Exam 1 Flashcards
What is the purpose of the fail-safe valve? What triggers the fail-safe valve on the anesthesia machine?
To ensure that whenever oxygen pressure is reduced and until flow ceases the set oxygen concentration will not decrease in the common gas outlet. The loss of oxygen pressure triggers the high-priority alarm audible and visible (around 30 psi)
Can a hypoxic mixture be delivered from the anesthesia machine with an intact fail-safe valve? Explain.
Yes as long as there is pressure in the oxygen line nothing in the fail-safe system prevents you from turning on a mixture of 100% nitrous oxide.
Someone could have mixed up the tanks that supply the hospital lines
How are oxygen, nitrous oxide, and air gases that are used in anesthesia typically delivered to the anesthesia machine? At what pressure must these gases be delivered for proper function of the anesthesia machine?
Typically delivered via pipeline system or gas cylinders. Oxygen at 45 psi, nitrous oxide at 45 psi
How is the delivery of erroneous gases to the anesthesia machine minimized?
Diameter Index Safety System (DISS). Safety system on pipeline systems to prevent improper connection of supply hoses. (does not prevent hypoxic gas mixture to patient)
What is the purpose of the cylinders of oxygen and nitrous oxide that are found on the back of the anesthesia machine?
In case of a pipeline failure
How is an erroneous hookup of a gas cylinder to the anesthesia machine minimized?
Pin index safety system PISS
What are the PISS numbers for Oxygen?
2,5
What are the PISS numbers for Nitrous?
3,5
How many liters are in a full oxygen tank?
660 L
What is the PSI of a full oxygen tank?
1900 psi
How many liters are in a full nitrous tank?
1590 L
What is the PSI of a full nitrous tank?
745 psi
How is the pressure of oxygen related to the volume of oxygen in an oxygen gas cylinder?
Pressure drops as oxygen volume drops
How is the pressure of nitrous oxide related to the volume of nitrous oxide in a nitrous oxide gas cylinder?
Pressure is 745 psig until about 400 L remaining, nitrous oxide is a liquified gas so pressure depends on the liquid’s vapor pressure and does not indicate the amount of gas remaining ONCE PRESSURE DROPS UNDER 745 psi REPLACE THE TANK
Why does atmospheric water vapor accumulate as frost on the outside surface of oxygen tanks and nitrous oxide tanks in use?
The can gets cold when sudden release of gas as pressure decreases. It tries to gain energy back from the environment to heat back up. Potential to cause frostbite. (more likely to occur in humid locations) Joule Thomson Effect
What is the purpose of flowmeters on an anesthesia machine?
To show the flow rate of gas being administered; precisely controls and measures gas flow to common gas outlet
Are flowmeters for various gases interchangeable?
No. specifically designed and calibrated for each gas
Why is the oxygen flowmeter the last flowmeter in a series on the anesthesia machine with respect to the direction in which the gas flows?
To prevent a hypoxic mixture, oxygen is the last gas to leave the machine and is closest to the common gas outlet. All gasses flow to the right; oxygen is furthest on the right.
What is the purpose of the oxygen flush valve?
A straight shot of oxygen from the common gas outlet bypassing vaporizers and flowmeters
What is the flow of oxygen delivered to the patient when the oxygen flush valve is depressed?
35 – 75 L/min
What is the risk of activating the oxygen flush valve during a mechanically delivered inspiration?
Barotrauma/ pneumothorax
Why do volatile anesthetics require placement in a vaporizer for their inhaled delivery to patients via the anesthesia machine?
To convert them from liquid to vapor.
What is the heat of vaporization?
The number of calories required at a specific temperature to convert 1 Gram of liquid to a vapor
What influence does temperature have on vapor pressure?
As temperature increases, more molecules enter vapor phase and vapor pressure increases
Why are contemporary vaporizers unsuitable for use with desflurane?
Desflurane has a high vapor pressure
Describe how contemporary vaporizers for volatile anesthetics are classified.
Based on their vapor pressure (high vapor pressure or lower vapor pressure)
What does the term agent-specific refer to?
Agent = Volatile anesthetic gas. Each vaporizer is pressure/temperature calibrated for that specific agent.
How does tipping of a vaporizer affect vaporizer output?
Excessive tipping can cause the liquid agent to enter the bypass chamber and can cause an output with extremely high agent vapor concentration
How is the delivery of two different volatile anesthetics to the same patient via the same anesthesia machine prevented?
Vaporizer Interlock Mechanism
What is the function of anesthetic breathing systems?
Deliver oxygen and anesthetic mixture to the patient and eliminate CO2 from the breathing circuit
How do anesthetic breathing systems impart resistance to the spontaneously ventilating patient?
Small diameter or long circuits, small ET tubes, LMAs, HMEs, unidirectional valves can all create resistance. Controlled vent modes when pt is trying to breathe can also increase resistance
What classifies an anesthesia breathing system as open?
No reservoir, no rebreathing
What classifies an anesthesia breathing system as semi-open?
Reservoir, no rebreathing
What classifies an anesthesia breathing system as semi-closed?
Reservoir, partial rebreathing
What classifies an anesthesia breathing system as closed?
Reservoir, complete rebreathing
What are the most commonly used anesthetic breathing systems?
Circle breathing systems
How does the circle system prevent rebreathing of carbon dioxide?
Unidirectional valves and CO2 absorbents
What is the most commonly used circle breathing system used in the United States?
Semiclosed system
What are some advantages of the semi-closed and closed circle systems?
They conserve heat and moisture efficiently. Economic use of anesthetic gases. Minimizes release of anesthetic gases into environment.
What are some disadvantages of the circle anesthetic breathing system?
Complex design (10+ different connections). Malfunction of unidirectional valves can result in life-threatening problems. Rebreathing, total occlusion of circuit if stuck shut.
What is the impact of the rebreathing of anesthetic gases in a semi-closed circle system?
Minimizes environmental impact of anesthetic gases on environment
What does dead space mean? Where is the dead space in the circle system?
Ventilation of structures that do not participate in gas exchange.
From the y piece to the patients lungs, including ETT, connectors, and valves.
What is advantageous about the corrugated tubing in the circle system?
Prevents kinking of the tube. Is sturdy but flexible
What are other names for the adjustable pressure-limiting (APL) valve?
Pop-off valve or adjustable pressure relief valve
What are the advantages of the reservoir bag on the circle system?
Prevents retrograde flow through the system
what is the vulnerable area of the anesthesia workstation and why?
the low-pressure circuit, it is most subject to breaks and leaks
where is the low pressure circuit located?
downstream from all anesthesia machine safety features except the oxygen analyzer (or, in some cases, the ratio controller), and it is the portion of the machine where a leak is most likely to go unrecognized if an inappropriate LPC leak test is performed
what should be checked for leaks before administering an anesthetic
the circle breathing system
when can internal vaporizer leaks be detected?
when the vaporizer is turned to the “on” position
what are the oxygen failure cutoff valves?
they help minimize the likelihood of delivery of a hypoxic gas mizture
when can Compound A be formed and why?
during sevoflurane anesthesia; inhaled anesthetics can interact with CO2 absorbents
what is the most common cylinder used in anesthesia?
E-cylinder
what are examples of non-liquefied gases?
oxygen, nitrogen, air, helium
what does a 3AA tank marking indicate?
steel
what does a 3AL tank marking indicate?
aluminum, MRI compatible
what temperature could cause a cylinder to explode?
> 57º C (~134º F)
what gas law applies to the function of the pressure relief valve?
Gay-Lussac’s law
increasing temperature = increasing pressure
what is the only true way to know how much N2O is in a tank?
weighing the tank
how should N2O be stored?
critical temp= 36º C (right above room temp)
what kind of thermal injury may arise from a N2O tank?
cold burn
what is the Joule Thomson effect?
cooling or freezing on the surface of a cylinder
what is the only monitor to detect low O2 concentrations?
the oxygen monitor on the machine; it is a high alert alarm
what part of the anesthesia machine drops the pressure to an operable level? what does it drop the PSI to?
the second-stage pressure regulator; 16 PSI
when does the oxygen failure safety valve shut off the flow of all other gases?
when the oxygen falls below the set limit, usually 20-25 PSI
how is the oxygen flow valve different from the others?
it is fluted, larger than other, protrudes further out
where does the low-pressure system begin?
at the second stage regulator
what is the PSI reduced to at the second stage regulator?
~16 PSI
how are the changes of a hypoxic mixture of gas minimized in the event of a gas leak?
oxygen is the furthest to the right so it is always delivered
what is a volatile agent?
an anesthetic agent which exists as a liquid at room temperature and evaporates easily for administration by inhalation
what does the bag/vent switch do?
it allows the user to either manually ventilate the patient, or utilize the mechanical ventilator
what happens if the APL valve is open too wide?
too much volume is allowed to escape and not enough is delivered to the patient
what are the final products of CO2 neutralization?
carbonates, water, and heat
when should the carbon dioxide absorbent canister be replaced?
when 50-70% of the granules have turned purple
define tidal volume
volume of gas entering or leaving the patient during the inspiratory or expiratory phase time