week 1 Flashcards
What measures a loss of oxygen pipeline pressure?
The pipeline pressure gauge indicates a loss of oxygen pipeline pressure.
What happens if pressure loss is profound?
The oxygen low-pressure alarm sounds, and the fail-safe valves halt the delivery of all other gases.
Problems with pipeline supply (5)
Pressure loss or excess pressure
Cross-connection of gas delivery pipelines
Contamination
Leaks
Theft of nitrous oxide
Pipeline oxygen is stored at what temperature?
Delivered to the hospital and stored as a liquid, at -184C.
What is pipeline O2 made from?
Made from fractional distillation of liquid air.
What are some Cylinder Safety we need to know?
*No oils or lubricants
*Temperature should be under 130 degrees Fahrenheit (57ºC)
*Keep connections tight
*Don’t interchange regulators/gauges
Keep closed when not using
Open slowly
Don’t stand them up on their own
When attaching to AGM
Crack valve 1st to prevent dust going into machine
New washer for every new tank, never more than 1 washer
What are 3 safety devices on a cylinder?
Frangible disc that bursts under pressure
Valve that opens under extreme pressure
Fusible plug made of Wood’s metal
What does a Hanger Yoke do?
Orients the cylinder
Provides a gas tight seal
Ensures unidirectional flow
Contains a filter required by standard
Check valve to minimize transfilling
The cylinder valve consists of:
body, the outlet port where gas exits, a conical depression for the securing screw, PISS pins, and safety relief devices.
CO2 service pressure is ____ and weighs____
838 psi (full tank is 1,590L)
When CO2 or N2O’s liquid runs out, how much is left in the tank?
Once liquid is gone tank is ¾ empty (~136L left)
International color for oxygen and air?
Oxygen: White, Air: White and black
CO2 psi and temp in cylinder is:
838 psi, < 31 C in gas and liquid
N2O temp in cylinder is:
< 37 C in gas and liquid
Helium psi and weight
2000 psi, 500 L
Nitrogen psi and temp (same as O2)
2000psi, 660L
H-size cylinder is what diameter
H – 4’ x 9” diameter
Bedside when no pipeline available
In OR - N2 compressed gas
How many positions for pins in PISS system?
7
5 tasks of oxygen in the AGM
- O2 supply failure alarm system
If pipeline or cylinder pressure falls less than 30 psig - O2 Pressure Failure Device
AKA Fail-safe valve
Machine will not deliver less than a certain percent of oxygen when also administering a non-life sustaining gas (example nitrous oxide)
Cuts off nitrous oxide or heliox if oxygen concentration gets too low - Ventilator drive Gas
Ventilator power (to bellow)
Auxiliary flowmeter
Jet vent devices- O2 supply line - Flowmeters →circle system → patient
- O2 flush valve → circle system → patient (typically used when not connected to patient, never ever press flush in children, usually used for machine checks)
Bypasses flowmeters
Range between 25-75 L/m directly from pipeline or cylinder depending on model
Open scavenger:
*No risk of barotrauma
*Too much suction = room air entrained
*Too little suction= waste gas goes into OR (expose personnel)
*Contains reservoir
Open to atmosphere
Only used with active systems (suction)
No positive or negative pressure relief valves
Closed scavenger:
*Doesn’t remove excess fresh gas from circuit (because it removes excess exhaled waste anesthetic gases WAG)
*Contains reservoir
Uses pressure valves
If passive system (no suction)- needs positive pressure relief
If active (suction) needs both positive and negative pressure relief
Contains reservoir
Scavenger formula for removing excess gas:
FGF - volume of gas lost to pts O2 consumption
Convenience receptacles are protected by: _____ or _____
Blowing a ____, what would happen?
These convenience receptacles are protected by circuit breakers or fuses. In theory, blowing a fuse in one of these circuits should not affect the operation of the rest of the machine.
Devices which require electric power supply
Cardiopulmonary bypass pump/oxygenators
Air warming blankets
Gas/vapor blenders (Suprane Tec 6) or vaporizers with electronic controls (Aladin cassettes in the ADU or Aisys)
Mechanical ventilators
Electronic monitors
Room and surgical field illumination
Digital flowmeter displays for electronic flowmeters
What devices/techniques do not need electrical power supply?
*Mechanical flowmeters
*Scavenging
*Battery operated peripheral nerve stimulators or intravenous
*Monitoring using the anesthetist’s five senses
*Variable bypass vaporizers (Tec 4, 5, 7, Vapor 19 or 2000)
Bag-mask ventilation
Laryngoscope, flashlights
Intravenous bolus or infusion pumps
What is high pressure leak test and how to test for it?
Tests integrity of low-pressure system and breathing circuit
Close APL valve to pressurize circuit to 30cm H2O
Fail = circuit does not remain pressurized ~ 30cm H2O
Should be completed between every patient/ when the circuit is changed
Guideline for Oxygen Pipeline Supply Failure
Do not attempt to fix the oxygen analyzer. It must be trusted until proven inaccurate.
Turn on backup oxygen cylinder on machine fully and disconnect pipeline. If inspired 02 does not increase, ventilate by bag mask and initiate TIVA (total IV anesthetic)
Call for help,
Use low flow of oxygen.
Turn off ventilator and bag manually
Call for help, calculate the time remaining on the cylinder.
Find out details of problem and how long.
DO NOT reconnect patient to pipeline unless it is tested.
Ventilate with an oxygen source or room air via bag valve mask.
Why would Oxygen Pressure Failure Device (Failsafe) alarm?
Depleted O2 tank
Decreased pressure from pipeline
Disconnected O2 hose
When will a Fail safe Device NOT alarm?
Pipeline Crossover
Crack/Leak in the flowmeters (upstream from fail safe device)
How to test if fail safe is working properly?
You turn on O2 and N2O. Then, disconnect the oxygen pipeline and oxygen cylinder and leave the nitrous on until the oxygen reads before 0. It should alarm and stop N2O from running.
When will a hypoxic mixture still occur
*Administration of 3rd gas (Helium)
Pipeline crossover
Leak distal to flowmeter valves
scavenger malfunctioning
Defective mechanic or pneumatic components
Dilution of oxygen due to high concentration of inhaled anesthetics (barash p. 1620)
Minimum FiO2 permitted: 25%
Flowmeter pressure is ____
16 psi
Flowmeter where is the largest diameter
Thorpe tube is gas specific and tapered with largest diameter at top
What is Reynolds number and the formula?
Predicts flow rate through tube; ([DensityDiameterVelocity]/Viscosity)
What is Reynolds number for laminar flow, dependent on ____?
Re< 2,000 = laminar flow (stable, smooth, and predictable)
Depends on gas viscosity
What is Reynolds number for turbulent flow, dependent on ____?
Re> 4,000 = turbulent flow (chaotic, irregular motion and mixing of fluid particles.)
Depends on gas density
What is Reynolds number for transitional flow?
Re 2,000-4,000 = transitional flow
What is fresh gas coupling?
couple fresh gas flow to the set tidal volume
What is fresh gas coupling Tidal volume delivered to the pt?
Vt set on vent + FGF during inspiration- volume lost to circuit compliance
How to calculate fresh gas coupling?
Step 1: Convert Fresh Gas Flow (FGF) from L/min to mL/min (multiply by 1,000)
Example: 4 L/min = 4,000 mL/min.
Step 2: Multiply FGF (ml/min) by the I:E Ratio (If the ratio is 1:2 = 1/3).
This is the amount of FGF delivered during the inspiratory phase.
Ex: 4,000 mL/min×(1/3)=1,333 mL
Step 3: Calculate Tidal Volume per Breath (Divide the insp. FGF by RR)
Ex: 1,333 mL/min/ 10 breathsperminute=133 mL
Step 4: Add set Tidal Volume on ventilator to insp. FGF
Example: 500 mL+133 mL=633 mL
How does an increase in respiratory rate affect delivered tidal volume?
decrease Vt
What decreases Tidal volume delivered in terms of I:E ratio, FGF, bellows height?
decrease I:E (1:2 to 1:3), decrease FGF, decreases bellows height
What increases Tidal volume delivered in terms of I:E ratio, FGF, bellows height?
increase I:E (1:2 to 1:1), increase FGF, increases bellows height
How does a decrease in respiratory rate affect delivered tidal volume?
increase Vt
How does positive pressure in a breathing circuit affect the gas volume delivered to the patient?
causes gas to expand, this will not reach the pt
*This must be subtracted from total Vt
Increase the set tidal volume slightly if circuit compliance and pressure loss are known to reduce the delivered volume.
What do modern ventilators do to circuit compliance?
compensate for circuit compliance when delivering Vt
What is formula for circuit compliance?
Change in volume/change in pressure
How does splitting ratio work?
fresh gas enters vaporizer, some gas encounters the anesthetic, and the rest bypasses it, in the end they mix and create the final concentration