Anesthesia Circuits

Question 1

Any portion of the airway that does not participate in gas exchange

Answer 1

Dead space

Question 2

True/false: Dead spaces causes us to rebreathe CO2 with every breath

Answer 2

True

Question 3

Anatomic dead space

Answer 3

Pharynx, trachea, bronchi

2ml/kg

Question 4

Physiologic dead space

Answer 4

Alveolar spaces that receive air but no blood flow

Question 5

Physiology of smokers

Answer 5

1. Alveolar sacs fuse into blebs (bullae)
2. Excess mucus forms in the bronchioles
3. Pulmonary capillaries get destroyed

Question 6

Mechanical dead space

Answer 6

Anesthesia airway equipment (circuit tubing, humidifiers, ETT)

Question 7

Which has less dead space? Masks, LMAs, or ETT?

Answer 7

ETTs have less, then LMAs, then masks

Question 8

True/false: Even though dead space is fixed, when a patient takes a larger breath, a lower percentage of that will be dead space?

Answer 8

True

Question 9

Perfused, but not ventilated

Answer 9

Pulmonary shunt

v/Q

Question 10

Ventilated, not perfused

Answer 10

Dead space

V/q

Question 11

Most common cause of hypoxemia

Answer 11

V/Q mismatch most likely due to atelectasis (v/Q, shunt)

Question 12

v/Q

Answer 12

Pulmonary shunt

Question 13

V/q

Answer 13

Dead space

Question 14

Is a pneumothorax a shunt or dead space?

Answer 14

v/Q, pulmonary shunt

Question 15

Pulmonary embolism: shunt or dead space?

Answer 15

V/q, dead space

Question 16

Pulmonary edema: shunt or dead space?

Answer 16

v/Q, pulmonary shunt

Question 17

Atelectasis: shunt or dead space?

Answer 17

v/Q, pulmonary shunt

Question 18

Increase in pulmonary vascular resistance: shunt or dead space?

Answer 18

V/q, dead space

Question 19

R mainstem intubation: shunt or dead space?

Answer 19

v/Q pulmonary shunt

Question 20

Top lung in lateral decubitus position: shunt or dead space?

Answer 20

V/q, dead space

Question 21

Lower lung in lateral decubitus position: shunt or dead space?

Answer 21

v/Q, pulmonary shunt

Question 22

Emphysema: shunt or dead space?

Answer 22

Both (due to bullae and mucus plugs)

Question 23

Spontaneous ventilation under GA: shunt or dead space?

Answer 23

v/Q, pulmonary shunt

Question 24

NTG (inc pulmonary vasculature and blood flow): shunt or dead space?

Answer 24

v/Q, pulmonary shunt

Question 25

Drop in cardiac output due to internal hemorrhage: shunt or dead space?

Answer 25

V/q, dead space

Question 26

Types of circuits used in anesthesia

Answer 26

1. Open circuits (nasal cannula, insufflation/blow by, open drop anesthesia 2. Partial re-breathing circuits (anesthesia circuits, oxygen masks) 3. Non-rebreathing circuits (T-piece, nonrebreather mask)

Question 27

What are open circuits primarily used for?

Answer 27

Oxygen delivery

Question 28

Max FiO2 for nasal cannula

Answer 28

44% (reached at 6L/min)

Question 29

How to calculate FiO2 with nasal cannula

Answer 29

21% + 4% for each L/min

Question 30

Hazards of nasal cannula use

Answer 30

1. Dries out nares at >4L/min flows | 2. Can increase risk of fire for facial surgeries/where cautery is used near face

Question 31

When is insufflation (blow by) used?

Answer 31

When a patient is claustrophobic, anxious, or won't tolerate the mask well During sedation/scope cases Facial surgeries to prevent CO2 accumulation under the drapes (use air, NOT O2)

Question 32

Types of partial rebreathing circuits

Answer 32

1. Semi-closed partial rebreathing circuits (used on our machines) 2. Semi-open partial rebreathing circuits (Mapleson) 3. Partial rebreathing O2 masks (simple face mask, venturi mask, ambu bag, "nonrebreathing" mask on lower flows

Question 33

Advantages and disadvantages to rebreathing circuits

Answer 33

Advantage: Conserves heat and humidity Disadvantage: Slower wake up on emergence and potential for CO2 retention/hypercarbia

Question 34

How can you prevent rebreathing in partial rebreathing circuits?

Answer 34

Increase fresh gas flow, or by opening the APL valve if applicable

Question 35

What do you do if you want to use an LMA or ETT outside of the operating room?

Answer 35

Transport an anesthesia machine to the room and hook it up to scavenging Use a mapleson circuit

Question 36

Best mapleson circuit for spontaneous ventilation

Answer 36

Mapleson A -APL valve closer to patient, FGF at end of circuit

Question 37

Best mapleson circuit for control ventilation

Answer 37

Mapleson D -FGF closer to patient, APL valve at end of circuit

Question 38

Mapleson circuits are primarily used for:

Answer 38

Delivering oxygen

Question 39

Advantage of Mapleson Circuits

Answer 39

Can hook them up to ETT or LMA for GA (TIVA) | Can deliver positive pressure ventilation

Question 40

Disadvantage of Mapleson Circuits

Answer 40

More dead space = more potential to rebreathe CO2 | No CO2 absorber and no inspiratory or expiratory valves

Question 41

Purpose of T piece

Answer 41

When a patient is breathing on their own but not ready to wake up yet To limit/decrease rebreathing CO2. Oxygen goes in one side and CO2 comes out the other

Question 42

Disadvantage of T piece

Answer 42

Cannot use positive pressure

Question 43

Advantages of a coaxial circuit

Answer 43

Conserves heat and humidity

Question 44

Disadvantage to a coaxial circuit

Answer 44

Possibility of disconnection or kink in tubing

Question 45

Open during inspiration, closed during expiration

Answer 45

Inspiratory valve

Question 46

Open during expiration, closed during inspiration

Answer 46

Expiratory valve

Question 47

Purpose of unidirectional valves

Answer 47

So the patient does not rebreathe CO2

Question 48

When is a CO2 absorber practically unneccesary?

Answer 48

When fresh gas flows over 5L/min are running

Question 49

Desiccated "old school" granules will:

Answer 49

1. Degrade all volatile agents into carbon monoxide (desflurane is the worst) 2. Accelerate the degradation of sevoflurane into compound A

Question 50

AIAAAH recommends a humidity range of ___ for the OR

Answer 50

30-60%

Question 51

FiO2 for a simple face mask

Answer 51

40% at 5L/min | 60% at 10L/min

Question 52

FiO2 for nonrebreathing mask

Answer 52

80s at 10L/min | 90s at 15L/min

Question 53

Maximum FiO2 of venturi mask

Answer 53

60% | also depends on the adapter

Question 54

Purpose of supplemental oxygen

Answer 54

To compensate for: 1. atelectasis 2. anesthetic induced hypoventilation

Question 55

Supplemental oxygen is most often given:

Answer 55

During MAC In transport from OR to PACU In the PACU

Question 56

Airway resistance equation (and what each variable means)

Answer 56

R= 8ul/π(r^4) R: resistance u: viscosity of air l: length of circuit r: radius

Question 57

What does the Hagen Poiseuille equation tell us?

Answer 57

1. Adding dead space (length) to a circuit increases resistance 2. Resistance can minimized if: the diameter of the equipment is bigger or the length of the equipment is shorter (diameter has a bigger effect than length)