ANESTHESIA MACHINE
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Transcript ANESTHESIA MACHINE
PART 3: Breathing Circuit
The
system that brings the fresh gas from the
vaporizer to the patient and takes the expired
gases from the patient to the scavenger.
May
contain unidirectional valves, reservoir bag,
pop off valve, CO2 canister, negative pressure
relief valve, pressure manometer.
Non-rebreathing
System
Rebreathing System
Rebreathing System
up as a circle system exhaled gases are
recirculated and rebreathed by the patient
Set
New
Used
Can
fresh gas is also added in
for patients weighing >7kg
be used as a closed or semi-closed system
Begins
with the fresh gas inlet
Vaporizer
outlet port connects to the fresh gas inlet,
which connects to the inspiratory unidirectional valve
Rebreathing System: Closed
Pop-off
valve is completely closed!
Only
provides enough oxygen to meet metabolic
demands of the patient
Flow
rates (L/min) must be kept very low!!
The
volume of gas added to the circuit = the
volume of gas used by the patient
This
is very tricky to achieve and is therefore not
commonly used
Rebreathing System: Semi-Closed
Also
known as partial rebreathing system
Pop-off
This
valve is open or partially closed
system requires a scavenging system
because more oxygen than the patient needs is
being provided
Unidirectional Valves
One-way
valves that allow the flow of fresh gas to
enter the inhalation valve and exit the exhalation valve.
Valve is either a rigid disk or a flap that flutters as gas
flows past it
Inspiratory/Inhalation valve opens as patient inhales
Fresh gas enters the inspiratory breathing hose, then the ET
tube and then the patient’s lungs
Gas exchange occurs now = sleepy patient 02
CO2
CO2
and anesthetic gases are then exhaled and
travel up the expiratory breathing hose.
Flows through the unidirectional exhalation valve
This valve prevents the expired gases from traveling back to
the patient before the CO2 is removed.
Breathing Tubes for Rebreathing System
1. Y Tubes
Come
in large animal, small animal, and pediatric
Large
animal tubes can only be used on large animal
machines
2. Universal F-circuit
Come
in adult (green-blue) and pediatric (red)
Pediatric = patients 15-35 lbs
Adult = patients weight > 35 lbs
The
inspiratory tube is located within the expiratory
tube
Each connects to the machine separately at their respective
flutter valves
CO2 absorber
CO2 Absorber
Exhaled
gases flow out of the expiratory breathing tube and
into the CO2 canister
CO2 canisters usually contain calcium hydroxide granules that
selectively absorb CO2 from other gases breathed out.
Example: soda lime granules
“Exhausted” soda lime granules no longer absorb CO2.
patient breathes in CO2
CO2 Absorber
HOW DO I KNOW WHEN THE GRANULES ARE
EXHAUSTED?
Color change to violet, off-white or pink
depending on the brand.
CO2 saturated granules are hard and brittle, new
ones can be chipped and crumbled
Once color becomes abnormal, it is possible that
it changes back to normal within hours!
next, gas flows into the rebreathing bag
AND through the pop-off simultaneously
Reservoir Bag- aka rebreathing bag
Expandable bag that fills as gases enter the circuit
or as patient exhales
Deflates as patient inhales
Range in size from 0.5 L to 30 L; 1 L increments
Volume of bag should be minimally 60 mL/kg
*This is equal to 6 times their minimum tidal volume
Reservoir Bag Calculation
If
your patient weighs 15 lbs, how many mLs of
air should the bag hold?
How
many liters is this?
*Always round up to next highest bag
*If that size doesn’t work for your patient, switch it
out!
Reservoir Bag Functions
1)
Helps in determining correct ET tube placement
movement of bag with breaths = tube in
trachea (yay!)
2)
Allows assessment of respiratory rate and depth
Good
for when you can’t see your patient
Why can’t you see your patient?!
Allows manual ventilation of the patient
3)
Also known as “giving a breath” or “bagging”
Indications for Manual Ventilation
1.
Reverse atelectasis if present; prevent if not
Done by closing pop-off and gently squeezing bag
Performed once q 10 minutes = “sighing” patient
Removal of CO2 and anesthetic that builds up
when respirations have decreased in volume
Anesthetics decrease tidal volume up to 50%
Forcing fresh gas in stimulates gas exchange
in the alveoli
3. Assist or control ventilation – especially if in
respiratory arrest or “deciding not to breathe”
IPPV
2.
Is Your Reservoir Bag the Right Size?
Bags
should consistently be ~ ¾ full upon exhalation
If bag is going from over-inflated to flat =
is too small and doesn’t hold enough oxygen
patient won’t be able to fully inflate lungs on inhalation
Bag
AND
Bag will overinflate on exhalation increases
pressure in the circuit
If bag is flat during respirations (under-inflated) =
is too big will not see movements with each
breath and wasted space in circuit
Bag
Pressure Manometer
Measures
pressure of gas within the breathing
circuit this includes the patient’s lungs
Unit
is in cm H20
Should
read between 0-2 cm H2O during
normal respirations
Pressure
How
increases as system is closed
do we close the circle and why?
Gauge
animals!
Watch
should never exceed 20 CM H20 in small
manometer while “bagging” patient
Pop-off Valve - aka pressure relief valve, exhaust valve
Always
kept open for semi-closed system
Allows
exhaled gas to leave the breathing
circuit and be scavenged
Prevents
the build-up of excess gas or
pressure within the circuit.
If
the pressure were allowed to build up
(forgot to open pop-off valve), the alveoli in
the lungs could rupture!
Pop-off Valve
The
degree that the pop off valve is opened
changes the flow rate and how full the reservoir
bag is. (semi-closed system)
If
you see your reservoir bag unintentionally
expanding very quickly- check pop-off!
Only close the pop-off valve when you are
currently providing breaths for the patient
Must
be opened between breaths
Negative Pressure Release Valve
aka Air Intake Valve
Special
feature activated in emergencies
Indicated
by a completely empty reservoir bag
1. When an active scavenging system is utilized, if
negative pressure is detected in the circuit, this valve
opens and allows room air in.
Instances
when there is excessive suction
2. O2 flow rate is too low or the tank runs out of
oxygen
ALWAYS
keep an eye on your oxygen pressure gauge
*Better for the patient to breathe room air than no air