa02, those
measurements can be converted using the following equation:
fractional saturation
functional saturation = ~ x
100 — (%carboxyhemoglobin + %methemogiobin
2.2.4 Measured versus Calculated Saturation
When saturation is calculated from a blood gas measurement of the partial pressure of arterial
oxygen (PaO2), the calculated value may differ from the N-6000 SpO2 measurement. This is
because the calculated saturation may not have been corrected for the effects of variables that shift
the relationship between PO2 and saturation (Figure 2-1): temperature, pH, the partial pressure of
carbon dioxide (PaCO2), the concentrations of 2,3-DPG and fetal hemoglobin.
2-2

100 —
t
pH
„==
=.
+
Temperature
.”
est
+
PCO2
>
n°
+ 2,3-DPG
“e
„>“
¿e
>. ㆍ
΄
+
=
+ e
ο
7 è
я
; .
+
pH
5
504
+
e
+
Temperature
©
4
+
+
PCO2
.
の
e
e
+
2,3-DPG
a
ifs
4 +
+
+
+
+
nf.
+
+
7
の
VA
0
|
50
100
PO: (mmHg)
Figure 2-1: Oxyhemoglobin Dissociation Curve
2.3 CAPNOGRAPHY SUBSYSTEM
The N-6000 uses nondispersive infrared spectroscopy to quantitatively measure the amount of CO2
present at the end of exhalation (ETCO2). It features a small lightweight “mainstream” CO2
sensor that attaches to a disposable airway adapter. The airway adapter is inserted into the
ventilator circuit either between the endotracheal tube and the ventilator circuit or between the
elbow and the patient wye. The CO2 mainstream sensor fits on top of the adapter and does not come
into contact with the respired gases.
Infrared spectroscopy can be used to measure the concentration of any molecule that absorbs
infrared light. Of the normally respired gases, only CO2, N20, and water vapor selectively absorb
specific wavelengths of infrared light (i.e., have an infrared spectrum). This absorption pattern,
the infrared spectrum of a molecule (usually displayed as a graph of light absorbed by a molecule
versus the wavelength of light), is unique to. that molecule. However, different molecules may
have similar spectra that have overlapping absorption peaks. Because the absorption of light is
proportional to the concentration of the absorbing molecule, an unknown concentration can be
determined by comparing the absorbance to that of a known standard.
The CO2 detection mechanism used in the N-6000 (commonly referred to as the CO2 sensor or
“optical bench”), has an infrared source that is optically filtered to provide a narrow band of
wavelengths corresponding to an absorption peak of the CO2 spectrum (see Figure 2-2).
During monitoring, light first passes through the respiratory gas in the airway adapter. Next it
reaches the narrow-band infrared filter, which was selected because it passes wavelengths that are
selectively absorbed by 0602. It then encounters the chopper wheel, which rotates many times each
second. Three measurements are obtained during each rotation:
ο A sample measurement is made when the light passes through the open area of the chopper
wheel and then reaches the detector (i.e., light passes through the respiratory gas).

. A reference+sample measurement is obtained when light passes through a reference gas cell
containing a known CO2 concentration and then reaches the detector (i.e., light passes through
respiratory gas and gas in the reference cell).
ㆍ A dark measurement is made when light strikes a solid area of the wheel (1.9., no light
reaches the detector).
The ratio, “reference+sample/sample”, is then used in the sensor-specific calibration equation to
determine the CO2 concentration in respiratory gas. Respiratory rate is determined by the N-6000
from the analysis of the CO2 waveform (capnograph).
The N-6000 measures the partial airway pressure of CO2 in the patient airway adapter at normal
assumed conditions of 33° C and fully saturated. Barometric pressure is measured directly by the
N-6000. When units of % (by volume) are displayed on the front panel LEDs, the measured value is
expressed as % dry gas. By convention, all readings of CO2 posted on the front-panel LED display
are assumed to be measured from a patient and corrected to body temperature (37° C). When PCO2
is being displayed on the front panel LED in units of mmHg or kPa, the values are also converted
to fully saturated conditions (BTPS ) before being displayed.
The N-6000 detects and counts breaths when the COz2 level crosses a threshold, which is set
dynamically from maximum and minimum CO2 values. Hence, when a ventilated patient has
several spontaneous breaths with low ETCO2 values followed by a mechanical breath with a higher
ETCO? value, the N-6000 accurately detects and counts all breaths.
The value of ETCO2 that best estimates the true alveolar CO2 value is the maximum value
obtainable from the patient during forced exhalations. Unlike conventional capnometers that
simply average all breaths together to-display the ETCO2 value, the N-6000 looks for the maximum
value of ETCO2 seen within the last 8 seconds and displays that maximum value for the true
ETCO2. This results in a stable ETCO2 value that best approximates the arterial PaCO value in the
patient.
Reference
gas cell
Open
area
!
Light Airway Infrared Chopper Photodetector
source adapter filter wheel
Figure 2-2: Nondispersive Infrared CO2 Analyzer
2-4

24 N20/O2 COMPENSATION
Unless compensated for, elevated levels of oxygen (O2) and nitrous oxide (N20) in the airway
affect the measurement of the concentration of CO2 by a collision broadening effect.
To ensure accurate measurements, the N-6000 provides two levels of compensation: (1) nitrous
oxide with oxygen; and (2) high oxygen. Compensation levels are user selectable via display
screen menu selections.
The N-6000 is calibrated for low O2 compensation, which assumes the reference state of 0% nitrous
oxide and 20% oxygen. This is the default mode where COMP. = OFF. In the N-6000, an increase
in O2 beyond the reference state decreases the displayed CO2 value by 1.5% of reading for every
20% of increase in O2. An increase in N20 increases the displayed CO2 value by 1.6% of reading
for every 20% increase in N20.
The first compensation level assumes 50% nitrous oxide and 50% oxygen. Selecting COMP. = N20
provides the necessary correction factor for high levels of N20. When this correction is applied,
there is zero error under these assumed conditions,
The second compensation level assumes 0% nitrous oxide and 60% oxygen. Selecting COMP. = O2
provides the correction factor for high levels of O2. Once again, when this correction is applied,
there is zero error under these assumed conditions.
Finally, barometric pressure changes also affect measured CO2 values. However, changes in
barometric pressure require no user intervention; the N-6000 automatically adjusts for these
changes.
The following paragraphs contain further in-depth discussion of compensation and standard
conditions, as pertains to N-6000 operation.
2.4.1 Standard Gas Conditions
The accuracy specifications for the N-6000 refer to the following standard conditions: test gas is
CO2 in balance air (21% O2), at airway conditions of 33 °C, fully saturated (water vapor pressure of
38 mmHg), and a barometric pressure of 760 mmHg. Additional corrections and/or residual
errors are required for barometric pressure (altitude), N20, 02, and water vapor.
2.4.2 Pressure Broadening Compensation
Ambient barometric pressure affects measured CO2 by a “pressure broadening” effect, in which
energy exchanged in molecular collisions alters the absorption spectrum of CO2. In the N-6000,
barometric pressure is automatically measured and a compensation is automatically applied to
CO2 values reported on both the main monitoring screen and the service screen. However,
additional residual errors may be observed when testing reference gases at pressures different
from the standard reference state of 760 mmHg (sea level). These amount to approximately +0.5
mmHg for every 5000-foot change in altitude.
2-5

2.4.3 N20 Collision Broadening
Nitrous Oxide (N2O) can affect the CO2 measurement by both direct absorption of infrared and by a
“collision broadening” effect in which energy exchanged in molecular collisions alters the
absorption spectrum of CO2. The infrared narrow bandpass filter used in the N-6000 is chosen to
eliminate any direct absorption of infrared energy by N20. However, N20 collision broadening
causes an increase in measured CO2 of approximately +0.8% per 10% increase in N20 from
standard conditions. A software-selected (user-selectable) N20 compensation option is provided to
correct for high N20, assuming a gas composition of 50% N20 and 50% O2. CO2 values reported on
both the N-6000 main monitoring screen and on the service screen are compensated for this gas
mixture if the 02 compensation option is selected.
2.4.4 O2 Collision Broadening
Oxygen (02) can affect the CO2 measurement by a “collision broadening” effect in which energy
exchanged in molecular collisions alters the absorption spectrum of CO2. O2 collision broadening
causes a decrease in measured CO2 of approximately -0.75% per 10% increase in O2 from standard
conditions. A software-selected (user-selectable) 02 compensation option is provided to correct for
high O2, assuming a gas composition of 60% O2 (0% N20). CO2 values reported on both the N-6000
main monitoring sereen and the service sereen are compensated for this gas mixture if the O2
compensation option is selected.
2.4.5 Water Vapor Effect
Water vapor also has an effect on CO2 measurements. In normal use, it is assumed that
respiratory gas is at standard airway conditions of 33°C, fully saturated. Under these conditions,
water vapor (with a vapor pressure of 38 mmHg) causes an increase in measured CO2 of 6%. The
N-6000 is calibrated to include this effect, and CO2 values reported on the main monitoring screen
are automatically compensated, while those on the service screen are not. If applying a dry test gas
to verify calibration, CO2 values reported on the service screen should be used for comparison.
2.4.6 BTPS/ATPS Compensation
The N-6000 assumes that measured respiratory gases are at standard airway conditions of airway
temperature and pressure fully saturated (ATPS). That is, it is assumed that the gas in the airway
adapter is measured at 33 °C, fully saturated with a water vapor pressure of 38 mmHg, at ambient
barometric pressure. By convention, CO2 values are reported on the main monitoring screen after
conversion to deep lung conditions of body temperature and pressure fully saturated (BTPS): 37 °C,
fully saturated with a water vapor pressure of 47 mmHg, at ambient barometric pressure. Service
screen values do not have these corrections applied.
2.4.7 Summary: Reported CO2 Values on the Main Monitoring and Service Screens
CO2 values reported on the service screen are uncorrected for BTPS/ATPS conditions (including
water vapor correction). That is, CO2 values reported on the service screen are accurate assuming
a dry test gas is present in the airway adapter (at 25 °C). Corrections for N20 and Oz, if selected, are
also applied to the service screen values.
CO2 values reported on the main monitoring screen have all corrections applied: BTPS/ATPS,
water vapor, and, if selected, N20 and O2.

2.5 FACTORY CALIBRATED SENSOR
Each CO2 sensor is individually factory-calibrated over multiple gas concentrations and multiple
temperatures. The N-6000 sensor is temperature-regulated to 42 °C, which keeps the sensor optical
components and electronics at a known constant temperature. Additionally, the sensor is factory-
calibrated over multiple temperatures, so that any deviation from the 42 °C set-point is
automatically compensated by temperature calibration coefficients stored with each sensor unit.