Transcript BREATHING SYSTEMS - Dr. Roberta Dev Anand

BREATHING SYSTEMS
BREATHING VS.
NONREBREATHING SYSTEMS
RE-BREATHING
Also known as a circle system
Exhaled gases are re-circulated back to
the patient. After exhalation, they go
through the unidirectional valve, to the
CO2 canister and the reservoir bag, then
back through the inhalation valve where
they are combined with more fresh gas for
the patient to inhale.
BREATHING VS.
NON-REBREATHING SYSTEMS
Choose a re-breathing system for your
patient if the patient is >15lb (7kg)
Because re-breathing systems recycle
exhaled gases, the O2 flow rates are
relatively low.
When we recycle, we don’t have to use as
much oxygen or anesthetic gas.
Re-breathing Systems
 Depending on the position of the pop-off valve, we
can call a re-breathing system CLOSED OR SEMICLOSED
CLOSED- the pop-of valve is totally closed. All
gases exhaled by the patient remain in the circuit
and are re-circulated after the CO2 is absorbed
SEMI-CLOSED- the pop-off valve is open or
semi-closed. Some gases exhaled by the patient
remain in the circuit, some exit through the pop
off and into the scavenger
CLOSED
Total re-breathing
Low oxygen flow rate!
Pop off valve is closed
SEMI-CLOSED
aka partial re-breathing
Higher oxygen flow rate than closed
system
Pop off valve is open letting excess gases
be scavenged (in some cases, valve may
not be open ALL the way)
RE-BREATHING VS.
NON-REBREATHING SYSTEMS
NON-REBREATHING
 In a non-rebreathing system, oxygen flows from the tank
to the flowmeter and vaporizer, however the
unidirectional inhalation valve is bypassed. Fresh gas
enters a hose after the vaporizer and is inhaled by the
patient. Exhaled gases exit through a separate hose and
into a reservoir bag. There is no entry into the CO2
canister. The gases pass through the pop off valve and
into a scavenging system.
 Most anesthetic machines can be converted back and
forth from re-breathing to non-rebreathing systems
BREATHING VS. NONREBREATHING
SYSTEMS
NONREBREATHING
Choose a non-rebreathing system for your
patient if it weighs less than 15lb (7kg).
Little to no gas is recycled back to the
patient, so O2 flow rate are very high!
Since we are being wasteful and NOT recycling,
we have to use more oxygen and anesthetic gas
The pop-off valve should be all the way open or
partially open with a non-rebreathing system.
NON-REBREATHING SYSTEM
 ADVANTAGES:
Great for small patients (< 7 kg) as it offers very little
resistance to breathing.
Lighter weight than conventional tubing; creates less
drag on tube
 DISADVANTAGES:
More expensive as more gas is used.
Patients are more susceptible to heat loss without the
benefit of the tube within a tube.
NON-REBREATHING
 Commonly used Bain Co-axial
system
 Tube within a tube
Inner tube delivers fresh gas to the
patient. Outer tubing conducts gas
away from the patient and into a
reservoir bag. Since most of the gas
is scavenged and does not re-enter
the patient, the bag is used to
visualize respirations and facilitate
manual ventilation.
Incoming gases are warmed by
exhaled gases
Parameters
Nonrebreathing Rebreathing
CO2 absorption Not necessary
Must have
Anesthetic depth
change
Quickly
Slowly
Flow rates
High
Low
Cost
High
Low
Waste gas
High
Minimal
Pop off valve
Fully open
Open, Closed or
partially open
Heat and moisture
conservation
Poor
Good
Animal size
< 7 kg
>7 kg, unless pediatric
hoses are available
O2 FLOW RATES
Depends on the period of anesthesia and
the type of system being used
Generally, flow rates during induction and
recovery are higher because we are trying to
achieve a rapid change in anesthetic depth.
Chamber induction: 5 L/min
Mask induction:
animals <10kg = 1-3 L/min
 animals > 10kg = 3-5 L/min
O2 FLOW RATES
MAINTENANCE FLOW RATES
NONREBREATHING:
150-200ml/kg/min (ex: Bain Coaxial system)
400-600mL/kg/min (ex: Jackson-Rees)
WE COMMONLY USE 250 mL/kg/min at VTI (and
we will round up to at least 0.8 L/min)
REBREATHING
CLOSED: 5-10 mL/kg/min,
SEMICLOSED: 20-40 mL/kg/min
WE COMMONLY USE 40 mL/kg/min at VTI (and
will round up)
LEAK TEST
 TO BE PERFORMED BEFORE EVERY
ANESTHETIC PROCEDURE!
Close pop-off valve and cover the patient end of the
anesthetic tube
Push O2 flush button or turn on flow meter until bag
is distended and the pressure on the manometer
reads 30cm H20.
Turn O2 off and watch the manometer. If the
reading drops rapidly, bag deflates rapidly, or a
hissing sound is heard, leak is present. If there
were no leaks, the pressure would remain constant
for at least 30 seconds, despite the O2 being turned
off.
LEAK TEST CONT’D
Check the hoses, bag, attachments of machine
to be sure everything is properly placed
When test is over, reopen pop off valve and
squeeze the reservoir bag.
RESERVOIR BAGS
WEIGHT
0-3 kgs
4-7 kgs
8-15 kgs
16-50 kgs
51-150 kgs
BAG SIZE
½L
1L
2L
3L
5L