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
