O2 Therapy & Vent Settings Flashcards
(159 cards)
1
Q
What is the formula for oxygen delivery?
A
DO2 = CO x Arterial O2 content
2
Q
What two factors make up a persons CO?
A
HR x SV
3
Q
What is the equation for arterial O2 content?
A
Hb x SaO2 x 1.34 + PaO2 x 0.003
4
Q
What is usually the first step in restoration of CO?
A
Restoration of intravascular volume guided by hemodynamic responses
5
Q
What is the triad of responses that can occur if we do not restore O2 delivery in patients?
A
Hypotension
Acidosis
Coagulopathy
6
Q
What is the most sensitive indicator of inadequate perfusion?
A
Lactate because you are assessing the product of anaerobic metabolism
7
Q
Why might you see a base deficit on an ABG?
A
Assume lactic acidosis which is mostly from blood loss or inadequate volume resuscitation
8
Q
How do you calculate oxygen use?
A
VO2 = CO x O2a - O2v
9
Q
What is the normal O2 extraction ratio?
A
About 25%, this is 4x the amount of O2 delivered
10
Q
When does a patient usually become symptomatic from inadequate perfusion?
A
When the reserve is lost, remember we only use about 25%
11
Q
What organ requires the most perfusion?
A
The heart
12
Q
Differentiate between hypoxia and hypoxemia?
A
Hypoxemia is a decrease in oxygen content in the blood where Hypoxia is a decrease in oxygen delivered to the tissues
13
Q
What is our goal as the anesthetic providers in oxygen delivery?
A
To maintain adequate oxygenation and ventilation
14
Q
What is the primary goal of O2 therapy?
A
Prevention and correction of hypoxemia and tissue hypoxia
15
Q
Differentiate between oxygenation and ventilation?
A
Oxygenation is delivery of O2 to the tissuesVentilation is removal of byproducts CO2 from the tissues
16
Q
What are the five types of hypoxia?
A
Hypoxic Circulatory Hemic Demand Histotoxic
17
Q
What type of hypoxia can occur with seizures, MH, sepsis or a fever?
A
Demand hypoxia because there is an increase in oxygen consumption
18
Q
What type of hypoxia can occur with congestive heart failure, MI or dehydration?
A
Circulatory hypoxia because there is a reduction in the cardiac output
19
Q
What are some global symptoms of hypoxia?
A
Vasodilation, tachycardia, tachypnea, cyanosis, confusion, lactic acidosis and organ-related changes
20
Q
What type of hypoxia can occur with over use of sodium nitroprusside?
A
Histotoxic hypoxia, cyanide toxicity can result from SNP at the mitochondrial level
21
Q
As the anesthetist, what are the two main symptoms of hypoxia are we most likely to see?
A
Lactic acidosis and organ related changes, the meds we give can mask some of the other symptoms described
22
Q
What type of hypoxia can be see with anemia and CO poisoning?
A
Hemic hypoxia from reduced hemoglobin content and function
23
Q
What type of hypoxia can be seen with drug overdose, altitude changes, asthma and congenital heart diseases?
A
Hypoxic hypoxia because of multiple factors such as:R–> L shuntVQ mismatch Pulmonary diffusion deficitAlveolar hypoventilationDecreased barometric FIO2
24
Q
What are four types of supplemental ambient O2 devices for non-intubated patients?
A
Nasal cannula
Simple face mask
Face mask with reservoir
Venturi mask
25
What flow rates can be used with a nasal cannula and how much does it increase the FiO2?
Flow Rates: 1-6L and with each increase in L the FiO2 increases about 4%
26
What is the minimum amount of O2 that can be set on a simple face mask and why?
5L, it is the amount of flow necessary to avoid CO2 rebreathing
27
How much FiO2 does a simple face mask typically deliver?
40-60%
28
How much FiO2 is delivered with a face mask reservoir bag?
60-100%
29
What type of patient is the venturi mask most beneficial in and why?
Patients with COPD, more precise FiO2 can be delivered (24-50%)
30
Define the venturi effect.
When diameter decreases velocity increases creating a negative pressure to "suck in" a second gas(Extension of Bernoulli's principle)
31
What is the FiO2 delivered with 2L NC?
0.23-0.28
32
What is the FiO2 delivered with 3L NC?
0.27-0.34
33
What is the FiO2 delivered with 4L NC?
0.31-0.38
34
What is the FiO2 delivered with 5-6L NC?
0.32-0.44
35
What is the FiO2 delivered with 5-6L on a simple face mask?
0.3-0.45
36
What is the FiO2 delivered with 7-8L on a simple face mask?
0.4-0.6
37
What is the FiO2 of a non-rebreating mask at 7-15L?
0.4-1.0
38
What are the five major hazards of O2 therapy?
```
Oxygen toxicity
Absorption atelectasis
Induced hypoventilation
Fire hazard
Retinopathy of prematurity
```
39
What can occur if high FiO2 is delivered over long periods of time?
Oxygen toxicity
40
What are some of the consequences of oxygen toxicity in the lung tissues?
Acute tracheobronchitis
Decreased ciliary movement (impaired ability to clear secretions)
Alveolar epithelial damage
Interstitial fibrosis
41
What are the two determinants of oxygen toxicity?
Partial pressure of O2 in inspired gases and duration of exposure
42
What are safe and toxic doses of O2 to an adult patient?
Safe: 100% O2 for up to 10-20h
Toxic: 50-60% for >24-72h
43
Who are considered a high risk population for oxygen toxicity?
>70yrs of age
Hx of radiation to lung or chest
Antineoplastic drugs: Bleomycin
44
How does oxygen toxicity occur?
Intracellular generation of O2 metabolites are cytotoxic as they react with cellular DNA Inflammation in alveoli leads to membrane disruption (compromises diffusion)
45
What are the signs and symptoms of oxygen toxicity?
Cough, dyspnea, rales, hypoxemia, decreased diffusion capacity, pulmonary fibrosis and increased A:a gradient
46
How does absorption atelectasis occur?
Insoluble nitrogen is replaced by O2 this causes a decreased alveolar volume because O2 is absorbed
47
What is a consequence of absorption atelectasis?
Causes an increase in pulmonary shunting from atelectasis
48
What is considered a safe level of O2 administration in order to avoid absorption atelectasis?
FiO2 of 60% is safe
49
What lung region is more at risk for the consequences of absorption atelectasis?
The dependent lung because of under-ventilation
50
How might induced hypoventilation occur from O2 administration?
With chronic CO2 retainers they rely on hypoxic drive to breathe, take away the hypoxia and the patient may hypovetilate or become apnic
51
In addition to over administration of O2, how else might an anesthetic provider induce hypoventilation?
Narcotic induced
52
What mechanism in the body is triggered when hypoxemia is sensed?
Peripheral chemoreceptors
53
How does O2 administration create a fire hazard?
O2 supports combustion
54
How does oxygen affect the premature retina?
Disorganized vascular proliferationFibrosisRetinal detachment Blindness secondary to retinal hyperoxia
55
What risk factors are associated with retinopathy from O2 administration?
less than 36weeks gestation
less than 1500g
Considered up to 44 weeks high risk
56
What is the safe O2 administration for a neonate?
PaO2 60-80mmHg
57
What is considered hypercapnia?
CO2 > 45mmHg
58
What are the two main causes of hypercapnia?
Increased alveolar dead space and decreased alveolar ventilation
59
What factors can cause an increase in alveolar dead space?
Failed alveolar perfusion
Interruptions of pulmonary circulation
Pulmonary disease
60
What is the most common cause of hypercapnia in the immediate post operative period?
Decreased alveolar ventilation from narcotics, decreased RR and TV
61
What is the major clinical manifestations of hypercapnia in the anesthetized?
Vasodilation of peripheral vessels --> increased HR
62
What clinical manifestations might be seen in an awake, hypercapnic post operative patient?
```
HA
N/V
sweating & flushing
Shivering
Restlessness
```
63
What is an important CNS consideration with hypercapnia?
Potent stimulus for cerebral vasodilation
64
How much does CBF increase with a 1mmHg increase in PaCO2?
1-2ml/100gm/min
65
How much can hypercapnia affect pulmonary artery pressure?
May produce a 60% increase in PAP
66
What way does the oxyhemoglobin dissociation curve shift with hypercapnia?
Rightward shift
67
What are the goals of mechanical ventilation?
Maintain adequate gas exchange
Minimize hemodynamic impairment
Avoid lung injury
Avoid injury to distant organs
68
What currently drives our gas machines?
Piston driven
69
What type of ventilation is delivered via an iron lung?
Negative pressure ventilation
70
What type of ventilation is being used if a square waveform is seen on the monitor?
Volume control
71
What type of ventilation is being used if a slanted waveform is seen on the monitor?
Pressure control
72
What does the distending pressure measure?
Compliance of the lungs
73
What does the resistive pressure measure?
Airway resistance
74
What is the pressure in the airway as a product of airway resistance
Peak inspiratory pressure (PIP), also known as the opening pressure
75
What is the pressure needed to distend the lung as a product of lung compliance?
Plateau pressure, needed to keep the airways open
76
Why might there not be a drop in the pressure wave form after initial opening pressure have been met?
If the lungs have poor compliance
77
If the baseline of the pressure curves are elevated what is expected?
The use of peep
78
What are mechanical ventilation variables?
Elements of a breath that a ventilator can control during delivery of the breath
79
What are the two kinds of variables in mechanical ventilation?
Control variables
| Phase variables
80
What type of variable does the ventilator control circuit manipulate to cause inspiration?
Control variable
81
What are the three types of control variables?
Volume
Pressure
Flow
82
How are ventilators classified?
Based on the control variable
83
Which variable is used to control the shape of the delivered breath?
Control variable
84
What variable varies in volume control ventilation?
Pressure
85
What variables vary in pressure control ventilation?
Volume and flow
86
What are the four phases of one respiratory cycle?
Start of inspirationInspiration itself
End of inspiration
Expiration
87
What controls the conventional phases of the respiratory cycle?
Phase variables
88
What are the four phase variables?
Trigger
Limit (target)
Cycle
Baseline
89
What is the relationship between the trigger variable and the respiratory cycle?
Starts inspiration
90
What is the relationship between the Limit variable and the respiratory cycle?
Limit reached and maintained at preset level before inspiration ends
91
What is the relationship between the cycling variable and the respiratory cycle?
End of inspiration beginning of expiration
92
What is the relationship between the baseline variable and the respiratory cycle?
Baseline conditions controlled at end expiration
93
What trigger is independent of the patient effort?
Time
94
What three triggers are sensed by the ventilator and delivers a breath in response to it?
Pressure
Flow
Volume
As a result of the patient attempting to inhale
95
What are the three limit (target) variables that cannot be exceeded during inspiration?
PressureVolumeFlow
96
What is the primary phase variable controlled by the ventilator during inspiration?
Limit (target) Variable
97
What phase variable is used to cycle from inspiration to expiration?
Cycling Variable
98
What are the four variables to cycle from inspiration to expiration?
Volume
FlowPressure
Time
99
How is the flow cycling variable measured?
Flow during inspiration falls to a certain level, typically 25% of the peak inspiratory flow
100
If an inspiratory pause has been set how is the ventilatory cycle changed?
Expiration does not immediately follow the delivery of a breath and now becomes time cycled
101
What is the most common baseline variable?
Pressure, controlled at end exhalation
102
How is pressure at the end of exhalation achieved?
Closure of the expiratory valve before the lung has completely emptied
103
What two components make up the baseline variables?
ZEEP, zero relative to atmospheric pressurePEEP positive related to atmospheric pressure
104
What components determine the ventilator mode?
How a breath is initiated, how a breath is delivered, and how it is terminated
105
In a volume controlled ventilator setting, what does adjusting the tidal volume result in?
Reduced atelectasis
106
In a volume controlled ventilator setting, what does adjusting the respiratory rate result in?
Maintenance of desired PaCO2
107
What are two determining factors f airway pressure?
Respiratory system resistance Compliance
108
How does Volume Controlled Ventilation function?
There is a set tidal volume delivered at a constant flow rate and set respiratory rate
109
What is the trigger, limit, cycle and baseline of VCV mode?
Trigger: Time
Limit: Flow
Cycle: Volume
Baseline: PEEP if desired
110
When is inspiration terminated in VCV?
When a set tidal volume is delivered, regardless of the pressure achieved
111
What is a typical tidal volume to deliver to a patient?
6-12mL/kg
112
What is a typical I:E ratio?
1:2
113
If PEEP is added to ventilator settings, what is a good number to start at and why?
5cmH2O, that is normal physiologic PEEP
114
How does Volume Assist Control Ventilation function?
There is a set TV and RR and the patient is able to trigger own breath that is supported by the set volume
115
What are the trigger, limit, cycle and baseline of ACV?
Trigger: Time OR pressure/flow (if pt spontaneously breathing)
Limit: Flow
Cycle: Volume
Baseline: PEEP if desired
116
What is a possible complication of ACV ventilation?
Muscle atrophy due to unloading of respiratory muscles
117
In ACV ventilation how could a patient determine their own RR?
As long as spontaneous RR EXCEEDS the ventilator set rate
118
If a patient becomes apnic on ACV, how does the ventilator respond?
Reverts to VCV delivering a set rate and tidal volume
119
How does Intermittent Mandatory Ventilation function?
There is a set TV and RR, the patient is able to breathe spontaneously between mandatory breaths but the spontaneous breaths are NOT supported
120
What is the trigger, limit, cycle and baseline of IMV?
Trigger: Time (because of mandatory breaths)
Limit: Flow
Cycle:Volume
Baseline: PEEP if desired
121
What is a major disadvantage to using the IMV mode?
Asynchrony that can lead to breath stacking
122
How does Synchronized Intermittent Mandatory Ventilation function?
A set TV and RR are delivered, minimum number of mandatory breaths are synchronized with the patient's respiratory effort and the breaths are NOT supported
123
What is the trigger, limit, cycle and baseline of SIMV?
Trigger: Time/Patient
Limit: Flow
Cycle: Volume
Baseline: PEEP if desired
124
What is the purpose of the SIMV mode?
To allow exercising of the respiratory muscles
125
What are the major benefits of using the SIMV mode?
Decreased occurrence of asynchrony and prevention of muscle atrophy
126
What is the function of SIMV + PSV?
A set TV and RR are delivered, minimum number of mandatory breaths are synchronized with the patient's respiratory effort and the breaths are supported by positive inspiratory pressure
127
What is the trigger, limit, cycle, baseline for SIMV+ PSV?
Trigger: Time/Patient
Limit: Flow/Pressure
Cycle:Volume/Flow
Baseline: PEEP if desired
128
Why might a provider choose pressure control over volume control ventilation?
Desire to limit inspiratory pressure
129
What type of patients are at risk for high PIP?
COPD
Neonates/infants
LMA
130
What type of patients are we concerned may have low compliance?
Pregnancy
Laparoscopic surgery
Morbid obesity
ALI/ARDS
131
What conditions might the provider choose to use pressure control ventilation versus volume control?
Concern for high PIP
Concern for low compliance
Compensation for leaks
132
What is the function of Pressure Control Ventilation?
There is a preset pressure limited breath is delivered as a set RR, supports apneic patients
133
What is the trigger, limit, cycle and baseline for PCV?
Trigger: Time
Limit: Pressure
Cycle: Time
Baseline: PEEP as desired
134
What determines the volume delivered in PCV?
Airway resistance and lung compliance
135
What is the benefit of a decelerating flow pattern?
Promotes more rapid alveolar filling and more even gas exchange
136
What is a typical pressure limit and recommended max when using PCV?
Initially start with 20cmH2O and recommended max 30-35 cmH2O
137
What is the function of Pressure Support Ventilation?
The patient must be spontaneously breathing, the patient sets the RR and additional support is given to achieve optimal consistent tidal volume (pt controls depth, length and flow of each breath)
138
How much PEEP is required to overcome the resistance of the ETT?
5 cmH2O
139
What is the trigger, limit and cycle of PSV?
Trigger: Patient (pressure or flow)
Limit: Pressure
Cycle: Flow
140
What can occur if a patient is given excessive levels of pressure support?
Respiratory alkalosis
Hyperinflation
Ineffective triggering
Apneic spells
141
What is a major set back to using PSV in patients with COPD?
Asynchrony
142
What is the function of PSV-Pro?
Spontaneous breathing mode, additional support to achieve optimal TV but there is a built in protection mode if the patient become apneic
143
What is the trigger, limit and cycle in PSV-Pro?
Trigger: Patient
Limit: Pressure
Cycle: Flow
144
What mode will PSV-Pro default to if apnea is detected?
Back up mode is usually PCV until patient begins breathing spontaneously again
145
If the trigger is too sensitive in PSV-Pro what can cause the ventilator to deliver a pressure support breath?
Surgical manipulation
Cardiogenic oscillations
Condensation in the breathing circuit
146
What can occur if the trigger is not sensitive enough in PSV-Pro?
The machine will fail to trigger and WOB will increase and may produce coughing and bucking
147
What are the two type of PEEP?
Intrinsic "auto PEEP"Extrinsic "applied PEEP"
148
What are the goals of adding PEEP?
Improved oxygenation and Re-expansion of collapsed alveoli
149
What type of patients may require Supra-physiologic PEEP?
ARDA/ALIPulmonary Edema
150
What are the physiologic effects to adding PEEP?
Decreased venous return
Increased ICP
Altered renal function
Barotrauma
151
The incomplete expiration prior to the initiation of the next breath causes progressive air trapping?
Auto-PEEP
152
What are some causes of intrinsic PEEP?
High minute ventilation
Expiratory flow limitation
Expiratory resistance
153
How do dual modes of ventilation function?
The inspiratory pressure is continuously adjusted to insure delivery of the set tidal volume using the lowest possible pressure
154
How does BiVent ventilation function?
There are two levels of CPAP, both levels allow the patient to breathe spontaneously
155
What are the two levels of Bivent set to treat?
Low level set to treat hypoxia
| High level set to assist in CO2 elimination
156
What is the formula to determine airway resistance?
Resistance = PIP - Pplat Inspiratory flow/min
157
How would you determine the flow rate being delivered to the patient?
60 sec/BPM = seconds per breathGiven volume and I:E ratio to calculate mL/secConvert to L/min
158
What is the formula to calculate lung compliance?
Compliance = Tidal Volume Pplat - PEEP
159
How would you calculate your I:E ratio?
60sec/BPM = seconds per breathGiven TV and flowConvert to mL/sec
