Lecture 11 (Exam II) Flashcards
(87 cards)
1
Q
- What is anatomical dead space?
- How much of our tidal volume gets trapped in the dead space?
A
- This is the dead space of the conducting zones of the upper airways.
- It is air that is not involved in gas exchange
- We use it as a filler to push the first 350mL of inspired air deep enough into the lungs to be useful for gas exchange.
- volume = 150mL
2
Q
What is dead space air?
A
Any gas that isn’t used for gas exchange
3
Q
How much of our inspired tidal volume makes it to the deep parts of the lung for gas exchange?
A
350mL
4
Q
What is the first and primary type of dead space?
A
anatomical dead space
5
Q
What is alveolar dead space?
A
- This is dead space within the deeper parts of the lung that are involved in gas exchange
- This happens when patches of lung tissue are ventiled but not perfused.
- EX: a PE
6
Q
Every one has ___ dead space, but they won’t have ___ space unless they are sick/unhealthy
A
- Anatomical
- alveolar
7
Q
How does our body work to eliminate alveolar dead space?
A
By directing airflow away from the places that are unable to be perfused and towards the places that are being perfused.
8
Q
What is physiologic dead space?
A
Anatomic dead space + alveolar dead space
9
Q
The healthier you are, the ___ dead space you have.
The more unhealthy you are, the ___ dead space you have.
A
- less
- more
10
Q
What is the consequence of having an increased alveolar dead space?
A
You have to increase ventilation to make up for the fact that air is going to places in the lung where gas exchange isn’t happening
11
Q
True or false:
Positive pressure ventilation can create alveolar dead space during a long procedure?
A
true
12
Q
What is normal minute ventilation?
A
6L/min
* 500mL x 12 breaths per minute
13
Q
What is normal minute alveolar ventilation?
A
4.2L/min
* 350mL x 12 breaths per minute
14
Q
What is notmal minute dead space ventilation?
A
1.8L/min
* 150mL x 12 breaths per minute
15
Q
When we expire what air comes out of our lungs first?
A
- The first 150mL of anatomic dead space gets expired first.
- This is followed by the 350mL of alveolar air that has gone through gas exchange, which now has a different composition from when it entered the lungs
16
Q
True or false:
Inspired anatomic dead space air will have the same O2 and CO2 partial pressures as expired anatomic dead space air
A
True
17
Q
True or false:
Inspired alveolar air will have the same partial pressures as expired alveolar air
A
false
The partial pressures will be different because gas exchange has happened. There will be less O2 and more CO2 than what was inspired
18
Q
What kind of air does the transitional zone of the respiratory airways contain?
A
a mixx of anatomical dead space and alveolar air
19
Q
What happens if we increase our amount of alveolar ventilation?
A
- Our PAO2 will increase and then plateau at 150mmHg
- We will have a lower PACO2
20
Q
When breathing room air, what is the highest partial pressure our PAO2 can get to?
A
150mmHg
21
Q
What happens if we redue our alveolar ventialtion?
A
- Our PAO2 will decrease because we are bringing in less fresh air.
- If we only have 1L of alveolar minute ventilation instead of 4.2L, our PAO2 will be 0mmHg
- We will have an increase in PACO2
22
Q
In the lungs, what is the pulmonary capillary hydrostatic pressure?
A
7mmHg
23
Q
In the lungs, what is the pulmonary capillary oncotic pressure?
A
28mmHg
(This number is the same as systemic capillary oncotic pressure)
24
Q
In the lungs, what is the interstitial hydrostatic pressure?
A
-8mmHg
25
In the lungs, what is the interstitial oncotic pressure
14mmHg
26
In the lungs, what is the NFP?
* +1mmHg
* net filtration pressure = 7 + 8 + 14 - 28 = +1mmHg
27
What 2 things combined further decrease our interstitial hydrostatic pressure?
* The lungs being surrounded by a pleural pressure of -5cmH2O
* high lymphatic activity in the lungs
28
What is the 1 force that holds pulmonary fluid in the capillary?
The pulmonary capillary oncotic (plasma protein) pressure of 28mmHg
29
What are the 3 forces that favor filtration and movement of fluid out of the capillary and into the interstitium?
* The pulmonary capillary hydrostatic pressure of 7mmHg
* The interstitial hydrostatic pressure of -8mmHg
* The interstitial oncotic (plasma protein pressure) of 14mmHg
30
* Is our lung NFP less or more than what we get with systemic filtration?
* Why is this ok?
* More
* It is ok because our lung lymphatics are very active
31
What does an NFP higher than 1mmHg mean?
the lungs are wet
EX: pulmomary edema
32
What does an NFP less than 1mmHg mean?
The lungs are dry
33
What happens to the lymphatics in the lungs when we use positive pressure ventilation, especially at high pressures/high PEEP?
* The lympathics won't work as well at clearing out all the extra fluid because they won't be able to handle the added pressure from PPV.
34
What is a major obstacle to gas exchange in the lungs?
Fluid because oxygen is not very soluble in water
35
What is the built in safety factor we have to help keep our lungs dry for adequate oxygen exchange?
Our left atrium, which normally has a pressure of 2mmHg, can accomodate a pressure of up to 23mmHg to help take the pressure off the lungs so the lympathics can do their job
36
What happens to the lungs if we have left sided heart failure/ a left atrial pressure greater than 23mmHg?
* Pressure gets backed up in the lungs
* Fluid starts building up in the lungs
* We get pulmonary edema
37
What is the biggest risk for starling forces in the lungs to be out of balance?
* someone who has lost a lot of blood, and you haven't replaced any of their colloids
* Normal capillary oncotic pressure is 28mmHg. If you lose a lot of blood and cut that number in half, you greatly incresae your NFP, which leads to more fluid in the lungs
38
What is the second biggest risk for starling forces in the lungs to be out of balance?
* Left sided heart failure
* If your heart can't pump out what is being returned to it, all that fluid will eventually back up in the lungs.
39
What factors can cause pulmonary edema? (9)
* **Increased capillary permeability **(ARDS, oxygen toxicity, inhaled toxins/pollutants)
* **Increased NFP >1mmHg**
* **Increased capillary hydrostatic pressure >7mmHg **(Left heart failure, mitral stenosis, increased left atrial pressure, volume overload with IV fluids)
* **Decreased interstitial hydrostatic pressure <-8mmHg **(evacuating a pneumo or hemothorax too rapidly, stripping the chest tube, choking and trying to breath against a closed airway)
* **Decreased capillary colloid osmotic pressure >28mmHg **(Over administration of IV fluids that don't have colloids, protein starvation, renal problems resulting in protein urea)
* **Insufficient pulmonary lymphatic drainage** (tumors, interstitial fibrosing diseases, PPV)
*** High altitude pulmonary edema
* drug overdose
* neurogenic pulmonary edema from a head injury**
40
What happens in the lungs if you start choking and try to breathe against a closed airway?
* Flash pulmonary edema
* This is generated by trying to suck in air against a blocked off airway and creating a pleural pressure as low as -50 to -60mmHg
* This happens very quickly and is difficult to reverse
41
For perfusion:
The upper portion of the lung has ___ intravascular pressure, ___ recruitment and distension, ___ blood flow, ___ PVR, ___ perfusion. The vessels are ___, and the alveolai are ___
* lower intravascular pressure
* less recruitment and distension
* less blood flow
* higher PVR
* pulsitile perfusion
* vessels are narrow
* alveoli full and large
42
For perfusion:
The lower portion of the lung has ___ intravascular pressure, ___ recruitment and distension, ___ blood flow, ___ PVR, ___ perfusion. The vessels are ___, and the alveolai are ___
* higher intravascular pressure
* more recruitment and distension
* greater blood flow
* lower PVR
* continuous perfusion
* vessels distended and wide
* alveoli small and not very full
43
For ventilation:
The upper portion of the lung has a ___ pleural pressure gradient, a ___ transpulmonary pressure gradient. The alveoli are ___ and this area gets ___ ventialtion.
* more negative pleural pressure
* higher transpulmonary pressure gradient
* Alveoli are larger and less compliant
* This area gets less ventilation
44
For ventilation:
The lower portion of the lung has a ___ pleural pressure, a ___ transpulmonary pressure gradient. The alveoli are ___ and this area gets ___ ventialtion.
* less negative pleural pressure (or more positive)
* lower transpulmonary pressure gradient
* Alveoli are smaller and more compliant
* This area gets more ventilation
45
What areas of the lung are typically the most ventilated?
The areas that have the most blood flow.
If we don't direct our ventilation to areas with good blood flow, then it is wasted ventilation
46
For V/Q matching:
* What does V stand for?
* What does Q stand for?
* What does V/Q matching mean?
* V = ventilation from the fresh air coming into the lungs
* Q = perfusion from the blood flowing through lung tissue
* V/Q matching = a lot of fresh air ventilating places of the lung that have a lot of blood flow.
47
* What is alveolar compliance?
* What section of the lung are the alveoli more compliant at FRC?
* What section of the lung are alveoli less compliant at FRC?
* Alveolar compliance = How easy it is to fill the alveoli up with air.
* The alveoli at the base of the lung or more compliant (because they are small and don't have much volume)
* The alveoli at the apex of the lung are less compliant (because they are already full and distended)
48
When an upright patient is at RV:
* What section of the lung are alveoli more compliant?
* What section of the lung are alveoli less compliant.
* Alveoli at the apex are more compliant (because they are only 30% full)
* Alveoli at the base are less compliant (Because they are 20% full and the small airways are collapsed)
49
What does a higher transpulmonary pressure and a more negative pleural pressure do to alveoli?
* keeps them distended and open.
* This is what happens at the apex of the lung.
50
If we are in the upright position at FRC where will the inspired air go first?
The base of the lung because the alveoli are less full there and there is more perfusion.
51
If we are in the upright position at RV, where will the inspired air go first?
The apex of the lung because at RV the small airways in the base of the lung have collapsed.
Once the apex gets full of air, it will start opening the airways on through the bottom of the lung.
52
At FRC:
* What is the pleural pressure at the apex?
* What is the transpulmonary pressure at the apex?
* What is the volume of the alveoli at the apex?
* Pip = -8.5cmH2O
* Ptp = +8.5cmH2O
* Alveoli volume = 60%
53
At FRC:
* What is the pleural pressure at the base?
* What is the transpulmonary pressure at the base?
* What is the volume of the alveoli at the base?
* Pip = -1.5cmH2O
* Ptp = +1.5cmH2O
* Alveoli volume = 25%
54
In order to forcefully push more air out of our lungs to get done to RV, we have to make our pleural pressure more negative or more positive?
More positive than -5cmH2O
55
At RV:
* What is the pleural pressure at the apex?
* What is the transpulmonary pressure at the apex?
* What is the volume of the alveoli at the apex?
* Pip = -2.2cmH2O
* Ptp = +2.2cmH2O
* Alveoli volume = 30%
56
At RV:
* What is the pleural pressure at the base?
* What is the transpulmonary pressure at the base?
* What is the volume of the alveoli at the base?
* Pip = +4.8cmH2O
* Ptp = -4.8cmH2O
* Alveoli volume = 20%
57
* What is the lower limit of fullness we can get in the alveoli before they collapse?
* What does this mean?
* Alveoli can only get down to 20% fullness before the small airways start collapsing.
* This means that even as these airways collapse and fresh air is directed elsewhere, there is still a small portion of air trapped in those alveoli.
58
True or false:
The less full the alveoli are, the easier it is to put air into them
true
59
Is the lung more compliant on inspiration or expiration?
expiration
60
What is the difference between the behavior of the lung tissue on inspiration and expiration called?
Hysteresis
61
What happens to your blood gases when you inspire from RV?
* They get very messed up because we are initially sending ventilation to the top of the lungs where there is much less perfusion for gas exchange.
* This would be a V/Q mismatch and is the reason we spend most of our time at FRC and not RV.
62
* How does putting someone under anesthesia compare to the lung volumes at RV.
* How can this be counteracted?
* When we lay someone supine it decreases their FRC.
* Volitiles, anesthetics, and paralytics will decrease our lung volumes.
* Relaxing the chest wall and abdominal wall muscles with paralytics will reduce the lung volume down even further.
* We an counter act this by using more pressure with the ventilator to add more volume.
63
What are the 2 sets of smooth muscles that are most important in our lungs?
* pulmonary blood vessel smooth muscle
* The smooth muscles in the airway
64
What is the purpose of the pulmonary blood vessel smooth muscle?
* It has the ability to constrict and relax blood vessels just upstream op the pulmonary capillaries.
* Squeezing or relaxing determines how much blood flow gets to the pulmonary capillaries.
* These muscles can also direct perfusion towards places where it is needed in the lungs by dilating, or direct perfusion away from areas of the lungs that aren't being ventilated by constricting.
65
What is the purpose of the airway smooth muscle?
* It constricts or relaxes the airways to determine ventilation.
* It can either direct ventilation towards areas of the lung that need to be ventilated, or away from areas of the lung that aren't being perfused.
* If we have a blocked vessel and no perfusion to an area of the lung due to a clot, the airway smooth muscle will contract and direct ventilation to better perfused areas of the lungs.
66
What will a lower alveolar PAO2 cause in terms of perfusion?
It will cause vasoconstriction upstream of that alveoli to direct the blood elsewhere since that portion of the lung isn't being ventilated well.
67
What is HPV?
* Hypoxic pulmonary vasoconstriction
* If we have poorly ventilated areas of the lung, we constrict our blood vessels up stream of those alveoli to direct the blood flow to better ventilated parts of the lung.
68
How is HPV different than systemic circulation?
* HPV vasoconstricts as a result of low PAO2 to an area of the lung so that fresh air is directed towards better perfused areas.
* In the systemic circulation when we have a low PO2 in a tissue, those vascular beds dilate to allow more blood flow to the area.
69
What is the secondary effect that will cause upstream vasoconstriction to a poorly ventilated area?
a buildup of PACO2.
70
What happens to perfusion when we have a collapsed lung?
* All of the blood vessels in that collapsed lung or area will vasoconstrict, clamp down, and redirect the blood elsewhere.
* when this happens are blood gases will still be relatively normal because all of our blood is going to well perfused areas.
71
All vascular smooth muscle vasoconstriction is mediated by what?
cell membrane potentials
72
* What channels on the vascular smooth muscle cell membrane do volatile anesthetics open up?
* What does this cause?
* What protective lung mechanism doesthis interfere with?
* potassium channels
* This causes potassium to leak out of the channel and this vascular smooth muscle relaxes.
* This interferes with HPV because it is relaxing the system that normally vasoconstricts upstream when we have poor ventilation to an area of the lungs.
73
What isthe reason why we have to use supplimental oxygen when a patient is under anesthesia?
General anesthetics will relax the vascular smooth muscle and eliminate the compensatory mechanism of HPV to shunt blood away from underventilated areas of the lung.
74
If we have a perfusion problem from a vlot blocking blood flow, what will our alveolar gas look like?
It will be similar to inspired gas with a PAO2 of 150mmHg and a PACO2 of 0mmHg
75
If we have a ventilation problem due to a blocked airway what will our alveolar gas look like?
It will be similar to pulmonary artery gas with a PAO2 of 40mmHg and a PACO2 of 45mmHg.
76
What is another cause for airway smooth muscle constriction besides preventing air from going to a poorly perfused area?
* Hyperoxia
* If the PAO2 gets as high as 150mmHg, the airway smooth muscle will sense this and constrict to direct the flow elsewhere.
* This is a safegaurd against alveolar dead space because hyperoxia can damage the capillaries by turning them into swiss cheese, as well as create airway reactivity.
77
What are 4 things that will decrease FRC?
* Pregnancy
* Obesity
* pulmonary fibrosis
* Going from up right to supine
78
* How much air is lost at FRC when a patient goes from upright to supine?
* Why?
1L
The FRC goes from 3L to 2L
* This happens becauseall of the stuff from our abdominal cavity pushes up from the underside of the diaphragm, whoch then forces air out.
79
If going from supine to upright what changes happen to your lung volumes and capacities?
* TLC = no change
* VC = no change
* IC = Decrease
* FRC = Increase
* IRV = Decrease
* VT = no change
* ERV = Increase
* RV = no change
80
If going from upright to supine what changes happen to your lung volumes and capacities?
* TLC = no change
* VC = no change
* IC = Increase
* FRC = Decrease
* IRV = Increase
* VT = no change
* ERV = Decrease
* RV = no change
81
What lung volumes and capacities can basic spirometry measure?
* IRV
* VC
* IC
* VT
* ERV
82
What volumes and capacities can NOT be measured with basic spirometry?
* RV
* TLC
* FRC
83
Describe what a basic spirometer looks like
* It looks like an upside down water heater sitting in a pool of water.
* As the patient inspires or expires, the upside down water heater container will either bob up or down depending on what is happening with the volume of air inside the spirometer.
84
What does a basic spirometer do?
It is a basic instrument that measures how the lung volume is changing as someone is breathing (whether it is normal breathing or deep breathing)
85
What happens as we expire air into the spirometer?
* As we expire, it will push the upside down water heater up, which will cause the little marker with the black dot to trace a reading
86
What happens as we inspire air from the spirometer?
* as we inspire, the upside down water heater will go down into the cylinder.
87
What is another name for vital capacity?
The "working volume" we can take into the lungs and put out of the lungs on a single maximal effort breath.
