Anesthesia Machine Flashcards by Adrie McFarland

What is the main purpose of the oxygen pressure failure device?

To monitor for and protect against low oxygen pressure in the anesthesia machine

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What kinds of things would set off the O2 pressure failure device?

O2 tank was depleted, drop in pipeline pressure, oxygen hose disconnect

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The oxygen pressure failure device resides in which portion of the machine? (low, int, or high pressure)?

Intermediate

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What are the 2 components of the oxygen pressure failure device?

Threshold alarm that sounds when the pipeline pressure falls below 28-30 psi
Device that reduces or stops the flow of N2O when the pressure in the O2 pipeline falls below 20 psi

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What are the 2 types of oxygen pressure failure devices?

GE Datex Ohmeda
Drager

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What are the differences between the 2 oxygen pressure failure devices?

GE Datex-Ohmeda will completely stop N2O flow when O2 pipeline pressure gets below 20 psi. “All or nothing” response.

Drager will cause a proportional decrease in N2O as O2 pipeline pressure decreases but is only completely stopped with O2 pressure is extremely low.

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How can you tell the O2 pressure failure device is working?

Turn both the O2 and N2O flow meters on.

Make sure O2 tank is closed.

Disconnect O2 pipeline and should see N2O flowmeter drop just before the O2 flow stops.

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In what 2 scenarios would the O2 pressure failsafe device not necessarily work to notify you that a hypoxic mixture is present?

O2 pipeline cross over
Flowmeter leak- bc it is upstream of the flowmeters, so it wont detect a flowmeter crack (where gas can escape)

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What does the SPDD model stand for? What does it describe?

Supply
Processing
Delivery
Disposal

Architecture of the anesthesia machine

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What does supply describe as far as the SPDD model goes? What is the location?

How the gas enters the anesthesia machine

Pipeline to the back of the anesthesia machine

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What does processing describe as far as the SPDD model goes? What is the location?

How the machine prepares the gases before they are delivered to the patient

Inside the machine up to the common gas outlet

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What does delivery describe as far as the SPDD model goes? What is the location?

How the prepared gases are brought to the patient

Breathing circuit

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What does disposal describe as far as the SPDD model goes? What is the location?

How the gases are removed from the breathing circuit

Scavenging system

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Purpose of Pin Index Safety System

Prevent incorrect connections of the GAS CYLINDERS

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Why is gas preferentially pulled from the O2 pipeline even if the O2 tank is left open?

Because when O2 cylinder pressure of 1,900 psi drops to 45 when it enters the intermediate system. Which is lower than the O2 pipeline pressure

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What is the problem with having more than one washer between the hanger yoke assembly and the stem of the tank?

May allow for the PISS to be bypassed.. do not do it

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What is the PISS configuration for O2?

2,5

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What is the PISS configuration for air?

1,5

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q
What is the PISS configuration for N2O?

3,5

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What is the main purpose of the Diameter Index Safety System

To prevent incorrect connection of GAS HOSES

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Pipeline pressures are what psi?

50 psi

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Oxygen total L in tank

660 L

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Air total L in tank

625 L

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N2O total L in tank

1,590 L

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Pressure in O2 tank

1900 psi

Pressure in air tank

1900 psi

Pressure in N2O tank

745 psi

How much does full N2O tank weigh

20.7 lb

How much does empty N2O tank weigh

14.1 lb

What color are O2, air, and N2O tanks usually?

O2: green Air: yellow N2O: blue

In what form does oxygen exist at room temp?

gas

In what form does N2O exist at room temp?

liquid (unless it is almost empty) The pressure of the gas above the liquid remains constant (745) regardless of how much liquid remains in the tank. The pressure only decreases when all the liquid is consumed.

When does the pressure start to decrease from 745 psi in the N2O tank?

It is usually constant until the cylinder is more than 3/4 empty at which point all of the liquid has been consumed. Approx 136 L remains in the tank.

When is it wise to change the N2O tank (at what psi) and why?

When it drops below 745 psi because that means all of the liquid in the tank has been consumed

What is the only reliable method to determine how much N2O remains in the tank?

WEIGH IT!

Max volume of CO2 tank?

1,590 L (Same as N2O)

Service pressure for N2O tank

838 psi

Damage to what part of the tank can cause it to take off like a mistle?

Cylinder valve!!

What should you do if you open a cylinder and hear a "hissing" sound (i.e. a leak)?

First step: tighten the connection Second step if that doesn't work: replace the washer between the cylinder and the hanger yoke assembly Third step if that doesn't work: use a different cylinder

What kind of O2 tank do you need for MRI?

MRI safe!

The fire triad consists of:

Oxidizer, a fuel, an igniter

What are examples of oxidizers?

Oxygen N2O

What is in place in a tank for safety measures if there is a fire? What does it do?

Safety relief device Opens if there is a fire, allowing the cylinder to empty its contents in a slow and controlled way.

3 examples of fire safety relief devices on a tank:

1. A fusible plug that melts at elevated temps. Made from Wood's metal: bismuth, lead, tin, and cadmium *BLT w/cheese 2. Valve that opens at elevated pressures 3. A frangible disk that ruptures under pressure

What is the process of cracking a cylinder open and why is it used?

Slowly opening it when it is ready to be used to flush the valve outlet clean of dust and debris to prevent it from starting a fire

What standards does the US (DOT- Dept of Transportation) set?

Sets the standards for compressed gas cylinders

Who sets the standards for acceptable occupational exposure to volatile anesthetics

OSHA

Food and Drug administration (FDA) sets standards for what?

FDA anesthesia machine pre-use checkout procedures

American society for testing and materials sets standards for:

required components of the anesthesia machine Standards document is called the ASTM F1850

How often does a cylinder have to be tested?

5 years

What is done to test cylinders every 5 years?

Subjecting the cylinder to 1.66 x its service pressure

The US DOT requires the following information on the cylinder label:

1. Government agency 2. Type of metal used to construct the cylinder 3. Max filling pressure (psi) 4. Serial number 5. Manufacturer 6. Owner 7. Date of the last inspection

What is the oxygen pressure failure device?

Shuts off and or proportionally reduces N2O flow if O2 pressure drops below 20 psi

What is the hypoxia prevention safety device?

Prevents you from setting a hypoxic mixture with the flow control valves. Limits N2O flow to 3 x O2 flow (Nitrous max of about 75%)

The hypoxia prevention safety device prevents you from ever delivering FiO2 less than what %?

25%

There are 2 types of proportioning devices, what are they?

Link 25 system (GE Datex-Ohmeda): O2 and N2O are mechanically linked by a CHAIN. If either gas is adjusted in a way that would create a hypoxic mixture, the other gas would be automatically adjusted by the chain to correct the problem (go up on O2 or down on N2O) Oxyegn Ratio Monitor controller (Drager): maintains a 3:1 ratio, the supply pressure is manipulated by the machine if the mixture gets hypoxic and decreases N2O

What are some scenarios where a proportioning device cant prevent a hypoxic mixture?

1 oxyegn pipeline crossover 2 leaks distal to the flowmeter valves 3 administration of a third gas (helium) 4 defective mechanic or pneumatic components

What is a Thorpe tube

Traditional flowmeter that controls and measures the fresh gas flow that travels towards the vaporizers and common gas outlet

How many types of floats are there for flow meters?

Flow measurements on a flow meter are taken from the widest or narrowest part of the float?

Widest

Which floats are read from the top of the float?

Skirted, pump bob, nonrotating

Which float has flow measurement taken at the middle part of the float?

Ball

What is annular space on the flow meter design?

Area b/w the float and the sidewall of the flowmeter

What is internal diameter on the flow meter design?

the flowmeter is narrowest at the base an widens along its ascent

What kind of flow is represented by a Re number of < 2,000, 2,000-4,000, >4,000

< 2k: laminar 2k-4k: transitional >4k: turbulent

In the context of Thorpe tube flow dynamics, a low FGF will favor a _ flow pattern. At higher GFG, the annular space creates _ flow

laminar turbulent

What happens if the flowmeter glass is broken?

There will be a leak allowing oxygen to escape and creating a potentially hypoxic mixture

Where should O2 flow meter be positioned? Right, left, middle? Why?

Right. Because if there is a leak in any of the gases proximal to that, it should not reduce the FiO2 delivered to the patient.

Simple way to remember and calculate FiO2 when using a Nasal Cannula

Add 4% for each liter of oxygen administered (0=21%) up to a max of 44% for 6 L

Modern anesthesia machines seperate FGF from Vt. Older machines do not what does that mean?

Moderna anesthesia machines: the Vt set is the Vt the patient gets, regardless of the FGF set.