exam 3 part 3 Flashcards
breathing systems
estimated FiO2 achieved with nasal prongs O2 cannula at various flow rates (1L-4L)
1L- 24%
2L- 28%
3L - 32%
4L - 36%
during regional anesthesia or sedation it is common that
no breathing system is used, but supplemental O2 often administered
nasal cannula is an example of an ________ system
open
estimated FiO2 achieved with simple face mask at various O2 flow rates (5L-9L)
5-6L - 40%
6-7L - 50%
7-8L - 60%
8-9L - 70%
minimum flow rate on simple mask to avoid rebreathing
5L
need to use a reservior on simple mask to get FiO2 > ______, if flow rates are >____L
80%
10L
flow out of CGO is ______ whereas flow in trachea is _____
consistent
variable
a breath of 500 ml inhaled over 3 seconds requires a flow rate of _______
10L/min for that 3 seconds
functions of the anesthesia breathing circuit (2)
1- deliver oxygen and/or anesthetic gases without significant increase in airway resistance
2- eliminate CO2 by wash out with FGF or chemical neutralization
elements of the breathing system
fresh gas flow
dead space
rebreathing
reservoir
adjustable pressure limiting valve (APL)
most commonly used breathing circuit type
semi-closed
open breathing circuit types and components
insufflation
open drop
nasal cannula
(NO RESERVOIR BAG NO UNIDIRECTIONAL VALVES)
open breathing circuit elimination of CO2
no rebreathing of gas - no chemical elimination needed
semiopen breathing circuits components
Mapleson A, B, C, D
Bain
Mapelson E
Mapelson F (Jackson-Rees)
what semiopen breathing system does NOT have a gas reservoir bag or unidirectional valves
Mapleson E
majority of semiopen breathing circuits have ______ unidirectional valve
1
semiopen breathing circuits have ______ FGF
High
semiopen breathing circuits elimination of CO2
high fresh gas flow prevents rebreathing - no chemical elimination needed
semiclosed breathing circuit components
Circle system
has reservoir bag, partial rebreathing and 3 unidirectional valves
which breathing system has moderate FGF
semiclosed
semiclosed breathing circuit elimination of CO2
fresh gas flow exceeds consumption while allowing for rebreathing - needs chemical neutralization of CO2
circle system breathing circuit advantages
constant inspired concentrations
conserve respiratory heat and humidity
useful for all ages
low resistance
useful for multiple system types
cost reduction- less agent/O2 used
decreases exposure to OR staff of waste gas
decreased pollution and waste of anesthetic gases
closed breathing circuit components
Circle system
has gas reservoir bag, total rebreathing, 3 unidirectional valves
which breathing system requires a low FGF
closed
closed breathing circuit elimination of CO2
indicated gas inflow equals amount consumed by the patient, rebreathing is 100% - so chemical neutralization of CO2 is needed
closed breathing circuit advantages
less waste/pollution, heats and humidifies inhaled gas
closed breathing circuit disadvantages
difficult to rapidly changes anesthetic concentration, risk of hypoxic concentrations especially if N2O is used
requires careful monitoring of O2, CO and anesthetic agent
mapleson circuits, work of breathing is _____ in all wit no __________ or _________ to create resistance
low
unidirectional valves
soda lime granules
there is no separation of inspired and expired gas with _________
mapleson circuits
if inspiratory flow exceeds FGF _______ occurs
rebreathing
less rebreathing will occur if FGF is _______, tidal volume is _____, and the duration of the expiratory pause is _____
high
low
long
with mapleson circuits inspiratory flow can reach
60L/min or 1L/sec
FGF 2-3X ____ is recommended
minute ventilation
Mapleson A spontaneous respiration process
- Inhalation:
When the patient inhales, fresh gas flows from the reservoir bag through the tubing towards the patient, as the expiratory valve remains closed. - Exhalation:
During exhalation, the expired gas travels through the tubing and fills the reservoir bag, causing pressure to build up and open the expiratory valve, venting the expired gas to the atmosphere
(dead space can be a concern with increasing tubing length)
Mapleson D spontaneous respiration process
Inspiration: The patient inhales fresh gas from the reservoir bag and the machine.
Expiration: The patient exhales, and the expired gas collects in the reservoir bag and tubing.
APL valve: The APL valve is fully open, allowing the expired gas to exit the system
Mapleson A vs Mapleson D which is better for spontaneous respiration
Mapleson A:
Most efficient for spontaneous breathing.
Requires a fresh gas flow close to the patient’s minute ventilation to prevent rebreathing.
Considered the “ideal” circuit for spontaneous ventilation.
Mapleson D:
Less efficient for spontaneous breathing.
Expired gas can accumulate in the tubing and reservoir bag before enough pressure builds to open the APL valve during spontaneous breaths.
Best suited for controlled ventilation where fresh gas flow can effectively push expired gas away from the patient
during controlled ventilation you have to close the ___________ so inspiration pressure can be generated
APL valve
the APL valve is open during ________
spontaneous respiration
which mapleson circuits are poor for controlled ventilation due to placement of APL valve
A B C
which mapleson circuits use a T piece at the patient connections
D E F
which circuits are modified mapleson D circuits
F (jackson-rees) and Bain
this mapleson circuit is good for
spontaneous respiration in pediatric patients due to reduced resistance
MAGILL - mapleson A
For Mapleson A- Magill circuit, FGF is recommended to be at _______ or ________ to avoid rebreathing, or FGF of _________ of minute volume only for spontaneous respiration
5L/min or 85ml/kg/min
42%-88%
during controlled ventilation, rebreathing occurs due to the placement of the
FGF inlet and APL valve
for the Bain circuit the FGF needs to be at ____________ or _________.
100-300ml/kg/min
1.5-3x minute volume
what makes the Bain circuit a modified mapleson D
the FGF tube runs through the corrugated expiratory limb
whereas the FGF and the expired gas mixes in the regular mapleson D
Bain circuit FGF tube can kink or disconnect, how do you test for this
The Pethick Test
4 steps of the Pethick Test
1- occlude the patient’s end of the circuit
2- close the APL valve
3- fill the circuit, using the oxygen flush valve
4- release the occlusion at the elbow and flush
result of pethick test if there is NO leak
the reservoir bag would fill while occluding and then flatten without you occluding it
name this mapleson circuit:
- used for spontaneous breathing
- lack of scavenging
- can occlude tubing to deliver positive pressure but difficult to control
- no bag expiratory limb is the only reservoir
mapleson E
circuit used for low resistance for pediatric patients
mapleson F - Jackson-Rees (FGF requirements same as Bain)
the circle system can be 3 different types of breathing system
1 - semiclosed: some rebreathing
2 - closed total: rebreathing
3- semiopen: no rebreathing with high FGF
circle systems remove _____ from exhalations chemically which allows for _____ of all other exhaled gases
carbon dioxide
rebreathing
Poiseuille’s law for resistance
resistance of a fluid to flow is equal to (8ln/pi X r^{4}), where:
n: The viscosity of the fluid
l: The length of the tube
r^4: The radius of the tube
Airway resistance
The resistance to laminar air flow is directly proportional to the length of the airway and inversely proportional to the fourth power of the airway radius
unnecessary valves and sharp bends cause _______ flow
turbulent
deadspace ends where
inspiratory and expiratory gas streams converge
Dead space in the anesthetic system can include:
The mask
The portion of the endotracheal tube that extends outside the patient’s mouth
The elbow on the endotracheal tube that connects it to the ventilation bag
Any connectors between the end of the tube and the breathing circuit, such as CO2 adapters or apnea alarm adapters
The Y piece at the end of a circuit
Anatomical dead space
The volume of air in the conducting zone of the respiratory system, which includes the nose, trachea, and bronchi. This volume is about 30% of the normal tidal volume, or 150 mL
Alveolar dead space
The volume of air in the alveoli that is ventilated but not perfused with blood. In a healthy adult, alveolar dead space is negligible
Physiologic dead space
The sum of anatomical and alveolar dead space. In healthy people, anatomic and physiologic dead space are roughly equal. However, in people with lung disease or heart failure, physiologic dead space is much larger than anatomic dead space
increasing deadspace = _______ rebreathing of CO2
how to combat this ______
increases
increase minute ventilation
minute ventilation
the amount of air that moves into or out of the lungs in one minute. It’s calculated by multiplying the tidal volume (the amount of air inhaled in a single breath) by the breathing rate.
increased dead space = __________ compliance
decreased
dead space will increase with any
breathing system
length of circuit _______ _______ circuit compliance
DOES AFFECT
circle system components
FG inlet
unidirectional valves
inspiratory and expiratory limb
Y connector or elbow
APL valve
Reservoir
CO2 absorbent
_____ size is important in the process of CO2 neutralization
granule
chemical makeup of soda lime
how is CO2 neutralized
Ca(OH)2
H2O
NaOH
3 step rxn
neutralization occurs in 1st and 3rd step with carbonic acid and CaCO3 respectively
soda lime mesh size
4-8
soda lime activator
NaOH
chemical makeup of Amsorb
how is CO2 neutralized
Ca(OH)2
CaCl2
H2O
amsorb mesh size
4-8
chemical makeup of litholyme
how is CO2 neutralized
Ca(OH)2
LiCl
litholyme mesh size
4-10
chemical makeup of lithium hydroxide
how is CO2 neutralized
(LiOH) neutralizes carbon dioxide (CO2) by reacting with it to form lithium carbonate (Li2CO3) and water (H2O)
advantages of amsorb
removal of strong alkali significantly reduces degradation of inhalation agents so much less compound A and CO
advantages of litholyme
efficient CO2 absorption capabilities, longer lifespan compared to other absorbents, no production of harmful compounds like Compound A, lack of strong bases like NaOH and KOH, and a visible color change indicating when it needs to be replaced, generates less heat
advantages of lithium hydroxide
high absorption capacity, relatively low reactivity with other gases, a high reaction rate with CO2, and potential for regeneration
disadvantages of amsorb
trace color indicator will turn purple but still need to pay attention to inspired CO2 make sure it is still going back down to 0
soda lime will turn purple during case but after case ____
even though it is exhausted it will change back to white
disadvantages of litholyme
only thing is that it costs about $5/bag more than sodalime.
disadvantages of lithium hydroxide
can severely irritate and burn the skin and eyes, and can cause eye damage. Inhaling lithium hydroxide can irritate the nose, throat, and lungs, and can lead to coughing, shortness of breath, and pulmonary edema
Fire hazards
Environmental impacts
what causes the color change of exhausted CO2 absorbent
carbonic acid accumulates causes more acidic pH
which CO2 absorbents turn purple and stay purple
amsorb plus and litholyme
hazards of granules
dust- so open APL valve to release pressure at completion of high pressure check
channeling - so shake the canister before removing plastic
packing - this is why it is important to have different size granules
soda lime can absorb up to _____- of CO2 per 100g of absorbent
23-23L
amsorb has a _____ capacity compared to sodalime
lower
you don’t change absorb based on color you change it based on _____ not returning to _______
EtCO2
Baseline
degradation of Des, Iso and Enflurane by dry soda lime produces _____ and sevo produces _____
CO
compound A
what will dry out sodalime canisters
1-2days of 10L/min FGF
how to prevent CO (5 things)
1- turn oxygen off at end of case
2- change sodalime regularly
3- change if FGF left on over the weekend or overnight
4- use low flows to keep granules moist
5 - just don’t use soda lime
what absorbent has the highest capacity for CO2 neutralization
lithium hydroxide
factors that increase compound A with sodalime
high sevo concentrations
high temperatures
low moisture
low FGF rates
scavenging happens when
FGF is greater than the amount of gas taken up by the lung
what happens when FGF is greater than the amount of gas taken up by the lung but there is no scavenging
positive pressure builds up in the circuit
in the manual ventilation mode the gas is vented through the
APL valve
in the mechanical ventilation mode the gas is vented through the
ventilator pressure relief valve
how is excess gas removed from the OR to prevent exposure and pollution
scavenging system connected to suction
the apparatus of the scavenging bag includes two types of valves, what are they
positive pressure relief valve and negative pressure relief valve
scavenging system negative pressure relief
suction exceeds inflow of gas into scavenging system, so negative pressure relief valve opens to allow room air to enter and be suctioned
scavenging system positive pressure relief
if suction does NOT remove all the inflow gas into system, this valve opens at 10 cm H2O pressure and vents gas to room
potential sources of anesthetic agent leaks into the OR and PACU
leaks at connections within the anesthesia machine
faulty breathing circuit components like tubing or valves
poorly fitted masks or endotracheal tube cuffs
improper patient positioning, damaged equipment
inadequate ventilation
malfunctioning gas scavenging systems
improper handling of anesthetic gas cylinders
poor practices like leaving gas flow control valves open after use or not properly purging the system at the end of a procedure
recommended techniques to minimize the level of anesthetic agents in the clinical environment
Ventilation and scavenging systems: Use a well-designed ventilation system to reduce waste anesthetic gas concentrations. A scavenging system can capture excess anesthetic gases and deliver them to a gas disposal assembly.
Monitor waste gases: Regularly monitor airborne concentrations of waste gases to ensure they remain below recommended limits (insufficient evidence to support needing to do this)
Use low-flow anesthesia: Use low-flow anesthesia (e.g., <1 l. min‐1) in oxygen/air mixtures.
Avoid desflurane and N2O if possible
Use total intravenous anesthesia (TIVA)
Encourage environmental sustainability
components of waste gas
nitrous oxide and halogenated anesthetic agents like isoflurane, sevoflurane, desflurane, and enflurane, which are released into the environment during an anesthetic procedure
OR ventilation is effective at minimizing agents levels because air is exchanged ____ per hour
15 times
OSHA numbers for nitrous and volatiles
N2O - <25ppm
volatiles - <2ppm
bacterial filters added into expiratory limb of circuit to prevent …
microorganism retention in the circle system leading to respiratory infections form patient to patient
