Midterm Flashcards
What is PSIg?
Pounds per square inch gauge
- Diff b/t measured pressure and surrounding atmospheric pressure
- Most gauges read 0 at atmospheric pressure
What is PSIa?
Pounds per Square Inch Absolute
- Based on reference point of 0 pressure for a perfect vacuum
- PSIg + local atmospheric pressure (14.7 psi)
What regulatory agency enforces medical gas purity?
FDA
What agency regulates how gas cylinders are manufactured, labeled, filled, transported, stored & disposed of?
Dept. of Transportation (DOT)
What are the 5 regulatory agencies associated with anesthesia gas?
FDA
DOT
United States Pharmacopoeia (USP)
Nat’l Fire Protection Agency (NFPA)
Compressed Gas Associated (CGA)
What gases are used in anesthesia?
Oxygen (O2)
Air
Nitrous Oxide (N2O)
Helium (He)
Nitrogen (N2)
Nitric Oxide (NO)
Carbon Dioxide (CO2)
What are the gases in the atmosphere (air)?
- Nitrogen N2 - (28.01 - 78%)
- Oxygen O2 (32 - 21%)
- Argon Ar - (40 - 0.934%)
- Carbon Dioxide CO2 - (44 - 0.031%)
- Neon Ne - (20 - 0.0018)
- Helium He - (4 - 0.000524%)
- Krypton Kr - (84 - 0.000114)
- Hydrogen H2 - (1.0079 - 0.00005)
- Xenon Xe - (131 - 0.0000087)
For what gases are cylinders the primary source of gas?
Helium
Heliox
CO2
Are index pins located on the yoke or the cylinder?
The yoke
The cylinder contains the pin holes
What are the steps to install an E cylinder?
- Place cylinder gasket over the yoke inlet
- Align holes in the cylinder valve with the pins on the yoke
- Push the cylinder forward and into the yoke
- Rotate the yoke arm upwards and over until thearm engages w/ the other side of the yoke
- Turn the T-handle clockwise until it is tight and holds the cylinder firmly in place
- To open cylinder, turn valve at least 1-2 turns counterclockwise using a cylinder wrench
Where are the pipeline’s regulators located?
The cylinder’s regulators?
- Pipeline: in the wall
- Cylinder: in machine (behind yokes)
What is the primary regulator?
The cylinder regulator (located in the machine behind the yoke)
What is the pressure of the primary regulator?
45 psi
What is the pressure of the pressure relief valve?
75 psi
What is the E-cylinder capacity (L) and pressure (PSIg) of:
Air
CO2
He
HeO2
N2
N2O
O2
Air: 625 / 1900
CO2: 1590 / 838
He: 500 / 1600
HeO2: 500 / +
N2: 610 / 1900
N2O: 1590 / 745
O2: 660 / 2200
What are the phases and US & Internat’l color codes for:
O2
Air
N2O
He
Heliox
CO2
N2
O2: Gas; Green / White
Air: Gas; Yellow / White & Black
N2O: Gas/Liquid; Blue / Blue
He: Gas; Brown / Brown
Heliox: Gas; Brown & Green / Brown & White
CO2: Gas/Liquid; Gray / Gray
N2: Gas; Black / Black
How do you calculate total O2 consumption?
Total O2 consumption = Fresh Gas Flow (FGF) + Minute Ventilation (VE)
Ex:
FGF: 2 L/min
Tidal Vol: 0.7 L
RR: 10 bpm
VE = Tidal Vol. x RR = 0.7 L x 10 bpm = 7 L/min
Total O2 consumption: 2 L/min + 7 L/min = 9 L/min
How do you calculate time left in an E-cylinder?
O2 Time Remaining = Residual / Consumption
Ex:
Residual: 225 L
Consumption: 9 L/min
Time remaining = 225 / 9 = 25 mins.
What is pipeline pressure?
50 PSIg
What are pipeline supply sources?
Oxygen
medical air
N2O (held in tanks)
What is the cylinder’s index safety system?
What is the pipeline’s index safety system?
Cylinder: PISS (Pin Index Safety System)
Pipeline: DISS (Diameter Index Safety System)
Where are the connectors for the DISS?
DISS connector is on the side going to the machine.
Quick connect or DISS (variable) is on the side going to the wall.
What is the purpose of shutoff valves in the pipeline?
What are the types of shutoff valves?
Isolate specific piping system areas w/o turning off the entire system
Types: Manual (for a room)
Service (for an area)
What is the master alarm system in a pipeline?
- Monitors the central supply & distributiion system for all gases
- Signals changes in pressure, supply changeovers & supply/reserve depletion
What is the area (local) alarm system in a pipeline?
- Monitors a specific area
- Signals pressure changes 20% above/below normal operating pressure
What are the functions of the anesthesia machine?
- Receive gases from central supply system or pressurized cylinders
- Control the flow of desired gases & reduce their pressure
- Measure a precise amount of gases & load them with anesthetic vapors
- Provide gas to patient for breathing
- Provide monitoring & safety features
What are the Datex-Ohmeda machines?
Excel
Aestiva
Aisys
Avance
What are the Drager medical machines?
Apollo
Fabius GS
What are the anesthesia machine standards from 1979, 1988, and 1999?
- 1979 - ANSI Z79.8
- Est. minimum standards for design, performance, safety
- 1988 - ASTM F1161.88
- Added pre-use checkout, calibrated vaporizers, O2 analyzer, prioritized alarms, alarms enabled by a master switch, airway pressure monitoring, volume monitoring, & capnography
- 1999 - ASTM F1850-00
- Addressed workstation of the future
What are the high pressure components in the machine?
Hanger yoke (incl. filter and unidirectional valve)
Yoke block
Cylinder pressure gauge
Cylinder pressure regulators
What are the intermediate pressure components in the machine?
- The intermediate pressure system receives gases from the pipeline inlet or the pressure regulator (cylinder)
- Intermediate pressure = 37-55 psi
- This is pipeline pressure or the pressure after cylinder regulator
- Components:
- Pipeline inlets and pressure gauges
- Gas power outlet
- Master switch (pneumatic component)
- O2 flush valve
- O2 pressure failure device (fail-safe) & alarm
- O2 and N2O 2nd stage pressure regulators
- Flowmeter valves
What is the function of the gas power outlet?
It is a gas source for the ventilator.
One or more gas power (auxiliary gas) outlets may be present on an anesthesia machine. It may serve as the source of driving gas for the anesthesia ventilator or to supply gas for a jet ventilator. Either oxygen or air may be used.
What parts of the machine are still active when the machine is turned OFF?
O2 Flush
Gas Power Outlet
Electrical Outlets on the back of the machine
Battery recharging circuitry
Suction
Auxiliary O2
What happens when the machine is in STANDBY?
In the STANDBY position:
- No gas can flow to the patient
- No electrical power goes to the Ventilator, Display, or CPU
- O2 Flush is still available provided an oxygen supply is connected
- Electrical outlets (if equipped) are still active
- Battery will recharge
What happens when the machine is in the ON position?
When the Switch is turned to the ON position ( l ) the following occur:
- Oxygen is allowed to flow from the Main Output Manifold to the oxygen flowmeter
- Air is allowed to flow from the Main Output Manifold to the Air flowmeter
- Electricity flows to the components of the machine requiring electrical power, such as the ventilator, the display, & the CPU
O2 Flush Valve
- Directs a high unmetered flow (35-75 L/min) directly to the common gas outlet
- Receives gas from the pipeline inlet or cylinder pressure regulator
- Required by standards to be operable w/ 1 hand
Caution: pressure may be transmitted to other parts of the machine
O2 Fail Safe Device / Alarm
- Device that shuts off or proportionally decreases all gases except oxygen or alarms when oxygen pressure has fallen to a dangerous level (usually <30 psig)
- Depends on pressure, not flow
- 2 separate components, 2 sep. pressures
- Relief valve is 75 psi
How does the O2 Fail-Safe Device / Alarm work on the Datex-Ohmeda machines?
- Alarm activated when O2 pressure < 30 psi
- Gas flows stopped if O2 pressure <20 psi
- If alarm starts, turn on cylinder b/c it goes off if you don’t have enough or have run out of O2
- The Excel whistles when you turn it on b/c pressure is going from 0 to 30. It whistles when you turn it off b/c pressure is going from 30 to 0. Excel will turn off other gases (air, N2O) if O2 supply goes out
How does the O2 Fail-Safe Device / Alarm work on the Drager?
N2O flow is decreased proportionally with O2 pressure
When is the O2 Fail-Safe Device / Alarm activated?
When O2 pressure < 30 PSIg
What is the secondary pressure regulator?
- Reduce intermediate pressure to low pressure (from 50 –> 20 psiO2 and 38 psiN2O)
- Decrease pressure fluctuations from the pipeline
How does the flow control valve operate?
- Turning the flow control knob counterclockwise moves the needle valve back & away from its seat to open a channel for the flow of gas into the flowtube.
- Turning the knob clockwise closes the space between the needle valve & its seat.
- O2 knob must be fluted and be as large or larger than other knobs. It must look and feel different than the other knobs
What are the low pressure components in the machine?
- Hypoxic guard / proportioning systems
- Flowmeter tubes
- Vaporizers
- Check valves (if present)
- Common gas outlet
- Starts just after the flow control valves. Pressure is slightly above atmospheric
What are the mechanical and pneumatic components of the hypoxic guard system?
- Pneumatic:
- Secondary Regulators
- Mechanical:
- Chain
- The kick-in tab makes the clicking sound
- The kick-in tab must engage with the stop tab to work properly
- If you get above the 25% and turn down just N2O, you will disengage the stop screw
- Only on the Excell machine
What is the function of the common gas outlet?
- Receive all gases and vapors from the machine
- Deliver them to breathing system
- This is a frequent place for circuit disconnection
What was the first anesthesia delivery system?
Ether soaked rag
Done by Dr. Crawford Long March 30, 1842
What is pipeline pressure? Cylinder Pressure?
Pipeline: 50 PSIg
Cylinder: 45 PSIg
Which gases have the highest and lowest Blood/Gas ratio?
Blood/Brain ratio?
Blood/Gas:
- Highest: Iso - 1.4
- Lowest: Des - 0.42
- The higher the #, the longer it takes to work
Blood/Brain:
- Highest: Iso - 2.6
- Lowest: Des - 1.3
- The higher the #, the more potent
What is the purpose of the gas reservoir bag?
Provides a place for gas to accumulate
What is the purpose of the APL valve?
Provides ability to generate positive pressure in circuit
What drives the bellows up and down?
Drive gas pushes bellows down
Expired gas from pt. pushes bellows up
What are the types of CO2 absorbers?
What are the indications that they need to be changed?
Soda Lime and Baralyme
CO2 in inspired gases, color change and heat in canisters
What is the most common type of scavenging?
Closed interface w/ active scavenging
What are the required safety features in an anesthesia machine?
DISS
PISS
Low O2 pressure alarm
Hypoxic Guard
O2 failure safety device
O2 enters common manifold downstream to other gases
O2 concentration monitor and alarm
Automatically enabled essential alarms and monitors
Vaporizer interlock device
Capnography and anesth. gas measurement
O2 flush that doesn’t pass through vaporizers
Breathing circuit pressure monitor and alarm
Exhaled volume monitor
Pulse ox, EKG, and BP monitoring
Mechanical Ventilator
Scavenging system
Step 1 of machine checkout
Verify backup ventilation equipment (AMBU bag) is available and functioning
AMBU bag is the only way of continuing positive pressure ventilation
What are the steps and reasons of the machine checkout?
- Verify backup ventilation and equipment
- AMBU bag is only way to deliver pos. press. vent.
- Check O2 cylinder supply
- It is the backup supply
- Also, so low O2 supply alarm alerts you
- Check central pipeline supplies (50 PSI)
- Ensure adequate gas supply
- Check initial status of low press. system (everything OFF)
- Perform leak check of low pressure system
- Creates vacuum to see if there are cracks in flowmeter tubes / vaporizers
- Turn on machine
- Test flowmeters
- Ensure floats don’t get stuck
- Hypoxic guard mechanism working
- Adjust and check scavenging system
- Loose or improperly adjusted vacuum will release waste gases into OR
- Broken neg. pressure valve will allow excessive vacuum and create subatmospheric press.
- Broken pos. pressure valve will cause buildup of waste gases.
- Calibrate O2 monitor
- Don’t want hypoxic gas mixture
- Test alarm
- Check initial status of breathing system
- Improperly attached circuit can cause vent. problems
- Exhausted CO2 absorbent causes rebreathing
- Absorbent change may cause circuit leak
- Perform breathing system leak check
- Closing APL valve allows pressure to build up in circuit while using O2 flush creates high pressure
- Gas will escape thru leak under high press.
- You can measure amt of leak using FGF
- Test ventilation systems and unidirectional valves
- High gas flows will hide a leak
- Stuck insp. valve increases press. in machine
- Stuck exp. valve increases press. in pt’s lungs
- Check capnometer
- Check final status of machine
What is Peak Insp. Pressure (PIP) / Peak Airway Pressure (PAP)?
The pressure measured by the ventilator in the major airways.
Should be kept under 40 cmH2O
Strongly reflects airway resistance
What is plateau pressure?
Positive press. applied to small airways and alveoli
Goal is to keep <30 cmH2O b/c excessive alveoli stretch is thought to be a cause of ventilator-induced lung injury
Usually 25% of insp. time
What is peak flow?
Determines the rate of tidal volume delivery to the patient during mandatory volume control breaths
Affects I:E ratio adn peak pressure
What is Volume Control Vent.?
What are the Independent and Dependent Variables?
Tidal volume is preset and the resultant airway pressure is a function of lung compliance and other factors
Independent Variables:
- Tidal Vol.
- RR
- I:E ratio
- FiO2
- PEEP
Dependent Variables:
- PIP
- Plateau Press.
What are the advantages and disadvantages of VCV?
Advantages:
- Guaranteed min. vent.
- May help lung compliance in certain surgeries
Disadvantages:
- Pt. doesn’t trigger breath, but can see patient effort in capnogram
- May need to reduce tidal vol. if you get high PIP/ PAP
What is Pressure Control Ventilation?
What are the independent and dependent variables?
PAP is preset and the delivered tidal vol. is a product of lung compliance and other factors
Independent Variables:
- Insp. Pressure
- RR
- I:E ratio
- FiO2
- PEEP
Dependent:
- Tidal Vol.
What are the advantages and disadvantages of PCV?
Advantages:
- Reduced vent.-induced lung injury b/c able to limit PIP
- Improved gas distribution b/c uses decelerating flow
- More rapid improvement in lung compliance and oxygenation compared to VCV
- Better method to use if you’re having problems ventilating the patient
Disadvantages:
- Does not guarantee minute vent.
PIP vs. Plateau Pressure in VCV and PCV
VCV:
- PIP is determined from tidal volume set
- Plateau Press. determined by applying an inspir. hold
PCV:
- PIP usually the same as Plateau Press. b/c of how breath is delivered
- There is an inherent inspir. pause
What is Pressure Support Ventilation?
What are the independent and dependent variables?
Spontaneous vent. mode that provides constant pressure once patient inspir. effort is sensed.
Independent:
- Support Press.
- Inspir. Time
- Flow Trigger
- FiO2
- PEEP
Dependent:
- Tidal Vol.
- RR
What are the advantages and disadvantages of PSV?
Advantages:
- Able to have patient breathe spontaneously and not fight the ventilator
- Able to augment tidal vol.
- Able to adjust ETCO2 w/ support press.
Disadvantages:
- Requires pt. to be breathing spontaneously
- Can’t control RR
What is SIMV?
What are the independent and dependent variables?
Breaths given at preset time intervals.
Pt. can breathe spontaneously b/t the ventilator breaths
Ventilator will not give a breath if the pt. inspires at the same instant
Independent Variables:
- Tidal Vol.
- RR
- I:E ratio
- FiO2
- Pressure Support Level
- PEEP
Dependent Variables
- PIP
- Plateau Press.
What are the advantages and disadvantages of SIMV?
Advantages:
- Can be used as a way to start building up CO2
- Back up mode for PSV
Disadvantages
- May confuse pt’s brain b/c not physiological
Ventilator Settings for:
Tidal Vol.
RR
VE
Tidal Volume:
10-15 mL/kg (adults)
6-10 mL/kg (infants, children, COPD)
RR: 10 initial
Minute Ventilation: Tidal Vol x RR
Men: 4 x BSA
Women: 3.5 x BSA
In what ventilator setting can you use Inspiratory Pause?
VCV
Takes time from inspiration
What is auto-PEEP and what are the indications?
Air trapping in the lungs b/c of insufficient exhalation time
Signs:
Non-zero end expiratory pressure
Increasing PIP/PAP
