Ventilation Modes & Oxygen Therapy Flashcards
(112 cards)
1
Q
What are the 3 controlled mechanical ventilation modes/
A
- Volume Controlled Ventilation (VCV)
- Pressure Controlled Ventilation (PCV)
- Pressure Controlled-Volume Guaranteed Ventilation (PCV-VG)
2
Q
What are 2 other methods of ventilation in addition to controlled ventilation modes?
A
- synchronized intermittent mandatory ventilation (SIMV)
2. Pressure Support Ventilation (PSV)
3
Q
Looking at the flow tracing, how do you know what mode the ventilator is set at?
A
Volume control will have “square” shape
Pressure control will have decelerating flow shape
4
Q
What is the resistive pressure?
A
overall pressure required to distend the lungs and airways
5
Q
What is the distending pressure?
A
pressure needed to open lungs to provide O2 delivery and CO2 removal
6
Q
What is the Peak Inspiratory Pressure tell providers about?
A
both intrinsic & extrinsic (chest wall & muscle) compliancec
7
Q
What does the Plateau Pressure (pplat) tell us about?
A
the intrinsic compliance of the lung
8
Q
What is the total pressure required to distend the lungs & airways?
A
the peak inspiratory pressure
9
Q
What is the distending pressure required to expand the lungs?
A
Plateau Pressure
10
Q
What pressure is used to calculate dynamic compliance?
A
Peak inspiratory pressure
11
Q
What pressure is used to calculate static compliance?
A
Plateau Pressure (pplat)
12
Q
How is a plateau pressure obtained?
A
must be in volume control with an inspiratory hold
13
Q
What compliance does dynamic compliance tell you about?
A
total respiratory compliance
14
Q
What compliance does static compliance tell you about?
A
intrinsic/lungs themselves compliance
15
Q
During a plateau pressure, what does the drop in pressure indicate?
A
redistribution of gas flow throughout the lungs
16
Q
What are the 4 variables that can be controlled during mechanical ventilation?
A
- respiratory rate
- tidal volume
- pressure (PiP / Pplat / PAW
- I:E ratio
17
Q
What can happen if you increase only the RR in a pressure mode?
A
decreased tidal volume = decreased minute ventilation d/t shortening of insp / exp time
18
Q
Each breath has 4 parts which are?
A
- start of inspiration
- inspiration itself
- end of inspiration
- expiration
19
Q
What is the trigger variable? and what are the 4 types?
A
represents the start of inspiration
- pressure
- volume
- flow
- time
20
Q
What is the limit variable?
A
maintenance of inspiration
aka: target variable
21
Q
What is the target variable?
A
maintenance of inspiration
aka limit variable
22
Q
What is the cycling variable?
A
transition of expiration
23
Q
What is the baseline variable?
A
end of expiration
aka PEEP
24
Q
The pressure trigger variable:
A
decrease in circuit pressure stimulates ventilator to deliver a breath
25
The volume trigger variable:
volume change in the circuit can stimulate the ventilator to deliver a breath
26
The flow trigger variable:
change of the flow in the circuit stimulates the ventilator to deliver a breath
27
The time trigger variable:
a set time interval triggers the ventilator to deliver a breath
28
What variable are we most concerned about?
the TRIGGER variable
29
What does the limit variable control?
how the inspiratory breath is maintained.
once the threshold is reached, the variable will not exceed a set limit
**does not cause termination of inspiration
30
Limit variable set as pressure sets what?
the upper pressure limit that cannot be exceeded
31
What can initiate the pressure trigger?
patient
or
an outside source (ie. surgeon pulling/pushing on patient)
32
What is tidal volume commonly set to?
8-12mL/kg
can be as low as 6mL/kg
[prevent overdistention and injury]
33
What is the respiratory rate commonly set to?
10-20 bpm
34
What is minute ventilation? (VE)
the average volume of gas entering or leaving the lungs per minute.
Usually L/min
Vt x RR = VE
normal 5-10L/min
35
What is normal VE?
5-10L/min
36
What is peak flow rate?
aka
peak inspiratory flow
highest flow, or speed, that is set to deliver the Vt during inspiration, usually L/min
the higher the flow rate, the faster the air is delivered and SLOWER the inspiratory time is
37
What is inspiratory:expiratory time?
| I:E ratio?
speed at which the Vt is delivered. Setting a shorter inspiratory time results in faster inspiratory flow
average adult inspiratory time 0.7 - 1
I:E ratio is usually 1:2 or 1:3
38
What is a normal I:E ratio?
1:2 or 1:3
39
What is the peak airway pressure?
| Paw
represents the total pressure that is required to deliver the Vt and depends upon various airway resistance, lung compliance, and chest wall factors.
expressed in cmH2O
40
What is the plateau pressure?
pressure that is needed to distend the lunch, which an be measured by applying an end-expiratory pause setting on the ventilator.
expressed in cmH2O
41
What is the sensitity or trigger sensitivity?
negative pressure [effort] required to trigger a machine breath, commonly set to -1 or -2 cm H2O [minimal] effort is needed.
some vents have flow triggering which is more sensitive.
42
What is PEEP?
the amount of positive pressure that is maintained at end-expiration.
cmH2O
43
What is the purpose of PEEP?
to increase end-expiratory lung volume and reduce air-space closure at end expiration
44
What is CPAP?
continuous pressurization of the breathing circuit when a patient breathes spontaneously. CPAP may be used as a last step in the weaning process or as a non-invasive method of providing a pneumatic splint to the upper airway in obstructive sleep apnea
45
What is a mandatory breath?
breath in which the timing and/or size of the breath is controlled by the ventilator; the machine triggers and/or cycles the breath
46
What is a spontaneous breath?
breath in which both the timing and size are controlled by the patient; the patient both triggers and cycles the breath
47
What are 4 volume-targeted ventilator modes
CMV
VCV
A/C
SIMV
48
What are 2 pressure-targeted ventilator modes?
PSV
| PCV
49
When does inspiration terminate in a volume targeted ventilator mode?
when a preset Vt has been delivered
50
When does inspiration terminate in a pressure targeted ventilator mode?
when a preset pressure is reached.
preset pressure delivered; volume is variable and determined by set pressure level, airway resistance, and lung compliance factors, specified time or flow cycling criteria
51
In a pressure targeted mode, is the inspiratory flow rate fixed or variable?
variable.
52
What happens if a patient inspires faster or more vigorously when on a pressure targeted mode?
the flow rate may need to be changed
53
Is the inspiratory flow rate fixed or variable in a volume targeted mode?
fixed.
54
What happens if a patient inspires faster or more vigorously when on a volume targeted mode?
WOB will increase, flow rate or other settings need to be changed
55
What is the abbreviation for oxygen delivery?
DO2
56
What is the oxygen delivery equation?
DO2 = CO x arterial O2 content
57
What is one value (from a blood gas) that can indicate an O2 delivery issue?
the base deficit
58
What is VO2?
oxygen use
59
What is the equation for VO2?
CO x O2a - O2v
60
What is a normal oxygen extraction ratio?
25%
61
What is special about oxygen extraction of the heart?
the heart has a very high oxygen demand
62
What is hypoxemia?
deficiency of O2 in the blood
63
What is hypoxia?
O2 delivery to the tissues is not adequate to meet metabolic demand
64
What is anesthesia's goal in oxygen therapy?
maintain oxygenation and ventilation
65
What is the goal of oxygen therapy?
prevention and correction of hypoxemia and tissue hypoxia
66
What are the 5 types of hypoxia?
1. hypoxic
2. circulatory
3. Hemic
4. Demand
5. Histotoxic
67
What is hypoxic hypoxia?
shunt of pulmonary diffusion defect;
- drug overdose causing hypoventilation
- COPD
asthma
emphysema
- atlectasis
68
What is circulatory hypoxia?
↓ CO d/t MI, congestive HF
69
What is hemic hypoxia?
↓Hgb or fxn of Hgb
70
What is demand hypoxia?
↑O2 consumption (fever, Sz, MH)
71
What is histotoxic hypoxia?
inability of cells to USE oxygen (cyanide toxicity)
72
What are 6 s/s of hypoxia?
1. vasodilation
2. tachycardia
3. tachypnea
4. cyanosis
5. confusion
6. lactic acidosis
73
What is the treatment of hypoxia in mechanically ventilated patients?
tailored to treat the cause
74
What are 6 possible methods of increasing oxygenation in a ventilated patient?
1 . increase VE (minute ventilation)
2. Increase CO
3. Increase O2 carrying capacity
4. Optimize V/O relationship (↓PEEP)
5. Decrease O2 consumption
6. increase FiO2
75
What are 4 methods of oxygen delivery in non-ventilated patients
1. nasal cannula
2. simple face mask
3. face mask with reservoir
4. venturi mask
76
What is the flow rate/ % O2 delivery of a nasal cannula?
1-6L/min
4% per L
77
What is the flow rate/ % O2 delivery of a simple face mask?
minimum flow of 6L to prevent rebreathing
40-60%
→ must provide at least the minute ventilation in flow to prevent rebreathing
78
What is the FiO2 delivery of a face mask with a reservoir?
60-100%
79
What is the FiO2 delivery of a venturi mask?
24-50% (more precise)
check set up for correct flow rate
80
What principle does a venturi face mask use?
Bernoulli principle
81
What are 3 sequalae of high FiO2 on lung tissue?
1. decreased ciliary movement = lungs can't mobilize mucous
2. alveolar epithelial damage
3. interstitial fibrosis
82
Damage to lung tissue from high FiO2 is dependent upon what 3 factors?
1. FiO2
2. duration of therapy
3. patient susceptibility
83
Delivery of 100% FiO2 is safe for how long?
10-20 hours
84
Delivery of 50-60% FiO2 is safe for how long?
24-72 hours
85
Toxicity of 50-60% FiO2 is seen after how long?
24-72 hours
86
What is absorption atelctasis?
nitrogen is replaced in the lung by oxygen.
alveoli become UNDER VENTILATED and have DECREASED VOLUME
increase pulmonary shunting (perfusion w/o ventilation)
WIDENING OF THE A-a gradient
87
At what FiO2 is absorption atelectasis likely to not occur?
60% FiO2
88
What is induced hypoventilation?
chronic CO2 retainers become hypercapnic
→ rely on hypoxemia for respiratory drive. (peripheral chemoreceptors are triggered by hypoxemia)
→ high amounts of delivered O2 can cause apnea
(theory)
89
What patients are at highest risk for oxygen toxicity? (3 patient populations)
1. elderly >70y
2. Hx radiation to the chest
3. Bleomycin [methotrexate]
90
What are 6 s/s of oxygen toxicity?
1. cough
2. rales
3. dyspnea
4. hypoxemia
5. ↑ A-a gradient
6. ↓ diffusion capacity
91
When are providers MOST concerned about intra-operative fire?
head and neck cases with high FiO2
** tracheostomy patients. already have induced atelectasis (likely) from long term mechanical ventilation and O2 requirement.
find balance communicating with surgeon about oxygenating... cautery... oxygenating... cautery
92
What should be considered when using cautery or lasers on the head or neck?
- use LOW FiO2.
- O2 can build up under drapes
- COMMUNICATE with the surgeon if FiO2 is needed
- it is possible to connect nasal cannula to common gas outlet and deliver <100% FiO2
93
What is retinopathy?
exponential growth of the retinal vasculature [scarring]
- vascular proliferation, fibrosis, retinal detachment, blindness
94
What 3 characteristics of patients are most at risk for retinopathy?
1. < 36 weeks gestation
2. weight < 1500g
3. up to 44 weeks gestation = high risk
95
What is considered "safe" O2 delivery for patients that are at high risk of developing retinopathy?
PaO2 60-80 mmHg
96
What is hypercapnia?
| What are the causes?
CO2 > 45mmHg
1. increased CO2 concentration (lack of removal)
2. increased CO2 production
97
What are 2 causes of hypercapnia in relation to V/Q mismatch?
1. increased alveolar dead space
| 2. decreased alveolar ventilation
98
How does increased alveolar dead space lead to hypercapnia?
decreased alveolar perfusion
interruptions in pulmonary circulation
pulmonary disease
99
What are the 2 types of defects that can cause decreased alveolar ventilation, leading to hypercapnia?
can be central or peripheral defect
** respiratory depression is the most common cause of hypercapnia in the postoperative period
100
What are 6 non-specific signs of hypercapnia?
headache, nausea/vomiting, sweating, flushing, shivering, restlessness
101
What are 3 manifestations of hypercapnia (not signs)?
1. vasodilation of peripheral vessels (direct)
2. increased HR from catecholamine release (indirect)
3. effects d/t an acidotic state
102
What are CNS considerations of hypercapnia?
1. regulation of ventilatory drive
2. cerebral blood flow (dilation of vessels)
↑CO2 = ↑RR
1mmHg increase in PaCO2 will increase cerebral blood flow by 1-2mL/100g/min
103
1mmHg increase in CO2 will increase cerebral blood flow by how much?
1-2mL/100g/min
104
What are cardiovascular considerations of hypercapnia?
1. depression of smooth muscle
2. depression of cardiac muscle
3. increased catecholamine release
4. vasodilation vs vasoconstriction
- VD initially then ↑SNS results in VC
105
What are pulmonary considerations of hypercapnia?
1. increased RR
2. increased pulmonary vascular resistance
*60% increase in pulmonary artery pressures
106
Hypercapnia will shift the oxyhemoglobin dissociation curve which way?
to the right
107
How is hypercapnia treated?
#1 treat cause
- increase minute ventilation
bad CO2 scrubber?
108
What is hypocapnia?
PaCO2 < 35mmHg
109
What is the most common cause of hypocapnia?
iatrogenic
110
What are the CNS manifestations of hypocapnia?
decreased CBF
| [can be beneficial with ↑ ICP or neurosurgery]
111
What are the cardiovascular manifestations of hypocapnia?
decrease in CO, coronary artery constriction
alkalosis can lead to ↓iCa
112
What are the pulmonary manifestations of hypocapnia?
hypoxemia may result from hypoventilation
