Lecture 3: The Anesthesia Machine (Exam 1) Flashcards
Labels the parts of the machine
Describe G & H cylinders
- Compressed gas in cylinders
- Set up as a central supply system
- Usually 2 banks (each containing 1 day’s supply) are connected to a common manifold that converts them into one continuous supply
- Pressure regulator ensure gas piped out @ 50-55 psi
Describe cryogenic liquid supply
- Large liquid oxygen containers installed @ facilities that have a fairly constant demand
- Liquid kept @ -297 degree F to prevent evaporation then O2 drawn as req & passed through heater to increase temp & raise pressure
Describe an oxygen concentrator
- Increases O2 concentration by absorbing nitrogen onto a molecular sieve & allows O2 & trace gases to pass through resulting in O2 concentration of 90 - 96%
- Can save money compared to liquid or cylinder oxygen sources
- Maintenance required
- Takes a few mins to reach max concentration of 96%
- Produces gas lows that would be acceptable for SA anesthesia patients
Describe an oxygen cylinder
- Filled & discharged through through valve
- The port is the exit point sealed w/ a washer or gasket over the nipple prior to attaching the cylinder to the yoke
- The conical depression is opposite side of the port & receives the retaining screw from the yolk
- How is the oxygen cylinder opened
- A handle or cylinder wrench is used to open the valve
- Open the valve slowly b/c rapid recompression of gas generates heat which causes a adiabatic process (+ dust & grease = flash fire or explosion)
What is the capacity (L) & the pressure (psi) of the E oxygen common cylinder
- Capacity = 660
- Pressure = 2200
What is the capacity (L) & the pressure (psi) of the H oxygen common cylinder
- Capacity = 6900
- Pressure = 2200
What safety measures must be taken w/ oxygen cylinder
- Inspected & tested @ least every 5 years
- Oxygen top is green while N2O is a blue top to prevent the connection of the wrong gas
- Pin index safety systems
- Diameter index safety system
- Manufacturer specific quick connector
Describe the regulator
- Reduces the gas pressure from the cylinder (or other source) to a usable level of a constant 50 psi
- Specific for gas tank size (E or H)
- Terminates in a gas specific male DISS fitting
Describe the cylinder pressure gauge
- Must be installed downstream of each pressure regulator
- Calibrated in psi
- Allows user to calculate remaining liter in the tank or pipeline pressure
Label the green & red arrow
- Green = cylinder pressure gauge
- Red = Regulator
Calculate for x
When should a cylinder be changed
When pressure is < 500 psi
How many liters of oxygen are left in this E tank
1500 psi
Explain the flush valve
- Receives O2 from the pipeline inlet or cylinder pressure regulator & directs a high unmetered flow directly to the common gas outlet
- 35 to 75 L/min when activated -> possible barotrauma so never use when connected to a non-breathing system
Describe the flow meter
- Indicates rate of flow o gas passing through them
- Turn the control knob counterclockwise to increase flow & clockwise to decrease flow (do not over tighten)
- Gas specific calibration
- Reliable vaporizer output when flowmeter set btw/ 500 - 2000 mL/min so don’t set the flowmeter lower then .5 L/min w/ a rebreathing system
What happens as the height increase in a flow meter
More gas flows b/c the tube in the flow meter is internally tapered (the smallest diameter is @ the bottom)
How many L/min of oxygen is being delivered w/ this flow meter setting
1.5 L/min
Describe the unidirectional valves
- Only present on a rebreathing system
- Allows gases to only travel in on direction
- Has an inspiratory valve & expiratory valve
What are the disadvantages of the unidirectional valves
- Increases resistance to breathing
- If one or both valves are leaky then the px will rebreathe CO2
Describe the vaporizer
A device that changes a liquid anesthetic agent into its vapor & adds a controlled amount of that vapor to the fresh gas flow going into the patients breathing system
What designs are shared among modern vaporizers
- Gas specific
- Concentration calibrated
- Variable bypass
- Flow-over vaporization method
- Temperature compensation
Where are the concentration calibrated vaporizers are located
Btw/ the flowmeter & common gas outlet
How is the vaporizer output controlled
By a dial/knob that is calibrated in volumes %
How does the vaporizer dilute the saturator vapor pressure
By splitting the gas flow that passes through the vaporizer into the bypass to the vaporizer outlet & the vaporizing chamber
How is the efficiency of vaporization enhanced
Stream of gas passes over the surface of the liquid which increase the surface area of the gas-liquid interface
What is used to adjust flow through the vaporizing chamber when temp varies
Bimetallic strip of valves
What are some vaporizer hazards
- Two vaporizers on the machine turned on @ the same time (interlock systems will prevent this)
- If the vaporizer is tipped, overfilled, or filled w/ the wrong agent consult the manufacturer for the best recommendations
What should be done if the vaporizer is tipped
- Should be flushed w/ a high O2 flow rate for the max time recommended by manufacturer
- The vaporizer should be emptied prior to transport let in upright position, & dial set to the 0 position
What happens is the vaporizer is overfilled
- May deliver lethal concentration
- Cause vaporizer failure w/ zero output
What is done if the vaporizer is filled with the wrong agent
- Must be completely drained & all liquid discarded
- O2 should be run through until no agent is detected
What does purple & yellow stand for on the bottle of liquid anesthetic
- Purple = isoflurane
- Yellow = sevoflurane
What does the common/fresh gas inlet & outlet do
Receives all gases & vapors from the machine & delivers the mixture to the breathing system
What should we make sure is secured
- The hose that connects to the breathing system can be different on every machine, but make sure the connection is secure when setting up the machine for the px
Why should the oxygen flush valve never be activated when using a non-rebreathing system
Attaches closer to the px
What is this
Common/fresh gas inlet
What is the reservoir bag
- Inspiratory reservoir of oxygen (+/- anesthetic gases) for the px to be able to take 5 or 6 breaths from
- Used to monitor the frequency of the respiratory rate & compliance of the px’s pulmonary system during assisted ventilation
- Manual ventilation by the anesthetist from squeezing the bag up to 20 cm H2O while occluding the APL valve momentarily or replaced by a ventilator hose during mechanical ventilation
What equation is used to determine the size of the reservoir bag for a px
Calculate the answer & determine the bag size needed
- 1250 mL
- 2 L bag
What size reservoir bag would you select for a 35 lb dog
2 L
What is the adjustable pressure limiting (“pop-off”) valve (APL)
- User adjustable valve that releases gases to a scavenging system
- Used to control pressure in the breathing system
When should the APL valve be closed
Transiently close APL to deliver manual ventilation to px (otherwise it must be kept open @ all times)
What are the top 3 killers
- Closed pop off valve
- Too little O2
- Too high vaporizer setting
List some safety concerns
- Improper cylinder storage
- Tipping over vaporizer
- Wrong inhalant in vaporizer
- Overfilling vaporizer
- Opening a cylinder too quickly & having dust or grease around the valve
- Using oxygen flush valve when attached to a small px
- O2 & N2O are flammable
- Taking a steel cylinder into a MRI room
How should cylinders be stored
- Cylinder valve, pressure regulator, or gauges should never come in contact w/ oils, grease, organic lubricants, rubber or combustible substances
- Valve kept closed @ all times unless cylinder is in use (use a protection cap when stored)
- Bleed all pressure from the system
- Store btw/ 20 to 130 degrees F away from heat duct
- Properly stored @ all times (never drop, drag, slide, or roll a cylinder)
What are some service & maintenance costs
- Trained & certified technician
- Routine maintenance usually 1 to 2 times/year
- Keep accurate records
List some safety feature upgrades
- Key fill adapters
- pop off occlusion valve
- Pressure relief valve
What are the steps to performing a machine leak test (“machine pressure check”)
- Make sure O2 flow meter is off
- Close the APL pop off valve
- Occlude the patient end of the Y-piece w/ a hand, finger, or syringe plunger
- Press the O2 flush button to pressurize the system to 30 cmH2O (non-rebreathing systems jus use a flowmeter to fill the system)
- Observe the pressure gauge for approx. 50 seconds
- Release the APL valve
- Remove occlusion from the Y-piece
What should be done if there is a leak observed in step 5 of the leak test
- Slowly titrate the O2 flow meter up to max of 300 mL/min
- If this the leak stop the machine & breathing system is acceptable to use
- If it takes > 300 mL/min of O2 to stop the leak the machine & breathing system should not be used until the source of the leak is IDed
