The Anesthesia Machine Flashcards by Kate Guiremand

why should you not deliver anesthestic gas in air (21% O2)

would lead to hypoxemia due to hypoventilationa and V/Q mismatch by anesthetic itself

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minimal acceptible range of O2

30-35% O2 (FiO2= 0.30-0.35)

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what is the metabolic requirement for oxygen?

5-10 mL/kg/min

this would be the minimun O2 flow required

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what are other medical gases

nitrous oxide

medical air

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types of oxygen sources

cylinders

liquid (cryogenic oxygen)

oxygen concentrator

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E- cylinders

usually single, attached directly to anesthesia machine via yoke

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H-cylinders

often in banks, supply central O2

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T/F clyniders are color coded

True

oxygen= green

nitrous oxide (N2O) = blue

medical air = yellow

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T/F unsecured tanks may explode if dropped or falls over and can become a projectile

True!!

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what can you do to avoid fire with tanks

clean oils from hands and tank

open cylinder valves slowly

open & close walve briefly before attaching to machine to remove dust from connecting port

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T/F pressure in the breathing system is meansure in psi

False

measured in cmH2O, the cylinder is measured in psi

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what are pressure gauges used to measure

cylinder pressures

pipeline pressures

anesthetic machine working pressures

pressure within the breathing system

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what part of the system is in low pressure

between flowmeter output and common gas outlet

breathing system (= pressre in patient’s lungs)

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what is the capacity of an E-cylinder

660L (know this!!)

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both E and H cylinders are filled to:

2200 psi (know this!!)

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how can you calculate remaining O2 in the tank

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how can you gifure out how many minutes of O2 are left

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T/F N20 exisits in both a gaseous an dliquid form in the tank

True

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T/F it is NOT possible to calculate amount of N2O gas remaining based on pressure

True

gauge only reads the gas pressure

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what are some of the safety systems in place

color-coded tanks

labelling

diameter index safety system

pin index safety system

quick connectors

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what is the diameter index safety system

non-interchangeable, gas specific threaded connection system

used universally by all equipment and cylinder manufacturers

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what is the pin index safety system

gas-specific pin patterns that only allow connections bewteen the appropriate cylinder yokes and e tanks

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characteristics of quick connectors

manufacturer-specific

facilitate rapid connecting and disconnecting of gas hoses

useful for multipurpose work areas

what does the regulator/pressure-reducing valve

decreases tank pressure to a safe working pressure (≈50 psi) which is supplied to flowmeter

prevents pressure fluctuations as the tank empties

flowmeter

controls rate of gas flow through the vaporizer (L/min) gas enters at bottom at 50 psi and exits the top at 15 psi

the single/double taper flowmeter is more accurate at lower gas flows

**Double-taper**

T/F flowmeters are calibrated for 760 mmHg and 20ºC

**True**

where do you read the flow?

middle of the ball top of the bobbin

T/F flowmeters are gas-specific

**True** O2 flowmeter is NOT accurate if used for N2O or medical air

if there are multiple flowmeters where would the O2 be located

the far right (downstream of all other gases) prevent delivery of a hypoxic gas mixture

in a mixed gas set up the N2O is set to 6L and the O2 set to 1L, is there sufficient O2 flow going the patient

**No!!!** 1L O2 + 6L N2O 02 = 1/7 = 14% (minimum is 35%) **This would be a hypoxic mixture = fatal**

T/F the quick flush bypasses the vaporizer and delivers O2 with no anesthetic gas

**True** dilutes gas in the circuit

when should the quick flush be used

quickly decrease anesthic gas % in the circuit (emergency, recovery) **Remember:** disconnect patient from cicuit before using quick flush→ can resulti n dangerous increases in breathing circuit pressures

what is a possible complication of the quick flush

**pneumothorax** small circuit, high pressure, small patient

what do anesthetic vaporizers do

change liquid anesthetic into vapor deliver selected % of anesthetic vapor to fresh (common) gas outlet

vapor

gasesous state of substance that is liquid at ambient temp and pressure halothane, isoflurane, sevoflurane, desflurane

gas

exists in gaseous state at ambent T and P N20, Xenon

vapor pressure

pressure exerted by vapor molecules when liquid and vapor phases are in equilibrium

T/F vapor pressure is dependent on temperature

**True** increases with increases temperature, inversely related to boiling point

saturated vapor pressue

maximum administration percentage vapor pressure/barometric pressure

characteristics of modern vaporizers

agent-specific concentration-calibrated variable-bypass flow-over out-of circuit high resistance compensated for temp, flow and back-pressure

variable-bypass system

fresh gas flows over a reservoir of liquid anesthetic and mixes wit carrier gas

vaporizers out of circuit (VOC)

carrier gas is from flowmeter anesthetic % is known - percision vaporizer

vaporizers in circuit (VIC)

not currently recommended cannot produce known anesthetic gas % not temperature compensated non-precision

modern vaporizers compensate for:

temperature bewteen 15-35º C flow rate between 0.5 and 10 L/min back pressure associated with positve pressure ventilation and ise of flush valve

how is temperature compensation achieved

using materials that are efficient heat conductors mechanical thermocompensation systems: has thermal element mode of heat sensitive metal that reliably expands and contracts based on temp

how is flow rate compensation achieved by

saturation of gas moving through vaporizing chamber use of wicks, baffles, and spiral tracks that facilitate vaporization

back pressure

can occur during positive pressure ventilation or use of the flush valve may increase vaporizer output of compensation mechanisms not present vaporizers have mechanism to prevent

how are vaporizers filled

using screw-cap port or agent-specific keyed filler port

characteristics of vaporizers

require no external power (except desflurane) routine maintenance is required and must be performed by a qualified technician mounted on a "back bar" on the machine **cannot be tipped**-must be emptied before transporting

what can happen if vaporizer is filled with wrong agent

depends on vapor pressure and petency of each agent iso in sevo vaporizer could produce a leathal concentration

what should you do if you put the wrong agent on the vaporizer

drain and run 1 L/min O2 until completely dry

what would happen if vaporizer was tipped

anesthetic may enter the bypass channel and deliver a high concentration run 1 L/min O2 through machine with vaporizer off to fix

what is the common gas out

where gas exits the vaporizer

where is the common gas outlet connected

by a hose to the fresh gas inlet - must be connected so fresh gas flows to the breathing circuit connects to either rebreathing or non-rebreathing system