Anesthesia breathing systems ppt. Flashcards
all anesthesia breathing systems have 2 purposes. what are they?
delivery of O2/anesthestic gases
eliminatin of CO2
ALL breathing circuits create some degree of _______ to flow
resistance
Resistance to flow can be minimized by what 5 things
reducing the circuit’s length
increasing the diameter
avoiding the use of sharp bends (turbulent flow)
eliminating unnecessary valves
Maintaining laminar flow
who law describes that increasing the diameter can reduce resistance?
poiseuille
resistance is ___________ proportional to flow rate with laminar flow?
indirectly
resistance increases and flow decreases
for turbulent flow what is more important in relation to resistance and flow. density or viscosity?
density
(my rational the more dense = more turbulent)
resistance is proportional to __________ of flow rate (turbulent flow)
square
what type of flow is orderly movement of gas inside a “hose”
laminar flow
with laminar flow where does the gas move the fastest at?
what type of flow is seen with sudden narrowing or with branching of a tube?
turbulent flow
what is increased with turbulent flow??
resistance
Lmainar flow becomes turbulent when reynolds number is what
> 2000
Poiseuille’s Law follows what type of flow?
Laminar
formula for resistance
R= 8 n l / r4
R= resistance
n= viscsity
l=length
r=radius
an ex of resistance is: when you double the radius of the tube, it will decrease the resistance by how much
16 times
22= 16
Traditional attempts to classify breathing circuits combine ______ aspects with _______ characteristics
functional aspects (eg, extent of rebreathing)
Physical characteristics (eg, presence of valves)
Classifications of breathing systems are based on the presence or absence of what 4 things
- A gas reservoir bag
- rebreathing of exhaled gases
- Means to chemically neutralize CO2
- Unidirectional valves
what does the gas reservoir bag do?
provides gas for the moment during inspiratin where flow in the trachea is greater than fresh gas flow (FGF)
4 diferent classifications of breathing systems
- OPen
- Semiopen
- semiclosed
- Closed
what is the fuctions (2) of any breathing circuit?
deliver O2 and gases
Eliminate CO2
what are the 2 ways that the breathing circuit can eliminate CO2
washout with adequate FGF
or
by soda lime absorption
for the following tyes of breathing circuits, tell if they have a reservoir, if they allow rebreathing and give and example of each
Open
semiopen
Semiclosed
Closed
type Reservoir Rebreathing EX
_Open _ NO No Open gtt, insufflation, NC
Semiopen Yes No Non rebreathing circuit; circle @ high gas flow
Semiclosed Yes Yes (partial) Circle @ fresh gas flow less than MV
_Closed _ Yes Yes (complete) Circle @ extremly low FGF, with APL valve closed
an open gtt, insufflation, and nasal cannula are ex of wha type of breathing circuit?
Open
with the open breathing curcuits is there a reservoir? what abot rebreathing?
nope
and
nope
a non rebreathing circuit and a circle at high FGF is an ex of what type of breathing curcuit?
semiopen
with the semiopen curcuits is there a reservoir? what about rebreathing?
yes
and
no
A circle system at FGF less than MV is an example of what type of breathing circuit?
semiclosed
Does the semi closed circuits have a reservoir? what about rebreathing?
yes
and
yes (partial)
what type of breathing circuit is a circle at extremly low FGF, with APL valve closed?
Closed
with a closed breathing circuit is there a reservoir? what about rebreathing?
yes
and
yes (complete)
breathing systems classifications Open
reservior?
rebreathing?
neutralization of CO2?
Unidirectional Valves?
and give 2 ex?
reservior? NO
rebreathing? NO
neutralization of CO2? NO
Unidirectional Valves? NO
Ex
Nasal cannula
Open gtt ether
a way to remember open breathing circuits?
Think of it as anything where there is NO REBREATHING and NO SCAVENGING
Breathing system classification
Semiopen
reservior?
rebreathing?
neutralization of CO2?
Unidirectional Valves?
what is important about FGF?
three examples?
reservior? YES
rebreathing? NO
neutralization of CO2? NO
Unidirectional Valves? NO
what is important about FGF? the FGF needs to EXCEED MV (2-3 times MN to prevent rebreathing) MINIMUM FGF 5Lpm
Examples
- Mapleson A,B,C,D
- Bain
- Jackson-Rees
Breathing system classifications
Semiclosed
A type of what system?
reservior?
rebreathing?
neutralization of CO2?
Unidirectional Valves (if so how many and what are they)?
what is important about FGF?
Example?
A type of what system?“CIRCLE SYSTEM”
reservior? YES (ALWAYS)
rebreathing? PARTIAL (EXHALED GASES)
neutralization of CO2? YES (ALWAYS)
Unidirectional Valves (if so how many and what are they)? YES; 3, (INSPIRATORY, EXPIRATORY, APL)
what is important about FGF? FGF IS LESS THAN MV
Example?
- THE MACHINE WE USE EVERYDAY
Classification of breathing systems
CLOSED
reservior?
rebreathing?
neutralization of CO2?
Unidirectional Valves ?
Example/ SIDE NOTE?
reservior? YES (ALWAYS)
rebreathing? YES (TOTAL)
neutralization of CO2? YES (ALWAYS)
Unidirectional Valves ? YES (ALWAYS)
Example/SIDE NOTE?
WE DON’T USE THESE…. SUFFICE TO SAY YOU CAN DO THIS WITH THE MACHINES WE HAVE IF YOU KEEP THE FGF TO METABOLIC REQUIREMENT AROUNG 150ML/MIN (supply of O2, N2O, and VAA just matches pt’s requirement) IF PT SPONTANEOUSLY VENTILATING, APL VALVCE SHOULD BE CLOSED (no scavenging since no waste ⇒ total rebreathing)
All the retarded info you’ll need about nonrebreathing circuits!!!
(Just look at I don’t think it’s important and its alot of shit)
Mapleson classification-1954
- Mapleson D sill commonly used
- the modified Mapleson D is also called the bain. Arrangement of components are similar in both. The main difference is that the bain has the fresh gas hose inside the expiratory corrugated limb. unregnized kinking of the inner inspiratory hose will convert the expiratory outer hose into dead space.
- Mapleson F- better known as Jackson-Rees modificatin of Ayre’sT-piece
- used almost extensivly in children
- Very low resistance to breathing
- The degree of rebreathing is influenced by method of ventilation
- Adjustable overflow valve
- Delivery of FGF should be at least 2 x’s Minute volume
All non-rebreathing (NRB) circuits lack what 2 things?
- Unidirectional valves (insp and exp)
- soda lime CO2 absorption
with the NRB circuit (semiopen)the amount of rebreathing is highly dependent on what?
FGF (need high FGF to llow nonrebreathing)
with nonrebreathing circuits (simiopen) what makes the work of breathing low?
no unidiredctional valves or sodalime granules to create resistance
how do non-rebreathing circuits work?
- During EXPIRATION, FGF pushes exhaled gas down the expiratory limb, where it collects in the reservoir (breathing) bag and opens the pop off (APL) valve
- the next inspiration draws on the gas in the expiratory limb. The exp limb will have less CO2 (less rebreathing0 if FGF is high, TV is low, and the duration of the exp pause is long
- all NRB circuits are convenient, lightweight, easily scavenged( if using appropriate FGF)
Advantages of nonrebreathing circuits (Mapleson)
used during transport of children
Minimal dead space, low resistance to breathing
Scavenging
Disdvantages of nonrebreathing circuits (Mapleson)
Scavenging (variable ability dependent on FGF)
High flows required (cools child, costly)
Lack of humidification (except for Bain)
Possibility of high airway prssures (barotrauma)
Unreconized kink of inner hose in Bain
Pollution and higher cost
Difficult to assemble
Pic of Mapleson
to see what you just learned
with the Mapleson what will determine the performance and classification?
the fresh gas inlet (refer to pic again and notice the FGF inlets)
how does the APL valve work witht he mapleson?
(a nonrebreathing simiopen system)
how is it positioned during spont ventilation?
how is it positioned for assisted ventilation?
- if gas inflow > pt’s uptake and circuit uptake = preesure buildup and opens APL (gas out via scavenger)
- fully open
- partial closure ehile squeezing breathing bag
with the mapleson A*** why is it a bad choice for mechanical ventilation? and why is it a good choice for spont_A_***neous ventilation
- mechanical bad- since no gas is vented during expiration, high unpredictable FGF (> 3 times MV) needed to prevent rebreathing
- SpontAneous good- since a FGF = MV will be enough to prevent rebreathing
notice the A
name the types of Mapleson
which version of the mapleson uses FGF to force alveolar gas away from the pt toward the APL valve?
it is very effecient during contraolled ventilation
Mapleson D
efficient controlleD ventilation
The mapleson D is also called what
Bain system
what is the tubing like with the bain (mapleson D) system for FGF and exhaled gas
fresh gas enters through a norrow inner tube
exhaled gas exits through a currugated outer tube
what are the FGF rates that are required for the Mapleson D (Bain) system?
spontaneous
Controlled ventilation
200-300ml/kg/min (2times Ve) spont
70 ml/kg.min controlled
with the Bain system in the spontaneous mode what must you remember to do first, before connecting to the pt to it?
fill the breathing system with FG
with the bain system it has been mathmatically calculated and clinically proven that the FGF shold be a least what times the pt’s MV in order to minimize rebreathing (high flows)
1.5 - 2 times
Advantages of the Bain ( maplesin D)
Warming of FG inflow by surrounding exhales gases
Improved humidification with partial rebreathing
Ease of scavenging waste gases
Overflow/presure valve (APL)
disposable/sterile
Disadvantages of the Bain (modified mapleson D system)
Unrecognized disconnection
kinking of the inner FGF tubing
Needs high flows
Not easily converted to portable when commercialy used in anesthesia machine
what makes the Bain different from the standard mapleson D
APL valve addition
what ia a way to test the unique hazard of the bain circuit to have an occult disconnection or kinking of the inner hose (FG delivery hose)
Pethicks test
How do you perform the Pethicks’s test
- occulde the pt’s end of the cicuit (at the elbow)
- close the APL valve
- fill the circuit, using the O2 flush valve (like pressurizing the circuit when you are doing a leak test)
- Release the occlusion at the elbow and flush. a venturi effect flattens the reservoir bag if the inner tube is patent.
what is included in the circular system?
- FGF
- Ins limp
- exp limp
- unidirectional valves
- spill valve
- Reservoir bag
- CO2 absorber
- Bellows (per book)
what part of the circular system is placed in close proximity to the pt to prevent backflow into inspiratory limb if circuit leak develops?
Unidirectional valves
what is placed b/t the absorber and inspiratory valve in the circle system.
Fresh gas outlet
Side note - of placed down stream from insp valve it would allow FG to bypass pt during exhalation and be wasted. If FG were placed b/t expiration valve and absorber FG would be diluted by recirculating gas
where are the unidirectional valves located in the circle system
in clos proximity to the pt
where is the fresh gas inlet placed in the circle system
b/t the absorber an the insp valve
what is placed immediately before the absorber to conserve absorption capacity and to minimize venting of FG
APL valve (spill valve)
in the circulatory system what is placed in the expiratory limb to decrease the resistance to exhalation.
Breathing bag
where is the APL (spill) valve located in the circular system?
what does it do?
immediatly before the absorber
to conserve absorption capacity and to minimize venting FG
where is the breathing bag placed in the circulatory system?
what does it do?
in the exp limb
to decrease resistance to exhalation
the Breathing bag compression during controlled ventilation will do what
vent alveolar gas through APL valve, conserving absorbant.
