Anesthesia Machine Flashcards
Noninterchangeable gas-specific connections to pipeline inlets (DISS) w/ pressure gauges, filter, & check valve
Purpose?
Prevent incorrect pipeline attachments;
detect failure, depletion, or fluctuation
Pin index safety system for cylinders w/ pressure gauges, and at least one oxygen cylinder
Purpose?
Prevent incorrect attachments; provide backup gas supply; detect depletion
Low oxygen pressure alarm
Purpose?
Detect oxygen supply failure at the common gas inlet
Minimum oxygen/nitrous oxide ratio controller device (hypoxic guard)
Purpose?
Prevent delivery of less than 21% O2
Oxygen must enter the common manifold downstream to other gases
Purpose?
Prevent hypoxia in event of proximal gas leak
Oxygen failure safety device (shut-off or proportioning device)
Purpose?
Prevent administration of nitrous oxide or other gases when the oxygen supply fails
Oxygen concentration monitor and alarm
Purpose?
Prevent administration of hypoxic gas mixtures in event of a low-pressure system leak; precisely measure oxygen concentration
Automatically enabled essential alarms & monitors (ex: oxygen concentration)
Purpose?
Prevent use of the machine without essential monitors
Vaporizer interlock device
Purpose?
Prevent simultaneous administration of more than one volatile agent
Capnography & anesthetic gas measurement
Purpose?
Guide ventilation; prevent anesthetic overdose; help reduce awareness
Oxygen flush mechanism that does not pass through vaporizers
Purpose?
Rapidly refill or flush the breathing circuit
Breathing circuit pressure monitor & alarm
Purpose?
Prevent pulmonary barotrauma and detect sustained positive, high peak, and negative airway pressures
Exhaled volume monitor
Purpose?
Assess ventilation & prevent hypo- or hyperventilation
Pulse oximetry, blood pressure, ECG monitoring
Purpose?
Provide minimal standard monitoring
Mechanical ventilator
Purpose?
Control alveolar ventilation more accurately and during muscle paralysis for prolonged periods
Backup battery
Purpose?
Provide temporary electrical power (>30 min) to monitors and alarms in event of power failure
Scavenger system
Purpose?
Prevent contamination of the OR w/ waste anesthetic gases
how gases and electrical power enter the machine
Supply
preparation of gases prior to delivery to the patient
processing
gases going to the pt and returning from pt, their control and monitoring
delivery
disposal of gases
disposal/scavenging
gas supplies connected to the machine
also includes cylinder of o2 on side of machine
high pressure system
blending of gases and volatile agent based on control settings
- also regulates high pressure to prevent barotrauma
- includes vaporizers
low pressure system
fresh gas mixture passes from machine to patient
breathing system
What psig should hospital pipeline gases show on the pressure guage?
50 to 55 psig
these prevent retrograde flow and leakage if pipeline supply is disconnected and cylinder supply is in use
check valves
What is blue hose
nitrous
what is green hose
oxygen
what is yellow hose
air
reserve supply of gases oxygen, nitrous oxide, and air
cylinder gas inlet
What does pressure regulator reduce pressure to in high pressure system
45 psig
occurs if two cylinders of the same gas are both open and gas flows from the higher pressure to lower pressure cylinder instead of going to the flowmeters
-check valve prevents this
transfilling
type of gauge where flexible tube within the gauge straightens when exposed to gas pressure, causing gear mechanism to move the needle pointer
bourdon type gauge
why do you need to bleed pressure to allow guage to read 0?
If 0 is not baseline, the gauge will only read pressures that are higher than the baseline
What does the second stage regulator decrease O2 pressure to?
16-20 psig
what does the second stage regulator decrease nitrous to?
32 psig
in tank nitrous is 745, then decreased to 50-55, then 32
- bypasses flowmeters and vaporizers
- delivers breath directly to breathing system at 50 psig (barotrauma!)
- delivers 35-75 L/min flow (max on flowmeters is 10)
- reinflates reservoir, bellows
O2 flush valve
controls gas flow though the flowmeter
includes a knob, needle valves, and an indicator float
flow control valves
tapered, calibrated to specific density and viscosity of gas, coated with conductive substance to minimize static electricity.
flow tubes, thorpe tubes
what is the ratio of nitrous to oxygen delivery?
3:1
managed by proportioning system
-link-25, chain link
pneumatic, mechanic control
dependent on 32 psig of nitrous and 16-20 psig of O2
oxygen ratio monitor controller
What is the minimal oxygen flow?
150 ml/min
meets basal metabolic O2 needs
Why are O2 flowmeters ALWAYS nearest to the vaporizers?
to minimize risk of hypoxic mixture being delivered if leak occurs in the flowmeters
where gases from different flowmeters mix together and have opportunity to enter into a vaporizer which is attached
manifold
supplies gas mixture to breathing system
common gas outlet, “fresh gas outlet”
Used in bag mode to deliver positive pressure breath.
0 = OPEN
-Do not go above 20 mmHg when bagging to prevent inflating stomach
Adjustable pressure limiting valve
APL or pop off valve
How much peep do anesthesia machines have intrinsically?
4 PEEP
vacuum (negative pressure) from hospital disposal system withdraws gas from the scavenging system
active system
slight positive pressure of excess gases in the machine moves it into the evacuation hose and into the disposal system
passive system
opens with too much pressure to vent waste gases into the room and helps prevent a positive pressure in the patient circuit
positive pressure relief valve
opens with too much suction to allow room air into the flow of waste gas to the vacuum source and helps prevent a negative pressure in the patient circuit
negative pressure relief valve
if vacuum not high enough, pressure will not back p into breathing system
positive pressure relief mechanism
if vacuum is too strong, the gases to be delivered to the pt will not be affected
negative pressure relief mechanism
during manual ventilation, when does gas enter the scavenging system?
when the peak pressure exceeds the opening pressure of the APL valve
when does gas enter scavenging system during mechanical ventilation?
during late exhalation and the expiratory pause after the ventilator bellows have returned to full position
When does gas enter during spontaneous ventilation?
during late exhalation and the expiratory pause after the reservoir bag is full.
- Go to oxygen flowmeter
- Go to O2 flush
- Activate oxygen pressure failure safety mechanism
- Activate oxygen low pressure alarm
- powers the mechanical ventilator bellows
five functions of oxygen
How can you defeat the anti-hypoxic safeguards?
- wrong gas in the O2 pipeline or cylinder
- defective pneumatics or mechanics
- leaks downstream of flow control valves
- inert third gas administration
- to provide oxygen
- to blend an anesthetic gas mixture
- to allow ventilation of pts lungs, whether spontaneous, assisted or controlled
primary purposes of anesthesia machine
What is patient ready?
APL valve open, flowmeter and vaporizers off, minimal flow 150, bag mode and mask on end of circuit
