anesthesia machines Flashcards
absorber
canister (1-2)-source of leaks, will become dessicated–>won’t work
chemical carbon dioxide absorbent-all or part of exhaled CO2 is absorbed
made of calcium hydroxide, KOH, NaOH, LiOH
CO and compound A
flow rates: beginning
higher flows at the beginning of the procedure
“wash in”-two fators: gas flow rate & volume
3 time constants required to reach 95% of inspired conc
lower time constant with high flow and lower volume
flow rates: maintenance phase
close: flow rate=metabolic need, most economical, change happens slowly, higher vaporizer settings, close attention to volume in circuit, O2 delivery to patient, airway gas monitoring helpful
semi-closed: flow rate>metabolic need, flow rate<minute>
</minute>
advantages of non-rebreathing system
simple inexpensive, lightweight, easy to use
few moving parts
low resistance
low volume, high flows (time constant decreased)
no CO2 absorbent- no risk of toxic compounds
disadvantage to non-rebreathing systems
high fresh gas flow rate-expensive, not eco friendly
loss of heat and humidity
low volume-higher risk of volutrauma
5 basic function
source of oxygen
support ventialtion
delivers inhalants
removes exhaled CO2
removes inhalant anesthetics
basic components of anesthesia machine
gas source
pressure regulator
flowmeter
vaporizer
high pressure zone
cylinger
hanger yoke
high pressure hoses
pressure gauges
regulators
intermediate pressure zones
pipeline inlets
conduits from pipeline or regulators
flow control valve
oxygen flush
low pressure zones
conduits to vaporizers
vaporizers
conduits to breathing system
Cylinders (tanks)
E or H size
colors: Green-O2, Blue NO, Black N2, Yellow air, Gray CO2
permanent markings
general rules for cylinders
safe handling
no oils, grease, lubricants or combustibles
gas specific apparatus
20-130 degrees F
secure tanks upright or horizontally in bins or racks (E) or upright and chained to wal (H)
no dropping, dragging, sliding or rollling
crack the tank before fitting it to a machine
use washer
open cylinder slowly
close when not in use
remove empty tanks
how will the pressure drop in a cylinder with oxygen?
pressure decreases linearly as the volume decreases
how will the pressure drop in a cylinder with nitric oxide?
pressure will not start dropping until 75 to 80% of contents are used
how is the gas source connected to the machine?
tanks: hanger yokes or PISS (pin index safety system)
pipeline: quick connectors, DISS (diameter index safety system)
what do pressure regulators do?
reduce the high, variable pressures from the cylinder to lower and constant pressures more suitable for anesthesia machine
what does a flowmeter do?
allows for precise control of gases being delivered
what is the flowmeter composed of?
flow control valve
glass tube
scale
flow indicator
flow indicators
read at the top (in the middle for a ball)
should move freely (watch for rotation)
vaporizers
most inhaled anesthetics are liquids that must be converted into vapors before they can be used
vaporizers convert liquid into vapors and add a specific amount to the gas being delivered to the patient
concentration-calibrated, variable-bypass with temperature, flow and back pressure compensation are recommended
variable bypass vaporizer
fresh gas flows into the vaporizer
part directed through the vaporizing chamber, part bypassing it
gases mix before exiting the vaporizer giving the desired concentration
measured flow
gas is direted through the vaporizer and becomes fully saturated
second source of gas dilutes to desired concentration
calculations needed
not as reliable
method of vaporization
flow over
bubble through
injection
vaporizer in circuit
increased ventilation–>increased inspired anesthetic concentration
increase oxygen inflow–>decreased inspired anesthetic concentration
vaporizer out of circuit
increased ventilation –> decreased anesthetic comcentration
increased oxygen inflow–>increased inspired anesthetic concentration
precision vaporizers
recommended and most commonly used
variable bypass
flow-over or injection
out of circuit
flow and temperature compensation
agent specific
high resistance
output is controlled accurately by dial setting
relatively complex and expensive
require occasional maintenance
oxygen flush valve
gas derived from intermediate pressure system
bypasses the vaporizer
delivers a high flow rate of oxygen directly to patient’s breathing circuit
used to rapidly decrease the inhalant concentration in the breaking circuit
potential for barotrauma in small patients especially on non-rebreathing circuits
