Basic Anesthesia Machine Concepts Flashcards

1
Q

ASA 4 monitoring standards

A

1.) oxygenation (pulse ox)
2.) ventilation (etCO2)
3.) circulation (blood pressure and ECG)
4.) temperature

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2
Q

Why is BP measurement important

A

It is how we know the patients is being adequately perfused

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3
Q

BP ranges

A

Normal: 120/80
Hypertension: >140/90
Hypotension: <90/60

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4
Q

Mean Arterial BP

A

Average pressure during one cardiac cycle. AVG = 70-100mmHg
MAP=[(2xDiastolic BP)+Systolic BP]/3

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5
Q

What is pulse pressure

A

Systolic minus diastolic
Normal is: 30-40mmHg

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6
Q

End tidal CO2

A

Amount of carbon dioxide in expired air. Normal range is 35-45mmHg

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7
Q

2 main functions of EtCO2

A

1.) reveal patients EtCO2
2.) Reveal patients respiratory rate

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8
Q

Normal core body temperature

A

36-38 degrees celsius

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9
Q

2 main purposes of the anesthesia machine

A

1.) Allows an anesthetist to deliver anesthetic gas to keep the patient asleep
2.) Allows an anesthetist to ventilate a patient with positive pressure ventilation

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10
Q

Volatile agents

A

Sevoflurane, Isoflurane, Desflurane

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11
Q

Fresh gas flow gases

A

Oxygen, air, and Nitrous oxide

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12
Q

Y-piece

A

Merges the inspiratory and expiratory limbs

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13
Q

Elbow adapter

A

allows the circuit to more easily connect to the mask or ETT

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14
Q

Humidifier

A

filters out bacteria and viruses, and humidifies the dry gases that come from the machine

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15
Q

Gas sampling line

A

Measures the exhaled gases (oxygen, CO2, and volatile agent). Connected to the elbow adapter or the humidifier

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16
Q

What controls the fresh flow gases

A

Flow control valves or rotameters

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17
Q

Anesthesia flowmeters

A

Indicate how much each gas is entering the circuit each minute

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18
Q

Using oxygen as fresh flow gas

A

1.) Higher fiO2 compensates for atelectasis
2.) Some patients (lung disease, COPD) may need higher FiO2 in order to have an adequate oxygen saturation
3.) The higher FiO2 allows the patient to maintain adequate oxygen saturation for longer periods in case of unexpected apnea

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19
Q

Using nitrous oxide as fresh flow gas

A

1.) Only anesthetic gas that has analgesic properties
2.) allows an anesthetist to use lower concentrations of volatile agent

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20
Q

Using air as fresh flow gas

A

Benefit is that it allows us to use a lower FiO2 which is good because:
1.) Too much oxygen for too long can be toxic (Free radicals) especially in neonates it can cause “retinopathy of prematurity”
2.) High FiO2 can cause “absorption atelectasis”
3.) An FiO2 above 30% and/or use of nitrous oxide increases the risk of airway fire

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21
Q

Two fresh flow gas supplies

A

1.) Wall supply (H cylinder)
2.) E cylinder (tank) supply

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22
Q

Green hose

A

Oxygen

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23
Q

Blue hose

A

Nitrous oxide

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24
Q

Yellow hose

A

air

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25
Q

Diameter index safety system (DISS)

A

Prevents us from connecting the machine to the wrong wall supply hose

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26
Q

Pin index safety system (PISS)

A

Prevents us from connecting the machine to the wrong gas tank

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27
Q

Flowmeter mechanical proportioning system

A

Limits the % of nitrous oxide that can be given to a patient. Max nitrous oxide to oxygen ratio allowed is 3:1. Minimum oxygen concentration allowed with nitrous oxide is 25%

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28
Q

Low pressure pathway

A

1.) Flowmeters
2.) Common manifold
3.) Vaporizers
4.) Fresh (common) gas outlet
5.) Inspiratory tubing of circuit
6.) Patient
7.) Expiratory tubing of circuit
8.) Rebreathing bag or ventilator
9.) CO2 absorber & APL valve
10.) Exhaled gas joins fresh gas outlet

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29
Q

Scavenging system

A

takes excess gas away from the circuit (purple hose)

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30
Q

Adjustable Pressure Limiting (APL) valve

A

controls the amount of gas going to the scavenging system. Also known as the “pop off valve” or “pressure relief valve”

31
Q

APL valve open

A

Patient breathing on their own. Open counterclockwise

32
Q

APL valve partially closed

A

Increases the pressure in the system and allows the anesthetist to ventilate with positive pressure. turn knob clockwise

33
Q

3 things APL valve controls

A

1.) the amount of gas flow that goes to scavenging
2.) amount the patient rebreathes
3.) pressure in the circuit

34
Q

Oxygen flush valve

A

Allows 50psi to enter the circuit and bypass the low pressure circuit. Used for building up pressure in situations where it difficult to prevent a circuit leak (difficult seal)

35
Q

Possible circuit leak problems (can’t build up pressure)

A

1.) loose mask seal
2.) disconnected circuit at ETT
3.) Cap off on humidifier
4.) Exhaled gas sampling line connection
5.) Disconnected inspiratory/expiratory limb of circuit
6.) Deflated ETT cuff

36
Q

Managing leak during mask ventilation

A

1.) improve seal around mask
2.) place oral airway
3.) use two hands to mask over the patient’s face
4.) pressing the oxygen flush button

37
Q

Managing leak after intubation

A

Start at the patient and then follow back to the machine

38
Q

Ways to increase circuit pressure

A

1.) turn up the fresh gas flow
2.) close APL valve
3.) press oxygen flush button
4.) avoid leak in the circuit (maintain good mask seal)

39
Q

Mask ventilation airway pressure

A

Do not exceed 20cmH20 (air could enter stomach)

40
Q

ETT tube airway pressure

A

Do not exceed 40cmH20 (barotrauma of the lungs can occur)

41
Q

Bag Mode “manual/spontaneous mode”

A

Ventilator is not turned on and is not part of the circuit (exhaled has flows through breathing bag)

42
Q

Ventilator mode

A

Ventilator is turned on and will be delivering positive pressure breathes

43
Q

Common situations for mask ventilation

A

1.) After induction but before intubation
2.) Mask induction
3.) Failed intubation
4.) Any other unexpected apnea, like over sedation or absence of patient ventilation after extubation

44
Q

Spontaneous ventilation

A

Breathing on their own. At Liberty it (negative pressure) shows up as grey

45
Q

Mode for spontaneous breathing

A

Manual/spontaneous mode or pressure support ventilation mode

46
Q

Assist ventilation

A

Squeezing the breathing bag just as the patient starts to inhale to achieve a greater tidal volume

47
Q

Mode for assist ventilation

A

Tradition way: bag/manual/spontaneous mode and we squeeze as we feel the bag deflating
New way: pressure support mode automatically assists with breathing. Almost always use this except for right before extubation

48
Q

Mechanical ventilation (control ventilation)

A

Breathing for a patient with positive pressure ventilation. Can be squeezing the bag (manual/spontaneous mode) or putting the patient on the ventilator (ventilator mode)

49
Q

Mechanical (positive pressure) breaths

A

Show up as green at Liberty hospital

50
Q

Two things we set when using ventilator

A

1.) respiratory rate
2.) tidal volume

51
Q

Three ways to abolish patient’s respiratory drive

A

1.) administering muscle relaxants
2.) higher doses of narcotics
3.) giving propofol

52
Q

Tidal volume setting

A

6-8mL/kg

53
Q

Respiratory rate settings

A

8-12 breathes per minute but also determines how long each breath is

54
Q

Longer breathes generate

A

lower pressure in the lung

55
Q

Short breathes generate

A

higher pressure in the lungs

56
Q

Peak Inspiratory Pressure (PIP) or Pmax

A

Max amount of pressure you are willing to give in order to expand the lungs with ventilator (keep under 35-40cmH20)

57
Q

Common causes of high PIP

A

1.) Right mainstream intubation
2.) Bronchoconstriction/bronchospasm
3.) Coughing/bucking while on the ventilator
4.) Trendelenburg position
5.) Insufflation pressure from laparoscopic surgery
6.) Increased resistance through endotracheal tube
7.) Too high of tidal volume
8.) Too fast of a respiratory rate

58
Q

Positive end expiratory pressure (PEEP)

A

PEEP leaves a small amount of positive pressure in the lungs at the end of expiration which helps prevent atelectasis. Normal around 5cmH2O

59
Q

Continuous positive airway pressure (CPAP)

A

Leaves a small amount of positive pressure in the circuit at all time. (Constant PEEP)

60
Q

Common uses for CPAP

A

1.) Used in the recovery room for patients prone to sleep apnea
2.) Used at home for those with sleep apnea
3.) Preoxygenation in obese patients
4.) Intubated patients undergoing lung surgery

61
Q

I:E time

A

amount of time allowed for each inspiration and expiration in one breath. Normal ratio is 1:2

62
Q

Advantages of increasing inspiratory time (shortening expiratory time)

A

Lowers peak airway pressure

63
Q

Disadvantage of increasing inspiratory time

A

It shortens expiratory time which increases the risk of incomplete exhalation and can lead to overinflation of the lungs (auto PEEP or air trapping)

64
Q

COPD patients are prone to what

A

Air trapping because incomplete exhalation. Should consider longer expiration times

65
Q

Advantages of decreasing inspiratory time

A

expiratory time becomes longer which will allow for complete exhalation

66
Q

Disadvantage of decreasing inspiratory time

A

peak inspiratory pressure will increase

67
Q

Normal inspiratory time (Ti)

A

Adults: around 2 seconds if RR is within normal limits
Younger patients: 0.3-0.5 seconds in neonates

68
Q

Volume control ventilation

A

You set the tidal volume and it will deliver that no matter what pressure it takes. You can also set a limit for Pmax as a safety measure

69
Q

Problems with volume control ventilation

A

1.) you can create high peak inspiratory pressures
2.) accidentally overinflate a smaller patients lungs if you forget to turn the tidal volume down

70
Q

Pressure control ventilation

A

Set the amount of positive pressure they want to be generated with each breath. How much air that is delivered depends on how much volume the lungs can handle before that pressure is achieved. Advantage is that the lungs should never be overinflated

71
Q

Problems with pressure control ventilation

A

1.) We do not know initially what tidal volume the ventilator will give
2.) The tidal volumes can change when things in surgery change (going from prone to trendelenberg)

72
Q

Volume Control Autoflow

A

Upgraded version of volume control ventilation. It is able to deliver breaths with lower peak airway pressure. It is less likely to cause coughing on spontaneously ventilating patients.

73
Q

Techniques for reducing Inspiratory pressure

A

1.) Ensure that the patient is paralyzed or deeply anesthetized
2.) Intubate with larger diameter ETT
3.) use pressure control ventilation
4.) increase inspiratory time
5.) decrease respiratory rate and/or tidal volume
6.) cut the length of the ETT
7.) ask the surgeon to decrease the insufflation pressure or decrease the amount of trendelenberg