Lecture 4: Breathing systems, scavenging, & intubation supplies (Exam 1) Flashcards
What are some areas to find a leak
- Neck of the reservoir bag
- Breathing circuit hoses
- Any hose connection
- Inlet/outlet to vaporizer
- One-way valves
- CO2 absorbing canister
- Flow meter
What is the purpose of breathing machines
Deliver O2 +/- anesthetic gases & eliminate CO2
What are the types of breathing systems
- Rebreathing
- non-rebreathing
What are the components of the rebreathing system
- Fresh gas source
- Unidirectional valves
- Breathing hoses
- Breathing system pressure gauge
- CO2 absorber
- APL valve
- Reservoir bag
How does the rebreathing system work
- Gases flow in a one way circular pattern
- Then into a px via inspiratory hose
- then out of the px through expiratory hose
How is rebreathing of CO2 prevented in a rebreathing system
By chemical absorption but other gases can be passed again to the px
What are the advantages of a rebreathing system
- Can use lower O2 flow rate
- Easy to set up & use
What are the disadvantages of the rebreathing system
- Increased resistance for smaller px
- More components to work w/
What are the recommended O2 flow rates for a closed circle (rebreathing) system
- 4 - 11 mL/kg/min
- Oxygen flow approx px’s oxygen consumption which varies w/ metabolic rate
What are the advantages & disadvantages of a closed circle system
- Advantages: More economical, retain more heat & humidity, & less likely to cause OR pollution
- Disadvantages: Vaporizer accuracy compromised, N2O can not be used, & CO2 absorption completely dependent on chemical absorbent
What is the recommended oxygen flow rates of the low flow circle (rebreathing) system
- 10 to 22 mL/kg/min
- Oxygen flow rater greater than the px oxygen consumption
What are the advantages & disadvantages of low flow circle system
- Advantages: Economical, some heat & humidity retained, & reduced waste gas
- Disadvantages: Inadequate delivery of anesthetic from modern vaporizer
What is the recommended oxygen flow rates for a semi-closed circle system
- 22 - 44 mL/ kg/min
- Fresh gas inflow exceeds the uptake of oxygen by px
What are the advantages & disadvantages of a semi-closed circle system
- 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 & humidity lost
Answer the math problem & Determine what the O2 flow meter should be set at
Answer the math problem & Determine what the O2 flow meter should be set at
Label the hose & who they are used for
- B = pediatric hose for px < 15lb
- A = Adult hose for px 15 - 300 lb
- C = Universal-F hose generally used in larger px
Describe the breathing system pressure gauge
- Measures the existing pressure w/in a breathing system
- Differs from oxygen cylinder pressure gauge which is read in psi
- Should remain @ zero unless giving a manual or mechanical ventilation
- Also used when performing a leak test on the machine
1 mmHg = ? cm H2O
1.36
Describe the CO2 absorption canister
- Chemical reaction removes CO2 from the rebreathing system
- Once the product is exhausted CO2 will accumulate in the circuit which lead to rebreathing CO2 that will cause respiratory acidosis
What can be used to determine when to change soda limem
- Simply mark off # of hours used
- Capnography (increased inspired CO2 & ETCO2)
- Color change (not reliable)
- Lack of heat i canister
- Hardness of granules
- Clinical signs in px
How much should be left in the soda lime to avoid tightly packing of granules
1 to 2 cm
What are the components of the non-rebreathing system
- Fresh gas source
- Expiratory lib or coaxial breathing hose
- Open/close valve
- Reservoir bag
What is the typical O2 flow rates of non-rebreathing sys
200-300 mL/kg/min
What px should use a non-rebreathing sys
- If < 3 kg can always use
- 3 to 7 kg is a grey zone & is anesthetist dependent
What is the advantages of a non-rebreathing system
- Less resistance to breathing for px
- Little to no dead space
- Fewer components that can leak or malfunction
What are the disadvantages of non-rebreathing systems
- Higher O2 glow rates req to get rid of CO2
- Pollution to the environment
- Can contribute to hypothermia
What are the common non rebreathing systems used in vet med
- Mapleson D
- Bain circuit (Modified Mapleson D)
- Mapleson F
Why is waste air gas (WAG) scavenging important
National institute for occupational safety & Healthy published recommendations that exposure to to halogenated anesthetic agents be kept below 2 ppm
How can you prevent exposure
- Engage a scavenging system
- Leak test the machine & breathing system prior to use
- Used cuffed & correctly sized endotracheal tubes
- Use a low flow circle system if possible
- Avoid mask & chamber inductions
- When disconnecting the px turn off the flow meter, vaporize, empty gas from bag in to scavenging & occlude Y piece
- Perform machine & equipment maintenance periodically
- Adequate ventilation of areas where anesthetic gas exposure occurs
What are the tips for filling or emptying vaporizers
- Ideally wear a charcoal mask
- Always announce that you are filling a vaporizer if it must occur when other personnel are in the room
- Best to select a time late in the day (or first thing in the am) to refill vaporizers to min unnecessary exposure
- Replace cap on the bottle when done
- Switch to key-fill vaporizers if possible
- Always turn vaporizer dial OFF before filling
What are the 2 types of scavenging systems
- Passive (charcoal absorption to outside wall or window)
- Active (Central vacuum collection)
Describe charcoal absorption
Absorbs halogenatated anesthetic gases but does NOT absorb CO2 or N2O
What are the advantages of charcoal absorption
- Mobil
- Initial cost is low
- Easy to set up
What are the disadvantages of charcoal absorption
- Must be replaced after gaining 50 grams in weight (usually 8 to 12 hours of use)
- Use limited to lower oxygen flow rates
- Adds resistance
- Environmental impact
Describe active scavenging
- Interface protect the breathing circuit & px from excess positive or negative pressure
- Located btw/ the pop-off valve & disposal system
*Cost more than passive but is more effective
Describe endotracheal tubes (ETT)
- Made of PVC, silicone, or red rubber
- Sized according to internal diameter (ID) or french gauge (in mm)
- Want to use the largest size of ETT that will fit w/out 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 the types of ETT
- Murphy
- Magill
- Cole
- Guarded or armored
Define dead space
- Portions of the breathing passages that contain air but there is no gas exchange
- Ex. Mouth, nasal passages, pharynx, trachea, & end of ET tube/ Y-piece
Describe the murphy Edo tube
- “Murphy eye” - Has an oval hole positioned on the bevel facing the opening of the tube
- If distal end of the tube becomes occluded there is still air flow
- Magill tube is the same design just no “eye”
Describe the cole tube
- Uncuffed
- Has a “shoulder” near the distal end (Laryngotracheal portion)
- Designed to create a seal by using a smaller end to fit in the arytenoid cartilages
- Smaller portion goes in the trachea
Describe large animal ETTs
Much larger (16 - 30 mm size)
Describe guarded or armored tubes
- Made of silicone rubber
- Have steel wire or nylon coil embedded in the wall
- Resists kinking (good for optho cases or CSF tap)
- More expensive
Describe laryngoscope
- Allows visualization
- Light source (allows for quick detection of abnorm anatomy)
- Easier accessibility to airway
- Apply light pressure to base of tongue, just underneath epiglottis
- Tilts larynx ventrally & opens glottis, frees up the epiglottis if still tucked underneath the soft palate
What are the steps for correct Endotracheal intubation placement
What are some methods to confirm ET placement
- Canograph reading from ETT registers high enough CO2 values
- Direct observation of ETT going into trachea
- Condensation seen on inside of ETT
- Feel breath from end of ET tube on hand or movement of plucked hairs
- Outward movement of chest wall when positive pressure ventilation given
- Auscultation of breaths sounds bilaterally when breath given
- Reservoir bag & exhalation valve movement
- Absence of two “tubes” palpated b/c ETT is inside the trachea
- Feel the ETT sliding pas tracheal rings
What is the cuff inflation tech
- not considered accurate
- Utilize an esophageal stethoscope to accomplish the desired effect
- No escape of gas from around the ETT cuff when delivering a pos pressure ventilation & the bag is squeezed to ~20 cm H2O
List some respiratory assist devices
