Exam II Flashcards
What are the two types of baroreceptors that help maintain BP & CO?
Carotid & Aortic
Where are the carotid baroreceptors located?
At the bifurcation of the carotid arteries
What attaches the carotid baroreceptors to the brainstem?
Glossopharyngeal
Where are the aortic baroreceptors located?
Aortic arch
What is the aortic baroreceptor a product of?
Vagus nerve
Which two catecholamines can be released locally or systemically by the adrenal gland to affect contractility & SVR?
Norepi & Epi
What are the two most protected circulatory beds?
Coronary & Central nervous system
- & to some extent kidneys
Which beds can shunt blood away from it when the body is in need?
GI
Changes in osmolarity will manage ___ levels
Vasopressin
- if Bp is really low CV system can add vasopressin
When needed the CV can stimulate the RAAS to increase BP, which mineral corticoid is associated with the RAAS?
Aldosterone
There is a reflex built into the atria where if it is over distended or too full it will stimulate the kidneys to do what? & how does it accomplish this?
Increase output by decreasing sympathetic tone to the kidneys
What is risk to having an excess in blood volume?
the more blood volume you have the slower the circulation rate –> slower circulation rate increases the risk for coagulation
What is ANP/ANF? what is its function? Where is it predominantly made?
a protein formed in the atria – predominantly RA – released when atria becomes stretched out – it gets rid of sodium & water by increase u/o in kidneys
What is BNP? Where is it formed? What is its function?
Brain natriuretic peptide – protein formed in the ventricles that works similarly to ANP
What can BNP be used as?
A marker to see how well HF treatment is going
- rise in BNP –> ventricle is being stretched out
- drop in BNP –> HF treatment is working
What is a downfall to BNP/ANF/ANP?
its affects only last about a week
If the normal amount of blood circulating in the system is 5L, how much of it is plasma & how much is Hct?
3L plasma
2L Hct
If we were to lose 20% of our circulating blood volume, how much would we lose? How much is plasma? How much is Hct?
1L
600mL plasma
400mL Hct
if we were to lose blood volume, fluid would shift from the ISF to the CV to make up for the loss, what will make it difficult to keep the volume in the CV system after it has shifted over?
The loss of capillary proteins
What is the pitfall to replacing blood volume loss with NS?
NS has no colloids –> 1/4 to 1/5 will actually stay in the CV the rest will go to the ISF
Which organ are we most concerned with when replacing blood loss with NS?
Lungs
- the water layer in the lungs is extremely thin, it has no room for extra fluid shifting over into it
What were the large sugar molecules mentioned in class that could be used as a synthetic colloid to temporarily provide an increase of oncotic pressure?
Dextran & Hetastarch
Stretch relaxation is a property of large veins, describe what this property is
it is a response by the smooth muscles in the walls of the veins –> when they become distended or tight post bolus the smooth muscle relaxes –> reducing venous pressure
What is reverse stretch relaxation?
autonomic NS overriding the smooth muscles in the veins & tightening up the walls of the veins
The strongest SNS response to maintain CO & perfusion is the?
CNS ischemic response from the brain stem
- stimulated when perfusion to the brain stem is low for a few minutes
Arterial blood normally has how many mLs of O2 per dL of blood?
20mL
Venous blood normally has how many mLs of O2 per dL of blood?
15mL
if you took the difference between the arterial oxygen content and the venous oxygen content, it would give you what? & what would this tell us?
5 mL O2/dL blood
this tells us how much oxygen is dropped off at the tissues in circulation
What is the average amount of oxygen the blood consumes in a minute?
250mL O2
What is cardiac reserve?
Max amount of cardiac output that you can get above what is normal in a patient.
What is cardiac reserve in a normal, healthy person?
400% cardiac reserve
What is cardiac reserve in an elite polka dancer?
600% cardiac reserve; baseline CO may be elevated
What happens to cardiac reserve as we age?
It lowers, especially with disease states and sedentary lifestyle
Will patients with valvular disease have a cardiac reserve?
Not really
How do valve issues typically start?
Inflammation, followed by cholesterol deposits or calcification
More calcification/cholesterol on heart valves makes it _____ for coronary perfusion.
harder
What is the most common heart valve problem?
Aortic stenosis
What % of the population have a congenital bicuspid valve (aorta)?
1-2%. Instead of three leaflets, there are two.
Does everyone with a congenital bicuspid aortic valve need surgical repair?
Not really. It might not need to be replaced while young, but if you’re older with other valve issues this may exacerbate it.. might replace it then
The leaflets don’t fit together quite as well as a tricuspid with this disease state.
What is the pressure within the thorax in mmHg?
Where does this apply?
-4mmHg
Heart, lungs, any vessel/other thing in the thorax (sealed/normal environment)
What will is the normal motion of lungs on inspiration/expiration?
What changes if one leaflet of the diaphragm is paralyzed?
On inhalation the lungs move down, on expiration the lungs move up.
i.e.
If the right leaflet of the diaphragm is paralyzed and someone takes a breath, the left lung will move down while the right lung moves UP. (inverse)
Which lung is bigger - left or right? Why?
Right lung is bigger than the left lung due to the space the heart takes up on the left.
How many leaflets does the diaphragm have?
Two - left & right
Where is the apex (top) of the lung?
Can be very superior in patients and extend past rib 1, sometimes even above the clavicle.
What are the linings of the lungs called that help it glide without hurting/friction?
Pleura
How many pleural linings do we have?
What are their names?
Two
Visceral pleura
Parietal pleura
Note: Both connective tissue
What does “visceral” mean?
Organ
Where does the visceral pleura sit?
It is the membrane immediately surrounding the lungs
Where is the parietal pleura?
Stuck to the chest wall/inside of the thorax
What is between the visceral and parietal pleura, and why is it important?
Coating of mucous
Important because it helps the lungs glide freely without friction/pain.
What happens if you have a pleural infection?
Lungs will not slide around as well and it will be painful.
Note: Sometimes respiratory infections may lead to airway pain, while other times it may be an infection of the pleura and cause pleural pain.
When the diaphragm contracts, what happens?
Lungs are pulled down, creating a negative pressure. This pulls air in to the lungs.
Where are the leaflets of the diaphragm anchored?
Is there any special anatomy between this anchor?
Lumbar spine
Opening on the anterior part of the vertebral body for aorta called the aortic aperture.
How many openings are there in the diaphragm to allow passage inferiorly?
Three
One for the vera cava (caval aperture), one for the aorta (aortic aperture), and one for the esophagus (esophageal aperture)
Note: Picture is an inferior view of the diaphragm
Most of the diaphragm is what type of muscle?
Skeletal muscle
Tendons connect what structures?
Muscle to bone
Ligaments connect what structure?
Bone to bone
What structure in the diaphragm is out of the ordinary for its normal function in the body?
Central tendon. Normally tendons connect muscle to bone. Here, the tendon is where the heart rests on the diaphragm. It is NOT connected to bone.
Pic = inferior view
Where does the phrenic nerve connect on the spinal cord? How many are there, where does it pass, and what does it work on?
C3-5
Two
Passes on each side of the neck, across the heart, then on to each side of the diaphragm
What do regional blocks help with?
Helps post recovery
Minimizes opioids
Good to use if someone can’t go under GA
Problem with regional blocks (cervical/brachial)?
Phrenic nerve hangs around in that area. If the anesthetics move, we can knock out the phrenic nerve, causing breathing problems.
In a healthy person, can you live with one phrenic nerve? What about an unhealthy person?
Healthy? - only really need one, second one is redundant
Sick? - Probably will die
What are the three accessory muscles mentioned in class?
Scalene, intercostal, and abdominal muscles
Is the phrenic nerve the only nerve in the thorax?
No
Vagus (L/R) for SA/AV node
Phrenic
SNS branches for myocardial tissue
Among many more
What are accessory muscles, insertion points, and function?
Extra muscles that can be used to breathe if the body is stressed/exercising.
They are anchored in the base of skull/top of neck, and provide a platform to pull the ribcage up. They also can prevent the ribcage from being pulled down when the diaphragm contracts.
What is the main muscle of inspiration?
Diaphragm
Regarding airways, what is a “generation,” and how many are there?
A generation is the split in airways from the trachea to alveoli. There are 24 generations, starting with generation 0 (trachea) and ending with 23 (alveoli)
What generation is the trachea?
0
What generation is the bronchi?
1-3
What generation are the bronchioles?
4
What generation are the terminal bronchioles?
5-16
What generation are the respiratory bronchioles?
17-19
What generation are the alveolar ducts?
20-22
What generation are the alveolar sacs?
23 (final)
Note, this is generation 23, but considered the 24th generation since it starts with 0 (trachea)
Within the airways and alveoli, what has the smallest cross sectional area?
Bronchi, generation 3
What happens as you move to the next generation of airways?
Number of tracts in the generation doubles
i.e.
Generation 0 = 1 tract
Generation 1 = 2
Generation 2 = 4
Generation 3 = 8
Generation 4 = 16
etc
I feel that this may be a test question??
Where is there a dramatic increase in cross sectional area within the airways/alveoli?
Why is this?
Between generation 16 and 19.
Generation 17 is the start of respiratory bronchioles, and alveoli sac begin to appear here, dramatically increasing cross sectional area to accommodate gas exchange
What is included in the “conducting zone” of the airways?
Trachea, bronchi, bronchioles, and terminal bronchioles.
Generation 0-16
There is no gas exchange here.
What is included in the “respiratory zones?”
Alveolar ducts and sacs
Generation 20-23
Main gas exchange occurs here*
What zone is between the conducting and respiratory zones of the airway? What is included here, and what generations?
Transitional zones
Respiratory bronchioles
Generation 17-19
Some gas exchange, but not incredibly significant until alveolar ducts. Still impact gas exchange. It’s where alveoli start to appear.
What is the typical tracheal diameter in a normal adult?
2cm
What is a large difference in structure between the conducting zones (specifically bronchioles) and the respiratory zones?
Bronchioles have cartilage supporting them to keep them open/patent, while the respiratory zones are entirely soft tissue.
What is Eupnea?
Normal breathing
What is Dyspnea?
Respiratory distress, not enough air
What is apnea?
No breathing at all
What is stridor?
Funny sounds coming from lungs, i.e. asthma, lung tumor, smooth muscle spasm.
“Sounds like a recorder.”
What is bradypnea?
Slow breathing
What is tachypnea?
Rapid breathing
What is hyperventilation?
Ventilation well in excess of metabolic demand
What is orthopnea?
Change in breathing when changing body positioning
What is hyperinflation?
Big lungs that are much larger than they should be (COPD; loss of connective tissue that makes lungs hard to expand)
What is Cyanosis?
DeoxyHb of >5 gm/dL;
Lots of DeoxyHb (blue coloration)
Threshold is what our normal venous oxygen looks like
What is hypoventilation?
insufficient ventilation for metabolic demand
What is Hypoxia?
Decreased amount of O2 at the level of a tissue; localized
What is hypoxemia?
Decreased amount of O2 in the blood (art) (entire system)
What is the main difference between hypoxia and hypoxemia?
Hypoxia = localized to a certain area
Hypoxemia = systemic
What is hypercapnia?
Excessive CO2 in blood (art); hypercarbia (COPD, etc)
What is hypocapnia?
Deficiency of CO2 in blood (art); hypocarbia (overbreathing maybe)
What is hyperoxia?
O2 levels above normal (tissues/organs)
This is regional, not systemic
What is atelectasis?
Collapse of functional lung units
Consider causes of this*
In the CV system, what unit of pressure do we use?
How does this differ from the lungs?
mmHg
In pulmonary, we use both mmHg AND cmH2O depending on what is being measured.
What might we use mmHg to measure pulmonary wise?
Gas pressures
In the pulmonary system, what do we use cm H2O for?
Intrathoracic, pleural, intrapleural pressures
The pressure inside the chest is typically ____.
Subatmospheric
1 mmHg = _____ cm H2O
1.36 cm H2O
In high pressure systems, why is it easier to use mmHg vs cm H2O?
When might we want to use cm H2O?
Easier to eyeball pressures.
Mercury is much more dense than water, so when dealing with low pressures such as those in the thorax it is easier to measure with a less dense medium such as water. This allows for greater -resolution-, and helps us eyeball thorax pressures easier.
P (capital) stands for
Pressure
What is “content?”
We use this with blood gases.
i.e., 1dL arterial blood has O2 quantity of 20mL/dL/blood
This number is the “O2 content” of the blood
How can you tell the difference of content between an arterial vs venous sample?
Depends on the subscript after P (capital P for pressure)
A capital A stands for
Alveolar
A lowercase a stands for
Arterial
What is PaO2?
What about PAO2?
PaO2 = pressure of dissolved oxygen in an arterial sample (should be ~100)
PAO2 = pressure in the alveoli of oxygen (Po2 in alveolar gas)
What does a lowercase v stand for?
What about Pv?
venous
Pressure in the veins
What does a capital V stand for?
Ventilation, AKA how much air is coming in/out
What is Vt?
Tidal volume
Is it easier to measure air going into a patient, or out of the patient?
What is this measurement?
Out of patient (can measure air going in, but harder to do)
VE = expired gas
What is the volume of O2 delivered per minute?
What is another term to describe this?
250mL/min
VO2 = volume of oxygen per minute
How much oxygen is delivered per dL of blood usually to maintain oxygenation?
We have a 5L (aka 50dL system).
250ml/O2/min O2 is delivered and used.
250mL/min divided by 50dL = 5mL/O2/min
5mL/O2/min is delivered to maintain oxygenation
What is the inverse of compliance?
Elastance
What does V̇ mean?
Oxygen delivery per unit time
V is ventilation
We use minutes for ventilation, meaning that V̇ is the volume/minute of ventilation.
What is compliance?
Behavior of tissue; stretchy
If you have a high compliance, you will have a _____ elastance.
Low - remember, inverse
What is the total lung capacity (TLC)?
Total amount of air that the lungs can hold.
Normal value is 6L
What makes up the Total lung capacity (TLC)?
Inspiratory capacity (IC) and functional residual capacity (FRC).
What makes up functional residual capacity (FRC)?
Expiratory reserve volume (ERV) and residual volume (RV)
What makes up inspiratory capacity (IC)?
Inspiratory reserve volume (IRV) and Tidal volume (Vt)
What makes up the vital capacity (VC), and what is the value?
Inspiratory reserve volume (IRV), Tidal volume (Vt), and expiratory reserve volume (ERV).
The volume is 4.5L in a healthy person.
How much is a normal tidal volume (Vt)?
500mL, or 0.5L. Half a liter in, half a liter out.
Each lung holds how much of the total lung capacity (TLC)?
3L, for a total of 6L
Note, he may throw a question in the test where someone loses a lung or % of function. Be prepared to do math to figure out how the volumes would change.
What are all of the sub components of total lung capacity (TLC), and the volume associated with it?
Tidal volume (Vt), Inspiratory reserve volume (IRV), Residual volume (RV), and Expiratory reserve volume (ERV).
2.5L + 0.5L + 1.5L + 1.5L = 6L
Should be a total of 6L in a healthy adult.
What is functional residual capacity (FRC)?
It is 3L in a normal person.
When we take a normal breath (500mL = Vt), it is added to this 3L, and when we exhale we return to this 3L.
What is different between expired and inspired gas due to functional residual capacity?
Expired air has less O2 than inspired air, BUT expired air still has some O2 in it. Oxygen moves to equalize its gradient between Vt and FRC, leaving some oxygen breathed out, and some oxygen still in the lungs for between breaths.
How can we hold our breath?
Functional residual capacity (FRC).
Some oxygen stays in the lungs for gas exchange. Not as efficient, but allows us to live between breaths.
If we didn’t have a FRC of 3L, we would have abrupt changes to our blood gasses.
If someone didn’t have functional residual capacity, what would happen?
On inspiration we would see a spike in oxygen content, but then on exhalation to oxygen content would drop dramatically. FRC stabilizes blood gases and more importantly, helps keep airways open. Remember that respiratory zones are soft tissue without cartilage structure.
Low functional residual capacity puts someone at more risk of what?
Atelectasis
What is the normal expiratory reserve volume (ERV), and what is it?
In a healthy 20 y/o, it is 1.5L
Volume of air that we can force out after a normal expiration
What is the normal Residual volume (RV), and what is it?
1.5L
This is the air that we cannot push out of our lungs even if we try. Even with maximal expiration, residual volume of 1.5L remains.
Note: Trying to push harder to get this out only results in airways closing which further prevents this air from leaving the lungs.
What is inspiratory reserve volume (IRV), and what is the value?
Amount of air we can inspire in addition to a normal Vt
2.5L is the normal IRV. The majority of inspiratory capacity is IRV.
What is the resting volume within a healthy persons lungs?
3L
What is the amount of air we can take in starting from resting volume (3L) to max?
3L
Resting lung volume + Vt =
3.5L
Resting lung volumes + inspiratory capacity =
6L
Resting lung volume - ERV =
1.5L
What happens to lung volumes when we lay down?
Gravitational weight from the stomach pushes the diaphragm up and removes a little air from the lungs
ERV is squeezed out*
Maximal breath that we can take?
3L (Vt + IRV)
How many seconds is a respiratory cycle?
5 seconds
Note: Diagrams say 4 seconds, but Schmidt mentioned that we have one second where nothing happens between respiratory cycles. He says 5 seconds.
What is the breakdown of the respiratory cycle?
2 seconds inspiration
2 seconds expiration
1 second of nothing
What is a normal RR, and how do we find it?
60 seconds in a minute
5 second respiratory cycles (normal, at rest)
60/5 = 12RR
In this picture, which side is inspiration/expiration?
left = inspiration
Right = expiration
What is the pressure inside of the thorax in both mmHg and cm H2O?
-4mmHg
-5cm H2O
In between breaths (between the 4th and 5th second of the respiratory cycle), what is the pressure within the thorax?
-5cm H2O
At the end of inspiration, what is the pressure within the thorax? Why?
-7.5cm H2O
This pressure is reached at the START of the 2nd second of the respiratory cycle
Diaphragm pulls down on a closed system - this brings the lungs down, expands them, and lowers the pressure allowing for air to move into the lungs.
This pressure assumes a normal Vt (500mL)
At the beginning of the 2nd phase of the respiratory cycle, what is the normal volume inspired?
Vt, which is 500mL has been inspired.
When inspiration starts, what is the air flow rate? When does it peak?
Slow
Peaks at the 1 second mark (-0.5L/sec)
What does a negative air flow rate mean?
Air is flowing into the lungs (inspiration, peak at 1 second)
What does a positive air flow rate mean?
Air is flowing out of the lungs (expiration, peak flow at the 3rd second of the respiratory cycle).
0.5L/sec
What is air flow rate measured in?
L/sec
Does thoracic pressure decrease linearly over the two seconds of inspiration?
Book/schmidt answer = yes, linear
Clinical answer = probably curved
BONUS from flight school, this is NOT from Schmidt but he may use something like it later. Just to get you thinking of potential questions.
- Tyler
How is alveolar pressure related to atmospheric pressure? What is the significance?
Higher atmospheric pressure will result in higher alveolar pressure, at the atmosphere of the alveoli are connected to the outside atmosphere via the airway. They have a direct relationship. This helps keep the alveoli open (within reasonable pressure).
Lower atmospheric pressure (as can be seen with altitude, especially over 10,000ft) lowers alveolar pressure since the two are directly related. Alveoli do not have cartilage supportive structures and are made of soft tissue. The drop in alveolar pressure results in lower partial pressure of oxygen in the alveoli (less oxygen available to exchange into blood), which leads to hypoxia at high altitudes. This is what causes elevation sickness/hypoxia.
Physiologic compensations: Increase RR (increase of alveolar ventilation), increased Hg/affinity, increased tissue extraction of O2
tl;dr
Atmospheric pressure/alveolar pressure are directly related.
Low alveolar pressure reduces partial pressure of O2 in alveoli, resulting in potential hypoxia.
What is the normal alveolar pressure at sea level?
0cm H2O
Key word: Sea level.
–
As elevation increases, atmospheric pressure generally decreases
What is the normal atmospheric pressure?
760mmHg
Just in case he’s a bully, this is 1,033.6 cm H2O
760mmHg x conversion factor of 1.36 = 1,033.6 cm H2O
When air is entering a healthy lung quickly at 0.5L/s, what is the pressure in the alveoli?
What about when it is exiting at -0.5L/s?
-1 cm H2O
+1 cm H2O
What is the pressure inside the alveoli after inspiration, but before expiration?
What second of the breathing cycle is this?
0 cm H2O @ the 2 second mark
If the alveoli pressure is negative, air moves ___
Into the lungs
If the alveoli pressure is positive, air moves ____
Out of the lungs
Rate of air flow is dependent on what?
ΔP
At the end of inspiration, the alveolar pressure is 0 cm H2O. This is at the 2 second mark of the respiratory cycle.
What is the thoracic pressure at this point?
-7.5 cm H2O
When the diaphragm relaxes for expiration, what happens to alveoli pressure and thoracic pressure?
Thoracic pressure becomes more positive over expiration (-7.5 cm H2O –> -5 cm H2O), which makes alveoli pressure +1 cm H2O and allows for expiration. After expiration, alveoli pressure return to 0 cm H2O at the 4 second mark of the respiratory cycle.
When air moves into the lungs, alveoli are stretched. The tissue is stretched as well. What is this called, and why is it important?
Elastic recoil. We rely on this to push air out of the lungs*
If a patient has abnormal elastic recoil of the alveoli, you have problems doing what?
Getting air in or out of the lungs
If someone has “messed up lungs,” what phase of the respiratory cycle will always be longer?
Expiration (phase 2-4)
Name a disease that impacts getting air out of the lungs (problem with elastic recoil).
COPD
Name a disease that impacts getting air into the lungs (problem with elastic recoil).
Fibrotic tissue
Expired airflow rate peaks when?
One second into expiration
OR
phase 3 of respiratory cycle
+0.5L/s airflow rate
+1 cm H2O alveoli pressure
Thoracic pressure is linear, and is ~-6 cm H2O at this point
What is PIP?
Note: IP is supposed to be a subscript
Pleural pressure
What is PA?
Note: A is subscript
Alveolar pressure
What is PTP
Note: TP is a subscript
Transpulmonary pressure
AKA
Difference in pressure. Compares pressures.
(i.e. pleural pressure vs alveolar pressure)
-5 cm H2O thoracic vs 0 cm H2O alveolar pressure = PTP of 5 cm H2O
Why is Transpulmonary pressure (PTP) important?
This is the pressure we use to fill the lungs with air (i.e. negative/positive ventilation)
This is the pressure that will put air into the lungs. Dependent on pleural pressure**
How many “west perfusion zones” are there?
4
Note: 3 on the Guyton graph but daddy doesn’t agree with guyton - addressed on slide 35 lecture 5 pptt, 4th zone being the lungs resting on the diaphragm
Where does functional gas exchange occur?
Alveoli; each is surrounded by capillaries
How are west perfusion zones separated?
Zone 1 is the apex
Zone 2 is the middle
Zone 3 is the lower part
Zone 4 is the very lowest part of the lung that rests on the diaphragm
Note: This is in an UPRIGHT patient. Zones dependent on gravity.
What is the blood flow through lungs dependent on?
Gravity
What is the “always on blood flow” area of the lung? (west perfusion zone).
Why?
Zone 3
Pressure is higher lower in the lungs; dependent on gravity. Blood vessels wider at the base of the lungs due to this, and have less resistance to perfusion.
What is the formula for west perfusion zone 2?
Pa>PA>Pv
In west perfusion zone 2, if BP is higher what happens to blood flow?
What if BP is low?
Increases blood flow
Decreases blood flow if BP is low
Which has a higher blood flow - west perfusion zone 2 or 3? Why?
Zone 3
If someone is upright, zone 3 is below zone 2. This means pressures are higher here.
Higher pressures in compliant pulmonary tissue stretches blood vessels out. Wider blood vessels have less resistance to perfusion, allowing for higher blood flow.
Which west perfusion zone has continuous blood flow throughout the entire cardiac cycle?
Zone 3
What is the formula for west perfusion zone 3?
Pa>Pv>PA
Why do we put the “good lung” down when someone has a pulmonary surgery?
Blood flow in zone 3 is dependent on gravity. By putting the good lung down, it allows for higher pressures in the lower lung, allowing for more blood flow/perfusion/gas exchange.
What west perfusion zone is “in-between,” i.e. is on sometimes, not others?
Zone 2
Which west perfusion zone is “always off” in healthy people?
Why?
Zone 1 (top of lungs) in an upright position.
Vascular pressures are low, further from earth so pressures are slightly lower and harder to perfuse.
What is the formula for west perfusion zone 1?
PA>Pa>Pv
No blood flow through this since capillary will be compressed*
What is the #1 thing that we do that can cause west perfusion zone 1?
Why?
Positive pressure ventilation.
Normal fluctuation of alveolar pressure is from 0 cm H2O, to -1 cm H2O on inspiration, 0 cm H2O between inspiration/expiration (phase 3 of the respiratory cycle) to +1 cm H2O on expiration, back to 0 cm H2O for phase 5 of the respiratory cycle.
Positive pressure ventilations LOWEST setting is 5 cm H2O, which is FIVE TIMES as much pressure as our lungs are used to. This compresses blood vessels, which lowers or stops flow entirely.
How is positive pressure ventilation useful?
How is it detrimental?
Helpful: Holds airways open
Bad: Increases right side workload of heart and causes more west perfusion zone 1
^Note: Right side workload of heart is increased because right sided afterload (pressure in lungs) is increased with positive pressure ventilation.
What is the average blood flow through the lungs?
5L/min - all blood that flows through the heart must flow through the lungs, so it should equal cardiac output.
Where is most of the blood flow in the lungs occurring?
Bottom of the lungs
If blood flow is increased the lower in the lungs we are, why is blood flow decreased at the very bottom of the lung?
What is this referred to?
If someone is in an upright position, the lungs are suspended in the chest where they connect to the mediastinum. However, the base/bottom of the lungs are supported by the central tendon below.
Note: The heart rests directly on the central tendon, while the lungs are on the sides of the central tendon.
Lungs are heavy. The bottom of the lungs resting on the diaphragm compresses some blood vessels on the inferior part of the lung, decreasing blood flow slightly.
This is referred to as west perfusion zone 4.
What is perfusion in the lungs dependent on?
Gravity
Which region of the lung gets the most blood flow?
the dependent lung closest to the planet
What affect does gravity have on blood & the blood vessels of the lungs?
it makes blood weight more –> more weight of blood increases distention of blood vessels –> this decreases PVR
What is elastic recoil of the lung?
Tendency of the lung to collapse
- the more stretch we have the more recoil we normally have
What is elastic recoil also called?
Transpulmonary pressure
What is transpulmonary pressure?
pressure available to fill the lung up with air
What increases transpulmonary pressure?
Normal breathing & positive pressure ventilation
What happens when transpulmonary pressure increases?
Lung volume goes up
What happens when transpulmonary pressure decreases?
Lung volume goes down
What is the formula to find alveolar pressure?
PA = PIP + PER
or
PA = PIP + PTP
What is the formula to find transpulmonary pressure?
PTP = PA - PIP
The lowest possible lung volume is called?
Residual volume – RV (1.5L)
The highest possible lung volume is called?
Total lung capacity – TLC (3L) for each lung, total 6L
What is the smallest functional unit of the lung?
Alveoli
What is the point where pulmonary vascular resistance is at its lowest point?
FRC
What are the two components that make up PVR?
Extraalveolar blood vessels & Alveolar blood vessels
Which of the two pulmonary blood vessels are the larger ones? Where are they found?
Extraalveolar
found outside alveoli
What are the extraalveolar blood vessels mostly affected by?
Pleural pressure
What would happen to the extraalveolar blood vessels if pleural pressure were increase/made more negative?
the larger/wider the extra-alveolar blood vessels would become decreasing PVR
What would happen to the extraalveolar blood vessels if pleural pressure were decreased/made more positive?
The smaller/narrower the extra-alveolar blood would become increasing PVR
What would happen if we wanted to make lung volume lower than FRC? How would this affect PVR?
It would require effort –> this would increase pressure in the chest –> increasing PVR
Which of the two pulmonary blood vessels are the smaller ones? Where are they found?
Alveolar blood vessels
imbedded on the alveoli
Which blood vessels of the lungs does gas exchange take place?
Alveolar
What has the largest affect on alveolar blood vessels?
The volume amount of volume in the alveoli
What happens to alveolar blood vessels if a large amount of volume is put in the alveoli?
More volume –> capillaries stretch out & compress –> increased PVR
What happens to alveolar blood vessels in low lung volumes?
Less volume –> less capillary stretch & compression –> decreased PVR
When right heart CO increases, what happens to PVR?
How is this different than systemically?
Decreases
Systemically, there is not much compliance so pressure would increase if CO was increased. Pulmonary vessels are very compliant, so they get distended which decreases pressure/increases dilation.
What is a passive force that changes PVR?
Lung volumes with normal breathing; function of how much blood is in our blood vessels
What is the problem with right heart failure in regard to PVR?
It’s a vicious cycle..
Lower right heart CO –> Higher PVR –> Lower right heart CO –> repeat –> death
What are some causes of increased PVR?
Right heart CO drop
Right heart failure
MI of the right heart
Within pulmonary circulation, what happens as PVR is lowered? Why is this important?
Distention of compliant vessels, leading to recruitment of more pathways.
More blood = more recruitment = more pathways = larger parallel system = lowers PVR
This occurs as right heart CO increases. Important because this pulmonary compliance keeps the load on the right heart in check.
In regard to blood flow, what quality does zone 2 have?
Pulsatile
In regard to blood flow, what quality does zone 3-4 have?
Continuous
In regard to blood flow, what quality does zone 1 have?
Large area of the lung isn’t being used/perfused/ventilated.. won’t have as much blood flow as zone 2-4. It’s not one big chunk of tissue though, it’s spots here and there that aren’t perfused as much.
i.e. about 1/3 of alveoli are exchanging air. If you inhaled a bunch of diesel fumes, probably good to not wipe out all of your alveoli all at once
What is the atmospheric pressure at sea level?
760 mmHg
What is the pressure that drives gas movement into the alveoli related to?
Atmospheric pressure
What is the conversion between TORR and mmHg?
1:1
i.e. 760 mmHg atmospheric pressure = 760 TORR
What impact does altitude have on atmospheric pressure?
Higher altitude = less atmosphere above us = less weight of atmosphere above us = lower atmospheric pressure at altitude
Conversely, lower you are –> more atmosphere is above us –> higher pressure (like gold mines in South Africa)
What is the O2 % of atmospheric pressure?
21%
What is the N2 % of atmospheric pressure?
79%
What is atmospheric pressure a product of?
gravity
Several miles of atmosphere above us.. that has a weight.
Weight of pile of gas = atmospheric pressure
What two things do you absolutely have to have to get gas into the body?
Gas
Pressure
Without one of these two -> no gas exchange
The total of partial pressures of atmospheric pressure will always equal what?
100%
What is the CO2 % of atmospheric pressure?
Bonus: what is it used for?
0.04%
Plants use it, store it, release oxygen for us to mouth breathe
What three abbreviations for concentration can we have? (i.e., 79% concentration of N2)
[79%]
0.79
F = 79%
How do you obtain the partial pressure associated with each gas in atmospheric pressure?
Multiply whatever the atmospheric pressure is that daddy gives you x % concentration of the gas you’re looking for.
i.e. 760 mmHg x 79% N2 = 600.3 mmHg
Does composition of the atmosphere always stay the same?
Mostly - changes at very high altitudes.. for our purposes, use table on lecture 5 slide 42
Pulmonary arterial capillaries have a PO2 of ___ and a CO2 of ____
PaO2 = 40mmHg
PaCO2 = 45 mmHg
Note: Deoxygenated
Inspired air has a PO2 of ____ and a CO2 of ___
PO2 = 150 mmHg
CO2 = 0 mmHg
Alveolar air has a PO2 of ____ and a CO2 of ___
Note: Post gas exchange
PAO2 = 100mmHg
PACO2 = 40mmHg
Pulmonary venous capillaries have a PO2 of ____ and a PCO2 of ____
PvO2 = 100mmHg
PvCO2 = 40mmHg
Note: Oxygenated
On average in a normal patient, how much does PaCO2 drop between pulmonary arteries and veins?
5mmHg
Why is alveolar PO2 lower than inspired air PO2?
Also, why is alveolar PCO2 higher than inspired air?
FRC (3L) air mixing with inspired air in alveoli gives diluted numbers. Also, gas exchange occurs.
Of our 500mL tidal volume, how much is dead space? How much makes it to the lungs?
Therefore, what is the total amount in the lungs at the end of a normal inspiration?
200mL dead space
300mL makes it to the lungs
FRC = 3L
3L + 300mL =3.3 L makes it into the lungs at the end of a NORMAL inspiration.
On average in a normal patient, how much does PaO2 rise between pulmonary arteries and veins?
60mmHg
Why does PaCO2 only drop 5mmHg when it passes by the alveoli compared to oxygen rising so dramatically?
CO2 is highly soluble in the blood. Oxygen is less soluble in blood, so changes much faster.
After alveolar gas equilibration, what is the PAH2O at standard barometric pressure? (After inspiration but before expiration)
47 mmHg (always!)
After alveolar gas equilibration, what is the PAO2 at standard barometric pressure? (After inspiration but before expiration)
104mmHg
^He said 100mmHg is good for our class, but 104mmHg is MORE accurate.. so brownie points?
After alveolar gas equilibration, what is the PACO2 at standard barometric pressure? (After inspiration but before expiration)
40 mmHg
After alveolar gas equilibration, what is the PAN2 at standard barometric pressure? (After inspiration but before expiration)
569mmHg
A healthy lung will have what characteristics around the alveoli?
Relatively dry, not too much water around it.. Water is a barrier to gas exchange.
How does PAN2 change between inspiration/expiration?
Shouldn’t change very much at all since we don’t use this all that much.
If you have a blocked airway, what happens to O2/CO2?
How does the lung protect itself from messing up blood gasses related to the above?
O2 will decrease
CO2 will increase
Pulmonary arterial capillaries constrict to drive blood to different alveoli that are actually being ventilated.
What is another way to write out PAO2?
Alveolar PO2
These are the same things, just written differently
Label the pulmonary capillary.
C
Embedded in the wall of the alveoli right next to where the air is.. not much space between them in a healthy lung, which this is
What are V/Q matches due to?
Pleural pressure gradient.
Pleural pressure is more negative at the top of the lung, and more positive at the base of the lung.
This means Transpulmonary pressure (PTP) is higher at the top of the lung than the bottom of the lung.
Higher transpulmonary pressure at the top of the lung results in what?
More distended alveoli at the top of the lung. As the alveoli fill up, they start to resist further filling. This leads to more air making it deeper in the lungs later on inspiration.
Why are blood vessels at the base of the lung larger than at the top of the lungs?
Development - we spend out lives upright (hopefully), leading to vessels developing more at the bottom of the lung. A person, upright at FRC will have most of their blood directed to the base of the lung.
Alveoli at the top of the lungs are larger than the base of the lungs.
What is transpulmonary pressure?
PTP
Alveolar distending pressure, aka pressure available to help get air into the lungs
If PA (pressure in the alveoli) is 0 mmHg, what is the pleural pressure at the base of the lung? (At FRC, upright lung)
-1.5 cm H2O
A transpulmonary pressure of +1.5 cm H2O at FRC at the base of the lung can fill the lungs to ____ of capacity. (upright lung)
25% capacity
How is PTP found?
PA - PIP = PTP
For example, at FRC, the base of the lung is 0 cm H2O - -1.5 cm H2O = +1.5 cm H2O
At FRC, what is the transpulmonary pressure (distending pressure of alveoli) at the top of the lung? (upright lung)
+8.5 cm H2O
0 - -8.5 =8.5 +8.5 cm H2O
At FRC, a transpulmonary pressure of +8.5 cm H2O will fill the top of the lung to about ___ capacity. (upright lung)
60%
On the pulmonary ventilation curve, there are two curves. Which is which?
Arrow pointing up and right is inspiration
Arrow pointing down and left is expiration
As we put air into the lungs, the pulmonary ventilation curve flattens out. What does this mean?
Harder and harder to put more air into the alveoli. Pressure increases rapidly as you get closer to max capacity. Toward the top, lots of pressure is added without getting very much air in.
At the top of the pulmonary ventilation curve, is the alveoli compliant or no?
No
At the bottom of the pulmonary ventilation curve, is it compliant or no? What does this mean?
Very compliant
A small increase of pressure results in lots of air entering the lung
What is the relationship between steepness/flatness on the pulmonary ventilation curve?
Steep = compliant; little pressure adds a lot of volume
Flat = noncompliant; LOT of pressure adds only a little volume
Name compliance characteristics of the following:
Top of the lung
Base of the lung
Top - very low compliance
Base - very compliant
Middle - gradient between the two
Note: Air will go where it is most compliant.. so it will go to the base
How does the lung behave differently on inspiration vs. expiration?
What is this behavior called?
Lung is more compliant on expiration.
i.e. takes more pressure to inflate the lung than deflate it.
This is called Lung Hysteresis*
To get down to RV, what has to happen to pleural pressure?
It has to become positive.
Which will have higher pleural pressures - lung at FRC, or lung at RV?
RV
At the top of the lung at RV in a healthy person, the pleural pressure is ___. PTP is ____
-2.2 cm H2O
PA = 0 cm H2O
PA - PIP = PTP
0 - -2/2 = +2.2 alveolar pressure/PTP
At RV, a PTP of +2.2 cm H2O fills alveoli at the apex of the lung to ___% capacity (upright lung)
30%
What is the PTP at RV in an upright lung at the base?
0 - 4.8 = -4.8 cm H2O
At RV in an upright lung, if the PTP is -4.8 cm H2O, what is going on in the lung? What capacity can it be emptied to? Why?
Alveoli are very empty (20% capacity). Any further pushing of air out will only result on airway closure.
At RV in an upright lung, the apex has a pleural pressure of -2.2 cm H2O and a PTP of +2.2 cm H2O. The capacity will be ____%
30% open airways
At RV in an upright lung at the base, the pleural pressure is +4.8 cm H2O and the PTP is -4.8 cm H2O. The capacity will be at ___
20%; lowest alveoli capacity can be collapsed
When someone is at RV, why is it easier to get air into the apex than the base?
The alveoli in the base are collapsed, whereas the apex is not collapsed. To reopen these airways, a breath is initiated –> increase of PTP –> air goes to the top of the lungs –> lung tissue inflates –> walls of alveoli start to stretch out more at the base –> airways open –> air flow occurs
RV at the base of the lung is noncompliant. (Horizontal line)
A person is at RV. The base of their lung is normally a PTP of -4.8 cm H2O. What happens if we increase this to 0 cm H2O?
Nothing. This area has zero compliance and accepts no volume.
Requires pressure of around +5 PTP to start taking in air after upper airways start to fill.
As we take a breath, where does our air go?
How about when we breathe out?
Apex –> Base
When we expire, the base empties out first, then the apex.
If we are missing elastic/connective tissue in the lung, what is the problem?
Can’t pull airways open (and also recoil pressure is diminished)
In an upright patient, imagine if they started at RV.
What is the problem with this?
Upright position = blood is hanging out in base of the lungs. Fresh air goes to the apex of the lung first and requires more pressure to start filling the base, resulting in fresh air not really making it to where the blood flow is.. this would cause VQ mismatch if we did this all the time
Generally, when transpulmonary pressure is increased what happens to lung volumes?
They are increased
What happens when we put someone under GA and paralyze them in regard to airway?
Very low lung volumes
Being supine lets air out of the lungs
Relaxing all skeletal muscles reduces lung volume further
^So does position change
Need pressure to achieve lung volumes (PPV)
When you move from upright to supine, what happens to air in the lungs?
Stuff in abdomen pushes on the diaphragm, slides up, and pushes air out of the lungs
What is FRC when we are supine in a healthy patient?
2L
1L gets pushed out of the lungs when laying down compared to upright.
What happens when someone who is obese lays down compared to someone who is not (regarding lung volumes)?
A healthy person has a reduction of FRC of 1L when supine. This leaves FRC at 2L.
An obese person would have an even lower FRC when supine.
When going from upright to supine, FRC decreases. Which volume(s) are changing?
ERV is reduced when supine.
IRV becomes larger, as TLC remains the same.
VC remains the same.
How do we measure lung capacities?
Pulmonary function lab with a spirometer (Not an incentive spirometer)
How does basic spirometry work? Is there any volume that it can’t measure?
Patient inspires/expires into an upside down air container –> Container bobs up and down depending on volume of air in spirometer –> bell is bushed up, which causes marker to draw a pattern on paper.
This is digital nowadays.
It cannot measure RV. This has to be done with a tracer gas and a fancier setup.
Know how this works.
If someone had a lung that had an excess of recoil pressure (tons of springs), what kind of lung disease would that be? What is the problem?
Restrictive lung disease (i.e. fibrosis)
Lots of recoil, can’t get air in. Smaller alveoli/airways
If someone had a lung that was overly compliant with not much recoil, what would that lung disease be? What’s the problem?
Obstructive lung disease (i.e. emphysema)
Not much recoil, can’t get air out. Airways and alveoli are large
How is pleural pressure written?
P(subscript PL)
At a normal pleural pressure of -5 cm H2O, what would happen to someone with obstructive lung disease?
Restrictive disease?
Obstructive - less tissue resisting filling; volume will be higher
Restrictive - pressure won’t be high enough to get the same volume.. harder to fill with air
What happens if some disease process interferes with surfactant production or release?
Results in higher surface tension in the alveoli, which can lead to collapse & difficulty opening the airways.
What does every lung disease ever discovered/studied have in common?
Surfactant deficiency
What fraction does surfactant play on recoil pressure?
2/3rds
the remaining 1/3rd is due to tissue factors (recoil of alveoli)
What is surface tension? (example used in class)
Water wants to hang around with other water molecules instead of apart, so they stick together.
When it rains, water molecules stick together and form water droplets.
Definition: Force that causes water aggregation
The loss of elastic tissue in the lungs is classified as?
Obstructive lung disease
The loss of elastic tissue in the lungs has what effect when it comes to lung volumes & transpulmonary pressures?
a small increase in transpulmonary pressure will increase greatly increase lung volumes
lung tissue becomes very compliant & has low resistance
The addition of scar tissue making it more difficult for the lung to expand is classified as?
Restrictive lung disease
The addition of scar tissue in the lungs has what effect when it comes to lung volumes & transpulmonary pressures?
An increase in transpulmonary pressure will only slightly increase vital capacity
tissue becomes less compliant & high resistance
Why does water want to hang out with other water molecules (surface tension)?
Water doesn’t like air and prefers to be with other water
In general, is the lung more compliant on a large inspiration or a large expiration?
Large expiration
During inspiration despite an increase in transpulmonary pressure there is a delay in lung volume increasing, why is this? When lung is at RV
The lungs are at really low lung volumes due to initial decreased compliance
What is an amphipathic molecule? How does this come into play in the lungs?
Molecule is partially water soluble, partially lipid soluble
Surfactant is an example with its polar head & hydrophobic tail
Polar bit goes into water, hydrophobic tail aims to the air.. makes an air/water interface, preventing water molecules from sticking together and making droplets, which breaks surface tension. This makes the alveoli easier to fill.
Why does the dishwasher leave spots on it? How can we fix this?
City water has minerals in it. When water evaporates, it leaves behind concentrated mineral deposits.
Using dishwasher rinse agent provides surfactant to disperse the water before it dries, thus spreading out the minerals and making it to where the spots are not visible.
Surprise, your dishes are all dirty!
Goblet cells secrete what?
Mucous
Where are globlet cells found?
Upper airway
What are the secretory cells of the lower airways?
Clara cells (Club)
What do the clara cells produce?
surfactant
What are the cells found in the alveoli?
Type 1 & type 2
Which cell is most abundant in the alveoli?
Type 2
there is x2 as many type 2 compared to type 1
Which alveoli cell takes up most of the gas exchange area?
Type 1 – make up 90-95% of gas exchange area
Type 2 – make up 5-10%
How is surfactant excreted into the alveoli?
Exocytosis
What is the function of type 1 alveolar cells?
Gas exchange
What is the function of type 2 alveolar cells?
produce surfactant
Where does surfactant hang out after it excreted by the type 2 alveolar cell?
Tubular myelin (mesh netting)
What most effectively knocks the surfactant off the tubular myelin allowing it to rise to the water-air interface?
The negative pressure produced in the alveoli during normal breathing
What scavenges bacteria & surfactant to be recycled?
Alveolar macrophages
If surfactant is reduced or a portion of the lung collapses, what affect does this have in terms of opening the lung during ventilation?
surface tension will increase making it more difficult to open the lung despite increasing transpulmonary pressure
Why was the Clara cell renamed to club cell?
Nazi scientist experiments
Aside from goblet cells, Clara cells, alveolar cells (type I & II), what other kind of cell do we have in the lung that is important?
Mast cells - pacman shaped cell that is an inflammation mediator in the lung. It is a secretory cell. It gobbles up pollutants/junk in the lungs.
Why do mast cells cause inflammation? What is the result?
Histamine release
Cause inflammation + airway irritation and tightening of airway smooth muscles.
How many alveoli does a young healthy person have?
500,000,000 (500 million)
Lose these as we age^
Does the lung have a way to produce new alveoli? What is this similar to?
Yes, albeit slowly. If we are young and healthy but happen to lose a lung, we can grow new alveoli SLOWLY.
Similar to the heart.. we have cells die all the time, but cardiac stem cells replace these cardiac cells. Cannot replace cells after a MI fast enough
^Similarly, cannot replace alveoli fast enough in chronic lung disease, you’re just boned
Each alveoli can have as many as _____ capillaries attached to it.
1,000
A 20 y/o healthy adult will have ____ of surface area available for gas exchange in the lungs.
This is roughly the size of a ___ ____.
70 meters squared (70 m2, but 2 is an exponent)
Tennis court
What is a large contributor to compliance of the lungs?
Surface tension
Alveoli have a tendency to recoil on themselves. This is called elastic recoil pressure. What is the abbreviation?
PER —- ER is a subscript
Elastic recoil is a pressure that ____ air ____ the lungs
Pushes
Out of
How is surfactant disbursed?
When air is brought into the alveoli, surfactant is knocked off the mesh (tubular myelin), swims up to the air water interface. Note that the mesh is in the water at baseline.
The polar head is in the water, lipid tail in the air - breaks surface tension in the lungs and makes it easier to fill with air.
Aside from breaking surface tension, what does surfactant do? How?
Keeps our lungs dry.
As we stretch alveoli, the water layer is made thinner. Surfactant makes the air/water interface and makes the water layer very thin, making for easy gas exchange
What is the most important phospholipid component of surfactant? What about the second?
Dipalmitoylphosphatidylcholine (31%) is the most important
Unsaturated phosphatidylcholine (31%) is the second most important
What are the steps of making surfactant + recycling it?
Creation of substrates (Surfactant proteins + Phosphatidyl groups) has to happen first within the type II alveolar cell
^ 1) substrate
2) Synthesis in ER
3) Golgi apparatus
4) Lamellar body
5) Exocytosis of surfactant into the alveolar space
6) Surfactant rests on the tubular myelin sheath in the water of the alveoli
7) Air enters lungs, knocks surfactant off the mesh. Surfactant swims over to the surface and makes a monolayer, air-liquid interface. This breaks surface tension and allows for easier air filling and gas exchange.
8) eventually, alveolar macrophages gobble up remnants of broken down surfactant, and some components are reuptaked into the type II alveolar cell.
Elastic recoil pressure is most dependent on what first, then second?
Most dependent on surface tension
Secondly, tissue factors (recoil of tissue itself)
Usually, surface tension is managed by the body pretty decent. What variable do we see a difference with in chronic lung conditions?
Elastic tissue factor, assuming surfactant system is working appropriately
What can influence airway resistance?
lung volume
Lung volume is related to airway resistance. How? Why?
higher volumes = low resistance
Low volumes = high resistance
Low volume alveoli also have a smaller diameter airway, making it more difficult to fill.
High volume alveoli have a large diameter airway, making it easier to fill.
What is the abbreviation Schmidt snuck on the whiteboard for airway resistance?
RAW (AW being a subscript of R)
What did daddy drink in class on 3/4/25
Water, followed by mellow mushroom - David you owe April $5
As you expire forcefully from a low lung volume, what happens to airway resistance and flow?
Resistance is high since low volume alveoli have small diameter airways.
This limits the speed that you can exhale at low volumes.
As you expire forcefully from a high lung volume, what happens to airway resistance and flow?
Resistance is low since high volume alveoli have large diameter airways.
Large airways increase the speed that you can exhale.
In a healthy lung, lung volume plays a big role in what?
Determining blood flow, pulmonary BP, and airway pressures
This slide was repeated like 5000 times, memorize it and know all of the intricacies
LOOK AT IT
What are large airways held open by?
Negative pleural pressure
What are large pulmonary blood vessels held open by?
Negative pleural pressure
The physical pull that negative pleural pressure exerts on airways and blood vessels is called
Traction
Holding alveoli open is more controlled by
volume
Holding large airways open is more controlled by what?
Negative pleural pressure (held open at high lung volumes as a result of negative pleural pressure)
TLC (total lung capacity) in a normal patient requires what pressures?
PTP of +30 cm H2O, which is -30 cm H2O pleural pressure.
This fills the lung with air and applies traction on larger airways to open them.
Traction in the large airways/blood vessels relies on what?
Tethering to other vessels/airways nearby
What is the normal pulmonary artery blood PO2?
40mmHg
(similar to systemic venous blood)
What is the normal pulmonary artery blood PCO2?
45mmHg
(similar to systemic venous blood)
What is the normal arterial blood PaO2?
100mmHg
What is the normal arterial blood PaCO2?
40mmHg
What is the accurate amount of PAO2 in the pulmonary venous blood?
104mmHg
why does the PAO2 drop from 104 to 100mmHg?
Pulmonary venous blood get diluted with bronchiolar mixture
What percent of CO does the circulation of the tissue of the lungs take up?
1%
When do lungs start falling apart?
20 :(
What is a normal Vt?
500mL
The 350mL of air that makes it to the alveoli for gas exchange gets diluted with what?
The 3L of air in lungs
What is the normal amount of air that reaches the lungs for gas exchange?
350mL
What is the normal amount of air that does not make it to the lungs for gas exchange but used to push air forward?
What is referred to as?
150mL
dead space
What is the term for used for the over all dead space in the lungs?
Physiologic dead space
What are the two types of physiologic dead space?
Anatomical dead space & Alveolar dead space
What is anatomical dead space?
the last 150mL of ventilation that does not make to the lungs for gas exchange – it stays in the conducting zones of the upper respiratory system
What is alveolar dead space?
patch of lung tissue that is ventilated but not perfused – found in unhealthy lungs –> the more unhealthy you are the more alveolar dead space you have
What kind of pressure can cause alveolar dead space?
Positive pressure
What does Vt consist of?
Both alveolar ventilation & dead space
Vt = VD + VA
What is the normal breaths per minute for dad’s class?
12 BPM
What is the formula for minute ventilation?
VM = VT x BPM
What is the normal minute alveolar ventilation?
12 x 350mL = 4.2L/min
What is the normal minute dead space ventilation?
12 x 150mL = 1.8L/min
What is the normal total minute ventilation?
4.2 + 1.8 = 6L/min
What is the calculation for dead space?
1mL/lb of ideal body weight
If we increase ventilation how will it affect alveolar PO2?
it will increase
If we decrease ventilation how will it affect alveolar PO2?
it will decrease
If we increase ventilation how will it affect alveolar PCO2?
it will decrease
If we decrease ventilation how will it affect alveolar PCO2?
it will increase
What is the normal pulmonary capillary pressure?
7mmHg
What is the normal blood oncotic pressure
28mmHg
What is the hydrostatic pressure in the interstitium of the lungs?
-8mmHg
Why is the interstitial in the lungs more negative compared to the systemic?
The lungs are surrounded by a negative pleural pressure of -5 plus the lymphatics pull is -3 –> totals to -8mmHg
What is the normal interstitial protein osmotic pressure?
14 mmHg (double periphery)
What is the total filtration of the pulmonary capillaries?
+1mmHg
29 - 28 = 1
What is the pressure the left atrial can go before it becomes a problem for the lungs?
23mmHg
What is the biggest risk for imbalance that can cause pulmonary edema?
Blood loss with unreplaced colloids & left heart failure
if someone is young & they wake up & try to breath but they airway is closed, what can happen?
They can take in a breath strong enough to make the pressure in the chest really negative that can cause flash pulmonary edema
The alveoli at the top of the lungs are larger than the alveoli at the bottom of the lungs, why is this?
The spend more time full so they end up being physically larger than the alveoli at the base since we spend most of our time upright
on average what is the normal pleural pressure?
-5cmH20 (between -1.5 to -8.5)
What is the lung attached to at the mainstem?
Hilum
The lung sitting on the diaphragm pushes against it, how does this affect the pleural pressure at the bottom of the lung? What is the pleural pressure at the bottom of the lungs?
it makes it more positive
-1.5 cmH20
The the apex is hanging down, how does this affect pleural pressure? what is the pleural pressure at the top of the lungs?
it makes it more negative
At FRC what is the percentage of fullness at the apex of the lungs?
60%
At FRC what is the percentage of fullness at the bottom of the lungs?
25%
Where will air having a tendency to go, the top or the bottom of the lungs?
Bottom as the base of the lungs are only 25% full, which allows them to have more compliance compared to the apex
What is the lower end percentage of how empty the alveoli can get?
20%
Why can the alveoli not get completely empty?
at 20% the small airways collapse trapping air in the alveoli
