The Boyles Design as applied in the GE Aisys Anaesthetic ... · vaporizers. In a closed system, all...

The Boyles Design

as applied in the

GE Aisys

Anaesthetic Machine

Steven Threlfo

John Hunter Hospital Anaesthetics Dept.

Revision

The Classic Boyles Design

GE

Aisys

Gas

Distribution

Diagram

GE

AisysFollowingthe same

path

Gas

Distribution

Diagram

GE

Aisys

Gas

Distribution

Diagram

GE

AisysAdditional

Components

Gas

Distribution

Diagram

GE

Aisys

Some important theory

Electronic Gas Delivery System

Proportional Valve

Feedback from the flow sensor controls proportional valve drive

Electronic Gas Delivery System

Servo Gas Flow Control

Gas

Mixer

GE

Aisys

Electronic Gas Delivery Module

Electronic Gas Delivery System Diagram


Flow Control Valve


Flow Sensor

Electronic Gas Delivery Hot Wire Anemometers


Flow Sensor


Two unique

measurements

of flow are

compared to

ensure safe

gas delivery

Electronic Gas Delivery System Diagram - Pneumatic equivalent

Electronic Gas Delivery System Diagram - Electrical equivalent


Flow 1 Flow 2

GE

Aisys

Alternate

O2 Control

Alternate O2 Control:

• Safety device to allow

administration of 100% O2

from 0.5 - 10 L/min.

• Triggered 3 ways:

• Electronic mixer malfunction,

system reacts in 500 milliseconds.

• LCD screen malfunction; lose

controls.

• No power - mains or battery.

GE

Aisys

Alternate Oxygen Flow Path - Electronic Gas Delivery System


• Requires a cylinder or wall

oxygen supply to be

available.

• Only works when the

power on/off switch is in

the on position.

GE

Aisys

GE

Aisys

Alternate

O2 Control


• Requires a cylinder or wall

oxygen supply to be

available.

• Only works when the

power on/off switch is in

the on position.

• May also allow agent

delivery, provided the

oxygen flow measurement

system is functional.

GE

Aisys

Alternate Oxygen Flow Path - Electronic Gas Delivery System

Gas

Delivery

GE

AisysIn Summary:

• Mixes O2 with AIR or N2O.

• Has N2O shut off and

anti-hypoxic delivery.

( Computer says NO… )

• May be bypassed with 100%

O2 via the alternate oxygen

control system.

Revision

Detachable mechanical vaporizers

In a closed system, all volatile

liquids have a unique vapor

pressure which is driven by

temperature.




temperature.

Low

Temperature




temperature.

Higher

Temperature

Increased

Pressure

Vaporizer - Off - Gas Path

Vaporizer - On - Unit Warm

Vaporizer - On - Unit Cool

Anaesthetic agent boiling points at

a pressure of 1 atmosphere:

Sevoflurane 58.6 °C

Isoflurane 48.5 °C

Desflurane 23.5 °C

(Below normal room temperature)

Desflurane Vaporizer

Datex Ohmeda TEC 6

Desflurane Vaporizer

GE

Aisys

Electronic

Vaporizer

All the functions of a

mechanical vaporizer

are integrated into one

electronically controlled

subsystem

Electronic Vaporizer

Electronic Vaporizer Cassette

Electronic Vaporizer Schematic Drawing

Cassette

Electronic Vaporizer Schematic Drawing

Cassette

Cassette Identification

Selects the software

lookup table relating

saturated vapor

pressure and

temperature.

Cassette Identification

Cassette Interface Connectors

Liquid level detection

and enhanced

temperature sensing.

Cassette Interface Connectors

Temperature Measurement

Central to calculation

of saturated vapor

pressure.

Temperature Measurement

Bypass and Cassette Flow Paths

Cassette

Bypass flow


Cassette

Bypass flow

Cassette flow


Cassette

Cassette Flow Control Valve

Cassette Flow Control Valve

This is a Proportional

Valve

Cassette Inflow Flow Sensor

Cassette Inflow Flow Sensor

If required, the

Cassette Inflow Flow

Sensor is used to

control inlet flow.

Cassette Outflow Flow Sensor

Cassette Outflow Flow Sensor

If required, the

Cassette Outflow Flow

Sensor is used to

control outlet flow.

Cassette Inflow and Outflow Valves

Isolate the vaporizer

cassette from the

machine.

Input Flow Rate

Known from the

electronic gas

delivery system.

Back Pressure Valve

Drives carrier gas

through the vaporizer

cassette.

Inflow Check Valve

Prevents agent

escape upstream of

the Back Pressure

Valve.

Inflow Check Valve

Prevents agent

escape upstream of

the Back Pressure

Valve.

Important if the

cassette pressure

rises to a level

sufficient to open the

Back Pressure Valve.

Bypass Flow Control

Bypass Flow Control

Components work

together to control the

gas splitting ratio.

Bypass Flow Control

Components work



Bypass flow

Bypass Flow Control

Components work



Bypass flow

Cassette flow

Bypass Flow Control

Components work



Sevoflurane and

Isoflurane delivery.

Bypass flow

Cassette flow

Cassette Pressure Transducer

Monitors cassette

pressure.


Monitors cassette

pressure.

Desflurane may have

a saturated vapor

pressure high enough

not to require an

inflow of carrier gas.

Direct Release of Agent

Monitors cassette

pressure.

Desflurane may have

a saturated vapor


not to require an


Outflow is measured

to control Desflurane

concentration.


Monitors cassette

pressure.

Desflurane may have

a saturated vapor


not to require an


Outflow is measured


concentration.

Bypass flow


Monitors cassette

pressure.

Desflurane may have

a saturated vapor


not to require an


Outflow is measured


concentration.

Bypass flow

Cassette flow


Monitors cassette

pressure.

Once Desflurane has

cooled below its

boiling point, it will no

longer vent into the

gas stream under its

own pressure.

Bypass flow

Bypass Flow Control

Cool Desflurane can

be vaporized in the

same manner as

Sevoflurane and

Isoflurane.

Bypass Flow Control

Bypass flow

Cool Desflurane can

be vaporized in the

same manner as

Sevoflurane and

Isoflurane.

Bypass Flow Control

Bypass flow

Cassette flow

Cool Desflurane can

be vaporized in the

same manner as

Sevoflurane and

Isoflurane.

Bypass Flow Control

Bypass flow

Cassette flow

Cool Desflurane can

be vaporized in the

same manner as

Sevoflurane and

Isoflurane.

This is the key to the

Evap dealing with all

three volatile agents.

Input and Output Flow Comparison

Provides additional

input to the control

software.

Input and Output Flow Comparison

Provides additional

input to the control

software.

Hardware self-checks

and monitoring of

vaporizer gas flows

during use.

Scavenging Valve

Vents excess

cassette pressure.

Scavenging Valve

Vents excess

cassette pressure.

Connected to the

exhaust scavenging

system.

Liquid Flow Prevention Valve

A ball float safety

device to seal the

outlet path if liquid

escapes from the

vaporizer cassette.


A ball float safety

device to seal the


escapes from the

vaporizer cassette.

Only operates if an

overfilled cassette is

installed or agent is

added during

machine operation.


A ball float safety

device to seal the


escapes from the

vaporizer cassette.

Only operates if an

overfilled cassette is

installed or agent is

added during

machine operation.

Gas flow anomaly

causes an immediate

system shutdown.

Electronic Vaporizer Control

Electronic Vaporization:

• Automatically detects the agent cassette installed in the machine.

• Monitors agent temperature and adjusts the gas splitting ratio.

Agent Identification and Concentration

Control Button

Electronic Vaporizer Control

Electronic Vaporization:

• Allows accurate volatile agent delivery during low flow anaesthesia.

• Opens the door to End Tidal or “Cruise Control” anaesthesia.

Agent Identification and Concentration

Control Button

Advanced

Breathing

System

(ABS)

GE

Aisys

The ABS is an integrated

circle breathing system and

ventilator bellows assembly.

ABS and Ventilator Schematic

GE Aisys - ABS - Hand Bag

Inspiration Exhalation

GE Aisys - ABS - Ventilator

Inspiration Exhalation

The Aisys Flowmeter AssemblyMeasures flow in the

inspiratory and

expiratory limbs of the

circle breathing

system.

Two variable orifice

flow detectors

connect to separate

differential pressure

transducers.

Calibration data, recorded during

manufacture, is retained in an

EPROM located inside the flow

detector connecting plug.

Flowmeter Differential Pressure

Transducers

Ventilator Operation


Drive calibration is used to explain how components

of the ventilator control system operate.

The phases of operation of the ventilator in volume

control and pressure control modes complete the

picture.

Ventilator Drive - Major components

Ventilator Drive - The ventilator control system is reliant on

accurate pressure delivery to the proportional flow control

valve.

Ventilator Drive - The ventilator control system is reliant on

accurate pressure delivery to the proportional flow control

valve. ( The regulator has a 1% tolerance on adjustment. )

Ventilator Drive - The control system provides electrical output

to drive the proportional flow control valve.

Ventilator Drive - The control system provides electrical output

to drive the proportional flow control valve. The control system

also receives feedback from the pressure sensor.

Ventilator Drive - A calibrated pressure test gauge is

connected to the output.

Ventilator Drive - A calibrated pressure test gauge is

connected to the output. With no drive to the proportional flow

control valve, the pressure sensor zero is established.

Ventilator Drive - With the test pressure gauge connected, a leak

via the pneumatic resistance allows the control system to be

manually driven to a prescribed pressure.

Ventilator Drive - With the test pressure gauge connected, a leak

via the pneumatic resistance allows the control system to be

manually driven to a prescribed pressure. This establishes the

pressure sensor calibration.

Ventilator Drive - With a stopper to seal the output, the control

system then ramps up the valve drive output.

Ventilator Drive - With a stopper to seal the output, the control

system then ramps up the valve drive output. The valve drive

versus pressure characteristic of the system is automatically

“mapped” into the control system memory.

Ventilator Drive - A calibration orifice is connected to the output.

Ventilator Drive - A calibration orifice is connected to the output.

The size and shape of the orifice is precisely machined to result

in a known pressure versus flow characteristic.

Ventilator Drive - The control system then ramps up the valve

drive output to increase pressure.

Ventilator Drive - The control system then ramps up the valve

drive output to increase pressure. By calculation, the valve

drive versus flow characteristic of the system is automatically

“mapped” into the control system memory.


Calibration maps the relationship between:

• Valve drive and pressure

• Valve drive and flow

Ventilator Operation - VCV

Ventilator Operation - PCV

Remember - VCV at this point

where drive to the canister is withdrawn

Ventilator Operation - PCV

Ventilator Operation - Summary

• Pure VCV and PCV operation represent

both ends of the spectrum.




• All Aisys ventilator modes are variations

or blends of VCV and PCV operation.






• Aisys ventilator capabilities match those

of an advanced ICU ventilator.






• Aisys ventilator capabilities match those

of an advanced ICU ventilator.

• Adult and paediatric patients require a

change of circuit with compliance

determined during the machine self test.


• The ventilator control system integrates

inspiratory flow to determine delivered

volume.


• The ventilator control system integrates

inspiratory flow to determine delivered

volume. As a result, it can compensate

for gas flow entering the breathing

system during inspiration.


Inspiration


Inspiration In volume delivery, the flow toward the patient on inspiration is the sum of flow returned from the ventilator bellows added to the fresh gas flow from the gas delivery system.



The flow rate measured by the flow sensor is integrated to determine delivered volume.



The flow rate measured by the flow sensor is integrated to determine delivered volume.

Ventilator drive is continually perfecting inspiratory volume.


• At low gas flows the ventilator bellows

will have maximum excursion.


• At low gas flows the ventilator bellows

will have maximum excursion.

• At high gas flows the ventilator bellows

will have a lower excursion.

Waste Gas Scavenging

Scavenger Assembly

Scavenger Schematic

Scavenger flow is monitored by the pressure drop across the

signal orifice and displayed by a small flowmeter mounted on the

side of the machine.

Scavenger Schematic

Scavenger flow is monitored by the pressure drop across the

signal orifice and displayed by a small flowmeter mounted on the

side of the machine. Scavenger Flow > Machine Exhaust Flow.

One important

message on

electronically

controlled

equipment.

Keep corrosive solutions away from machines.

Keep corrosive solutions away from machines.

Damage to Aisys

ventilator drive

system.

Something for

analysis

2 LPM Alternate Oxygen Flow Set

What failed and how?

Error Log: 23-Jul-2013, 22:40:08, Mix: FLOW ATTAINMENT FAILURE CH123-Jul-2013, 22:40:09, EGC EXIT ALT O223-Jul-2013, 22:40:10, O2 FLOW CTRL FAIL23-Jul-2013, 22:40:10, EXPIRED GAS CONTROL AUTO EXITED

Conclusion

Photograph - Gandhi Smriti

Delhi India - 2013

The End

The Boyles Design as applied in the GE Aisys Anaesthetic ... · vaporizers. In a closed system, all...

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