Anesthetic Equipment

Question 1

what is held in the gas cylinders? what do the gasses do?

Answer 1

 Oxygen
* Carrier gas
* Flow should meet metabolic requirements
 Nitrous oxide
* Carrier gas in combination with oxygen
* MAC sparing effect
* Not used as often anymore
* Not used at OVC

Question 2

what percent oxygen is in the gas cylinder? what sizes? what pressure?

Answer 2

 >99.5% O2
 Sizes:
* E, H
 Pressure: full tank has 2200 psi (pounds per square inch) * High pressure system

Question 3

have can we find out the number of liters in a small (E) and large (H) oxygen tank?

Answer 3

 E- small tank attached to anesthetic machine
* psi X 0.3 = liters of O2 in tank- 660 L

 H- Large tank
* psi X 3 = liters of O2 in tank- 6600 L

Question 4

what is the purpose of grouping oxygen tanks for H tanks?

Answer 4

 H- larger tank
* They can be grouped to maintain constant supply and avoid frequent changing of regulators

Question 5

conversion of liquid oxygen to gas oxygen?

Answer 5

 1 L of liquid oxygen = 860 L of gas

Question 6

what temp should we store liquid oxygen at?

Answer 6

 Stored at -150 to – 175 °C
* Critical temperature of oxygen is -119°C
* If below this temperature, the gas is known as a vapor and can be compressed to a liquid

Question 7

Yoke index for E-tanks

Answer 7

• Positions
  – Oxygen 2 & 5
  – N2O 3 & 5

Question 8

Pressure regulator does what?

Answer 8

Reduces high pressure of tank (up to 2200 psi) supply to a lower pressure of 50 psi
* Establishes intermediate pressure system

Question 9

what does the oxygen flowmeter do? what is the pressure in the flowmeter?

Answer 9

 Allows delivery of precise amount of oxygen (mL/min or L/min) to meet patient requirements and as carrier gas for inhalational anesthetic
 Pressure through flow meter is 15 psi
* Low pressure system
 Bobbin versus ball
* Bobbin- read the top
* Ball- read the middle

Question 10

Oxygen requirements and fresh gas flow (FGF) - min oxygen reqs? what is it needed for?

Answer 10

 Minimum oxygen requirements (VO2)
* 5-10 mL/kg/min
* Necessary to maintain aerobic metabolism

Question 11

what does a rebreathing system allow for? what are the types?

Answer 11

• One that allows CO2 to be extracted by the anesthetic circuit system used
• Circle system, F-circuit

Question 12

what does a non-rebreathing system allow for? what are the types?

Answer 12

• One that uses FGF to flush the CO2 out of the anesthetic system
  -bain system**
  -also lack system, magill

Question 13

what is fresh gas flow through the rebreathing system?

Answer 13

• 10-100 mL/kg/min
• Low flow for closed system
  – Pop-off valve closed
  – Delivers minimum oxygen requirements (5-10 mL/kg/min)
• Higher flows for semi-closed systems
  – Pop-off valve open
  – 50-100 mL/kg/min

Question 14

what is fresh gas flow for a non-rebreathing system?

Answer 14

• 130-200 mL/kg/min

Question 15

what does the vapourizer do?

Answer 15

 Converts the liquid anesthetic to vapor (gas)
 Allows for precise conversion and delivery of desired concentration, mixed with carrier gas (O2)
 Important to know MAC values so that the desired concentration is dialed

Question 16

what is the purpose of vaporizer percision, variable by-pass, and automatic temp. ompensation?

Answer 16

 Precision- output is accurate at dialed concentration
 Variable by-pass- FGF splits so that part of the flow goes into the chamber where the liquid anesthetic is vaporized, part of the flow bypasses the chamber
 Automatic temperature compensation- Accurate output despite fluctuations in room temperature

Question 17

what is the purpose of automatic flow commpensation for the vaporizer?

Answer 17

 Automatic flow compensation- Accurate output despite of FGF (300 mL/min – 10 L/min)

Question 18

does the vaporizer have high or low resistance? how is this acheived?

Answer 18

 High resistance- Design with variable bypass and small tubing results in high resistance

Question 19

can we use the same vapourizer for different gases?

Answer 19

NO
Specificity- Design for specific inhalational anesthetic

Question 20

what is out of the circuit vaporizer flow?

Answer 20

 Out of the circuit- between flowmeter and the circuit. Not between unidirectional valves and Y piece

Question 21

what are the unidirectional valves for? when are they used?

Answer 21

 Inspiratory flow- inspiratory valve
 Expiratory flow- expiratory valve
 They prevent backflow through the opposite limb (inspiratory or expiratory)
 Used with rebreathing systems
* Circle, F-circuit
* Not part of the non-rebreathing system

Question 22

what is the purpose of the rebreathing bag? does it send/.receive air with CO2? what can we use the bag for?

Answer 22

 Reservoir from which the animal can breath part of the tidal volume (VT)
* Part of the tidal volume also comes from what is present in the anesthetic circuit (hoses)
 CO2 is removed from gases before entering inspiratory valve
* Flow is directed through soda lime absorber as leaves bag or before enters bag
 Intermittent positive pressure can be applied to the bag to manually ventilate the patient

Question 23

how do we size a rebreathing bag?

Answer 23

 Size: usually 3 times VT = 20 mL/kg;
therefore 60 mL/kg.
* 1L bag for up to 15kg
* 2L bag if 15-30kg
* 3L bag if over 30kg
* 5-10 L bag if 100-200 kg
* 30 L bag for adult LA

Question 23

how do we size a rebreathing bag?

Answer 23

 Size: usually 3 times VT = 20 mL/kg;
therefore 60 mL/kg.
* 1L bag for up to 15kg
* 2L bag if 15-30kg
* 3L bag if over 30kg
* 5-10 L bag if 100-200 kg
* 30 L bag for adult LA

Question 24

what does the carbon dioxide absorber contain? how does it work? how does it change with use? is it necessary in both rebreathing and non-rebreathing systems?

Answer 24

 Holds sodalime (most commonly) or baralyme
 Sodalime is composed of active ingredients, water, hardener and pH indicator
* Prior to use, soda lime is creamy-white, soft, moist, and easily crumbled
* After use and exhaustion, soda lime is hard, dry and changes to purple, (color will revert back to white with sitting)
 Applicable only to rebreathing system
 Non-rebreathing systems use high FGF to eliminate CO2 from the system

Question 25

what is the composition of sodalime?

Answer 25

• 80% calcium hydroxide
• 15% water
• 4% sodium hydroxide
• 1 % potasium hydroxide

Question 26

what are the reactions that are undergone to eliminate CO2?

Answer 26

1) CO2 + H2O <> H2 CO3
2) H2CO3 + 2NaOH <> Na2CO3
3)Na2CO3 + Ca(OH)2 <> CaCO3 + 2NaOH

Question 27

what is the manometer for? what should it read for spontaneuous breathing? mechanical ventilation?

Answer 27

 Pressure gauge
 Indicates pressure within the breathing circuit.
 Spontaneous breathing
* Pressure gauge should read 0 cm H2O
 Mechanical ventilation
* Pressure gauge rises up to 20 cm H2O
* “Positive pressure ventilation”

Question 28

what is the oxygen flush valve for? what does it bypass? what is the purpose?

Answer 28

 Enables flow of emergency oxygen to the circuit
 Bypasses the flowmeter and vaporizer
* Dilutes the concentration of inhalational anesthetic in the anesthetic circuit and patient
 Delivers 100% oxygen to the breathing circuit at high flows (40-70 L/min) and intermediate pressures (50-60 psi)

Question 29

why should we not use the oxygen flush valve with a non-rebreathing system?

Answer 29

• Would deliver high flows directly to animal’s airway and risk trauma

Question 30

what is the common as outlet? what goes through it?

Answer 30

 Outlet on machine for gases (all gases from the flow meter(s) that have passed through or over the vaporizer).
 Anesthetic circuit is connected to this outlet
 Oxygen Flush system also exits machine at this outlet

Question 31

what is the pop-off valve? what are the closed and open positions for?

Answer 31

 “Adjustable pressure limiting valve”
 “Pressure relief valve”
 Open position
* For spontaneous ventilation
 Closed position
* Allows mechanical ventilation since the ventilator has a spill valve that releases the pressure during the expiratory phase

Question 32

what is the scavenger system? what does it do? what types are there?

Answer 32

 Exhaled gases are directed to the outside
* Passive scavenge system (window)
* Active scavenge system (suction, exhaust fan)

Question 33

where will we find the interface?

Answer 33

 If an interface is present, it will be located between the pop-off and the scavenge system to the outside

Question 34

what is the use of a charcoal cannister in a scavenger system?

Answer 34

• Also removes waste gases and inactivates them
• Used “in situ”
• Used during transport between areas

Question 35

what is the interface? what is its purpose?

Answer 35

 Controls flow of exhaled gases coming from scavenger (anesthetic circuit, ventilator)
* Allows “centralizing” the scavenging system from more than one anesthetic system in the machine (e.g., non-rebreathing system [Bain] and rebreathing system [circle]) and ventilator
 Prevents excessive filling or emptying of reservoir (rebreathing bag).