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Principles of Monitoring & Fluid balance > Oxygen Therapy & Ventilator Paremeters > Flashcards

Oxygen Therapy & Ventilator Paremeters Flashcards

1
Q

What is the formula for oxygen delivery?

A

DO2 = CO x Arterial O2 content

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2
Q

What two factors make up a persons CO?

A

HR x SV

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3
Q

What is the equation for arterial O2 content?

A

Hb x SaO2 x 1.34 + PaO2 x 0.003

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4
Q

What is usually the first step in restoration of CO?

A

Restoration of intravascular volume guided by hemodynamic responses

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5
Q

What is the triad of responses that can occur if we do not restore O2 delivery in patients?

A

Hypotension
Acidosis
Coagulopathy

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6
Q

What is the most sensitive indicator of inadequate perfusion?

A

Lactate because you are assessing the product of anaerobic metabolism

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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

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8
Q

How do you calculate oxygen use?

A

VO2 = CO x O2a - O2v

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9
Q

What is the normal O2 extraction ratio?

A

About 25%, this is 4x the amount of O2 delivered

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10
Q

When does a patient usually become symptomatic from inadequate perfusion?

A

When the reserve is lost, remember we only use about 25%

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11
Q

What organ requires the most perfusion?

A

The heart

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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

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13
Q

What is our goal as the anesthetic providers in oxygen delivery?

A

To maintain adequate oxygenation and ventilation

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14
Q

What is the primary goal of O2 therapy?

A

Prevention and correction of hypoxemia and tissue hypoxia

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15
Q

Differentiate between oxygenation and ventilation?

A

Oxygenation is delivery of O2 to the tissues

Ventilation is removal of byproducts CO2 from the tissues

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16
Q

What are the five types of hypoxia?

A 
Hypoxic
Circulatory
Hemic
Demand
Histotoxic
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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

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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

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19
Q

What are some global symptoms of hypoxia?

A

Vasodilation, tachycardia, tachypnea, cyanosis, confusion, lactic acidosis and organ-related changes

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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

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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

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22
Q

What type of hypoxia can be see with anemia and CO poisoning?

A

Hemic hypoxia from reduced hemoglobin content and function

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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 shunt
VQ mismatch 
Pulmonary diffusion deficit
Alveolar hypoventilation
Decreased barometric FIO2
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24
Q

What are four types of supplemental ambient O2 devices for non-intubated patients?

A

Nasal cannula
Simple face mask
Fasce mask with reservoir
Venturi mask

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25
Q

What flow rates can be used with a nasal cannula and how much does it increase the FiO2?

A

Flow Rates: 1-6L and with each increase in L the FiO2 increases about 4%

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26
Q

What is the minimum amount of O2 that can be set on a simple face mask and why?

A

5L, it is the amount of flow necessary to avoid CO2 rebreathing

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27
Q

How much FiO2 does a simple face mask typically deliver?

A

40-60%

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28
Q

How much FiO2 is delivered with a face mask reservoir bag?

A

60-100%

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29
Q

What type of patient is the venturi mask most beneficial in and why?

A

Patients with COPD, more precise FiO2 can be delivered (24-50%)

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30
Q

Define the venturi effect.

A

When diameter decreases velocity increases creating a negative pressure to “suck in” a second gas
(Extension of Bernoulli’s principle)

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31
Q

What is the FiO2 delivered with 2L NC?

A

0.23-0.28

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32
Q

What is the FiO2 delivered with 3L NC?

A

0.27-0.34

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33
Q

What is the FiO2 delivered with 4L NC?

A

0.31-0.38

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34
Q

What is the FiO2 delivered with 5-6L NC?

A

0.32-0.44

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35
Q

What is the FiO2 delivered with 5-6L on a simple face mask?

A

0.3-0.45

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36
Q

What is the FiO2 delivered with 7-8L on a simple face mask?

A

0.4-0.6

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37
Q

What is the FiO2 of a non-rebreating mask at 7-15L?

A

0.4-1.0

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38
Q

What are the five major hazards of O2 therapy?

A 
Oxygen toxicity
Absorption atelectasis
Induced hypoventilation
Fire hazard
Retinopathy of prematurity
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39
Q

What can occur if high FiO2 is delivered over long periods of time?

A

Oxygen toxicity

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40
Q

What are some of the consequences of oxygen toxicity in the lung tissues?

A

Acute tracheobronchitis
Decreased ciliary movement (impaired ability to clear secretions)
Alveolar epithelial damage
Interstitial fibrosis

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41
Q

What are the two determinants of oxygen toxicity?

A

Partial pressure of O2 in inspired gases and duration of exposure

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42
Q

What are safe and toxic doses of O2 to an adult patient?

A

Safe: 100% O2 for up to 10-20h
Toxic: 50-60% for >24-72h

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43
Q

Who are considered a high risk population for oxygen toxicity?

A

> 70yrs of age
Hx of radiation to lung or chest
Antineoplastic drugs: Bleomycin

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44
Q

How does oxygen toxicity occur?

A

Intracellular generation of O2 metabolites are cytotoxic as they react with cellular DNA
Inflammation in alveoli leads to membrane disruption (compromises diffusion)

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45
Q

What are the signs and symptoms of oxygen toxicity?

A

Cough, dyspnea, rales, hypoxemia, decreased diffusion capacity, pulmonary fibrosis and increased A:a gradient

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46
Q

How does absorption atelectasis occur?

A

Insoluble nitrogen is replaced by O2 this causes a decreased alveolar volume because O2 is absorbed

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47
Q

What is a consequence of absorption atelectasis?

A

Causes an increase in pulmonary shunting from atelectasis

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48
Q

What is considered a safe level of O2 administration in order to avoid absorption atelectasis?

A

FiO2 of 60% is safe

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49
Q

What lung region is more at risk for the consequences of absorption atelectasis?

A

The dependent lung because of under-ventilation

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50
Q

How might induced hypoventilation occur from O2 administration?

A

With chronic CO2 retainers they rely on hypoxic drive to breathe, take away the hypoxia and the patient may hypovetilate or become apnic

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51
Q

In addition to over administration of O2, how else might an anesthetic provider induce hypoventilation?

A

Narcotic induced

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52
Q

What mechanism in the body is triggered when hypoxemia is sensed?

A

Peripheral chemoreceptors

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53
Q

How does O2 administration create a fire hazard?

A

O2 supports combustion

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54
Q

How does oxygen affect the premature retina?

A

Disorganized vascular proliferation
Fibrosis
Retinal detachment
Blindness secondary to retinal hyperoxia

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55
Q

What risk factors are associated with retinopathy from O2 administration?

A

< 36weeks gestation
<1500g
Considered up to 44 weeks high risk

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56
Q

What is the safe O2 administration for a neonate?

A

PaO2 60-80mmHg

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57
Q

What is considered hypercapnia?

A

CO2 > 45mmHg

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58
Q

What are the two main causes of hypercapnia?

A

Increased alveolar dead space and decreased alveolar ventilation

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59
Q

What factors can cause an increase in alveolar dead space?

A

Failed alveolar perfusion
Interruptions of pulmonary circulation
Pulmonary disease

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60
Q

What is the most common cause of hypercapnia in the immediate post operative period?

A

Decreased alveolar ventilation from narcotics, decreased RR and TV

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61
Q

What is the major clinical manifestations of hypercapnia in the anesthetized?

A

Vasodilation of peripheral vessels –> increased HR

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62
Q

What clinical manifestations might be seen in an awake, hypercapnic post operative patient?

A 
HA
N/V
sweating & flushing
Shivering
Restlessness
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63
Q

What is an important CNS consideration with hypercapnia?

A

Potent stimulus for cerebral vasodilation

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64
Q

How much does CBF increase with a 1mmHg increase in PaCO2?

A

1-2ml/100gm/min

65
Q

How much can hypercapnia affect pulmonary artery pressure?

A

May produce a 60% increase in PAP

66
Q

What way does the oxyhemoglobin dissociation curve shift with hypercapnia?

A

Rightward shift

67
Q

What are the goals of mechanical ventilation?

A

Maintain adequate gas exchange
Minimize hemodynamic impairment
Avoid lung injury
Avoid injury to distant organs

68
Q

What currently drives our gas machines?

A

Piston driven

69
Q

What type of ventilation is delivered via an iron lung?

A

Negative pressure ventilation

70
Q

What type of ventilation is being used if a square waveform is seen on the monitor?

A

Volume control

71
Q

What type of ventilation is being used if a slanted waveform is seen on the monitor?

A

Pressure control

72
Q

What does the distending pressure measure?

A

Compliance of the lungs

73
Q

What does the resistive pressure measure?

A

Airway resistance

74
Q

What is the pressure in the airway as a product of airway resistance

A

Peak inspiratory pressure (PIP), also known as the opening pressure

75
Q

What is the pressure needed to distend the lung as a product of lung compliance?

A

Plateau pressure, needed to keep the airways open

76
Q

Why might there not be a drop in the pressure wave form after initial opening pressure have been met?

A

If the lungs have poor compliance

77
Q

If the baseline of the pressure curves are elevated what is expected?

A

The use of peep

78
Q

What are mechanical ventilation variables?

A

Elements of a breath that a ventilator can control during delivery of the breath

79
Q

What are the two kinds of variables in mechanical ventilation?

A

Control variables

Phase variables

80
Q

What type of variable does the ventilator control circuit manipulate to cause inspiration?

A

Control variable

81
Q

What are the three types of control variables?

A

Volume
Pressure
Flow

82
Q

How are ventilators classified?

A

Based on the control variable

83
Q

Which variable is used to control the shape of the delivered breath?

A

Control variable

84
Q

What variable varies in volume control ventilation?

A

Pressure

85
Q

What variables vary in pressure control ventilation?

A

Volume and flow

86
Q

What are the four phases of one respiratory cycle?

A

Start of inspiration
Inspiration itself
End of inspiration
Expiration

87
Q

What controls the conventional phases of the respiratory cycle?

A

Phase variables

88
Q

What are the four phase variables?

A

Trigger
Limit (target)
Cycle
Baseline

89
Q

What is the relationship between the trigger variable and the respiratory cycle?

A

Starts inspiration

90
Q

What is the relationship between the Limit variable and the respiratory cycle?

A

Limit reached and maintained at preset level before inspiration ends

91
Q

What is the relationship between the cycling variable and the respiratory cycle?

A

End of inspiration beginning of expiration

92
Q

What is the relationship between the baseline variable and the respiratory cycle?

A

Baseline conditions controlled at end expiration

93
Q

What trigger is independent of the patient effort?

A

Time

94
Q

What three triggers are sensed by the ventilator and delivers a breath in response to it?

A

Pressure
Flow
Volume
As a result of the patient attempting to inhale

95
Q

What are the three limit (target) variables that cannot be exceeded during inspiration?

A

Pressure
Volume
Flow

96
Q

What is the primary phase variable controlled by the ventilator during inspiration?

A

Limit (target) Variable

97
Q

What phase variable is used to cycle from inspiration to expiration?

A

Cycling Variable

98
Q

What are the four variables to cycle from inspiration to expiration?

A

Volume
Flow
Pressure
Time

99
Q

How is the flow cycling variable measured?

A

Flow during inspiration falls to a certain level, typically 25% of the peak inspiratory flow

100
Q

If an inspiratory pause has been set how is the ventilatory cycle changed?

A

Expiration does not immediately follow the delivery of a breath and now becomes time cycled

101
Q

What is the most common baseline variable?

A

Pressure, controlled at end exhalation

102
Q

How is pressure at the end of exhalation achieved?

A

Closure of the expiratory valve before the lung has completely emptied

103
Q

What two components make up the baseline variables?

A

ZEEP, zero relative to atmospheric pressure

PEEP positive related to atmospheric pressure

104
Q

What components determine the ventilator mode?

A

How a breath is initiated, how a breath is delivered, and how it is terminated

105
Q

In a volume controlled ventilator setting, what does adjusting the tidal volume result in?

A

Reduced atelectasis

106
Q

In a volume controlled ventilator setting, what does adjusting the respiratory rate result in?

A

Maintenance of desired PaCO2

107
Q

What are two determining factors f airway pressure?

A

Respiratory system resistance

Compliance

108
Q

How does Volume Controlled Ventilation function?

A

There is a set tidal volume delivered at a constant flow rate and set respiratory rate

109
Q

What is the trigger, limit, cycle and baseline of VCV mode?

A

Trigger: Time
Limit: Flow
Cycle: Volume
Baseline: PEEP if desired

110
Q

When is inspiration terminated in VCV?

A

When a set tidal volume is delivered, regardless of the pressure achieved

111
Q

What is a typical tidal volume to deliver to a patient?

A

6-12mL/kg

112
Q

What is a typical I:E ratio?

A

1:2

113
Q

If PEEP is added to ventilator settings, what is a good number to start at and why?

A

5cmH2O, that is normal physiologic PEEP

114
Q

How does Volume Assist Control Ventilation function?

A

There is a set TV and RR and the patient is able to trigger own breath that is supported by the set volume

115
Q

What are the trigger, limit, cycle and baseline of ACV?

A

Trigger: Time OR pressure/flow (if pt spontaneously breathing)
Limit: Flow
Cycle: Volume
Baseline: PEEP if desired

116
Q

What is a possible complication of ACV ventilation?

A

Muscle atrophy due to unloading of respiratory muscles

117
Q

In ACV ventilation how could a patient determine their own RR?

A

As long as spontaneous RR EXCEEDS the ventilator set rate

118
Q

If a patient becomes apnic on ACV, how does the ventilator respond?

A

Reverts to VCV delivering a set rate and tidal volume

119
Q

How does Intermittent Mandatory Ventilation function?

A

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
Q

What is the trigger, limit, cycle and baseline of IMV?

A

Trigger: Time (because of mandatory breaths)
Limit: Flow
Cycle:Volume
Baseline: PEEP if desired

121
Q

What is a major disadvantage to using the IMV mode?

A

Asynchrony that can lead to breath stacking

122
Q

How does Synchronized Intermittent Mandatory Ventilation function?

A

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
Q

What is the trigger, limit, cycle and baseline of SIMV?

A

Trigger: Time/Patient
Limit: Flow
Cycle: Volume
Baseline: PEEP if desired

124
Q

What is the purpose of the SIMV mode?

A

To allow exercising of the respiratory muscles

125
Q

What are the major benefits of using the SIMV mode?

A

Decreased occurrence of asynchrony and prevention of muscle atrophy

126
Q

What is the function of SIMV + PSV?

A

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
Q

What is the trigger, limit, cycle, baseline for SIMV+ PSV?

A

Trigger: Time/Patient
Limit: Flow/Pressure
Cycle:Volume/Flow
Baseline: PEEP if desired

128
Q

Why might a provider choose pressure control over volume control ventilation?

A

Desire to limit inspiratory pressure

129
Q

What type of patients are at risk for high PIP?

A

COPD
Neonates/infants
LMA

130
Q

What type of patients are we concerned may have low compliance?

A

Pregnancy
Laparoscopic surgery
Morbid obesity
ALI/ARDS

131
Q

What conditions might the provider choose to use pressure control ventilation versus volume control?

A

Concern for high PIP
Concern for low compliance
Compensation for leaks

132
Q

What is the function of Pressure Control Ventilation?

A

There is a preset pressure limited breath is delivered as a set RR, supports apneic patients

133
Q

What is the trigger, limit, cycle and baseline for PCV?

A

Trigger: Time
Limit: Pressure
Cycle: Time
Baseline: PEEP as desired

134
Q

What determines the volume delivered in PCV?

A

Airway resistance and lung compliance

135
Q

What is the benefit of a decelerating flow pattern?

A

Promotes more rapid alveolar filling and more even gas exchange

136
Q

What is a typical pressure limit and recommended max when using PCV?

A

Initially start with 20cmH2O and recommended max 30-35 cmH2O

137
Q

What is the function of Pressure Support Ventilation?

A

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
Q

How much PEEP is required to overcome the resistance of the ETT?

A

5 cmH2O

139
Q

What is the trigger, limit and cycle of PSV?

A

Trigger: Patient (pressure or flow)
Limit: Pressure
Cycle: Flow

140
Q

What can occur if a patient is given excessive levels of pressure support?

A

Respiratory alkalosis
Hyperinflation
Ineffective triggering
Apneic spells

141
Q

What is a major set back to using PSV in patients with COPD?

A

Asynchrony

142
Q

What is the function of PSV-Pro?

A

Spontaneous breathing mode, additional support to achieve optimal TV but there is a built in protection mode if the patient become apneic

143
Q

What is the trigger, limit and cycle in PSV-Pro?

A

Trigger: Patient
Limit: Pressure
Cycle: Flow

144
Q

What mode will PSV-Pro default to if apnea is detected?

A

Back up mode is usually PCV until patient begins breathing spontaneously again

145
Q

If the trigger is too sensitive in PSV-Pro what can cause the ventilator to deliver a pressure support breath?

A

Surgical manipulation
Cardiogenic oscillations
Condensation in the breathing circuit

146
Q

What can occur if the trigger is not sensitive enough in PSV-Pro?

A

The machine will fail to trigger and WOB will increase and may produce coughing and bucking

147
Q

What are the two type of PEEP?

A

Intrinsic “auto PEEP”

Extrinsic “applied PEEP”

148
Q

What are the goals of adding PEEP?

A

Improved oxygenation and Re-expansion of collapsed alveoli

149
Q

What type of patients may require Supra-physiologic PEEP?

A

ARDA/ALI

Pulmonary Edema

150
Q

What are the physiologic effects to adding PEEP?

A

Decreased venous return
Increased ICP
Altered renal function
Barotrauma

151
Q

The incomplete expiration prior to the initiation of the next breath causes progressive air trapping?

A

Auto-PEEP

152
Q

What are some causes of intrinsic PEEP?

A

High minute ventilation
Expiratory flow limitation
Expiratory resistance

153
Q

How do dual modes of ventilation function?

A

The inspiratory pressure is continuously adjusted to insure delivery of the set tidal volume using the lowest possible pressure

154
Q

How does BiVent ventilation function?

A

There are two levels of CPAP, both levels allow the patient to breathe spontaneously

155
Q

What are the two levels set to treat?

A

Low level set to treat hypoxia

High level set to assist in CO@ elimination

156
Q

What is the formula to determine airway resistance?

A

Resistance = PIP - Pplat

Inspiratory flow/min

157
Q

How would you determine the flow rate being delivered to the patient?

A

60 sec/BPM = seconds per breath
Given volume and I:E ratio to calculate mL/sec
Convert to L/min

158
Q

What is the formula to calculate lung compliance?

A

Compliance = Tidal Volume

Pplat - PEEP

159
Q

How would you calculate your I:E ratio?

A

60sec/BPM = seconds per breath
Given TV and flow
Convert to mL/sec

Principles of Monitoring & Fluid balance (3 decks)

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