Anesthesia Machine Flashcards
What is the fail-safe valve?
Prevents delivery of hypoxic gas mixtures.
Based on pressure from oxygen supplies.
Turns off nitrous oxide if in use. Can be proportional or on/off
How does the fail-safe valve work?
In the event of a failure of the oxygen supply (oxygen delivery line pressure decreases below 30 psi), proportionally decreases the flow of all other gases.
Prevents unrecognized exhaustion of oxygen cylinder or if hospital supply line failure.
Does not prevent delivery of 100% N2O when O2 flow is zero. The provider will also need to monitor the oxygen analyzer to detect hypoxic gas mixtures.
Diameter Index Safety System (DISS)
Fittings that are noninterchangeable to prevent misconnections of pipeline gases (from the wall source).
The pipeline gases come into the wall with color-coded outlets.
Hospital pipeline pressure.
Approximately 50 psi
Pin Indexed Safety System (PISS)
Prevents misconnection of the cylinders to the hanger yoke assembly. Makes it impossible to attached the wrong cylinder.
Medical air has pins 1 and 5
N20 pins 3 and 5
O2 pins 2 and 5
Oxygen E-cylinder
Green Pins at 2,5 Full tank pressure: 1900-2000 psi Full tank volume: 625-660L Volume proportional to psi/pressure, ex: psi 1000 = 1/2 full or ~330L
Nitrous Oxide (N2O) E-cylinder
Blue
Pins: 3,5
Pressure: 745-750 psi until 75% empty or all liquid nitrogen has vaporized
Determine tank volume via weight
Once pressure beings to fall below 750 psi less 25% left or ~400L
Total volume of a full tank: 1590
Why does frost accumulated on E-cylinder valves and tanks?
The expansion of compressed O2 and vaporization of liquified nitrous oxide absorbs heat. Heat is extracted from the cylinder and atmosphere. This causes condensation from the water in our atmosphere.
There will never be internal icing because gases in the tank are free of water vapor
How do flowmeters measure flow?
Measurement based on the principle that flow past a resistance is proportional to the pressure.
Proportionality between pressure and flow is determined by the shape of the tube (resistance) and the physical properties (density and viscosity) of the gas.
Calibrated to a specific gas, and not interchangeable. Color coded.
Flowmeters design
Gas enters at the bottom of vertically positioned and tapered glass flow tube.
Gas as it enters raises the bobbin or ball shaped float
Gas is off when gravity is balanced by the decrease in pressure.
*The cross sectional area increases upward from the site of gas entry.
The oxygen flush valve
Bypasses flowmeters. Direct communication between high and low pressure circuits.
Delivers 35-75L/min
Pressure of 50 psi or hospital pipeline
Can cause barotrauma. Avoid using during mechanical inspiration. No relief valve.
High Pressure system pressure value
Related to tank pressure. Oxygen tanks at full are 2200psi. N2O is 745psi
Components of the hight pressure system.
Cylinder Hanger yoke assembly PISS- pin indexed safety system Pressure gauge, indicator for cylinders Ends at the pressure reducing valve
Intermediate pressure system pressure?
35-55psi
Intermediate pressure system components
Pipeline inlet connects for wall source Pipeline pressure gauges piping gas power outlet master switch O2 pressure failure devices O2 flush valve Secondary stage reducing device if GE Flow control valves
