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Fall 2013 Anesthesia Concepts > Medical Gas Systems and Vaporizers > Flashcards

Medical Gas Systems and Vaporizers Flashcards

1
Q

What cyclinder size is stored on the back of the anesthesia machine?

A

E cylinders.

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2
Q

What is this a picture of, what does it do?

A

This is the flowmeter proportioning system. It prevents you from giving a hypoxic mixture by tying O2 to N20. So if you increase N20, O2 goes up proportionally as well.

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3
Q

Color coding of cylinders. What color is oxygen, nitrous, air, nitrogen and helium?

A

Oxygen=green, Nitrous Oxide=blue, Air=yellow, Nitrogen=Black (used for some ortho power tools), Helium=brown (used by ENT to give with O2 sometimes)

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4
Q

Oxygen E cylinders are full at _____psi and ________ liters.

A

2000-2200 psi and 625-700 liters

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5
Q

As O2 is used from the tank what happens to psi?

A

It falls in proportion.

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6
Q

Air cylinders are considered full at _________ psi and _________ liters.

A

1900-2000psi and 625 liters.

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7
Q

As air is used from the cylinder, what happens to the psi?

A

As air is used psi will fall in proportion.

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8
Q

What is unique about N2O in cylinders as opposed to air and O2?

A

Air and O2 are stored as compressed gas, but N2O is stored as liquid.

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9
Q

A full cylinder of N2O has ______ psi and holds______ liters.

A

745psi and 1590 liters.

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10
Q

As nitrous is used from the tank, what happens to the psi?

A

The psi will continue to read 745 until there is no liquid left in the tank. Only when all of the liquid is gone and only vapor is left will you see the pressure start to fall as the vapor is used up.

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11
Q

If the pressure gauge is not a good indicator, how can you tell how much nitrous you have in a tank?

A

By the weight of the tank.

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12
Q

How much does a full cylinder of N2O weigh?

A

20.7 lbs.

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13
Q

If the N2O tank is half full, how much will it weigh, and what is the psi on the gauge?

A

17.3 lbs and it will still read 745 psi

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14
Q

At a point where the liquid in the N2O tank is used up, how much does it weigh? what is the psi?

A

14.2 lbs and still 745 psi (psi will stay the same until the tank starts losing vapor with no liquid N2O to replenish it)

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15
Q

At the point where there is no liquid N2O remaining, how many liters of N2O do you have left (only vapor at this point)?

A

250L

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16
Q

When there is only 125L of N2O left in the tank and it is nearly empty, what does it weigh? and what is the psi?

A

it weighs 14.1 lbs and the psi will be down to 350.

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17
Q

The purity of medical gases is specified by which agency?

A

the United States Pharamcopoeia

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18
Q

Which agency enforces adherence to the purity of medical gases

A

The FDA

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19
Q

Which regulatory agency establishes the requirements for manufacturing, filling, qualification, transportation, storage, handling, maintenance, re-qualification, and disposition of medical gases?

A

DOT (department of transportation)

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20
Q

What are permanent markings on cylinders for?

A

The DOT requires specific markings with important data to be etched into each cylinder.

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21
Q

What are these?

A

Cylinder Markings. DOT regulations are etched into the cylinder. This is a requirement.

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22
Q

What are 4 things you will see etched into the cylinder?

A

The DOT specification number (the service pressure in psi), the identifying symbol of the manufacturer, and the serial number. You will also see the intial qualifying date and the inspector’s mark between the month and the year.

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23
Q

What does it mean if “SPUN” is etched into your cylinder?

A

It indicates that the end of the cylinder was closed by a spinning process.

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24
Q

If you see a + sign etched into your cylinder, what does it mean?

A

It means your cylinder is authorized for charging 10% in excess of the marked service pressure.

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25
Q

What does it mean if you see a ‘star’ etched into your cylinder?

A

It means the cylinder may be retested every 10 years instead of the typical 5 years.

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26
Q

What is the standard life of a cylinder before it needs to be re-tested.

A

A cylinder needs to be re-tested every 5 years, unless marked with a star, then it can go for 10 years.

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27
Q

What is a cylinder label?

A

Each cylinder must have a label or decal on the side or on the shoulder, but it may not cover any permanant markings.

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28
Q

What sort of information is on the cylinder label?

A

It shows the basic Compressed Gas Association (CGA) marking. There is also a diamond shaped figure that denotes the hazard class of the contained gas. ex. (NONFLAMMABLE). The name of the gas is also listed. and the word Caution: followed by a list of hazards and measures to be taken with that specific gas.

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29
Q

What is this?

A

Cylinder label

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30
Q

What is this?

A

A cylinder tag. When it is first opened the FULL portion of the tag should be ripped off, and likewise, once it is empty, the in use portion should be ripped off.

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31
Q

How many pin positions are there in the PISS?

A

7 positions. All of the pins are the same size, 4mm diameter and 6mm long except for pin 7 which is slightly thicker.

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32
Q

Label the pin positions in the PISS.

A
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33
Q

What is DISS?

A

The diameter index safety system. It provides non-interchangable connections for medical gas lines. Only properly mated parts will fit together and allow the threads to engage. This is required for every anesthesia machine.

34
Q

A DISS connection consists of what 3 parts?

A

a body, a nipple, and a nut.

35
Q

What is the PISS pin number for O2?

A

2, 5

36
Q

What is the PISS pin number for N2O?

A

3, 5

37
Q

What is the PISS pin number for air?

A

1, 5

38
Q

There are some basic rules for handling cylinders, mostly to prevent fires and prevent them from becoming missiles. All of them are for patient safety. What are the 7 rules.

A
  1. never stand cylinder upright without a support. 2. Never leave empty cylinders on the machine. 3.Never leave plastic tape on the port while installing the cylinder. 4. Never rely on the cylinder’s color for identification of its contents. 5. Never oil valves 6. Before any fitting is applied to the cylinder valve, particles of dust, metal shavings, and other foreign matter should be cleared from the outlet by slowly and briefly “cracking” the valve away from you. 7.The valve should always be fully open when a cylinder is in use. Marginal opening can result in failure to deliver adequate gas.
39
Q

Why do we want to briefly “crack” the tank as we open it?

A

Oil and dust particles that may be on the cylinder opening could catch fire if the pressure changes suddenly. As the pressure changes, heat is released and coud cause a fire. Allowing a tank to crack open blows dust and oil off the surface and minimizes the sudden change in temperature.

40
Q

What is vaporization?

A

Conversion of a liquid to a gas

41
Q

Vaporization of anesthetic gas is dependent on what 3 things?

A
  1. Vapor pressure 2. Temperature 3. Amount of carrier gas used.
42
Q

Describe vapor pressure, what causes it?

A

In a closed container a volatile agent is distributed between the liquid and gas phases. Gas molecules bombard the surface of the liquid and wall of the container creating a vapor pressure.

43
Q

As temperature increases more molecules enter the vapor phase and hence ______ _______ increases.

A

vapor pressure

44
Q

What is the vapor pressure of Sevoflurane at 20 degrees C (room temp)?

A

160 mm Hg

45
Q

What is the vapor pressure of Enflurane at 20 degrees C (room temp)?

A

172 mm Hg

46
Q

What is the vapor pressure of Isoflurane at 20 degrees C (room temp)?

A

240 mm Hg

47
Q

What is the vapor pressure of Halothane at 20 degrees C (room temp)?

A

244 mm Hg

48
Q

What is the vapor pressure of Desflurane at 20 degrees C (room temp)?

A

669 mm Hg

49
Q

Increasing temperature will do what to vapor pressure?

A

Increases: more molecules enter the vapor phase.

50
Q

Decreasing the temperature will do what to vapor pressure?

A

Decrease vapor pressure and cause a shift toward the liquid phase.

51
Q

Passing a carrier gas over the liquid shifts the equilibrium toward the:__________.

A

vapor phase.

52
Q

What is the latent heat of vaporization?

A

The number of calories required to change 1 gram of liquid into a vapor without a temperature change. (1 gram = 1mL)

53
Q

The energy for vaporization comes from:________ or ________.

A

The liquid itself or an outside source.

54
Q

What is specific heat?

A

The number of calories required to increase the temperature of 1 gram of a substance by one degree C. The substance can be a liquid, solid, or a gas.

55
Q

What is the significance of specific heat in anesthesia?

A

The specific heat of an anesthetic agent indicates how much heat must be added to maintain a constant rate of vaporization.

56
Q

What is thermal conductivity?

A

A measure of the speed with which heat flows through a substance.

57
Q

The higher the thermal conductivity, the (better/worse) the substance conducts heat.

A

better

58
Q

If you increase altitude, what happens to barometric pressure?

A

It goes down.

59
Q

If you decrease altitude, what happens to barometric pressure?

A

It goes up.

60
Q

The boiling point occurs when __________ equals barometric pressure.

A

Vapor pressure. So the closer to the vapor pressure to the surrounding atmospheric pressure, the more likely the liquid will pop off into gas form.

61
Q

If temp goes up, vaporization goes ___.

A

up

62
Q

If temp goes down, vaporization goes ____.

A

down

63
Q

What would happen to the amount of vaporized anesthetic if you did not compensate for atmospheric pressure and moved your machine to Denver.

A

The increased altitude and decreased barometric pressure of Denver would cause your anesthetic agent to vaporize more easily. You could accidentally give too much anesthetic if your machine was not calibrated to the new atm.

64
Q

Are vaporizers agent specific?

A

Yes

65
Q

Are vaporizers temperature compensated?

A

Yes

66
Q

What is the basic function of a variable bypass vaporizer?

A

A portion of the gas flow will pass into the vaporizing chamber where it will become saturated with vapor. The vapor-laden portion wil then rejoin the gas flow for dilution to deliverable concentrations.

67
Q

The variable bypass vaporizer has a temperature compensating valve. How does that work?

A

As the temperature inside the vaporizer increases (and more gas is vaporized) the bimetallic strip will bend to the right, causing more gas to go straight through bypassing the baffle system. As the temperature goes down the metal bends closing off the bypass gas and sending more into the baffle system to pick up anesthetic.

68
Q

In the variable bypass vaporizer, the the temperature inside the vaporizer is colder, what happens?

A

Less gas will vaporize if it’s colder. So, the bimetallic strip closes off the path of air and directs more of it into the baffle system to pick up anesthetic.

69
Q

In the variable bypass vaporizer, if the temperature inside is warm, what happens to air flow?

A

If it is warmer, then more gas will turn to vapor and less carrier gas is needed to pick up the anesthetic, so the bimetallic strip will bend and prevent too much gas from entering the baffle system and picking up anesthetic.

70
Q

How do you calculate the % of an anesthetic gas? For example, Isoflurane?

A

Isoflurane has a vapor pressure of 240mmHg, so if we are at 760 mm Hg, so as a percentage 240 is 33% of 760. So the answer is about 33%.

71
Q

What is the % of isoflurane (vapor pressure 240 mmHg) in Honduras where the atmospheric pressure is 500 mm Hg.

A

About 50%.

72
Q

What is a TEC 6 vaporizer?

A

It’s a vaporizer made specifically for Desflurane. Desflurane has a very high vapor pressure. The TEC 6 vaporizer has a heating element that is used, not to heat the anesthetic but to increase the atm in the machine to 2 atm.

73
Q

What is the formula for calculating the dialed amount of desflurane you will need, (remembering that the vaporizer is altered to 2 atm)?

A

Required dial setting = normal dial setting % x 760mmHg divided by ambient pressure in mmHg.

74
Q

What is a copper kettle?

A

It’s an out of circuit, non-agent specific, measured flow, bubble through vaporizer. it is not likely to be seen in the USA.

75
Q

How does the copper kettle work?

A

It has a dedicated flowmeter to provide measured flow. The gas comes up through a central tube inside the vaporizer to the Loving cup. From there gas is directed down toward the liquid (bubble through). THe highlyconcentrated vapor then exits the vaporizer and is diluted by fresh gas flow.

76
Q

How do you calculate vapor output in the copper kettle?

A

Vapor Output= Carrier gas lpm x vapor pressure Divided by Barometric pressure - Vapor Pressure.

77
Q

How do you calculate anesthetic concentration in the copper kettle?

A

anesthetic concentration = vapor output (mL/min) divided by Total gas flow in mL/ min

78
Q

How do Aladdin cassettes work?

A

Thye are electronically controlled vaporizers.

79
Q

What are some potential vaporizer hazards?

A

Wrong agent in the vaporizer, contamination, tipping, overfilling, simultaneous administration of more than one vapor, leaks, pumping effect.

80
Q

If you put an anesthetic in the vaporizer that has a higher vapor pressure than the one you intended, you will end up delivering a __________ (higher/ lower) concentration of anesthetic.

A

Higher

81
Q

If you accidentally put an anesthetic in the vaporizer that has lower vapor pressure than you intended, you will end up given a (lower/higher)_______ concentration of anesthetic than you wanted.

A

Lower

82
Q

What is meant by pumping effect?

A

If there is an ovewhelming demand on the hospital oxygen pipeline at one moment, like in the OR in the morning when they are all getting started up at once, you could get a drop in O2 pressure in the system.

Fall 2013 Anesthesia Concepts (8 decks)

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