Pulmonary

Question 1

What are the respiratory and non-respiratory functions of the lung?

Answer 1

Respiratory functions: Gas exchange

Non-respiratory functions:

1. Metabolism (ex: angiotensin II)
2. Air conditioning where the moist mucosa and the increased blood flow warm up the air in the upper airways
3. Blood reservoir
4. Mechanical defense (starts in the upper airways and it prevents the gunk of particles from being stuck and collecting in your lungs)

Question 2

What are the structural features of the trachea? bronchiole?

Answer 2

Trachea has C-shaped cartilagenous rings that cover the anterior portion. Thus, the posterior side is very flexible.

Also, has mucous secreting cells and epithelium that have cilia. Together, this creates the mucocilary layer which helps to slide air/dust particles back up the airway and out of the body

Bronchioles simply have cartilagenous plates that surround them but these don’t really provide as much support, though they allow for increased flexibility. Bronchioles also have a small basement membrane and globet cells that secrete mucous into the lumen of the airway

Question 3

What are the two zones of the lung? What’s the difference b/w the two?

Answer 3

You have the conducting zone and the respiratory zone. The conducting zone is in the upper airways until you reach the terminal bronchioles and this is known as ANATOMICAL DEADSPACE since you have no gas exchange happening here

The lower airways (respiratory bronchioles to alveoli) is known as the respiratory zone and this where you have gas exchange occurring! Also the formation of the alveolar ducts into the alveoli significantly increases the surface area of the respiratory zone

Question 4

What happens to the cartilagenous rings surrounding the trachea?

Answer 4

As the airways continue to branch further and further and develop their own support, the cartilagenous rings change into plates that surround the bronchioles

Question 5

What is unique about the respiratory zone?

Answer 5

Has high SA due to the alveoli

Question 6

What happens to an asthmatic patient’s bronchioles?

Answer 6

The bronchiole’s have too much overproduction of mucous that can lead to formation of mucous plugs. They also have more mucous secreting goblet cells and they have a thicker basement membrane

Question 7

What are alveolar pores?

Answer 7

These are small opening b/w individual alveoli that allow for inter alveolar communication and let the lung expand as one giant unit and not as an individualized segment

Question 8

What happens in emphysema to your alveoli?

Answer 8

The alveoli lose their normal shape and they start to become less honeycomb like and shrivel up

The alveolar walls also thin and wear away…REDUCES SURFACE AREA & thus decreases gas exchagne

Question 9

What is the dual circulation of the lung?

Answer 9

You have pulmonary circulation that is where gas exchange happens and goes back to the left atria

You have bronchial circulation that supplies the bronchioles w/ the blood supply that they need. This allows for them to be fresh and healthy

Question 10

What two cells make up the alveolar septum? Function?

Answer 10

The alveolar septum is the wall b/w two alveoli. This is made up of Type I and Type II pneumocytes

Type 1: Majority (95%) and makes up the wall
Type II: Less common but can differentiate into Type I and can also produce surfactant

Question 11

Why don’t our lungs collapse?

Answer 11

1. We have interalveolar dependence due to the honeycomb shape that the alveoli are in. This allows for neighboring alveoli to pull at other alveoli and keep them held up
2. You have surfactant production that reduces the surface tension in the alveoli that you get that you get form the air:liquid interaction

Question 12

What is adult respiratory distress syndrome?

Answer 12

this is a condition where your surfactant quality is diminished and it’s not as good thus you don’t reduce the surface area to the extent you would need too. Thus, your lungs are more susceptible to collapse at low pressures

Also you have membrane pealing that prevents efficient gas exchange from occurring

Question 13

What is your normal anatomical deadspace?

Answer 13

150 ml

Question 14

What makes up your alveolar gas?

Answer 14

It’s a combination of both residual air always stuck in the lungs and inspired air that has made it through the anatomical dead space

Question 15

What is alveolar ventilation?

Answer 15

Breathing air in and out…specifically the portion that occurs in the respiratory zone where gas exchange happens

Question 16

What is FEV1? How does the FEV1/FVC ratio differ if you have obstructive lung disease? Restrictive lung disease?

Answer 16

FEV1 is the forced expiration volume that happens in one second…normally the ratio is 0.8 because 80 percent of our expiration happens in that one second

However, in obstructive lung disease, this ratio will be lower since it takes longer for you to expire since you don’t have normal lung airflow…decreases the FEV1 and thus decreases the ratio

In restrictive lung disease, you decrease your TLC and this means that you also reduce your FEV1. Therefore, your ratio should be similar though your TLC is reduced

Question 17

What are some examples of obstructive lung disease?

Answer 17

COPD, asthma, & emphysema

Question 18

What are some examples of restrictive lung disease?

Answer 18

Anything that impedes the lung’s ability to expand fully

Pulmonary fibrosis, chest scarring, neuromuscular disorder, Adult respiratory distress syndrome

Question 19

How do lung volumes differ for obstructive and restrictive lung disorders?

Answer 19

Obstructive: At lower lung volumes you are more likely to collapse the lung and trap in more air thus you have HIGHER RESIDUAL VOLUME, and thus HIGHER TLC

Restrictive: You can’t fully inflate your lungs to normal level and thus you have REDUCED TLC

Question 20

What is the helium dilution technique? What can it help us calculate?

Answer 20

You take a container with a known concentration and volume of helium and have a person breath this in. Over time it equilibrates with their lung volume. At this point you take the concentration of the helium in the container as new C2 and then you volume is V1 (container volume) and V2 (volume left in lung) which is FRC

Question 21

How can you maximize your alveolar minute ventilation?

Answer 21

you can maximize this by increasing Tidal volume which can be done by reducing RR

If your tidal volume is unaffected, then you can do it by increasing RR

Also, by decreasing dead space

Question 22

What is the fowler method?

Answer 22

This is when you give a patient straight up 100 percent oxygen and then you capture their expired breath and plot the percentage of nitrogen captured over time. Note that the nitrogen is usually confined to our alveolar residual volume. Eventually, when this value plateaus, this means you have brought out all the nitrogen. You then draw a vertical line on the graph so that the area about and below the graph are in equal value. The area below the graph is your dead space

Question 23

What is physiological dead space? How do you get alveolar dead space?

Answer 23

physiological = anatomical + alveolar

you can get alveolar from reduce CO or pulmonary embolism

Question 24

What happens to you alveolar and arterial CO2 levels as you increase you alveolar ventilation?

Answer 24

If you increase alveolar ventilation, then these levels decrease b/c you’re blowing away the CO2

Question 25

Describe the process of inspiration (mention the effect of intrapleural pressure and transpulmonary and intrapulmonary pressure)

Answer 25

Your brain sends signals to your primary and accessory muscles (if needed) to cause muscle constriction. This leads to expansion of the thoracic wall and increased thoracic volume reduces the intrapleural pressure even more. This causes an increase in the transpulmonary pressure. Also, the alveoli are pulled and expanded, dropping the pulmonary pressure below atmospheric. This leads to air entering your alveoli.

Question 26

Describe the process of expiration(mention the effect of intrapleural pressure and transpulmonary and intrapulmonary pressure)

Answer 26

Passive process where the diaphragm relaxes and this decreases your thoracic volume, increases intrapleural pressure, and decreases the transpulmonary pressure. Causes air to leave your lung b/c the elastic recoil pushes the alveoli and deflates them (increases pulmonary pressure above atmospheric pressure)

Question 27

Why is there no airflow at FRC?

Answer 27

Functional residual capacity is the balance b/w lung and chest wall volumes. At this point they both exert the same amount of pressure so there's no airflow!

Question 28

What is the natural tendency for the lungs and the thoracic wall? Why does this affect the intrapleural pressure?

Answer 28

Lungs want to collapse and the thoracic wall wants to expand...this makes the intrapleural pressure negative during normal breathing

Question 29

What happens in pneumothorax?

Answer 29

Here you have some puncture that causes the intrapleural pressure to equal atmospheric. Therefore, the transpulmonary pressure is equal to 0. This causes the lung on that side to collapse and the chest wall to expand

Question 30

What are the two factors that affect ventilation?

Answer 30

Compliance and airway resistance

Question 31

What are the factors that affect compliance?

Answer 31

1. Elastic content (inverse relationship) 2. Surfactant (direct relationship) 3. Mobility of chest wall (direct relationship)

Question 32

How does compliance change for pulmonary fibrosis vs emphysema?

Answer 32

Pulmonary fibrosis: there's lower compliance (you're replacing elastin w/ more cells to thicken the alveolar septum and collagen fibers to make the alveoli more rigid) emphysema: there's more (you're destroying the elastin fibers)

Question 33

What is hysteresis? What is the primary reason for this?

Answer 33

Hysteresis is the difference b/w the pressure/volume or compliance curves of inspiration and expiration. This is due primarily to surfactant

Question 34

Why doesn't LaPlace's Law (lower radius = higher pressure) cause movement of air in lungs from high pressure or smaller alveoli into lower pressure/larger alveoli?

Answer 34

.1. Surfactant tends to reduce the surface tension more and more as the radius decreases. This reduced tension decreases the pressure. 2. The alveoli also have interalveolar pores that allow for all the alveoli to further stabilize and stay open!

Question 35

What is respiratory distress syndrome of the newborn? Treatment (2 means)?

Answer 35

This is when newborns lack adequate surfactant production and thus they don't have fully open alveoli. Treat by giving them artificial surfactant or via mechanical ventilation

Question 36

What is FRC?

Answer 36

This is the functional reserve capacity and in normal breathing it's the volume of breath that stays in your lungs when the tendencies of

Question 37

What are two reasons for chest wall compliance being decreases?

Answer 37

Increased intra-abdominal pressure (ascites or pregnancy) Reduced normal movement of rib cage (kyphoscoliosis or broken ribs)

Question 38

Why is the base of the lung more ventilated than the apex?

Answer 38

The apex of the lung has more negative intrapleural pressure due to gravity pulling the lung down. This causes the transpulmonary pressure there to be higher and the alveoli are normally more expanded than at the base. Thus during inspiration, they don't expand as much and the ventilation is lower

Question 39

Where is perfusion the greatest in the lung?

Answer 39

Base

Question 40

What causes increases in airway resistance? decreases in airway resistance?

Answer 40

Increase: Bronchoconstriction (histamines, leukotrienes, PNS) and compression of airway Decrease: Bronchodilation (leukotriene antagonists, SNS (beta 2), and anti-histamines) & low density air (heliox)

Question 41

What are the two reasons for why lower lung volumes cause increased airway resistance?

Answer 41

1. Traction (less alveoli pull it open and this strength is lower) 2. Reduces transpulmonary gradient (pressure outside > pressure on the inside at low lung volumes so the air way is more likely to constrict/collapse...reduced radius thus more resistance)

Question 42

Why can forced expiration potentially collapse smaller airways?

Answer 42

This causes your intrapleural pressure to be much more positive and thus in your smaller airways you can potentially exceed the intrapulmonary pressure and cause them to collapse

Question 43

What are the two types of work in breathing? What do they do?

Answer 43

Resistive work: overcomes tissue or airway obstruction | Elastic work: overcomes loss of elastic recoil in restrictive disorders

Question 44

What's the difference b/w extrathoracic obstruction and intrathoracic obstruction? How do you differentiate between the two?

Answer 44

Extrathoracic: The flow-volume loop is flatten in inspiration & narrowed. This is b/c you have an obstruction outside the thoracic outlet and during inspiration the tracheal pressure is less then atmospheric pressure causing an obstruction. ex: vocal cord paralysis & extrathoracic goiter Intrathoracic: Reduced flow-volume loop for expiration and this is b/c you have an obstruction inside thoracic cavity that causes the tracheal pressure to be less than pulmonary pressure (collapses the airway) ex: tracheomalcia (problems w/ collagen integrity of the airway causing it to be narrowed and easily collapsable)

Question 45

How is oxygen primarily transported in our blood? carbon dioxide?

Answer 45

Oxygen is carried mainly through hemoglobin | Carbon dioxide is carried mainly by bicarbonate ions

Question 46

Compare the solubilities of oxygen and carbon dioxide. How does this affect their diffusion constant?

Answer 46

Oxygen has a much lower solubility than carbon dioxide. This means that oxygen has a lower diffusion constant than carbon dioxide and is not as readily dissolved in the blood

Question 47

What factors affect a gas's ability to flow through the alveolar:capillary interface?

Answer 47

1. Surface area for diffusion...as this increases, there's higher flow 2. Thickness of membrane...thinner the membrane, then larger the diffusional flow 3. Diffusion constant...higher the constant larger the flow. this is positively related by solubility and negatively related to molecular weight

Question 48

Define the diffusion classifications of CO, N20, & O2

Answer 48

CO: Diffusion limited b/c when it gets into the blood it immediately gets picked up by hemoglobin and doesn't fall off quickly. Thus, it doesn't really accumulate in the capillaries. N20: Perfusion limited b/c when it quickly enters the blood and doesn't get picked up by Hb. Thus, within 0.1 seconds it fully saturates the blood and you need the blood to flow and have new blood coming in so that it can pick up more N20 02: normally is perfusion limited but in diseased individuals can become diffusion limited

Question 49

What are the two components of total diffusion capacity of the lung? What factors affect either component?

Answer 49

Total diffusion capacity = diffusion through the alveolar/capillary membrane + rate of reaction for oxygen combining w/ hemoglobin Diffusion through membrane can be made worse if the membrane is thickened Rate of reaction of oxygen w/ hb is based on the alveolar pressure and amount of blood in the lung

Question 50

In what cases can oxygen diffusion become diffusion limited as opposed to being perfusion limited?

Answer 50

1. Thickened alveolar septum so longer time to diffuse through 2. Severe forms of exercise, especially if you have a lung defect 3. Reduced ambient air oxygen pressure (i.e. higher elevations)

Question 51

What are three key functions of the pulmonary circulation?

Answer 51

1. Transfer blood to the alveolar:capillary interface and help facilitate gas exchange 2. Provide blood to systemic circulation if needed 3. Metabolism of metabolites such as Bradykinin & Angiotensin

Question 52

Describe the pulmonary circulation organization in the lungs

Answer 52

pulmonary arteries branch into smaller arteries that follow alongside of larger airways and these continue to branch outward until the end of the terminal bronchioles. The the arteries form a large meshlike capillary sheet that drapes over the alveoli like sheets

Question 53

Where does the bronchial circulation drain blood to?

Answer 53

It either drains blood into the bronchial veins or the pulmonary veins and brings them back into the right atria or left atria, respectively

Question 54

Describe the pressure, resistance, and cardiac output from the left and right side

Answer 54

Left and right side have the same cardiac output but left has greater pressure and resistance. Thus the left side of the heart is more muscular

Question 55

What are two differences b/w the pulmonary and systemic vasculatures (vessel & capillaries)?

Answer 55

1. pulmonary vessels are thinner walled, have more compliance, and dilated. Systemic vessels have more smooth muscles, thicker walls, and more actively controlled 2. Capillaries of the pulmonary form a dense sheet of blood but capillaries of the systemic form networks w/ some connections to distribute blood as needed

Question 56

What is PAOP? How is it measured? What can it be a good estimate for?

Answer 56

PAOP = Pulmonary arterial occlusion pressure and it is an estimate of left atria pressure, left end-diastolic ventricular pressure, and preload of the heart This can be measure w/ a pulmonary artery catheter and a balloon at the end that is blown up to create a column of blood in the pulmonary vessels. This can help estimate the pressures

Question 57

What happens to PVR as arterial and venous pressures increase? Why?

Answer 57

As the pressures increase then they cause previously closed capillaries to open up and also recruit more capillaries. This leads to a reduction in the PVR. Reduction is fart more for arterial pressure increase than for venous pressure increase

Question 58

What happens to PVR as blood flow increases? Why?

Answer 58

As blood flow increases, it causes an initial recruitment of capillaries and then an eventual distention of the capillaries, leading to a reduction of the PVR.

Question 59

What are passive mechanisms and active mechanisms of controlling PVR?

Answer 59

Passive: recruitment of capillaries & capillary distension Active: Vasoconstriction (localized) upon hypoxia in an alveolus

Question 60

What happens to PVR as lung volumes increase or decrease?

Answer 60

At TLC, your PVR is the highest it can be b/c your alveoli are fully distended and this compresses the alveolar vessels, causing them to exert more pressure and resistance. As you decrease your lung volume you reduce you lung volume, until you reach FRC (your lowest PVR). if you decrease further below this, then the pressure inside of your bronchial airways is soo low that it is compressed by the increased pressure outside of it. Thus you have again an elevation of PVR

Question 61

What is pulmonary hypertension?

Answer 61

When you have damage or injury to your pulmonary vessels, then you cause remodeling & loss of smooth muscle. This reduces the compliance of the vessels and thus increases the pressure and PVR. This increased resistance can cause increased pressure in the RV and lead to RV hypertrophy. EVENTUALLY, your cardiac output can also decrease since the RV may push up on the LV and thus lead to reduced filling of the LV or reduced preload

Question 62

How do low pH and sympathetic stimulation affect pulmonary vessels during hypoxia?

Answer 62

They both cause vasoconstriction and INCREASE PVR

Question 63

Describe regional vasoconstriction

Answer 63

When you have an alveoli that is occluded it will have lower than normal oxygen partial pressure and larger than normal carbon dioxide partial pressure. In response, your body will vasoconstrict the afferent arteriole entering that capillary bed for the alveoli. This doesn't change pulmonary pressure or PVR since it's localized and allows for more blood flow to the necessary areas of the lung

Question 64

Describe regional vasoconstriction

Answer 64

When you are at high altitude or have reduced ambient oxygen in the air this leads to a vasoconstriction of all your vessels exposed to the lower oxygen PVR increases and Pulmonary pressures increase...can cause pulmonary hypertension

Question 65

Describe the distribution of blood flow through the lungs. What are the three zones?

Answer 65

As you go from the apex to the base, your blood flow or perfusion will increase Zone 1: this is near the apex and alveolar pressure > arterial pressure > venous pressure...thus you have a certain extent of vasoconstriction of the capillary and this reduces the perfusion...if you have trauma or hemorrhaging then you're more likely to have larger regions of wasted capillaries with 0 perfusion Zone 2: this is in the middle of the lung and arterial pressure > alveolar pressure > venous pressure. Still not super ideal since the vessel taking blood away from the lung is compressed Zone 3: This is the base of the lung and arterial pressure > venous pressure > alveolar pressure and this is ideal

Question 66

In zone 2 and zone 3 what determines the blood flow?

Answer 66

The Alveolar - arterial pressure gradient...remember FLOW = Change in pressure/Resistance. This is independent of the venous pressure gradient

Question 67

What is fluid flux? How do you increase it?

Answer 67

This is the force in capillaries that causes fluid to be filtered out into the interstitial space. 1. Left heart failure...causes a back up of blood that goes into the pulmonary vessels and increases hydrostatic pressure 2. Reduce protein content in capillaries and decrease oncotic pressure 3. Sepsis that can damage the walls and make them more leaky 4. ARDS where you have low surfactant and thus you have increased surface tension to the alveolar wall and you pull in more water and cause capillaries to leak into the alveolus

Question 68

What is henry's law?

Answer 68

This states that the amount of gas in the blood is proportional to its solubility and its partial pressure

Question 69

What is methemoglobin?

Answer 69

This is when you turn a ferrous iron (+2) into ferric iron (+3). This conversion causes hemoglobin to bind oxygen and not let go...causes you to be functionally anemic

Question 70

What is the structure of hemoglobin? fetal hemoglobin?

Answer 70

hemoglobin normally is 4 subunits (2 alpha and 2 beta) | Fetal hemoglobin is 4 subunits (2 alpha and 2 gamma)

Question 71

Differentiate b/w oxygen content, oxygen capacity, oxygen saturation, and partial pressure of oxygen

Answer 71

oxygen content = the total amount of oxygen dissolved in blood and found in hb oxygen capacity = The total amount of oxygen that can bind to your hb oxygen saturation = percentage of hemoglobin bound by oxygen partial pressure of oxygen = the amount of oxygen dissolved in the blood

Question 72

What are the two sections of the oxygen dissociation curve? In which vessel is each section especially important?

Answer 72

1. Plateau region: You're oxygen saturation doesn't drop significantly even w/ drops in your oxygen partial pressure. This is useful in the capillary beds when you are trying to load oxygen. 2. Steep region: This is what's found normally in your veins b/c here small deviations in the partial pressure of oxygen cause huge drops in the oxygen saturation. B/c you want to prioritize unloading your oxygen

Question 73

What does right ward shift of the oxygen dissociation curve mean? left-ward shift?

Answer 73

right-ward shift = facilitates unloading of oxygen (typically what your venous blood looks like) left-ward shift = facilitates loading oxygen and holding onto it (typically what your arterial blood looks like)

Question 74

What is P50? What does a higher or lower number indicate?

Answer 74

P50 is the partial pressure of oxygen needed for there to be 50 percent saturation of your hemoglobin Higher number = you're more easily unloading oxygen so you're reaching the 50% at a higher than normal partial pressure Lower number = your no unloading oxygen as readily and holding onto it..this is why you reach the 50% saturation at a lower partial pressure of oxygen

Question 75

How does an increase or decrease in pH shift the 02 dissociation curve? increase or decrease temperature? Increase or decrease in 2,3-DPG?

Answer 75

pH increase causes leftward shift, pH decrease right Increase in temp = right, decrease in temp = left Increase in 2,3-DPG = right, decrease in temp = left

Question 76

What is the bohr effect?

Answer 76

When you're partial pressure of CO2 increases, you have a right ward shift When it decreases you have a leftward shift

Question 77

What is carboxyhemoglobin? How does this affect the oxygen dissociation curve?

Answer 77

This is when hemoglobin binds CO, which has a very strong affinity to it. This prevents hemoglobin from not only letting go of it's currently bound O2 but also from binding any future O2. Causes a leftward shift in the curve since you hold onto O2. Can cause functional anemia by reducing both the oxygen content and capacity (decreases working hb)

Question 78

What are four ways of coping w/ the high altitude and decrease in inspired partial O2?

Answer 78

1. Hyperventilate to blow off CO2...as you decrease partial pressure of CO2, then you will increase your alveolar oxygen partial pressure...alveolar gas equation 2. Polycythemia or make more RBC ---> thus while your oxygen saturation decreases, your oxygen content and capacity both increase 3. Respiratory alkalosis --> helps you load your RBC w/ more oxygen at the capillaries and alveoli 4. Increase 2,3-DPG production --> helps unload the oxygen at the tissues more easily

Question 79

What is the Haldane effect?

Answer 79

As your oxygen partial pressure increases, hemoglobin's affinity to carbon dioxide decreases...this means that you will be able to more easily take on the oxygen

Question 80

How does the distance b/w capillaries and tissues change with increased demand for oxygen?

Answer 80

As the demand for oxygen increases, then the tissues and capillaries decreases the space b/w them as the tissues recruit and open more capillaries...this helps to increases the tissue partial pressure of oxygen

Question 81

What is hypoxic hypoxia? Anemic hypoxia? Circulatory hypoxia? Histotoxic hypoxia?

Answer 81

hypoxic hypoxia = low oxygen content or saturation Anemic hypoxia = low hemoglobin Circulatory hypoxia = low cardiac output Histotoxic hypoxia = inability of the cell to consume the oxygen even when it is delivered correctly

Question 82

What's partial pressure of oxygen and carbon dioxide in inspired air? alveolar gas? mixed venous blood? end-pulmonary artery?

Answer 82

inspired air: O2 is 150 CO2 = 0 Alveolar gas: O2 = 100 and CO2 = 40 Mixed venous blood: O2 = 40 and CO2 = 45 End-pulmonary artery blood: O2 = 100 and CO2 =40 (NOTE THERE MAY BE SOME DEVIATION B/W THE ALVEOLAR AND ARTERIAL O2 partial pressures)

Question 83

Why does inspired air have more partial pressure of oxygen than alveolar gas

Answer 83

It is dependent upon the consumption of O2 and the replacement by inspired air. In our body, our capillaries consume more than we can replace via inspired air and therefore you have reduce alveolar o2 when compared to the o2 in inspired air

Question 84

What are 4 causes for hypoxemia?

Answer 84

1. Diffusion limitations that reduce the ability for gas exchange to occur efficiently 2. Abnormal shunts 3. Hypoventilation 4. Severely mismatched Ventilation/Perfusion ratios

Question 85

Why does our arterial PO2 differ from our alveolar PO2?

Answer 85

1. Diffusion of oxygen through the alveolar membrane into the capillary is not complete and thus you don't get the arterial P02 = alveolar P02 2. We normally have some shunts in our body which then combine w/ normally oxygenated blood and thus cause a lower arterial P02 3. V/Q differences throughout the lung cause perfusion & P02 fluctuations b/w the base and the apex leading to less oxygen in the arteries than in the alveoli

Question 86

What happens in diffusion limitation? What are three ways in which you can get diffusion limitation based hypoxia?

Answer 86

Diffusion limitation is when diffusion is no longer an efficient process and it takes longer for the blood to be fully oxygenated 1. Thickening of the alveolar:capillary membrane (pulmonary edema or pulmonary fibrosis) 2. Severe exercise/exertion 3. Increasing elevation (decreasing partial pressure of O2 in ambient air)

Question 87

What is a shunt? What are two normal shunt systems in our body?

Answer 87

Shunt = when you have deoxygenated blood that enters the systemic circulation w/o passing through a ventilated lung...thus this doesn't participate in gas exchange 1. Bronchial veins --> Left atria instead of right atria 2. Coronary veins ---> Thesbian veins ---> Left ventricle

Question 88

What are three types of intracardiac shunting?

Answer 88

1. Atrial/ventricular septal defects 2. Pulmonary atriovenous fistuals 3. Tetrology of fallot (pulmonary stenosis, overriding aorta, and ventricular septal defect)

Question 89

Will giving supplemental oxygen to someone w/ shunt help?

Answer 89

No it won't fully help them. Normally, you expect their Pa02 to get to 600, but with this you still have the deoxygenated blood circulating so you only get to 100-105

Question 90

How does hypoventilation cause hypoxemia? How can you assess if someone has hypoxemia due to this?

Answer 90

Hypoventilation --> Decreases minute ventilation---> increases PaCO2 ---> via the alveolar gas equation causes a drop in PA02 If you give a person 100% oxygen and you note that they are still doing super poorly and their symptoms aren't getting better, then they are hypoventilating...also, will have really high PaCO2 levels.

Question 91

What can cause hypoventilation?

Answer 91

Damage/injury to respiratory centers Respiratory muscle weakness/fatigue or nerve injury/spinal cord injury Obesity that can change lung or chest wall mechanics

Question 92

What is the V/Q ratio? Why is it important? What does it mean if V/Q 1, & approaching infinity?

Answer 92

It's the ratio of ventilation to perfusion we have in our lungs. 1 means you have a partially occluded vessel that is reducing the perfusion approaching infinity means you have dead space due to completely blocked vessel

Question 93

How does V/Q differ across the lung? What's the implication of this for the partial pressures of oxygen and carbon dioxide?

Answer 93

As you get to the base of the lung, ventilation increases but not as much as perfusion. This causes the V/Q ratio to be larger at the base of the lung than at the apex. This means that at the base of the lung you will have less PO2 and more PCO2 than at the apex.

Question 94

How do variations in blood flow in the lung lead to the A-a gradient?

Answer 94

The base gets more of the blood flow so the overall arterial oxygen pressure is based heavily on it's low PO2 concentrations (this is due to lower V/Q ratio in the base)

Question 95

How do O2 concentration differences in the lung lead to the A-a gradient?

Answer 95

The apex has higher P02 concentrations than normal while the base has lower P02 concentrations...however, it's not that much higher, while in the base it's a lot lower. Thus, the apex and higher V/Q regions can't compensate for the lower V/Q regions...this causes the A-a differences