CWE GEMINI User manual

GEMINI
End-tidal O2& CO2Analyzer
©CWE 2023
Read instructions carefully before operating this device.
 This device is not to be used for Human Life Support applications.
 To avoid possible electrical shock, do not operate this device if is wet or has had
liquids spilled onto it.
 Service or calibration procedures should only be performed by qualified
personnel familiar with the electrical hazards of line-powered devices.
Ardmore PA 19003 U.S.A.
[phone]
[email protected]
Instruction Manual
www.cwe-inc.com

GEMINI O2& CO2Analyzer Instruction Manual 2
©2023 CWE, Inc.
STATEMENT OF WARRANTY
IF THIS INSTRUMENT FAILS WITHIN A PERIOD OF ONE YEAR FROM THE DATE OF
DELIVERY OR INSTALLATION, CWE, INC. WILL, AT ITS OPTION, REPAIR OR
REPLACE IT FREE OF CHARGE TO THE PURCHASER. THIS WARRANTY
EXCLUDES DAMAGE INCURRED THROUGH ABUSE OR ACCIDENT AND
CONSUMABLE ITEMS OR COMPONENTS SUCH AS BATTERIES. CWE, INC. DOES
NOT ASSUME ANY LIABILITY FOR ANY CONSEQUENTIAL DAMAGES RESULTING
FROM THE USE OR MISUSE OF THIS INSTRUMENT. THIS WARRANTY IS
APPLICABLE ONLY TO THE ORIGINAL PURCHASER OF THE INSTRUMENT, AND IS
NON-TRANSFERRABLE.
IF YOU HAVE A PROBLEM
Please call or write describing your problem. We can often identify what is wrong, and
suggest a solution without recourse to returning the device. Defective units under
warranty should be returned to the factory along with a note describing the nature of the
fault. Every effort will be made to ensure prompt repair or replacement of the device.
FACTORY SERVICE
Out of warranty or damaged instruments may be returned to the factory postage prepaid
for service at prevailing rates. Upon request, a written or verbal quotation for such service
will be issued after examination of the unit but prior to commencing repairs or service.
Address requests for service or technical information to:
CWE, Incorporated
Technical Support Department
TEL [phone]
[email protected]
LIFE SUPPORT POLICY
Instruments manufactured by CWE, Incorporated are not authorized for use as critical
components in human life support devices or systems. "Life support devices or systems",
as used herein, are devices or systems whose failure to perform, whether through misuse,
failure, or proper operation, can reasonably be expected to result in significant injury to
the operator or subject persons.
This document last updated on July 28, 2023.

GEMINI O2& CO2Analyzer Instruction Manual 3
©2023 CWE, Inc.
TABLE OF CONTENTS
1.0 INTRODUCTION............................................................................................ 4
3.0 SETTING UP THE GEMINI............................................................................ 6
4.0 OPERATION.................................................................................................. 7
4.1 SAMPLE FLOW............................................................................................. 7
4.11 MINIMIZING SAMPLE TUBING VOLUME .................................................. 7
4.12 SAMPLE FLOW RATE................................................................................ 7
4.2 CONDITIONING THE SAMPLE..................................................................... 8
4.3 LCD DISPLAY ............................................................................................... 8
4.4 CALIBRATION............................................................................................... 9
4.5 END-TIDAL OR FAST CO2DISPLAY SWITCH............................................ 9
4.6 SETTING AND USING THE ALARMS .......................................................... 9
4.7 ANALOG OUTPUT SIGNALS (REAR PANEL)........................................... 10
4.8 RS232 OUTPUT (REAR PANEL)................................................................ 10
5.0 MAINTENANCE........................................................................................... 11
6.0 ORDERING INFORMATION........................................................................ 12
CONNECTION DIAGRAMS............................................................................... 13

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©2023 CWE, Inc.
1.0 INTRODUCTION
The GEMINI is a high-performance respiratory gas analyzer for the routine
monitoring of expired carbon dioxide and oxygen gas concentrations and respiratory
rate. For CO2, a temperature-controlled, infrared optical bench is used, which
features fast response, excellent accuracy, and long-term stability. Oxygen
measurement is accomplished using an advanced design, rapid response
paramagnetic analyzer. Respiratory rate is computed on a breath-by-breath basis
from the CO2excursions. The unit is completely self- contained: the sensors, control
electronics, displays, and sampling pump are housed in a rack-mountable
enclosure.
The digital readout of CO2concentration shows either the instantaneous value, or
the peak end-tidal value. The O2concentration is shown as a continuous reading.
Analog outputs provide a linear voltage corresponding to the current gas
concentrations and respiratory rate. An RS232 serial output is provided for
connection to an external computer, whereby data can be independently collected
and analyzed.
The GEMINI has built-in audible and visual alarms for detecting out-of-range end-
tidal CO2or respiratory rate conditions. These alarms have adjustable high and low
limits, which are remembered by the instrument and reinstated when it is next used.
A special feature of the GEMINI is an open module slot that can hold any of the
SYSTEM 1000 instrumentation modules. Available modules include a
cardiotachometer, blood pressure monitor, and many other functions. This flexibility
allows the GEMINI to serve as a full-featured physiological monitoring system.
GEMINI Respiratory Gas Analyzer front panel

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©2023 CWE, Inc.
2.0 SPECIFICATIONS
Carbon dioxide analyzer..............................................................single beam infrared
Sample cell materials.................................................sapphire and stainless steel
Sample inlet connector .......................................................................Luer female
Measurement range.............................................................................0-10% CO2
Analog output scaling ....................................................................1.1V/% (0-10V)
Linearity ............................................................................................... 0.1% CO2
Repeatability..........................................................................................0.1% CO2
Response time (T10 - T90)..................................... 120mS at 100 ml/min sampling
Response time (T10 - T90) .......................................150mS at 50 ml/min sampling
Zero stability ....................................................... 0.1% (8 hours), 0.2% (24 hours)
Interference effects: 50% N2O .........0.1% at 0% CO2, 0.6% at 5% CO2(uncomp.)
N2O compensation (internal jumper for 25, 50, 75%) ..................0.1% at 5% CO2
Maximum sample cell pressure.................................................................+ 5 psig
Interference effects: vaporized anaesthetic agents .................................negligible
Operating temperature range.....................................................................5-40° C
Optical bench temperature ..........................................................48° C, controlled
Warm-up time.........................................................6 min to 0.2%, 10 min to 0.1%
Oxygen analyzer .................................................................................. paramagnetic
Linearity ..................................................................................................0.1% O2
Repeatability ...............................................................................<0.01% O2/hour
Zero stability ...................................................................................+0.1% O2/day
Response time ....................................................................................... <200mS
Operating temperature ............................................................................0 –65oC
Maximum pressure ....................................................................................15 psi
Maximum sample flow ....................................................................... 250 ml/min
Measurement range ...................................................0 –100% (0 –95% usable)
Sample flowmeter............................................................................. 20 - 200 ml/min
Calibration controls (O2, CO2)............................................. Zero, Span (10-turn dials)
Respiratory rate measurement range ......................................... 5 –120 breaths/min
Alarm adjustment range: CO2...................................................................1.0 –9.9%
Alarm adjustment range: Respiratory rate .................................. 5 –120 breaths/min
Analog signal outputs (rear panel) ............................................................BNC jacks
CO2 output scaling ............................................................................... 1.0V / %CO2
O2 output scaling .................................................................................... 0.1V / %O2
Respiratory rate output scaling ............................................................. 0.05V / bpm
Alarm output ................................................... 5V if alarm condition, 0V if no alarm
Serial data output format ............................... 9600 baud, 8 data, no parity, 1 stop bit
Electrical requirements........................................ 120VAC/220VAC switchable, 35VA
Dimensions (main unit) ........................19W x 5.25H x 16D in., 49W x 13H x 41D cm
Weight.................................................................................................. 10 lbs. (4.5kg)

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©2023 CWE, Inc.
3.0 SETTING UP THE GEMINI
Place the GEMINI control unit in a stable location close to the subject or animal
being monitored. Note that the output signals are on the rear panel. When
monitoring small animals, it is desirable to locate the unit as close to the animal as
possible, to minimize sample tube volume.
Be sure the VOLTAGE SELECTOR switch on the rear panel is set correctly. Plug
the included power cord into the receptacle on the rear panel, and the other end
into a grounded AC outlet.
Attach the sample tubing to the SAMPLE INLET port on the front panel. This
should be flexible tubing (Tygon or similar), with an inside diameter of 0.050 -
0.062" (1.25 - 1.60 mm). For long-term monitoring, it is recommended that the
included Nafion sample tubing be used. This tubing, recognizable by its braided
appearance, passes water vapor through its membrane, thus drying the sample
gas. Whatever tubing is used, be sure that the miniature in-line filter is always in
place. This filter is the final line of defense that prevents water from entering the
sample cells.
Switch POWER on. The digital display should come on, showing a “welcome”
message, indicating that the unit is receiving power and operating. Adjust the
SAMPLE FLOW appropriately. The higher the sample flow, the faster the response of
the instrument.
The unit requires about ten minutes to warm up and stabilize. After about 5
minutes, the analyzer will be usable, with an accuracy of 0.2%. After 10 minutes,
the full rated accuracy of 0.1% will be available. Warm-up time depends on the
ambient temperature.
See the remainder of this manual for the various operating modes and controls.

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©2023 CWE, Inc.
4.0 OPERATION
4.1 SAMPLE FLOW
The flowmeter on the front panel is used to regulate the sample flow to the
sensing cells. The higher the flow rate, the faster the response of the
analyzer. If possible, select a flow rate in the 35 - 100 ml/min range.
Smaller flow rates can be used, with a consequent increase in response
time.
The GEMINI monitor can be used with a wide range of animals. For use
with rodents and similar sized animals, special considerations are
necessary because of their very small volumes and fast respiratory rates.
In general, the sample flow rate should be kept as high as practicable to
ensure fast analyzer response. In addition, the volume of the sample
tubing must be as small as possible to prevent sample dilution and
minimize the gas transit time from the sample point to the analyzer cell. If
the following suggestions are followed, good end-tidal measurements can
be achieved with small animals.
4.11 MINIMIZING SAMPLE TUBING VOLUME
Ideally, the SAMPLE INLET should be connected directly to the
endotracheal tube as close to the animal as possible, ALWAYS
using a small hydrophobic in-filter at the GEMINI SAMPLE INLET port.
Several centimeters of small-bore tubing is acceptable between the
sample port and the tracheal connection if the sample rate is kept
reasonably high. Avoid large moisture absorbers, which typically
have a substantial internal volume. Moisture-reducing sample
tubing, such as DuPont Nafion®, is ideal, and is included in the
Accessories Kit (Part No. 11-01101) provided with the instrument.
The CO2sample cell itself is heated and will not condense water
vapor. Be careful to keep the sample tubing free of liquid water,
however.
4.12 SAMPLE FLOW RATE
The response time of the analyzer is directly proportional to the
sample flow rate. Although the analyzer will work with rates as low
as 20cc/min, optimum response time is realized with sampling in
the 35 –100 ml/min range. To avoid depleting the available expired
volume with mechanically ventilated small animals, the analyzer
sample flow can be returned to the breathing circuit. This will result
in a net volume change of zero. The SAMPLE OUTLET port on the
rear panel is provided for this purpose. Be sure to return the volume
to a point distal from the sample point to prevent diluting the end-
tidal sample.

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©2023 CWE, Inc.
4.2 CONDITIONING THE SAMPLE
It is extremely important that no condensed water or other fluids enter the
sample cells. Such contamination will shift the zero or make zeroing the
instrument impossible. A moisture blocking filter should be used between
the sample site and the SAMPLE INLET. DuPont Nafionsample lines are
also available, which remove water vapor from the gas sample. The
sample tubing should be inspected periodically to ensure there is no
trapped moisture. If visible water has condensed in this tubing, it should
be disconnected and dried using compressed air. Water entering the CO2
sample cell will cause unstable reading and zero offsets. If water or other
contaminants have entered the instrument, see Section 5.0 and Appendix
A for cell-cleaning procedures.
4.3 LCD DISPLAY
The front-panel lcd display shows all current measurements, the settings
and state of the programmable alarms, and a graphical display of the CO2
concentration. During normal operation, the display will appear as follows:
CO25.4% O220.9%
Resp 15 ALM: OFF
<3.0/7.5> <010/100>
|||||||||||
The first line of the display shows the current CO2and O2concentrations.
The second line shows the respiratory rate in breaths/minute, and what (if
any) alarms are currently active. The fourth line shows a bar graph of the
fast CO2measurement. This serves as a quick visual indicator of changing
CO2. The fourth line also serves as a message area for special conditions,
such as alarms or errors.

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©2023 CWE, Inc.
4.4 CALIBRATION
Calibrating the GEMINI is straightforward. Because of the inherent linearity
of the analyzers, only a two-point calibration is required. For CO2
calibration, a 5% CO2in air calibration mixture is ideal. For O2calibration,
100% nitrogen or other oxygen-free gas is required. Each gas has its own
set of ZERO and SPAN controls for calibration.
CO2:With the instrument fully warmed-up, and the SAMPLE INLET port
opened to room air, adjust the ZERO knob to achieve a reading of 0.0%
Once a stable zero has been established, a known calibration gas is
introduced to the SAMPLE INLET. Adjust the SPAN knob until the display
indicates the concentration of the calibration gas.
O2:Allow the instrument to sample the 100% N2(or other zero-oxygen
gas), and adjust the ZERO control until the display reads 0.0%. Open the
sample line to room air, and adjust the SPAN control until the display reads
20.9%
4.5 END-TIDAL OR FAST CO2DISPLAY SWITCH
The lcd display on the GEMINI can report CO2concentration in either a
continuous reading (FAST), or as the peak expired value (END TIDAL).
Note that the CO2output (rear panel) always provides the fast response
signal.
4.6 SETTING AND USING THE ALARMS
This GEMINI provides user-selectable alarms for end-tidal CO2(ETCO2)
and respiratory rate. Either alarm can be activated independently, and
both have adjustable upper and lower alarm limits. When an alarm is
activated, the ALARM LED will light, and a beep will sound according to the
following pattern:
CO2 out of range: beep every 2 seconds
Resp. rate out of range: beep every 5 seconds
To set either alarm range, move the CO2 ALARM or RESP RATE ALARM lever
switch to either the HI (up) or LO (down) position, and hold it there while
turning the SET knob. The alarm setting selected will change on the
display:
<3.5/6.0> <30/60>
The left-hand group is the low and high CO2range, respectively; the right-
hand group is the respiratory rate range.
The lower two lever switches are used to activate the alarms. The lcd
display shows which alarms (if any) are currently active.

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©2023 CWE, Inc.
4.7 ANALOG OUTPUT SIGNALS (Rear Panel)
Analog outputs are provided for CO2concentration, O2concentration,
respiratory rate, and the alarm status. These signals are scaled as follows:
CO2output 1.0V / %CO2
O2output 0.1V / %O2
Respiratory rate 0.05V / bpm
Alarm status 5V if alarm, 0V if no alarm
4.8 RS232 OUTPUT (Rear Panel)
A serial interface is provided for external data collection and analysis. Two
formats are available, which are selected by the SERIAL FORMAT SWITCH
(rear panel). A sample of each is shown:
format 1 ETCO2, ETO2, rate 5.5,16.3,23<cr>
format 2 CO2(fast), O2(fast) 4.5,17.0<cr>
FORMAT 1is sent out once-per-breath; FORMAT 2is sent every 50mS (200
samples/sec). These numbers are sent as simple ASCII characters,
separated by commas, and each data set ends with a <cr> character
(ASCII 13). This format allows for easy importation into spreadsheets or
other analysis software.
The protocol used is 9600,N,8,1 which is almost universally available
using any terminal program ( e.g., Windows HyperTerminal).