Breathing Systems, ET Tubes, and Scavenging

Question 1

what are the 2 types of patient breathing systems

Answer 1

re-breathing and non-rebreathing

Question 2

what are the types or rebreathing systems

Answer 2

circle

universal F

Question 3

what are the types of non-rebreathing systems

Answer 3

mapleson A-F

Most common - modified mapleson D, mapleson F

Question 4

what is anatomic dead space

Answer 4

airway structures that do not participate in gas exchange

Question 5

what is mechanical dead space

Answer 5

portion of the anesthesia circuit where bidirectional flow is occuring (rebreathing of exhaled gases)

if excessive may cause an unsafe increase in inspired CO2

Question 6

sources of mechanical dead space

Answer 6

face mask

ET tube extending past patient’s incisors

capnograph or other adapters

y-piece

Question 7

T/F breathing tubes in a circle system do not constitute dead space becuase they flow is unidirectional (no rebreathing)

Answer 7

True

why breathing tubes may be long - ex. anesthesia machine palced outside MRI room

Question 8

T/F dead space in a non-rebreathing system consists of the space between the fresh gas flow inlet and the patient

Answer 8

True

differs depending on mapleson type

Question 9

components of re-breathing system

Answer 9

fresh gas input and O2 flush

unidirectional valves (inspiratory and expiratory)

breathing hoses

CO2 absorber

adjustable pressure limiting valvue (pop-off)

reservoir bag

Question 10

T/F patient rebreathes gases via the inspiratory valve

Answer 10

True

composed of exhaled gases adter CO2 removal and fresh gas flow

Question 11

advantages of re-breathing system

Answer 11

lower fresh gas flow rate required

patient breaths warm, humidifed gases

saves money

decreases environmental pollution

Question 12

disadvantages of re-breathing system

Answer 12

higher resistnace to breathing due to valves

changes in anesthetic gas concentration occur slowly (lower fresh gas flow)

more components → morepotential for leaks

Question 13

what is the shared connection between re-breathing and non-rebreathing systems

Answer 13

fresh gas inlet

Question 14

Adjustable pressure-limiting (APL) valve or pop-off

Answer 14

limits pressure build-up in breathing system

should “pop-off” at 3-5 cmH20

Question 15

when should pop-off be closed

Answer 15

checking the machine for leaks

administering positive pressure ventilation (manual or mechanical)

Question 16

what can happen if the pop-off valve is cloed

Answer 16

increased pressure in breathing system (fresh gas flow continues with no exhaust) → cardiorespiratory arrest and death

Question 17

breathing circuit pressure gauge

Answer 17

should be 0 +/- 1 with spontaneous patient breathing

exception - leak check, positive pressure ventilation

Question 18

what color does the carbon dioxide absorber (soda lime) change when exhausted

Answer 18

white → purple

Question 19

T/F color change in the absorbant can be seen when active and does not mean it is exhausted

Answer 19

True

Question 20

what are signs of CO2 absorbant exhaustion

Answer 20

inspired CO2 is > 1-2 mmHg on capnograph (= rebreathing)

increased PaCO2 on blood gas

Question 21

patient signs with CO2 absorbant exhaustion

Answer 21

increased RR (compensation)

increased HR ad BP (CO2 → sympathetic stimulation)

red mucous membranes (CO2 induced vasodilation)

Question 22

function of reservoir bag

Answer 22

inspiratory reserve for patient

administering positive pressure ventilation

allows anesthetist to monitor ventilation

Question 23

how do you calculate bag size for small animals

Answer 23

15 mL/kg x 6

short cut: (BW in kg) x 90

Question 24

oxygen flow rate

Answer 24

many different rates can be used

all are safe for patients as long as greater than metabolic O2 requirement (5-10 mL/kg/min)

Question 25

typical O2 flow rate for small animals (\<50 kg) **includes sheep under 50 kg**

Answer 25

induction and recovery 50-100 mL/kg/min maintenance 20-50 mL/kg/min

Question 26

typical O2 rate for larger animals

Answer 26

induction and recovery: 20-50 mL/kg/min maintenance: 10-20 mL/kg/min

Question 27

advantages of non-rebreathing systems

Answer 27

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

Question 28

disadvantages of non-rebreathing system

Answer 28

requires high gas flow rates patient breaths cold and dry gas more expensive increases environmental pollution

Question 29

oxygen flow rates for non-rebreathing system

Answer 29

should be 2-3x tidal volume 300mL/kg/min

Question 30

which monitor would help determine if the O2 flow rate was too low and patient was rebreathing CO2

Answer 30

capnograph

Question 31

indications for ET tube and intubation

Answer 31

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

Question 32

types of ETT

Answer 32

murphy cole wire-reinforced

Question 33

routes of intubation

Answer 33

oral (most common) nasal tracheal (tracheostomy) pharyngotomy

Question 34

characterisitcs of murphy

Answer 34

cuffed or uncuffed has "murphy eye" that allows gas flow if end of tube is obstructed most common

Question 35

T/F tubes with larger radius and shorted length will have less resistance to gas flow

Answer 35

**True** radius has the largest effect

Question 36

T/F side of the tube is measured in mm and indicates an internal diameter

Answer 36

**True**

Question 37

laryngoscope

Answer 37

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

Question 38

T/F inflate cuff a little first and then check to see if there is a leak

Answer 38

**False** exception: ruminants-air should be added before any movement, high risk of regurgitation

Question 39

what can cause tracheal damage

Answer 39

over-inflated cuff moving or twisting patient with inflated cuff

Question 40

complication of intubation

Answer 40

ETT obstruction endobronchial intubation ETT inhalation or ingestion

Question 41

types of scavenging systems

Answer 41

active passive

Question 42

how can you minimize waste gas exposure

Answer 42

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

Question 43

passive scavenging systems

Answer 43

no vacuum exhaust directly to atmosphere F-air canister

Question 44

Advantages of F air canister

Answer 44

absorbs anesthetic vapors does not release to atmosphere portable

Question 45

disadvantages to F air canister

Answer 45

does not absorb N2O flow-limited added resistance must be discarded when canister has gained 50g (weight before starting and PRN)

Question 46

other sourses of waste gas pollution

Answer 46

capnograph face mask and chamber induction recovery areas (large animals) volitile agent spills