Anesthetic Equipment Flashcards
what is held in the gas cylinders? what do the gasses do?
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
what percent oxygen is in the gas cylinder? what sizes? what pressure?
>99.5% O2
Sizes:
* E, H
Pressure: full tank has 2200 psi (pounds per square inch) * High pressure system
have can we find out the number of liters in a small (E) and large (H) oxygen tank?
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
what is the purpose of grouping oxygen tanks for H tanks?
H- larger tank
* They can be grouped to maintain constant supply and avoid frequent changing of regulators
conversion of liquid oxygen to gas oxygen?
1 L of liquid oxygen = 860 L of gas
what temp should we store liquid oxygen at?
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
Yoke index for E-tanks
- Positions
– Oxygen 2 & 5
– N2O 3 & 5
Pressure regulator does what?
Reduces high pressure of tank (up to 2200 psi) supply to a lower pressure of 50 psi
* Establishes intermediate pressure system
what does the oxygen flowmeter do? what is the pressure in the flowmeter?
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
Oxygen requirements and fresh gas flow (FGF) - min oxygen reqs? what is it needed for?
Minimum oxygen requirements (VO2)
* 5-10 mL/kg/min
* Necessary to maintain aerobic metabolism
what does a rebreathing system allow for? what are the types?
- One that allows CO2 to be extracted by the anesthetic circuit system used
- Circle system, F-circuit
what does a non-rebreathing system allow for? what are the types?
- One that uses FGF to flush the CO2 out of the anesthetic system
-bain system**
-also lack system, magill
what is fresh gas flow through the rebreathing system?
- 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
what is fresh gas flow for a non-rebreathing system?
- 130-200 mL/kg/min
what does the vapourizer do?
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
what is the purpose of vaporizer percision, variable by-pass, and automatic temp. ompensation?
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
what is the purpose of automatic flow commpensation for the vaporizer?
Automatic flow compensation- Accurate output despite of FGF (300 mL/min – 10 L/min)
does the vaporizer have high or low resistance? how is this acheived?
High resistance- Design with variable bypass and small tubing results in high resistance
can we use the same vapourizer for different gases?
NO
Specificity- Design for specific inhalational anesthetic
what is out of the circuit vaporizer flow?
Out of the circuit- between flowmeter and the circuit. Not between unidirectional valves and Y piece
what are the unidirectional valves for? when are they used?
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
what is the purpose of the rebreathing bag? does it send/.receive air with CO2? what can we use the bag for?
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
how do we size a rebreathing bag?
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
how do we size a rebreathing bag?
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
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?
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
what is the composition of sodalime?
- 80% calcium hydroxide
- 15% water
- 4% sodium hydroxide
- 1 % potasium hydroxide
what are the reactions that are undergone to eliminate CO2?
1) CO2 + H2O <> H2 CO3
2) H2CO3 + 2NaOH <> Na2CO3
3)Na2CO3 + Ca(OH)2 <> CaCO3 + 2NaOH
what is the manometer for? what should it read for spontaneuous breathing? mechanical ventilation?
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”
what is the oxygen flush valve for? what does it bypass? what is the purpose?
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)
why should we not use the oxygen flush valve with a non-rebreathing system?
- Would deliver high flows directly to animal’s airway and risk trauma
what is the common as outlet? what goes through it?
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
what is the pop-off valve? what are the closed and open positions for?
“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
what is the scavenger system? what does it do? what types are there?
Exhaled gases are directed to the outside
* Passive scavenge system (window)
* Active scavenge system (suction, exhaust fan)
where will we find the interface?
If an interface is present, it will be located between the pop-off and the scavenge system to the outside
what is the use of a charcoal cannister in a scavenger system?
- Also removes waste gases and inactivates them
- Used “in situ”
- Used during transport between areas
what is the interface? what is its purpose?
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).
