Drager Gamma, Gamma XL User manual

Technical Service Manual

Gamma / Gamma XL Patient Monitors

Monitor System

Revision 0 6013.053 MS14879

Emergency Care • OR/ Anesthesia • Critical Care • Perinatal Care • Home Care

Because you care

Copyright by Dräger Medical AG & Co. KGaA, Lübeck, Germany.

No reproduction allowed for commercial purposes.

Read and understand the Instructions for Use/Operator’s Manual.

This Technical Documentation does not replace the Instructions for Use/Operator’s Manual.

The warranty and liability conditions of the general terms and conditions for business transactions of Dräger Medical AG & Co. KGaA are not extended by this Technical Documentation.

Observe all applicable technical laws and regulations.

Insofar as reference is made to laws, regulations or standards, these are based on the legal system of the Federal Republic of Germany. Observe the laws and regulations applicable in your country.

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Contents

General

1	Advisory		3
2	Important information		3
	2.1	Symbols and Definitions .........................................................................................................	3
3	Introduction		4
	3.1	Service Strategy .....................................................................................................................	4
4	Product Overview		5
	4.1	Monitored Patient Parameters ................................................................................................	5
	4.2	Gamma/Gamma XL Monitor Controls ....................................................................................	5
	4.3	TFT-LCD Display ....................................................................................................................	5
	4.4	Alarms ....................................................................................................................................	5
	4.5	Monitor/Software Tracking ......................................................................................................	6
5	Technical Data		6
	5.1	General ...................................................................................................................................	6
	5.2	Environmental ........................................................................................................................	6
	5.3	Display ....................................................................................................................................	7
	5.4	Outputs ...................................................................................................................................	8
	5.5	Connectors .............................................................................................................................	8
6	Monitor Controls		9
	6.1	Main Screen Key ....................................................................................................................	9
	6.2	Menu Key ...............................................................................................................................	9
	6.3	Alarm Limits Key ..................................................................................................................	10
	6.4	Alarm Silence Key ................................................................................................................	10
	6.5	All Alarms Off Key ................................................................................................................	10
	6.6	NBP Start/Stop Key ..............................................................................................................	10
	6.7	Fast Access Key ...................................................................................................................	10
	6.8	Record Key ...........................................................................................................................	10

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Contents

I

Contents

Function Description

1	Overview		15
2	Parameter Inputs		15
3	Main PC Board		15
	3.1	LCD Control ..........................................................................................................................	16
	3.2	Network Interface .................................................................................................................	16
	3.3	Front Panel Circuitry .............................................................................................................	16
	3.4	Pod Interface ........................................................................................................................	16
	3.5	Battery Control and ON/OFF Control ...................................................................................	16
	3.6	BOOT Process, Flash Memory, and DRAM .........................................................................	16
	3.7	SRAM ...................................................................................................................................	17
	3.8	68HC912D60A Microcontroller .............................................................................................	17

4	Front End		17
	4.1	NBP Control ..........................................................................................................................	17
	4.2	Safety ...................................................................................................................................	17
5	Physiological Parameter Data Acquisition		18
	5.1	ECG/Resp ............................................................................................................................	18
	5.2	Respiration ...........................................................................................................................	20
	5.3	SpO2 .....................................................................................................................................	21
	5.4	Invasive Blood Pressure .......................................................................................................	23
	5.5	Non-Invasive Blood Pressure ...............................................................................................	24
	5.6	Temperature Circuit ..............................................................................................................	27
6	etCO2 Pod		28
7	Power Supply System		29
	7.1	Main Battery .........................................................................................................................	29
	7.2	AC Power Adapter ................................................................................................................	30
II	Dräger Medical AG & Co. KGaA		Contents

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Contents

Maintenance Procedures

1	Maintenance Procedure		33
	1.1	General .................................................................................................................................	33
	1.2	Battery ..................................................................................................................................	33
	1.3	Replacing NBP Air Intake Filter ............................................................................................	33
	1.4	Safety and Function Tests ....................................................................................................	34
	1.5	Acceptance Test Report .......................................................................................................	45

Schematics and Diagrams

1	IBP Connector	49
2	MultiMed Pod Connector	49
3	Docking Station Connector	50
4	Alarm Cable (Unterminated)	50
5	Interface Plate Connector	51
6	Recorder/Alarm Y-cable	51
7	Infinity Docking Station Connectors	52
8	PodPort Connector Pins	53

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Fault-Cause-Remedy

1	Troubleshooting		57
	1.1	Power Problems ...................................................................................................................	57
	1.2	Optical Encoder Malfunction ................................................................................................	59
	1.3	TFT-LCD Display Malfunction ..............................................................................................	59
	1.4	Fixed Key Fails to Function ..................................................................................................	60

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Contents

III

Contents
1.5	Visual or Audible Alarm Reporting Failure ............................................................................	60
1.6	NBP Malfunction ...................................................................................................................	60
1.7	etCO2 Malfunction ................................................................................................................	61
1.8	No Printout from Recorder ....................................................................................................	62
1.9	Isolating Cable Malfunctions .................................................................................................	63
1.10	Patient-Related Data Not Retained or Monitor Fails to Compute Trends .............................	63

Annex

Spare parts list

Test List

Problem Report

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IV

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Contents

General

1

2

Gamma / Gamma XL Patient Monitor	General

General

1 Advisory

2Important information

This document corresponds to the version/revision level effective at the time of system delivery. Revisions to hardcopy documentation are not automatically distributed.

The installation and service of equipment described herein is to be performed by qualified personnel who are employed by Dräger Medical or one of its affiliates or who are otherwise authorized by Dräger Medical or one of its affiliates to provide such services.

Assemblers and other persons who are not employed by or otherwise directly affiliated with or authorized by Dräger Medical or one of its affiliates are directed to contact one of the local offices of Dräger Medical or one of its affiliates before attempting installation or service procedures.

This Technical Documentation/Service Manual conforms to the International Standard IEC 60601-1.

Read each step in every procedure thoroughly before beginning any test. Always use the proper tools and specified test equipment. If you deviate from the instructions and/or recommendations in this Technical Documentation/ Service Manual, the equipment may operate improperly or unsafely, or the equipment could be damaged.

The maintenance procedures described in this Technical Documentation/ Service Manual may be performed by qualified service personnel only. These maintenance procedures do not replace inspections and servicing by Dräger Medical.

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Strictly follow the Instructions for Use/Operating Instructions! This Technical Documentation does not replace the Instructions for Use/Operating Instructions. Any use of the product requires full understanding and strict observation of the product-specific Instructions for Use/Operating Instructions.

Unless otherwise stated, reference is made to laws, regulations or standards (as amended) applicable in the Federal Republic of Germany.

2.1Symbols and Definitions

This symbol is used to provide important information that, if ignored, could lead directly to a patient’s or operator’s injury. It is also used to provide important information that, if ignored, could lead directly to equipment damage and, indirectly, to a patient’s injury.

The following three alert levels are used in this documentation to indicate a hazardous situation and how to avoid it.

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Danger	Danger indicates an imminently hazardous situation
	which, if not avoided, will result in death or serious
	injury.
Warning	Warning indicates a potentially hazardous situation
	which, if not avoided, could result in death or serious
	injury.
Caution	Caution indicates a hazardous situation which, if not
	avoided, may result in minor or moderate injury. Caution
	may also be used to alert against unsafe practices.

Danger

Danger indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury.

Note

This symbol is used to provide additional information, operating tips, or maintenance suggestions.

		Definitions according to German standard DIN 31051:
		Inspection	= examination of actual condition
		Servicing	= measures to maintain specified condition
		Repair	= measures to restore specified condition
		Maintenance	= inspection, servicing, and repair
3	Introduction	In keeping with the service strategy for the Infinity Gamma Patient Monitor
		and the Infinity Gamma XL Patient Monitor, this technical manual provides
		the necessary information required to maintain a Gamma/Gamma XL Patient
		Monitor in the field. The Gamma and Gamma XL are both stationary and por-
		table monitors designed to monitor patient vital signs (refer to user’s guide for
		monitoring options). For stationary operation near a bedside, the monitor is
		connected to an AC/DC power adapter or placed on a specially designed
		docking station attached to a shelf, wall, or rolling stand that securely locks it
		into place. While on the docking station, the monitor is powered by an IDS
		power supply. When the monitor is detached from an IDS, it is powered by a
		lead acid battery or by an optional Lithium ion battery. The monitor is reat-
		tached to the AC/DC Power Adapter or placed back on an IDS to recharge
		the battery.
3.1	Service Strategy	The monitor has been designed for high reliability, with an estimated MTBF of
		50,000 hours (5.7 yrs.) of continuous operation.Therefore, the service strat-
		egy is based on few failures in the field, a clear definition of failure analysis by
		field service personnel, and a quick repair turnaround. The field repair philos-
		ophy is based on the distributed and approved spare parts list.
		This manual is intended to serve as a source of technical information, for
		qualified field service personnel to use in maintaining a Gamma/Gamma XL
		patient monitor in accordance with the Dräger Medical Service Strategy. Field
		service is expected to be successful “First-Time Every Time.”
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Gamma / Gamma XL Patient Monitor			General
4	Product Overview	Gamma and Gamma XL Patient Monitors are light-weight, battery-equipped,
		hand-held or semi-permanently mounted devices for general purpose moni-
		toring of a preconfigured set of physiological parameters. When not con-
		nected to a hospital’s main ac power, they use a battery with approxi-mately
		1¼ hours (3 hrs. for Li option battery) of operating time. A power adapter or
		IDS, which also charges the battery, can be used to operate the monitor from
		the hospital’s main ac power circuit.

4.1Monitored Patient The Gamma/Gamma XL monitors the following physiological parameters:

Parameters	• ECG (three-lead, five-lead, or six-lead pod)

•Respiration

•Pulse Oximetry (SpO2 and PLS)

•Temperature

•NBP

•IBP1, IBP2 (locked option)

•etCO2 via PodComm Port (locked option)

•Arrhythmia

•OCRG (locked option)

•Dual Lead S-T Segment Analysis (locked option)

•Anesthetic Gas Monitoring (Gamma XL only, locked option)

4.2Gamma/Gamma XL All functions are controlled by a 16-position rotary knob and nine front panel

	Monitor Controls	fixed keys - Alarm Silence, Record, Alarm Limits, NBP Start/Stop, All Alarms
		Off, Fast Access, Main Screen, Menu, and ON/OFF. Turning the rotary knob
		locates different menu items, and pressing the knob in selects the item.
		Depending on the item selected, pressing the knob in may either bring up
		another menu or initiate an action. See Section 5 Technical Data. For detailed
		operating instructions, consult the Gamma/Gamma XL Patient Monitor User
		Guide applicable to the installed software.
4.3	TFT-LCD Display	The Gamma Patient Monitor has a 6.5 inch (16.5cm), 3-channel (optional 4th
		channel) color TFT-LCD display. The Gamma XL Patient Monitor has an 8.3
		inch (21cm), 4-channel color TFT-LCD display. Waveforms display in Erase
		Bar mode at 25 ±20% mm/s (except for respiration and etCO2 waveforms
		which display at 6.25 ±20% mm/s). All displays for a given parameter (label,
		unit of measure, and waveform) are in the same color. If a waveform is not
		displayed for a parameter, its label is gray.
4.4	Alarms	Alarm limits can be set either on a user-definable setup table, or automatic-

ally based on current parameter values. Three alarm grades, each with a distinct alarm tone, announce alarm situations of varying severity, as follows:

• life-threatening (asystole or ventricular fibrillation - red)

• serious (parameter limit alarms - yellow)

• advisory (technical alarms - white)

The message field background and parameter field of the parameter in alarm, and alarm LED, are displayed in the color associated with the alarm grade as given above.

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General	Gamma / Gamma XL Patient Monitor

4.5Monitor/Software Each monitor has a unique ID chip installed in its rear housing for diagnostic

Tracking

and tracking purposes, and un/locking optional software features.

5 Technical Data

5.1General

Technical Data included in this Section is as of publication date of this Manual. Changes are reported in User Guide applicable to installed SW.

Table 1 General Specifications

	Parameter					Specification
	Power Requirements					100-250 VAC through AC power adapter
	Mains Frequency					50/60 Hz
	AC Power Consumption					60 VA AC
	Battery Type					Lead-acid: PANASONIC LC-T121R8PU or equivalent
						Lithium-ion: Dräger Medical Li+ Battery Pack
	DC Input					11 - 14 V; 32 W continuous, 49 W peak
	Battery Operating Time (means running with NBP mea-					Lead-acid: 75 mins
	surement every 15 min @ 25°C temperature, no etCO2
	running					Lithium-ion: 180 mins
	Battery Recharging Time					Lead-acid: 5 ½ hours, typical
						Lithium-ion: 8 hours, typical
	Battery Charge/Discharge/Charge:					Lithium-ion only (operating as defined above): 2 hours,
						charging for 2 hours, operating 2 hours
	Patient Leakage Current					<10 A @ 110 V and 60 Hz (per UL 544)
						<10 A @ 220 V and 50 Hz (per IEC 601-1)
	Chassis Leakage Current with battery eliminator					<100 A @ 110 V and 60 Hz (per UL 544)
						<500 A @ 220 V and 50 Hz (per IEC 601-1)
5.2		Environmental	Table 2	Environmental Specifications
	Parameter					Environmental Specification
	Cooling Method					Convection and cooling chimney (no fan)
	Temperature:
	Operating					0°C to +40°C (without recorder)	reserved.	03.12.04
	Storage					-20°C to +50°C
	Relative Humidity:						Copyrightreserved.rightsAll	General.fmSMXLGammaGamma
	Operating					>30% and <95%, non-condensing
	Storage					>10% and <95% non-condensing
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	Gamma / Gamma XL Patient Monitor					General
	Parameter				Environmental Specification
	Altitude:
	Operating				-381 to +3048 m (-1250 to 10,000 ft.)
					525 to 795 mmHg (70.0 to 106 kPa)
	Storage				-381 to 5486 m (-1250 to 18,000 ft.)
					375 to 795 mmHg (50.0 to 106 kPa)
	Water Resistance				Drip-Proof
	Gamma Dimensions (H x W x D)				196 x 249 x 134 mm (7.7 x 8.8 x 5.3 in)
	Gamma XL Dimensions (H x W x D)				196 x 267 x 147 mm (7.7 x 10.5 x 5.8 in)
	Weight:
	Gamma Monitor (w/o etCO2)				2.87 kg (6.32 lbs) w/o battery
	Gamma XL Monitor (w/o etCO2)				3.32 kg (7.32 lbs) w/o battery
	Battery				Lead-acid: 0.55 kg (1.22 lbs)
					Lithium-ion: 0.35 kg (0.78 lbs)
	Finish:				Front: white
	according to Dräger Medical Corporate Design Guide-				Rear and Handle: blue
	lines				Material: ABS Polycarbonate Blend (injection molded
					plastic)
5.3		Display	Table 3	Display Specifications
	Parameter					Specification
	Type					Color Liquid Crystal Display (LCD)
	Size					Gamma = 16.5 cm (6.5 in)
						GammaXL = 20 cm (8 in)
	Resolution					640 x 480 pixels
	Active Viewing Area					132.5 x 99.4 mm
	Pixel pitch					Gamma = 0.207 x 0.207 mm
						Gamma XL = 0.267 x 0.270 mm
	Sweep Speeds					fixed 25 mm/s ±20% for ECG, SpO2, and IBP curves
						fixed 6.25 mm/s ±20% for Resp and etCO2 curves
						fixed 1.0 mm/s ±20% for optional OCRG curve
	Display Mode					Erase bar (updates waveforms from left to right)

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General	Gamma / Gamma XL Patient Monitor

5.4		Outputs	Table 4	Output Specifications
	Parameter					Specification
	QRS Synchronization:
	Timing:					For heart rates from 30 to 250 [1/min], with QRS widths
						from 40 to 120 msec and QRS amplitudes from 0.5 to 5
	Output Pulse:					mV, a sync pulse is delayed no more than 35 msec from
						peak of R-wave for each valid QRS complex.
						+12 V, 100 ms duration
	Alarm Output					12 V Open collector output for external alarm indicator
	Recorder					UART interface w/ recorder through interface plate or
						docking station connector
	Debug Port					UART interface w/ a PC to retrieve diagnostic information
						through interface plate or docking station connector
	External VGA					Video signals sent to external VGA display for remote
						viewing of Gamma screen. -- not available when Infinity
						Serial Hub interface plate in use.
	Export Protocol					UART interface w/ external devices using proprietary
						export protocol. -- not available when Infinity Serial Hub
						interface plate in use.
	Network					Serial connection to Infinity Network through Infinity LAN
						or docking station connector, or with a wireless PC card
						in an Infinity Wireless Network.
5.5		Connectors	Table 5	Connector Specifications
	Parameter					Specification
	DC Input					Dräger Medical 2-pin power connector
	Docking Station					Dräger Medical 28-pin connector to provide Alarm Output,
						Recorder, Debug Port, Network, External VGA and Power
	Memory Card					PCMCIA slot
	QRS Sync					Phone jack connector
	MultiMed Pod					16-pin shielded female input connector
	IBP					7-pin shielded female input connector
	NBP Hose					One-hand coupling system
	etCO2					7-pin shielded female PodComm connector

Note

For patient parameter specifications, refer to User Guide applicable to installed software version.

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Gamma / Gamma XL Patient Monitor			General
6	Monitor Controls	The rotary knob in the lower right corner of the front panel is a pointing and
		selecting device. Turn the knob to select a screen area or menu item or to
		change a default value, and press the knob in to confirm your selection and to
		set a default value. Press Main Screen key to return to the MAIN screen.

Note

Instructions in this chapter are intended to provide only a cursory overview of basic monitor controls for accessing and performing service-related functions. Refer to the User Guide for the installed software version for complete operating information.

6.1Main Screen Key Pressing the Main Screen key exits the current menu or screen and displays

		the home screen.
6.2	Menu Key	-- provides access to Main menu. In general, functions of direct concern to
		the FSE or Biomed are accessed via Monitor Setup → Biomed on Main
		menu. Only authorized personnel should perform password-protected ser-
		vice-related functions. Use Biomed password (375) to access the following:
		• Save Setups - Confirm or Cancel
		• Locked Options - four locks into which monitor-specific 2-digit codes must
			be entered to enable locked options
		•	Diagnostic Logs
		•	Units
			a)	Temperature - °C or °F
			b)	etCO2 - mmHg, kPa, Vol %
			c)	Pressure - mmHg or kPa
			d)	ST - mm, mV
		• Service - requires Service password. (The password is given on the Ser-
			vice Setup Instructions for the installed software version.)
			a)	Update Software Load
			b)	Test Pulse (Confirm or Cancel - one-shot test pulses for ECG (1mV
				spike) and Temp (-5°C and +50°C, respectively). An additional test is
				performed for IBP, Resp Pulse, and SpO2. Test indication is reported
				in trend table.)
			c)	Monitor Setup Language
			d)	SCIO Port X5
			e)	USB
			f)	Data Collection OFF
			g)	SpO2
			h)	NBP
			i)	Line Frequency 50
			j)	60
			k)	Service
			l)	Network SetupNetwork Config SSID
			m)	Central Yes
			n)	Station No

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General	Gamma / Gamma XL Patient Monitor

o)Keep Bed Yes

p)Label No

q)Network WEP Transmit Key

r)Key 1

s)Key 2

t)Key 3

u)Key 4

v)Network Config

w)Network Setup

x)Network IP Address

y)Info Network Setup

z)Service

•Exit

Note

Set the line frequency equal to the ac mains line according to local conditions (50 or 60 Hz). An incorrect setting of line frequency can cause artifact or excessive waveform noise on the ECG waveform.

6.3Alarm Limits Key -- calls up a setup table for alarms.

1.Turn rotary knob to select desired parameter field and limits, and press knob in to activate your selection.

2.The number representing the limit value turns black on a blue background, indicating that you can change it. Turn knob to change value.

3.When desired setting is displayed, press knob in to set value.

4.Press MAIN Screen key to return to MAIN screen.

6.4Alarm Silence Key -- silences an active alarm tone for 1 minute ±5 seconds, and turns active

blinking parameter areas into active steady parameter areas

6.5All Alarms Off Key -- suspends alarms for a fixed 3-minute ±5 second period.

6.6NBP Start/Stop Key -- starts and stops non-invasive blood pressure measurement.

6.7	Fast Access Key	-- allows access to the monitor’s bottom channel menu as well as tabular
		trends, graphical trends and Event recall screen.
6.8	Record Key	-- starts a manual, timed recording on a connected R50™ recorder or on a
		networked postscript laser printer in an Infinity Network.

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Gamma / Gamma XL Patient Monitor	General

Note

If a recorder or networked postscript laser printer is not available, pressing the Record fixed key writes 15 seconds of waveform and vital signs information to internal memory. Monitors can store up to ten recordings, which are automatically printed as soon as the recorder or networked postscript laser printer is available.

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Function Description

13

14

Gamma / Gamma XL Patient Monitor	Function Description

Function Description

1 Overview

Infinity Gamma and Gamma XL Patient Monitors are configured monitors running on one processor, an MPC823E Power PC processor, which attends to all monitoring functions, controls all graphics functions, generates video and timing signals for the LCD screen, and interfaces with the PCMCIA card and USB port. It also performs several peripheral control functions, such as NIBP control, audio volume control, and timing generation for the front end. See Figure 1.

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Figure 1 Infinity Gamma / Gamma XL Patient Monitor Block Diagram

2	Parameter Inputs	The data acquisition front end acquires and digitizes signals derived from a
		three-, five-, or six-electrode ECG patient lead set, a Nellcor® or Masimo®
		SpO2 transducer, an Impedance respiration measurement system, a ther-
		mistor-based Temperature transducer, and two strain-gauge IBP transducers
		(IBP2 = locked option). The NIBP main transducer signal is digitized together
		with the rest of the front end parameters. See Section 4 Front End and Sec-
		tion 5 Physiological Parameter Data Acquisition for more detailed information.
3	Main PC Board	The Main MPC823E Power PC processor not only attends to monitoring
		functions, but also controls all graphics functions, generates the video and
		timing signals for the LCD screen, interfaces with the PCMCIA card and USB

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Function Description	Gamma / Gamma XL Patient Monitor

		port, and controls the network link. In addition, it performs a host of peripheral
		control functions, such as NIBP control, audio volume control, and timing
		generation for the front end.
3.1	LCD Control	A set of buffer/drivers are used to drive the 6.5” screen in Gamma monitors or
		the 8.3” screen in the Gamma XL monitors. In parallel, a triple video DAC

generates analog RGB signals for an external VGA monitor (typically a CRT or LCD).

3.2Network Interface The Infinity Gamma / Gamma XL Monitor interfaces with the physical inter-

face device (e.g., IDS) automatically, when connection to the device has been detected. Connections to Infinity network services are established and maintained by software components resident on both the Gamma and Gamma XL Monitor and the physical interface device.

3.3Front Panel Circuitry The front panel circuit processes the audio information, drives the fluorescent

tubes on the LCD, implements a secondary alarm in case the unit resets or turns off, and routes the video and timing signals to the screen. It also routes the UART signal coming from the Pod interface to the main board Quad UART.

3.4	Pod Interface	The Pod Interface generates an isolated voltage to power the pod and also
		converts the Pod Comm protocol from the pod into a UART stream that can
		be interpreted by the microprocessor.

3.5Battery Control and The Pb-acid or Lithium battery charging and discharging cycles are controlled

ON/OFF Control	by a special charger circuit. The circuit initiates a charge cycle when com-
	manded by the microcontroller. The charge cycle for a Pb-acid consists of a
	bulk charge period in which the battery is being supplied a constant current of
	~400mA, a constant voltage period in which the battery voltage is held con-
	stant at ~14.8V and the current is allowed to diminish as the charge
	approaches 100%, and a float cycle in which the voltage is maintained at
	~13.7V. For Lithium batteries, the charger circuit acts as a constant voltage
	source of 16.8V. The battery is charged from a switching supply controlled by
	the charger chip. The microcontroller also reads the front panel keys and the
	rotary knob, encodes the information coming from them, and routes it to the
	main processor. When the On/Stdby key is pressed, it turns the monitor on
	and off. In addition, the microcontroller controls the NIBP safety timer.

3.6BOOT Process, Flash Memory, and DRAM

The BOOT EEPROM contains the boot code and is preprogrammed at the factory. It can be reprogrammed in the field by means of a special PCMCIA card, if required. (Contact your local Dräger Medical service representative.)

The executable software normally resides as compressed operational code in Flash memory. When the 68HC912D60A microprocessor senses that the on/off switch on the front panel has been pressed, it turns on (or turns off) the 3.3V and 5V supplies. As the 3.3V supply turns on, it wakes up the MPC823E main processor, which begins execution from the BOOT PROM. During boot initialization, the main processor attempts to read the Memory Card to detect authorized software. If a authorized software memory card is present, the software is loaded from the card. Otherwise, the main processor loads software from the Flash to the main processor DRAM, from which it completes initialization and enters operational mode. DRAM contains expanded operational code, and data space variables and stacks.

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Gamma Gamma XL SM Function Description.fm 03.12.04

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Gamma / Gamma XL Patient Monitor			Function Description
3.7	SRAM	The 512K x 8 SRAM is battery backed up and is used for error logs, trends,
		recordings and other non-volatile memory uses.
3.8	68HC912D60A	The 68HC912D60A microcontroller, with 64K of EEPROM and 2048 bytes of
	Microcontroller	RAM, is powered as long as there is a main supply plugged into the system
		or when the user presses the ON/OFF button. The code is stored in its inter-
		nal flash memory, but can be downloaded from the MPC823E. The microcon-
		troller performs the following functions:
	On/Off control	When the ON/OFF push button (either local or remote is pressed), the micro-
		controller activates the 3.3V and 5V supplies, which wakes up the MPC823E
		through a power-on reset. In addition, the microcontroller has control over a
		flyback supply, which comes on any time the unit is plugged into AC power (in
		order to charge the battery) or is turned on.
		The microcontroller also reads the front panel keys and the rotary knob,
		encodes the information coming from them, and routes it to the main proces-
		sor.
	NBP Valve modulation	When directed by the main processor, the microcontroller supplies modula-
		tion signals for the two NBP manifold valves.
	NBP Safety Timer	When the pump or the valve V2 are turned on, the microcontroller initiates a
		128 sec. timer (90 sec. or 60 sec. for neonates) which, if exceeded, produces
		an NBP fault and results in cut off of main 12V power to the NBP manifold.
	Battery Charger	The microcontroller initiates a battery charge when needed, and stops the
		charging process when the battery reaches full capacity. It can recognize
		whether a Pb or Lithium battery is connected into the system, and directs the
		battery controller chip to charge to different levels depending on the battery
		type. See Section 3.5 Battery Control and ON/OFF Control. The microcontrol-
		ler also acquires the battery voltage and current for monitoring purposes.
	Recorder Power	The microcontroller controls power applied to a stand-alone R50 Recorder.
	Main Audio Generator	The microcontroller generates the fundamental audio frequency of the unit’s
		tone generator, as directed by the main microprocessor.
	USB Power	When directed by the MPC823E, the 68HC912D60A microcontroller turns
		power ON/OFF on USB buss and determines the transaction speed.
4	Front End	All physiological signals (except etCO2) are digitized through a high speed
		multiplexing system and a common 16 bit ADC. The data is then transferred
		through the isolation barrier to an HDLC port in the main processor, where it
		is digitally filtered and processed.
4.1	NBP Control	The NBP main transducer signal is digitized together with the rest of the front
		end parameters. However, the redundant (overpressure) transducer is pro-
		cessed separately on the grounded end of the board. The pump on/off signal
		and valve enable signals are generated off of the MPC 821 microprocessor.
		The PWM signals for the valve flow control and the redundant safety timer
		are implemented in a separate microcontroller (MC68HC912D60A).
4.2	Safety	• Patient isolation withstands 5kV during defib.
		• Leakage currents are limited to safe values normally and during single
		fault conditions.

• Patient is protected against electrosurgical burns at the electrodes.

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Function Description	Gamma / Gamma XL Patient Monitor

•Defibrillation protection does not drain excessive current away from the patient.

•Specially shielded connectors and cables are used to provide excellent immunity up to 1000MHz and can not be touched by the patient even when disconnected.

•Single cable from MultiMed Pod to main Gamma / Gamma XL Monitor unit reduces clutter between bed and monitor.

Figure 2 Front End

5Physiological Parameter Data Acquisition

5.1ECG/Resp

Transducers gather physiological data at the patient and feed them into the small MultiMed Pod at the bed. The MultiMed Pod in turn is connected via a 3-meter cable to the front end in the main unit where analog ECG, Respiration, Temperature, and SpO2 signals are converted to digital form and sent through isolators for processing.

The MultiMed Pod located close to the patient accepts a set of 3, 5 or 6 shielded ECG electrode leads, an SpO2 (Nellcor) cable adapter, and a temperature sensor. The ECG section contains RF filters, and overvoltage clamps that include 1k series resistors to limit shunting of defibrillator current. The SpO2 and temperature sections also contain RF filters. Impedance respi-

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Gamma / Gamma XL Patient Monitor	Function Description

Gamma Gamma XL SM Function Description.fm 03.12.04

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5.1.1ECG

ration is sensed through the ECG electodes. Void-free potting and internal shielding enable compact containment of high voltage defibrillator and electrosurgery pulses. The small interconnecting cable to the main assembly is captive at the MultiMed POD but plugs into the MultiMed front end via a specially shielded connector.

The front end accepts physiological signals from the MultiMed POD connector and feeds temperature, respiration, and ECG signals via RF filters, configuration multiplexers, and pre-amplifiers to a high-speed multiplexer driving a 16-bit analog-to-digital (A/D) converter. The data stream is sent to the Main Processor board via an opto-isolator. Control commands from the Processor are sent out to the front end on a similar isolating link. Isolated DC power is also provided.

The ECG signals are conductively coupled to the isolated circuits via currentlimiting series resistors, whereas the SpO2 signals are optically isolated at the transducer. Temperature signals are doubly insulated at the patient by disposable boots on the sensors. AC (40kHz) excitation currents for respiration monitoring are dc-isolated by high-voltage ceramic capacitors.

The A/D samples the following parameters:

Table 1 Parameter Sampling Table

Parameter	# of Channels
ECG	4
Pace	2
SpO2 Red	1
SpO2 IR	1
NBP	1
Resp	1
Temp	2

The hardware pace detector monitors the ECG signal in two of the four channels (those not connected to the chest leads). All other signals are decimated and filtered using digital signal processing in the MPC823E. High oversampling rate is required to minimize the requirements (and size) of the analog anti alias filters. Superior rejection to ESU and other types of interference is achieved with this type of design.

•Bandwidth is set flexibly by software filters.

•Reconfigurable neutral selector can drive any electrode.

•Lead-on detection functions with even poor electrodes.

•Calibration voltages can be superimposed on patient wave-forms or onto flat baselines.

See Figure 3. Composite electrocardiographic (ECG) signals generated by the heart and by a pacemaker are filtered to reduce RF interference from impedance respiration and electrosurgery and then injected with dc lead-off detection currents. Over-voltage clamps protect the semiconductors from the surges passing the spark gaps in the MultiMed Pod and also reduce the dc current applied to the patient due to a component fault.

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Function Description	Gamma / Gamma XL Patient Monitor

Figure 3 Lead-Forming Network

5.1.2	Lead Selection	A lead-forming network following the RF filter generates the necessary refer-
		ence points for electrocardiographic measurements. Both normal leads (I, II,
		III, V1 and V2) and augmented leads (aVL, avR, and avF) can be obtained.
		Four differential channels generate the main axes I, II, V1 and V2. The
		remaining leads are derived mathematically as indicated in the vector dia-
		gram of Figure 3.
5.1.3	Lead-Off Detection	Lead-off detection is accomplished by introducing a very small current into
		each patient electrode, which would drive the corresponding input high if it
		were disconnected. A set of five comparators detects a lead-off condition.

5.1.4Low-Pass Filtering and The ECG preamplifier has a flat frequency response of 0.5 - 40Hz, with a

	Common Mode	software notch filter at 50/60 Hz. A 180° combined signal drives the neutral
	Enhancement	electrode to increase the CMMR.
5.2	Respiration	Impedance respiration is monitored by injecting a 40 kHz square wave of cur-
		rent into the RA electrode. The resulting 40 kHz voltage drop between the RA
		+ LL electrodes is proportional to the impedance. Especially balanced true
		current sources do not load the ECG electrodes or distort the ECG morphol-
		ogy. The returning 40 kHz differential voltage is amplified, synchronously
		demodulated, and low-pass filtered. An AC-coupled stage with an “autobloc”
		DC restorer feeds the input to the A/D converter with a nominal output of 60
		mV per Ohm.
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Gamma / Gamma XL Patient Monitor	Function Description

5.3SpO2

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	Figure 4 SpO2 Functional Block Diagram
	The pulse oximeter circuit uses a Nellcor® sensor to detect the oxygen satu-
	ration level in arterial blood flow. Determination of the concentration of oxy-
	gen in the blood is based upon the principle that the absorption of red (R)
	light depends on the degree of oxygenation of the blood, whereas the absorp-
	tion of infrared (IR) radiation is relatively independent of oxygenation and
	causes only constant attenuation. See Figure 4. In the SpO2 sensor, R and
	IR light emitting diodes (LEDs) are alternately pulsed ON at a 25% duty cycle.
	The light is transmitted through a well-perfused part of the body, such as a
	fingertip or an ear lobe. The intensity of light (including ambient) transmitted
	through or scattered by the blood is converted to a current by a photodiode in
	the sensor. The current that appears when both LEDs are OFF depends
	mainly on the ambient light, which is later subtracted to leave only the R or IR
	signal levels. The large dynamic range of the light intensities requires con-
	stant automatic monitoring and adjustment.
	The intensities of the R and IR sources are independently controlled by two
	digital-to-analog converters (DACs) attenuating the 2.5 V reference. These
	levels or zero are sequentially selected by a multiplexer, and converted to a
	driving current which is further guided or inverted by an output multiplexer to
	the LEDs in the sensor.
5.3.1 SpO2 Front End	The primary purpose of the SpO2 front end is to convert the sensor’s analog
	signal into individual digitized signals for the red and infrared analog signals
	for processing by the microprocessor. See Figure 5. Circuitry in the front end
	first eliminates the non-pulsatile component in the input signal, then demulti-
	plexes the resulting pulsatile signal to separate the R and IR signal compo-
	nents, and finally converts the demultiplexed R and IR analog signals into
	serial digital data streams.

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Function Description	Gamma / Gamma XL Patient Monitor

Figure 5 Sensor LED Timing Diagram

A sequence of light pulses, driven from the chopped current source in the sensor LEDs, are passed through a finger or an earlobe to a photodiode. The sensor LEDs are connected in an anti-parallel fashion on one pair of wires. A timing generator controls the sensor LEDs and signal multiplexing/ demultiplexing (see Figure 5) by means of three control signals:

		•	IRONL (infrared LED)
		• AMBONL (LEDS not lit)
		•	REDONL (red LED)
5.3.2	Input Stage	A preamplifier converts the photocurrent to an equivalent voltage, and applies
		it to a 20 Hz high-pass filter that removes the non-pulsatile component. The
		output of the preamplifier is fed to a saturation detector.
5.3.3	Brightness Control	If the output of the preamplifier is in saturation, the gate array provides a sig-
		nal to the digital-to-analog converters (DACs), which controls the drive cur-
		rent to increase or decrease the brightness of the LEDs.
		Controlling LED brightness extends the system dynamic range. For a very
		transparent subject it may not be possible to reduce the gain to prevent satu-
		ration. In that event, the brightness must be reduced. An additional purpose is
		to equalize the received amplitude of each wavelength. If both LEDs are
		turned ON to maximum brightness, and the software finds an extraordinary
		difference between the two, the microprocessor tends to reduce that differ-
		ence by equalizing the R or IR brightness signals.
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Gamma / Gamma XL Patient Monitor	Function Description

5.3.4Ambient Light Rejection The ambient rejection amplifier is a synchronous detector. The signal applied

Amplifier	to its inverting input is a composite of R, IR, and ambient signals. The non-
	inverting input is the same signal gated by the timing generator. This synchro-
	nously multiplexes the IR, ambient, and R analog signals.

5.4Invasive Blood Pressure

Figure 6 IBP Functional Block Diagram

The IBP circuit has been designed to be used with a strain gauge pressure transducer. See Figure 6. The analog portion of the IBP circuit provides excitation voltages for resistance bridge transducers. These voltages are derived from a reference which is also used to derive the A/D converter reference voltage. At the circuit input, a resistor divider network provides for transducer unplugged detection. R-C filtering and protection diodes limit the effects produced during electrosurgery, defibrillation, and other such procedures. A selector multiplexer allows for the insertion of calibration signals into the amplifier stage. The multiplexor feeds the pressure signal to a buffer amplifier, which in turn feeds the AD converter analog input. This allows the monitor to measure pressure signals in a range greater than ±700 mmHg with a resolution of approximately .02mmHg/LSB.

When no pressure transducer is plugged into the monitor, the resistor divider network puts a negative signal into the instrumentation amplifier, which propagates through the system to indicate the unplugged condition.

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