Anesthesia Machine Flashcards
(129 cards)
1
Q
Pressure exerted by blood against the interior walls of blood vessels
A
Blood pressure
2
Q
Why is blood pressure important?
A
It assesses tissue perfusion
3
Q
What are causes of hypotension?
A
Vasodilation, hypovolemia
4
Q
What is the equation for Mean Arterial Pressure (MAP)?
A
MAP = (2(diastolic)+systolic)/3
5
Q
What is a normal MAP?
A
70-100 mmHg
6
Q
What is the equation for pulse pressure?
A
Systolic-diastolic
7
Q
What is normal pulse pressure?
A
30-40 mmHg
8
Q
When pulse pressure is <25% of the systolic pressure
A
Narrow pulse pressure
9
Q
When pulse pressure is >50% of the systolic pressure
A
Wide pulse pressure
10
Q
What are consequences to hypertension?
A
- Added strain on the heart
- Increased oxygen demand on the heart
- Possible stroke
11
Q
What are consequences to hypotension?
A
Decreased tissue perfusion (possible stroke, MI, renal failure, etc)
12
Q
Normal Sinus Rhythm (NSR)
A
60-100 bpm
13
Q
Bradycardia
A
<60 bpm
14
Q
Tachycardia
A
> 100 bpm
15
Q
Normal SpO2
A
93-100% on room air
16
Q
Normal EtCO2
A
35-45 mmHg
17
Q
The amount of carbon dioxide in expired air
A
End tidal
18
Q
2 functions of the capnograph
A
- To show end tidal (EtCO2)
2. To show respiratory rate (RR)
19
Q
Normal respiratory rate for a spontaneously breathing patient
A
12-20 breaths per minute
20
Q
Normal RR for a patient on the ventilator
A
8-12 breaths per minute
21
Q
Normal core body temperature
A
36-38 C
22
Q
Normal room temperature
A
23 C
23
Q
What is the purpose for the anesthesia machine?
A
- To ventilate a patient with positive pressure ventilation
2. To deliver anesthetic gases to keep the patient asleep
24
Q
What are the two types of gases in anesthesia?
A
Volatile agents (Sevoflurane, Isoflurane, Desflurane) Fresh gas flow (nitrous oxide, oxygen, air)
25
What does the anesthesia circuit do?
It connects the machine to the patient so that anesthetic gases can be inhaled
26
What does the anesthesia machine do?
Delivers anesthetic gases to the patient
27
Where the gases of the machine travel through to get to the patient's airway
Inspiratory limb
28
Where the patient's exhaled gases travel back to the machine
Expiratory limb
29
Filters out bacteria and viruses, humidifies dry gases
Humidifier
30
Measures the patient's exhaled gases (oxygen, CO2, volatile agents)
Gas sampling line
31
Why is oxygen used to carry the volatile agent to the patient?
1. Higher FiO2 compensates for atelectasis
2. Some patients with lung disease may require higher FiO2 to have an adequate O2 level during anesthesia
3. Higher FiO2 allows patient to maintain adequate oxygen saturation for longer periods in the case of apnea at the end of surgery
32
Why is nitrous oxide used to carry the volatile agent to the patient?
1. It is the only anesthetic gas with analgesic properties
| 2. Allows lower concentrations of a volatile agent to be used
33
Why is air used to carry the volatile agent to the patient?
Allows for lower FiO2, which is good because:
1. Too much oxygen for too long can cause toxicity
2. Higher FiO2s can cause absorption atelectasis
3. FiO2 above 30% and/or use of nitrous oxide can increase risk for airway fires in the case of lasers or cautery in the pharynx/larynx
34
What are the two sources for fresh gas flow?
1. Wall supply
| 2. E cylinder (tank)
35
Where wall supply fresh gas flow starts
H cylinders under high pressure (2,000 psi for O2)
36
Pressure inside wall supply
50 psi (high pressure)
37
Pressure of flow inside the anesthesia machine
16 psi (low pressure)
38
Name of the knobs that turn on fresh gas flow gases
Rotameters or flow control valves
39
The portion of the anesthesia machine where fresh gas flow gases enter the pathway
Flowmeters
40
Flowmeters with a bobbin
Thorpe Tube Flowmeter
41
Why flowmeters are oriented with oxygen downstream
To prevent a hypoxic mixture from being delivered to the patient
42
The maximum nitrous oxide to oxygen ratio
3:1
43
The minimum oxygen concentration allowed with nitrous oxide
25%
44
Two index safety systems to prevent hooking up the wrong fresh gas flow
1. Diameter Index Safety System (DISS) -wall supply
| 2. Pin Index Safety System (PISS) -gas tank
45
10 parts to the Low Pressure Pathway
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 and APL valve
10. Exhaled gas joins fresh gas outlet
46
Reduces the pressure of gas from wall supply to 16 psi
2nd stage regulator
47
Controls the amount of pressure within a circuit by taking excess gas away from circuit and preventing excess pressure build up
Scavenging system
48
Controls the amount of gas going to scavanging
APL valve (Adjustable Pressure Limiting valve)
49
APL valve controls:
1. The amount of fresh gas flow that goes to scavenging
2. The amount of gas that a patient rebreathes
3. The amount of pressure in a circuit
50
APL is open
Increases the volume of gas that goes to scavenging and decreases the volume of gas and pressure that stays in the circuit
Makes it impossible to breathe for the patient because the bag won't inflate
51
APL is partially closed
Decreases the volume of gas that goes to scavenging and increases the volume of gas that stays in the circuit
Increase pressure in the circuit
Perfect for positive pressure ventilation
52
APL is fully closed
No gas can go to scavenging
Pt will rebreathe their exhaled gas
The volume and pressure of lungs and circuit will become dangerously high
53
What does pressing the Oxygen Flush Valve do?
Allows 50psi (high pressure) to enter the circuit at a rate of 35-75 L/min
54
Why use the oxygen flush valve?
If there was a leak in the circuit making it difficult to build up pressure within the circuit AFTER the APL valve is closed
55
What are examples of possible circuit leaks?
1. ETT cuff deflated
2. Loose mask seal
3. Cap off humidifier
4. Gas sampling line connections
5. Disconnected inspiratory or expiratory limbs
56
How can you increase circuit pressure?
1. Turn up the fresh gas flow
2. Close the APL valve
3. Press the oxygen flush button
4. Avoid a leak in the circuit
57
What are guidelines for circuit pressure?
When the APL valve is open, the pressure gauge reads 0 cmH2O
When the APL valve is closed, the pressure gauge shows an increase in pressure and reads higher when a positive pressure breath is delivered by bag or ventilation
58
What are the guidelines for delivering positive pressure ventilation?
1. Do not exceed 20cmH2O pressure when ventilating via mask or LMA -why? air could possibly enter the stomach at higher pressures
2. Do not exceed 40cmH2O pressure when ventilating via ETT -why? Barotrauma of the lungs can occur at high pressures
59
What is bag mode?
Manual/Spontaneous mode
The ventilator is not turned on and is not part of the circuit
When the pt inhales, the breathing bag deflates
When the pt exhales, the breathing bag expands
The breathing bag may be used to provide positive pressure breaths if needed
60
What is ventilator mode?
The ventilator will be delivering positive pressure breaths.
| On newer machines, both the ventilator and the breathing bag are part of this circuit
61
When would you use ventilator mode?
For prolonged cases where positive pressure ventilation is needed
62
When would you use bag mode?
1. For short term positive pressure ventilation for temporary apnea such as after induction/before intubation, failed intubation, oversedation, loss of airway after extubation or other unexpected apnea
2. When positive pressure ventilation is needed on a patient that is not intubated
3. Spontaneous ventilation
63
When is it okay to use the ventilator with mask ventilation?
If there is no provider in the room to squeeze the bag
64
How can you help a patient "tolerate" the ventilator?
Long term- administer muscle relaxants, give higher doses of narcotics
Short term- give propofol
65
Refers to a patient breathing on their own, rather than the anesthetist breathing for them
Spontaneous ventilation
66
Refers to an anesthetist squeezing the bag (delivering positive pressure) as the patient starts to inhale
Assist ventilation
67
Why would you use assist ventilation?
For patients that aren't taking deep enough breaths on their own and need assistance
68
How do you use assist ventilation?
Can use bag mode (manual/spontaneous) or Pressure Support
69
Refers to an anesthetist breathing for a patient with positive pressure ventilation
Control/Manual ventilation
70
What settings can you control on the machine?
1. Tidal volume (Vt)
2. Respiratory Rate (RR)
3. Peak Inspiratory Pressure (PIP)
4. Positive End Expiratory Pressure (PEEP)
5. Continuous Positive Airway Pressure (CPAP)
6. Inspiratory to Expiratory Ratio (I:E)
7. Inspiratory Time (Ti)
71
What is a normal tidal volume?
Traditionally, 5-10 ml/kg
| Recently, 6-8 ml/kg with higher RR
72
Describe the volume/pressure relationship in the lungs
The pressure inside the lungs is proportional to the volume delivered
The higher the tidal volume, the higher the inspiratory pressure
73
Slower respiratory rates lead to:
Longer breaths
Longer inspirations
Lower pressure
74
Faster respiratory rates lead to:
Shorter breaths
Shorter inspirations
Higher pressure
75
The maximum amount of pressure you are willing to give in order to expand the patient's lungs with a ventilator breath
Peak Inspiratory Pressure (PIP), or Pmax
76
Common causes of High Peak Inspiratory Pressure
1. R mainstem intubation
2. Bronchoconstriction/bronchospasm
3. Coughing/bucking on the ventilator
4. Trendelenburg
5. Insufflation pressure from laproscopic surgery
6. Increased resistance through the ETT
7. Too high of tidal volume
8. Too fast of respiratory rate/too short inspiratory time
77
The first sign of R mainstem intubation****
Elevated peak inspiratory pressure
78
Leaving a small amount of positive pressure in the lungs at the end of expiration
Positive End Expiratory Pressure (PEEP)
79
Purpose of PEEP
To prevent atelectasis
80
Normal amount of PEEP
5cmH2O
81
Leaving a small amount of positive pressure in the lungs at all times
Continuous Positive Airway Pressure (CPAP)
82
When would you use CPAP?
1. Preoxygenation in obese patients
2. Intubated patients undergoing lung surgery
3. Laryngospasms
4. In the recovery room for patients with sleep apnea
83
Normal I:E ratio
1:2 Expiratory time is 2x as long as inspiratory time
84
True/false: We can increase inspiratory time by decreased respiratory rate
True
85
What does increasing inspiratory time do?
Decreases peak inspiratory pressure
| Decreases expiratory time
86
What is a consequence to increasing inspiratory time?
Shorter expiratory time can cause incomplete exhalation, which can cause overinflation of the lungs (Auto PEEP)
87
How do you prevent Auto PEEP in COPD patients?
Increase expiratory time (1:2.5)
88
Normal inspiratory times?
Young patients: fast respiratory rates and low lung volumes require shorter inspiratory times (0.3-0.5 seconds in neonates)
Adult patients: slower respiratory rates and high lung volumes require longer inspiratory times (2 seconds)
89
Faster respiratory rate does what to inspiratory times and peak pressure?
Faster respiratory rate = shorter inspiratory times and higher peak pressure
90
What is volume control ventilation?
The ventilator will deliver the tidal volume you set regardless of the amount of pressure it takes
91
How do you prevent using too high of a pressure in volume control ventilation?
Set a limit for the amount of positive pressure the vent can generate
92
What are the consequences to volume control ventilation?
1. You can create high peak inspiratory pressures if airway resistance is increased or if there is increased resistance to diaphragm expansion
2. You can accidentally overinflate a small patient's lungs
93
What is pressure control ventilation?
You set the amount of positive pressure you want generated with each breath and the lungs will expand until that pressure is reached
94
What are advantages to pressure control ventilation?
1. The ventilator will never exceed that amount of positive pressure (pulmonary injury is less likely)
2. The lungs should never become overinflated (or receive too high of a tidal volume), because the breath will be delivered with an acceptable amount of pressure
95
What are consequences to pressure control ventilation?
1. You don't know what tidal volume the ventilator will give
| 2. Tidal volumes can change when things in surgery change (tidal volume will be lower with increased resistance)
96
In volume control ventilation, how will increasing the respiratory rate change the tidal volume and peak inspiratory pressure?
Tidal volume: No change
| PIP: Increase
97
In pressure control ventilation, how will increasing the respiratory rate change the tidal volume and peak inspiratory pressure?
Tidal volume: Decrease
| PIP: No change
98
In volume control ventilation, how will changing the I:E ratio from 1:2 to 1:3 change the tidal volume and peak inspiratory pressure?
Tidal volume: No change
| PIP: Increase
99
In pressure control ventilation, how will changing the I:E ratio from 1:2 to 1:1 change the tidal volume and peak inspiratory pressure?
Tidal volume: Increase
| PIP: No change
100
What patients are at risk for experiencing high peak inspiratory pressure?
1. Obese patients
2. Patients undergoing laproscopic surgery
3. Patients in Trendelenburg
101
What are techniques for reducing inspiratory pressure during positive pressure ventilation?
1. Ensure the patient is paralyzed or deeply anesthetized
2. Intubate with a larger diameter ETT
3. Place the patient in pressure control ventilation
4. Increase inspiratory time
5. Decrease the respiratory rate and/or tidal volume -will decrease minute ventilation and can cause SpO2 and EtCO2 to drop
6. Cut the length of the ETT
7. Ask the surgeon to decrease insufflation pressure/Trendelenburg
102
The ability of a container to expand when pressure is added to it
Compliance
103
True/false: Something with high compliance will expand more easily
True
104
What is the compliance equation?
pulmonary compliance = change in volume (ml) / change in pressure (cmH2O)
105
The ability of a container to return to it's original volume after the pressure inside the container is released
Elasticity
106
True/false: Things with low elasticity will deflate rapidly
False
107
True/false: Things with high compliance will have low elasticity
True
108
Why do COPD patients and smokers have compliant lungs?
The lungs can expand great, but are slow to deflate. It is difficult for them to exhale and air can get "trapped" in the alveoli
109
If a patient has a pulmonary compliance of 15 ml/cmH2O and they're being ventilated (positive pressure ventilation) with 30 cmH2O, what is their tidal volume?
15 ml/cmH2O = V/30cmH2O
| V= 450 ml
110
Forced exhalation against a closed glottis
Valsalva maneuver
111
The Valsalva maneuver results in:
1. Increased intrathoracic pressure
2. Decreased venous return (preload)
3. Decreased arterial blood pressure
112
Why would a patient "bear down" or "blow through a straw"?
To complete the Valsalva Maneuver as a vagal response for SVT
113
How does an anesthetist perform a Valsalva Maneuver?
1. Close the APL valve
2. Deliver positive pressure through the breathing bag
3. Hold for several seconds at 30-40 cmH2O
114
Indications for performing the Valsalva Maneuver
1. "Recruits" alveoli to treat atelectasis
2. Allows a surgeon to see an air leak after lung surgery
3. Allows a surgeon to check for a dura leak after neurosurgery
115
Measures the patient's exhaled tidal volumes
Spirometer
116
Analyzes which gases and what concentrations are being used
Spectrometer
117
Reveals the FiO2
Oxygen Analyzer
118
Prevents an accidental overdose of nitrous oxide if the O2 wall supply falls below 25 psi
Fail safe valve
119
Prevents positive pressure ventilation from being transmitted back to the vaporizers and flowmeters
Check valve
120
Used in MAC cases for supplemental oxygen
Auxiliary oxygen flowmeter
121
The most important thing to set up in the OR
Suction
122
Indicates the presence of a problem even though no problem exists
False positive result
123
Occurs when an alarm indicates there isn't a condition present when in reality, there is
False negative result
124
True/false: Alarms with high sensitivity will have a higher false positive rate
True
125
True/false: Alarms with high specificity has a lower false positive rate
True
126
When does the low pressure oxygen alarm go off?
When the wall supply pressure goes below 30 psi
127
When does the low inspired oxygen alarm go off?
When the FiO2 is low
128
When does the high circuit pressure go off?
When too much positive pressure is being delivered while ventilating the patient
129
When does the sustained airway pressure alarm go off?
When there is a continuous increase in circuit pressure
