Anesthetic Machine

what is the purpose of anesthetic machines

Anesthetic machines deliver precise amounts of oxygen and volatile anesthetic under controlled conditions to patients undergoing general anesthesia via a breathing circuit.

what are the 4 big, main components of the anesthetic machine

1. compressed gas

2. anesthetic vaporizer

3. breathing circuits

4. scavanging system

what are the 2 items under compressed gas

1. flow meter

2. o2 flush valve

Safety concerns with compressed gases (4)

1. Flammable

2. Pressurized release of gas cause injury

3. Dropped- become a projectile

4. Wrong gas hooked up

purpose of tank pressure gauge

Pressure of gas remaining in the compressed gas cylinder

what pressure is considered a full tank (range)

1900 - 2200 psi

at what pressure does a gas cylinder need to be replaced

below 500 psi

Must check O2 tank levels at …

the start of each day

purpose of Pressure reducing valve

reduces outgoing pressure to a usable level

what is the purpose for the Line pressure gauge

indicates the pressure in the intermediate-pressure gas line between the pressure-reducing valve and the flowmeters

what should the pressure be of the line pressure gauge (range)

40 - 58 psi

Intermediate-pressure gas line connects to the — —

anesthetic machine

Carrier gases must be delivered to patient at a controlled — —

flow rate

— is the primary carrier gas used in all anesthetic machines.

Oxygen

Flow rate expressed in

L/mins

non rebreathe circuit aka

bain

what are the 2 kinds of breathing circuits (long name)

1. non re-breathe

2. re-breathe

what is the induction and recovery rate for non rebreathe circuit

300 ml/kg/min

what is the maintenance rate for non rebreathe circuit

300 ml/kg/mins

rebreathe circuit aka

circle

what is the induction and recovery rate for rebreathe circuit

100 ml/kg/mins

what is the maintenance rate for rebreathe circuit

30 ml/kg/mins

If your calculated flow rate is less than 1 L/mins you will set it to …

1 L/mins

why cant we go less than 1 L/mins in flow rates

the concentration delivered to the patient can be unreliable

Round your calculated flow rate value up to the nearest …

100 ml/mins

purpose of o2 flush valve

Used to flush system of anesthetic gases

we Disconnect patient to avoid sending high pressures into lung and causing —

barotrauma

purpose of anesthetic vaporizer

vaporizes liquid inhalant anesthetic and mixes it with the carrier gases.

what kind of vaporizer

precision vaporizers

purpose of vaporizer outlet port

is the point where O2 and inhalant anesthetic exit the vaporizer on the way to the breathing circuit.

the Vaporizer Outlet Port connects to either … (2)

1. directly to the breathing circuit via a hose or

2. connects instead to the common gas outlet.

purpose of breathing circuits

The breathing circuit conveys the carrier gases and inhalant anesthetic to the patient and removes exhaled carbon dioxide.

what is a rebreathe

Patient rebreathes expired gases

Characteristic of Rebreathe (Circle)? (8)

1. Needs CO2 absorber

2. Slower changes in anesthetic depth after vaporizer dial changes

3. Less oxygen used

4. Less inhalant used

5. Lower cost

6. Less moisture loss

7. Less heat loss

8. For use on patient above 10 kg

define Non-rebreathing circuits (Bain hoses)

don’t rebreathe expired gas

Characteristics of Non rebreathe Systems? (9)

1. Co2 absorber not required

2. Rapid changes in anes depth occur with changes in vaporizer settings

3. Uses more oxygen

4. Uses more inhalation agents

5. Higher cost

6. Poor heat conservation

7. poor moisture conservation

8. Used for patients under 10kg

9. can be used for all normally though

The size of the bag reflects …

the net volume of the gas in the breathing system at any given time

functions of resevoir bag (5)

1. Space to accept expired air

2. Provides air needed to fill lungs

3. Used to observe patients respiration

4. Confirm ET tube placement by bag movement

5. Delivery of anesthetic gases or oxygen (“bagging”, IPPV)

what happens if the resevoir bag is too small (2)

1. Insufficient safety against pressure build up

2. Not large enough reserve volume for the patient to draw on inspiration

what happens if the resevoir bag is too large (3)

1. PPV is awkward

2. Monitoring spontaneous breathing difficult as minimal movement occurs

3. Unnecessary volume which can cause delay if you want to change the depth of anesthesia

how to calculate resevoir bag size

60 ml X body weight (kg)

in resevoir bags, If more than — ml away from an available bag size select the next size larger

100

what are the bag size options (4)

1. 0.5 L

2. 1 L

3. 2 L

4. 3 L

purpose of Carbon Dioxide Absorber

Contains granules that absorbed CO2 from exhaled air, and spit the clean air back out

what is the main ingredient in a Carbon Dioxide Absorber

Calcium Hydroxide

how to tell when the Carbon Dioxide Absorber is depleted (4)

1. Hard and brittle

2. Purple/pink vs white (caution)

3. 6-8 hr of use

4. After 30 days

APL valve stands for

Adjustable Pressure Limiting Valve

purpose of Adjustable Pressure Limiting Valve (2)

1. Vents waste gases and pressure

2. Connects breathing circuits to the scavenging system

the APL valve Must remain fully open except (3)

1. Testing the machine for leaks

2. Testing cuff inflation on ET tube

3. IPPV (bagging)

why should u always try and use a cuffed et tubes (3)

1. The inflated cuff helps prevent leakage of air and gases around the tube and therefore reduces waste gas pollution in the operating room.

2. Use of a cuffed tube minimizes the risk of aspiration of blood, saliva, vomitus, and other material into the lungs.

3. Cuffed tubes prevent the animal from breathing room air, which may otherwise flow around the outside of the tube and dilute anesthetic gases. Adequate depth of anesthesia is difficult to maintain in animals breathing significant amounts of room air.

what are the 2 types of et tubes

1. high volume/low pressure

2. low volume/high pressure

what are some alternatives to et tubes (2)

1. Cole Tubes

2. Supraglottic Airway Devices (SGAD)

what are the advantages of cole tubes (3)

1. the flexibility of the baffles allows the release of airway pressure over 20 to 30 cm H2O, thus reducing the risk of barotrauma in the event that excess pressure builds up in the breathing circuit

2. less trauma to the tracheal mucosa due to the limited area of contact with the baffles

3. a sweeping motion created by the baffles that helps carry liquids out of the trachea during extubation

what does SGAD stand for

Supraglottic Airway Devices

Supraglottic Airway Devices aka

laryngeal mask airway

LMA stands for

laryngeal mask airway

what is the benefit of laryngeal mask airway

allows the anesthetist to manage the airway without invading the tracheal lumen

define dead space

spaces through which these gases travel but in which no gas exchange occurs.

The patient’s — — must be considerably more than the dead space volume in order for oxygen and anesthetic gas to reach the alveoli and for carbon dioxide to be eliminated

tidal volume

what are the 3 sources of dead spacee

1. anatomic

2. alveolar

3. mechanical

anatomic and alveolar dead space comprise — dead space

physiologic

In an average patient, when awake, normal tidal volume is estimated to be approximately (range)

10 - 15 ml/kg

Guidelines are that mechanical dead space should not exceed (range)

2 - 3 ml/kg

purpose of scavange tube

Function is to collect waste gas from the machine/circuit and conduct it for disposal outside the building

purpose of scavange system

disposes of excess and waste anesthetic gases

WAG stands for

waste anesthetic gases

what do WAGs cause (3)

1. dizziness

2. heachaches

3. birth defects

what are the 2 types of scavange

1. passive

2. active

a passive scavange system relies on …

the pressure in system (O2 flow rate) to push WAG to either go directly to the outside or through a charcoal filter

what is a type of passive scavange

charcoal filter

how do u know when to replace charcoal filter (2)

1. When weight increases by 50 grams it is time to discard

2. Discard after 12 hours

what is an example of an active scavange system (2)

1. vaccum to outside

2. fans to outside

define Anesthetic chambers

clear, aquarium-like boxes used to induce general anesthesia in small patients that are feral, vicious, or intractable, or that cannot be handled without undue stress

a leak test does not test for (3)

1. Oxygen gas cylinder to flow meter

2. Scavange system

3. The inner tube of the bain

if a leak test fails you should check (7)

1. Check breathing hoses

2. Check resevoir bags

3. Check ET tubes

4. Check CO2 absorber not sealed

5. Covering over unidirectional valve

6. Connection between pop off scavanger not tight

7. Vaporizer cap not replaced

how to set up anesthetic machine (11)

1. All maintenance is up to date

2. Turn oxygen on and ensure adequate levels

3. Check vaoprizer levels

4. Connect oxygen line to machine if not already

5. Select breathing circuit and resevoir bag to the machine

6. Connect circuit and resevoir bag to the machine

7. Connect scavange and make sure no kinks (+/- turn on/replace)

8. Perform leak test at minimum daily and after changing circuits (ideally before every patient)

9. Calculate oxygen flow rates

10. Select ET tubes

11. Ensure all other supplies are ready

procedure for a leak test (11)

1. turn o2 on

2. make sure o2 canister is above 500 psi

3. put something in end of tube

4. close APL valve

5. turn on o2 flow

6. watch meter go to 20 psi

7. turn off flow

8. count to 20 noting if it goes up or down

9. open APL valve

10. turn o2 off

11. flush