Respiratory - High Yield Points Flashcards
1
Q
The primary function of the lungs is…
A
gas exchange
2
Q
What four processes must be functioning for optimal gas exchange?
A
Ventilation
Perfusion
Diffusion
Control of breathing
3
Q
Optimal Gas Exchange
Ventilation
A
Getting gas to the alveoli
4
Q
Optimal Gas Exchange
Perfusion
A
removing gas from the alveoli by the blood
5
Q
Optimal Gas Exchange
Diffusion
A
Getting gas across alveolar walls
6
Q
Optimal Gas Exchange
Control of Breathing
A
regulating gas exchange
7
Q
What structures make up the conducting zone?
A
Trachea
Bronchi
Bronchioles
No alveoli
8
Q
What structures make up the Respiratory Zone?
A
Respiratory Bronchioles
Alveolar Ducts
Alveolar Sacs
Alveoli
9
Q
Characteristics of Alveoli
A
Small, thin walled inflatable air sacs encircled by pulmonary capillaries
Single layer of thin exchange epithelium
Air flows between alveoli via pores of Kohn
10
Q
Where is the site of gas exchange in alveoli?
A
The single layer of thin exchange epithelium
11
Q
Define
Type I Alveolar Cells
A
Very thin
allowing gas exchange
12
Q
Define
Type II Alveolar Cells
A
Thicker
Secrete surfactant to ease lung expansion
13
Q
Define
Alveolar Macrophages
A
Protect and Defend
14
Q
Define
Atmospheric Pressure (PB)
What is it at sea level? How does it change?
A
760 mmHg at sea level
decreases as altitude increases
15
Q
Define
Intra-alveolar pressure (PA)
What is its value?
A
Equilibriates with PB
16
Q
Define
Intrapleural Pressure (Pip)
Value? What is it?
A
756 mmHg
Recoil forces create a vacuum (-4)
Closed cavity
17
Q
Define
Transmural Pressure (PL)
A
Pressure across the lungs
Key to inflating the lungs
18
Q
What is the purpose of the cohesiveness of Intrapleural Fluid and the transmural pressure gradient?
A
They hold the lungs and thoracic wall in tight position even though the lungs are smaller
PA = 760, pushes out vs. Pip of 756
PB = 760, pushes in vs. PIP
19
Q
Why does the pleural space have a slightly negative pressure?
A
Because the chest is pulling out, the lungs are pulling in, and there’s no extra fluid to fill the expanded space
20
Q
Pneumothorax
What causes it? What occurs with one?
A
Air enters pleural cavity
Pressure equalizes with atmospheric pressure
transmural pressure gradient is gone
Lungs collapse
Thoracic wall springs out
21
Q
Define
Boyle’s Law
A
Volume and pressure are inversely related
↓V↑P
22
Q
Changes in volume of chest cavity during ventilation cause…
A
Pressure gradients
↑Chest Volume ↓Pressure → air moves into body from atmosphere
23
Q
Inspiration results from…
A
contraction of the diaphragm and intercostal muscles `
active process
24
Q
During inspiration, the rib cage swings…
A
upwards and outwards
25
Expiration results from...
the relaxation of the diaphragm and intercostal muscles
| passive process
26
During expiration, the rib cage moves...
inward and downwards
27
How is air forced out of the lungs during expiration?
The elastic recoil of the lungs creates a higher intra-alveolar pressure compared to atmospheric pressure that forces air out of the lungs
28
# Define
Laminar Airflow
| What is it? Where is it?
Low flow rate
usually in small airways
29
# Define
Turbulent Airflow
| What is it? Where is it?
Fast flow rate
usually in large airways
30
How much do terminal bronchioles contribute to total resistance?
Each terminal bronchiole has a high resistance to flow, but they have a large cross-sectional area and are in parallel
Their overall contriution to total R is low
31
Air flow in the respiratory system increases as...and decreases as...
increases as the pressure gradient increases
decreases as resistance increases
| Airflow = ΔP/R
32
Where is airway resistance greatest? How is it measured?
Greatest in medium sized airways
Measured with Poiseuille's Law R = (8nl)/3.14r^4
33
What is the relationship between airway radius and resistance?
Airway radius is a pimary determinant of resistance
| Length and viscosity are virtually constant
34
Why is the diameter of the bronchiole adjustable?
No cartilage but has smooth muscle
35
# Bronchioles
Bronchoconstriction
## Footnote
What causes it? What effect does it have on resistance and airflow?
Caused by low levels of CO2
increases resistance
decreases air flow
36
# Bronchioles
Bronchodilation
##Footnote
What causes it? What effect does it have on airflow?
caused by increased CO2
increases airflow
37
# Define
Equal Pressure Point (EPP)
When airway pressure is equal to intrapleural pressure
38
What is the purpose of Pulmonary Function Tests?
they measure lung volumes, lung capacities, and flow rate
They can detect abnormalities in lung function before diseases are symptomatic
39
# Define
Tidal Volume (TV)
Air volume moving in a single normal inspiration or expiration
40
# Define
Inspiratory Reserve Volume (IRV)
Additional volume inspired above tidal volume
41
# Define
Expiratory Reserve Volume (ERV)
Air exhaled beyond the end of normal expiration
42
# Define
Residual Volume (RV)
Air in respiratory system after maximal exhalation (not measured directly)
43
What are lung capacities?
The sums of 2 or more lung volumes
44
# Define
Vital Capacity (VC)
| Define; How do you calculate it?
Max volume of air voluntarily moved through respiratory system
VC = IRV + ERV + VT
45
# Equation
Total Lung Capacity (TLC)
TLC = VC + RV
46
# Equation
Inspiratory Capacity (IC)
IC = VT + IRV
47
# Equation
Functional Residual Capacity (FRC)
FRC = ERV + RV
48
Obstructive lung disease is characterized by...
Increases in lung volumes and airway resistance and decreases in expiratory flow rates
49
# Define
Emphysema
| What is it? Characteristics?
Type of COPD
characterized by increasing lung compliance and decreased diffusion capacity for carbon monoxide
| Obstructive Lung Disease
50
Restrictive Lung Diseases are characterized by...
decreases in lung volume
normal expiratory flow rates
normal resistance
marked decrease in lung compliance
51
# Define
Compliance
The ability of the lungs to stretch
↑stretch↑compliance
Defined by slope of pressure volume curve for lungs
52
How does the slope of the pressure - volume curve for lungs change?
Steep slope is seen at low and normal lung volumes
Curve flattens at very high volumes
53
High compliance lungs are...
easily stretched
54
Low compliance lungs...
require more force to stretch (more work)
55
Hysteresis
Different compliance for expiration and inspiration because of surfactant
56
What is the purpose of elasticity in the lungs?
The lungs are able to return to its original shape after the force stretching it has been removed
| Normal lungs are both compliant and elastic
56
What causes the differences in ventilation throughout an upright lung?
Gravity
57
How does gravity effect the apex and base of the lung?
Alveoli at the apex are larger and less compliant and receive less of each tidal volume breath than those at the base
58
What happens to the lungs in a patient with emphysema?
elastin fibers/lung tissue are destroyed
Lungs have high compliance and low elastance
poor recoil during expiration
hyper-inflated lung and "barrel-chest"
59
What effect do Restrictive Lung Diseases have on compliance?
They reduce compliance
More work must be expended to stretch a stiff lung
60
What are some possible causes of restrictive lung diseases/reduced lung compliance?
Inelastic scar tissue
insufficient surfactant production
61
Pulmonary elasticity is generated by...
Elastic fibers
Surface Tension
62
Why are elastic fibers important in respiratory system?
The natural tendency of these fibers to recoil facilitates passive expiration
63
What causes surface tension in the respiratory system? Why is it bad?
Surface tension on alveolar surfaces arise due to the strong attractive force that water has for itself
Surface tension tends to make alveoli collapse (especially smaller alveoli)
64
What is the purpose of surfactant?
To reduce surface tension around the alveoli
65
The chest wall and lung are in equilibrium at...
the FRC
66
Pulmonary circulation is a _ flow, _ pressure, _ resistance circuit
high flow
low pressure
low resistance
67
Where does RV CO go?
The lungs receive 100% of RV CO
68
Why is pressure so much lower in the pulmonary circulation vs. the systemic?
Only enough pressure is needed to lift blood to top of lung
Length of pulmonary blood vessels is shorter
RV doesn't have to pump as hard to overcome peripheral resistance
| This allows low pulmonic BP, low net hydrostatic BP
## Footnote
Work required of RV is much less than LV
69
Pulmonaries are _ compliant than the aorta and systemic arteries
much more compliant
70
The bronchial circulation supplies the _ and is part of the _ circulation
conducting portions of the lungs
systemic circulation
71
What happens to the deoxygenated blood found in the bronchial circulation?
It flows into the pulmonary veins along with freshly oxygenated blood from the alveoli
| It doesn't return to systemic circulation
72
What does the addition of deoxygenated blood from the bronchial circulation to pulmonary circulation do to blood O2 content?
Addition of deoxygenated blood slightly lowers the oxygen content of the blood before it reaches the left side of the heart
73
What do increases in CO or Pulmonary Arterial Pressure do to pulmonary vascular resistance (PVR) and Pulmonary blood flow? How?
pulmonary vascular resistance (PVR) decreases
pulmonary blood flow increases
due to recruitment and distension of capillaries
74
PVR is lowest at...
FRC
75
Why is PVR lowest at FRC?
extra-alveolar vessels are tethered to surrounding alveoli and compressed with low lung volumes
Alveolar vessels are located between alveoli and are compressed with high lung volumes
76
Hypoxia can alter pulmonary blood flow and PVR depending on...
whether it is regional or generalized
77
What occurs in Zone 1?
Pa < PA
Capillary collapses before it crosses alveolus
No flow
doesn't exist in normal lungs
| might exist with hemorrhage when BP and intravascular volume are low
78
What occurs in Zone 2?
Pa > PA > PV
Flow driven by difference between arterial and alveolar pressure
primary area of distension, recruitment of vessels during exercise
79
What occurs in Zone 3?
Pa > PV > PA
continuous forward flow through distended vessels
80
Pulmonary capillary fluid exchange is regulated by...
the same starling forces as systemic capillaries, but also has surface tension and alveolar pressure influences
81
The sum of partial pressures of a gas must be equal to...
total pressure
82
The partial pressure of a gas is equal to...
the fraction of gas in the gas mixture times the total pressure
83
What happens to inspired gas by the time it reaches the trachea?
It is fully saturated with water vapor, which exerts a pressure of 47 mmHg at body temp and dilutes the partial pressures of N2 and O2
84
What occurs because the conducting airways do not participate in gas exchange?
The partial pressures of O2, N2, and H2O vapor remain unchanged in the airways until the gas reaches the alveolus
85
# Equation
Total (Minute) Ventilation (VE) =
VE = Tidal Volume (VT) x respiratory rate (f)
| VT is more important than f when VE increases
86
At rest, total ventilation is approximately...
6,000 mL → 6L
87
# Define
Anatomical Dead Space
~ 150 mL
volume of air filled in conductin airways incapable of gas exchange with blood
88
# Equation
Alveolar Ventilation (VA)
VA = (Tidal Volume (VT) - VD (dead space)) x f
89
At rest, VA is approximately...
4200 mL → 4.2L
90
Breathing deeply and slowly...
| What effect does it have on VE and VA?
VE is unchanged
VA increases
91
Breathing shallowly and rapidly...
| What effect does it have on VE and VA?
VE is unchanged
VA decreases
92
The partial pressure of oxygen in the alveolus is given by...
The Alveolar Gas Equation
PAO2 = FIO2 (PB-PH2O) - (PACO2/R)
| At sea level, R = 0.8; PAO2 = 0.21(760-47)-(40/0.8) = 100
93
# Define
Respiratory Quotient
| What is it?
The ratio of CO2 produced to O2 consumed
94
What is the relationship between CO2 production and Alveolar Ventilation (VA)?
defined by the PCO2 equation
Inverse relationship between PACO2 and VA
## Footnote
alveolar PACO2 is tightly regulated to remain constant (normally)
95
The V/Q ratio is the crucial factor in determining...
alveolar/arterial PO2 and PCO2
96
Why does the apex of the upright lung have a high V/Q with a high PO2 and low PCO2?
alveoli in the apex are poorly ventilated and perfused but better ventilated than perfused
97
What happens to alveolar gas pressure when there is poor perfusion but good ventlation?
alveolar gas pressure is similar to mixed venous blood
PAO2 = 40, PACO2 = 45
98
# Define
A-a O2 gradient
| What does it do? How do you determine it?
Measures gas exchange efficiency across the alveolar - capillary membrane and can point to the cause of hypoxemia
Can be determined using the alveolar gas equation and arterial blood gasses
99
What is a normal A-a O2 gradient and what causes it?
≤ 20 mmHg
Due to normal V/Q mismatch
Shunting of bronchial and cornary blood into Thesbian veins back to the left side of the heart
100
Normal A-a O2 gradient can be predicted by...
(your age/4) + 4
| Increases with age
101
What are the 5 causes of hypoxemia?
Low inspired O2
Hypoventilation
Diffusion Limitation
Right-to-Left Shunt
Ventilation - Perfusion Mismatch
102
When would the A-a O2 gradient be normal during hypoxemia?
When hypoxemia is due to low inspired O2 and hypoventilation
103
What effect do diffusion defects, V/Q mismatching, and Right-to-Left Shunts have on the A-a O2 gradient?
the A-aO2 gradient is widened
104
Right-to-Left Shunt is the only cause of hypoxemia in which...
arterial PO2 fails to rise to the expected level when 100% O2 is administered
105
What two forms is O2 carried from the blood to the lungs to the tissues?
Physically dissolved in the blood
Chemically combined to Hb
106
What three forms is CO2 carried inthe blood?
Physically dissolved in blood
chemically bound to blood proteins (like carbamino compounds)
As bicarbonante
107
# Define
Fick's Law of Diffusion
the **diffusion of a gas** across a sheet of tissue is **directly** related to the **surface area** of the tissue, the **diffusion constant** of the specific gas, and the **partial pressure difference** of the gas on each of the tissues, and **inversely** related to tissue **thickness**
108
What is the relationship between O2 and CO2 loading and unloading?
They do not occur simultaneously but also facilitate each other
109
Which diffuses faster through the alveolar-capillary membrane, CO2 or O2?
CO2
110
How does O2 bind to the heme groups of the hemoglobin (Hb) molecule?
Quickley and reversibly
111
Which form of O2 is measured clinically in an arterial blood gas sample as the PaO2?
dissolved O2
| it maintains its molecular structure and gaseous state
112
What affect does CO2 have on hemoglobin and O2 binding?
CO2 can alter hemoglobins affinity for O2 and enhance the delivery of O2 to tissues and uptake of O2 in the lungs
113
Tissue hypoxia occurs when...
insufficient amounts of O2 are supplied to the tissue to carry out normal levels of aerobic metabolism
114
The major source of CO2 production is...
the mitochondria during aerobic cellular metabolism
115
What is the major pathway for HCO3- generation?
The reversible reaction of CO2 with H2O to form carbonic acid (H2CO3) with its subsequent dissociation to HCO3- and H+ catalyzed by carbonic anhydrase within red blood cells
116
What shape is the O2 dissociation curve?
S
117
What occurs in the plateau phase of the O2 dissociation curve?
increasing/decreasing PO2 have minimal effect on Hb saturation
118
What is important about the plateau phase of the O2 dissociation curve?
It allows adequate Hb saturation over a large range of PO2
119
What does ths steep portion of the O2 dissociation curve show?
That during O2 deprivation (Low PO2) O2 is readily released fromHb with only small changes in PO2
| This facilitates o2 diffusion to the tissue
120
Respiratory control is...
| What type?
automatic and voluntary
121
Ventilatory control is composed of...
sensors
controllers
effectors
122
The primary respiratory control center providing output to respiratory muscles.
Medullary Respiratory Center
123
# Define
Ventral Respiratory Group (VRG)
| What is it? Whats it do?
Contains the rhythm generator whose output drives respiration
Sets eupena
124
# Define
Dorsal Respiratory Group (DRG)
| What does it do?
Integrates peripheral sensory input (from chemoreceptors and stretch receptors) and modifies the rhythm generated by the VRG based on physiological need
125
What do the apneutic pontine center and the penumotaxic pontine center do to the medullary center?
They exert a fine tuning effect on the medullary center to ensure smooth breathing and smooth transitions between inspiration and expiraiton
126
# Define
Penumotaxic Center
| What does it do besides fine tuning?
Sends impulses to DRG to turn off inspiratory neurons
127
# Define
Apneustic Center
| What does it do besides fine tuning?
Prevents inspiratory neurons from being turned off
128
Which pontine center is dominate?
Pneumotaxic Center
129
What do Central Chemoreceptors do? How?
They respond to PCO2 by sensing H+ in the medullary interstitial fluid
## Footnote
Located near the ventral surface of the medulla
130
What do Peripheral Chemoreceptors do?
respond primarily to decreases in PO2, minimally to decreases in pH and increases in PCO2
Mechanism of detection results in inhibition of a K+ channel
## Footnote
only chemoreceptors that respond to changes in PO2
131
A decrease in PaO2 below 60 mmHG has what effect on peripheral chemoreceptors?
Increased firing rate of peripheral chemoreceptors
132
Pulmonary receptors on the lungs are sensitive to...
Lung volumes, mechanics, and irritants
133
# Define
Irritant Receptors
| Where are they? What is their function? What stimulates it?
Located between airway epithelial cells
Stimulated by particles, cold air, touch, or noxious substances (dust, smoke, etc.)
Protect by inducing cough and hypernea
134
What stimulates Juxtacapillary (J receptors) in the alveolar-capillary membrane?
distortion of the alveolar wall
| Lung congestion or edema
135
What is the most important regulator of ventilation at rest?
PCO2
