Fisher & Paykel MR850 User Manual 2

MR850 RESPIRATORY

HUMIDIFIER

Technical Manual

REVISION J

Copyright ©2005 Fisher & Paykel Healthcare Ltd.

Auckland, New Zealand

Fisher & Paykel Healthcare Head
Office:

PO Box 14-348, Panmure,
Auckland 1134
New Zealand
Email: [e-mail]
Web Site: www.fphcare.com

France/Benelux:

Parc Silic-Bal F,
10 Avenue de Quebec,
Silic 512 Villebon, 91946,
Courtaboeuf, Cedex, France.
Tel: [phone]

Fax: [phone]
Tel: [phone]
Fax: [phone]

Australia:
36-40 New Street,
Ringwood, Victoria 3134,
Australia,
Tel: [phone]
Fax: [phone]

USA:

Suite 101 22982 Alcalde Drive,

Laguna Hills, California 92653, USA

Tel: [phone]

Fax: [phone]

Toll Free: (800)-446-3908

Germany:
Hundsbergerstrasse 45
73642 Welzheim
Germany
Tel: [phone]
Fax: [phone]

UK and Ireland(European Authorised Representative):

Unit 16, Cordwallis Park

Clivemont Road, Maidenhead, SL6 7BU,

United Kingdom

Tel: [phone]

Fax: [phone]

2

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

TABLE OF CONTENTS

1 INTRODUCTION .................................................................................................................................7

1.1 ABOUT THIS MANUAL..............................................................................................................................7

1.2 GLOSSARY ............................................................................................................................................7

1.3 DEFINITIONS ..........................................................................................................................................8

1.4 PRODUCT APPLICATION..........................................................................................................................8

2 HUMIDIFIER SYMBOLS.....................................................................................................................9

3 SPECIFICATIONS.............................................................................................................................10

3.1 MECHANICAL .......................................................................................................................................10

3.2 ELECTRICAL.........................................................................................................................................10

3.3 TEMPERATURE RANGE .........................................................................................................................10

3.3.1 Heater Wire Mode..................................................................................................................10

3.3.2 Non Heater Wire Mode..........................................................................................................10

3.3.3 Alarm Parameters..................................................................................................................10

3.4 PERFORMANCE....................................................................................................................................11

3.5 TRANSPORT AND STORAGE ENVIRONMENTAL CONDITIONS ....................................................................11

3.6 STANDARDS AND APPROVALS...............................................................................................................11

4 OPERATING MODES AND CONTROLS.........................................................................................12

4.1 HUMIDIFIER OPERATION .......................................................................................................................12

4.1.1 Heater wire operation ............................................................................................................12

4.1.2 Non-Heater Wire Operation...................................................................................................13

4.1.3 Stand-by Operation................................................................................................................13

4.1.4 Power Up Sequence..............................................................................................................14

4.1.5 Humidity Compensation (HC) mode......................................................................................14

4.1.6 Breathing Circuit Recognition ................................................................................................15

4.2 HUMIDIFIER CONTROLS ........................................................................................................................16

4.2.1 Power Button .........................................................................................................................16

4.2.2 Mode Button ..........................................................................................................................16

4.2.3 Mute Button ...........................................................................................................................17

4.3 TEMPERATURE DISPLAY .......................................................................................................................17

4.3.1 Showing Chamber and Airway Temperature ........................................................................17

4.4 SETUP INDICATORS..............................................................................................................................17

4.4.1 Heater wire connector ...........................................................................................................17

4.4.2 Temperature / Flow Probe Connector ...................................................................................18

4.4.3 Chamber Probe & Airway Probe ...........................................................................................18

4.4.4 Chamber or Airway Probe Alarm with Probe connector alarm..............................................18

4.4.5 Water Out Indicator................................................................................................................19

4.5 OPERATIONAL ALARMS.........................................................................................................................19

4.5.1 Temperature Indicator ...........................................................................................................19

4.5.2 Non-Heater Wire Operation...................................................................................................20

4.5.3 See Manual Indicator.............................................................................................................20

5 MAINTENANCE PROCEDURES......................................................................................................21

5.1 MAINTENANCE SCHEDULE ....................................................................................................................21

5.1.1 MR850 Humidifier ..................................................................................................................21

5.1.2 MR850 Temperature Probe...................................................................................................21

5.2 SAFETY CHECK....................................................................................................................................22

5.3 CLEANING INSTRUCTIONS .....................................................................................................................23

5.3.1 MR850 Humidifiers ................................................................................................................23

5.3.2 Temperature Flow Probe.......................................................................................................23

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

3

TROUBLESHOOTING ..................................................................................................................... 24

6

6.1 OPERATIONAL PROBLEMS.................................................................................................................... 24

6.2 TECHNICAL PROBLEMS ........................................................................................................................ 26

6.3 “SEE MANUAL” ERROR CODES............................................................................................................. 27

6.4 DIAGNOSTIC MENU .............................................................................................................................. 29

6.4.1 Diagnostic Menu for Software Versions 5.45, 5.70............................................................... 29

6.4.2 Diagnostic Menu for Software Version 6.00 ......................................................................... 30

6.4.3 Diagnostic Menu for Software Version 7.00 & 7.21 .............................................................. 31

6.4.4 Diagnostic Menu for Software Version 7.14 & 7.22 .............................................................. 32

6.4.5 Diagnostic Menu for Software Version 7.23 ......................................................................... 34

7 SERVICING PROCEDURES............................................................................................................35

7.1 GENERAL CONSIDERATIONS ................................................................................................................ 35

7.2 DISASSEMBLY ..................................................................................................................................... 35

7.2.1 Opening the case.................................................................................................................. 35

7.2.2 Replacing Fuses ................................................................................................................... 36

7.2.3 Replacement of Printed Circuit Boards (PCBs) .................................................................... 37

7.2.4 Replacement of Transformer ................................................................................................38

7.2.5 Servicing the Heater Plate .................................................................................................... 38

7.2.6 Installing New Software.........................................................................................................42

7.2.7 Replacing the Mains Cable ................................................................................................... 43

7.2.8 Closing the case.................................................................................................................... 43

8 PERFORMANCE TESTING .............................................................................................................44

8.1 HUMIDIFIER PERFORMANCE TESTING ................................................................................................... 44

8.1.1 Entering the Service Menu.................................................................................................... 44

8.1.2 Humidifier Calibration Check ................................................................................................ 44

8.1.3 Humidifier Display Test .........................................................................................................45

8.1.4 Humidifier Voltage Calibration Check ................................................................................... 46

8.1.5 Humidifier Warm-up and Control Check ............................................................................... 46

8.2 PROBE ACCURACY CHECK................................................................................................................... 47

8.2.1 Probe Temperature Accuracy Test....................................................................................... 47

8.2.2 Probe Flow Accuracy Test .................................................................................................... 47

9 RECOMMENDED MAINTENANCE CHECKLIST............................................................................ 49

9.1 HUMIDIFIER CHECK (ANNUALLY) .......................................................................................................... 49

9.2 PROBE CHECK (EVERY SIX MONTHS).................................................................................................... 49

10 SPARE PARTS................................................................................................................................. 51

11 CALIBRATION PROBE ................................................................................................................... 55

12 SERIAL PORT & LOGGING SOFTWARE ...................................................................................... 56

12.1 INTRODUCTION............................................................................................................................... 56

12.2 INSTALLATION................................................................................................................................. 56

12.3 OPERATING INSTRUCTIONS ......................................................................................................... 56

12.3.1 Viewing Humidifier Data........................................................................................................ 56

12.3.2 Logging Humidifier Data to File............................................................................................. 57

13 EMC INFORMATION........................................................................................................................ 58

14 PRODUCT CHANGE HISTORY....................................................................................................... 60

4

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

Revision Description of Technical Manual Change Date Issued

A

B

C

D

E

F

G

H

First release technical manual.
Covers Revision A PCB’s ONLY.

Second release technical manual.
Covers Revision C and later PCB’s ONLY.

Add “View850” Software Instructions

Neonatal volume ventilation capability.

3.4 Performance

4.1.2 Power Up sequence.

4.1.3 Manual Temperature Compensation (TC).

5.3 Cleaning Instructions

Appendix E – Product Change History.

Covers release of software version 6.00.

3.4 Performance
Recommended Operating Temperature: 15 to 26ºC

4.1.1 Stand-by.
Changed stand-by power limits.

4.1.3 Humidity Compensation (HC) mode.
Auto HC mode option.

4.2 Humidifier Controls
Power button must be held for 1 second to switch OFF.

4.4 Setup Indicators
Two LED’s now indicate heater wire connect alarm.

4.5 Operational Alarms
Low temperature alarm enabled during stand-by.

6.4 Diagnostic Menu
“OFF” Offset removed from diagnostic menu.

Covers release of software version 7.00.

3.4 Performance

Recommended Operating Temperature: 18 to 26ºC

4.1.3 Humidity Compensation (HC) mode

Changed step size to 1 °C in non-invasive mode

4.1.4 Breathing Circuit Recognition added

6.3 See – Manual, Error Codes

removed redundant error code “E33”

6.4 Diagnostic Menu

add new functions “CHP” and “Cct”

Technical manual now covers software versions 5.45, 5.70, 6.00, 7.00
and 7.14

The following sections have been modified: 3.3, 4.1.3, 4.1.5, 4.4, 5.3,

6.4, 7.2.3, 7.2.6, Appendix E

Added Non-Heater Wire Mode in sections 3.0, 4.0, 6.0, and updated
Product Change History

I

8.1.2 Humidifier Calibration Check – Equipment Required
Removed the reference to the service kit
10 Spare Parts
Added parts 17 to 22.

12.1 Introduction
Updated how to get View850 and the serial cable

12.2 Installation
Changed View850 installation from floppy disk to CD

12.3.1 Viewing Humidifier Data

Updated how to run View850 and how to change the com. Port

Add section, 13. EMC Information

12 Jan. 1999

6 May 1999

1 Mar. 2000

15 May 2001

1 November 2001

2 April 2002

1 May 2003

1 July 2004

1 August 2005

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

5

Revision Description of Technical Manual Change Date Issued

J

Note:

1. Fisher & Paykel Healthcare have a policy of continued product improvement and reserve the right to change

specifications without notice.

2. This Technical Manual covers software version 5.45, 5.70, 6.00, 7.00, 7.14, 7.21, 7.22, 7.23 and PCB Revision

C, D and E. Refer to previous revisions of the Technical Manual for earlier software and PCB versions.

1.4 Product Application, Add warning to connect humidifier only to a
pure sine wave power source

5.2 Safety Check, add CAUTION: and NOTE:

6.3 “See manual” Error codes, Elaborate the fault description

8.1.5 Humidifier Warm-up and Control Check, Change test flow rate
from 20±10 SLPM to 10±5 SLPM. Reference test limits to airway and
chamber set temperatures rather than fixed values.

8.2.2 Probe Flow Accuracy Test, Change test flow rate from 20±2
SLPM to 10±1 SLPM. Check flow measurement is now between 5 and
15 LPM

10 Spare Parts, add items 23,24,25,26

1 November 2005

6

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

Introduction

1.1 About this Manual

This manual is intended for qualified service personnel who will perform maintenance and
servicing on the Fisher & Paykel Healthcare MR850 Respiratory Humidifier. This manual
covers the product specifications, includes a maintenance schedule, and provides the
necessary information required for servicing.

NOTE: Some software may not be available in your country. Refer to your local Fisher &
Paykel Healthcare representative for the appropriate software version. Maintenance
procedures should be carried out at regular intervals (as recommended in the maintenance
schedule), to ensure that the humidifier and its accessories are working correctly.

If a fault should occur with the humidifier, follow the troubleshooting guide (section 6) in order to
find the most likely cause. If the unit requires servicing, make sure the servicing procedures are
followed in order to prevent damage to the humidifier. After service, or as part of the
maintenance schedule, a humidifier performance check should be completed.

Due to the nature of the electronics contained within this humidifier, it is not recommended that
the printed circuit boards be serviced at component level. Instead, if the PCBs are found to be
malfunctioning, they should be replaced.

1.2 Glossary

Chamber

Temperature / Flow
Probe

Airway Probe

Chamber Probe

Thermistor

Chamber Set Point

Airway Set Point

Heater Wire Adaptor

Breathing Circuit

Device that allows gas to be to be heated and humidified by passing it
over heated water.

Sensor assembly for measuring temperature and flow of respiratory
gases traveling through the breathing circuit. Consists of a chamber
and airway probe.

Sensor assembly for measuring gas temperature at the end of the
inspiratory limb.

Sensor assembly for measuring gas flow and temperature at the
outlet of the humidification chamber.

A temperature sensitive resistor placed inside the chamber and
airway probes.

The temperature that the humidifier attempts to maintain at the
chamber probe port.

The temperature that the humidifier attempts to maintain at the airway
probe port.

Electrical connector between the breathing circuit and the humidifier.

Tubing that carries respiratory gases to and from the patient.

Dual Heated Breathing
Circuit

Single Heated
Breathing Circuit

PCB

Heater Wire

Inspiratory Limb

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

A breathing circuit that is heated by means of heater wires, in both the
expiratory and inspiratory limbs.

A breathing circuit that is heated by means of a heater wire, in only
the inspiratory limb.

Printed Circuit Board.

Wire inside the breathing circuit which heats the respiratory gases.

The section of the breathing circuit that takes the inspired gases to
the patient.

7

Expiratory Limb

The section of the breathing circuit that takes the expired gases from
the patient.

1.3 Definitions

NOTE: A NOTE provides important information or explanation of procedures or conditions which
may otherwise be misinterpreted or overlooked.

CAUTION:

A CAUTION statement designates the possibility of damage to this or other

equipment if a procedure is not followed exactly.

WARNING:
A WARNING statement refers to conditions with a possibility of personal injury if a
procedure is not followed exactly.

1.4 Product Application

The MR850 is a respiratory humidifier designed for use in hospital intensive care units. It is
used to provide optimum humidity to respiratory gases delivered to patients via endotracheal
tubes or face masks.

Refer to the Respiratory Humidification Product Catalogue or your local Fisher & Paykel
Healthcare representative for a list of approved accessories.

WARNING:

• The use of breathing circuits, chambers or other accessories which are not approved

by Fisher & Paykel Healthcare may impair performance or compromise safety.

• Ensure that Invasive mode is set for patients that have bypassed airways.

• Ensure maintenance of grounding integrity by connection to a "hospital grade"

receptacle.

• Always disconnect supply before servicing.

• When mounting a humidifier adjacent to a patient ensure that the humidifier is always

securely mounted and positioned lower than the patient.

• The operation of high frequency surgical apparatus, shortwave or microwave

equipment in the vicinity of the humidifier may adversely affect its function. If this
occurs, the humidifier should be removed from the vicinity of such devices.

• Ensure that both temperature probe sensors are correctly and securely fitted. Failure

to do so may result in gas temperatures in excess of 41 °C being delivered to the
patient.

• Do not touch the glass tip of the chamber temperature probe during use. Keep black

connectors dry at all times.

• Visually inspect accessories for damage before use.

• Normal operation can not be guaranteed if powered from a source other than a pure

sine wave, such as a square wave inverter.

8

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

2 Humidifier Symbols

Year-month

Caution: Hot surfaces may
exceed 85 °C

Type BF

Attention – consult
accompanying documents

Alternating Current

Power On/Off (stand by)

Invasive Mode

Non-invasive mode

Temperature Alarm

Drip proof protection to IPX1

Date of manufacture

C-tick for EMC

Serial Port

Protective Earth

Caution: Electrostatic
Sensitive Device

Do not discard

WEEE collection (EU only)

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

9

3 Specifications

3.1 Mechanical

Dimensions: 140 mm x 173 x 135 (without chamber fitted)
Weight: 2.8 kg (without chamber fitted)

Approx. 3.1 kg (with chamber fitted, and filled with water)

3.2 Electrical

MR850 Model Number Supply Voltage Supply Current

MR850Axx
MR850Pxx
MR850Jxx
MR850Gxx

Supply Frequency: 50 or 60 Hz, Sine Wave
Heater Plate Capacity 150 W at nominal mains voltage
HP Thermal Cutout: 118 ± 6 °C
Heater Wire Supply: 22 ± 5 V~, 2.73 A Max, 50 or 60 Hz
Maximum Heater Wire Load: 8.0 Ω.

230 V~
127 V~
115 V~
100 V~

1.0 A Max

1.8 A Max

2.0 A Max

2.4 A Max

3.3 Temperature Range

3.3.1 Heater Wire Mode

Invasive Mode: Chamber Set Point: 35.5 to 37 °C

Chamber Set Point: 35.5 to 40 °C (versions 5.33, 5.34, 5.45, 5.70,

6.00, 7.00, 7.21).
Chamber Set Point: 35.5 to 42 °C (versions 7.14, 7.17 & 7.22).
Airway Set Point: 35 to 40 °C

Non-Invasive Mode: Chamber Set Point: 31 °C

Chamber Set Point: 31 to 34 °C (versions 5.33, 5.34, 5.45, 5.70,

6.00).
Chamber Set Point: 31 to 36 °C (versions 7.00, 7.14, 7.17, 7.21,

7.22).
Airway Set Point: 28 to 34 °C

3.3.2 Non Heater Wire Mode

Invasive Mode: Airway Set point: 37 °C (chamber temperature limited to 66 °C)
Non-invasive Mode: Airway Set point: 31 °C (chamber temperature limited to 66 °C)
Display: Three digit, 14 mm, 7 segment LED

Range: 10 to 70 °C

Accuracy: ± 0.3 °C (in 25 to 45 °C temperature range)

3.3.3 Alarm Parameters

High Temperature Alarm: Causes an immediate, audible and visible alarm at a displayed

temperature of 41 °C or if the airway temperature exceeds 43 °C
(see section 4.3)

Temperature Alarm: Invasive Mode

After 10 minutes @ 29.5 °C causes an audible and visible alarm.
After 60 minutes @ 34.5 °C causes an audible and visible alarm
(see section 4.5)
NOTE: The temperature indicator lights if the displayed
temperature drops below 35.4 °C, initially providing a temperature
warning.

10

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

:

Non-heater wire operation:
Invasive Mode: Airway temperature < 29.5 °C causes an audible
and visible alarm.
Non-invasive Mode: Airway temperature < 26.0 °C causes an
audible and visible alarm.

Sound Pressure Level: Alarms exceed 50 dBA @ 1 m.

3.4 Performance

Invasive Mode: Flow up to 60 LPM, humidity output >33 mg/L
Non-Invasive Mode: Flow up to 120 LPM, humidity output >10 mg/L
NOTE: Performance results with RT100 breathing circuit
Maximum System
Operating Pressure:
Warm-up time: Less than 30 minutes.
Recommended ambient

temperature range:

20 kPa, gas leakage at max. pressure <100 mL/minute.

18 to 26 °C

CAUTION:

If operating outside the recommended ambient temperature range, consult your

local Fisher & Paykel Healthcare representative or refer section 4.1.5.

3.5 Transport and Storage Environmental Conditions

Transport Conditions: -10 to +50 °C
Storage Conditions: -10 to +50 °C

3.6 Standards and Approvals

AS/NZS 3200.1.0, CAN/CSA 22.2 No.601.1, UL 60601-1, IEC 60601-1, EN 60601-1

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

11

4 Operating Modes and Controls

4.1 Humidifier Operation

The MR850 humidifier is designed to add heat and moisture to respiratory gases. The gas is
passed through a humidification chamber where it is warmed and humidified.

The MR850 has two heating systems. The first is a heater plate, which heats the water
contained in the humidification chamber, humidifying the air passing through it. The humidifier
monitors the temperature of the gas at the chamber outlet with the chamber probe, and controls
the amount of power delivered to the heater plate, in order to maintain the chamber set point.
Under normal conditions the gas is heated to 37 °C in the invasive mode, 31 °C for the non­invasive mode.

4.1.1 Heater wire operation

Ventilator/Gas Supply

RT100 Breathing Circuit

Temperature Probe

Chamber Probe

MR290 Chamber

MR850 Humidifier

Heater Wire Adapter

Figure 4.1 Typical Heater Wire Humidifier Setup

Airway Probe

Humidified gas from the chamber travels through the inspiratory limb, where its temperature
must be maintained in order to prevent the generated humidity from condensing. This is
achieved with a heater wire encapsulated within the inspiratory limb. The humidifier maintains
the temperature along the inspiratory limb by monitoring the temperature at the airway probe
and controlling the power delivered to the heater wire. Under normal conditions the gas is
heated to 40 °C in the invasive mode, 34 °C for the non-invasive mode.

An optional, second heater wire, located in the expiratory limb, minimises condensate in this
limb.

12

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

4.1.2 Non-Heater Wire Operation (Software version 7.23 only)

Ventilator/Gas Supply

RT134 Breathing Circuit

Temperature Probe

Chamber
Probe

MR290
Chamber

Water trap

Airway Probe

MR850 Humidifier

Figure 4.2 Typical Non-Heater Wire Humidifier Setup

In this application the MR850 maintains the airway temperature at the desired set point
(invasive 37 °C or non-invasive 31 °C) by heating the chamber of water through the heater
plate. As the gas cools considerably down the unheated circuit, a water trap circuit must be
used to collect the resulting condensate.

Activating Non-Heater Wire Operation

Refer also to the diagnostic menu in section 6.4.

1 Turn on the humidifier with NO heated circuit connected, and mute the heater wire alarm.

2 Access the diagnostic menu by pressing the mute and mode buttons together for 1 second,

the display should show two rows of dashes ‘= = =’. Releasing both buttons will allow the
diagnostic menu to cycle automatically.

3 Allow the menu to cycle through to “cct” – the circuit identification. Press mute to access

this function.

4 To enable non-heated operation, press both mute and mode buttons simultaneously for 1

second, the humidifier will beep twice and the temperature display will show “nhh”.
Release both buttons. The humidifier is now configured for non-heated circuits. This
setting will be remembered each time the humidifier is turned on.

Deactivating Non-Heater Wire Operation

The simplest way to de-activate non heater wire operation is to connect a heated breathing
circuit. Alternatively it can be de-activated the same way that non-heated circuit operation was
activated (see above).

4.1.3 Stand-by Operation

If the humidifier detects a problem with its setup or operation it will alarm. Depending on the
severity of the alarm condition, the humidifier will either remove all power from the heating
systems, or enter stand-by. The humidifier will also enter stand-by if the gas flow through the
breathing circuit has stopped.

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

13

Stand-by (Software versions: 5.45 & 5.70)

• Heater wire power is set at 30 %.

• Control of chamber temperature is attempted, within the following limits:

• Heater plate temperature is limited to 60 °C.

• Heater plate power is limited to 20 %.

Stand-by (Software version: 6.00 onward)

• Heater wire power is set at 15 %.

• Control of chamber temperature is attempted, within the following limits:

• Heater plate temperature is limited to 50 °C.

• Heater plate power is limited to 20 %.

NOTE: The temperature alarm algorithm continues to function in stand-by.

4.1.4 Power Up Sequence

The purpose of the power up sequence is to perform internal checks on various parts of the
humidifier and provide the user with a visual and audible check.

Internal self test sequence:

1. Test presence of heater wire.

2. Test correct operation of heater wire triac.

3. Test correct operation of protection relays.

4. Test integrity of temperature/flow probe.

Visual/Audio test sequence:

1. The temperature display and indicator LEDs turn on.

2. The temperature display is blanked and indicators set to their default.

3. Display shows humidifier model number i.e. 850.

4. Display is blanked.

5. Display shows software version number.

6. Display is blanked and an audio tone of 2100 Hz sounds.

7. Normal display.

4.1.5 Humidity Compensation (HC) mode (Software version 6.00 onward, except 7.23)

Normal ambient environments between 18 °C and 26 °C do not affect humidity output of
temperature controlled heated humidifiers. However once the ambient temperature increases
above 26 °C, and/or the temperature of the incoming gas becomes greater than 32 °C, e.g. due
to ventilator heating, then the humidity output maybe reduced.

This can be identified by the lack of beading condensate on the inner walls of the humidification
chamber and rectified by modifying the breathing circuit or humidifier settings. Increasing the
length of breathing circuit between the ventilator and the humidification chamber will assist in
cooling the gas before it enters the chamber and improve humidity output.

If beading condensate does not form, humidity output can be further improved by increasing the
humidifier’s chamber set point. This can be achieved by accessing the HC mode (or Tc) in the
Diagnostic Menu (see section 6.4) and either manually selecting a level of chamber temperature
compensation or letting the automatic mode do it for you.

Automatic Humidity Compensation

When automatic HC mode is selected the humidifier calculates the power required to
adequately humidify the gas flow through the chamber. If the minimum power level is not met

14

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

then the chamber set point will automatically be increased in 0.5 °C steps (1 °C steps for non­invasive mode) until the minimum power is achieved. The maximum amount of compensation
applied is either 3 or 5 °C depending on the mode and software version (section 6.4 Diagnostic
Menu details how compensation is applied for each software version).

If conditions improve and too much power is being applied, then the MR850 will automatically
reduce the chamber set temperature.

NOTE: Excessive condensate may form in the breathing circuit if the auto HC function is used
with turbine driven ventilators (i.e. ventilators that use room air). It is recommended to switch off
the auto HC function in these situations if the condensate becomes excessive.

NOTE: Auto HC function is factory set to enabled on all MR850 models.

Manual Humidity Compensation

For manual HC the level of compensation should be increased until beading condensate is
observed on the inner walls of the humidification chamber. It should be noted that if
environmental conditions change then it might be necessary to re-adjust this setting. For
example, a fall in room temperature could produce a build up of unwanted condensate in the
delivery circuit. A reduction in this setting may stop further build up.

NOTE: The previous manual HC setting is restored when power is applied to the humidifier

Refer to section 6.4 Diagnostic Menu for further information regarding this feature.

Activating/Deactivating Humidity Compensation

Refer also to the diagnostic menu in section 6.4

1. Access the diagnostic menu by pressing the mute and mode buttons together for 1
second, the diagnostic menu is entered, indicated by the display of two rows of dashes
‘= = =’. Releasing both buttons will allow the diagnostic menu to cycle automatically
through the menu.

2. The first item is “HC” this is the humidity compensation item, press and hold mute to
access this function.

3. The setting may show either ‘0’ or ‘-A-‘ to change the setting press both mute and mode
buttons simultaneously for 1 second, the humidifier will beep twice and the setting will
increase. Release both buttons.

4. To increase again repeat step 3. To decrease the setting press the mute and power
buttons for 1 second.

5. To exit the menu, release all buttons, the menu will continue to cycle until ‘end’ is
displayed, the menu will automatically exit.

Temperature Display

To alert users during normal operation that either manual or automatic HC mode has been
enabled, the decimal point on the temperature display will flash. Each of the two modes can be
further identified by the flash rate, where auto HC mode has a slower flash rate than manual HC
mode.

Note: The displayed temperature may also be higher than normal indicating (up to 39°C) the
amount of compensation present.

4.1.6 Breathing Circuit Recognition (Software version 7.00 onward)

Fisher & Paykel Healthcare has developed a range of breathing circuits that offer optimum
performance for the type of treatment selected while working within recommended operating
conditions. Some of these breathing circuits require a slightly modified controller to optimize
performance. To do this the MR850 must first recognize what type of delivery circuit has been

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

15

connected. Breathing circuit recognition is performed via three electrical connections on the
heater wire adaptor. Re-configuring the electrical connection pins on a heated circuit and the
way it connects to this adaptor identifies the type of heated circuit. In this way three separate
heater wire circuits can be identified by the MR850.

4.2 Humidifier Controls

4.2.1 Power Button

The humidifier will power on if this button is held down briefly, but must be held
for one second to turn the humidifier off.

Note: For software version 5.45, 5.70 the power button need only be pressed
briefly to turn off the MR850.

CAUTION:

energized. Be sure to disconnect power from the MR850 before servicing.

After power-on the humidifier starts an internal diagnostic routine which checks
for possible problems in the humidifier setup. If everything is working correctly,
normal control is initiated.

4.2.2 Mode Button

When held down for one second, the mode button toggles the humidifier
between Non-Invasive and Invasive mode. The Mode indicator LED shows the
user which mode is selected.

Invasive mode is for use with patients whose upper airways have been
bypassed by either a tracheostomy or endotracheal tube. In this mode of
operation the humidifier attempts to deliver optimal humidity to the patient (37
°C, 100 % RH). This mode is the default mode on power up of the humidifier.

The humidifier normally controls the chamber outlet temperature to 37 °C, and
the airway temperature to 40 °C, maintaining a +3 °C temperature gradient
along the inspiratory limb

If however this temperature gradient is not maintained, the chamber set point is
reduced in 0.5 °C steps (minimum setting of 35.5 °C), in order to reduce
condensate buildup in the breathing circuit
than 37 °C and sufficient temperature gradient has been maintained along the
inspiratory limb, then the chamber set point is increased back up to 37 °C in 0.5
°C steps.

Although the display is not illuminated, the unit may still be

1

.

2

. If the chamber set point is less

Non-Invasive mode is suitable only for patients whose natural humidification
system (i.e. upper airways) has not been bypassed, but are receiving gas via a
facemask or similar.

The humidifier normally controls the chamber outlet temperature to 31 °C, and
the airway temperature to 34 °C, maintaining a +3 °C temperature gradient
along the inspiratory limb

1

If automatic or manual humidity compensation has been activated then the displayed temperature may be higher

than 37 °C (Invasive mode) or 31 °C (Non-Invasive mode).

2

The humidity compensation algorithm takes precedence over the condensation control algorithm.

16

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

1

.

4.2.3 Mute Button

The mute button silences the humidifier's audible alarm. The muted time
depends on the alarm condition. In general, alarms will be muted for 2 minutes.

A chamber or airway probe alarm is muted for a longer time, until the humidifier
determines whether the probe is in or out. The temperature alarm is treated
differently - see section 4.5.

4.3 Temperature Display

The front panel shows the lower of the chamber or airway temperatures. This temperature
gives an indication of the dew point (in °C) of the gas that is being supplied to the patient. The
dew point of a gas is the best indication of both its humidity and energy content. Under normal
operation, the displayed temperature will be the chamber temperature, as its control set point is
lower. If the temperature is above 70 °C, "Hi" will be displayed. If the temperature is below 10
°C, "Lo" will be displayed. If HC mode has been enabled the decimal point on the temperature
display will flash.

4.3.1 Showing Chamber and Airway Temperature

Both the chamber and airway temperature can be displayed by pushing and holding the mute
button for 1 second. The temperatures are displayed in the following sequence:

1 Chamber temperature is displayed until two seconds after the mute button is released. The

chamber probe indicator (see section 4.4) will also light to show which temperature is being
displayed.

2 The display will blank, and then the airway temperature will be displayed until two seconds

after the mute button is released. The airway probe indicator will also light (see section 4.4)
to show which temperature is being displayed.

3 The temperature display will blank again, and revert to normal operation.

4.4 Setup Indicators

The MR850 setup indicators, placed on the lower left of the front panel, are intended to aid the
user in identifying problems with the incorrect setup of the device and its accessories.

4.4.1 Heater wire connector

These indicators light if the heater wire in the breathing circuit has not been
connected correctly, or if the heater wire or heater wire adaptor is faulty. An
intermittent connection, or excessive current (total current in all limbs > 3.5 A) in
the heater wires will also produce this alarm. The humidifier will remove power
from the heating systems if this alarm is active.

NOTE: Software versions 5.45 and 5.70 do not light the upper indicator located
on the breathing circuit.

NOTE: Software versions 7.22 and 7.23 in non heater wire operation and
without a heater wire connected no audible or visual heater wire alarm will be
given. Connecting a heated wire circuit will automatically cause the MR850 to
default to heater wire operation.

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

17

4.4.2 Temperature / Flow Probe Connector

This indicator will light if the temperature probe is not correctly plugged in, or the
probe used is faulty. The humidifier tests for the following probe fault conditions:

• Temperature probe disconnected

• Chamber thermistor open or short circuit

• Airway thermistor open or short circuit

• Flow thermistor open or short circuit (shorted probe test)

• One thermistor shorted to another (shorted probe test)

• Flow calibration resistor open or short circuit (shorted probe test)

An alarm will be generated if any of the above faults are found, and the
humidifier will remove power from all heating systems.

NOTE: the shorted probe tests and flow thermistor tests are only performed on
start-up, or when temperature probe or heater wire alarms are cancelled.

4.4.3 Chamber Probe & Airway Probe

These indicators are used to show that either the chamber probe or airway
probe is not inserted into the breathing circuit correctly. On start-up, and during
rapid changes in temperature, the humidifier tests to see if a probe is in place by
cooling and then heating the probe. If the humidifier finds that either probe is
not inserted into the breathing circuit, an alarm will be generated and the
humidifier will enter stand-by. During this alarm the humidifier will initiate a
probe out test periodically, or a test will be initiated immediately after mute has
been pressed.

During periods of low or zero gas flow, the airway probe out alarm is disabled.
As soon as flow is detected however, an airway probe test is initiated.

NOTE: For software versions 7.22 and 7.23 in non-heater wire operation, the
airway probe out alarm does not function, instead the low temperature of the
disconnected probe will activate the temperature alarm (refer section 4.5).

4.4.4 Chamber or Airway Probe Alarm with Probe connector alarm

The humidifier checks to see if the temperature probe is faulty by testing for the
following conditions:

• Chamber temperature has been greater than 50 °C for 20 minutes

• Chamber temperature is greater than 80 °C

• Airway temperature has been greater than 50 °C for 5 minutes

• Airway temperature is greater than 80 °C

If an apparent fault is found, the humidifier will give a temperature / flow probe
connector alarm, and also indicate either the chamber or airway probe. The
humidifier will stay in stand-by until the chamber or airway temperature drops
below 50 °C. Once this occurs, a probe test will also be initiated.

18

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

4.4.5 Water Out Indicator

This indicates that there is insufficient water in the humidification chamber.

The humidifier measures the amount of power used to obtain the chamber
temperature. If a lower than expected amount of power is used, a 'water out'
alarm is generated. It may take 15 minutes or longer to generate an alarm
especially if there is a disturbance (change in flow).

This alarm can be cancelled by pressing the mute button. If however the water
out condition remains, the humidifier will alarm again.

4.5 Operational Alarms

These alarms are generated if problems occur with the operation of the humidifier.

4.5.1 Temperature Indicator

This alarm will occur if the displayed temperature is too high, or if the delivered
temperature (Invasive mode only) has been low for a period of time.

High temperature:

The humidifier will immediately alarm if at any time the displayed temperature
exceeds 41 °C, or if the airway temperature exceeds 43 °C. If either of these
high temperature alarms occur, the humidifier will immediately shut down the
heater wire and heater plate.

Low Temperature:

The low temperature warning (visual only) and alarm (visual and audible) are
active only when the humidifier is in Invasive mode. Both are disabled during
warm-up conditions. The warning alerts the user that low temperature is being
delivered to the patient. The alarm alerts the user that a low level has been
delivered to an Invasive patient for too long.

The low temperature warning and alarm operate by monitoring the displayed
temperature. If the displayed temperature is below 35.5 °C for 25 seconds, the
temperature indicator will light, and act as a warning to the user. If the
temperature remains below this level for too long, then a Temperature Alarm is
activated. The time taken for the humidifier to alarm is dependent on how far
below the 35.5 °C threshold the displayed temperature is. Figure 4.3 shows the
relationship between temperature, a temperature warning and the time before a
temperature alarm:

MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)

19