Speaker : Dr Omar Kamal

To safeguard human life from unknown human errors.

Safety devices are to prevent delivery of hypoxic mixture

Regulation to prevent excessive pressure which is traumatic to patient

1979: American National Standards Institute (ANSI)

1988: American Society for Testing and Materials (ASTM) F1161-883

1994: ASTM F1161-944 (reapproved in 1994 and discontinued in 2000)

2000: ASTM F1850-005

2000 ASTM F1850-00 standard, newly

continuous breathing system pressure,

exhaled tidal volume, ventilatory CO2 concentration,

anesthetic vapor concentration, inspired oxygen concentration,

oxygen supply pressure, arterial oxygen saturation of hemoglobin,

arterial blood pressure, and continuous electrocardiogram

Master Switch

Power Failure Indicator

Reserve Power

Electrical Outlets

Circuit Breakers

Data Communication Ports

High pressure division

Intermediate pressure division

Low pressure division

Gas cylinder

Color coding

Cylinder labels

Symbol of gas

Pin index safety system

Safety relief device

Filling within service pressure

Oxygen black body,white shoulders

Nitrous oxide blue

Air white and black

Carbon dioxide gray

Helium brown

Entonox black with blue/white shoulders

The safety relief device is composed of atleastone of

- Frangible disc [bursts under extreme pressure]

- Fusible plug [wood’s metal which has a low melting Point ]

- Safety relief valve [ opens at extreme pressure ]

Check valves at the cylinder inlet and pipeline inlet

Cylinder pressure indicator [ bourdon’ s pressure gauge]

Pressure regulator

Pressure relief valves

Washer [ bodok seal ] – rubber made of neoprene

Gauge is usually color coded.

Name and symbol of gas are written over dial.

If bourdon tube ruptures gas is vented from back side

Gauges are angled and placed in such a way that it can be easily read by anesthetist.

Instructions like “use no oil’’ “open the valve slowly’’ are written on the gauge

Pressure regulators have safety relief valves

Safety valve blow off at a set pressure of 525 k pa(70psi)

Pipeline

• wall outlet : labelled and colour coded

• primary valve or automatic shut off valve

• secondary valve or isolation valve

• schraeders probes, quick connectors or diameter index safety system to prevent interchangeability

• pipeline hoses – colour coded

The 2000 ASTM F1850-00 standard states that

“The anesthesia gas supply device shall be designed so that whenever oxygen supply pressure is reduced to below the manufacturer specified minimum, the delivered oxygen concentration shall not decrease below 19% at the common gas outlet.”

fail-safe valve

is located downstream from the nitrous oxide supply source.

This valve shuts off or proportionally decreases the supply of nitrous oxide (and other gases) if the oxygen supply pressure declines

Datex-Ohmeda machines

Threshold principle

This valve operates in a threshold manner and is either open or closed.

Oxygen supply pressure opens the valve, and the valve return spring closes the valve

OFPD is based on a proportioning principle

The pressure of all gases controlled by the OFPD will decrease proportionally with the oxygen pressure.

consists of a seat nozzle assembly connected to a spring-loaded piston

The oxygen flow control knob is distinctively fluted, projects beyond the control knobs of the other gases, and is larger in diameter

All knobs are color-coded for the appropriate gas,

the chemical formula or name of the gas is permanently marked on each.

If a single gas has two flow tubes, the tubes are arranged in series and controlled by a single flow control valve.

- Bobbin rotates on flow which prevents it from sticking.

- Antistatic spray in flowmeter- master and slave safety mechanism for gas delivery

between N2O and O2- Downstream placement of oxygen flowmeter- Radio florescent plastic sheet behind flow meter- Float stop- Auxiliary oxygen flowmeter

An oxygen leak from the flow tube can produce a hypoxic mixture, regardless of the

arrangement of the flow tubes

Proportionating devices –

• link 25 in datexohmeda[mechanical,pneumatic

and electronic linkage]

• S-ORC( sensitive oxygen ratio controller)

ORMC( oxygen ratio monitor controller) in draeger,

• Mandatory minimum oxygen flow :

150 to 250 ml/min

It allows independent adjustment of either valve, automatically intercedes to maintain a minimum 25% oxygen concentration with a maximum N2O– oxygen flow ratio of 3 : 1

increases oxygen flow to prevent delivery of a hypoxic mixture.

14-tooth sprocket (nitrous oxide flow control valve) , 28-tooth sprocket (oxygen flow control valve)

2 : 1 gear ratio

Pneumatic oxygen–nitrous oxide interlock systems designed to maintain a fresh gas oxygen concentration of at least 25%

ORMC and S-ORC limit nitrous oxide flow to prevent delivery of a hypoxic mixture

Movement of the shaft regulates the nitrous oxide slave control valve, which feeds the nitrous oxide flow control valve.

If the oxygen pressure > N2O , the nitrous oxide slave control valve opens wider to allow more nitrous oxide to flow.

As the N2O flow is increased manually, this pressure forces the shaft toward the oxygen chamber limiting the flow of N2O

whenever the oxygen supply pressure falls below a manufacturer-specified threshold (usually 30 psig (205 kPa)

at least a medium priority alarm shall be enunciated within 5 seconds

Limitations

Depend on pressure and not flow

Do not prevent anesthetic gas from flowing if there is no flow of oxygen

Crossovers in the pipeline system or a cylinder containing the wrong gas

Leaks downstream

Ritchie whistle

Present in older machines – ohmeda

When the oxygen pressure drops below 260 kpa( 38 psi ), oxygen failure whistle valve opens

Whistle sounds continuously, until oxygen pressure has fallen to approx 40.5 kpa ( 6 psi )

At 30 psi ( 200 kpa ) , it cuts off the supply of anesthetic gases to the patient

Criteria required for oxygen failure warning devices :

Alarm should be auditory(60 dB), for atleast 7 s duration measured at 1 m..

alarm gets activated when oxygen supply pressure falls to approx 200 kpa

Alarm linked to gas shut off device

Vaporizers - Interlocking Selectatecmechanism, low filling port..

Unidirectional [check ] valve

Back pressure relief valve [opens when the pressure exceeds 200 cm H2O]

Common gas outlet

Receives oxygen from the pipeline inlet or cylinder pressure regulator and directs a high unmetered flow directly to the common gas outlet

labeled “O2+.”

activated regardless of whether the master switch is turned ON or OFF.

flow between 35 and 75 L/minute delivered

The button is commonly recessed or placed in a collar to prevent accidental activation

activation does not increase or decrease the pressure at the vaporizer outlet > 10 kPa or increase the vaporoutput > 20%

Limitations

Accidental activation and internal leakage

The flush valve may stick in the ON position

Oxygen flush activation during inspiration -barotrauma

Its purpose is to prevent backflow into the vaporizer during positive-pressure ventilation, thereby minimizing the effects of intermittent fluctuations in downstream pressure on the concentration of inhaled anesthetic

APL valve open when pressure exceeds 60 cm H2O

Pressure in reservoir bag shouldn’t exceed 60 cm H2O.

Oxygen analyser

Canister – Dessicated absorbents without KOH or ba(OH)2 and with lesser amounts of NaOHproduce less heat and no fires

VENTILATORS – Pressure sensors to detect excessive airway pressure due to ventilator malfunction

Alternative oxygen control

Scavenging system

Wheels in anesthetic workstation is made of antistatic low friction rubber.

More accurate and corrected tidal volume through compliance and fresh gas compensation

Fresh gas decoupling prevent hyperinflation of the lung

Electronic PEEP

Electronic selection of ventilation parameters

Reduced external connections

It is the only machine safety device that evaluates the integrity of the low-pressure circuit

Oxygen concentration–sensing element must be exposed to room air for calibration to 21%.

Absolute criteria:

1. Lack of essential safety features such as:A. O2/N2O proportioning systemB. O2 failure safety device (‘‘fail--safe’’ system)C. O2 supply failure alarmD. vaporizer interlock deviceE. noninterchangeable, gas-specific pin indexed and

diameter-indexed safety systems for gas supplies.

1. Presence of unacceptable features such as: A. measured flow vaporizers (e.g., Copper Kettle)B. more than one flow control knob for a single gas

delivered to the common gas outletC. vaporizer with a dial such that the concentration

increases when the dial is turned clockwiseD. connections in the scavenging system that are the

same (15 or 22mm diameter) as in the breathing system.

2. Adequate maintenance no longer possible

1. Lack of certain safety features such asA. a manual/automatic bag/ventilator selector switchB. a fluted O2 flow-control knob that is larger than the

other gas flow-control knobsC. an O2 flush control that is protected from unintentional

activation D. an antidisconnection device at the common gas outletE. an airway pressure alarm.

2. Problems with maintenance.3. Potential for human error.4. Inability to meet practice needs such as

A. accepting vaporizers for newer agentsB. ability to deliver low fresh gas flows (FGFs)C. a ventilator that is not capable of safely ventilating the

lungs of the target patient population

THANK YOU