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Unit 1 > 9-25a Pulmonary Physiology II > Flashcards

9-25a Pulmonary Physiology II Flashcards

1
Q

What is partial pressure?

A

fraction of pressure due to O2 (in PO2) is the partial pressure it would exert if it occupied the entire volume of the mixture; proportional to the concentration of O2 in the gas

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2
Q

What are the pressure gradients in the lungs?

A

PaO2 (arterial blood), PAO2 (alveolus blood), and PVO2 (venous blood)

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3
Q

What determines the flow rate of the diffusion of gases?

A

proportional to:
permeability of the conductance

size of partial pressure gradient

SA available for exchange

inverse to:
membrane thickness

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4
Q

What do partial pressures drive?

A

diffusion of gases

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5
Q

What is the PO2 in the conducting zone? Why?

A

150 mmHg

partial pressure in humidified air, so the partial pressure of water vapor needs to be subtracted

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6
Q

What is the PO2 in the conducting zone? Why?

A

150 mmHg

partial pressure in humidified air, so the partial pressure of water vapor needs to be subtracted

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7
Q

Why is PA 100 mmHg when it was 150 mmHg in the conducting zone?

A

gas exchange between the alveolus and the blood

PACO2 is 40 mmHg and 100 mmHg in Alveolus from CO2 coming into alveolus and O2 leaving

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8
Q

Why does PAO2 = PaO2 and PACO2 = PaCO2

A

both are 100 mmHg b/c arterial blood equilibrates with the alveolar air

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9
Q

Why does PAO2 = PaO2 and PACO2 = PaCO2

A

both are 100 mmHg b/c arterial blood equilibrates with the alveolar air

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10
Q

Why do we have lots of room to increase the speed of the blood through the capillary?

A

within a third of the length of the capillary blood equilibrates

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11
Q

What occurs in fibrosis?

A

thickening b/w blood-gas barrier and slows O2 exchange, so PAO2>PaO2

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12
Q

How much O2 is there per 100 mL of blood?

A

0.3 mLO2

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13
Q

If CO is 5L/min, how much O2 is delivered to the tissues per minute?

A

CO * 3mL/L blood = DO2a

5 L/min * 3 mL/L = 15 mL O2/min

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14
Q

If resting metabolic rate = 250 mL O2/min, how long before we became anoxic? Why does this not occur?

A

It would take 4 seconds
1 min (60s)/ 15 mL O2/min = 4 s
This is a really small part of all the O2 in the blood

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15
Q

How is O2 transported in the blood? When we measure SaO2%, what is considered?

A

bound to HGB (98%) via iron
SaO2 measures percent of HGB-O2 binding sites that are bound to HGB
(changes light fracture)

and dissolved in plasma (2%)

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16
Q

How do we calculate the Content of O2 in blood? How much O2 is in the blood?

A

Add the O2 bound to HGB and what is dissolved in plasma

20.3 mL O2/100 mL blood

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17
Q

What is the P50?

A

The PO2 at which 50% of the HGB binding sites are bound to HGB

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18
Q

When PaO2 is 25 mmHg, how many of the HGB binding sites are bound to O2?

A

50%

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19
Q

What happens when P50/affinity is right-shifted? What does this mean about HGB’s affinity to O2?

A

PaO2 gets higher (37mmHg), so 50% of the HGB binding sites are filled at 37mmHg PaO2

affinity is less bc we need more O2 to fill binding sites

therefore is more willing to unload

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20
Q

When muscles are most active, what happens to pH, PCO2 levels, and heat? What do they need more of?

A

lower pH, higher PCO2, and higher heat

need more O2

decrease of HGB affinity (right-shift) helps the O2 get to the tissues

21
Q

When muscles are most active, what happens to pH, PCO2 levels, and heat? What do they need more of?

A

lower pH, higher PCO2 (effect of both on affinity causes Bohr effect), and higher heat

need more O2

decrease of HGB affinity (right-shift) helps the O2 get to the tissues (unloading)

22
Q

What are the three modes of CO2 transport?

A

dissolved in the plasma (5%)
bound to HGB (different site 3%)
Chemically Modified Form (92%) protons and bicarbonate

23
Q

How does the CO2 get from the tissues to the blood?

A

Diffuses down concentration gradient into the blood. Some is diffused into plasma and some is bound to HGB

24
Q

How does CO2 become carbonic acid?

A

Interacts with water catalyzed by carbonic anhydrase via enzyme in RBC and results in a proton and bicarbonate

25
Q

How does CO2 become carbonic acid?

A

Interacts with water catalyzed by carbonic anhydrase via enzyme in RBC and results in a proton and bicarbonate

26
Q

How does the CO2 reaction in the RBC change direction from R to L or L to R?

A

direction and rate are determined by conc. of reactants and products

in tissues = lots of CO2 and goes to right (conv. to bicarbonate and proton)

in lungs = PCO2 is low and goes to the left (lots of bicarbonate ready to be released)

27
Q

What is a chloride shift?

A

When bicarbonate levels rise in the RBC and diffuse out of the cell into the plasma, an electrical gradient causes chloride to enter the cell to balance it

28
Q

What does the proton do?

A

it binds to unbound HGB

29
Q

What is hypoxemia?

A

PaO2 < 80 mmHg

30
Q

What is hypercapnia?

A

PaCO2 > 45 mmHg

31
Q

What senses hypercapnia?

A

central chemoreceptors in the brain stem are sensitive to PCO2 and pH of cerebrospinal fluid

Most important regulators of ventilation

32
Q

What senses hypoxemia?

A

Sensed by peripheral chemoreceptors in carotid and aortic bodies

less sensitive than central chemoreceptors

33
Q

Where are the signals of hypercapnia and hypoxemia sent to?

A

respiratory centers in the medulla and the pons

34
Q

Where do the medulla and the pons send signals to?

A

the respiratory drive centers to increase ventilatory drive/RR

35
Q

How does a significant drop in O2 levels due to hypoxemia compare to a significant drop in O2 levels with anemia? What does this tell us?

A

hypoxemia: (PaO2 lower than 100 mmHg) disturbs the partial pressure gradients that drive diffusion, but O2 content only drops to 19 mL O2/100 mL blood

O2 content for anemia (HGB = 10) is far lower (13.9 mL O2/100mL blood); PaO2 and SaO2 are normal

O2 saturation levels can be high, but O2 content can still be low due to anemia

36
Q

What can cause hypoxemia?

A

Breathing a hypoxic gas

Hypoventilation (PAO2 and PaO2 fall and PaCO2 rise); caused by decreased ventilatory drive (certain drug effects), paralysis/weakness of ventilatory muscles, or damage to chest wall

Diffusion limitation (Can occur with fibrosis)

Ventilation-Perfusion mismatching (Most common and important in lung disease)

37
Q

What are ventilation and perfusion? What is their interaction? Normal value?

A

ventilation (V): ventilation in L/min

Perfusion (Q): CO (L/min)

V/Q
4/5 = 0.8

38
Q

How is perfusion affected by gravity?

A

base of lungs are below the heart, so the amount of blood flow to an area is affected as well

39
Q

What are the normal values for V/Q, PAO2, PACO2, PaO2, and PaCO2?

A 
V/Q = 0.8
PAO2 = 100 mmHg
PACO2 = 40 mmHg
PaO2 = 100 mmHg
PaCO2 = 40 mmHg
40
Q 
What are values for V/Q
PAO2
PACO2
PaO2
PaCO2 
when blood is shunted through the lung w/out gas exchange?
A 
V/Q = 0
PAO2 = n/a
PACO2 = n/a
PaO2 = 40 
PaCO2 = 46 (no gas exchange, just like venous blood)
41
Q 
What are values for V/Q
PAO2
PACO2
PaO2
PaCO2 
air flow is retained but blood flow is shut off? ex?
A 
PE
V/Q = infinity
PAO2 = 150 
PACO2 = 0 
PaO2 = n/a
PaCO2 = n/a
42
Q

What is the distribution of perfusion in the apex vs. base? What affects it?

A

Capillaries in apex are
UNDERPERFUSED, while
those in base are
OVERPERFUSED

Flow at bases > Flow at
apex due to gravity

pressure in Pa, PV, and PA

43
Q

At the apex of the lung, what is V/Q, what is PaO2 and PaCO2?

A

V is lower and Q is lowest (underperfused = overventilated):
V/Q is highest
PaO2 is 130
PaCO2 is 28

Looks more like alveolus

44
Q

At the middle of the lung, what is V/Q, what is PaO2 and PaCO2?

A

V and Q are normal, so:
V/Q is 0.8
PaO2 is 100
PaCO2 is 40

45
Q

At the base of the lung, what is V/Q, what is PaO2 and PaCO2?

A

V is lower and Q is highest, so:
V/Q is 0.6
PaO2 is 89
PaCO2 is 42

46
Q

When V/Q is low:

A

ventilation < perfusion

air coming out of the lung looks more like venous blood

47
Q

When V/Q is high

A

ventilation > perfusion

air coming out of the lung looks more like the alveolus

48
Q

What are the phases of ventilation and moderate exercise? What happens during steady state exercise? What confirms this?

A

Phase I: immediate increase in ventilation at the start of exercise

Phase II: Primary

Phase III: Steady State:
the level of ventilation is well matched to the increase in O2 consumption and CO2 production (matches to metabolic demand); linearly related

venous blood has high levels of PVCO2 that give off enough so that PaCO2 remains the same

Unit 1 (25 decks)

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