Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Block 2 Exam 3 > Cremo 2: Factors that control CO2 and O2 in alveoli and blood > Flashcards

Cremo 2: Factors that control CO2 and O2 in alveoli and blood Flashcards

1
Q

Sensors of blood CO2 levels

A
  1. Central chemoreceptors in medulla

2. Peripheral chemoreceptors in carotid and aortic bodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Arterial CO2 is controlled by two rates. What are they?

A
  1. Metabolic production of CO2 (VCO2)

2. Alveolar ventilation (VA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

PCO2 ventilation equation

A

PaCO2 = VCO2 * 0.863 / VA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

H-H equation (acid-base)

A

pH = 6.1 + log [HCO3-]/0.03(PaCO2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Alveolar gas equation (oxygenation)

A

PAO2 = PIO2 - 1.2(PaCO2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a buildup of CO2 in the blood due to?

A

A failure in some component of the respiratory system (not an increase in metabolic CO2 production)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is VCO2?

A

Rate of CO2 production by metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What two rates control PaCO2?

A

VA: rate of alveolar ventilation by lung
VCO2: rate of CO2 production by metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Alveolar ventilation and CO2 production double during moderate exercise in a 24-year old man. What is the effect on PaCO2?

A

No effect! Both variables change together!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Clinical definition of hypercapnia or hypoventilation.

A

PaCO2 of >45mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Clinical definition of hypocapnia or hyperventilation.

A

PaCO2 of <35mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Normal PaCO2 levels

A

35-45mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

A 32 year old male has just run into the classroom after being late for class. He can be considered to be hyperventilating if his PaCO2 is at what level?

A

<35mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The only physiologic reason for elevated PaCO2

A

A level of alveolar ventilation inadequate for the amount of CO2 produced and delivered to the lungs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does VA refer to in the PCO2 equation?

A

VA = VE - VD = total volume of lung - dead space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the equation for VE, or total ventilation rate?

A

VE = Total ventilation rate (L/min) = respiratory rate · tidal volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Is dead space ventilated? Is it perfused?

A

Yes; no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Anatomic dead space + all other dead space

A

Physiologic dead space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

3 processes required for gas exchange

A
  1. Gas entering and leaving
  2. Blood flow = perfusion
  3. Diffusion of gases across capillary membrane
20
Q

What is another way to think of VA?

A

VE - VD

21
Q

Level of VE needed to keep PaCO2 constant

A

Minute ventilation requirement

22
Q

In a normal lung, what is PACO2? What is PaCO2?

A

40mmHg

23
Q

In a normal lung, what is PvCO2?

A

45mmHg

24
Q

What is a typical PAO2 for a normal lung?

A

100mmHg

25
Q

Is the PAO2 equal to the PaO2 in a normal lung?

A

No, PaO2 is slightly lower

26
Q

PO2 at sea level

A

159mmHg = 0.21 * 760mmHg

27
Q

PO2 at the trachea

A

150mmHg

28
Q

PaO2 at the terminal respiratory units

A

100mmHg

29
Q

Anatomic unit used by pathologists

10 to 12 terminal respiratory units

A

Acinus

30
Q

At the terminal respiratory unit, is PAO2 = PaO2?

A

No

31
Q

Mass conservation equation for O2

A

PAO2 = PIO2 - (PaCO2 x 1.2)

32
Q

Recall: PACO2~PaCO2

But does PAO2 = measured PaO2?

A

At the level of a single alveolus, yes

At the level of the lung, terminal respiratory unit, or patient, no

33
Q

PaO2 will always be less than PAO2

But how much less?

A

ranges between 5 and 20 mm Hg

34
Q

Calculating age appropriate normal PaO2

A

Normal PaO2 = 100-(0.4 x age)

35
Q

Normal P(A-a)O2 difference

A

[Patient age / 4] + 4

36
Q

Hypoxemia vs hypoxia

A

Hypoxemia: Partial pressure of oxygen (PaO2) in the blood < normal for the subject’s age
Hypoxia: Decreased oxygen supply to organs and tissues

37
Q

What happens to the P(A-a)O2 difference with age?

A

It increases

38
Q

Things that make diffusion faster

A

Large diffusing area
High solubility of gas in barrier and blood
Large difference in gas partial pressures

39
Q

Things that make diffusion slower

A

Thicker barrier membrane

Gases with higher mass

40
Q

Which is more soluble in liquid? CO2 or O2?

A

CO2 is 20 times more soluble than O2

41
Q

About how long does it take for the capillary to reach the alveolar PO2?

A

1/4 of the transit time. Total transit time = .75 sec

42
Q

Capillary reserve time

A

Time left over to reach appropriate levels of PAO2 or PACO2

43
Q

Is the amount of O2 in the end capillary blood diffusion or perfusion limited?

A

Normally it is perfusion-limited – the amount of gas taken up by the blood is limited by the amount of blood flow (not the rate of diffusion)

44
Q

The time in the pulmonary capillary after which the PO2 has reached PAO2

A

Capillary reserve time

45
Q

The typical time it takes for an RBC to traverse the length of a pulmonary capillary

A

Capillary transit time

46
Q

The anatomic dead space can be altered by…

A

Brochodilation

Block 2 Exam 3 (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions