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Patient Monitoring and Instrumentation > Principles of Anesthesia Machine > Flashcards

Principles of Anesthesia Machine Flashcards

1
Q

What is blood pressure?

A

Pressure exerted on the interior walls of the blood vessels. Measures tissue perfusion in the anesthetized patient

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2
Q

Normal BP

A

120/80

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3
Q

Hypertensive

A

> 140/90

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4
Q

Hypotension

A

<90/60

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5
Q

What is the equation of MAP and what does this tell you about diastolic and systolic BP?

A

=[(2)(Diastolic BP) + Systolic BP]/3

- this equation tells us that diastolic BP has twice as much effect on MAP than systolic BP

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6
Q

What is the MAP of a patient with 120/80?

A

[(2)(80) + (120)] / 3

= 93.3

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7
Q

What is pulse pressure?

A

systolic pressure minus diastolic pressure (normally 30-40 mmHg)

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8
Q

Pulse pressure for 120/80?

A

40 mmHg

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9
Q

What is narrow pulse pressure?

A

when pulse pressure is <25% of the systolic pressure.

- Patient with 100/80. pp = 20 which is less than 25% of the systolic pressure.

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10
Q

At what point will a patient automatically have narrow pulse pressure?

A

when diastolic pressure is 75 mmHg or greater

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11
Q

What is wide pulse pressure?

A

When the pulse pressure is >50% of the systolic pressure.

- Patient has BP 170/80. Any diastolic prssure less than 85 mmHg would constitute wide pp

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12
Q

Overtime, what can happen to someone with hypertension? (3)

A
  1. Left ventricle will enlarge due to resistance
  2. possible myocardial ischemia
  3. possible stroke
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13
Q

What is hypotension?

A

low perfusion to the tissue organs

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14
Q

What factors affect BP? (3)

A
  1. Blood volume
  2. Vascular tone
  3. Medications
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15
Q

What is a normal HR?

A

60-100

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16
Q

What is tachycardia?

A

> 100

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17
Q

What is bradycardia?

A

<60

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18
Q

What does a pulse oximeter read and what is it?

A

SpO2 which is the percentage of hemoglobin that is saturated with O2 (93-98%)

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19
Q

Normal End Tidal CO2 (EtCO2)

A

35-45 mmHg

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20
Q

What does capnograph read?

A

EtCO2 and respiratory rate

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21
Q

Normal RR

A

12-20 (spontaneously breathing)

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22
Q

RR on ventilator

A

8-12

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23
Q

What is the purpose of the anesthesia machine?

A
  1. allows an anesthetist to ventilate a patient with positive pressure
  2. Allows an anesthetist to deliver anesthetic gases to keep patient asleep
24
Q

How many types of gases are there in anesthesia?

A

2, volatile agents (sevoflurane, Isoflurane, Desflurane) and fresh gases (O2, N2O, and air)

25
Q

How many different gases can be delivered to a patient? (not all at the same time)

A

6

26
Q

What part of the machine converts volatile agents into vapor?

A

Vaporizer

27
Q

What is the purpose of “fresh gas flow”?

A

fresh gas flow gases carry volatile agent to the patient

28
Q

Why use O2 to carry volatile agent?

A
  1. FiO2 compensates for atelectasis
  2. Patient may need higher FiO2 in order to have adequate O2 saturation
  3. Higher FiO2 allows patient to maintain O2 saturation for longer periods of time
29
Q

Why use N2O to carry volatile agent?

A
  1. only anesthetic gas that has analgesic properties

2. can use lower amounts of volatile agents

30
Q

Why use air to carry volatile agent?

A
  1. Can lower FiO2 if O2 is being given for too long (toxic)
  2. High FiO2 can cause absorption atelectasis
  3. FiO2 above 30% can cause airway fire
31
Q

Is O2 upstream or downstream to N2O? Why?

A

Downstream in case there is a leak, the FiO2 will still be 25% entering the body.

32
Q

What two ways can O2 be delivered to the machine?

A

Wall supply and E cylinder supply.

33
Q

What color are the respected gases on the wall supply?

A 
O2 = green
N2O = blue hose
air = yellow
scavenging = purple
34
Q

PSI changes as O2 flows to the patient…

A

2000 (H cylinders) –> 50 (O2 wall supply)–> 16 (anesthesia machine)

35
Q

What are the E cylinders?

A

emergency back up tanks for O2 when the wall supply is not available

36
Q

How many regulators does O2 go through to get to 16 psi? What about N2O?

A

2, 1

37
Q

Low pressure pathway..(10)

A
  1. Flowmeters
  2. Common Manifold
  3. Vaporizers
  4. Fresh (common) gas outlet
  5. Inspiratory Tubing 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
38
Q

What is useful about a scavenging system?

A
  1. Takes away excess gas form circuit

2. Prevents excess pressure buildup in circuit (10-15 L/min)

39
Q

What controls the amount of gas that goes through the scavenging system?

A

APL valve

40
Q

When would we want pressure in the circuit?

A

When anesthetics make the patients stop breathing and you need positive pressure to ventilate

41
Q

What two options do you have for applying positive pressure ventilation?

A
  1. squeeze the bag

2. turn the ventilator on

42
Q

When is it necessary to fully close the APL valve?

A

When it is difficult to get a good seal around the mask when masking a patient. (Fat santa most difficult)

43
Q

What must it mean if the APL valve is completely open?

A

Patient must be breathing spontaneously (on their own)

44
Q

How could you have the APL valve fully closed and still no pressure in the circuit?

A
  1. Loose mask seal
  2. Circuit disconnected from machine or ETT
  3. Deflated ETT cuff
  4. Leak inside the machine
45
Q

High Pressure Pathways of O2

A

completely bypasses the flowmeters in order to power the ventilator and oxygen flush valve.

46
Q

What is so special about the oxygen flush valve?

A

The high pressure gas is sent directly to the ventilator bellows and initiates positive pressure when patient ready for a breath and also supplies the circuit with positive pressure so anesthetist can ventilate the patient.

47
Q

If the APL valve is open, what will the pressure gauge read?

A

zero

48
Q

What are the guidelines for delivering positive pressure ventilation?

A
  1. Do not exceed 20 cm/H2O when venting via mask or LMA (air could enter stomach)
  2. Do not exceed 40 cm/H2O when ventilating via ETT (barotrauma of the lungs can occur)
49
Q

What will a pressure gauge read if the patient is under spontaneous ventilation?

A

Zero

50
Q

4 ways to get pressure in the circuit

A
  1. Turn on the fresh gas flow
  2. Close the APL valve
  3. Press the O2 flush button
  4. Avoid a leak in the circuit
51
Q

Is the ventilator part of the circuit in bag mode?

A

No

52
Q

Ventilation Options w/ Bag mode (3)

A
  1. Spontaneous ventilation
  2. Control/Mechanical ventilation (positive pressure ventilation) APL valve partially closed, breathing bag inflates, is squeezed and lungs expand
  3. Assist Ventilation: as the patient begins to inhale, anesthetist squeezes bag and delivers a larger tidal volume than the patient would have taken on their own
53
Q

How can you make ventilator mode more tolerable for the patient?

A
  1. Administer muscle relaxants (longer term therapy)
  2. Give higher dose of narcotics (longer term therapy)
  3. Give propofol (shorter term therapy)
54
Q

Should you turn on vent mode if a patient is in spontaneous ventilation?

A

No, this counteracts the natural breath of the patient

55
Q

What is significant about the Thorpe Tube?

A

It is narrower at the bottom than at the top. This ensures that more air is required to keep the bobbin afloat as it rises

56
Q

Why does O2 need to be downstream from N2O?

A

To prevent a hypoxic mixture of fresh gas flow being delivered to the patient and keep FiO2 at 25% in case of leak in the system.

Patient Monitoring and Instrumentation (2 decks)

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