VIASYS Bear Cub 750PSV Service Manual
Service Manual
Bear Cub 750PSV
© Copyright 2004, VIASYS Healthcare Critical Care
L2346 Revision B June 2004
2 Bear Cub 750PSV
Revision History
Date Revision Pages Changes
June 2003 A All Release
June 2004 B All Release manual in VIASYS Healthcare
template using VIASYS Healthcare Critical
Care nomenclature.
L2346 Revision B June 2004
Service Manual 3
Contact and Ordering Information
United States, Latin America, Asia Pacific:
Sales, Service and Clinical Support:
VIASYS Healthcare
Critical Care Division
22705 Savi Ranch Parkway
Yorba Linda, CA 92887
Phone: (714) 283-8444
(800) 381-3552
Fax: (714) 283-8493
www.VIASYShc.com
United Kingdom:
Sales, Service and Clinical Support:
VIASYS Healthcare
3 Welton Rd.
Warwick,
CV34 5PZ
Phone: 01926 490888
Fax: 01926 402262
Europe
Sales and Customer Service Technical Service
VIASYS Healthcare VIASYS Healthcare
Critical Care Division Leibnizstrasse 7
22705 Savi Ranch Parkway D-97204 Hoechburg
Yorba Linda, CA 92887 Germany
Phone: (714) 283-8444 Phone +49 (0) 931 4972 – 0
(800) 381-3552 Fax:+49 (0) 931 4972 –423
e-mail: Support.CC.EU@VIASYShc.com
website: www.VIASYShc.com
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4 Bear Cub 750PSV
CAUTION
Federal law (USA) restricts this device to sale by or on the order of a physician.
CAUTION
Not suitable for use in the presence of flammable anesthetics.
CAUTION
Service and/or repair of this instrument is restricted to VIASYS Healthcare authorized
or VIASYS Healthcare Trained Personnel only.
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Service Manual 5
Warranty
The Bear Cub 750PSV is warranted to be free from defects in material and
workmanship and to meet the published specifications for One (1) year from date of
shipminent.
The liability of VIASYS Healthcare, Critical Care Division, (referred to as the
Company) under this warranty is limited to replacing, repairing or issuing credit, at
the discretion of the Company, for parts that become defective or fail to meet
published specifications during the warranty period; the Company will not be liable
under this warranty unless (A) the Company is promptly notified in writing by Buyer
upon discovery of defects or failure to meet published specifications; (B) the
defective unit or part is returned to the Company, transportation charges prepaid by
Buyer; (C) the defective unit or part is received by the Company for adjustment no
later than four weeks following the last day of the warranty period; and (D) the
Company’s examination of such unit or part shall disclose, to its satisfaction, that
such defects or failures have not been caused by misuse, neglect, improper
installation, unauthorized repair, alteration or accident.
Any authorization of the Company for repair or alteration by the Buyer must be in
writing to prevent voiding the warranty. In no event shall the Company be liable to
the Buyer for loss of profits, loss of use, consequential damage or damages of any
kind based upon a claim for breach of warranty, other than the purchase price of any
defective product covered hereunder.
The Company warranties as herein and above set forth shall not be enlarged,
diminished or affected by, and no obligation or liability shall arise or grow out of the
rendering of technical advice or service by the Company or its agents in connection
with the Buyer's order of the products furnished hereunder.
Limitation of Liabilities
This warranty does not cover normal maintenance such as cleaning, adjustment or
lubrication and updating of equipment parts. This warranty shall be void and shall not
apply if the equipment is used with accessories or parts not manufactured by the
Company or authorized for use in writing by the Company or if the equipment is not
maintained in accordance with the prescribed schedule of maintenance.
The warranty stated above shall extend for a period of One (1) year from date of
shipment, with the following exceptions:
1. Components for monitoring of physical variables such as temperature,
pressure, or flow are warranted for ninety (90) days from date of receipt.
2. Elastomeric components and other parts or components subject to
deterioration, over which the Company has no control, are warranted for sixty
(60) days from date of receipt.
3. Internal batteries are warranted for ninety (90) days from the date of receipt.
The foregoing is in lieu of any warranty, expressed or implied, including, without
limitation, any warranty of merchantability, except as to title, and can be amended
only in writing by a duly authorized representative of the Company.
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6 Bear Cub 750PSV
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Service Manual 7
Contents
Revision History .................................................................................... 2
Contact and Ordering Information ...............................................................................3
Warranty .........................................................................................................................5
Limitation of Liabilities.................................................................................................... 5
Contents .........................................................................................................................7
List of Figures ................................................................................................................9
List of Tables................................................................................................................ 11
Chapter 1: Specifications ...................................................................13
Modes............................................................................................................................ 13
Controls ........................................................................................................................13
Alarms...........................................................................................................................15
Monitors........................................................................................................................17
Preset Values ............................................................................................................... 19
Emissions/Susceptibility............................................................................................. 19
Outputs .........................................................................................................................19
Inputs ............................................................................................................................20
Physical Dimension and Shipping Information......................................................... 20
Environmental Specifications..................................................................................... 21
Method of Sterilization/Disinfection ........................................................................... 21
Cleaning........................................................................................................................22
Sterilization...................................................................................................................22
Chapter 2: Theory of Operation .........................................................23
Overview .......................................................................................................................23
Ventilator pneumatics - General description............................................................. 25
Gas Inlet Conditioning................................................................................................. 25
Blender.......................................................................................................................... 25
Flow Control Valve....................................................................................................... 25
AOPR Valve/Sub-Ambient Valve/ Dump Solenoid ....................................................26
Auxiliary Gas Outlet..................................................................................................... 26
Pressure Control System ............................................................................................26
Exhalation Valve .......................................................................................................... 27
Flow Sensor.................................................................................................................. 27
Ventilator Electronics ..................................................................................................27
Power Supply ...............................................................................................................28
Ventilator Software ......................................................................................................28
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8 Bear Cub 750PSV
Chapter 3 OVP Recommended Service ........................................... 29
Operational Verification .............................................................................................. 29
Equipment Required.................................................................................................... 29
Test Procedures........................................................................................................... 32
Exterior Inspection and Cleaning............................................................................... 34
Exterior Cleaning ......................................................................................................... 34
Plugs and Cables ........................................................................................................ 34
OVP Checklist .............................................................................................................. 35
Verification Steps......................................................................................................... 35
Chapter 4 Calibration (for software releases 2 and 3 only)........... 37
Introduction .................................................................................................................. 37
Pressure Transducers and Flow Control Valve Calibration .................................... 38
Air and O2 Regulator Balance..................................................................................... 41
Objective...................................................................................................................... 41
Equipment ................................................................................................................... 41
Requirements .............................................................................................................. 41
Chapter 5 Schematics and Assemblies ........................................... 45
Chapter 6 Troubleshooting ............................................................... 69
Chapter 7 Removal & Replacement.................................................. 73
Interior Access ............................................................................................................. 73
Flow Valve Assembly Removal .................................................................................. 74
Control PCB Removal.................................................................................................. 75
Display PCB Removal.................................................................................................. 76
Air/O2 Regulator Removal ........................................................................................... 76
Blender Removal.......................................................................................................... 77
Exhalation Valve Removal .......................................................................................... 78
Chapter 8 Preventive Maintenance................................................... 79
Replacement Parts ...................................................................................................... 79
Recommended Service Procedure............................................................................. 79
Exterior Inspection ...................................................................................................... 80
Interior Inspection........................................................................................................ 80
Specifications............................................................................................................... 80
Calibration and Verification Procedure ..................................................................... 80
Ground Resistance Test.............................................................................................. 81
Current Leakage Test .................................................................................................. 81
Operational Verification Procedure............................................................................ 81
Chapter 9 RS-232 Protocol............................................................... 83
Scope ............................................................................................................................ 83
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Hardware Definition ..................................................................................................... 83
Pin Assignment............................................................................................................ 83
Software Protocol ........................................................................................................ 84
Continuous Output (Default Mode) .............................................................................. 84
Data Upon Request ..................................................................................................... 84
Data Format................................................................................................................. 84
Chapter 10 Parts List.......................................................................... 93
Chapter 11 Repackaging Instructions ............................................... 95
General.......................................................................................................................... 95
Packaging Instructions ............................................................................................... 95
Procedure ..................................................................................................................... 95
Index ..................................................................................................... 97
List of Figures
Figure 2-1: Top Level Block Diagram ............................................... 23
Figure 2-2: Pneumatics System Schematic ..................................... 24
Figure 3-1: Bear Cub 750PSV US with Patient Circuit ....................33
Figure 5-1: Power Supply Module Assembly (1 of 2) ...................... 45
Figure 5-2: Power Supply Module Assembly (2 of 2) ....................... 46
Figure 5-3: Schematic Diagram, Pneumatic 750PSV .......................47
Figure 5-4: Power Supply PCB Assembly (1 of 3) ............................ 48
Figure 5-5: Power Supply PCB Assembly (2 of 3) ............................ 49
Figure 5-6: Power Supply PCB Assembly (3 of 3) ............................ 50
Figure 5-7: Pneumatic Tubing Diagram............................................. 51
Figure 5-8: Display PCB (1 of 3) ......................................................... 52
Figure 5-9: Display PCB (2 of 3) ......................................................... 53
Figure 5-10: Display PCB (3 of 3)....................................................... 54
Figure 5-11: Control PCB Assembly.................................................. 55
Figure 5-12: Wiring Diagram............................................................... 56
Figure 5-13: Power Supply Schematic ..............................................57
Figure 5-14: Control Schematic PCB (1 of 5) .................................... 58
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10 Bear Cub 750PSV
Figure 5-15: Control Schematic PCB (2 of 5).................................... 59
Figure 5-16: Control Schematic PCB (3 of 5).................................... 60
Figure 5-17: Control Schematic PCB (4 of 5).................................... 61
Figure 5-18: Control Schematic PCB (5 of 5).................................... 62
Figure 5-19: Display Schematic PCB (1 of 4).................................... 63
Figure 5-20: Display Schematic PCB (2 of 4).................................... 64
Figure 5-21: Display Schematic PCB (3 of 4).................................... 65
Figure 5-22: Display Schematic PCB (4 of 4).................................... 66
Figure 5-23: BEAR CUB 750PSV Overlay (P/N 51-09640-00)........... 67
Figure 6-1: Troubleshooting Decision Tree...................................... 69
Figure 7-1: Cover Removal................................................................. 73
Figure 7-2: Standoff Tube Removal................................................... 74
Figure 7-3: Opening of Front Portion ................................................ 74
Figure 7-4: Flow Valve Assembly ...................................................... 75
Figure 7-5: Control PCB ..................................................................... 75
Figure 7-6: Display PCB ..................................................................... 76
Figure 7-7: Air / O2 Fittings................................................................. 76
Figure 7-8: Air / O2 Regulator Assembly ........................................... 77
Figure 7-9: Oxygen % Knob ............................................................... 77
Figure 7-10: Blender Removal ........................................................... 78
Figure 7-11: Blender Assembly ......................................................... 78
Figure 7-12: Exhalation Valve Assembly .......................................... 78
Figure 8-1: Ventilator Back Panel ...................................................... 81
Figure 11-1: Repacking Procedure.................................................... 96
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List of Tables
Table 3-1: Standard Settings ............................................................. 30
Table 3-2: Rate.................................................................................... 30
Table 3-3: Exhalation Time and I/E Ratio Table ............................... 30
Table 4-1: Control PCB Transducer Calibration .............................. 38
Table 4-2: Calibration ......................................................................... 39
Table 4-3: Diagnostic Function ......................................................... 40
Table 4-4: Inspiratory Flow Calibration ............................................ 41
Table 4-5: Regulator Balance ............................................................ 42
Table 4-6: Standard Test Settings..................................................... 43
Table 6-2: Troubleshooting ................................................................70
Table 9-1: Pin Assignment.................................................................. 83
Table 9-2: Alternate Pin Assignment ................................................. 84
Table 9-3: Valid Requests Received by the Ventilator .................... 85
Table 9-4: Valid Message Transmitted by the Ventilator ................ 85
Table 9-5: Real Time Data .................................................................. 86
Table 9-6: Adult Ventilator Control Settings .................................... 87
Table 9-7: Adult Ventilator Alarm Settings / Status.........................88
Table 9-8: Adult Ventilator Monitor Status....................................... 89
Table 9-9: Infant Ventilator Control Settings ...................................90
Table 9-10: Infant Ventilator Alarm Settings / Status ...................... 91
Table 9-11: Infant Ventilator Monitor Status .................................... 92
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12 Bear Cub 750PSV
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Service Manual 13
Chapter 1: Specifications
Modes
A/C
In the Assist/Control position, a mechanical breath is delivered with each inspiratory
effort, provided the patient satisfies the assist sensitivity criteria. If the patient does
not meet the assist sensitivity criteria, the ventilator automaticallydelivers breaths
according to the Ventilator Rate control. Mechanical breaths may then be either
patient initiated (assisted) or ventilator initiated (controlled).
SIMV/IMV
In the SIMV/IMV position, a combination of mechanical and spontaneous breath
types is available. Mechanical breaths, either assisted or controlled, are delivered at
the set ventilator rate while all other breaths are spontaneous. Disabling the assist
sensitivity mechanism. or removing the flow sensor from the ventilator, will cause the
equivalent of IMV mode of ventilation to exist.
CPAP
In the CPAP position, the Base Flow control establishes the continuous flow
available for spontaneous breathing.
STANDBY
The STANDBY position discontinues all electrical controls and functions with the
exception of the charging system for the internal battery.
NOTE
If the ventilator is connected to air and O2 sources, blended gas will circulate while
ventilator is in the STANDBY position, making gas available from the Auxiliary Gas
Outlet. The amount of gas flow circulating is determined by the Base Flow setting.
Controls
Rate
Range: 1 to 150 BPM
Resolution: 1 from 1 to 100BPM
2 from 100 to 150 BPM
Tolerance: Greater of ± 1 BPM or 0.02 seconds applied to the Breath
Interval
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14 Bear Cub 750PSV
Inspiratory Time
Range: 0.10 to 3.0 seconds
Resolution: 0.01 from 0.10 to 0.50 seconds
0.02 from 0.50 to 1.70 seconds
0.05 from 1.70 to 3.00 seconds
Accuracy: ± 0.02 seconds from 0.10 to 0.50 seconds
± 0.025 seconds from 0.50 to 3.00 seconds
Inspiratory Flow
Range: 1 to 30 L/min
Resolution: 0.5 L/min from 1 to 10 L/min
1.0 L/min from 10 to 30 L/min
Accuracy: Pressures 0 to 60 cmH2O: ± 0.5 L/min or ± 10% of setting,
whichever is greater.
Pressure 60 to 72 cmH2O: ± 0.5 L/min or + 10%/- 15% of
setting, whichever is greater.
Baseline Flow
Range: 1 to 30 L/min
Resolution: 0.5 L/min from 1 to 10 L/min
1.0 L/min from 10 to 30 L/min
Accuracy:Pressures 0 to 60 cmH2O: ± 0.5 L/min or ± 10% of setting, whichever is
greater.
Pressure 60 to 72 cmH2O: ± 0.5 L/min or + 10%/- 15% of
setting. Whichever is greater
Volume Limit™
Range: 5 to 300 ML
Resolution: 1 ML from 5 to 50 ML
2 ML from 50 to 150 ML
5 ML from 150 to 300 ML
Accuracy: ± 2 ML or ± 10% of setting, whichever is greater
PEEP
Range: 0 to 30 cmH2O
Resolution: 1 cmH2O
Repeatability: ± 1 cmH2O or ± 5%, whichever is greater
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Service Manual 15
Inspiratory Pressure
Range: 0 to 72 cmH2O
Resolution: 1 cmH2O from 0 to 30 cmH2O
2 cmH2O from 30 to 72 cmH2O
Repeatability: ± 1 cmH2O or ± 5% whichever is greater. Breath to breath
Manual Breath
Range: X1
Assist Sensitivity
Range: 0.2 to 5.0 L/min
Resolution: 0.2 at 0.2 L/min increasing to 0.5 at 5.0 L/min
Accuracy:Not a calibrated scale, minimum setting accuracy is ± 0.1 L/min
Over Pressure Relief
Range: (Pressure at the patient wye): 15
to 75 cmH2O
Resolution: 2 cmH2O stability (repeatability) ±4 cmH2O
%02 Blending
Range: 21 to 100% Oxygen concentration
Resolution: 1%
Accuracy: ± 3% oxygen
APNEA Interval
Range: 5, 10, 20, or 30 seconds
Accuracy: ± 1 second
Alarms
Alarm Loudness
Range: Min. to Max. 60 to 75 db(A)
High Breath Rate
Range: 3 to 255 BPM
Low PEEP/CPAP
Range: -5 to 30 cmH2O
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16 Bear Cub 750PSV
Low Inspiratory Pressure
Range: 1 to 65 cmH2O
Patient Circuit
LED On/Off
Failed to Cycle
LEd On/Off
Low Gas Supply
LED On/Off
Apnea
LED On/Off
Settings Incompatible
LED On/Off
Pressure Settings Incompatible
LED On/Off
Prolonged Inspiratory Pressure
LED On/Off
Flow Sensor
LED On/Off
Low Battery
LED On/Off
Alarm Silence
60 seconds
Visual Reset
Push Button
High Pressure Limit
Range: 10 to 75 cmH2O
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Service Manual 17
Line Power
Green/Red LED
Monitors
Total Breath Rate
Range: 0 to 255 BPM
Resolution: 1 BPM from 0 to 100 BPM
2 BPM from 100 to 150 BPM
3 BPM from 150 to 255 BPM
Exhalation Minute Volume
Range: 0 to 30.0 L/min
resolution: 0.01 L/min from o to 1.00 L/min
0.02 L/min from 1 to 2.00 L/min
0.05 L/min from 2 to 5.0 L/min
0.10 L/min from 5 to 10.0 L/min
0.20 L/min from 10 to 30.0 L/min
Accuracy: Accuracy of the exhaled minute volume is a function of both
volume and breath rate. To evaluate the performance of this
monitor the accuracy of both tidal volume and breath rate must
be combined
Exhaled Tidal Volume
Range: 0 to 500 ML
Resolution: 0.1 ML from 0.0 to 99.9 ML
1.0 ML from 100 to 500 ML
Accuracy: ± 1 ML or ± 10%, whichever is greater
% of Tubing Leakage
Range: 0 to 100%
Resolution: 1%
Accuracy: ± 2% or ± 1 ML
Inspiratory Time
Range: 0 to 3.10 seconds
Resolution: 0.01 seconds
Accuracy: ± 0.02 seconds
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18 Bear Cub 750PSV
Expiratory Time
Range: 0 to 99.9 seconds
Resolution: 0.01 seconds from 0 to 99.9 seconds
0.10 seconds from 10.0 to 99.9 seconds
Accuracy: ± 0.02 seconds
I:E Ratio
Range: 9.9:1 to 1:9.9
Accuracy: ± 0.1 or ± 20 mseconds, whichever is greater
Peak Inspiratory Pressure
Range: 0 to 99 cmH2O
Resolution: 1 cmH2O
Accuracy: ± 2 cmH2O or ± 5% of reading, whichever is greater
Mean Airway Pressure
Range: 0 to 75 cmH2O
Resolution: 0.5 cmH2O
Accuracy: ± 2 cmH2O or ± 3% of reading, whichever is greater
Inlet O2 Pressure
Range: 0 to 100 PSIG
Resolution: 1 PSIG
Accuracy: ± 5 PSIG
Proximal Airway Pressure
Range: -10 to 100 cmH2O
Resolution: 1 cmH2O
Accuracy: ± 1 cmH2O from -10 to 20 cmH2O
± 2 cmH2O from 20 to 65 cmH2O
± 3 cmH2O from 65 to 100 cmH2O
Hourmeter
Range: 0 to 99,999 hours
Resolution: 0.1 hour
Accuracy: ± 2% of reading
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Service Manual 19
Breath Type (Patient Initiated)
LED
Test
Push Button
Battery
LED On/Off
Preset Values
Minimum Expiratory Time 150 milliseconds
Maximum Inspiratory Time 3.10 seconds
Maximum settable I:E Ratio 4:1
Model 9300
Classification Class 1
Degree of Protection
Electric Shock Type B
Harmful Ingress of Water None (Ordinary Equipment)
Degree of Safety of Application
in Presence of Flammable Anesthetics None
Mode of Operation Continuous
Emissions/Susceptibility
This ventilator has been tested to conform to the following specifications:
MIL-STD-461D:1993,MIL-STD-462D:1993, EN55011:1991, IEC 1000-4-2:1994, IEC
1000-4-3:1994, IEC 1000-4-4:1994, IEC 1000-4-5:1994, QUASI-STATIC:1993.
This ventilator is designed and manufactured to comply with the safety requirements
of IEC 601-1, IEC 601-2-12, CAN/CSA-C22.2 No. 601.1-M90, and UL 2601-1.
Outputs
Digital
(see chapter 9) RS-232 Bi-Directional
Analog
Proximal Pressure -10 to 100 cmH2O, 1 cmH2O/25 mv
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20 Bear Cub 750PSV
Proximal Inspiratory/Expiratory Flow -40 (expiratory) to 40 (inspiratory) L/min,
1 L/min/50 mv
Breath Phase 1 “Logic” signal; 0, 5V
Remote Nurse Call 0.5 amps max at 24 vdc max
Pneumatic
Auxiliary Blended Gas Outlet 7 to 17 psig, 0 to 8 L/min
Inputs
Electrical
Supply Ratings
Voltage: 100V 80 to 110 VAC
120V 96 to 132 VAC
220V* 176 to 242 VAC
240V 192 to 264 VAC
Current: 100V 1.0 A maximum
120V 1.0 A maximum
220V 0.5 A maximum
240V 0.5 A maximum
Frequency: 100V 50/60 Hz
120V 50/60 Hz
220V 50/60 Hz
240V 50/60 Hz
Fuses: 100/120V T 0.5 A, 5 x 20 mm
230/240V T 0.25 A, 5 x 20 mm
* For 220V operation, set the power entry module selector switch to 230V setting.
Pneumatic
Oxygen and Air 30 to 80 psig, 50 L/min Supply Ratings
Physical Dimension and Shipping Information
Ventilator Weight 27 lbs., 12 kg
Graphics Display Weight 5.5 lbs.
Pedestal Stand Weight 9 lbs.
Compressor Weight 110 lbs.
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Service Manual 21
Ventilator Dimensions 13.5" W x 10" D x 11" H
Graphics Display Dimensions 13" W x 2.5" D x 9.5" H
Pedestal Stand Dimensions 24" x 40.5" H
Compressor Dimensions 22"W x 21.5"D x 36" H
Shipping Weight Including Ventilator 38 lbs.
Graphics Display 11 lbs.
Pedestal Stand 12 lbs.
Compressor 122 lbs.
Shipping Dimensions
Ventilator 18" W x 18" D x 19" H
Graphics Display 16" W x 13" D x 11" H
Pedestal Stand 25" W x 5" D x 45" H
Compressor 26" W x 22" D x 40" H
Environmental Specifications
Temperature
Storage and Shipping -40 to 158 ºF (-40 to 70 ºC)
Checkout and Operating 50 to 104 ºF (10 to 40 ºC)
Altitude
Checkout, Operating,
Transport and Storage 0 to 9,000 feet (14.7 to 10.5 PSIA/760 to 543 mm Hg)
Humidity
Storage and Shipping 0 to 99% Relative Humidity — Non-condensing
Checkout and Operating 0 to 95% Relative Humidity — Non-condensing
Method of Sterilization/Disinfection
NOTE
See also the BEAR CUB™ 750PSV Infant Ventilator Instruction Manual Cleaning
and Maintenance (chapter 8)
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22 Bear Cub 750PSV
Cleaning
External Surfaces
All external surfaces of the ventilator shall be able to be wiped clean with the
following compounds:
A. Isopropyl Alcohol
B. Chlorine Compounds Maximum Concentration: 1:10
C. Quaternary Ammonium Compounds Maximum Concentration: 1:500
NOTE
These compounds are diluted by volume in water.
Sterilization
All parts of the ventilator that can come in contact with the patient expiratory gas and
all parts of the breathing circuit external to the ventilator shall be sterilizable or
disposable.
Methods of Sterilization
Ethylene oxide, maximum temperature 130 ºF (54 ºC)
Steam sterilization, maximum temperature 250 ºF (121 ºC)
Liquid Sterilization
1. Cidex
Minimum sterilization cycles before part replacement:
1. Patient Circuit, Exhalation Manifold:
Ethylene Oxide 240 cycles
Steam Sterilization 240 cycles
Liquid Sterilization 240 cycles
2. Flow Sensor:
Ethylene Oxide 6 months
Liquid Sterilization 6 months
Pasteurization (using mesh bag) 6 months
3. All other sterilization components:
Ethylene Oxide 120 cycles or 1 year
Steam Sterilization 120 cycles or 1 year
Liquid Sterilization 120 cycles or 1 year
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Service Manual 23
Chapter 2: Theory of Operation
Overview
This chapter describes the operating theory of the BEAR CUB™ 750PSV Infant
Ventilator. The BEAR CUB™ 750PSV ventilator can be classified as a microprocessor controlled, time cycled, pressure limited, dual flow, neonatal/pediatric
critical care ventilator. Breaths are initiated either by the ventilator (controlled), by
patient activity (assisted), or by the operator (manual).
The top level block diagram (figure 2-1) graphically illustrates the overall structure of
the ventilator.
Figure 2-1: Top Level Block Diagram
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Figure 2-2: Pneumatics System Schematic
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Service Manual 25
Ventilator pneumatics - General description
Figure 2-2 shows the schematic diagram of the BEAR CUB™ 750PSV Pneumatics
System. The pneumatics interface to the electronics is achieved using various
actuators (solenoids) and transducers. The Pneumatics System consists of eight (8)
main subsystems: Gas Inlet and Conditioning, Oxygen Blender System, Flow
Control, Sub-Ambient/Overpressure Relief system, Exhalation Valve/Pressure
Control, Pressure Monitoring, the Proximal Airway Purge System, and the Auxiliary
Gas Outlet.
Gas Inlet Conditioning
Compressed air and oxygen sources, supplied in the pressure range of 30 to 80
psig, are connected to the standard DISS male-threaded fittings on the back panel of
the ventilator.
Incoming air passes through a coalescing filter housed in the Air Inlet Water Trap.
Particulate matter down to .3 micron in size, and aerosols down to .75 micron, are
trapped. Both gases, air and O2, pass through sintered metal filters.
Supply pressures are monitored and displayed by the ventilator via pressure
transducers and the system electronics. The system will trigger an alarm if either Air
or O
pressure drops below 24(±2) psig, and the alarm will reset when the pressures
2
are above 30 psig.
From the Air Inlet Water Trap and internal filters, the air and oxygen enter the in-line,
one way Check Valves which prevent flow from exiting through an inlet if that source
is removed.
Blender
Air and O2 pressure are regulated to 17 psig and are balanced to each other for
accurate blending of gases in the O
In the event of a failure of either of the supply gases, one of a pair of crossover
check valves will open to permit continued operation. Oxygen blending will not be
maintained in this condition, and the patient gas flow and pressure may decrease, by
less than 10%, depending on settings.
To ensure accurate oxygen blending at low patient flow rates, a bleed valve
maintains a minimum flow through the blender.
Flow Control Valve
blender.
2
Two flow control valves are switched by a solenoid valve to create Inspiratory and
Base Flow. Each valve controls flow from 1 to 30 L/min. Each flow control valve is
geared to a potentiometer. The potentiometer provides an electronic signal to the
microprocessor; this flow is then displayed on the front panel corrected to set
barometric pressure.
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26 Bear Cub 750PSV
NOTE
The Inspiratory Flow and Base Flow displayed on the Front Panel are independent of
the flow readings taken by the flow sensor.
AOPR Valve/Sub-Ambient Valve/ Dump Solenoid
Maximum pressure to the patient can be limited using the Adjustable/Over Pressure
Relief valve. The mechanical, user adjustable, pressure relieving valve can be set
from 15 cmH
breathe air through the Sub-Ambient valve.
A Dump Solenoid is activated upon detection of an obstruction in the expiratory leg
of the patient circuit. Activation of the solenoid opens the Dump Valve to the
atmosphere. The solenoid is controlled by software which monitors system
pressures. Depending upon flow rate, patient circuit pressure will drop to 5 cmH
or less.
O to 75 cmH2O. A patient effort of -3 cmH2O allows the patient to
2
O
2
Auxiliary Gas Outlet
The auxiliary gas outlet provides blended gas for use with a nebulizer, or for manual
ventilation. The connection of auxiliary gas is achieved via a DISS O
inhibit overpressure in the system due to a mistaken connection to high pressure
oxygen supply, a check valve in line allows only one direction of flow. Auxiliary gas
flow levels can range from 0 to 8 L/min. This flow will not be interrupted by a
disruption in electrical power (therefore, use of a manual resuscitation bag could be
initiated if needed).
Pressure Control System
The BEAR CUB™ 750PSV Infant Ventilator ventilates the patient between two
pressure levels: Positive End Expiratory Pressure (PEEP) and Peak Inspiratory
Pressure (PIP). Inspiratory Pressure must always be above the PEEP pressure for
ventilation to occur. The PIP pressure is manually set by the user at a level of 0 to
72 cmH
cmH
exhalation assist jet venturi compensates for flow resistance in the exhalation limb of
the patient circuit to allow 0 cmH2O PEEP setting at up to 10 L/min of Base Flow (to
less than 4 cmH
be set appropriately to prevent negative patient circuit pressures.
The patient circuit has a proximal airway line for monitoring patient pressure. This
proximal airway line provides a link to the control electronics and software. It also
functions as a pneumatic servo control line to the exhalation valve. Only tubing that
is 1/8 inch in diameter is to be used in the proximal airway system. Any other
diameter tube may cause patient circuit pressure to become less stable.
O (measured at the patient wye). The PEEP valve can be set from 0 to 30
2
O. A solenoid valve switches reference pressure to the Exhalation Valve. An
2
O at 20 L/min). At low levels of Base Flow, the PEEP control must
2
fitting. To
2
A purge flow (100ml/min) of blended gas through the proximal airway tube is used to
prevent the migration of moisture and patient contamination into the ventilator.
L2346 Revision B June 2004
Service Manual 27
Exhalation Valve
The Exhalation Valve regulates flow out of the patient circuit. Exhaled patient gases
flow through the expiratory leg of the patient circuit, past the Exhalation Valve
diaphragm and seat, and out to the atmosphere. The Exhalation Valve is a
pneumatic servo controlled regulator. Within the Exhalation Valve, Proximal pressure
and Control pressure (which alternates between PIP and PEEP reference pressure
depending on the breath phase) are separated by a Control diaphragm. If Control
pressure is higher than Proximal pressure, the Control diaphragm will move the
control pin to close the Exhalation Valve diaphragm. When Proximal pressure
equals PIP/PEEP Control pressure, the diaphragm will open slightly to maintain the
PIP/PEEP level. At exhalation, Control pressure drops to PEEP reference pressure
which causes the Control diaphragm to retract the control pin opening the Exhalation
Valve diaphragm. Proximal pressure then drops to the PEEP level and stabilizes.
Flow Sensor
The BEAR CUB™ 750PSV Infant Ventilator flow sensor reads gas flow while
sensing flow direction. The flow is calibrated to 37 °C, ambient pressure, and
assumes 100% humidity. Inhaled flows, exhaled flows, and volumes are monitored
with control electronics through the flow sensor. The flow sensor enables the
ventilator to trigger a breath based upon inspired flow. The patient effort (in L/min)
required to initiate a breath can be adjusted (.2 to 5 L/min) using the assist sensitivity
setting. The flow sensor also enables the ventilator to display on the front panel the
percentage of endotracheal tube leak based upon inhaled and exhaled volume
measurements.
The flow sensor operates on the principle of hot wire anemometry. The hot wire flow
sensing system is a constant temperature device. The bidirectional operation is
achieved with two platinum wires. The two wires are positioned in the same plane
with a pin installed between them. The upstream wire will cool more rapidly than the
downstream wire. Therefore more current will be required to maintain a constant
preset temperature. The electronics interprets this higher current in the upstream
wire to determine both flow and flow direction. This measured flow rate is then
integrated over time by the ventilator’s microprocessor to yield inhaled and exhaled
volumes.
The flow sensor reads from 0.2 to 40 L/min, calibrated from 0.2 to 25 L/min, and
indicates to 40 L/min. Each Flow Sensor Cable Assembly contains an electronic
memory circuit (an E2PROM) which stores calibration data for the unit. Therefore,
the sensor will function with the electronic circuit of any BEAR CUB™ 750PSV Infant
Ventilator without the need for a system calibration.
Ventilator Electronics
The major components of the electronics system include the Display PCB, the
Control PCB, and the Power Supply.
L2346 Revision B June 2004
28 Bear Cub 750PSV
The Display circuit board is the user interface for the ventilator electronics. Ventilator
controls and alarms are set by the clinician, and Monitors feed current ventilator
status back to the display.
The Control circuit board includes the Monitor MCU and Control MCU. The Control
board drives the system solenoids which control breath phase, flow, and pressure.
This is achieved using front-panel settings from the display board, as well as
incorporating its own real-time pressure and flow readings. The Control board also
enables bidirectional (digital) communication to the optional Graphic Display in order
to chart ventilator data. Also, analog outputs proportional to pressure and flow, plus
a breath phase signal are provided to the back panel. The electronics to drive and
read the flow sensor are also contained on the Control PCB.
Power Supply
The Power Supply converts the AC line voltage to DC voltages for the electrical
system. AC line voltages of 100, 120, 230, and 240 volts (at frequencies from 50 to
60 Hertz) can be used as input power. Five DC voltages are used in the ventilator
electronics: 5, 7, 10, -10 and 22 VDC. All power levels that are high enough to pose
an ignition hazard in the presence of oxygen concentrations greater than 21% are
housed in a separate enclosure from the rest of the system. If input power fails, a 12
volt rechargeable, sealed, lead-acid battery is included to provide a minimum of 30
minutes of ventilator operation. A two-level battery charger circuit is contained on
the Power Supply PCB in order to keep the battery on continuous charge whenever
the ventilator is plugged into an AC outlet.
Ventilator Software
The BEAR CUB™ 750PSV Infant Ventilator is a shared processor system,
incorporating two Motorola 68HC11 microcontroller units (MCU), the Monitor and the
Controller. Each processor, and thereby its software, have specific and duplicated
tasks. Each processor is based on a 2.5 m-sec timer interrupt, referred to as a ‘tick.’
The Controller directs basic control of the ventilator based on operational settings
communicated from the Monitor MCU, as well as on pressure transducer, and flow
sensor data read on its own 8 bit Analog to Digital (A/D) converter. The Monitor has
the following functions: (1) reads the front panel switches, back panel switches, and
potentiometers, (2) monitors ventilator performance as well as the performance of
the Controller MCU, (3) transmits front panel status to the Controller, (4) receives
performance data back from the Controller, and (5) transmits display data and
annunciator status to the front panel.
During power-up, both processors perform RAM (Random Access Memory), and
ROM (Read Only Memory) tests to verify integrity of these two memory systems.
Solenoid and Control Potentiometer continuity are also tested during power-up by
the Control and Monitor processors respectively. Continuous communication checks
between the two processors are used to verify functionality of each sub-system. If
an error is detected, either processor has the ability to shutdown the ventilator while
enabling the audible and visual Failed to Cycle alarms. These systems, among
others, are provided to reduce the possibility of a software/hardware error leading to
an undetected hazardous condition.
L2346 Revision B June 2004
Service Manual 29
Chapter 3 OVP Recommended Service
Operational Verification
Operational Verification should be performed between patient use or a minimum of
once each month. Verification may be done by a qualified operator, Allied Healthcare
Trained Hospital Service Technician or Allied Healthcare Technician. Verification is
intended to be done in the hospital. If done by an Allied Healthcare Technician,
there will be a charge.
Certain procedures such as a verification of the alarm circuits should be performed at
least once every 24 hours that the unit is in clinical use. Refer to the BEAR CUB™
750PSV Infant Ventilator instruction manual for details.
Do not use the ventilator unless it passes all the steps in the Operational Verification
Procedure.
Equipment Required
Infant Test Lung P/N 52000-40027
Patient Circuit P/N 50000-01147
Oxygen Analyzer
Rubber Stopper
Stop Watch
CAUTION
If any of the following procedures fail to producer the results as outlined in this
document, disconnect the ventilator and contact your authorized VIASYS Healthcare
service technician.
L2346 Revision B June 2004
30 Bear Cub 750PSV
Table 3-1: Standard Settings
Mode SIMV
Rate 30 BPM
Inspiratory Pressure 40 cmH2O
Inspiratory Flow 15 L/min
PEEP/CPAP 0 cmH2O
Inspiratory Time 0.8 seconds
Base Flow 5 L/min
Assist Sensitivity MAX
O2% 21%
Apnea 10 seconds
Low PEEP/CPAP Alarm -3 cmH2O
Volume Limit™ 300 ml
High Pressure Limit 50 cmH2O
Low Inspiratory Pressure Alarm 30 cmH2O
High Breath Rate Alarm 40 BPM
Table 3-2: Rate
Set Rate Inspiratory Time Using stop watch verify Breath Rate
10 BPM 3 seconds 10 ± 2 BPM
40 BPM 1 second 40 ± 3 BPM
80 BPM 0.4 seconds 80 ± 4 BPM
120 BPM 0.1 seconds 120 ± 6 BPM
Table 3-3: Exhalation Time and I/E Ratio Table
Rate Set Inspiratory time Verify Exhalation
Time
10 BPM 3.00 seconds 3.0 ± 0.4 sec 1:1.0 ± 0.3
75 BPM 0.40 seconds - - - - - - - - 1:1.0 ± 0.3
Verify I/E Ratio
150 BPM 0.10 seconds - - - - - - - - 1:3.0 ± 0.4
L2346 Revision B June 2004
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