Exam 1: Lecture 4: Breathing system, Scavenging, and intubation supplies Flashcards
Where are common areas to find a leak in the breathing system
- Neck of the reservoir bag
- breathing circuits hoses
- Any hose connection
- Inlet/outlet to vaporizer
- One-way valve
- CO2 absorbing canister
- Flow meter
What should you always do before you use a breathing system
Pressure check (leak test)
What is the purpose of breathing systems
- deliver O2 +/- anestheic gases
- eliminate CO2
What are the two types of breathing systems
rebreathing and non-rebreathing
What type of breathing system is this?
Rebreathing system
AKA: circle system
What are the components of a rebreathing system
fresh gas source
unidirectional valves
breathing hoses
breathing system pressure gauge
CO2 absorber
APL valve
resivor valve
Define in simple terms how a rebreathing system works
gases flow in one-way circulation - into a patient via inspiratory hose - out of the patient through the expiratory hose
What are two advantages of using a rebreathing system
- can use lower O2 flow rates
- Easy to set up and use
What are two disadvantages of using a rebreathing system
- increased resistance for smaller patients
- more components to work with
What type of rebreathing system is defined?
- 4 - 11 mL/kg/min
- oxygen flow approximates patient oxygen consumption, which varies with metabolic rate
closed circle system
What type of rebreathing system is defined?
- 10 - 22 mL/kg/min
- Oxygen flow rate is greater than the patients oxygen consumption
Low flow circle system
What type of rebreathing system is defined?
- 22-44 mL/kg/min
- Fresh gas inflow exceeds the uptake of oxygen by patient
semi closed circle system
What type of rebreathing system is defined?
Advantages
- more economical
- retain more heat and humidity
- less likely to cause OR pollution
Disadvantages
- Vaporizer accuracy compromised
- N2O can not be used
- CO2 absorption completely dependent on chemical absorbant
Closed circle system
What type of rebreathing system is defined?
Advantages
- economical
- some heat and humidity retained
- reduced waste gas
Disadvantages
- inadequate delivery of anesthetic from a modern vaporizer
low-flow circle system
What type of rebreathing system is defined?
Advantages
- N2 accumulation insignificant
- N2O used safely
- rapid changes in inspired anesthetic concentration
- CO2 partially eliminated via pop-off valve
Disadvantages
- less economical
- more heat and humidity lost
semi-closed circle system
Calculate the maintenance oxygen flow rate for a 25 kg dog for a rebreathing system
25 kg x 22 ml/kg/min = 550 ml/min
set O2 flow meter to 600 ml/min or 0.6 L/min
calculate the oxygen flow rate for a 10 kg dog immediately after induction of anesthesia
10 kg x 44 ml/kg/min = 440 ml/min
The O2 flow meter should not be set below 0.5 L/min so even though you calculated 440 ml/min you would set it at 500 ml/min
What value should the breathing system pressure gauge be set at unless you are giving manual or mechanical ventilation
0
What value should the breathing system pressure gauge be set at when performing a leak test on the machine
0
What is the purpose of a CO2 absorption canister?
chemical reaction that removes CO2 from the rebreathing system
What happens to the patient if the CO2 absorption canister is out/exhausted
CO2 will accumulate in the circuit = rebreathing of CO2 = respiratory acidosis
What is this?
CO2 absorption cansiter
What are the components of a non-rebreathing system
fresh gas source
expiratory limb or coaxial breathing hose
open / close valve
reservoir bag
What is the typical flow rate of a non-rebreathing system
200 - 300 ml/kg/min
Which patients should use a non-rebreathing system
less than 3 kg = always use
3 to 7 kg = grey zone (anesthetist dependent)
What are three advantages of using a non-rebreathing system
- less resistance for a breathing patient
- little to no dead space
- fewer components that can leak or malfunction
What is a disadvantage of using a non-rebreathing system
- higher O2 flow rates required to get rid of CO2
- pollution to the environment and can contribute to hypothermia
What non-rebreathing systems are most commonly used in vet med
Mapleson D
- bain circuit: modified mapleson D
Mapleson F
- modified Jackson trees circuit
Why is waste air gas (WAG) so important?
sickness, pregnancy, and environmental
What pressure does the National institute for Occupational Safety and Health published recommendation that exposure to halogenated anesthetics be kept below?
2 ppm
What are some ways you can prevent exposure to WAG (6)
- engage scavenging system
- leak test
- used cuffed and correct-size endotracheal tubes
- Use low flow circle system is possible
- avoid mask and chamber induction
- disconnect patient before turning them
- machine maintenance
- Adequate ventilation of areas where anesthesia exposure occurs
Give an example of tips that can be used when filling or emptying vaporizers
- ideally, wear a charcoal mask
- announce what you are doing so others can leave if they desire/need to
- Select a time late in the day to avoid unnecessary exposure
- replace cap on bottle when doing filling the anesthesia
- switch to key fill vaporizers if possible
- always turn vaporizer dial off before filling
What are the two types of scavenging systems
passive and active
Describe passive scavenging systems
charcoal absorption to outside wall or window
Describe active scavenging systems
central vacuum collection
What type of gasses do charcoal absorb and not absorb
absorb
- halogenated anesthetic gases
- sevo , des, iso
non-absorbable
- CO2
- N2O
What are the advantages to charcoal absorption
mobile
initial cost is low
easy to set up
What are some disadvantages to charcoal absorption
- must be replaced after gaining 50 grams in weight
- use limited to lower oxygen flow rates
- adds resistance
- environmental impact
What type of interface protects the breathing circuit and patient from excessive positive or negative pressures
active scavenging
Where is the active scavenging located on the machine
between the pop-off valve and disposal system
Clinical Case:
You are approached by a co-worker who is concerned about exposure to anesthetic waste gas because they reveal they are pregnant. What advice could you offer this person?
Tell them they need to meet with their primary care provider
- Once that is done you can talk about ways to prevent exposure in the future
How can you determine what size endotracheal tube is needed for a patient and what are the boundaries
- you want to use the largest size of ETT that will fit without causing trauma to the trachea
- palpate the trachea to estimate size needed. Length should not extend distally beyond the thoracic inlet or rostrally beyond incisors
What are some types of ETT and what might they be made out of?
types
- murphy (most common)
- magill
- cole
- guarded
material
- PVC
- silicone
- rubber
Define dead space related to ETT
Portions of the breathing passage that contains air, but there is no gas exchange
Give examples of dead space
- mouth
- nasal passage
- pharynx
- trachea
- end of ET tube / Y piece
What type of endotracheal tube is described below?
- an oval hole positioned on the bevel facing the opening of the tube
- if the distal end of the tube becomes occluded, there is still airflow
- Magill tube is the same design, except no “eye”
Murphy type
- they have the Murphys eye that still allows for breathing
What type of ETT is this?
- this has an “eye”
Murphys type
What type of ETT tube is this?
- this does not have an “eye”
Magill tube
What type of endotracheal tube is described below?
- uncuffed
- characterized by a shoulder
- designed to create a seal by using a smaller end to fit in the arytenoid cartilages
- smaller portion goes in the trachea
Cole tube
What type of ETT tube is this?
Cole tubes
What type of endotracheal tube is described below?
- much larger, usually available in 16-30 mm
large animal ETT
What type of endotracheal tube is described below?
- made of silicone rubber
- have steel wire or nylon coil embedded in the wall
- resists kinking (good for optho cases of CSF taps
- more expensive
guarded or armored tubes
What type of tube is this?
guarded or armored tubes
What is a laryngeal scope used for
- allows for visualization
- light source
- easier to accessibility to airway
How do you place a laryngoscope for best visibility?
- apply light pressure to base of tongue
(underneath the epiglottis) - tilts larynx ventrally and opens glottis (frees up the epiglottis if still tucked underneath soft palate)
What are the steps for intubation?
What are some methods used to confirm ETT placement
Describe the cuff inflation technique
- aka: minimal occlusion volume technique
- can utilize an esophageal stethescope to accomplish the desired effect
- there should be no escape of gas from around the endotraheal tube when delivering a positive pressure ventilation and the bag is squeezed
How much air should be able to escape around the tube, if not some air should be removed from pilot ballon to prevent over-inflation of the cuff ?
20 to 30 cm
around 22 cm H2O air
What is this device?
cuff pressure manometer
What is this device?
Supraglottic airway device
What is this device?
Ambu bag
What is this device?
- used in LA medicine
demand valve
NAVLE Questions:
What might happen if you push the oxygen flush button on an anesthetic machine?
- flow rate increases
- the patient may start to wake up
- oxygen is flushed out of the system
- the patient will go to a deeper anesthetic plane
- anesthetic gas concentration goes up in the breathing machine
Flow rate increases
What fresh gas flow rate is typical of a non-breathing anesthetic machine?
50 - 150 ml/kg/min
200 - 300 ml/kg/min
30 - 50 ml/kg/min
150 - 200 ml/kg/min
200 - 300 ml/kg/min
