Gas machine PPT Flashcards
Gas machines have a system to provide and measure (3):
- Oxygen
- Anesthetic agents
- CO2
SPDD (gas machine organization)
Supply
Processing
Delivery
Disposal
Supply for gas machine (2) - how do gasses get into the machine?
Pipeline and cylinders
O2 hospital pipeline liquid oxygen is converted to gas pressure of
50 psi
DISS stands for (and fucntion)
Diameter Index Safety alarm
non-interchangable, threaded fittings to connect gas powered devices to station outlets
cylinders on back of machine should be kept closed so that
alarm will sound with a loss of pressure
What is the most frequently missed item in preanesthesia setup
amubag
Cylinder valve
Most fragile part of cylinder
has a unique arrangement of holes that correspond with contents
Pipeline psi
50 psi
Oxygen cylinder is supplied at (psi)
1900-2200 PSI
Oxygen in cylinder is regulated to ____ PSI after it enters the machine
45 psi
NIOSH recommendation fo occupational exposure to nitrous
<2ppm halogenated agents (0.5 ppm if using N2O)
NIOSH reccomendation for occupation exposure to N2O alone
<25 ppm
What prevents one cylinder from emptying into the other
Free floating valve
E cylinder with highest pressure
closes valve on the cylinder with less pressure
Check valve in cylinder yoke (3):
- Minimizes trans-filling
- allows change of cylinders during use
- Minimizes leaks to atm if yoke is empty
Regulator in cylinder
supplies constant downstream pressure (45 psi) so that if cylinder is left open, gas will still flow
O2 service pressure
1900 psi
N2O service pressure
745-750
Air service pressure
1900
O2 capacity
660L
N2O capacity
1600 L
Air capacity
635 L
The five tasks of oxygen:
- Flows to the fresh gas flowmeter
- Powers the oxygen flush
- activates fail safe mechanics
- Activates oxygen low pressure alarm
- Compresses the bellows of mechanical ventilators
Flowmeters are located downstream from all safety devices and alarms EXCEPT:
the oxygen analyzer
When should you flush to fill bellows?
during EXPIRATION
Oxygen flush valve
Bypasses vaporizers and can dilute anesthetic
Gate of gas outlet is held open by
pressure in the oxygen line
(oxygen must be present for gate to remain open)
Gate closes if oxygen pressure is not met
Piston ventilators may operate for prolonged periods with only cylinder supplies because:
They do not consume oxygen to drive the bellows
A ventilator not driven on pistons and driven on oxygen can consume a whole E cylinder in:
30 minutes
Final breathing mixtures at the common gas outlet are
at least 23% to 25% oxygen
How can oxygen proportioning fail (4)?
- wrong supply of gas in oxygen pipeline or cylinder
- Defective pneumatics or mechanics
- Leaks downstream of flow control valves
- innert gas administration (third gas such as helium)
Low pressure alarm and hypoxic guard systems are based on
the pressure within the oxygen circuitry of the gas machine
______ determines that oxygen is present
Inspired Oxygen Analysis
*ONLY ONE SYSTEM that does this
Inspired oxygen analysis check
MUST check function before ANY anesthesia care, including MAC cases in case of needing to convert to GA
What is used to contain liquid in the vaporizers and why
copper, because it has high thermal conductivity and capacity
The rate of vaporization depends on:
- temperature
- vapor pressure of the liquid
- partial pressure of the vapor above the evaporating liquid
vapor prsesure
equilibrium between molecules leaving liquid phase into gaseous phase and molecules leaving gaseous phase and entering liquid phase
Latent heat of vaporization
heat required to change one mol of liquid into gas
Specific heat
heat required to raise the temp of 1g of substance by 1 degree celcius
Thermal conductivity
ability of a given material to conduct/transfer heat
Ambient pressure effect*
Boyle’s law
If volume increases, pressure decreases and vice versa
Tec 6 vaporizers are designed specifically for_____and are ______ heated
desflurane, electrically heated
Tec 6 vaporiers are pressurized to____.
2 atmospheres
Desflurane must be heated to
maintain a constant temp and vapor pressure. It has a vapor pressure 3-4 times that of other gasses and boils at room temp, need to prevent “boiling out” at room temp
Altitude and desflurane vaporizer output
Higher altitude = lower barometric pressure
You would need to increase dial at higher pressure to obtain same effect at lower altitude
During the ____ stage, low fresh gas flows are good
maintenance
increasing the flows on induction will _______ the speed of equilibrium
increase
After induction, too low of flows could cause
awareness
The low pressure leak test evaluates:
the integrity of the anesthesia machine from the flow control valves to the common gas oullet
Evaluation of the circle system and APL valve: (where does it evaluate)
evaluates from common gas outlet to patient
Circle system and APL valve evaluates: (what does it evaluate)
- Leak in circuit
2.proper inspiratory and expiratory flow
Gas enters the system from ______ and exits ______
enters from CGO by way of fresh gas delivery hose, and exits the circle to the scavenger via the APL valve
APL valve aka
adjustable pressure-limiting valve
APL valve function (4):
-provide dialed-in amount of pressure to patient
-PEEP
-manual ventilation
-assisted respiration
What determines breathing circuit resistance(2)?
circuit diameter and length
What machine alarms are based on circuit pressure?
- disconnection alarm
- high pressure alarm
Most common critical incidents occur from
disconnection at the Y piece
Boyle’s law
Volume of gas and pressure of gas are inversely related
What can reliably detect a disconnection in the breathing circuit (2)?
- ETCO2
- Respirometer
What is the most important part of the scavenging system
the scavenging interface
