The Anesthesia Machine Flashcards
why should you not deliver anesthestic gas in air (21% O2)
would lead to hypoxemia due to hypoventilationa and V/Q mismatch by anesthetic itself
minimal acceptible range of O2
30-35% O2 (FiO2= 0.30-0.35)
what is the metabolic requirement for oxygen?
5-10 mL/kg/min
this would be the minimun O2 flow required
what are other medical gases
nitrous oxide
medical air
types of oxygen sources
cylinders
liquid (cryogenic oxygen)
oxygen concentrator
E- cylinders
usually single, attached directly to anesthesia machine via yoke
H-cylinders
often in banks, supply central O2
T/F clyniders are color coded
True
oxygen= green
nitrous oxide (N2O) = blue
medical air = yellow
T/F unsecured tanks may explode if dropped or falls over and can become a projectile
True!!
what can you do to avoid fire with tanks
clean oils from hands and tank
open cylinder valves slowly
open & close walve briefly before attaching to machine to remove dust from connecting port
T/F pressure in the breathing system is meansure in psi
False
measured in cmH2O, the cylinder is measured in psi
what are pressure gauges used to measure
cylinder pressures
pipeline pressures
anesthetic machine working pressures
pressure within the breathing system
what part of the system is in low pressure
between flowmeter output and common gas outlet
breathing system (= pressre in patient’s lungs)
what is the capacity of an E-cylinder
660L (know this!!)
both E and H cylinders are filled to:
2200 psi (know this!!)
how can you calculate remaining O2 in the tank
how can you gifure out how many minutes of O2 are left
T/F N20 exisits in both a gaseous an dliquid form in the tank
True
T/F it is NOT possible to calculate amount of N2O gas remaining based on pressure
True
gauge only reads the gas pressure
what are some of the safety systems in place
color-coded tanks
labelling
diameter index safety system
pin index safety system
quick connectors
what is the diameter index safety system
non-interchangeable, gas specific threaded connection system
used universally by all equipment and cylinder manufacturers
what is the pin index safety system
gas-specific pin patterns that only allow connections bewteen the appropriate cylinder yokes and e tanks
characteristics of quick connectors
manufacturer-specific
facilitate rapid connecting and disconnecting of gas hoses
useful for multipurpose work areas
what does the regulator/pressure-reducing valve
decreases tank pressure to a safe working pressure (≈50 psi) which is supplied to flowmeter
prevents pressure fluctuations as the tank empties
flowmeter
controls rate of gas flow through the vaporizer (L/min)
gas enters at bottom at 50 psi and exits the top at 15 psi
the single/double taper flowmeter is more accurate at lower gas flows
Double-taper
T/F flowmeters are calibrated for 760 mmHg and 20ºC
True
where do you read the flow?
middle of the ball
top of the bobbin
T/F flowmeters are gas-specific
True
O2 flowmeter is NOT accurate if used for N2O or medical air
if there are multiple flowmeters where would the O2 be located
the far right (downstream of all other gases)
prevent delivery of a hypoxic gas mixture
in a mixed gas set up the N2O is set to 6L and the O2 set to 1L, is there sufficient O2 flow going the patient
No!!!
1L O2 + 6L N2O
02 = 1/7 = 14% (minimum is 35%)
This would be a hypoxic mixture = fatal
T/F the quick flush bypasses the vaporizer and delivers O2 with no anesthetic gas
True
dilutes gas in the circuit
when should the quick flush be used
quickly decrease anesthic gas % in the circuit (emergency, recovery)
Remember: disconnect patient from cicuit before using quick flush→ can resulti n dangerous increases in breathing circuit pressures
what is a possible complication of the quick flush
pneumothorax
small circuit, high pressure, small patient
what do anesthetic vaporizers do
change liquid anesthetic into vapor
deliver selected % of anesthetic vapor to fresh (common) gas outlet
vapor
gasesous state of substance that is liquid at ambient temp and pressure
halothane, isoflurane, sevoflurane, desflurane
gas
exists in gaseous state at ambent T and P
N20, Xenon
vapor pressure
pressure exerted by vapor molecules when liquid and vapor phases are in equilibrium
T/F vapor pressure is dependent on temperature
True
increases with increases temperature, inversely related to boiling point
saturated vapor pressue
maximum administration percentage
vapor pressure/barometric pressure
characteristics of modern vaporizers
agent-specific
concentration-calibrated
variable-bypass
flow-over
out-of circuit
high resistance
compensated for temp, flow and back-pressure
variable-bypass system
fresh gas flows over a reservoir of liquid anesthetic and mixes wit carrier gas
vaporizers out of circuit (VOC)
carrier gas is from flowmeter
anesthetic % is known - percision vaporizer
vaporizers in circuit (VIC)
not currently recommended
cannot produce known anesthetic gas %
not temperature compensated
non-precision
modern vaporizers compensate for:
temperature bewteen 15-35º C
flow rate between 0.5 and 10 L/min
back pressure associated with positve pressure ventilation and ise of flush valve
how is temperature compensation achieved
using materials that are efficient heat conductors
mechanical thermocompensation systems: has thermal element mode of heat sensitive metal that reliably expands and contracts based on temp
how is flow rate compensation achieved by
saturation of gas moving through vaporizing chamber
use of wicks, baffles, and spiral tracks that facilitate vaporization
back pressure
can occur during positive pressure ventilation or use of the flush valve
may increase vaporizer output of compensation mechanisms not present
vaporizers have mechanism to prevent
how are vaporizers filled
using screw-cap port or agent-specific keyed filler port
characteristics of vaporizers
require no external power (except desflurane)
routine maintenance is required and must be performed by a qualified technician
mounted on a “back bar” on the machine
cannot be tipped-must be emptied before transporting
what can happen if vaporizer is filled with wrong agent
depends on vapor pressure and petency of each agent
iso in sevo vaporizer could produce a leathal concentration
what should you do if you put the wrong agent on the vaporizer
drain and run 1 L/min O2 until completely dry
what would happen if vaporizer was tipped
anesthetic may enter the bypass channel and deliver a high concentration
run 1 L/min O2 through machine with vaporizer off to fix
what is the common gas out
where gas exits the vaporizer
where is the common gas outlet connected
by a hose to the fresh gas inlet - must be connected so fresh gas flows to the breathing circuit
connects to either rebreathing or non-rebreathing system
