Anesthesia Machine/Delivery Systems Flashcards
Name the components of the anesthesia workstation
◾Anesthesia machine ◾Vaporizers ◾Ventilator ◾Breathing circuit ◾Scavenging system ◾Monitoring system

What is the high pressure circuit?
Cylinders (typically E-cylinders) and primary pressure regulator. O2 - up to 2200 psi N2O - up to 745 psi
What is the intermediate pressure circuit?
Pipeline sources (50-55 psi), down-regulated cylinder sources (45psi)
What is the function of a pressure regulator?
Reduce gas pressure from variable pressure cylinders to a consistent 45psi Some machines have a second stage O2 pressure regulator to further decrease oxygen pressure within the machine to a set pressure (12-19psi)
When are the cylinders utilized?
When pressure within the machine drops below 45psi
What is the function of the fail-safe valve?
on each NON-O2 gas line Shut off or decrease supply pressure (oxygen failure protection device) of all other gases if O2 line pressure falls to 28psi Prevents delivery of gas is O2 supply fails
What is the low pressure circuit?
Machine from flow-control valves –> common gas outlet, including vaporizers
What is the flow of oxygen delivered when using the oxygen flush valve?
100% O2 @ 35-75L/min at 50psi
What is the color code for the following medical gases in the US: Oxygen Nitrous oxide Air CO2 Nitrogen
Oxygen = green Nitrous oxide = blue Air = yellow CO2 = grey Nitrogen = black
What is the only monitor that detects problems/hypoxic mixture downstream of the flow control valves (low pressure circuit)?
Oxygen analyzer = one of the most important monitors
Why is oxygen the last gas in the sequence of flow meters?
If one of the other gases leaks, its position is the least likely to result in hypoxic mixture
What is the proportioning system on the anesthesia machine?
aims to prevent delivery of hypoxic mixtures Nitrous and O2 intercede mechanically and pneumatically to minimum [O2] at common gas outlet is 23-25%
What are the limitations of the fail-safe system?
Only reads pressures. If gas pipelines are crossed - may allow hypoxic mixture
What 3 things can fool the proportion limiting systems?
- wrong supply gas 2. defective pneumatics or mechanics 3. leaks downstream
How are flowmeters calibrated?
specifically for each gas based on density and viscosity of the gas
What should you do if the oxygen low pressure alarm sounds?
- indicates profound loss of O2 pipeline pressure –> fully open E-cylinder + disconnect pipeline and consider use of low fresh gas flows
Describe a non-rebreathing system
no rebreathing of exhaled gases ◾Reliable control of the inspired [gas] ◾Elimination of CO2 by venting all expired gases from the system. ◾High flow rates (equal to or more than the patient’s minute ventilation) must be supplied to the patient to prevent rebreathing, and so they are less economical to use. ◾Operating room environmental pollution is a problem. ◾Examples = AMBU bag, and the Mapleson Non-Rebreathing Circuits (Classification A-F).
Describe a partial rebreathing system
partial recirculation of exhaled gas ◾most commonly used partial rebreathing configuration ◾circular flow of gases, separation of inspiratory and expiratory channels, unidirectional valves and carbon dioxide absorbers. ◾Mapleson Systems can also behave as partial rebreathing systems at low fresh gas flow (FGF) rates; however there is risk of rebreathing exhaled CO2 since there are no unidirectional valves, no clear separation of inspired and expired gases and no CO2 absorbers.
Describe a complete rebreathing system
inflow gas exactly matches consumption by the patient In a closed system - complete rebreathing of exhaled gases after absorption of CO2. A circle system can be used in a closed configuration at extremely low fresh gas flows.
What are the major components of a classic circle system?
◾Fresh gas inflow site (best downstream of CO2 abs b4 inspiratory uni-valve) ◾Inspiratory and expiratory limbs ◾Inspiratory and expiratory unidirectional valves ◾Y-Piece ◾Reservoir bag ◾Ventilator ◾Bag/ventilator selector switch ◾Carbon dioxide absorber ◾Adjustable pressure limiting (APL) valve ◾Air pressure monitor gauge ◾Spirometer Optional: ◾Positive end expiratory pressure (PEEP) valve ◾Filters ◾Heated humidifier ◾Respiratory gas monitor sensor / gas sampling line.

How does a CO2 absorber work?
CO2 + water –> carbonic acid + calcium hydroxide –> carbonate, water and heat Contains silica –> less likely to disintegrate –> dec breathing system resistance pH indicator to highlight exhaustion (ethyl violet)
What are the two types of absorbents?
- High alkali absorbents (#1) 2. Alkali-free absorbents
Describe the high alkali absorbents
Soda lime formulations Mixture of calcium hydroxide (CaOH2) 75%, water 20%, sodium hydroxide (NaOH) 3%, potassium hydroxide (KOH) 1% When dessicated, they react w/ volatile anesthetics –> CO Compound A formation with Sevo
Describe the alkali free absorbents
Calcium hydroxide No CO formation No compound A formation



