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