Medical Gas Systems Flashcards
Purity of cylinders is regulated by
Pharmacopeia of US
Cylinders are inspected
Q 10 years by DOT
Regulates storage/transportation of compressed gas
DOT
Standards for manufacturing/delivering compressed gas
Compressed gas association
Publishes minimum safety/performance standards for anesthesia machine
ANSI - American National Standards Institute
ASTM - American Society for Testing and Materials
Oxygen E-Cylinder
2000 psi
625-700L
Nitrous Oxide E-Cylinder
CT 36.5* (kept liquefied)
745 psi
1590 L
—> must be weighed
Air E-Cylinder
*Same as Oxygen
Blended O2+N2O
Cylinders marked 3AA, 3AL, 3ALM
Do not bring in MRI
DISS
End of hose—> gas outlet in pipeline
*safety precaution
PISS
E-Cylinders: 2 holes in cylinder valve —> corresponding pins in yoke in anesthesia machine
O2 Pin index position
2+5
Air Pin Index Position
1+5
Nitrous Oxide Pin Index Position
3+5
Sources of resistance
APL valve Connectors HMEs/Humidity CO2 Absorbers ET tubes Circuit Tubing
Breathing system that adds least resistance
Open system (insufflation)
Location of most resistance in intubated pt
Connxn btwn ETT—> circuit connector/Y-piece
Location of most resistance in unintubated pt
Expiratory valve in semi-closed system
Open systems
No reservoir bar, rebreathing, CO2 neutralization or valves
- insufflation
- open drop ether
Open drop methods used today
Pediatric mask induction with mask not on face —> blowby
Semi-open systems
Gas reservoir, corrugated tubing, APL, common source of fresh gas
=mask on face
FGF > MV, no rebreathing
Circuit changes classes based on
FGF rates
Semi open systems
Mapleson systems
Semi closed systems
=Mask on face No room air inspired FGF < MV Unidirectional, inspiratory/exp limb CO2 absorber
Closed system
APL closed
Gas flow = pt uptake (CO2 absorbers used)
Best for spontaneous ventilation
Mapleson A
Mapleson B
Reqs 2X MV of FGF (prevent rebreathing)
FGF requirement = NO rebreathing
250 mL/min
FGF > Alveolar ventilation
Mapleson Circuits: Controlled Ventilation
D>B>C>A
“Dead Bodies Can’t Argue”
Mapleson Circuits: Spontaneous Ventilation
A>D>C>B
All Dogs Can Bite
Most common semi-closed system used today
Circle system
Closed system
FGF is 150 - 500 mL/min
Anesthetic agents contained in system, not vented
Closure of APL valve (rebreathing gases)
Disadvantages of closed system
Unpredictable (gas % and O2)
