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611 Cards in this Set

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Describe Tidal Volume
It is the volume of inspired or expired with each normal breath
tidal volume
volume inspired or expired with each normal breath
What is the tidal volume?
The volume inspired or expired during normal breathing
What structures make up the conducting zone?
The nose, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles.
Volume inspired and expired with each breath
Tidal volume
definition of tidal volume
volume inspired with each normal breath
Describe Inspiratory Reserve Volume
-It is the volume that can be inspired over and above the tidal volume
-It is used during exercise
inspiratory reserve volume
volume inspired over and above TV ex. during exercise
What is the inspiratory reserve volume?
The volume that can be inspired beyond the tidal volume
What is the function of the conducting zone?
To warm, humidify, and filter the air before it reaches the critical gas exchange region.
The volume that can be inspired over and above the tidal volume
Inspiratory Reserve Volume
definition of IRV
volume that can be inspired over and above the tidal volume (with exercise)
Describe Expiratory Reserve Volume
It is the volume that can be expired after the expiration of a tidal volume
expiratory reserve volume
volume that can be expired after expiration of a tidal volume
What is the expiratory reserve volume?
The volume that can be expired after expiration of the tidal volume
How many divisions of the trachea/bronchi/bronchiole system are there?
There are 23 such divisions.
What lung capacity is used during exercise
IRV
definition of ERV
volume that can be expired after expiration of tidal volume
Describe Residual Volume
-It is the volume that remains in the lungs after a maximal expiration
-It cannot be measured by spirometry
residual volume
volume that remains in lungs after a maximal expiration
- cannot be measured by spirometry
What is the residual volume?
The volume that remains in the lungs after a maximal expiration
What effects does sympathetic innervation have on the conducting airway?
The walls of the conducting airways contains smooth muscle.
Sympathetic adrenergic neurons
activate β2 receptors on bronchial smooth muscle,
which leads to relaxation and dilation of the airways.

(and circulating epinephrine released from the adrenal medulla)
Volume the remains in the lungs after maximal expiration
Residual volume
definition of residual volume
volume that remains in the lungs after a maximal expiration... Cannot be measured by spirometry
Describe Anatomic Dead Space
-The volume of the conducting airways
-Approximately 150ml
anatomic dead space
volume of conducting pathways
approx. 150 ml
Can residual volume be measured by spirometry?
No
What effects does parasympathetic innervation have on the conducting airway?
Parasympathetic cholinergic neurons activate muscarinic receptors, which leads to contraction and constriction of the airways.
What are the two dead spaces of the lungs?
Anatomic and Physiologic
definition of anatomic dead space
volume of the conducting airways
Describe Physiologic Dead Space
-A functional measurement
-It is defined as the volume of the lungs that does not participate in gas exchange
-It is approximately equal to the anatomic dead space in normal lungs
-It may be greater than the anatomic dead space in lung diseases in which there are ventilation/perfusion (V/Q) defects
physiological dead space
- volume of lungs that does NOT participate in gas exchange
What is anatomic dead space?
The volume of the conducting airways,
Approximately 150 ml (or about 1 ml/lb of body weight)
What type of drugs are used to treat asthma?
β2-adrenergic agonists
(e.g. epinephrine, isoproterenol, albuterol),
which are used to dilate the airways.
Volume of conducting airways
Anatomic dead space
what is the "normal" anatomic dead space
approx. 150 ml
What is the equation to define physiologic dead space?
V_D=V_T* (P_ACO2-P_ECO2)/(P_ACO2)

V_D=Physiologic Dead Space
V_T= Tidal Volume
P_ACO2=P_CO2 of alveolar gas = P_CO2 of arterial blood
P_ECO2=P_CO2 of expired air
calculation of physiological dead space (Vd)
Vd = TV x (PaCO2 - PeCO2) / PaCO2
What is physiologic dead space?
It is the total dead space (the volume of the lungs that doesn't participate in gas exchange)
In normal lungs, physiologic dead space is approximately equal to anatomic dead space, but when there are V/Q defects, it is greater than anatomic dead space
What structures make up the respiratory zone?
Respiratory bronchioles, alveolar ducts, and the alveolar sacs.
Defined as the volume of the lungs that does not participate in gas exchange
Physiologic dead space
definition of physiologic dead space
volume of the lungs that does not participate in gas exchange
Describe Minute Ventilation
Minute Ventilation = TV*RR
minute ventilation
TV x breaths/min
Formula for physiologic dead space
Vd = Vt x [(PCO2 - PexpiredCO2) / PCO2]
Vt = tidal volume
Note that PCO2 is arterial/alveolar
What are transitional structures?
Respiratory bronchioles are transitional structures. Like the conducting airways, they have cilia and smooth muscle, but they are also considered part of the gas exchange region because alveoli occasionally bud off their walls.
Is a the functional measurement of dead space
Physiologic
what is the equation for physiologic dead space?
Vd = Vt * (PaCO2 - PeCO2)/PaCO2
Describe Alveolar Ventilation
Alveolar Ventilation = (TV-Dead Space)*RR
alveolar ventilation
alveolar ventilation = (TV - Vd) x breaths/min
Formula for minute ventilation
Minute ventilation = tidal volume x (breaths/min)
How many alveoli does each lung contain?
Approximately 300 million alveoli.
PHYSIOLOGIC DEAD SPACE

May be greater than the anatomic in:
Lung diseases with V/Q defects
what is the equation for alveolar ventilation?
alveolar ventilation = (Vt - Dead space) * breaths/min
Describe Inspiratory Capacity
The sum of Tidal Volume and IRV
inspiratory capacity
IRC = IRV + TV
Formula for alveolar ventilation
Alveolar ventilation = (tidal volume - dead space) x (breaths/min)
What is the role of type II pneumocytes?
Type II pneumocytes synthesize surfactant and have regenerative capacity for the type I and type II pneumocytes.
How do you calculate the physiologic dead space? ie Formula
Vd= Vt X (PaC02 - PeC02)/ PaC02
PaC02 = alveolar gas = PC02 of arterial
PeC02 = PC02 of expired air
definition of functional residual capacity
sum of ERV and RV;
volume remaining in lungs after Vt is expired
Describe Functional Residual Capacity
-The sum of ERV and Residual Volume
-The volume in the lungs after a tidal volume is expired
-Includes the residual volume so it cannot be measured by spirometer
functional residual capacity
FRC = ERV + RV

volume remaining after a tidal volume is expired --> cannot be measured
What is the inspiratory capacity?
Tidal volume + IRV
Which structures of the conducting zone contain cartilage?
Only the trachea and bronchi contain cartilage.
Tidal volume X Breaths/min
Minute ventilation
what is the normal FEV1?
80% of the FVC
Describe Vital Capacity/Forced Vital Capacity
-The sum of Tidal Volume, IRV, and ERV
-The volume of air that can be forcibly expired after a maximal inspiration
vital capacity or forced vital capacity
FVC = TV + IRV + ERV
What is the functional residual capacity?
ERV + RV
The volume remaining in the lungs after a tidal volume is expired
Where is pulmonary blood flow the highest? The lowest? Why?
Pulmonary blood flow is highest at the base of the lungs. It is lowest at the apex (top) of the lungs. This is due to gravitational effects.
(Tidal volume - Dead space) X Breaths/min
Alveolar ventilation
What happens to FEV1 in obstructive lung diseases?
FEV1 reduced more than FVC, so FEV1/FVC is decreased
Describe Total Lung Capacity
-The sum of all four lung volumes
-The volume in the lungs after a maximal inspiration
-Includes residual volume, so it cannot be measured by spirometry
total lung capacity
TLC = IRV + TV + ERV + RV

- cannot be measured by spirometry
Can FRC be measured by spirometry?
No, because it includes the residual volume
What is tidal volume (Vt)?
Normal, quiet breathing. It is approximately 500 mL and includes the volume of air that fills the alveoli plus the volume of air that fills the airways.
The sum of tidal volume and IRV
Inspiratory capacity
What happens to FEV1/FVC in restrictive lung disease?
e.g. fibrosis, both FEV1 and FVC are reduced and FEV1/FVC is normal or increased
Describe Forced Expiratory Volume (FEV1)
-FEV1 is the volume of air that can be expired in the first second of a forced maximal expiration
-Normally 80% of forced viral capacity
forced expiratory volume (FEV1)
volume of air that can be expired in the first second of forced maximal expiration
What is the vital capacity?
Also known as the forced vital capacity (FVC)
TV + IRV + ERV
This is the volume of air that can be forcibly expired after a maximal inspiration (total lung capacity except for the RV)
What is inspiratory reserve volume?
The additional volume that can be inspired above tidal volume. It is approximately 3000 mL.
Sum of ERV and residual volume
Functional Residual volume
what is the most important muscle for inspiration?
diaphragm
Describe how FEV1 is affected by obstructive lung disease
In obstructive lung disease, such as asthma, FEV1 is reduced more than FVC so that FEV1/FVC is decreased
normal value of FEV1/FVC
0.80
What is the total lung capacity?
The sum of all lung volumes; the volume in the lungs after a maximal inspiration
What is expiratory reserve volume?
The additional volume that can be expired below tidal volume, approximately 1200 mL.
Volume remaining in the lungs after a tidal volume expiration
FRC
what is hysteresis
the difference in the P-V curves of inspiration and expiration
Describe how FEV1 is affected by restrictive lung disease
In restrictive lung disease, such as fibrosis, both FEV1 and FVC are reduced and FEV1/FVC is either normal or is increased
obstructive lung disease, such as (1), the FEV1/FVC ratio is (2)
1 = asthma
2 = reduced
Can TLC be measured by spirometry?
No, because it includes RV
What is the volume of gas that remains in the lungs after a maximal forced expiration?
Residual volume, which is approximately 1200 mL. This cannot be measured by spirometry.
Sum of tidal volume, IRV, and ERV
Forced vital capacity
what happens to the FRC in a patient with emphysema and why?
FRC increases due to increased compliance of the lung.
The lung reduces its tendency to collapse
and "traps" the air that failed to be expired from a normal cycle.
What are the muscles of inspiration?
-Diaphragm
-External intercostals
-Accessory muscles
restrictive lung disease, such as (1), the FEV1/FVC ratio is either (2) or (3)
1 = fibrosis
2 = increased
3 = unchanged
Can VC be measured by spirometry?
Yes
What is the inspiratory capacity (IC)?
The inspiratory capacity is composed of the tidal volume plus the inspiratory reserve volume.
Approximately 3500 mL (500 + 3000)
The volume of air that can be forcibly expired after a maximal expiration
FVC
What happens to the FRC in a patient with fibrosis?
lung compliance is decreased,
and tendency of the lung to collapse is increased,
so FRC decreases
Describe the Diaphragm
-The most important muscle for inspiration
-When the diaphragm contracts, the abdominal contents are pushed downward and the ribs are lifted upward and outward, increasing the volume of the thoracic cavity
what is the most important muscle for inspiration?
diaphragm
What is the forced expiratory volume?
Abbreviated as FEV1
This is the volume of air that can be expired in the first second of a forced maximal expiration
What is the functionary residual capacity (FRC)?
FRC is the volume remaining in the lungs after a normal tidal volume is expired and can be thought of as the equilibrium volume of the lungs. It is composed of the expiratory reserve volume plus the residual volume.
Approximately 2400 mL (1200 + 1200)
The volume in the lungs after maximal inspiration
TLC
what is the effect of surfactant on alveoli?
it reduces the surface tension, and, therefore the opening pressure of the alveoli (Laplace's law). This results in a decreased tendency of alveoli to collapse
Describe the external intercostals and accessory muscles
-Not used for inspiration during normal quiet breathing
-Used during exercise and in respiratory distress
which muscles are used for inspiration during exercise/respiratory distress?
external intercostals
accessory abdominal muscles
What is the normal value for FEV1/FVC?
0.8 (80%)
What is the vital capacity?
Vital capacity is the volume that can be expired after maximal inspiration.
It is composed of the inspiratory capacity
plus the expiratory reserve volume.

Approximately 4700 mL (3500 + 1200)
Sum of all four lung volumes
TLC
where is surfactant produced?
type II alveolar cells
What are the muscles of expiration?
-Abdominal muscles
-Internal intercostal muscles
muscles in quiet expiration?
none --> passive recoil of lung tissue
What happens to FEV1/FVC in obstructive lung disease?
It decreases
What is the volume of total lung capacity?
Total lung capacity (TLC) includes all of the lung volumes (Vital capacity + residual volume).
It is approximately 5900 mL (4700 + 1200)
Lung capacities that can't be measured
FRC and TLC

B/C it includes residual volume, so cannot be measured by spirometry
what is the primary composition of surfactant?
dipalmitoyl phosphatidylcholine (DPPC)
Describe the muscles of expiration
-Expiration is normally passive
-Because the lung-chest wall system is elastic, it returns to its resting position after inspiration
-Expiratory muscles are used during exercise or when airway resistance is increased because of disease (e.g., asthma)
expiratory muscles used during exercise or when airway resistance is increased?
internal intercostals
abdominal muscles
What happens to FEV1/FVC in restrictive lung disease?
FEV1 and FVC are REDUCED

FEV1/FVC
Normal or increased
What is the anatomic dead space? What is its volume?
The anatomic dead space is the volume of the conducting airways, including the nose (and/or mouth), trachea, bronchi, and bronchioles. The volume is approximately 150 mL.
The volume of air that can be expired in the first second of forced maximal expiration
FEV1
what is the earliest time surfactant is produced in the fetus?
24 weeks
Describe the role of abdominal muscles in expiration
Compress the abdominal cavity, push the diaphragm up, and push air out of the lungs
compliance of lungs
describes distensibility of lungs and chest wall
- inversely related to elastance AND stiffness
- slope of pressure-volume curve

C = V/P
Is asthma an example of obstructive or restrictive lung disease?
Obstructive
What is the definition of physiologic dead space?
Physiologic dead space is the total volume of the lungs that does not participate in gas exchange.
FEV1 is normally ______% of forced vital capacity
80% of FVC
how does one tell if a fetus is producing mature levels of surfactant?
lecithin:sphingomyelin ratio > 2:1 in amniotic fluid
Describe the role of internal intercostal muscles in expiration
They pull the ribs downward and inward
transmural pressure = (1) pressure - (2) pressure
1 = alveolar pressure
2 = intrapleural pressure
Is fibrosis an example of obstructive or restrictive lung disease?
Restrictive
What is a reason the physiologic dead space can become larger than the anatomic dead space?
In normal persons, the physiologic dead space is nearly equal to the anatomic dead space. When the physiologic dead space is larger than the anatomic dead space, there may be a ventilation/perfusion defect.
In obstructive lung diseases, what happens to the FEV1 and FVC
FEV1 is reduced more than FVC so

FEV1/FVC is DECDREASED
according to Poiseuille's law, what is the relationship between resistance of an airway and the radius?
R is inversely proportional to the r^4
Describe compliance
-Describe the distensibility of the lungs and chest
-Is inversely related to elastance, which depends on the amount of elastic tissue
-Inversely related to stiffness
-The slow of the PV curve
-The change in volume for a given change in pressure. Pressure refers to the transmural or transpulmonary pressure (the pressure difference across pulmonary structures)
when intrapleural pressure is negative, the lungs (1) and volume (2)

when intrapleural pressure is positive, the lungs (3) and volume (4)
1 = expand
2 = volume increases
3 = collapse
4 = volume decreases
What are the muscles that participate in inspiration?
Diaphragm
External intercostals and accessory muscles -- only used during exercise and respiratory distress
What is the equation to calculate the volume of physiologic dead space?
Vd = Vt*(Paco2 - Peco2)/Paco2

Volume of the physiologic dead space is the tidal volume multiplied by a fraction that represents the dilution of alveolar Pco2 by dead space air.
In restrictive lung disease, what happens to FEV1 and FVC?
FEV1 and FVC are reduced so

FEV1/FVC are normal or increased
where is the major site of airway resistance?
medium-sized bronchi
What equation describes compliance?
C=V/P

C=Compliance
V=Volume
P=Pressure
hysteresis
difference between inspiration and expiration lung pressure-volume curves
What is the role of the diaphragm in inspiration?
The most important inspiratory muscle
When the diaphragm contracts, the abdominal contents move downward and the ribs move upward and outward
This increases the volume of the thoracic cavity
What is the difference between minute ventilation and alveolar ventilation rates?
Minute ventilation is the total rate of air movement into and out of the lungs. Alveolar ventilation rate is the same, but it corrects for the physiologic dead space.

Minute ventilation = Vt x Breaths/min

Alveolar ventilation Va = (Vt-Vd) x Breaths/min

Vt = tidal volume (mL)
Vd = physiologic dead space (mL)
Name a common form of obstructive lung disease?
Asthma, can't get air out
What class (and example) of drug causes dilation of airways?
Beta-2 agonists (e.g. isoproterenol)
Describe the compliance of the lungs
-Transmural pressure is alveolar pressure minus intrapleural pressure
-When the pressure outside of the lungs (ie intrapleural pressure) is negative, the lungs expand and lung volume increases
-When the pressure outside of the lungs is positive, the lungs collapse and lung volume decreases
-Inflation of the lungs (inspiration) follows a different curve than deflation of the lungs (expiration) (called hysteresis)
-In the middle range of pressures, compliance is greatest and the lungs are most distensible
-At high expanding pressures, complaince is lowest and the lungs are lead distensible ad the curve flattens
when is lung compliance the highest?
middle range of pressure on curve
Is normal quiet expiration active or passive?
Passive
Results from the elastic recoil of the inspiratory muscles
What is forced vital capacity (FVC)?
Forced vital capacity is the total volume of air that can be forcibly expired after a maximal inspiration
Name a common form of restrictive lung disease?
Fibrosis, can't get air in
at what point in the breathing cycle is alveolar pressure equal to 0?
at FRC, just before inspiration.
Describe the compliance of the lung-chest wall system
Less than that of the lungs alone or the chest wall alone
compliance of the lung-chest wall system is (1) than that of lungs or chest (2)
1 = less
2 = alone
What are the expiratory muscles?
Abdominal muscles -- compress the abdominal cavity and push the diaphragm upward
Internal intercostals -- pull the ribs down
Note that these muscles only participate during exercise or when airway resistance is increased due to lung disease
What is FEV1?
FEV1 is the volume of air that can be forcibly expired in the first second.
In restrictive lung diseases name what happens to each: increase or decrease:
TLC
Residual Volume
FEV1
FVC
FEV1/FVC
Pa02
A-a gradient
TLC= decreased
Residual volume = decreased
FEV1= decreased
FEV1/FVC = Normal to increased
Pa02 = Decreased
A-a gradient = Increased
how does one measure intrapleural pressure?
with a balloon catheter in the esophagus
Describe the complaince of the lung-chest wall system at rest
-Lung volume is at FRC and the pressure in the airway and lungs is equal to atmispheric pressure
-Under these equilibrium conditions, there is a collapsing force on the lungs and an expanding force on the chest wallAt FRC, these two forces are equal and opposite and therefore the combined lung-chest wall system neither wants to collapse nor expand
pneumothorax
lungs collapse
chest wall springs forward
(natural tendencies)
What is respiratory compliance?
Describes the distensibility of the lungs and chest wall
It is inversely related to elasticity (that is, as elasticity increases, compliance decreases)
Inversely related to stiffness
Compliance is the change in volume or a given change in pressure. The higher the compliance, the greater the change in volume for that pressure value
What is the value of FEV1/FVC in a normal person?
FEV1/FVC = ~0.8, meaning that 80% of the vital capacity can be forcibly expired in the first second.
In obstructive lung diseases name what happens to each: increase or decrease
TLC
Residual Volume
FEV1
FVC
FEV1/FVC
Pa02
A-a gradient
TLC= increased
Residual volume = increased
FEV1= decreased
FEV1/FVC = decreased
Pa02 = Decreased
A-a gradient = Increased
why do patients with COPD expire through pursed lips?
during forced expiration a positive intrapleural pressure is created that collapses the airways. Pursing the lips creates enough back-pressure to maintain airway patency
Describe the intrapleural pressure at rest
Negative due to the lungs collapsing in and the chest expanding out
emphysema
- lung compliance is (1) and tendency of lungs to collapse is (2); tendency of lungs to collapse is (3) than tendency of chest wall to expand resulting in (4)
1 = increased
2 = decreased
3 = less
4 = barrel-shaped chest
Formula for respiratory compliance
C = V/P
V = volume
P = transmural pressure
What is the FEV1/FVC in a patient with asthma?
In obstructive lung diseases like asthma, both FVC and FEV1 are decreased, but FEV1 is decreased more. Thus, FEV1/FVC is decreased.
An increase in A-a gradient means
Hypoxemia of pulmonary origin
What are general characteristics of COPD?
obstructive disease with increased lung compliance. FEV1 is markedly decreased, FVC is decreased, FEV1/FVC is decreased and FRC is increased
Describe a pneumothorax
-Air is introduced into the intrapleural space
-The intrapleural pressure becomes equal to atmospheric pressure
-The lungs will collapse (their natural tendency) and the chest wall will spring outward (its natural tendency)
in fibrosis, lung compliance is (1) and tendency of lungs to collapse is (2); the tendency of lungs to collapse is (3) than tendency of chest wall to expand
1 = decreased 3
2 = increased
3 = greater
What is the transmural pressure?
Alveolar pressure - intrapleural pressure
What is the FEV1/FVC in a patient with fibrosis?
In patients with restrictive lung diseases such as fibrosis, both FVC and FEV1 are decreased, but they decrease the same or FEV1 is decreased less than FVC. Thus, in fibrosis FEV1/FVC is the same or increased.
Hypoxemia due to extrapulmonary causes has a _____ A-a gradient
Normal
What are characteristics of a "pink puffer"
primarily emphysema, have mild hypoxemia, normocapnia.
Describe the changes in lung compliance due to emphysema
-Lung compliance is increased then the tendency of the lungs to collapse is decreased
-At the original FRC, the tendency of the lungs to collapse is less than the tendency of the chest wall to expand
-The lung-chest wall system will seek a new higher FRC so that the two opposing forces can be balances
-The patient's chest becomes barrel-shaped, reflecting this higher volume
collapsing pressure (surface tension)
P = 2 T / r

T = surface tension
r = radius
What is intrapleural pressure?
The pressure outside of the lungs, inside the thoracic cavity
What is the most important muscle for inspiration?
What muscles are used for inspiration during exercise?
The diaphragm.
During exercise, the external intercostal muscles and accessory muscles (scalene muscles and sternomastoids)
Laplace's law states that larger alveoli are
Less likely to collapse b/c collapsing pressure is directly proportional to surface tension and inversely proportional to size
what are characteristics of 'blue bloaters?'
primarily bronchitis, have severe hypoxemia with cyanosis, do not maintain alveolar ventilation --> hypercapnia; right ventricular failure and systemic edema. must have productive cough for >3 consecutive months in >= 2 years
Describe the changes in lung compliance due to fibrosis
-Lung complaince is decreased and the tendency of the lungs to collapse is increased
-At the original FRC the tendency of the lungs to collapse is greater than the tendency of the chest wall to expand
-The lung-chest wall system will seek a new, lower FRC so that the two opposing forces can be balanced
in absent of surfactant, small alveoli have a tendency to (1) known as (2)
1 = collapse
2 = atelectasis
How does intrapleural pressure determine lung inflation and deflation?
When the IPP is negative, the lungs expand, causing lung volume to increase
When the IPP is positive, the lungs collapse and lung volume decreases
What muscles are used for expiration? During exercise?
Expiration is normally a passive process.

During exercise (or disorders like asthma), the muscles of expiration include abdominal muscles, internal intercostal muscles, and internal and external obliques.
Small alveoli are more likely to collapse b/c
of increased pressure and tendency to collapse
what are characteristics of pulmonary fibrosis?
restrictive disease with decreased lung compliance. inspiration is impaired; decrease in ALL lung volumes, FEV1/FVC is increased
what is the equation to correct for water vapor and PO2 in humidified tracheal air?
P(total) = (760mmHg - 47mmHg) * 0.21 = 150 mmHg P(O2)
Describe the surface tension of the alveoli
-Results from the attractive forces between liquid molecules lining the alveoli
-Creates a collapsing pressure that is directly proportional to surface tension and inversely proportional to alveolar radius
surfactant
- roles (2)
- synthesized where? (1)
- made of (3)?
2 = decreases surface tension, increases compliance
1 = type II alveolar cells
3 = DPPC dipalmitoyl phosphatidylcholine
What is hysteresis?
When the volume-pressure relationship of the lungs is different for inspiration and expiration
What happens during a pneumothorax?
Normally, intrapleural pressure is -5 cm H2O. When a sharp object punctures the intrapleural space, air is introduced into the space, and intrapleural pressure suddenly becomes equal to atmospheric pressure.
- There is no longer a negative intrapleural pressure to hold the lungs open, and the lungs collapse.
- There is no longer a negative intrapleural pressure to keep the chest wall from expanding, and the chest wall springs out.
Surfactant is synthesized in
Type II pneumocytes
what is the normal P(O2) in normal humidified tracheal air?
150 mmHg
Describe the surface tension of large alveoli vs small alveoli
Large alveoli (large radius) have a low collapsing pressure and are easy to keep open

Small alveoli have high collapsing pressures and are more difficult to keep open

In the absence of surfactant, the small alveoli have a tendency to collapse
Ratio of what reflects mature lungs?
lecithin/sphingomyelin ratio of 2:1 in amniotic fluid
At what pressures is compliance the greatest?
Middle range of pressures
High compliance = greatest distensibility
At high pressures, compliance is low and the lungs are only slightly distensible
What occurs when the volume is FRC?
At FRC, because they are elastic structures, the lungs "want" to collapse and the chest wall "wants" to expand. At FRC, the collapsing force on the lungs is exactly equal to the expanding force on the chest wall. Thus, the combined system neither has a tendency to collapse nor to expand.
Surfactant consist of
DPPC, dipalmitoyl phosphatidycholine
what limits gas exchange in pulmonary capillaries normally?
perfusion --> partial pressures of gases equilibrate early in the capillary
What is atelectasis?
-Lack of gas exchange within alveoli, due to alveolar collapse or fluid consolidation
-In the absence of surfactant, the small alveoli have a tendency to collapse
neonatal respiratory distress syndrome
due to lack of surfactant
lungs collapse, difficulty reinflating and hypoxia
How does the compliance of the chest-wall system compare to the compliance of the lungs or chest wall along?
It is greater
What occurs when the volume is less than FRC?
When the volume in the system is less than FRC (i.e., the subject makes a forced expiration), there is less volume in the lungs and collapsing (elastic) force of the lungs is smaller. The expanding force on the chest wall is greater, however, and the combined system "wants" to expand.
How do you know if a neonates lungs are mature?
Lecithin:sphingomyelin ratio > 2:1
what limits gas exchange in the pulmonary capillaries under strenuous exercise?
diffusion --> perfusion is increased to a point that maximum gas exchange is achieved limited by the rate at which the gases can cross the alveolar membranes
Describe surfactant
-Lines the alveoli
-Reduces surface tension
-Syntehsized by type II alveolar cells and consists primarily of phospholipid dipalmitoyl phosphatidylcholine (DPPC)
formula for airflow
Q = P / R
Describe the state of pressure and lung volume at rest
Lung volume is at FRC
Pressure in the airways and lungs is equal to atmospheric pressure (0 mmHg)
There is a collapsing force on the lungs and an expanding force on the chest wall
These forces are equal and opposite, so the chest-wall system does not collapse or expand
These two opposing forces generate negative intrapleural pressure
What occurs when the volume is greater than FRC?
When the volume in the system is greater than FRC (i.e., the subject inspires from the spirometer), there is more volume in the lungs and collapsing (elastic) force of the lungs is greater. The expanding force of the chest wall is smaller, and the combined system "wants" to collapse.
The major site of airway resistance in the lungs is
the medium-sized bronchi
what limits gas exchange in fibrosis?
thickness of membrane increases
Describe how surfactant reduces surfact tension
-Disrupts the intermolecular forces between liquid molecules
-This reduction in surface tension prevents small alveoli from collapsing and increases compliance
poiseuilles law for resistance
R = 8 n l / (pi) r^4
What happens during pneumothorax?
Air is introduced into the intrapleural space
This causes the intrapleural pressure to equal atmospheric pressure
The lungs follow their natural tendency to collapse
The chest wall follows its natural tendency to expand
What happens to compliance in patients with emphysema?
Emphysema is associated with loss of elastic fibers in the lungs. As a result, the compliance of the lungs increases. As a result, at a given volume, the collapsing (elastic recoil) force on the lungs is decreased.
Why don't the smallest airways offer the highest resistance based on Poiseuille's law?
The smallest airways are connected in parallel
what limits gas exchange in emphysema?
surface area is decreased
Describe surfactant synthesis in the fetus
-Variable
-Surfactant may be present as early as gestational week 24 and is almost always present by gestational week 35
-Lecithin:sphingomyelin ratio greater than 2:1 in amniotic fluid reflects mature levels of surfactant
where is the major site of airway resistance?
medium bronchi
What happens to lung compliance in a patient with emphysema?
Lung compliance increases because the alveoli are eaten away
The tendency of the lungs to collapse is decreased
A new, higher FRC is established because air can't escape
The chest becomes barrel-shaped
Why do patients with emphysema have a barrel-shaped chest?
Because of the decreased tendency to collapse, the combined lung and chest-wall system seeks a new higher FRC, where the two opposing forces (expansion and collapse) can be balanced. A patient with emphysema breathes at higher lung volumes, and will have a barrel-shaped chest.
How do the lungs change airway resistance?
contraction or relaxation of bronchial smooth muscle
what molecule causes off-loading of O2 from Hb in tissues?
2,3-diphosphoglycerate
Describe neonatal respiratory distress syndrome
-Can occur in premature infants because of lack of surfactant
-Infant exhibits atelectasis (lungs collapse), difficulty reinflating the lungs (as a result of decreased compliance), and hypoxemia (as a result of decreased V/Q)
What causes constriction of airways? (3)
1 = PNS
2 = irritants
3 = slow reacting substance of anaphylaxis (asthma)
What happens to lung compliance in a patient with fibrosis?
Lung compliance decreases
The tendency of the lungs to collapse is increased
A new, lower FRC is established because the tendency of the lungs to collapse exceeds the tendency of the chest wall to expand
What happens to compliance in patients with fibrosis?
Fibrosis is associated with stiffening of lung tissues and decreased compliance. The lung and chest-wall system will seek a new lower FRC.
What constricts the airways, decrease the resistance, and increase the resistance to flow?
Parasympathetic stimulation
Irritants
Slow-reacting substance of anaphylaxis ASTHMA
what is the composition of fetal Hb and how are its properties different from adult Hb?
composition: 2 alpha and 2 gamma chains; this causes a left-shift in the saturation curve resulting in increased affinity for O2 due to decreased affinity to 2,3-DPG
What causes dilation of airways? (2)
1 = SNS stimulation
2 = SNS agonists i.e. isoproterenol that act on B2 AR
What causes surface tension in the alveoli?
Attractive forces between liquid molecules lining the alveoli
This creates a collapsing pressure that is directly proportional to surface tension and inversely proportional to alveolar radius
What does the law of Laplace state?
The law of Laplace states that the pressure tending to collapse an alveolus is directly proportional to the surface tension generated by the molecules of liquid lining the alveolus and inversely proportional to alveolar radius.
What increases the radius, and decreases the resistance to airflow?
Sympathetic stimulation
Sympathetic agonist
what is the equation for O2 content of blood?
O2 content = (O2-binding capacity * % saturation) + dissolved O2
asthma is an (1) disease, with (2) FVC and (3) FEV1 and (4) FEV1/FVC ratio; functional residual capacity is (5)
1 = obstructive disease
2 = decreased
3 = decreased
4 = decreased
5 = increased
Laplace's Law
P = 2T/r
P = collapsing pressure (pressure required to keep alveolus open)
T = surface tension
R - radius of alveolus
What is the formula for collapsing pressure (Law of Laplace)?
P = 2T/r

P = Collapsing pressure on alveolus (dynes/cm^2)
or Pressure required to keep alveolus open
T = Surface tension (dynes/cm)
r = Radius of the alveolus (cm)
MOA for sympathetic dilation of airways
B2 receptor activation
which binding site of Hb has the highest affinity for O2? Why is this important?
the fourth binding site --> it allows maximal loading of O2 in the lungs and unloading in the tissues
COPD is an (1) disease with (2) lung compliance; characterized by (3) FCV, (4) FEV1 and thus, (5) FEV1/FVC ratio
1 = obstructive disease
2 = increased lung compliance
3 = decreased
4 = decreased
5 = decreased
How does collapsing pressure vary according to alveolar radius?
Large alveoli (large radius) have low collapsing pressures, so it is easy to keep them patent
Small alveoli (small radius) have high collapsing pressures, and are easier to collapse
In simple words, describe the law of Laplace.
The tendency for an alveolus to collapse increases as the radius decreases.
Isoproternol MOA on the lungs
dilates via B2 stimulation
What causes a right-shift in the Hb-O2 dissociation curve?
increased P(CO2)
decreased pH
increased temperature
increased 2,3-DPG
What is the most important constituent in surfactant?
Dipalmitoyl phosphatidylcholine (DPPC).
fibrosis is a (1) disease with (2) lung compliance characterized by a decrease in (3); FEV1/FVC ratio is (4)
1 = restrictive disease
2 = decreased lung compliance
3 = decrease in all lung volumes
4 = increased (normal)
What is atelectasis?
Alveolar collapse
Asthma is what type of disease?
Obstructive lung disease
What causes a left-shift in the Hb-O2 dissociation curve?
decreased P(CO2)
increased pH
decreased temperature
decreased 2,3-DPG
pink puffers
emphysema
- mild hypoxemia
- maintain alveolar ventilation = normocapnia
What happens if there is no surfactant?
Small alveoli have a tendency to collapse (atelectasis)
What occurs in neonatal respiratory distress syndrome?
Surfactant is lacking. Infants born before gestational week 24 will never have surfactant, and infants born between weeks 24 and 35 will have uncertain surfactant status. Thus, without surfactant, small alveoli have increased surface tension and increased pressures, and will collapse. Lung compliance will be decreased and the work of inflating the lungs during breathing will be increased.
What are the effects of Asthma on FEV and FVC?
Decreased FEV1
Decreased FVC
Decreased FEV1/FVC ratio
In asthma, air should have been expired is known as ______ leading to______
Air trapping, a barrel shaped chest
Increased FRC
what is normal pulmonary arterial pressure?
15 mmHg
blue bloaters
bronchitis
- severe hypoxemia with cyanosis
- do not maintain alveolar ventilation = hypercapnia
- right ventricular failure and systemic edema
How does surfactant reduce alveolar surface tension?
Disrupts the intermolecular forces between liquid molecules
This prevents small alveoli from collapsing and increases compliance
What is the formula for pulmonary vascular resistance (PVR)?
PVR = P(pulm.artery) - P(L.atrium)/ Cardiac Output

P(pulm.artery) = pressure in pulmonary artery
P(L.atrium) = pulmonary wedge pressure
Who are pink puffers
Emphysema
Describe the pressure and perfusion relationships in Zone 1 alveoli
alveolar pressure > arterial pressure > venous pressure
Q is greatly decreased, V is decreased and V/Q is increased
blood flow is lowest
Dalton's law of partial pressure
PP = total pressure x fractional conc.
How is surfactant produced?
It is made by type II alveolar cells
What does Poiseuille's law sate?
Resistance is inversely proportional to the radius of an airway (to the fourth power), and directly proportional to the length of the airway and viscosity of inspired air.
Why are emphysema people called pink puffers?
They have mild hypoxemia with normal ventilation, normal pCO2
(normocapnia)
Describe the pressure and perfusion relationships in Zone 2 alveoli
arterial pressure > alveolar pressure > venous pressure
Q, V and V/Q are "normal"
gas transfer is maximized
physiological shunt
2% of systemic cardiac output bypasses pulmonary circulation making the PO2 of arterial blood slightly lower than that of alveolar air
What is surfactant made of?
Comprised mostly of the phospholipid dipalmitoyl phosphatidylcholine (DPPC)
What is Poiseuille's law?
R = 8ηl/πr^4

R = Resistance
η = Viscosity of inspired air
l = Length of the airway
r = Radius of the airway
Who are blue bloaters?
Bronchitis
Describe the pressure and perfusion relationships in Zone 3 alveoli
arterial pressure > venous pressure > alveolar pressure
Q is greatly increased, V is increased and V/Q is reduced
blood flow is highest
perfusion limited exchange
- demonstrated by (1)
- gas equilibrates (2) along length of pulmonary capillary
- diffusion of gas can only be increased in blood flow (3)
1 = N20, O2 under normal conditions, CO2
2 = early
3 = increases
When during fetal development is surfactant produced?
This is somewhat variable
Can be made as early as 24 weeks
Almost always present by 35 weeks
A lecithin:sphingomyelin ratio greater than 2:1 in the amniotic fluid generally reflects mature levels of surfactant
What are the sites of highest airway resistance?
The medium-sized bronchi. Because of the parallel arrangement of the smallest airways, the total resistance is less than the individual resistance.
Why are people with Bronchitis called Blue Bloaters?
B/c they have severe hypoxemia w/ Cyanosis
No alveolar ventilation, hypercapnia, increased pCO2
Right vent. Failure and systemic edema
what is the effect of hypoxia on pulmonary vasculature?
it causes vasoconstriction in order to redirect flow away from poorly ventilated hypoxic regions of the lung to those that are better ventilated
diffusion limited exchange
- demonstrated by (1)
- gas (2) equilibrates along pulmonary capillary
1 = CO, O2 under strenous exercise
2= does not equilbrate
What is neonatal respiratory distress syndrome?
Occurs in premature infants who have not manufactured sufficient amounts of surfactant
These infants have atelectasis (collapsed lungs), difficulty reinflating the lungs because of decreased compliance, and hypoxemia (decreased V/Q)
What factors constrict the airways, decrease the radius, and increase the resistance to flow?
Parasympathetic stimulation, irritants, and the slow-reacting substance of anaphylaxis (asthma)
What is COPD?
A combination of bronchitis and emphysema
Where are right-to left shunts seen and what is the result?
Tetralogy of Fallot; result in a decrease in arterial P(O2)
subunits in fetal hemoglobin
a2 y2
What drives airflow?
The pressure difference between the mouth or nose and the alveoli
What factors relax the airways, increase the radius, and decrease the resistance to airflow?
Sympathetic stimulation and sympathetic agonists (isoproterenol) dilate the airways via β2 receptors.
What type of lung disease is COPD
Obstructive lung disease with increased lung compliance and impaired expiration
where are left-to-right shunts seen and what is the result?
paten ductus arteriosus or traumatic injury; do not result in decrease in arterial P(O2). most are asymptomatic.
fetal Hb has a (1) affinity for O2 than adult Hb bc 2,3BPG binds (2)
1 = higher
2 = less tightly
How is airflow related to airway resistance?
Inversely proportional
The higher the airway resistance, the lower the airflow
What is the difference in intrapleural pressure when expiration (passive) and forced expiration?
In passive expiration, intrapleural pressure (which was -6 cm H2O during inspiration) returns to its resting value (-3). During a forced expiration, intrapleural pressure actually becomes positive. This positive intrapleural pressure compresses the airways and makes expiration more difficult.
What happens to lung compliance in COPD?
It's increased
What is the normal V/Q ratio?
0.8
methemoglobin
Fe3+
does not bind O2
Equation for airflow
Q = delta P / R
Q = airflow
delta P = pressure gradient
R = resistance
What is asthma? What is it characterized by?
Asthma is an obstructive disease in which expiration is impaired.
Characterized by:
Decreased FVC
Decreased FEV1
Decreased FEV1/FVC

Air that should have been expired is not, leading to air trapping and increased FRC.
Which iron state binds oxygen?
FE2+
What are the partial pressures of CO2 and O2 in pulmonary capillaries of obstructed airways?
in a physiologic shunt, Pa values approach venous values: Pa(O2) = 40 mmHg and Pa(CO2) = 46 mmHg
What is COPD? What is it characterized by?
COPD is a combination of chronic bronchitis and emphysema. It is an obstructive disease with increased lung compliance in which expiration is impaired.

Characterized by:
Decreased FVC, FEV1
Decreased FEV1/FVC

Air that should have been expired is not, leading to air trapping, increased FRC, and a barrel-shaped chest.
O2 binding capacity of blood
max amount of O2 that can be bound to Hb

- depends on Hb conc.
Formula for airway resistance
R = (8nl) / (pi x r^4)
n = viscosity
l = length of airway
r = radius
What is the name for FE3+?
Methemoglobin
What are the partial pressures of CO2 and O2 in alveoli of obstructed pulmonary capillaries?
in physiologic dead space, the partial pressures of O2 and CO2 approach that of humid air: P(O2) = 150 mmHg and P(CO2) = 0 mmHg
What are "pink puffers"? "Blue bloaters"?
"Pink puffers" (primarily emphysema) have mild hypoxemia and normocapnia (normal PCO2).

"Blue bloaters" (primarily bronchitis) have severe hypoxemia with cyanosis and hypercapnia (increased PCO2). They have right ventricular failure and systemic edema.
SHIFT to the RIGHT of Hb-O2 curve
increased PCO2
increased 2, 3 BPG
decreased pH
increased temp
What is the relationship between airway resistance and radius of the airway?
Resistance is inversely proportional to the fourth power of the airway
What is the normal structure for adult hemoglobin?
α2β2
Where is the medullary respiratory center located?
in the reticular formation
LEFT SHIFT of Hb-O2 curve
HbF
CO

---> affinity of Hb for O2 is increased
What is the major site of airway resistance?
Medium-sized bronchi
What condition leads to a decrease in all lung volumes, decreased lung compliance in which inspiration is impaired, and an increased FEV1/FVC?
Fibrosis (restrictive disease).
What is the structure of fetal hemoglobin?
α2γ2
What is responsible for inspiration and generates basic rhythm of breathing?
Dorsal respiratory group
CO (1) the O2 content of the blood
decreases
What factors cause the bronchial smooth muscle to contract?
Parasympathetic stimulation
Irritants
Slow-reacting substance of anaphylaxis (asthma)
What are the values of partial pressure of O2 and CO2 for alveolar air, systemic arterial blood, and mixed venous blood?
Alveolar air
PO2 = 100 mmHg
PCO2 = 40

Systemic Arterial Blood
PO2 = slighty <100 (due to physiologic shunt)
PCO2 = 40

Mixed Venous Blood
PO2 = 40 mmHg
PCO2 = 46
Why does a left shift occur with fetal hemoglobin?
Tighter O2 affinity
Less 2,3 DPG affinity
From where does the input to the dorsal respiratory group come?
vagus (chemoreceptors and mechanoreceptors) and glossopharyngeal (chemoreceptors) nerves
hypoxemia
decrease in arterial PO2
What factors cause the bronchial smooth muscle to relax?
Sympathetic stimulation
Sympathetic agonists
These things use beta 2 receptors
In hemoglobin, what is the heme moiety?
Iron-containing porphyrin. The iron is in the ferrous state (Fe2+), which binds O2. Iron in the ferric state (Fe3+) does not bind O2.

Mnemonic: Ferris (Ferrous) was with 2 (Fe2+) people on his adventure.
What does %saturation measure?
Amount of O2 bound to hemoglobin
Where does the output of the dorsal respiratory group go?
along the phrenic nerve to the diaphragm
A-a gradient
- used to compare causes hypoxemia
A-a gradient = alveolar PO2 - arterial PO2
How does isoproterenol affect bronchodilation?
It is a sympathetic agonist, and this causes the bronchioles to dilate
What is hemoglobin F composed of?
In fetal hemoglobin, the β chains are replaced by γ chains. Thus, fetal hemoglobin is α2γ2.
O2 content is a measure of
Total O2 in blood: bound to heme and dissolved O2
What is the function of the ventral respiratory group and when is it activated?
function is expiration, activated during exercise
alveolar PO2
alveolar PO2 = inspired Po2 - alveolar PCO2 / R
How does lung volume contribute to airway resistance?
Lung tissue exerts radial traction upon the airways
High lung volumes are associated with greater traction and decreased resistance
Low lung volumes exert less traction, and there can be resistance to the point of airway collapse
At which values of PO2 is hemoglobin 100% saturated?
75% saturated? 50% saturated?
100% saturated: PO2 = 100 mmHg
75% saturated: PO2 = 75 mmHg
50% saturated: PO2 = 50 mmHg
What is the formuale for O2 content?
= (O2-binding capacity x %sat) + dissolved O2
What and where is the apneustic center?
stimulates inspiration; located in lower pons
What does a shift to the right in the hemoglobin-O2 dissociation curve indicate? What causes this?
Shifts to the right occur when the affinity of hemoglobin for O2 is decreased.

Causes:
Increases in PCO2
Decreases in pH
Increases in temperature (e.g. during exercise)
Increases in 2,3-DPG concentration (e.g. living at high altitudes)
normal A-a gradient
is less than 10 mmHg
How do the density and viscosity of an inspired gas affect airflow?
They change the resistance to airflow
During deep-sea diving, air density increases and resistance increases
Low-density gases such as helium reduce airflow resistance
What is on the x and y axis of Hemoglobin curve?
X axis = PO2
Y axis = % sat.
Where/what is the pneumotaxic center?
located in the upper pons and inhibits inspiration
Increased A-a gradient
- if O2 does not equilibriate between alveolar and arterial blood

- diffusion defect
- V/Q defect
- right to left shunt
What are the thoracic pressures at rest, before inspiration begins?
Alveolar pressure = atmospheric pressure = 0
Intrapleural pressure is negative due to the opposing forces of the lungs trying to collapse and the chest wall trying to expand
What does a shift to the left in the hemoglobin-O2 dissociation curve indicate?
What conditions cause this?
Shifts to the left occur when the affinity of hemoglobin for O2 is increased.

Causes:
Decreased PCO2
Increased pH
Decreased temperature
Decreased 2,3-DPG concentration
What is the pO2 of mixed venous blood?
40 mm Hg
where are the central chemoreceptors for breathing and what stimuli increase breathing rate?
medulla; decreased pH (or increased CO2 which combines with water to make H+) of CSF
what is the major form of CO2 in blood?
HCO3

- small amounts of CO2 dissolved and as carbaminohemoglobin
Equation for airflow
Q = delta P / R
Q = airflow
delta P = pressure gradient
R = resistance
What is 2,3-DPG? When does 2,3-DPG production increase?
2,3-diphosphoglycerate (2,3-DPG) is a byproduct of glycolysis in red blood cells. 2,3-DPG binds to the β chains of deoxyhemoglobin and reduces their affinity for O2.

2,3-DPG production increases under hypoxic conditions (i.e. high altitude).
At pO2 of 25 mm Hg, what is the % Hg sat. ?
50%, aka P50, 2 out 4 heme groups are saturated
where are the peripheral chemoreceptors for breathing and what stimuli increase breathing rate?
carotid and aortic bodies; decreased P(O2) (if <60mmHg), decreased pH, increased P(CO2)
main buffer of H+ in RBCs?
deoxyhemoglobin
Formula for airway resistance
R = (8nl) / (pi x r^4)
n = viscosity
l = length of airway
r = radius
Does HbF cause the curve to shift to the left? What about the binding of CO to hemoglobin?
HbF: left shift.
HbF does not bind 2,3-DPG as strongly as adult hemoglobin, which results in increased affinity of HbF for O2.

Carbon monoxide (CO) poisoning: left shift
Why is there a sigmoid shaped curve for Hg-O2 dissociation curve?
Positive cooperativity, B/c of a change in affinity for hemoglobin with each O2 added.
What are J receptors and what do they affect?
located in alveolar walls, close to capillaries. they are activated by engorgement of pulmonary capillaries (as in left heart failure) to cause rapid shallow breathing
pulmonary circulation vs. systemic circulation
- pressure is (1)
- resistance is (2)
- CO of RV = (3)
1 = much lower (15 mmHg)
2 = lower
3 = pulmonary blood flow
What is the relationship between airway resistance and radius of the airway?
Resistance is inversely proportional to the fourth power of the airway
What is the A-a gradient used for? What is the normal A-a gradient?
A-a gradient = PAO2 - PaO2
Alveolar - arterial
A-a gradient can be used to compare causes of hypoxemia.

Normal A-a gradient < 10 mmHg
Shifts to right in Heme-O2 dissociation curve are
Occur b/c of Decreased O2 affinity
Increase in pCO2
Decrease in pH
Increase in Temp
Increase in 2,3 DPG
what happens to the mean values of arterial P(O2) and P(CO2) during exercise
they do not change
blood flow is lowest in the (1) of lung and highest at (2)
1 = apex (zone 1)
2 = base (zone 3)
What is the major site of airway resistance?
Medium-sized bronchi
What is the A-a gradient for the following conditions?

High altitude
Hypoventilation
Diffusion defect (e.g. fibrosis)
V/Q defect
Right-to-left shunt
High altitude: Normal
Hypoventilation: Normal
Diffusion defect (e.g. fibrosis): Increased
V/Q defect: Increased
Right-to-left shunt: Increased
What happens to the P50 in rightward shifts of heme-o2 curve
P50 is increased; O2 unloading occurs
what happens to physiologic dead space during exercise?
it decreases
zone 1
- blood flow (1)
- alveolar pressure is (2) than arterial pressure
1 = lowest
2 = greater than
--> high alveolar pressure compresses capillaries
--> hemorrhage or positive pressure ventilation
What factors cause the bronchial smooth muscle to contract?
Parasympathetic stimulation
Irritants
Slow-reacting substance of anaphylaxis (asthma)
What are the three forms of CO2 in the blood?
1. Dissolved CO2
2. Carbaminohemoglobin
3. HCO3- (major form, 90%)
What is the Bohr effect?
Decreasing the affinity for hemoglobin for O2 and facilitating the unloading of O2 in tissues
what are physiologic adaptations in high altitude?
alveolar P(O2) is decreased, arterial P(O2) is decreased (hypoxemia), hyperventilation, respiratory alkalosis, increased EPO, increased 2,3-DPG, hypoxic pulmonary vasoconstriction
zone 2
- blood flow (1)
- alveolar pressure is (2) than arterial pressure
1 = medium
2 = lower
What factors cause the bronchial smooth muscle to relax?
Sympathetic stimulation
Sympathetic agonists
These things use beta 2 receptors
How does CO2 get converted to HCO3-? Where is it converted?
CO2 diffuses into RBCs, where it combines with H2O to form H2CO3. This reaction is catalyzed by carbonic anhydrase.
H+ and HCO3- are dissociated from H2CO3. HCO3- leaves the RBC in exchange for Cl- (chloride shift).
How does an increase in 2,3 DPG affect the heme-o2 curve?
Rightward sift
By binding B-chains of deoxyhemoglobin and decreasing the affinity for heme O2
What structures perforate the diaphragm and at what levels?
IVC (T8), esophagus (T10), vagus (T10), aorta (T12), thoracic duct (T12), azygous vein (T12).
zone 3
- blood flow (1)
- arterial pressure is the (2)
1 = highest
2 - highest
How does isoproterenol affect bronchodilation?
It is a sympathetic agonist, and this causes the bronchioles to dilate
What are the three zones? What is the comparison of the pressures?
Zone 1: blood flow is lowest
Alveolar pressure > arterial pressure > venous pressure

Zone 2: blood flow is medium
Arterial pressure > alveolar pressure > venous pressure

Zone 3: blood flow is highest
Arterial pressure > venous pressure > alveolar pressure
How does the body compensate for living in high altitude?
Increases synthesis of 2,3 DPG which binds hemoglobin and Facilitates O2 unlaoding
By what is the diaphragm innervated?
phrenic nerve (C3, 4, 5) (keeps the diaphragm alive)
In contrast to other organs, in lungs, hypoxia causes (1) which redirects blood away from poorly ventilated, hypoxic regions
1 = vasoconstriction
How does lung volume contribute to airway resistance?
Lung tissue exerts radial traction upon the airways
High lung volumes are associated with greater traction and decreased resistance
Low lung volumes exert less traction, and there can be resistance to the point of airway collapse
In the lung, what happens during hypoxia? Why?
Hypoxia causes vasoconstriction. Physiologically, this effect is important because local vasoconstriction redirects blood away from poorly ventilated, hypoxic regions of the lung and toward well-ventilated regions.
How does CO, CArbon monoxide affect the heme-O2 curve?
Left-ward shift, b/c 250-times binding affinity
CO decrease the O2 content by binding direct to O2 sites
What are the accessory muscles of inspiration?
external intercostals, scalene muscles, sternocleidomastoids
right to left shunts
ex. tetralogy of fallot

--> always decrease arterial PO2
How do the density and viscosity of an inspired gas affect airflow?
They change the resistance to airflow
During deep-sea diving, air density increases and resistance increases
Low-density gases such as helium reduce airflow resistance
What is the normal V/Q ratio?
V/Q = 0.8
What affect does respiratory alkalosis have on heme-O2 curve?
A left-ward shift, Increase in pH
what are the accessory muscles of expiration?
rectus abdominis, internal and external obliques, transversus abdominis, internal intercostals
V/Q ratio
ratio of alveolar ventilation to pulmonary blood flow
What are the thoracic pressures at rest, before inspiration begins?
Alveolar pressure = atmospheric pressure = 0
Intrapleural pressure is negative due to the opposing forces of the lungs trying to collapse and the chest wall trying to expand
Where is blood flow highest? Where is ventilation highest?
Blood flow AND ventilation are highest at the base of the lungs.
What affect does a left-ward shift have on P50?
The P50 is decreased, unloading of O2 into tissues is difficult
what molecule activates bradykinin?
Kallikrein
Where is the V/Q ratio highest? (apex or base)
apex
Which of the standard lung volumes is in the lungs at rest?
The FRC
Where is the V/Q ratio highest? Where is the V/Q ratio lowest?
The V/Q ratio is highest at the apex (3.0), and lowest at the base (0.6).
What is hypoxemia?
Decreased in arterial pO2
What is the effect of CO poisoning?
causes a decrease in oxygen binding capacity of Hb with a left-shift in the oxygen dissociation curve
apex has (1) regional arterial PO2 and (2) regional PCO2 bc gas exchange is more efficient
1 = highest
2 = lower
What happens to the thoracic pressures during inspiration?
The inspiratory muscles contract and increase the thoracic volume
This causes the intrapleural pressure to become more negative
The increased transmural pressure on the alveoli causes the alveolar pressure to become negative
The pressure gradient between the alveoli and the air causes air to flow into the lungs
What is a shunt? What can cause a shunt?
V/Q = 0
When the airways are completely blocked (e.g. by a steak caught in the trachea).
What is the A-a gradient?
Pao2-Pa2, difference between alveolar and arterial pO2
Calculation of pulmonary vascular resistance?
PVR = [P(pulm artery) - P(wedge)] / Cardiac outupt
dorsal respiratory group
- inspiration
- generates basic rhythm of breathing
How does lung volume relate to elastic recoil?
Elastic recoil is greatest when the lungs contain high volumes
What is dead space?
V/Q = infinite.
When the blood flow to a lung is completely blocked (e.g. by an embolism)
Why do we use the A-a gradient?
Can distinguish if hypoxemia is from the lungs or outside the lungs
ventral respiratory group
- expiration
- not active during normal quiet breathing --> only active when expiration is an active process
What do we measure when we want to know about the dynamic compliance of the lungs?
Changes in intrapleural pressure during inspiration
What nerves relay sensory information? Where does the information go?
Vagus nerve and glossopharyngeal nerve relays information to the dorsal respiratory group.
What is a normal A-a gradient?
<10mm Hg, b/c O2 equilibrates between alveolar gas and arterial gas
apneustic centre
lower pons
- stimulates inspiration
- deep and prolonged inspiratory gasp
Which of the standard lung volumes is in the lungs at the peak of inspiration?
FRC + TV
In what nerve does the output to the diaphragm travel?
Phrenic nerve
When the A-a is > 10 mm Hg what does it mean?
O2 is not equilibrating so;
Diffusion defect
V/Q defect
Right-to-left shunt
pneumotaxic centre
upper pons
- inhibits respiration
- regulates depth and rate of breathing
What happens to the thoracic pressures during expiration?
The inspiratory muscles relax and the thoracic pressure becomes less negative
This causes the alveolar pressure to become positive
The pressure gradient causes air to flow from the lungs out the airway
Where are the central and peripheral chemoreceptors located?
Central chemoreceptors are in the medulla.
Peripheral chemoreceptors are in the carotid and aortic bodies.
What is hypoxia?
decreased O2 delivery to the tissues.
central chemoreceptors
- located in medulla
- sensitive to pH of CSF (decreases in pH increased breathing)
What happens to intrapleural pressure during a forced expiration?
It becomes POSITIVE
During quiet expiration, IPP becomes less negative, but never actually becomes positive
Positive IPP can compress the airways and make expiration more difficult
How does increased CO2 activate the central chemoreceptors?
CO2 diffuses from arterial blood into the CSF (CO2 is lipid soluble). In the CSF, CO2 combines with H2O to produce H+ and HCO3-. The resulting H+ acts directly on the central chemoreceptors. Thus, increases in PCO2 and [H+] stimulate breathing, and decreases in PCO2 and [H+] inhibit breathing.

Metabolic acidosis -> hyperventilation
What is the equation for O2 delivery?
= Cardiac output X O2 content of blood
peripheral chemoreceptors
- location? (1)
- respond preferentially to? (2)
1 = carotid and aortic bodies
2 = decreased PO2 (<60 mmHg)
How is breathing altered in a patient with COPD?
Airway resistance is increased
Patients learn to expire slowly with pursed lips
This prevents the airway collapse that can occur with a forced expiration
In response to exercise, does the arterial PO2 and PCO2 change? What about the Venous PCO2? V/Q ratios?
The arterial PO2 and PCO2 do not change in response to exercise. Venous PCO2 does increase.
The V/Q ratios are more evenly distributed in the lung during exercise.
What does O2 content depend on?
Hg concentration
O2-binding capacity
% saturation
Hering-Breur Reflex
receptors are stimulated by distension of lungs, the produce a reflex decrease in breathing reflex
Which of the standard lung volumes is in the lungs at the end of a quiet expiration?
The FRC
In the context of adaptation to high altitude, what are the changes to the following parameters:

Alveolar PO2
Arterial PO2
Ventilation rate
Arterial pH
Hemoglobin concentration
2,3-DPG concentration
Hemoglobin-O2 curve
Pulmonary vascular resistance
Alveolar PO2: decreased (resulting from decreased barometric pressure)
Arterial PO2: decreased (hypoxemia)
Ventilation rate: increased
Arterial pH: Increased (respiratory alkalosis)
Hemoglobin concentration: Increased (polycythemia)
2,3-DPG: Increased
Hemoglobin-O2 curve: shift to right
Pulmonary vascular resistance: increased (hypoxic vasoconstriction)
What are the causes of hypoxia?
Decrease CO
Decrease O2-binding capacity
Decreased arterial pO2
J (juxtacapillary) receptors
located in alveolar walls close to capillaries --> engorgement of capillaries i.e. left heart failure causes rapid, shallow breathing
What is asthma?
An obstructive disease where expiration is impaired
Patients have low FEV1/FVC
Air that should be expired is instead getting trapped, which causes the FRC to increase
If a patient has a decreased Pao2 and normal A-a gradient, what should you think?
1) Hypoventilation

2)High altitude

Distinguish by high altitude b/c low air/ barometric pressure:
joint and muscle receptors and breathing
early stimulation of breathing during exercise
What is COPD?
A combination of chronic bronchitis and emphysema
Obstructive disease with increased lung compliance, so expiration is impaired
Decreased FEV1/FVC
Air that should be expired is trapped, leading to increased FRC and a barrel-shaped chest
Name all the diseases associated with restrictive lungs diseases
1.Lung tissue abnormalities: pulmonary fibrosis, silicosis, asbestosis, tuberculosis
2. Pluera problems: Pneumonthorax, Pleural Effusion
3. Neuromuscular: Polio, Myasthenia Gravis
What are "pink puffers?"
COPD patients who primarily have emphysema
Mild hypoxemia
Normocapnia because alveolar ventilation is maintained
Name all of the diseases associated with obstructive lung diseases.
1. Obstructed airway lumen; chronic bronchitis, edema, or food aspiration
2. Asthma, constricted of airway muscles
3. Outside of airway; emphysema = lung tissue destruction
What are "blue boaters?"
COPD patients who primarily have bronchitis
Severe hypoxemia with cyanosis
Hypercapnia because alveolar ventilation is not maintained
Right ventricular failure and systemic edema
Where does Asthma usually take place and how does it occur?
Hypersensitivity reaction of the bronchioles; produces edema and bronchospasm
What is fibrosis?
Restrictive disease associated with decreased lung compliance, so inspiration is impaired
All lung volumes are decreased
FEV1/FVC is increased
What is the PCO2 value when a person is hypercapnic and breathing rapidly and deeply
60 to 75 mm Hg
What is Dalton's law of partial pressure?
Partial pressure = total pressure x fractional gas concentration
At what level of PCO2 does a person become lethargic and semicomatose,
80 -100 mm Hg pCO2
What is the fractional concentration of oxygen in dry inspired air?
21%
What is the PCO2 value when a person is hypercapnic and breathing rapidly and deeply
60 to 75 mm Hg
When calculating the partial pressure of oxygen in humidified tracheal air, what do we have to do to calculate?
You have to subtract the partial pressure of water (47 mmHg) from the total pressure before multiplying by the fractional concentration of oxygen
At what level of PCO2 does a person become lethargic and semicomatose,
80 -100 mm Hg pCO2
Are the systemic and pulmonary circulations entirely separate?
No
2% of cardiac output bypasses the pulmonary circulation (physiologic shunt), and this venous blood mixes with arterial blood
This makes the PO2 of arterial blood slightly lower than the PO2 of alveolar air
How many forms of CO2 are carried in the blood? Name them
3 forms
1: Dissolved CO2, free in solution
2: Carbaminohemoglobin, CO2 bound to heme
3: HCO3-, major form ~ 90%
How much gas dissolves in solution?
An amount that is proportional to the partial pressure
How is CO2 carried in the RBC? IE Formula
CO2 combines with H2O to form H2CO3-
H2CO3- dissociates into H+ + HCO3-
Formula for dissolved gas in solution
Dissolved gas = partial pressure of gas x solubility in blood
how does HCO3- get out the RBC?
HCO3- is exchanged for CL- ion
HCO3- is then transferred in the blood, the major form of CO2
What factors impact the diffusion rates of O2 and CO2?
The partial pressure difference across the membrane
The surface area available for diffusion
What happens to H+ ion generated in the RBC from H2CO3- dissociation?
H+ is buffered by deoxyhemoglobin
What gases exhibit perfusion-limited exchange?
N2O
O2 (under normal conditions)
In the lungs, what reactions take place in the RBC?
HCO3- enters the RBC
Cl- is kicked out in exchange
H+ recombines to form H2CO3
H2CO3 decomposes to CO2 and H2O
CO2 is expired
What is perfusion-limited exchange?
The gas equilibrates early along the length of the pulmonary capillary
The partial pressures of the gas in the arterial blood and alveolar air become equal
Diffusion of the gas can be increased only if blood flow increases
What are the pressures in pulmonary circulation when compared to systemic?
Lower, eg pulmonary artery is 15mm Hg and aortic is 100mm hg
What gases exhibit diffusion-limited exchange?
CO
O2 (emphysema, fibrosis, and during strenuous exercise)
What is the resistance in pulmonary circulation vs systemic?
Much lower
What is diffusion-limited exchange?
The gas does not equilibrate by the time the blood reaches the end of the pulmonary capillary
The partial pressure difference of the gas between the arterial blood and the alveolar air is maintained
Diffusion continues as long as there is a partial pressure gradient
Pulmonary blood flow is equal to CO of ______
Right ventricle
How does fibrosis cause O2 to become diffusion-limited?
Thickening of the alveolar membrane increases diffusion distance
This restricts the diffusion of O2
Cardiac output of the right ventricle is equal to
CO of the left ventricle
How does emphysema cause O2 to become diffusion-limited?
The surface area for gas diffusion is decreased
If the pressure of pulmonary circulation are low how are they sufficient to pump CO?
B/c the resistance in pulmonary circulation is low
How is oxygen transported in the blood?
Dissolved
Bound to hemoglobin (most important mechanism)
Zone one blood flow in the lung is
the lowest
What is the structure of adult hemoglobin?
Globular tetramer
Each subunit has a heme moiety, which is iron-containing porphyrin
The iron is in the ferrous 2+ state, which binds oxygen
If the iron is in the ferric 3+ state, it is methemoglobin and will not bind oxygen
Made of 2 alpha and 2 beta chains (normal adult Hb is known as a2B2)
What is the sequence of pressures for zone? Eg alveolar, arterial, venous
Alveolar>Arterial>venule
What is the structure of fetal hemoglobin?
The beta chains are replaced by gamma chains, so fetal Hb is known as a2y2
Where is arterial pressure greater than alveolar and venule pressures?
Zone 2
Arterial>Alveolar>Venule
Zones in the lung
What is the difference in oxygen affinity between adult and fetal hemoglobin?
Fetal Hb has higher oxygen affinity
This means the oxygen dissociation curve is left-shifted relative to the adult curve
Because of this phenomenon, a fetus will draw maternal oxygen across the placenta