Anesthetic Equipment - Study Questions

Question 1

List, in sequence, the 7 major parts of a vaporizer out of breathing circuit anesthesia machine

Answer 1

• source of medical gases
• pressure reducing regulator
• variable flowmeter for each medical gas
• vaporizer
• O2 flush
• patient breathing circuit
• waste gas scavenging interface

Question 2

Rate each of the following in terms of relative risk of causing spontaneous abortion (high or low)

Answer 2

• waste anesthetic gas exposure (iso,sevo): low
• handholding animals for radiographs: high
• exposure to zoonotic dz/parasites: high
• excessive smoking and/or alcohol consumption during pregnancy: high
• recreational use of NO during pregnancy: high
• exposure to chemotherapy agents: high

Question 3

T/F: exposure to trace amounts of waste anesthetic gases represents a significant risk to the pregnant veterinarian

Answer 3

False

Question 4

What are the gas flow requirements for Mapleson-type non-rebreathing circuits based upon?

Answer 4

Patient minute volume

Question 5

How is CO2 removed in non-rebreathing circuits?

Answer 5

High fresh gas flows are required to blow expired CO2 away during expiatory pause
- rates 1.5-3 times the minute volume

Question 6

What is the minimum oxygen flow requirement for circle rebreathing circuits based upon?

Answer 6

Metabolic O2

• supply oxygen from the flowmeter at a rate equal to or greater than the metabolic O2 use rate
• O2 flow rate lower than metabolic use rate may lead to hypoxia

Question 7

How is carbon dioxide removed in rebreathing circuits?

Answer 7

Soda Sorb

Question 8

How can you decrease the time constant for an anesthetic circuit?

Answer 8

Increase the inflow rate at the same time you change the vaporizer setting
- increasing vaporizer output alone will NOT decrease time constant!!

Question 9

What is the purpose of the flowmeter?

Answer 9

Measures and indicates the flow rate of carrier gas to the vaporizer and other downstream components of the anesthesia machine
- also delivers gases when the vaporizer is off

Question 10

Your patient seems to be waking up 10 minutes after being connected to the gas anesthesia machine. Make a list of 6 possible reasons for this

Answer 10

• anesthetic machine or breathing circuit leaks
• endotracheal cut off leak
• use of the oxygen flush valve to fill anesthetic circuit
• insufficient fresh gas flow rate
• CO2 rebreathing
• vaporizer off, not connected, empty
• stuck or malfunctioning one-way valves in circle rebreathing circuit

Question 11

Why would you use the oxygen flush valve? Describe an alternative method to achieve the same end?

Answer 11

Used to pressure check the anesthesia machine and breathing circuit

• do not use while patient is connected!
• alternative: use flowmeter when vaporizer is off

Question 12

What is the device that changes a high cylinder gas pressure to a constant lower working gas pressure?

Answer 12

Regulator

Question 13

What factors would influence your choice between using a NRB circuit and a rebreathing circuit for any given patient?

Answer 13

Patient size, cost of inhalants, patient body temperature

• < 5 kg: NRB
• 5-8 kg: pediatric rebreathing
• > 8 kg: adult rebreathing

Question 14

Why does the temperature of the anesthetic liquid fall as it is vaporized? Why is this important to vaporizer function?

Answer 14

Molecules of vapor push against container walls, creating vapor pressure

• saturated vapor pressure at 20 degrees
• vapor pressure changes with changing temp
• temp of vaporizer changes more slowly

Question 15

The gas flow in a Mapleson D-type circuit connected to a spontaneously breathing 3 kg cat is inadvertently decreased from one L/min to 100 ml/min. How will this effect the functioning of the circuit?

Answer 15

Impair CO2 removal and affect vaporizer inhalant output

Question 16

Your reservoir bag is continually becoming empty (every minute) and your partner suggests repeated filling with the oxygen flush. Do you foresee any potential problems with this?

Answer 16

Will dilute inhalant concentration and patient will become too light

Question 17

Describe a method to check out an anesthetic machine prior to use

Answer 17

• turn on cylinder, evaluate high, intermediate, low pressure areas of anesthetic machine for leaks
• check patient breathing circuit for leaks
• occlude patient breathing circuit connection, close pop-off APL valve
• inflate circuit with O2, use flush valve
• observe for leaks, circuit should hold pressure with <250 ml/min leak rate
• open circuit outflow valve and note that scavenger interface is not obstructed

Question 18

The CO2 absorber in a circle system is filled with what material?

Answer 18

Soda lime

Question 19

You wander into a room to pick out an anesthesia machine for a case. The absorbent granules are white, the same color as they were when the canister was first filled 3 months ago. Are the granules still good?

Answer 19

Probably not.

• only last for 6 hours
• need to check consistency (if hard, needs to be replaced)

Question 20

Your patient is light, so you turn up the vaporizer. What else should you do to speed the rate of change in anesthetic vapor concentration?

Answer 20

You need to increase the carrier gas inflow rate