Exam 3 Flashcards
1
Q
The numbers for pulmonary arteries are synonymous with systemic arteries or veins?
A
Systemic veins. So, pulm arteries and systemic vein will have a PaO2 of 40mmHg and a PaCO2 of 45mmHg. The pulm veins and systemic arteries will have a PaO2 of 100mmHg and PaCO2 of 40 mmHg,
2
Q
Alveolar interdependence is also known as ___.
A
Alveolar dependence or association
3
Q
Define alveolar interdependence.
A
The function of one alveolus will be related/dependent to the ones around it. **Google: As alveoli are inter-connected, any alveolus tending to collapse will be held open, because it will be supported by the walls of adjoining alveoli; this interaction between alveoli is termed interdependence.
4
Q
What happens if the alveolar connections between them aren’t present or the tension isn’t taught enough?
A
Normally things work very orderly; filling up one portion of the lung tends to fill up the area of the lung around it. If the connections aren’t working right, then we have problematic areas of the lung (ex. COPD).
5
Q
Our tidal volume has is split into what 2 compartments? What are their volumes?
A
Gas exchange (VA)= 350mL Dead space (VD) = 150
6
Q
Alveolar ventilation (VA) + Dead space ventilation (VD) = ___
A
Tidal volume (VT) *Normal: 500 mL for VT, 350 mL for VA, and 150 mL for VD per breath.
7
Q
What does dead space air look like?
A
That should look close to what the patient is inspiring, minus the fact we have some humidity added to it. Remember, it doesn’t undergo gas exchange, so it should be similar to the composition of the atmosphere patient is breathing in.
8
Q
The air that initially comes out of the patient upon expiration has what type of composition?
A
It should be similar to the dead space air; since dead space doesn’t undergo gas exchange, its composition should be very similar to the air they inhaled/atmosphere. So, it should have close to 21% oxygen and very little CO2.
9
Q
After we’ve expired a large portion of dead space air, the air that comes out of the patient after that looks really similar to ___ air.
A
alveolar
10
Q
What are the pressures of dead space for O2, CO2, N2, and water vapor?
A
O2 149mmHg CO2 0.3mmHg N2 564mmHg H2O 47mmHg
11
Q
What are the pressures of alveolar air for O2, CO2, N2, and water vapor?
A
O2 104mmHg CO2 40mmHg N2 569mmHg H2O 47mmHg
12
Q
Alveolar gases look similar to what other gases in our body?
A
Systemic arterial blood gases (PAO2 = 104, PaO2 = 100. PACO2 = 40, PaCO2 = 35=45)
13
Q
__ is the state of the gases in the alveoli after we’ve had gas equilibration between air in alveoli and the pulmonary capillary blood.
A
PAO2 (alveolar gas)
14
Q
___ describes the difference in PAO2 and PaO2 when things are unhealthy in the lung.
A
alveolar arterial difference
15
Q
Formula for partial pressure of a gas.
A
PPgas = [gas] x Ptotal
16
Q
Formula for concentration of a gas.
A
[gas] = PPgas/Ptotal
17
Q
What is the concentration of PACO2 if we know that PACO2 is 40mmHg and we are at sea level?
A
PPgas = [gas] x Ptotal PPgas/Ptotal = [gas] 40mmHg/760mmHg = 5.3%
18
Q
If concentration of PACO2 is 5.3%, in each 350mL of expired alveolar air, we have __ mL of CO2.
A
VA = Vtotal x PACO2% 350mL x 0.053 = 18mL of CO2
19
Q
We have no CO2 in 150mL of dead space and about 5% CO2 in 350mL of alveolar air. So, the total volume of expired air on each breath should be 500mL. Of that, there is __ mL of CO2.
A
18.42 mL
20
Q
We have no CO2 in 150mL of dead space and about 5% CO2 in 350mL of alveolar air. So, the total volume of expired air on each breath should be 500mL. Of that, there is 18.42 mL of CO2. How much CO2 do we exhale each minute with RR of 12?
A
221.05mL
21
Q
If we expired 220 ccs of CO2 per minute, how much CO2 are we inhaling?
A
about 200-250 ccs of oxygen (We have to absorb the about the equivalent amount of oxygen to make up for the gas exchange. It depends on what your diet, metabolism, fitness level, etc.)
22
Q
What is the respiratory exchange ratio?
A
Comparison between the amount of CO2 that is expired with the amount of oxygen that is absorbed.
23
Q
If you have a major MI, what can happen to your expired CO2?
A
It will decrease. That results in CO2 building up in the patient and they are acidotic
24
Q
Why do we see an upslope on our end-tidal capnograph waveform?
A
Because the concentration or partial pressure of CO2 of expired air tends to increase a little bit over the duration of the expiration.
25
What does VE stand for?
total minute ventilation, the sum of all of our tidal volumes all put together
26
What does the black dot over VT or VA or VD mean?
Putting a dot over each of the variables implies tidal volumes, dead space air, or alveolar air over the course of a minute.
27
How does PPV affect the right heart?
The R♥ has to push all the blood through these lungs. If there is a ton of positive pressure pushing on the blood vessels, that will really make things difficult for the R♥ because of the increased workload. So, use the lowest possible pressures!
28
At FRC, where in the lung does the majority of fresh air preferentially go to first?
Majority of fresh air preferentially goes to the areas of the lung that are most compliant, where alveoli are less full, and has the most blood flow. This would be the base of the lung.
29
On the pulmonary ventilation curve, what does the slope of the curve represent?
Compliance (The steeper the slope, the more compliant. The flatter the slope, the less compliant.)
30
At FRC, is the top of the lung more or less compliant than the base?
The apex of lung is less compliant. The base of lung is more compliant.
31
How does pleural pressure affect the fullness of alveoli?
The more positive the pleural pressure, the emptier the alveoli. The more negative the pleural pressure, the fuller the alveoli. **Note how alveoli at apex of lung (PPL = -8.5) at FRC is significantly larger than at the base (PPL = -1.5).
32
Pleural pressure gradient in the lungs are driven by ___.
gravity
33
Is the alveoli at the base of the lungs fuller/larger at FRC or RV? At the apex?
At FRC, the alveoli at the base and apex are both larger than the alveoli at the base and apex of the lung in RV, respectively.
34
Comparing the two together, the alveoli at the base of the lung are only ___% less full than the base alveoli at FRC.
5% (The way we have that 5% pushed out of the alveoli is we have applied positive PPL to push that 5% out of the alveoli.)
35
Why can't we drop our alveolar fullness any lower than 20%?
Because there is only so much air we can squeeze out of our alveoli before the small airways leading into that alveoli collapse.
36
What happens to alveoli and alveolar pressure when we forcefully expire as much as possible?
When we forcefully expire, this is going to push on the alveoli to help it empty out by pressing on the walls of the alveoli and make PA positive, which will push the air out.
37
When we forcefully expire, how does that affect the small airways leading into the alveoli?
If we push on these hard enough, some of this pushing pressure has a potential to push on the airway, which, at some point, will collapse the airway and prevent us from getting any more air out.
38
If pleural pressure at the base of the lung at RV becomes more positive, what happens to the fullness of the alveoli at the base?
If we push any harder, and make PPL more positive than +4.8 at the base of the lung, it doesn’t change the fullness of the alveoli at the base of the lung at all. The most empty the alveoli can get is 20%!
39
What alveoli will have the potential to become trapped depends on ____.
Lung volume. **If we are at a really high lung or alveolar volume and we push on this (more positive pleural pressure), we are going to be able to get quite a bit of air out of here.
40
True or False. When we have high lung or alveolar volume, the small airway is basically a continuation of the alveolar unit.
TRUE **So, if we have a fairly high alveolar volume, then the attached airway will be really wide!
41
If the alveolus has been pulled open by negative pleural pressure or forced to accept volume in here, the small airways tend to do what?
The small airways tend to widen as alveoli fill with volume. **Remember that the small airways are like a continuation of large alveolar units!
42
Explain why larger/fuller alveoli are less likely to collapse than smaller/emptier alveoli.
Larger alveoli will have larger/wider airways attached to them. Smaller alveoli have smaller/more narrow airways, which make them more likely to collapse.
43
What is the pleural pressures at the apex and base of the lung at RV?
Apex: -2.2 Base: +4.8
44
The higher the transpulmonary pressure, the higher or lower the alveolar volume %?
Higher **Remember PTP is essentially opposite of PPL. So, The higher (more positive) the PTP, the lower (more negative) the PPL, the higher/fuller the alveolar volume %.
45
Describe PTP and PPL on expiration.
On expiration, we are pushing air out of the lungs/alveoli. So, PTP will be lower (more negative) and PPL will be higher (more positive).
46
The alveoli at the top of the lung at RV are more empty than they were at FRC. Why?
At FRC, the PPL at the top is -8.5 and at RV it is -2.2. RV's pleural pressure is more positive, meaning there is isn't as much pressure to hold the alveoli open or fill them up!
47
At RV, the alveoli at the apex of the lung is ___% full.
30% So, at RV: apex is 30% and base is 20% of total possible capacity.
48
True or False. If we have a PPL of anything that is positive or if we have a PTP that is negative, that would give us the ability to put a little bit more air into alveoli.
False! Putting air into the alveoli (inspiration) would require PPL to be negative and PTP to be positive.
49
Where in the lung are alveoli more compliant at RV?
The apex
50
When we are at really low lung volumes (RV) and inspire, where in the lung will the fresh air preferentially go to first? Why?
The apex, because at RV, the apex has more compliance than the base of the lung--easier for air to go there.
51
Describe the compliance of the base of the lung at RV.
The slope is essentially flat; zero compliance! If we were to increase PTP from +4.8, we would get no volume into the lung for quite a while. If we make PPL 0, we still wouldn’t have a whole lot of air coming into the base of the lung. We would have to actually get all the way over to somewhere around here [pointing/arrow] until we get any air coming into the base of the lung.
52
If we are changing transpulmonary pressure without any change in volume to the alveoli, what is the compliance?
ZERO compliance (This is what occurs at the base of the lung at RV!)
53
What happens to alveoli if they are collapsed for too long?
They will be difficult to open back up! It will be harder for the alveoli/lung to re-inflate. Eventually, if they are collapsed for long enough then that part of the lung is going to eventually disappear.
54
Is there a difference in tissue characteristic between inflating and deflating the lung?
Yes. Lung volume increases correspond to the curve that is on the right and lung volume decreases (expiration) is the curve on the left; that is why they have two lines in there.
55
True or False. PTP of 0 would be equal to a PPL of 0. So, PPL of 0 surrounding the base of the lung. We can assume that as soon as we make PPL more negative, we could probably get air into the lungs at that point.
False! If we are working from really low lung volumes and we do have some collapsed areas of the lung, we actually have to apply a little extra pressure just to prop open those airways back up after they collapsed. What we would have to do is make PPL substantially more negative than it is in order for any air to start going into the base of the lung.
56
How much extra pressure is needed to open up a collapsed alveoli?
4-5cmH2O (in a young, healthy adult). More might be required for elderly patients, smokers.
57
How can we prevent alveoli from collapsing?
Using PEEP on the ventilator to keep a little bit of volume in the lungs.
58
If we are at lower lung volumes (RV) and we are still upright, fresh air would preferentially be going to the top of the lung. What happens as we put more and more into the lungs?
It tends to open up the lungs as it goes down. At some point, we will get enough air into the lungs to reopen the base of the lung. When that reopening has taken place, once those airways and alveoli there open back up, then air will start preferentially going to the base of the lung. This is due to the pleural pressure gradient!
59
Significance of alveoli sharing common walls.
These shared walls connect alveoli together, forming continuous pathways for blood to go through. So, if we are able to start putting air into the middle of the lung here, this is going to pull these other connected alveoli open and help get air into the lower collapsed areas of the lung.
60
What happens to alvolar walls in COPD or emphysema?
Some alveolar walls are lost and alveoli get really big; they don’t have the same types of connections that a healthy person has. If we don’t have as many walls that are attached to each other, we can have an issue getting collapsed areas of the lungs to open back up, resulting in a patchy collapse.
61
Pro and Con of using PEEP to keep extra volume in lungs.
Pro: Prevent alveolar collapse Con: Potential circulatory problems in the lungs, R♥ overload/increased workload
62
Why is transpulmonary pressure used rather than pleural pressure when looking at pulmonary ventilation curves?
Because PTP are applicable to normal breathing and PPV, whereas pleural pressure does not necessarily apply to PPV.
63
Looking at PACO2 (alveolar) and PAO2 (alveolar), ____ is dependent on how much ventilation we have.
partial pressure
64
If we were bringing in completely fresh air from the outside with no blood flow, what would our PAO2 and PACO2 be?
If we had no blood flow but plenty of fresh air coming in, we wouldn’t be absorbing any oxygen out of the alveolus. Therefore, the PAO2 and PACO2 should be equal to what is coming in. So, if PO2 coming into the alveoli is 150, then PAO2 should also be 150. If PCO2 coming into the alveoli is 0, then PACO2 is also 0. **Written in blue on drawing.
65
If we were to have no ventilation of this alveolus but we did have perfusion of this alveolus, what would our PAO2 and PACO2 be?
The alveolar PACO2 should be 45 mmHg, the equivalent of PCO2 partial pressure arriving at this location via the pulmonary arteries. PAO2 would be 40 mmHg, again, the equivalent of PO2 of the pulmonary arteries.
66
____ is a way for us to measure a number of our lung volumes and capacities.
Spirometry
67
How does a spirometer work?
There is an upside down tank that is pretty full of air, with an opening at the bottom of the tank. The patient is connected by a tube to this machine and as they inspire and expire, the quantity of air inside of the upside down water heater it changes. With inspiration, the tank moves down because it is drawing air out of the tank, sucking in the water. With expiration, it fills the upside down tank with more air, pushing the tank up.
68
What does a large tracing mean on a spirometer?
Large tracings signify more movement, greater inspiratory and expiratory volumes.
69
Normal spirometer can calculate all lung volumes and capacities except?
Residual volume. Therefore, spirometers cannot measure total lung capacity or functional reserve capacity.
70
Patient is hooked up to a spirometer and takes a deep breath and exhales as much as possible. What did the spirometer record?
The patient's vital capacity (VC = TD + IRV + ERV)
71
Is emphysema an obstructive or restrictive pulmonary disease? COPD?
Both are obstructive airway disorders, associated with the loss of elastic tissue and some of the elastic tissue not being connected very well on the inside of the lungs.
72
What lung volumes differ in obstructive lung diseases compared with normal? How are they different?
With obstructive lung disease (ex. Emphysema, COPD, etc.), we can see more than a doubling in the RV vs someone who is completely healthy. Also, they would have a smaller ERV.
73
What do we need in addition to a spirometer to measure residual volume?
We would need extra attachments to it and an indicator dilution setup.
74
4 qualities of an ideal indicator for measuring residual volume.
1. cheap 2. non-reactive 3. non-toxic 4. not absorbed in blood stream
75
The most commonly used indicator for spirometers is ___.
Helium, because it is fairly inert, doesn’t react with a whole lot of stuff, doesn’t explode when it is exposed to flame, and is probably one of the cheapest of the noble gases.
76
List the noble gases. (6)
1. Helium 2. Neon 3. Argon 4. Krypton 5. Xenon 6. Radon
77
____ is a noble gas but can actually be radioactive.
Radon
78
Outside of smoking, ___ is the most common source of lung cancer.
Radon (A lot of people ran radon tests if they had a basement if you someone had lung cancer. Sometimes people look for radon leaking in from the outside.)
79
We don’t want a gas indicator that will be absorbed into the blood stream when measuring residual volume. Why?
We want the indicator gas to stay in the gas form; we don’t want it disappearing. Otherwise, it will screw up our measurements and we won’t be able to keep track of it.
80
When measuring RV/FRC using spirometry and indicator dilution setup, before the test there was 10% helium and only 5% after the test. Why?
During the test, the helium is going to be diluted out because you added more space (patient's breath) in the system.
81
Formula for a concentration.
volume of the compound that we are interested in/total volume
82
If a 10 L container has 10% helium, what is the volume of helium in that container?
volume of the compound that we are interested in (X)/total volume 10% He = [He] Total volume = 10L So, [0.1] = X/10 L → X = 1 L He
83
Before the FRC test, there 10% He in a 10L container. After the test, there is only 5% He. How much is the new total volume of the container? What does the difference between the original and new volume mean?
Before test: 10% He = [He] Total volume = 10L So, [0.1] = X/10 L → X = 1 L He After test: 5% He = [He] Total volume = Y So, [0.05] = 1L He/Y → Y = 1 L/0.05 = 20 L So, the amount of volume that is in the patient is the difference—10 L of air in the patient.
84
We would expect composition of dead space gas to look pretty close to what we are ___.
inspiring
85
The gas that is in the lung after equilibration is going to have some ___ that is missing and some ___ that it didn’t have on the way in.
The gas that is in the lung after equilibration is going to have some oxygen that is missing and it will have some CO2 that it didn’t have on the way in.
86
What we expired during the entire breath, that will be a combo of ___ and ___.
dead space gas and alveolar gas
87
True or False. The amount of air we have in our dead space it is not available for gas exchange.
TRUE
88
If we have a really ___ VQ, that implies our perfusion is absent. If we have a really ___ VQ that means ventilation is absent.
If we have a really high VQ (C), that implies our perfusion is absent and if we have a really low VQ (B) that means ventilation is absent.
89
If we have problems with ventilation, we tend to have alveolar gas that looks like ____. If we have problems with perfusion (C), the alveolar air will look like ___.
If we have problems with ventilation (B), we tend to have alveolar gas that looks like pulmonary capillary blood. If we have problems with perfusion (C), the alveolar air will look like inspired air.
90
Where in the lung do we have the most alveolar oxygen?
The top of the lung, because less oxygen is absorbed from the alveoli at the apex
91
Where in the lung do we have the most alveolar CO2?
The base of the lung
92
PAO2 and PACO2 numbers at the top of the lung? Base of lung?
Apex: PO2 = 130. PCO2 = 30. Base: PO2 = 90. CO2 = a little bit higher than 40.
93
Average PAO2 and PACO2
PAO2: 40 PACO2: 100/104
94
Alveolar gas distribution is due to ____.
gravity **it will affect which regions of the lung get certain amounts of blood flow and also dictates which areas of the lung will see fresh air coming in.
95
The V:Q ratio tends to increase exponentially as we get closer to the ___ of the lung, which is what gives us our alveolar gas gradient that we see at the different levels of the lung.
Apex
96
How does fresh air in the trachea look?
That would basically be inspired air numbers PO2 150 saturated with water and no CO2.
97
What does V with a bar/line on top of it represent?
represents systemic venous blood that is being returned to the right side of the heart.
98
Systemic venous blood would have a PCO2 of ___ and a PO2 of ___.
a PCO2 of 45 and a PO2 of 40.
99
We have a mixture of both dead space air and alveolar air coming out of the patient at the same time, but the mixture will be depend on what?
It will depend on where is the gas predominantly coming from.
100
How does V/Q matching change with age?
We have worse VQ matching as we get older. If we look at what is happening with ventilation, it is quite a bit more spaced out.
101
As we age, ventilation doesn't match up well with perfusion. Why?
Oftentimes this is because we have a little bit more alveolar dead space when we get older. As we age, this usually gets significantly worse and we tend to have more wasted ventilation as we get older.
102
Recoil formula.
PER = PA _ PPL. **This is the same formula for PTP.
103
Under normal circumstances the PTP will be primarily affected by what our ___ is and somewhat affected by what the ___ is.
Primarily affected by PPL. Somewhat affected by PA.
104
At the end of inspiration, if no air is moving, what is our PA, PPL, PTP, and PER?
PA = 0. PPL = -7.5 cmH2O. PTP = +7.5 cmH2O. PER = +7.5 cmH2O.
105
If we were to think about elastic recoil pressure at end of expiration but before beginning of next inspiration, our PTP would be equal to ___.
+5 mmHg **So, if no air is moving, then our PPL is -5 and our PER or PTP have to be +5 cmH2O.
106
As we open this thing up by dropping our PPL, this fills with air and these springs have [more or less] tension on them.
more
107
If we have fewer springs/less elastic recoil, it becomes difficult for us to empty lungs because of _____.
small airway collapses
108
With fibrotic lung diseases, what happens is it becomes more difficult to do what?
fill alveoli/lungs with air
109
If we think about the PER/tension of a [fibrotic or obstructive] lung, it has a whole lot more tension than a normal lung.
fibrotic
110
Which has more elastic recoil pressures: restrictive lung disease or obstructive lung disease?
Restrictive (fibrotic) has a lot more tension.
111
Elastic recoil depends on what 2 things?
the stretch of the alveoli and how many springs are in each of the alveoli
112
Flow volume loops, as a pulmonary function test, is usually looking at what?
Air going in or out of the lungs over a period of time.
113
What part of each breath is seen on the top and bottom halves of the flow volume loop?
Top half: expiration Bottom half: inspiration
114
The maximum rate of expire air can be out of a reasonably average adult.
10 L/sec
115
If we are dealing with someone who is super healthy, 20yo and they work out a lot, at the more extreme end of the scale, someone might be able to get a flow rate up to ___.
15 L/sec (very fast!)
116
True or False The max inspiratory flow rate is usually substantially higher than 10 L/sec.
False **Max inspiratory flow rate is substantially LOWER. Generally, what we usually see is a really high forced expiratory flow rate.
117
Patient exhales as much as possible and inspires as much as possible. What lung volumes/capacities are we measuring?
Expire as much as possible leaves us at RV. Inspiring as much as possible gets us to TLC. So, from RV to TLC, we are able to calculate the VC (maximal working volume).
118
Normal vital capacity.
4.5L
119
Other than volume and flow rate, what can affect how the flow loop looks?
The amount of effort applied.
120
How would flow loop appear if we apply maximal effort vs minimal effort?
Maximal effort flow loop would be larger in height, so the flow rate would be at greater ends. Minimal effort flow loop would be smaller/shorter; flow rate would be lesser.
121
Which part of the flow loop appears more symmetrical, the top half or bottom half? Which part of respiratory cycle is this?
The bottom half is more symmetrical, which is inspiration.
122
When doing flow loops as a PFT, why do we look at maximal inspiration or maximal expiration?
Those are typically the places where we could run into problems if problems exist. If there is something that can obstruct the airway during inspiration, it is most likely to happen when we are applying the maximal effort. Likewise, if there is something in the system that is going to block expiration for any reason, it is most likely to do that when we are using maximal amounts of effort.
123
How would flow loop appear in someone with fibrotic lung disease?
Fibrotic lung disease would cause smaller VC, so the flow loop would be more narrow.
124
Why is the expiratory/top half of the flow loop not symmetrical, like it is for the inspiratory/bottom half?
During peak forced expiration, we start off with alveoli and airways that are really open and stretched out at the very beginning of forced expiration. Once we apply a lot of effort to expire air as fast as possible, there is a very short period of time where the air just sits there as you are applying pressure. So, we have that initial inertia that we have to overcome.
125
Why is peak expiratory flow rate significantly higher than the peak inspiratory flow rate?
Because we are usually able to generate a ton of more positive pressure in our pleura or thorax compared to the maximal negative PPL that we can create using our muscles for inspiration.
126
How much PPL can we generate during inspiration and expiration?
We can probably generate +25 to 35, if not higher with expiration. On inspiration, we might be able to get the same range, just the pressures being negative (-25, -35).
127
During expiration, in addition to the PPL we can generate, we have additional pressure that helps us get air out of the lungs, which is our ____ pressure.
recoil pressure **this PER provides us additional force on top of the PPL to move air out of the lungs very quickly.
128
True or False The PER becomes much more positive the more air we put in the lungs.
TRUE
129
Where would FRC be found in the flow loop?
Going from RV to TLC, the FRC would be 1/3 of the way through.
130
What does "effort independence" mean?
No matter how hard we push, we aren_t able to increase the rate at which air is coming out of the lungs. The place where that starts to happen is where the lung is starting to empty out and has gone through some of that recoiling of alveoli and small airways.
131
If we are at a very high lung volume, it is relatively easy to get air out of the lungs because our airways are open. What are the 2 reasons why alveoli are able to stay open.
1. These will be supported and pulled open by some of the tethers/connections to the interstitial tissues in the lungs. 2. A big portion of the pressure on the inside of the alveoli and airway is coming from the elastic recoil pressure. When we have PER in here, that is going help keep the pressure inside these conduits higher than PPL.
132
Alveolar pressure is a combination of what 2 pressures?
Elastic recoil pressure and pleural pressure. So, if PPL is +25 and PER is +25, then PA = +50.
133
True or False If we are forcing air out of the lungs, then pressure will be highest in the alveoli.
TRUE
134
If the pressure in our airway is [higher or lower] than the pressure in the pleural space or the thorax, it will withstand collapse.
higher
135
As we get to lower and lower lung volumes, what happens to alveolar tension/recoil?
Recoil tends to be reduced **PER becomes smaller the smaller our alveoli are.
136
If we have a reduction in pressure in a way that drops our small airway pressure lower than our PPL, we have the possibility of ____.
small airway collapse **If we have an internal small airway pressure that is lower than PPL, we are running the risk of small airway collapse because our forced positive PPL is potentially higher than the small airway pressure.
137
If we were to increase our PPL to levels that are above 25 or 35, that thoracic pressure wouldn_t necessarily move air out of the lung any faster. Why?
More pressure is just going to collapse the small airway. So, there becomes a point when our effort or amount of PPL we are generating is not sufficient enough to push air out of the lungs in a faster clip when we have smaller lung volumes and potentially less built-in tissue elastic recoil.
138
Why do we not generally see small airway collapses at higher lung volumes?
Because at really high lung volumes, we have a lot of elastic recoil normally and our airways are really wide. So, there, we don_t really run the risk of collapse at the very beginning of forced expiration.
139
The effort independence things happen in normal healthy lungs once we get down to about ___.
FRC *With unhealthy lungs, they tend to run into this problem earlier.
140
When we have disease that is ___ in nature and an abnormal lung compliance, that is going to increase our effort independent expired flow rate.
Obstructive
141
How much PTP do we apply to get a normal healthy lung from RV to TLC?
25-30cmH2O
142
How much PTP do we apply to get an obstructive diseased lung from RV to TLC?
10 or 15cmH2O the most **These lungs were easier to full up to TLC because they were stretchy and they didn_t have as many springs.
143
At TLC, our obstructive lung disease is going to cause a [increase or reduction] in the amount of elastic recoil have in our alveoli.
reduction **Normally the recoil is +25 or +30. If we have an alveoli that is coming out of a lung that has emphysema, their recoil at TLC might be between 10-15 cm H2O.
144
The difference between the lung tissues with ___ lung disease is that they just don_t have as much internal recoil tension to keep small airways/alveoli open as we are trying to force air out of the lung during a maximal effort forced expiratory maneuver.
Obstructive
145
We run into a cap in our maximal expiratory flow rate with obstructive lung disease. Why?
Because we have the potential for our small airways to collapse at really early times into the expiratory maneuver. This peak tends to be a lot lower.
146
How would the flow loop appear in obstructive lung disease?
Depending on what their VC is, it could be normal, expanded or smaller depending on where they are in the disease. If they are at end stage, barely holding on, then their VC will be really small. If they are at an earlier stage, it could look normal or larger than normal.
147
How does the inspiratory half of the flow loop appear with obstructive lung disease?
The bottom half would look normal because when we are inspiring, we are still pulling on this whole thing evenly.
148
Higher up the lungs towards the trachea, how does the pressure change?
The numbers would keep getting lower the closer we got to the trachea. So, PA could be +35 and the trachea would be 0.
149
If pressure higher up in the tracheobronchial tree is lower, what prevents those areas from collapsing?
At some point we will have some structural support from cartilage and things that are in the airway to keep it open as we get closer to the trachea. If we have a PPL pushing on this, it doesn_t really matter what the internal pressure is if we have enough structural support to prevent it from collapsing.
150
Why would a high compliance lung be at greater risk for collapse than a normal lung?
Higher compliance lungs (ex. COPD, emphysema) have a lack of internal elastic recoil pressure support in the alveoli and connecting small airway. So, risk for collapse is greater.
151
3 sets of muscles used for forced expiration, to get really high PPL.
1. abdominal muscles (rectus abdominis) 2. Obliques 3. Internal intercostals.
152
If we obstruct airway with pursed lips, how does the pressure in trachea change? What would the pressure gradient then be?
If we obstruct the outflow, we could keep the pressure at the pursed lips of maybe +10 up until where the air is leaking out. If we increase this pressure here, that is going to increase all of the pressures in that gradient. So, instead of it being a 30 to 0 gradient, we might have 30 to 20 gradient.
153
Does pursed-lip breathing [increase or decrease] resistance of air getting back to the outside environment?
Increase **If we increase resistance of this thing getting to the outside environment, we can maintain a higher pressure in our small airways and help us empty our lungs to get more old air and more fresh air in.
154
How does the inspiratory half of the flow loop of restrictive lung differ from normal?
With restrictive lung disease, we have a problem with peak expiratory flow rate because we can_t get as much air into the lungs as we normally would; we tend to have a lower than normal peak expiratory flow rate. VC also tends to be lower, so it is more narrow.
155
How does the inspiratory half of the flow loop of obstructive lung differ from normal?
RV is about 4.75 L. TLC is quite a bit higher (8.5 according to this). VC is 3.5 L, probably a little bit more. The peak expiratory flow rate is going to be substantially lower than normal because we are running into problems with collapsed airways very soon into the event.
156
The closing capacity test measure what lung capacity?
They are using a VC breath, the largest possible quantity of air we can move in and out of the lungs.
157
As far as the dead space gas is concerned, it should look really similar to inspired gas. What would O2, CO2, and water vapor levels be?
O2: 149mmHg CO2: 0mmHg H2O: 47mmHg
158
The difference between the air we absorb and the air we inspire is what will undergo ____.
gas exchange
159
For our PACO2, there isn_t any coming in, but we add about ___% CO2 into the alveolar air that we expire.
5%
160
What kind of gas does capnography measure?
expired gas mixture
161
If we are looking at expired air, the oxygen coming out of alveolar air should have partial pressure of ___; partial pressure of oxygen in dead space air should be ___ mmHg.
alveolar air: 104mmHg dead space air: 150mmHg
162
Gas gets diluted out during which part of expiration?
The latter half; the early portion of the expired breath looks similar to what came in.
163
All the air that is doing that dilution of the CO2 is coming from the ____ portion of the expired air.
dead space
164
After we allow dead space and alveolar air to mix, we should see a CO2 that is [higher or lower] than our alveolar concentration (VA) and [higher or lower] than our dead space concentration (VD)
CO2 is lower than alveolar concentration ; CO2 is higher than dead space volume **the dead space air is going to dilute out whatever CO2 is in the alveolar air
165
PMECO2 refers to?
partial pressure of mixed expired CO2
166
Formula for concentration of a gas.
[gas] = PPgas / Ptotal
167
What is [CO2] if we have a PACO2 of 40 at atmospheric pressure?
[CO2] = 40/760 = 0.05263
168
What is the volume of CO2 present in alveolar air if we have a PACO2 of 40 at atmospheric pressure?
[CO2] x Volume _ 0.05623 x 350mL = 18.42mL CO2
169
Normal conditions, we have 18.42mL CO2 in alveolar air. How much do we have after it is mixed with dead space?
Volume CO2 / Total Volume _ 18.42mL / 500mL = 3.6841% CO2
170
What is the normal partial pressure of mixed expired CO2 at sea level?
Partial pressure of CO2 = [CO2]xPtotal _ 760 mmHg x 3.6841% = 28 mmHg for the partial pressure of CO2 in the combined container after the alveolar air has been diluted out by the dead space air.
171
Simplest way to analyze CO2 as patient is expiring?
Capnograph waveform
172
We are usually concerned with the PMECO2 concentration or partial pressure being [higher or lower] than normal.
lower
173
If we are dealing with someone who has an expanded dead space volume and normal alveolar volume, how would CO2 levels appear?
Our [PMECO2] concentration and our PMECO2 should be lower (both are basically the same thing; one is just multiplied by the total pressure)
174
Anatomical dead space vs Alveolar dead space
Anatomical: Doesn't really change with age; fixed volume. Alveolar: Represents areas of the lungs that are ventilated but under-perfused or not perfused. We usually don_t have alveolar dead space when we are young and healthy, but as we get older and sicker, it starts to show up.
175
Definition of dead space gas.
Gas that doesn_t participate in gas exchange
176
People with COPD will have a little bit [higher or lower] than normal average VT. Why?
Higher VT, because our body has to make up for a bunch of these extra alveoli that don_t work very well--the increase in dead space.
177
What happens to amount of dead space and mixed expired gas if we have poor perfusion to alveoli?
The more poorly perfused alveoli we have, the more our dead space volume will increase and the more dilute our mixed expired gas will look.
178
Pt has a normal blood gas for CO2 and a lower than normal mixed expired CO2. What does this mean?
That definitely tells us we that have more dead space than we do in the typical patient.
179
What is physiologic dead space?
combination of anatomical dead space plus alveolar dead space
180
How does the body make up for extra alveolar dead space?
increase in VT **Normally that is not really too big of a deal; if the lung is healthy, we just put a little extra air in there and that basically fixes the problem.
181
To increase VT, how does it differ b/t restrictive and obstructive lung dz?
With restrictive lung disease, we might have to push significantly harder because lung doesn_t want to expand. With obstructive lung diseases, we tend to have a problem getting the old volume out to put new volume in.
182
What does it mean if patient has high VT and diluted expired CO2? High VT and higher than normal expired CO2?
If it is being diluted out to a number that is lower than normal, we probably have alveolar dead space. If it is not diluted out higher than normal and have an expanded VT, maybe that gas is being used for gas exchange.
183
True or False An MI would create an increased amount of dead space in our lungs.
True If we don_t have enough perfusion to adequately push enough blood through the lungs, this would effectively create an increased amount of dead space.
184
What could we look at to see if there was a change in patient's dead space while they're vented? (2)
1. Look at ETCO2 2. Look at the mixed expired air
185
When you are doing a long case, the longer the case is, the more ____ will show up.
alveolar dead space
186
Why do you have more alveolar dead space the longer you are on a vent?
If you are using PPV, that is a completely abnormal way of getting air into the lungs, using all sorts of positive pressure and physically pushing things into the lungs. Instead of lungs being pulled open with negative PPL, if we are instead pushing the air into the lungs, then we are basically compressing on blood vessels and parts of the lungs. It will be more difficult to get blood flow through all these blood vessels. By definition, that is creating alveolar dead space because we are putting air in here and it_s not being efficiently used.
187
How does PPV affect lung compliance?
When we are using PPV, that can affect the amount of surfactant we have floating around in the lungs. It can interfere with surfactant release and production.
188
If we have deficiencies of surfactant or if we are just manipulating these tissues in ways that aren_t normally manipulated, we can generate ____.
alveolar dead space
189
PECO2 is normally ___ mmHg.
27 **Schmidt said 26, 27, 28 range
190
If we have the total quantity of all the dead space, the Bohr equation allows us to figure out what?
how much alveolar dead space we have
191
In Fowler's tests, nitrogen concentration early vs late in expiration changes how?
Early, it should be 0. Later on, as we get air from the deeper parts of the lung, the nitrogen concentration goes up.
192
What is the Bohr Equation?
physiological dead space = total of anatomical dead space and alveolar dead space.
193
Volume of CO2 in mixed expired air = ____x____
FECO2 x VT **Fractional expired CO2 (FECO2)
194
Fractional expired CO2 (FECO2) is equal what?
the total volume of CO2 that is related to the different volumes coming from dead space and alveoli.
195
Other than increasing VT, how else can we compensate for alveolar dead space?
Increase in ventilation rate
196
Why does capnograph waveform have a slope on the ETCO2?
After the patient starts to expire, the first portion of expired breath won_t have much CO2, if any, because it is coming from anatomical dead space air. As we get to deeper portion of the lungs, we start to see the alveolar air that has undergone gas exchange. So, we should see a PCO2 coming out of the lungs of 40 mmHg or a little lower starting off. Over the course of the expired breath, the CO2 tends to increase to a point here called the ETCO2.
197
At a normal alveolar ventilation of about ___L/min, we should actually have a PACO2 of about 40 mmHg and PAO2 of ___.
4.2 L/min ; PAO2: 104mmHg
198
The lower our alveolar ventilation is, the [higher or lower] the PACO2 is.
higher **If we have lower than average or lower than normal ventilation to a lung or a region of the lung (left shift), the CO2 partial pressure in those alveoli should be higher than the average normal PCO2 (40).
199
If we have [higher or lower] than normal alveolar ventilation in an area of the lung, we would expect to see a reduction in PACO2.
higher
200
If we have a region of the lung that has a greater than normal alveolar ventilation, our PAO2 will be [higher or lower].
higher **So, if we bring in less fresh air, then our PAO2 is going to be less.
201
At FRC, the ___ of the lung tends to be fairly compliant in terms of the airways and alveoli.
base *The top of the lung at FRC is less compliant and probably more full. If it is already more full, there will be more tension on alveolar walls and will be more difficult to get air into those alveoli.
202
Normal V/Q ratio.
V/Q _ VA/CO = 4.2L/min / 5L/min = 0.84 (close to 1)
203
V/Q ratio for alveoli with no ventilation. V/Q ratio for alveoli with no perfusion.
V/Q ratio for alveoli with no ventilation = 0/5 (infinitely small number approaching 0). V/Q ratio for alveoli with no perfusion = 4.2/0 (infinitely large number)
204
Diff b/t low and high VQ problem.
Low VQ = no ventilation, good perfusion. High VQ = good ventilation, no perfusion.
205
Airway collapse occurs with high or low VQ problem?
Low VQ
206
2 things that can cause high VQ problem.
1. PE 2. MI
207
How would PACO2 and PAO2 look if we have a high VQ problem?
High VQ problem_lots of ventilation and little perfusion. So, if we have a really high VQ problem, we would expect that gas to look like inspired gas: PO2 of 150 and PCO2 of 40.
208
How would PACO2 and PAO2 look if we have a low VQ problem?
Low VQ problem_crappy ventilation but with perfusion. We would expect our alveolar air to look very similar to pulmonary capillary blood gas numbers: PCO2 of 45 mmHg, the PO2 should be 40.
209
At the very top of the lung under normal conditions, we might see a PAO2 of ____. At the base of the lung, it would be ____. Total average would be ___.
Apex PAO2: 130mmHg Base PAO2: 90mmHg Total average: 104mmHg
210
Gradient from apex to base of lung is based on what 2 things?
1. regional ventilation 2. perfusion at different parts of the lung **Most ventilation normally is going to go to the base of the lung; that is where all the blood is going through. In terms of the blood flow, it tends to be quite a bit higher at the base of the lung and the gases in the alveoli will depend on a couple things.
211
With PCO2, we could have a normal range of predicted values going from ___ to ___.
0 to 45mmHg
212
How does blood flow affect how much oxygen is absorbed in alveoli?
If we have a lot of perfusion through alveoli, we will have a lot of O2 absorbed out of that alveolar air. If we have low perfusion through an alveoli, we will have less oxygen absorbed from that alveolar air.
213
2 things that can change alveolar air composition.
ventilation and perfusion
214
If we are looking at the base of the lung, blood flow is really high_we would expect PAO2 to be [more or less] than average.
less **It makes sense that we have a lower PAO2, because we have so much blood flow at the base; we are absorbing lots of O2 from that alveolar air.
215
Alveolar gas at the top of the lung has relatively [high or low] PAO2.
high **less blood flow to the apex, so less O2 is absorbed from that region. Hence, a high PAO2.
216
How does blood flow and ventilation differ from base of lung to the apex?
Base has higher blood flow and ventilation compared with the apex.
217
Which has greater variation: regional blood flow or regional ventilation? Why?
There is more variation in regional blood flow than regional ventilation. Our VQ ratio tends to be significantly higher at the top of the lung than at the base due to greater variation in regional perfusion, which affects the VQ ratio in a way that is a bigger factor than the regional differences in ventilation.
