Breathing Machines - Exam 2 Flashcards by Erin Baker

Breathing systems do these 6 things:

Receives gas mixture from the machine
Delivers gas to the patient
Removes CO2
Providing heating and humidification of the gas mixture
Allows spontaneous, assisted and controlled respiration
Provides gas sampling, measures airway pressure, and monitors volume

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When gas passes through a tube, the pressure at the outlet will be ___ than at the inlet

The drop in pressure is a measure of the ______ that must be overcome

lower
Resistance

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In this type of flow, the flow is smooth and orderly. Particles move parallel to the tube walls.

Laminar flow

Poiseuille’s law

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This term is used in regards to turbulent flow and is composed of particles moving across or in opposite the general direction of flow

Eddies

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With ____ flow, the flow rate is the same across the diameter of the tube.

With ____ flow, flow is fastest in the center where there is less friction

Turbulent

Laminar

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Is this generalized or localized turbulent flow:
When the flow of gas through a tube exceeds the critical flow rate

Generalized

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Is this generalized or localized turbulent flow:
Gas flow rate below the critical flow rate but encounters constrictions, curves, or valves

Localized

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To minimize resistance, gas-conducting pathways should have ___ length, ___ internal diameter, and be without sharp curves or sudden changes in diameter

minimal, maximal

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Changes in ____ parallel changes in the work of breathing

resistance

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What causes more resistance: ETT or breathing system?

ETT

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What tool can we use to learn about resistance?

Flow-volume loops

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This term is the ratio of change in volume to change in pressure

Compliance

Measures distensibility (mL/cm H2O)

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What two things are the most distensible components of the breathing system?

-Breathing tubes
-Reservoir bags

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What three things influence rebreathing?

-Fresh gas flow
-Dead space
-Breathing system design

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Amount of rebreathing varies inversely with the total ___

fresh gas flow

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If the volume of FGF supplied per minute is equal to or greater than the pt minute volume, ____________ occurs

NO REBREATHING

As long as exhaled gas is vented

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If the volume of FGF supplied per minute is less than the pt minute volume, then _____ occurs

REBREATHING

Some of the exhaled gases must be rebreathed to make up required volume

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This is the volume in a breathing system occupied by gases that are rebreathed without change in composition

apparatus

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How can you decrease the apparatus dead space?

Decreased by having inspiratory and expiratory limb separation as close to patient as possible

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What two things make up physiologic dead space?

anatomical and alveolar dead spaces

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This type of dead space involves conducting airways; adds H2O vapor

Anatomical

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What is alveolar dead space?

volume of alveoli ventilated but not perfused

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Rebreathing reduces __ and ____ loss from the pt

heat, moisture

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Components of breathing system pic

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Where do masks go on the face?

Fits between the interpupillary line and in the groove between the mental process and the alveolar ridge

Masks connect to the Y-piece or connector and involve a ___ mm female connection

22 mm female connection

Benefits of connectors / adapters

-Extends distance between patient and breathing system -Change angle of connection -Allow more flexibility/less kinking

Disadvantages of connectors / adapters

-Increased resistance -Increases dead space -Additional locations for disconnects

Desirable Characteristics of A Breathing Circuit (6)

-Low resistance to gas flow -Minimal rebreathing -Removal of CO2 at rate of production -Rapid changes in delivered gas when required -Warmed humidification of inspired gas -Safe disposal of waste gases

This type of circuit has no reservoir bag and no rebreathing

open

This type of circuit has a reservoir bag but no rebreathing

semi-open

This type of circuit has a reservoir bag and partial rebreathing

Semi-closed

This type of circuit has a reservoir bag and complete rebreathing

closed | Depends on FGF

Two functions of any breathing circuit

-Deliver oxygen and anesthetic gases -Eliminate CO2 (either by washout with adequate fresh gas flow (FGF) or by soda lime absorption)

Classify these breathing circuits: Nasal cannula, open drop, insufflation

Open

Classify these breathing circuits: Non rebreathing circuit, circle at high fresh gas flow

Semi-open

Classify these breathing circuits: Circle at fresh gas flow less than minute ventilation

Semi closed

Classify these breathing circuits: circle at extremely low fresh gas flow, with APL closed

Closed

Classify this breathing system, these are its characteristics: NO reservoir NO rebreathing No neutralization of CO2 No unidirectional valves

Open

What type of breathing systems are the following: Mapleson A, B, C, D Bain Jackson-Rees

Semi open

Classify the breathing system: Gas reservoir bag present NO rebreathing No neutralization of CO2 No unidirectional valves Fresh gas flow needed exceeds minute ventilation (two to three times minute ventilation to prevent rebreathing). Minimum FGF 5L/min

Semiopen

This is a type of “circle system” that always has a gas reservoir bag and allows for **PARTIAL** rebreathing of exhaled gases -It always provides for chemical neutralization of CO2 -Fresh gas flow is less than minute ventilation How many unidirectional valves does it have? What is an example?

-Semiclosed -Always contains 3 unidirectional valves (insp, exp, APL) -Example – The machine we use everyday!

This type of breathing system always has a gas reservoir bag and allows for **TOTAL** rebreathing of exhaled gases It always provides for chemical neutralization of CO2 and it always contains unidirectional valves

Closed

What is another name for the **modified** Mapleson D?

Bain

What is the big difference between the Mapleson D and Bain circuit?

The main difference is that the Bain has the fresh gas hose inside the expiratory corrugated limb (tube within a tube).

________ is better known as Jackson-Rees modification of Ayre’s T-piece Who is this used exclusively in?

-Mapleson F -Children

The mapleson F has a very low resistance to breathing. -The degree of rebreathing is influenced by method of ______ -It has an adjustable ___ valve -Delivery of FGF should be at least ___ the minute volume

-ventilation -overflow -2x

Open anesthetic breathing system: Does it have a gas reservoir bag? Is there rebreathing of exhaled gases? Is there chemical neutralization of exhaled CO2? Are there unidirectional valves? What is the fresh gas inflow rate?

-No -No -No -None -Unknown

Semi-open anesthetic breathing system Mapleson A, B, C, D and Bain: Does it have a gas reservoir bag? Is there rebreathing of exhaled gases? Is there chemical neutralization of exhaled CO2? Are there unidirectional valves? What is the fresh gas inflow rate?

-Yes -No -No -One -High

Semi-open anesthetic breathing system Mapleson E: Does it have a gas reservoir bag? Is there rebreathing of exhaled gases? Is there chemical neutralization of exhaled CO2? Are there unidirectional valves? What is the fresh gas inflow rate?

-No -No -No -None -High

Semi-open anesthetic breathing system Mapleson F (Jackson Rees): Does it have a gas reservoir bag? Is there rebreathing of exhaled gases? Is there chemical neutralization of exhaled CO2? Are there unidirectional valves? What is the fresh gas inflow rate?

-Yes -No -No -One -HIgh

Semi-closed anesthetic breathing system; Circle: Does it have a gas reservoir bag? Is there rebreathing of exhaled gases? Is there chemical neutralization of exhaled CO2? Are there unidirectional valves? What is the fresh gas inflow rate?

-Yes -Partial -Yes -Three -Moderate

Closed anesthetic breathing system; Circle: Does it have a gas reservoir bag? Is there rebreathing of exhaled gases? Is there chemical neutralization of exhaled CO2? Are there unidirectional valves? What is the fresh gas inflow rate?

-Yes -Total -Yes -Three -Low

With non-rebreathing circuits, what two things do they lack?

-Unidirectional valves (insp and exp) -Soda lime CO2 absorber

With non-rebreathing circuits, the amount of rebreathing is highly dependent on _____ The work of breathing is ___

-FGF -Low

How do NRB work?

-During expiration, fresh gas flow (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 expiratory limb will have less carbon dioxide (less rebreathing) if FGF inflow is high, tidal volume (VT) is low, and the duration of the expiratory pause is long (a long expiratory pause is desirable as exhaled gas will be flushed out more thoroughly). -All NRB circuits are convenient, lightweight, easily scavenged (if using appropriate FGF).

How long is breathing tubing? What is the internal volume?

-1 meter in length -Internal volume - 400-500 mL/m of length

Why is the flow in breathing tubing always turbulent?

Bc it is corrugated

If you pressure check the circuits before use, what is the limit in cmH2O?

30 cmH2O

Unidirectional valve information

Which valve (insp or exp) prevents backflow of exhaled gases? Which valve prevents rebreathing?

-inspiratory valve -expiratory valve

Unidirectional valves must be placed between the patient and the _____

reservoir bag

What size reservoir bag is traditionally used for adults?

The minimum pressure of a reservoir bag is ___ cmH2O THe max pressure (rubber bags) is between __ and __ cmH2O

-30 -40-60

This type of reservoir bag has 2x the distending pressure of a rubber bag

PLASTIC

Reservoir bags can range from ___ to ___ L

0.5-6L

What is the preferred location for the gas inflow site?

between CO2 absorbent and inspiratory valve

This controls the pressure in the breathing system, releases gas to the scavenging system and permits gas to leave the circuit

APL valve

with an APL valve, does clock wise motion increase or decrease pressure?

INCREASE

3 requirements for APL valve on system:

-Clockwise motion to increase pressure -1-2 clockwise turns from fully open to fully closed -An arrow must indicate direction to close valve

During spontaneous respiration what is the APL valve doing (opened or closed or bypassed) during: Inspiration? Expiration? What about CPAP inspiration?

-Closed -Open -Partially closed

During assisted/manual ventilation what is the APL valve doing (opened or closed or bypassed) during: Inspiration? Expiration?

-Partially open (excess diverted) -Partially open

During mechanical ventilation what is the APL valve doing (opened or closed or bypassed) during: Inspiration? Expiration?

-Bypassed -Bypassed

What are the four parts of the absorber canister?

-Canister -Absorbent -Housing -Side/center tube

Which part of the absorber canister returns gas to the patient?

Side/center tube

Cornelius put this under a slide so here it is FYI:

A threaded screw cap over the spring allows the pressure exerted by the spring on the disc to be varied. When the cap is fully tightened, the disc will prevent any gas from escaping from the system. As the cap is loosened, the tension on the spring is reduced so that the disc can rise. When the pressure in the breathing system increases, it exerts an upward force on the disc. When this upward force exceeds the downward force exerted by the spring, the disc rises and gas flows through the valve. When the pressure in the system falls, the disc returns to its seat. When the cap is at its maximum open position, there will be only minimal pressure exerted by the spring. This allows the patient’s exhalation to lift the disc with only minimal pressure. The weight of and pressure on the disc ensures that the reservoir bag fills before the disc rises. Spontaneous Respiration With spontaneous respiration, the APL valve remains closed during inspiration and opens during exhalation. Normally, the valve is fully open during spontaneous ventilation. It should be closed slightly only if gas is withdrawn from the breathing system by negative pressure from the scavenging system and the reservoir bag collapses. Partially closing the valve during spontaneous respiration will result in continuous positive airway pressure (CPAP). With spontaneous respiration, the anesthesia provider must be constantly aware of volume of gas in the bag. If attention is diverted, the bag may collapse or become overdistended. Negative pressure transmitted from the scavenging system may cause gases to be evacuated from the breathing system. An obstruction in the scavenging system may result in the bag becoming overdistended and the patient being subjected to CPAP. During inspiration, the bag is squeezed and pressure increases until the relief pressure is reached. Before this, the patient receives all of the gas displaced from the bag (less a small amount due to gas compression and expansion of the tubes). Once the APL valve opens, the additional volume that the patient receives is determined by the relative resistances to flow exerted by the patient and the APL valve.

O2 consumption equation? For neonates?

Wt in kg x 3 Neonates: Wt in kg x 4

Absorbents are exhausted when all _____ become ____

hydroxides, carbonates

What are the components of soda lime?

-Calcium hydroxide (~80%) -Sodium hydroxide and potassium hydroxide (~5%) -Water (~15%) -Small amounts of silica and clay

Soda lime can absorb __% of its weight in CO2 Therefore, 100 g can absorb approximately __ L CO2

19% 26L

3 issues with Calcium hydroxide lime

-Compound A -CO -Destruction of inhaled gases

This absorbent is used in spacecrafts and has more CO2 absorption capacity

Lithium hydroxide

Four advantages of litholyme?

-No reaction with inhaled anesthetic agents -No activators/strong bases -No regeneration (pH indicators do not become colorless) -Lower exothermic reactivity --> reduced risk of fire --> and reduced economic/environmental impact

This CO2 absorber has no color indicator but is cost effective

Spira-lith

CO2 absorber chart

What is the most common dye used for absorbent indicators?

ethyl violet

Absorbents undergo color change around a pH of

10.3

Exhausted absorbent is ____ (color) and occurs with a pH of <___

purple, 10.3

The mesh size for CO2 absorbent is ___-___ It functions to maximize absorption and minimize ____

4-8 resistance

Half the volume of the CO2 absorber cannister is __

gas

How does excess water in the CO2 absorber impact CO2 absorption

decreases efficiency of CO2 absorption and decreases surface area

How to minimize channeling with CO2 absorbers (5)?

-Circular baffles -Placement for vertical flow -Permanent mounting -Prepackaged cylinders -Avoiding overly tight packing

Compound A formation occurs in these situations:

-Low FGF -Increased absorbent temperature -Higher inspired sevoflurane concentrations -Dehydrated absorbent

List the highest to lowest occurence of CO formation with the volatiles:

Desflurane ≥ enflurane > isoflurane > halothane > sevoflurane

Which gas should you avoid with desiccated strong base absorbents?

Sevoflurane

APSF reccomendations to avoid compound A / CO / heat formation

What are the components of a Mapleson circuit?

What is the Mapleson circuit missing (in comparison to a circle system)?

-CO2 absorber -Unidirectional valves -Separate insp / exp limbs

What Mapleson component has a large diameter (22mm) that creates low-resistance pathway for gases & potential reservoir for gases

corrugated breathing tubes

The position of this Mapleson component will determine type of Mapleson performance and classification

Fresh Gas Inlet

In a Mapleson circuit, what happens if gas inflow is > pt’s uptake & circuit uptake

pressure buildup opens APL (gas out via scavenger)

In the Mapleson A (Magills system) where is the FGF? Where is the APL?

FGF: Near reservoir bag, opposite of the patient APL: Near the patient

This Mapleson system has the best efficiency of all systems for spontaneous ventilation, worst during controlled ventilation

Mapleson A

What are the FGF requirements to prevent rebreathing during spontaneous ventilation in the Mapleson A system? What about during controlled ventilation? What about mechanical ventilation?

-FGF must be greater than or equal to minute volume to prevent rebreathing during spontaneous ventilation -Rebreathing during controlled ventilation occurs unless minute ventilation is very high, more than 20L/min -Since No gas is vented during expiration, high unpredictable FGF (> 3 times minute ventilation) needed to prevent rebreathing during mechanical ventilation (Poor choice)

Why is the Mapleson A circuit a poor choice for mechanical ventilation?

High unpredictable FGF > 3x minute ventilation is needed to prevent rebreathing during mechanical ventilation

In the Mapleson B where is the FGF? Where is the APL? Reservoir bag?

-Both near patient -Bag near end of system

Why is the Mapleson B inefficent?

You lose a lot of volume because much of the FGF is vented through APL during exhalation

With the Mapleson B, FGF should be ___x minute volume during spontaneous and controlled ventilation to prevent rebreathing

The Mapleson C is almost identical to the Mapleson B except for the fact that the Mapleson C omits the

corrugated tubing

With the Mapleson C, FGF should be ___x minute volume to prevent rebreathing

This Mapleson Circuit has a 3 way T-Piece

Mapleson D

In the Mapleson D where is the FGF? Where is the APL? Reservoir bag?

-Fresh gas inlet near pt -APL at end, near reservoir -Reservoir at the end

Bain modification of a Mapleson D involves what?

FGF coaxial (tube within a tube) inside tubing

With a Bain system, what is the FGF requirements to prevent rebreathing during spontaneous breathing? Controlled ventilation?

* 200-300ml/kg/min with spontaneous breathing (2 times VE) * 70ml/kg/min with controlled ventilation

Advantages of a Bain

-Warming of fresh gas inflow by surrounding exhaled gases (countercurrent exchange) -Improved humidification with partial rebreathing -Ease of scavenging waste gases -Overflow/pressure valve (APL valve) -Disposable/sterile

Disadvantages of a Bain

-Unrecognized disconnection -Kinking of inner fresh gas flow tubing -Requires high flows -Not easily converted to portable when commercially used anesthesia machine adapter Bain circuit used

Why do we have to use the Pethick's test for the Bain circuit?

-A unique hazard of the use of the Bain circuit is occult disconnection or kinking of the inner hose (fresh gas delivery hose)

How to perform Pethick's test

-Occlude the patient's end of the circuit (at the elbow). -Close the APL valve. -Fill the circuit, using the oxygen 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.

This Mapleson system has NO reservoir bag / APL and has corrugated tubing that attaches to a T-Piece

Mapleson E (Ayre’s T-Piece)

Mapleson F (Jackson Rees) FGF requirements for rebreathing prevention

2 - 2.5x minute ventilation

Why is excessive pressure less likely to develop with the Mapleson F (Jackson Rees)?

There is no APL valve

Rank the Mapleson's in terms of efficiency with spontaneous ventilation

Mapleson A is greater than Maplesons DFE, which are greater than Maplesons CB

Rank the Mapleson's in terms of efficiency with controlled ventilation

Maplesons DFE are greater than Maplesons BC, which are greater than Mapleson A

Advantages of Maplesons

-Simple, inexpensive, and lightweight -Changes in FGF composition result in rapid changes in the circuit -Low resistance to gas flow -No toxic products d/t lack of CO2 absorbent -No degradation w/ VAs

Disadvantages of Maplesons (3)

-Require high FGF -Scavenging challenging -Not suitable for patients with MH

With a circle system, the extent of rebreathing and conservation of exhaled gases, depends on ___

FGF

3 rules with a circle system that prevent rebreathing:

-Unidirectional valve must be located between the pt and the reservoir bag on both the inspiratory and expiratory limbs -The fresh gas inflow cannot enter the circuit between the expiratory valve and the pt -APL valve cannot be located between the pt and the inspiratory valve

When would you use a semi-closed circle system?

Low flow anesthesia

What 2 types of equipment use semi-open circle sysems?

Scuba gear and post-op ICU vents

This type of circle system function is where the rate of oxygen inflow exactly matches the metabolic demands

Closed

Advantages of low-flow anesthesia

-Decreased use of VAs -Improved temperature and humidity control -Reduced environmental pollution

Disadvantages of low-flow anesthesia

-Difficulty in rapidly adjusting anesthetic depth -Possibility of accumulating unwanted exhaled gases ( ex: CO, acetone, methane) -VA degradation by-products (ex: CO, compound A)

Advantages of circle system

-Low FGF can be used -Elimination of CO2 -Relatively stable inspired gas concentration -Conservation of moisture/heat/gases -Prevention of OR pollution

Disadvantages of a circle system

Complex design CO or compound A May compromise Vt during controlled ventilation ASA Closed Claims Project -->Misconnections/ disconnections

Components of self-Inflating Manual Resuscitators

-Self-expanding Bag -T-shaped non-rebreathing Valve -Bag Inlet Valve -Pop-off valve -Excess oxygen venting valve -Oxygen reservoir

Hazards of self-inflating manual resuscitators

-Barotrauma or gastric insufflation -Significant variation of tidal volume, PIP, and PEEP -Nonrebreathing valves generate resistance

Where are bacterial filters placed?

Expiratory limb

Which of the following bacterial filter types has a larger surface area: the small pore, compact matrix or larger pore size arrangment? Which one has more resistance?

Small-pore compact matrix

What is the upside of the hydrophobic bacterial filter? What are the two downsides?

Upside: prevents water penetration Downside: decreased efficiency, increased resistance

Define humidity

Define absolute humidity

Define relative humidity

Define water vapor pressure

In regards to humidification of the airway, heating and humidification has occurred by mid-____ It heats to ___ C with an absolute humidity of ___ to ___ mg/L

trachea 34°C with an absolute humidity of 34 to 38 mg/L (95% to 100% relative humidity)

What is the issue with cold ambient temperatures in the airway?

Little capacity to hold water vapor Low absolute humidity Upper airway transfers large amounts of heat and moisture May trigger a bronchospasm

How does underhumidification negatively impact the respiratory tract?

Damage to respiratory tract because: Secretions thicken Ciliary function decreases Surfactant activity is impaired Mucosa susceptible to injury

3 issues (vague) with underhumidification

-Damages respiratory tract -Body heat loss -Tracheal tube obstruction can cocur

Issues with overhumidification

-Condensation of water in the airway -Reduced mucosal viscosity and risk of water intoxication -Inefficient mucociliary transport -Airway resistance, risk of pulmonary infection, surfactant dilution, atelectasis, and V/Q mismatch -Obstruction to sensors

Are HME's passive or active? What about heated humidifiers?

passive active

Humidification devices aim to reproduce more normal physiologic conditions in the __ respiratory tract

lower

Where are HME devices placed between?

Placed close to the pt, between Y piece and proximal end of ETT or LMA

HME functions

-Conserves heat + water -Returns heat + water to patient -Serves as filter (bacteria, virus, particles)

Issues with HME filters?

-Low ETCO2 reading -Increases resistance and dead space in circuit -Efficiency may be reduced with large Vt (Hydrophobic models)

Which type of HME is made of paper or other fiber barrier coated with moisture-retaining chemicals

Hygroscopic

Which type of HME is made of pleated hydrophobic membrane with small pores

Hydrophobic

Which HME filter (hydrophobic or hygroscopic) is more efficient at filtering pathogens

Hydrophobic

Which HME filter (hydrophobic or hygroscopic) is most efficient retaining heat and moisture

Hygroscopic

Which HME filter (hydrophobic or hygroscopic) is more prone to becoming saturated and increasing in resistance?

Hygroscopic

Heated humidifiers should not be placed on the ____ limb

expiratory

Heated humidifiers should be placed on the ____ limb downstream of the _______

inspiratory, unidirectional valve

Advantages of humidifiers

Can deliver saturated gas at body temp or higher More effective than HME

Disadvantages of humidifiers

Bulky Potential electrical malfunction and/or thermal injury Contamination, cleaning issues Higher cost than HME Water aspiration risk

Breathing Machines - Exam 2 Flashcards

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