Respiratory Flashcards
(227 cards)
1
Q
Motor Innervation to the Larynx
A
External branch of the superior laryngeal nerve — Cricothyroid muscle
Recurrent laryngeal nerve - ALL other muscles
2
Q
What is the major motor nerve of the larynx?
A
Recurrent laryngeal nerve
3
Q
What is the major sensory nerve of the larynx?
A
Internal branch of the superior laryngeal nerve
4
Q
Sensory Innervation to the Larynx
A
Internal branch of the superior laryngeal nerve — vocal cords and UP
Recurrent laryngeal nerve - BELOW the vocal cords
5
Q
What laryngeal muscle aBDucts the vocal cords?
A
Posterior cricoarytenoids
6
Q
What laryngeal muscle tenses/tightens/lengthens the vocal cords?
A
Cricothyroid
The voice will go up in pitch!
7
Q
What laryngeal muscle relaxes the vocal cords?
A
Thyroarytenoids
8
Q
What laryngeal muscle aDDucts the vocal cords?
A
Lateral cricoarythenoids
9
Q
What laryngeal muscle closes rima glottidis?
A
Transverse arytenoid
10
Q
What happens with damage to the external branch of the superior laryngeal nerve?
A
Cricothyroid muscle paralysis
Inability to tense the vocal cords
Weakness and huskiness of the voice
11
Q
What happens with unilateral recurrent laryngeal nerve damage?
A
Hoarseness and 1 paralyzed vocal cord
*This is the most common injury after subtotal thyroidectomy
12
Q
What happens with bilateral recurrent laryngeal nerve damage?
A
Aphonia and paralyzed vocal cords
Possible airway obstruction during inspiration
*Intubation is required
13
Q
After a subtotal thyroidectomy, hoarseness may be caused by what 2 things?
A
- Unilateral recurrent laryngeal nerve damage
2. Superior laryngeal nerve damage
14
Q
After a thyroidectomy, stridor may be caused by what 2 things?
A
- Hypocalcemia - tensed cords d/t tetany
2. Bilateral damage to recurrent laryngeal nerves
15
Q
Define P50.
A
P50 is the partial pressure of oxygen at which Hgb is 50% saturated by oxygen
16
Q
What is the normal P50?
A
26-27 mmHg
17
Q
What SO2s correspond to PO2s?
A
70% - 40 mmHg — mixed venous blood
80% - 50 mmHg
90% - 60 mmHg — arterial blood
18
Q
What is the significance of the flat portion of the oxy-hbg dissociation curve?
A
Facilitates the loading of oxygen by the blood
Pulmonary circulation
Shift Left
19
Q
What is the significance of the steep portion of the oxy-hgb dissociation curve?
A
Facilitates the unloading of oxygen at tissues
Systemic circulation
Shift Right
20
Q
What causes a leftward shift in the oxy-hgb dissociation curve?
A
Opposite of CADETS Hemoglobin F Carboxyhemoglobin Methemoglobin LEFT LINGERS
21
Q
What causes a rightward shift in the oxy-hgb dissociation curve?
A
CADETS to the R...INCREASED CO2 Acidosis DPG 2,3 Exercise Temp Sickle cell (HgbS) Maternal hemoglobin! RIGHT RELEASES
22
Q
What is the Bohr effect?
A
How does a change in CO2 shift the oxy-hgb dissociation curve?
23
Q
Administration of opioids shifts the oxy-hgb dissociation curve in which direction?
A
Right
Respiratory depression - CO2 accumulates
24
Q
Is oxygen release from Hgb to the the tissues increased or decreased by acidosis?
By alkalosis?
A
Acidosis is a shift right - releases - increases O2 delivery
Alkalosis is a shift left - lingers - decreases O2 delivery
*Alkalosis can be worse than acidosis
25
How do you calculate the amount of dissolved O2 in the blood?
Whose law permits this calculation?
0.003 x PO2
Units: mL O2/100 mL blood
Henry's Law
26
What is Henry's Law?
At a constant temp, the amt of a gas that dissolves in a liquid is directly proportional to the partial pressures of that gas in equilibrium with that liquid
27
O2 is carried in the blood in what 2 forms?
1. Hemoglobin-bound
| 2. Dissolved in blood
28
What is the max O2 carrying capacity of arterial blood if a healthy person is breathing room air?
20. 4 mL O2/100 mL blood
| 20. 1 carried by Hbg + 0.3 dissolved
29
Switching from room air to 100% O2 causes a small or large increase in the amount of dissolved and hgb-bound oxygen?
Small
(we are talking about a healthy patient)
Patients who have poor perfusion in relation to ventilation (dead space) respond well to O2 therapy
Patients with shunts are less responsive to O2 therapy
30
Define hypoxia.
PaO2 < 60 mmHg
31
What is the amount of oxygen carried by each gram of fully saturated Hgb?
1.34 mL O2 per g Hgb
32
How do you calculate the amount of oxygen bound to Hgb?
1. 34 x Hgb x % sat
| 1. 34 x 15 x 0.9 = 18.1
33
If SvO2 is 70%, how much oxygen is dissolved in venous blood?
If SvO2 is 70% then PvO2 is 40 mmHg
| O2 dissolved = 40 x 0.003 = 0.12
34
What is the Haldane Effect?
Describes how a change in PO2 influences the blood CO2 dissociation curve
How changes in PO2 in the blood alter the amount of CO2 carried by the blood
35
Haldane Effect
| When PO2 increases, the blood CO2 dissociation curve shifts...
DOWN and to the RIGHT
Unloading of CO2 to the lungs
Pulmonary circulation
36
Haldane Effect
| When PO2 decreases, the blood CO2 dissociation curve shifts...
UP and to the LEFT
Loading of CO2 into the blood
Systemic circulation
37
What effect does opioid administration have on the blood CO2 dissociation curve?
PO2 decreases with respiratory depression caused by opioids
| When PO2 decreases, CO2 dissociation curve shifts UP and to the LEFT
38
Approx. 90% of the CO2 transported by the blood is in what form?
HCO3
39
How does CO2 become HCO3 in RBC?
RBC:
CO2 + H2O - carbonic anhydrase - H2CO3 - HCO3 + H
HCO3 then diffuses OUT of the RBC down a concentration gradient
Cl diffuses IN RBC - electroneutrality is maintained
*Chloride Shift aka Hamburger Shift in non-pulmonary capillaries
40
CO2 is carried in the blood in what 4 forms?
1. Dissolved (5%)
2. Bound to proteins and hemoglobin (5%)
3. As Bicarb (90%)
4. As carbonic acid (< 1%)
41
Chloride Shift aka Hamburger Shift in Pulmonary Capillaries
CO2 diffuses from plasma to alveoli
CO2 diffuses from RBC to plasma
HCO3 diffuses IN RBC
Cl diffuses OUT of RBC
42
How do you calculate the amount of CO2 dissolved in blood?
PCO2 x 0.0067
| Units: Units: mL CO2/100 mL blood
43
Central chemoreceptors are stimulated by...
Increased H
| When CO2 in CSF increases, the H and Bicarb concentrations increase - Le Chatelier's principle (law of mass action)
44
What drives respiration?
CO2
| *The single most important regulator of alveolar ventilation is PaCO2
45
Peripheral chemoreceptors are stimulated by...
1. Increased PCO2
2. Decreased pH (increased H)
3. Decreased PaO2 (< 60 mmHg)* most sensitive
* Also by cyanide, doxapram, nicotine
46
The glossopharyngeal nerve carries sensory impulses from the...
Carotid bodies
47
The vagus nerve caries sensory impulses from the...
Aortic bodies + stretch receptors found in the lung parenchyma (bronchi or bronchioles)
48
List the 4 respiratory centers.
1. Dorsal Respiratory Group (DRG)
2. Ventral Respiratory Group (VRG)
3. Pneumotaxic Center (PnC)
4. Apneustic Center (ApC)
49
What is the Dorsal Respiratory Group (DRG) responsible for?
| Where is it found?
Basic rhythm of respiration - inspiratory pacemaker!
Controls diaphragm and external intercostal muscles
Found in the medulla
50
What is the Ventral Respiratory Group (VRG) responsible for?
Where is it found?
Can influence BOTH inspiration and expiration
Comes into play when high levels of ventilation are required
Controls internal intercostal muscles
Found in the medulla
51
What is the Pneumotaxic and Apneustic Centers responsible for?
Where are they located?
PnC shuts OFF inspiration
PnC is located high in the pons
aka Pontine Respiratory Group (PRG)
ApC promotes deep and prolonged inspiration
ApC is located low in the pons
*Work together to control the RATE and DEPTH of INSPIRATION
52
Smooth muscle of bronchi and bronchioles has receptors that fire when stretched, which reflexly tends to inhibit inspiration. This is known as the ________ reflex.
What nerve is involved?
Hering-Breuer inflation
Vagus nerve carries this sensory info
*Protective mechanism to prevent excess lung inflation
53
In adults, the Hering-Breuer reflex does NOT become important until the TV exceeds what?
1. 5 L
| * In neonates, this reflex is strong and relevant
54
Where are peripheral chemoreceptors found?
Mostly in the carotid bodies
| Also in the aortic bodies
55
Describe the intrapleural space.
A potential space
Found b/t the parietal pleura of the internal chest wall and the visceral pleura covering the lung
Pressure here is NEGATIVE
Lungs recoils inward and the chest recoils outward
Inward forces = outward forces at FRC
56
Describe the changes in intrapleural and intrapulmonary pressures during inspiration.
Intrapleural pressure - MORE negative
Intrapulmonary pressure - negative
Suck air IN
57
Describe the changes in intrapleural and intrapulmonary pressures during expiration.
Intrapleural pressure - LESS negative
Intrapulmonary pressure - positive
Push air OUT
58
When does intrapleural pressure become positive?
During a forced expiration
| During maneuvers such as Valsalva
59
Since MV is normally 4 L/min and CO is normally 5 L/min, the average V/Q for the lungs is...
0.8
60
Nondependent vs. Dependent Differences
Nondependent: high V/Q, intrapleural pressure more negative, larger alveoli, PaO2
Dependent: perfusion, ventilation, low V/Q, intrapleural pressure less negative, smaller alveoli, PaCO2
61
What changes cause a clinically significant mismatch in ventilation and perfusion?
When the patient in the lateral decub position is anesthetized and paralyzed
Nondependent lung is well ventilated BUT poorly perfused (dead space)
Dependent lung is well perfused BUT poorly ventilated (shunt)
62
What does a V/Q ratio of 0 mean?
Absolute shunt - no ventilation
63
What does a V/Q ratio of infinity mean?
Absolute deadspacing - no perfusion
64
True or False
| PaO2 ALWAYS decreases when there is a V/Q mismatch.
True
65
What are 3 causes of low PaO2?
1. Low inspired O2
2. Hypoventilation
3. V/Q mismatching
66
What is the normal PAO2 to PaO2 gradient when breathing room air?
5-15 mmHg
| *Gradient increases when inspired oxygen increases - if 100% O2 gradient should be < 100 mmHg
67
What is the normal PaCO2 to PACO2 gradient?
2-10 mmHg
| *This gradient is independent of the inspired O2 concentration
68
How do you differentiate between hypoxemia d/t hypoventilation or V/Q mismatch?
```
Determine the
PAO2 to PaO2 (degree of R to L shunt)
OR
PaCO2 to PACO2 (degree of dead spacing)
Gradient
```
69
How does the PAO2 to PaO2 gradient vary with age?
Normal PAO2 to PaO2 = 0.21 x (age +2.5)
70
What represents the average alveolar CO2 (PACO2)?
End-tidal CO2
71
What is the normal PaO2/PAO2 ratio?
> 0.75
Assess V/Q abnormalities like the gradient
A decrease in this ratio reflects a shunt
*Advantage - not affected by changes in inspired O2
72
You can estimate the PaO2 in a healthy patient by x % O2 by...
5
| %O2 x 5 = PaO2
73
You can estimate the PAO2 in a healthy patient by x % O2 by...
6
| %O2 x 6 = PAO2
74
What is happening if V/Q is 4?
Deadspace
75
One-Lung Ventilation
| Strategies for Maintaining Arterial Blood O2
Selective non-dependent lung CPAP*
| Non-dependent lung CPAP + Dependent lung PEEP
76
What is the major determinant of regional differences in pulmonary ventilation?
Intrapleural pressure gradient
| More negative in non-dependent - alveoli don't collapse as much - require less air to fill - less compliant
77
Does a V/Q mismatch have a greater effect on PaO2 or PaCO2?
PaO2
78
A patient has unilateral lung disease. What position will optimize blood oxygenation?
Lateral decubitus healthy lung dependent
Lateral decubitus healthy lung nondepedent
Supine
Lateral decubitus position with the healthy lung in the dependent position
79
Does hyperventilation help improve blood oxygenation?
No, hyperventilation does little to improve blood oxygenation d/t the S shape of the oxy-hgb curve - think flat portion: increasing ventilation produces only a small increase in the amount of oxygen in arterial blood
Consider the hgb saturated already
*Hyperventilation does dramatically decrease PaCO2 (linear CO2 dissociation curve)
80
West Zones of the Lungs
| Name the 4 zones.
1. Collapse PA > Pa > Pv
2. Waterfall Pa > PA > Pv intermittent BF
3. Distention Pa > Pv > PA continuous BF
4. Interstitial pressure Pa > Pisf > Pv > PA
81
Name 2 pathological zones of the lung.
Zone 1: NO blood flow, develops with pulmonary hypotension
| Zone 4: develops with pulmonary edema
82
Where should the tip of a Swan-Ganz cath be?
Zone 3
83
What do West Zones describe?
Perfusion
84
Are West Zones "fixed" zones?
NO, they are variable, functional zones
85
The FRC is a reservoir for...
O2
86
Pre-oxygenation with 100% O2 for 5 min can furnish up to ___ minutes of oxygen reserve following apnea.
10
87
What is the most common reason for not achieving a max alveolar FiO2 during pre-oxygenation?
Loose-fitting mask
88
What is oxygen consumption (VO2)?
| What is the total quantity of O2 delivered to and used by the tissues each min?
250 mL O2/min
3-4 mL O2/kg/min
0.3-0.4 mL O2/100g/min
*Oxygen delivery matches oxygen consumption
89
In response to ALVEOLAR hypoxia, the blood vessels _________. This effectively decreases _________. What is the name of this mechanism?
Constrict
Shunt
Hypoxic Pulmonary Vasoconstriction (HPV)
90
What are some drugs that inhibit HPV?
Direct-acting vasodilators - nitroprusside, nitroglycerine, hydralazine
Volatile agents > 1 MAC
91
What falls when shunt increases?
PaO2
92
In regards to ventilatory defects, which is most amendable to treatment?
COPD
| *Restrictive disorders are generally difficult to reverse
93
What 3 lung volumes are NOT directly obtainable from spirometric recordings?
1. FRC
2. RV
3. TLC
94
FRC =
ERV + RV
95
Inspiratory capacity =
IRV + TV
96
Vital capacity =
IRV + TV + ERV
97
Define FEV1.
Forced expiratory volume in 1 sec
98
Define FVC.
Volume of gas that can be exhaled during a forced expiratory maneuver
99
Define FEF25-75.
Rate of flow occurring in a forced expiratory flow from the point where 25% of the FVC has been exhaled to the point where 75% has been exhaled
aka midmaximal expiratory flow (MMEF)
100
What is the best test for assessing small airway disease?
FEF25-75
MMEF
Normal 4.7 L/sec
101
What is the normal values for the following:
FEV1
FVC
FEV1/FVC
FEV1 - 4
FVC - 5
FEV1/FVC - 0.8
102
Obstructive Spirometry Values
FEV (more significantly) and FVC are decreased
| FEV1/FVC is LOW < 0.7
103
Restrictive Spirometry Values
ALL values are decreased!
| FEV1/FVC in NORMAL or > 0.7
104
If FEV1 < 2 L and FEV1/FVC < 50%, should you go along with the case?
NO, request more sophisticated split lung function tests
105
Flow Volume Loops
Normal shape looks like a...
What is represented on the x-axis? Y-axis?
Is expiration below or above the x-axis?
Is inspiration below or above the x-axis?
```
Guitar pic
X-axis = lung volume (L) - far right is 0*
Y-axis = flow (L/sec) - middle is 0
Expiration is above the x-axis
Inspiration is below the y-axis
```
106
What does the flow volume loop look like in restrictive pathology?
Same shape as normal BUT smaller
| Found to the right (far right is 0 L)
107
What does the flow volume loop look like in obstructive pathology?
Looks like a baby carriage
Expiration limb is caved in
Lung volumes are greater
Found to the left (far right is 0 L)
108
What does the flow volume loop look like if there is a variable extrathoracic obstruction?
Expiration limb is normal
Inspiration limb is flat - obstructed segment collapses b/c airway pressure is subatm
EXTRAthoracic --- INSpiration
109
What does the flow volume loop look like if there is a variable intrathoracic obstruction?
Inspiration limb is normal - obstructed segment widens b/c of negative intrapulmonary pressure
Expiration limb is flat - obstructed segment collapses
INTRAthoracic --- EXpiration
110
What does the flow volume loop look like with a fixed large airway (tracheal) obstruction?
Both inspiration and expiration limbs are abnormal - flat
111
As fluid (liquid or gas) flows through a tube, pressure ______. In the airway, pressure ______ as gas flows along the bronchioles. This is the physical basis of airway closure.
Falls
Falls
*At some point in the airway, the intrapleural pressure sufficiently exceeds airway pressure and the airway closes.
112
Intrapleural pressure _________ during forced vital expiration or Valsalva maneuver.
Increases
113
Airway closure during forced expiration occurs in the young healthy person at some volume less than what?
FRC
| *Expiration must be forced to achieve lung volumes where airway closure occurs
114
Define closing volume.
Forced expiration
Airways begin to close
Volume that can subsequently be exhaled = CV
115
Define closing capacity.
CC = CV + RV
116
How are the CV and CC measured?
Nitrogen washout test
| Helium dilution method
117
As we age, do CV and CC increase or decrease?
Increase
| *The volume at which airway closure occurs increases progressively with age
118
In young, healthy individuals, airway closure occurs at a lung volume equal to about ___% of vital capacity.
10%
119
Closing capacity is equal to what in the healthy upright 66 yo?
FRC
| CC = FRC in 66 yo upright
120
In the healthy supine 44 yo, closing capacity equals what?
FRC
| CC = FRC in 44 yo supine
121
Besides aging, what increases closing volume?
Obstructive pulmonary disease
Emphysema - loss of collage and elastin, airways close easier
Chronic bronchitis and asthma - airways are narrower, pressure drop is greater
122
Besides aging and obstructive pulmonary disease, list 5 more conditions that increase CV.
1. Smoking
2. Bronchospasm
3. Airway secretions
4. Fluid retention
5. Anesthesia/surgery
123
Does pulmonary compliance increase or decrease with age?
Increases
Elastin and collagen break down - so the lung tissue becomes easier to distend
*Elasticity decreases
124
How does FRC change with age?
Increases
| Lung does not recoil inward with as much force
125
Does chest wall compliance increase or decrease with age?
Decreases
126
Talk about FRC, VC, RV, and TLC in reference to obstructive pulmonary disease.
FRC (RV + ERV) increases d/t increased RV
VC (ERV + TV + IRV) decreases
RV increases (trapped air)
TLC increases d/t increased RV
127
Talk about FRC, VC, RV, and TLC in reference to restrictive pulmonary disease.
ALL decrease!
128
During normal tidal breathing, when is intrapleural pressure positive?
Never!
129
Compare PACO2 in the base with PACO2 in the apex when the patient is in the prone position.
PACO2 is the same in the base as the apex
130
What nerve innervates the posterior 1/3rd of the tongue?
CN 9 - Glossopharyngeal
131
What nerve innervates the anterior 2/3rds of the tongue?
CN 7 - Facial
132
What muscle acts as a barrier to regurgitation in the conscious subject?
Cricopharyngeus muscle
133
List the 9 laryngeal cartilages.
1. Epiglottis
2. Thyroid
3. Cricoid
4. Arytenoids (2)
5. Cuneiforms (2)
6. Corniculates (2)
134
Laryngospasm is caused by stimulation of which nerve?
Superior laryngeal nerve (external branch)
135
What muscles are involved in a laryngospasm?
Cricothyroids
136
What are the muscles of inspiration? Which is the most important?
Diaphragm* most important
| External intercostals
137
What nerve innervates the diaphragm? What segments of the spinal cord?
Phrenic nerve
| C 3,4*,5
138
What muscles are involved in increasing the AP diameter of the thorax?
External intercostals*
SCM (lift sternum)
Anterior serrati (lift ribs)
Scaleni (lift 1st 2 ribs)
139
What muscles are employed to force expiration.
Abdominal recti
| Internal intercostals
140
Define anatomic dead space.
Volume of air in the conducting airways (gas exchange does not occur here)
50% is in the upper airway
*2 mL/kg
141
Define alveolar dead space.
Volume of inhaled gas that enters non-perfused alveoli
142
Define physiologic dead space.
Physiologic = anatomic + alveolar dead space
| Hopefully physiologic = anatomic
143
Identify 4 situations that are associated with a significant increase in dead space.
1. Age
2. PPV
3. PE
4. Lung disease
144
What % of TV in a spontaneously breathing adult is dead space? In a paralyzed, mechanically ventilated patient?
Spontaneously breathing - 33% of TV
| Paralyzed, mechanically ventilated - 40-60% of TV
145
With each breath, what fraction of the TV mixes with alveolar air?
2/3rds
| 1/3rd is dead space
146
What site in the trachea produces the strongest cough reflex when stimulated?
Carina
147
What respiratory cells secrete mucus?
Goblet cells
148
Define compliance.
Change in volume that occurs in response to a change in pressure
Measure of ease with which a structure is distended
Large compliance - easy to distend
149
Define resistance.
Change in pressure along a tube divided by flow
| Measure of ease with which a fluid flows through a tube
150
What cells secrete surfactant?
Type II alveolar epithelial cells
Lipoprotein mix
Major phospholipid - dipalmitoyl lecithin
151
Discuss the 3 functions of surfactant.
1. Decreases surface tension (increases pulmonary compliance, decreases WOB)
2. Permits alveolar stability (prevents small alveoli collapse)
3. Keeps alveoli dry
152
Normally, surface tension _______ as alveoli become smaller.
Decreases
The job of surfactant
*Law of Laplace
153
Define FRC.
Volume of gas left in the lungs after a normal exhalation
| Outward chest recoil = Inward lung recoil
154
More than 2/3rds of the WOB is used to overcome what?
Elastic recoil of lungs and thorax
155
What is the cause of exhalation?
Passive elastic recoil of the lungs
156
The intrapleural pressure is the same at the base as the apex in the following 3 positions.
1. Supine
2. Prone
3. Lateral decubitus
* Intrapleural pressure changes in the vertical direction, not in the horizontal direction.
157
What happens to intrapleural pressure during inspiration if the patient is on a positive pressure mechanical ventilator?
Intrapleural pressure increases during inspriation (becomes LESS negative)
158
What happens with the Valsalva maneuver?
```
Forced expiration with the glottis closed
ALL intrathoracic pressures increase!
Intrapleural pressure will be positive!
VR decreases
CO and BP decreases
HR increases (baroreceptor reflex)
```
159
Give 3 formulas for TLC.
```
TLC = VC + RV
TLC = IRV + TV + ERV + RV
TLC = IC + FRC
```
160
RV is normally what % of TLC?
20%
161
Calculate alveolar ventilation.
Alveolar ventilation = (TV - dead space) x RR
| *Dead space = 2 mL/kg
162
Increasing which component of MV most improves alveolar ventilation?
TV
| An increase in TV increases MV withOUT increasing dead space ventilation
163
What happens to end-tidal CO2 when fresh gas flows and MV are increased?
ETCO2 decreases
| *ETCO2 becomes dependent on MV
164
What will happen with TV and MV with high fresh gas flows?
TV and MV will increase
165
How are PaCO2 and ETCO2 related to alveolar ventilation?
PaCO2 and ETCO2 are inversely proportional to alveolar ventilation
166
What are the 2 determinants of PaCO2?
1. CO2 production
| 2. Alveolar ventilation
167
Alveolar air is ______% humidified at 37 deg C.
100%
168
Calculate the partial pressure of CO2 in expired gas if end-tidal CO2 is 5%.
ETCO2 = 0.05 x 760 = 38 mmHg
| *Dalton's Law of Partial Pressures
169
What volume of blood is found in the pulmonary circuit? What % of the total blood volume?
450 mL
| 9% of the total blood volume
170
Is an intrapulmonary shunt a R to L or a L to R shunt?
Blood passes from the pulmonary artery to the pulmonary vein
R to L shunt
171
What is the major consequence of a shunt?
Decrease in PaO2
172
What is the major consequence of dead spacing?
Increase in PaCO2
173
What is responsible for decreasing a shunt?
Hypoxic pulmonary vasoconstriction
| In the response to alveolar hypoxia, pulmonary vessels constrict
174
What is the partial pressure of oxygen in mixed venous blood (PvO2)?
40 mmHg
| Oxygen saturation of 70%
175
What is the normal CaO2 - CvO2?
5 mL O2/100 mL
| This says that 5 mL of O2 are extracted from each 100 mL of blood by tissues
176
What 2 changes can cause SaO2 to remain normal and SvO2 to decrease?
What determines mixed venous oxygen content or saturation (MvO2, SvO2)?
* Increased extraction from the tissues
1. Decrease in O2 delivery (decreased CO, Hgb concentration)
2. Increase in O2 consumption (fever, shivering, MH, thyroid storm)
177
What 2 factors determine the amount of oxygen carried by Hgb?
1. PO2
| 2. Amt of Hgb
178
____ mL of O2 is carried by each gram of saturated hemoglobin.
1.34
179
If a question asks you to calculate the maximum oxygen carrying capacity what do you need to consider?
```
Oxygen bound to Hgb (1.34)
Oxygen dissolved (0.003)
```
180
Iron is in what state in methemoglobinemia?
Normal Hgb - iron in the ferrous state (Fe2+)
| Met-Hgb - iron in the ferric state (Fe3+)
181
Which patient will most easily become cyanotic...the anemic or the polycythemic?
Polycythemic
| Cyanosis develops when there is 5g/100 mL of reduced Hgb
182
What is the best assessment of the adequacy of CO?
Mixed venous oxygen tension or saturation
| *In the absence of hypoxia or severe anemia
183
Stated simply, venous blood oxygen saturation provides what info?
Relationship b/t oxygen delivery and consumption
184
What is the CO2 content in room air?
0.03%
185
Which is more soluble: O2 or CO2?
CO2 is approx. 20x more soluble than O2
186
How much CO2 is normally produced and eliminated per min?
200 mL/min
| 2.4-3.2 mL/kg/min
187
How many mL of CO2 is expired from the lungs per 100 mL of blood?
CO excretion = 200 mL/min
CO = 5 L/min
200/5000 = 4 mL CO2/100 mL
188
What is the total CO2 content of arterial blood? Venous blood? CvCO2-CaCO2?
Arterial - 48 mL CO2/100 mL of blood
Venous - 52 mL CO2/100 mL of blood
CvO2-CaCO2 = 4 mL CO2/100 mL of blood - This says that 4 mL of CO2 are eliminated from each 100 mL of venous blood
189
Compare the amounts of O2 and CO2 carried in arterial blood.
O2 - 20 mL O2/100 mL
| CO2 - 48 mL/100 mL
190
What lab value will exclude CO2 retention from a diagnosis?
Normal Bicarb values
| *For every 10 mmHg increase in PCO2, HCO3 will increase by 1 mmol/L
191
The ventilatory response to a increased PaCO2 is mediated primarily by...
Central chemoreceptors
*The effect of CO2 on central chemoreceptors is 7x more powerful than it is on peripheral chemoreceptors!
Central chemoreceptors are MORE important than peripheral chemoreceptors in controlling ventilation
192
What is the most common cause of hypocapnia?
Hyperventilation by mechanical means
193
What are pulmonary J-receptors?
Juxtapulmonary-capillary receptors
Stimulated by pulmonary vascular congestion
Leads to tachypnea and dyspnea
Afferent pathway, unmyelinated C fibers in the vagal nerves
194
What lung volume is increased in chronic smokers compared to nonsmokers?
Closing volume
| Increased air trapping
195
Smoking should be stopped how many weeks prior to surgery?
> 6 weeks before surgery
| Benefits occur within 2-3 mo following cessation
196
How long does it take for the polycythemia to normalize in a smoker after cessation?
5 days
197
Cessation of smoking ______ hrs pre-op reduces carboxyhemoglobin levels and nicotine levels
12-24 hrs
P50 increases from 23 to 26 mmHg
CarboxyHgb decreases from 6.5% to 1%
*Short-term cessation of smoking does NOT decrease the incidence of post-op M and M
198
What does the increased gradient b/t ETCO2 and PaCO2 indicate in the chronic smoker?
Reflects the degree of V/Q mismatch
| Dead space ventilation
199
What happens to lung compliance in the smoker?
Increases
| Loss of elastic recoil
200
What provides a large safety factor for preventing pulmonary edema?
A high colloid osmotic pressure (force holding water in the pulmonary capillaries)
Colloid osmotic pressure = 28 mmHg
Hydrostatic pressure = 6-8 mmHg
201
What is the most common cause of acute pulmonary edema?
Increased hydrostatic pressure secondary to LV failure (cardiogenic pulmonary edema)
202
Why does large amounts of isotonic saline promote the development of pulmonary edema?
Plasma proteins are diluted so...
Colloid osmotic pressure decreases
Hydrostatic pressure increases
203
What is the traditional hallmark of early pulmonary edema?
Detection of basilar crackles on auscultation
| A "butterfly" or "whited-out" appearance of chest radiographs supports the diagnosis
204
What is the earliest and most reliable sign of aspiration?
Hypoxemia
205
What is the most serious complication of aspiration?
ARDS
Mendelson's syndrome
*Will see fluffy infiltrates on chest x-ray
206
The affinity of CO for Hgb is ___x greater than that of oxygen.
200-250x
| *CO poisoning tx = 100% O2 to displace CO
207
CO poisoning causes what type of hypoxia?
Tissue hypoxia
*PO2 may be high
Carboxy-Hgb is unable to carry oxygen = functional anemia
208
What is the result of prolonged 100% O2 administration?
Loss of surfactant
| Prolonged exposure to O2 radicals
209
What is refractor to oxygen therapy?
R to L shunts
210
Administration of 50% nitrous oxide will result in how much of an increase in the size of the pneumothorax?
Doubling of the size
211
Define paradoxical breathing.
Inspiration - increased collapse of the lung
Expiration - collapsed lung expands
*Open pneumothorax
212
Concerns for a patient with cystic fibrosis.
Very thick mucus secretions - infection, obstruction, collapse
Risk for bleeding - poorly absorb Vit K
Give higher FiO2, humidify gases, use inhalation agents, keep normocarbic, hydrate
Avoid glyco and atropine - make secretions harder to remove
213
What does an ABG look like during an asthma attack?
Low PaO2
Low CO2
Alkalosis
214
What 2 types of drugs should be avoided in the patient with asthma?
1. Beta 2 Blockers
| 2. Histamine releasers
215
What happens to airway resistance and pulmonary compliance in the patient with COPD?
Increased airway resistance
| Increased pulmonary compliance
216
What is the primary mechanism of hypoxemia in the patient with COPD?
V/Q mismatch
217
COPD patient relies on what for breathing?
Peripheral chemoreceptor oxygen drive
*Raising PaO2 > 60 mmHg can precipitate respiratory failure
Chronic elevation of PaCO2 - increased Bicarb in CSF - reset chemoreceptors - decrease sensitivity to CO2
218
Tracheal stenosis is an example of obstructive or restrictive pathology? Intrathoracic or extrathoracic?
Obstructive
| Fixed extrathoracic obstruction
219
How does aminophylline work?
Produces bronchodilation by inhibiting phosphodiesterase causing cAMP accumulation
*Can be used to reverse respiratory depression
220
How does cromolyn sodium work?
Mast cell stabilizer
Works by blocking the degranulation of mast cells and subsequent release of histamine
Used to prevent bronchospasm, NOT effective for treatment
221
How does ipratropium work?
Antimuscarinic (decrease in IP3 and Ca)
| Quaternary ammonium drug - non systemic effects when inhaled
222
What respiratory volume does NOT change in obstructive disease?
NO change in TV
223
What are the principle causes of death in patients with kyphoscoliosis?
Restrictive lung disease
| Pulmonary HTN
224
Respiratory reserve is assessed by what 3 things?
1. Exercise tolerance
2. Vital capacity*
3. ABGs
225
If hypoxia occurs during OLV, what steps should you take?
1. Check the position of the tube
2. Increase RR
3. CPAP* to nondependent lung
4. PEEP to dependent lung
5. Intermittent ventilation of nondependent lung
6. Ligation or clamping of PA
226
List 4 reasons for increased peak inspiratory pressures.
1. ETT obstruction
2. Accumulation of secretions, blood, or edema
3. Bronchospasm
4. Endobronchial intubation
227
What happens to PIP if there is a partial obstruction of the inspiratory valve?
PIP will decrease
| *PIP is measured on the patient side of this obstruction
