Anesthesia Machine Flashcards
What is the best way to detect a vaporizer leak?
- Negative pressure test (low pressure leak test)
- assesses the integrity of the low pressure system
What does the high pressure leak test assess for?
- if the machine does NOT have a check valve: breathing circuit and entire low pressure system
- if the machine has a check valve: breathing circuit and low pressure system up to the check valve
What are the PISS configurations for air, O2 and N2O?
- Air: 1, 5
- O2: 2, 5
- N2O: 3, 5
What is the max pressure and volume for air?
- 1900 (or 2000) psi
- 625 L
What is the max pressure and volume for O2?
- 1900 (or 2000) psi
- 660 L
What is the max pressure and volume for N20?
- 745 psi
- 1590 L
- only reliable method to determine the volume that remains is to weigh it
- N2O is a liquid and will read 745 psi until the liquid is gone and only gas remains - at this point the cylinder is about 3/4 empty
- wise to change the tank anytime it falls below 745 psi
What is the main purpose of the oxygen pressure failure device?
- monitor for and protect against low O2 pressure in the anesthesia machine
- it is the pressure in the supply line (not O2 concentration) that maintains fail-safe in the open position
- resides in the intermediate pressure system
How does the Hypoxia Prevention Safety Device work?
- prevents you from setting a hypoxic mixture with the control valves
- Limits N2O flow to 3 times O2 flow (N2O max ~ 75%)
When are instances when proportioning devices CANNOT prevent a hypoxic mixture?
- O2 pipeline crossover
- leaks distal to the flowmeter valves
- administration of a third gas (helium)
- defective mechanic or pneumatic components
There are 4 types of floats in flowmeters. Where is the measurement taken at each?
- the widest part of the float
Where should the O2 flowmeter be positioned to prevent a flowmeter leak from creating a hypoxic mixture?
- all the way to the Right (closest to the common gas outlet)
What are concepts that come to mind about a Variable Bypass Vaporizer?
- variable bypass
- flow-over
- temperature compensated
- out-of-circuit
- agent specific
Does the pumping effect increase or decrease vaporizer output?
- increases
- usually d/t positive pressure ventilation or use of flush valve
- it is enhanced by low FGF, low dial setting, and low levels of anesthetic gas
- this effect is minimized by the modern vaporizer
Does tipping the vaporizer over cause an increase or decrease in output?
- increase
- run FGF through the vaporizer for 20-30 min before connecting to the pt
What are concepts that come to mind about the Tec6 vaporizer?
- it heats and pressurizes to 39 C & 2 atms
- uses an injector
- doesn’t compensate for changes in elevation
- at Higher elevation the partial pressure in the breathing circuit is Lower than expected
- at Lower elevation or hyperbaric chamber the partial pressure in the breathing circuit will be Higher than expected
What are key points about the oxygen analyzer?
- it monitors O2 concentration (not pressure)
- can detect O2 pipeline crossover
- can detect leak in breathing circuit (most common is circuit disconnect and 2nd is CO2 canister)
Which type of pneumatic bellows will not fill if there is a disconnect, ascending or descending?
- Ascending - regarded as safer b/c of this
What happens when there is a leak in the pneumatic bellows?
- may transmit high gas pressure to the breathing circuit
- increased breathing circuit pressure may cause barotrauma
- if there is a bellows leak and O2 is used as the ventilator drive gas, FiO2 in breathing circuit may increase
- if there is a bellows leak and air is used as the ventilator drive gas, FiO2 in breathing circuit may decrease
What is the mechanism of a piston ventilator?
- use an electric motor to compress piston to generate positive pressure
- won’t consume O2 tank w/pipeline failure
How many pressure relief valves are on the piston ventilator?
- there are 2 pressure relief valves: + and -
- Positive pressure relief: opens @ 75+/-5 cm H2O (prevents excessive build up in anesthesia circuit)
- Negative pressure relief: opens @ -8 cmH2O (when circuit pressure galls below this value, the valve opens and entrains air) - protects against negative end-exp. pressure
How do piston ventilators deliver constant tidal volume?
- Fresh gas decoupling
What happens to the breathing bag on the piston ventilator during mechanical ventilation?
- the bag is incorporated into the vent during mechanical ventilation
- bag inflates during inspiration and deflates during expiration
- if the bag rapidly deflates suspect circuit disconnect
- piston won’t move when the pt initiates spontaneous breath on the ventilator
What are the fixed and variable components of Volume Control Ventilation?
- Fixed: TV, Insp. Flow Rate, Insp. Time
- Variable: Peak insp. pressure
What are the fixed and variable components of Pressure Control Ventilation?
- Fixed: Peak Insp. Pressure, Insp. Time
- Variable: TV, Insp. Flow
What are advantages of PCV?
- delivers larger TV for given insp. airway pressure
- insp. flow pattern improves gas exchange
- dec. risk of vent associated lung injury (VALI)
- useful if pt has low compliance (high PIP is dangerous) or to compensate for leaks
What are disadvantages of PCV?
- inc. airway resistance and/or dec. lung compliance dec’s TV
- requires extra attention w/circumstances that can alter pulmonary resistance or compliance will cause TV to change
What is the final product of the soda lime reaction?
- Calcium carbonate + 2 Sodium Hydroxide
At what pH does the indicator ethyl violet change from clear to purple?
- 10.3
- it may revert to a colorless stage when the machine is not in use, but will change back as soon as it comes in contact with CO2
If unable to change exhausted soda lime, what should you do?
- increase FGF to convert a circle system to a semi-open system
- this will prevent rebreathing and capnograph should return to zero
What are benefits of using Calcium Hydroxide Lime (Amsorb Plus)?
- no carbon monoxide
- very little or no compound A
- may be lower risk of fire
What are drawbacks of using Calcium Hydroxide Lime (Amsorb Plus)?
- absorbs less CO2 than soda lime and requires more frequent changing
- more expensive
