Anesthesia machine - week 2

Question 1

Give five examples of how a vaporizer can become hazardous.

Answer 1

wrong agent used to fill vaporizer

tipping it over

overfilling

contaminants in the vaporizing chamber

leaks

Question 2

How is agent delivery affected by changing altitudes?

Answer 2

decreased barometric pressure (high altitude) => increased delivery

increased barometric pressure (more than 1 atm) => decreased delivery

Question 3

What does a flow-compensated vaporizer compensate for?

Answer 3

temperature

(To prevent fluctuations in vaporizer output owing to temperature changes, compensatory mechanisms are built in. Typically the use of a valve that changes flow through a vaporizer—commonly a bimetallic strip or an expansion element. As ambient temperature goes up, the bimetallic strip/expansion element diverts more gas flow through the bypass, because the gas flowing through the vaporizing chamber will pick up more agent (due to the higher vapor pressures at higher temperatures)

Question 4

Which volatile agents are not delivered through variable bypass vaporizers?

Answer 4

Desflurane

(Desflurane’s high volatility and moderate potency preclude it’s use with contemporary variable-bypass vaporizers for two primary reasons: (1) at 20 degrees C, the vapor pressure of desflurane is near 1 ATMs (669 vs 760). (2) Traditional vaporizers lack an external heat source. Basically, the delivery of desflurane would be very unpredictable)

Question 5

Where are variable bypass vaporizers located? Why?

Answer 5

Between the flowmeters and the common gas outlet.

To prevent administration of elevated levels of inhalation agent to the client by secondary back-flow.

Question 6

How is a desflurane vaporizer (Tec - 6) different than other modern day vaporizers?

Answer 6

1) It has its own heater
2) No fresh gas flows through the desflourane sump. Instead, mixture occurs as gas is leaving the vaporizer
3) It cannot compensate for changes in altitude pressure

Question 7

Why does Desflurane need a special vaporizer?

Answer 7

Highly volatile

1/5 as potent as other VAA’s

The vaporization required for desflurane produces a cooling effect that would overwhelm the ability of conventional vaporizers to maintain a constant pressure.

A tremendously high fresh gas flow is required to dilute the carrier gas to clinically relevant concentrations

Question 8

It is possible to use Desflurane in a traditional flow over vaporizer?

Answer 8

Yes

(but you wouldn’t want to since the vaporizer for Desflurane is specifically designed to vaporize all of the VAA and make it more predictable and usable)

Question 9

What would happen to desflurane if it were used in a flow over vaporizer at a high altitude, like on Mt. Kilimanjaro?

Answer 9

you would have a shit-ton being delivered

i attempted to reason this out, if it’s wrong go ahead and change it

Question 10

What are the 6 components of the circle system?

Answer 10

Inspiratory and expiratory unidirectional valves

Inspiratory and expiratory corrugated tubes

Y-piece connector

Overflow or pop-off valve (APL)

Reservoir bag

Canister containing CO2 absorbent.

Question 11

What are 5 advantages to using the circle system?

Answer 11

Constant inspired concentrations

Conservation of heat and humidity

Minimal OR pollution

Useful for closed-system, low-flow, and semi-open configurations

Low resistance (less than the endotracheal tube; not as low as in nonrebreathing circuits)

Question 12

Which circle system component(s) generates the greatest resistance to breathing during spontaneous respiration?

Answer 12

1) valves in the inspiratory and expiratory limbs of the circuit
2) CO2 absorber

Question 13

In a circle system, where is the dead space located?

Answer 13

the Y-piece

(Mechanical dead space in a circuit constitutes the area where inspiratory and expiratory streams share the same space. This dead space ends where the inspiratory and expiratory gas streams split apart. Because of the two unidirectional valves in the circle system, dead space is limited to just the Y-piece)

Question 14

Why is re-breathing not a reasonable option with a semi-open system?

Answer 14

These systems do not utilize CO2 absorbent so if the fresh gas flow is set too low, the patient will rebreathe CO2 and potentially become hypercarbic/acidotic

Question 15

What are the two main features (or lack of features) of a semi-open anesthetic breathing system?

Answer 15

1) Absence of valves to direct gases flowing to & from patient
2) Absence of carbon dioxide neutralization

(Because semi-open systems have no clear separation of inspired and expired gases, high FGF is required to prevent rebreathing)

Question 16

What are some advantages of the semi-open breathing system?

Answer 16

lower cost

increased humidification

reduced heat loss

decreased release of anesthetic to the environment

Question 17

Why is the adjustable pressure limiting valve important in the semi closed system?

Answer 17

Waste anesthetic gases are vented from the anesthesia system through the APL valve or through the ventilator’s relief valve

Question 18

When does a closed anesthetic system exist?

Answer 18

Rarely

(The use of a closed circuit represents an extreme of anesthetic administration, one infrequently employed because few systems completely eliminate leakage of gas from the circuit.

Anesthetists often apply a deliberate leak of approximately 200 mL/min by sampling gases for oxygen, carbon dioxide, and anesthetic analyses.)

Question 19

Name four main advantages to using a closed breathing system.

Answer 19

cost reduction

increase in tracheal warmth & humidity

decrease in potential exposure of OR personnel to trace or waste gas

Question 20

What are two advantages of the open anesthetic breathing system?

Answer 20

light weight

easily sterilized

Question 21

What are two disadvantages of the open anesthetic breathing system?

Answer 21

unrecognized disconnection

kinking of fresh gas hose

Question 22

When using a T-piece, what flow rate must be used to avoid rebreathing?

Answer 22

A T-piece must have total flow greater than inspiratory flow in order to avoid rebreathing.

(exactly what that flow is, I don’t know)

Question 23

The Mapleson D system when modified is also known as what type of circuit?

Answer 23

Bain circuit

Question 24

What is the most commonly used system for delivering anesthetic gases and O2 to children and adults?

Answer 24

Circle system; gives most control over all variables

Question 25

What is the problem with placing the O2 sensor at the common gas outlet?

Answer 25

the common gas outlet has a mixture of volatile agent and gases

Question 26

Describe four actions you can take to test the low pressure system.

Answer 26

Check initial status of low pressure system

- Close flow control valves and turn vaporizer off
- Check fill level and tighten vaporizer filler caps

Perform leak check of machine low pressure system

- Verify that the machine master switch and flow control valves are OFF
- Attach “suction bulb” to common gas outlet
- Squeeze bulb repeatedly until fully collapsed
- Verify bulbs stays fully collapse for at least 10 seconds
- Open one vaporizer at a time and repeat collapsing and evaluation of the bulb
- Remove suction bulb and reconnect fresh gas hose

Turn on machine master switch

Test Flowmeters

- Adjust the flow of all gases through their full range and check for smooth operation of floats and undamaged flow tubes
- Attempt to create a hypoxic O2/N2O mixture and verify correct changes in flow and/or alarm

Question 27

What is the most abundant constituent in soda-lyme and baralyme?

Answer 27

CaOH2 (Calcium hydroxide)

Question 28

What is the name for the type of chemical reaction occurring in the carbon dioxide absorber?

Answer 28

Neutralization of Carbon Dioxide

or

Heat of Neutralization

Question 29

Why does the volume returned on an ascending bellows not reflect true tidal volume?

Answer 29

Ventilators impose a slight resistance at the end of exhalation, at which time the pressure in the bellows rises enough (2 to 4 cm H2O) to open the spill valve.

(during exhalation, the bellows expands upward)

Question 30

What is present inside and outside the bellows (gases/agents…)

Answer 30

outside - the driving gas (usually oxygen, but can be air, or a combo of both)

inside - everything the patient exhales (ie VAA, O2, N2O, CO2, etc)

Question 31

How does positive pressure ventilation affect pulmonary circulation? Cardiac Output?
Heart Rate? Blood pressure? Venous return?

Answer 31

Cardiac output is decreased due to a decreased venous return which can lead to a decrease in systemic blood pressure.

If heart rate is increased (as is should with a decrease in stretch of the baroreceptors) blood pressure may remain normal.

Question 32

The application of heat will increase or decrease saturated vapor pressure?

Answer 32

increase

because more molecules will enter the gas phase

Question 33

The application of cold will increase or decrease saturated vapor pressure?

Answer 33

decrease

fewer molecules enter the gas phase

Question 34

VAAs with a high vapor pressure that are placed in a vaporizer that is meant for a VAA with a low vapor pressure will produce what kind of output?

Answer 34

high output

high - low - high

Question 35

VAAs with a low vapor pressure that are placed in a vaporizer that is meant for a VAA with a high vapor pressure will produce what kind of output?

Answer 35

low output

low - high - low