Medical Gas Supply, Internal Components, Flowmeters, Vaporizers

exam #1

SPDD Model stands for?

supply, processing, delivery, disposal

supply in SPDD Model means?

how the medical gases enter the machine (cylinders & pipelines)

processing in SPDD Model means?

how the machine prepares the gases before it reaches the patient (inside the machine to the common gas outlet)

delivery in SPDD Model means?

how the prepared gases get to the patient (breathing circuit)

disposal in SPDD Model means?

how gases are removed from the OR (scavenger system)

what level pressure is the cylinder supply?

high pressure

Full O2 or Air cylinder enters machine at what pressure?

1900 psig

Full N20 cylinder enters machine at what pressure?

745 psig

what level pressure is the hospital pipeline supply?

intermediate pressure

hospital pipeline supply enters machine at approx. what pressure?

50-55 psig for all 3 medical gases

what does the Compressed Gas Association (CGA) do?

manufacture, filling, shipping, storing, and handling of cylinders. Also, colors, markings, labels, contents, and valve design of cylinders.

what does the Department of Transportation (DOT) do?

writes the standards regarding transport from the manufacturer, manufacturing, and testing specifications of compressed gases (like regulating amount of gas that may be contained in the cylinder)

general cylinder identifications?

specific color, specific markings, and labels to identify contents

what color is the oxygen (O2) cylinder?

kelly green

what color is the air cylinder?

bright yellow

what color is the nitrous oxide (N2O) cylinder?

dark royal blue

what color is a carbon dioxide (CO2) cylinder?

gray

what color is a helium cylinder?

brown

the markings on a cylinder are?

permanently engraved on cylinder and registered with Bureau of Explosives

the label (or sticker) on a cylinder tells you what (in general)?

identify the contents (name of gas), manufacturing info (name of company), and hazard class/level of the gas

green diamond hazard identification on cylinder means?

non-flammable gas

yellow diamond hazard identification on cylinder means?

oxidizer

red diamond hazard identification on cylinder means?

flammable gas

what apparatus does the anesthesia machine contain that allows the cylinder supply to be physically attached to the back of the machine?

hanger yoke

what 3 components are needed to physically hang the cylinder supply to the machine?

hanger yoke with valve, pin index safety system, T-handle

what was the pin index safety system (PISS) designed to do?

prevent misconnection of medical gas cylinders

what is the pin index safety system hole combination on the cylinder valve for O2?

2 & 5

what is the pin index safety system hole combination on the cylinder valve for N2O?

3 & 5

what is the pin index safety system hole combination on the cylinder valve for Air?

1 & 5

what is the cylinder valve and what does it contain?

conduit for the cylinder contents to reach the machine, contains a safety relief valve, and the pin index safety system

what does the safety relief valve in a cylinder valve do?

prevents rupture of cylinder under extreme conditions

what are the names of the 3 types of safety relief valves that exist?

fusible plug, frangible disc, spring loaded valve

characteristics of a fusible plug safety relief device?

made of metal alloy (a mixture of metals), melts at either low and/or high temperature range, and cannot be reset once triggered

characteristics of a frangible disc safety relief device?

made of copper, bursts when a certain high pressure is exceeded, and cannot be reset once triggered

characteristics of a spring loaded valve safety relief device?

increase in pressure in cylinder will force the spring open, the excess pressure will be released, and valve will close

how are the hanger yokes labeled?

color-coded and labeled for each medical gas

hanger yokes and cylinder valve PISS relationship and purpose?

each hanger yoke has 2 pin index posts that correspond to the pin index holes on the cylinder valve which prevents connection of incorrect cylinder

what is located between the gas outlet on the cylinder valve and the gas inlet on the anesthesia machine and what is it’s purpose?

gasket which creates a seal between the gas outlet on cylinder valve and gas inlet on machine

what device secures the cylinder to the hanger yoke?

T-handle

what takes the place of where a cylinder would normally go in a hanger yoke when there is no cylinder in place?

yoke plug

purpose of the cylinder check valves and how?

prevent reverse flow of gases (transfilling) and prevent flow of gas from one cylinder to another when a 2nd cylinder is turned on by responding to pressure

are cylinder check valves leak proof?

no

what is the ASTM standard allowable leak of cylinder check valves?

200 mL/minute

what is the function of a regulator?

degrades pressure

what is the only component on the machine that a non-anesthesia provider can use/operate?

auxiliary O2 flowmeter

how is particulate matter trapped in a hangar yoke?

a filter

what does the pipeline check valve do?

prevents transfilling of medical gas from cylinder supply into pipeline supply

how to safely handle cyclinders?

store upright in cool, dry, ventilated rooms, lay flat on ground when changing cylinder on machine, never oil the cylinder valve (wipe any oil off), place in free standing container when moving, MUST be stored in holder when transporting patient bed, and never leave standing alone

what must be done to a cylinder before it can be placed on the machine?

inspect for damage, confirm appropriate cylinder markings & labels to confirm contents, “crack” briefly prior to placement in hanger yoke to clear dust, oil, or debris from gas outlet

how do you “crack” a cylinder?

open with allen wrench

how is cylinder volume measured and what is unique about the volume of gas in a full cylinder?

measured in liters at standard temperature and pressure (STP) and volume in a full cylinder changes with the size of the cylinder and the type of gas (substance stored as different state of matter than gas will have different volume)

what 3 states of matter can a substance be stored as?

gas, gas mixture, liquid

what volume and pressure does a full E cylinder of compressed O2 contain?

660 L and 1900 psig

what volume and pressure does a full E cylinder of compressed N2O contain?

1590 L and 745 psig

what volume and pressure does a full E cylinder of compressed air contain?

625 L and 1900 psig

what is unique about how N2O is stored in a cylinder?

stored as compressed gas and liquid, volume is mostly liquid state (some gaseous), so when gaseous N2O leaves the cylinder during use, some of the liquid N2O changes to gas (aka mostly changes to gas only when leaving tank, stays liquid until then)

how is the manometer (gauge) reading different on a cylinder of N2O than O2 and Air?

as it changes from liquid to gas, the pressure indicated on gauge remains relatively constant until all of the liquid has been converted to gas

when will you see a decrease in the pressure gauge on a N2O cylinder?

when all the liquid is gone (all liquid has changed to gas)

once the pressure gauge on a N2O cylinder drops below ? psig, the cylinder contains approx. ? L N2O?

745 psig, 300 L

Example: What 2 things do we know if N2O cylinder pressure gauge reads 500 psig?

all the liquid is gone and there is less than 300 L of N2O left

what will happen to the manometer on an O2 or Air cylinder as volume decreases?

pressure will decrease proportionally to volume which will be reflected on the manometer (simply, lower psig=lower volume of gas remaining & visa versa)

how are volume and pressure related in general?

directly proportional (inc volume=inc pressure; dec volume=dec pressure)

full E cylinder pressure, volume, PISS Pin # of Air, O2, and N2O?

1900 psig, 625 L, Pin 1-5

1900 psig, 660 L, Pin 2-5

745 psig, 1590 L, Pin 3-5

what is the cylinder equation for O2 or Air?

(tank capacity L)/(full tank pressure psi)=(contents remaining L)/(gauge pressure psi)

how do you find minutes left before O2 or Air cylinder runs out of gas?

(contents remaining L)/(flow rate L/min)=mins left before tank expires

can then divide mins left/60=hours left before tank expires

what determines if a gas can be stored as a liquid or a gas?

its critical temperature

what is critical temperature?

temperature at which below a gas can be converted to a liquid if the critical pressure is applied (aka the temperature above which a substance cannot exist as a liquid no matter how much pressure is applied)

what does it mean if the critical temperature of a substance is close to room or ambient temperature?

the substance/gas can be stored as a liquid

what 2 gases can be stored as liquids?

N2O and CO2 (very cost effective)

what is a Bourdon Gauge and what does it indicate?

cylinder gauge that displays the pressure of gas in the cylinder in psig that indicates volume of gas remaining in the cylinder

what MUST occur of the high pressure cylinder gas and how is this accomplished?

must be regulated down to intermediate pressure via a first stage regulator

what does the first stage regulator do?

degrades (regulates down) pressure from high pressure to intermediate pressure

what pressure are the cylinder medical gases at before reaching the first stage regulator?

1900-2200 psig

the first stage regulator downgrades the pressure of the cylinder medical gas from _____ to _____?

1900-2200 psig to 45 psig

what does the ASTM require of gases supplied under high pressure?

each gas must have at least 1 pressure reducing regulator

what is the 1st true internal component that the anesthesia provider checks?

first stage regulator

how to confirm proper functioning of first stage regulator?

when an O2 flow of 2L/min is restored to 2L/min within 2 seconds after each operation of the O2 flush valve

is it possible to check functioning of first stage regulators for Air or N2O?

No, only first stage regulator for O2 can be checked

what safeguard exists for regulators?

safety relief valve that will vent excessive pressure out of the regulator (aka will keep internal pressure of 45 psig/intermediate pressure regulated if there is an issue with the machine)

from ____ to ____ is considered the high-pressure portion of the machine?

cylinder to first stage regulator

once the first stage regulator decreases cylinder flow to an intermediate pressure (45 psig) what will the anesthesia machine do?

preferentially seek flow from pipeline supply because it is entering at a slightly greater pressure (50-55 psig from pipeline)

does the first stage regulator and cylinder supply system bypass the on-off switch?

yes, does not require electricity. this is why cylinder supply is used in emergencies

what is another name for first stage regulators?

cylinder pressure regulator

what pressure portion does the pipeline supply enter the machine/begin?

intermediate

where does the pipeline supply get it’s gas supply from and what is unique about the bulk supply?

bulk supply located outside the hospital (near facility), stored in large cryogenic containers or cylinder manifolds which store the compressed medical gas in liquid form because it is able to overcome the critical temperature

what must occur to the liquid form of the gases, stored outside the hospital, BEFORE entering the hospital pipeline supply?

prior to entering pipeline system the liquid must be converted to vapor via vaporizer coils that warm the liquid which expands the liquid converting it to a gas, the gas flows through pressure regulators and check valves before reaching the piping system of the hospital

what 3 safeguards are in place from the bulk supply of gas to the hospital pipeline system?

actuating switches, shut off valves, high pressure relief valves

what pressure does the pipeline supply enter the hospital?

50-55 psig

how does the pipeline supply connect to the anesthesia machine?

diameter indexed safety system (DISS)

what does the DISS do?

helps prevent incorrect connections, fitting for each gas has a different diameter, and each fitting is internally keyed so the operator cannot make a loose connection with a slightly larger fitting one

hoses (pipeline pressure supply hoses) are color coded for each medical gas and are used to connect the anesthesia machine to the terminal units (where the pipeline supply enters the hospital)

one end of each hose will connect to the hospital medical has supply system (via columns or wall outlets) and the other end of each hose will connect to the anesthesia machine via DISS

what is the pipeline alarm panel, how many are there, and where are they located?

keeps hospital workers informed of the integrity of the gas supply. the OR has a main operating and emergency alarm panel in a central location

what should the pipeline supply alarm panel warn you of?

O2, N, N2O, & Air line pressure high/low

O2 supply low (reorder)

O2 emergency reserve in use

O2 emergency reserve low

N reserve supply in use

Vacuum line vacuum above/below normal

N2O reserve supply in use

what a 4 possible hazards from the pipeline supply?

fire, explosion, cross connection, cross contamination

If the pipeline supply is functioning properly what should the bourdon gauge be reading always?

50-55 psi

Example: if a problem occurs with pipeline pressure supply of O2, what would happen?

there would be an audible alarm from the machine, the bourdon gauge would fluctuate, and an alarm would be indicated at the front desk panel

what is the auxiliary oxygen flowmeter, what is needed for it to be operational, and does it bypass the on/off switch?

used to administer O2 during local, MAC, or regional anesthesia

operational as long as there is O2 pressure supplied to the machine

bypasses the on/off switch

what does it mean when something bypasses the on/off switch?

does not require electricity to function

Equation to calculate FiO2 for O2 + N2O

FiO2= # of liters of O2/total flows

Example: You are giving 1 L O2 and 2 L N2O. What is your FiO2?

1 L/3 L= 0.33 ×100= 33% FiO2