Breathing Systems, ET Tubes, and Scavenging Flashcards
what are the 2 types of patient breathing systems
re-breathing and non-rebreathing
what are the types or rebreathing systems
circle
universal F
what are the types of non-rebreathing systems
mapleson A-F
Most common - modified mapleson D, mapleson F
what is anatomic dead space
airway structures that do not participate in gas exchange
what is mechanical dead space
portion of the anesthesia circuit where bidirectional flow is occuring (rebreathing of exhaled gases)
if excessive may cause an unsafe increase in inspired CO2
sources of mechanical dead space
face mask
ET tube extending past patient’s incisors
capnograph or other adapters
y-piece
T/F breathing tubes in a circle system do not constitute dead space becuase they flow is unidirectional (no rebreathing)
True
why breathing tubes may be long - ex. anesthesia machine palced outside MRI room
T/F dead space in a non-rebreathing system consists of the space between the fresh gas flow inlet and the patient
True
differs depending on mapleson type
components of re-breathing system
fresh gas input and O2 flush
unidirectional valves (inspiratory and expiratory)
breathing hoses
CO2 absorber
adjustable pressure limiting valvue (pop-off)
reservoir bag
T/F patient rebreathes gases via the inspiratory valve
True
composed of exhaled gases adter CO2 removal and fresh gas flow
advantages of re-breathing system
lower fresh gas flow rate required
patient breaths warm, humidifed gases
saves money
decreases environmental pollution
disadvantages of re-breathing system
higher resistnace to breathing due to valves
changes in anesthetic gas concentration occur slowly (lower fresh gas flow)
more components → morepotential for leaks
what is the shared connection between re-breathing and non-rebreathing systems
fresh gas inlet
Adjustable pressure-limiting (APL) valve or pop-off
limits pressure build-up in breathing system
should “pop-off” at 3-5 cmH20
when should pop-off be closed
checking the machine for leaks
administering positive pressure ventilation (manual or mechanical)
what can happen if the pop-off valve is cloed
increased pressure in breathing system (fresh gas flow continues with no exhaust) → cardiorespiratory arrest and death
breathing circuit pressure gauge
should be 0 +/- 1 with spontaneous patient breathing
exception - leak check, positive pressure ventilation
what color does the carbon dioxide absorber (soda lime) change when exhausted
white → purple
T/F color change in the absorbant can be seen when active and does not mean it is exhausted
True
what are signs of CO2 absorbant exhaustion
inspired CO2 is > 1-2 mmHg on capnograph (= rebreathing)
increased PaCO2 on blood gas
patient signs with CO2 absorbant exhaustion
increased RR (compensation)
increased HR ad BP (CO2 → sympathetic stimulation)
red mucous membranes (CO2 induced vasodilation)
function of reservoir bag
inspiratory reserve for patient
administering positive pressure ventilation
allows anesthetist to monitor ventilation
how do you calculate bag size for small animals
15 mL/kg x 6
short cut: (BW in kg) x 90
oxygen flow rate
many different rates can be used
all are safe for patients as long as greater than metabolic O2 requirement (5-10 mL/kg/min)
typical O2 flow rate for small animals (<50 kg) includes sheep under 50 kg
induction and recovery 50-100 mL/kg/min
maintenance 20-50 mL/kg/min
typical O2 rate for larger animals
induction and recovery: 20-50 mL/kg/min
maintenance: 10-20 mL/kg/min
advantages of non-rebreathing systems
light, minimal dead space, minimal resistance to ventilation (use for small patients <3 kg)
concentration of anestheitc gas changes rapidly due to high fresh gas flow
few components = fewer potential for leaks
disadvantages of non-rebreathing system
requires high gas flow rates
patient breaths cold and dry gas
more expensive
increases environmental pollution
oxygen flow rates for non-rebreathing system
should be 2-3x tidal volume
300mL/kg/min
which monitor would help determine if the O2 flow rate was too low and patient was rebreathing CO2
capnograph
indications for ET tube and intubation
maintain patent airway
administer O2, deliver inhalant anesthetics
provide positive pressure ventilation
protect airway from foreign material
apply tracheal and bronchial suction (transtracheal wash)
decreases environmental contamination if cuff is properly inflated
types of ETT
murphy
cole
wire-reinforced
routes of intubation
oral (most common)
nasal
tracheal (tracheostomy)
pharyngotomy
characterisitcs of murphy
cuffed or uncuffed
has “murphy eye” that allows gas flow if end of tube is obstructed
most common
T/F tubes with larger radius and shorted length will have less resistance to gas flow
True
radius has the largest effect
T/F side of the tube is measured in mm and indicates an internal diameter
True
laryngoscope
make intubation safer and easier
allows visualization of airway
apply light pressure to base of tongue, rostral to epiglotis
DO NOT place the blade of the laryngoscope on the epiglottis
T/F inflate cuff a little first and then check to see if there is a leak
False
exception: ruminants-air should be added before any movement, high risk of regurgitation
what can cause tracheal damage
over-inflated cuff
moving or twisting patient with inflated cuff
complication of intubation
ETT obstruction
endobronchial intubation
ETT inhalation or ingestion
types of scavenging systems
active
passive
how can you minimize waste gas exposure
scavenge all the time
ensure that the machine has no leaks
use ETT with properly inflated cuff
avoid mask of chamber induction
check for tight fitting
use low O2 flows
maintain appropriate room ventilaion
use keyed systems for filling vaporizers
passive scavenging systems
no vacuum
exhaust directly to atmosphere
F-air canister
Advantages of F air canister
absorbs anesthetic vapors
does not release to atmosphere
portable
disadvantages to F air canister
does not absorb N2O
flow-limited
added resistance
must be discarded when canister has gained 50g (weight before starting and PRN)
other sourses of waste gas pollution
capnograph
face mask and chamber induction
recovery areas (large animals)
volitile agent spills
