Control of CO2 and O2 in alveoli and blood

Question 1

Increase in PaCO2 in blood flowing to the medulla causes increase in (blank). What receptor allows for this?

Answer 1

ventilation

Central chemoreceptor in medulla

Question 2

The peripheral chemoreceptors in carotid and aortic bodies have (blank) effect on the breathing of a normal person at rest at sea level.

Answer 2

little effect

Question 3

When does peripheral chemoreceptors in carotid and aortic bodies begin to drive breathing?

Answer 3

when PaO2 falls below 60 mm HG and when lactic acid is released into the blood during strenuous exercise (lactate threshold)

Question 4

What is the PCO2 ventilation equation?

Answer 4

PaCO2=(VCO2 X 0.863)/VA
VA=rate of alveolar ventilation by lung
VCO2= Rate of CO2 production metabolism

Question 5

What is the alveolar gas equation oxygenation?

Answer 5

PAO2=PIO2-1.2(PaCO2)

Question 6

Buildup of CO2 in the blood causes the pH to (blank)

Answer 6

fall

Question 7

Buildup of CO2 in the blood causes the (blank) to fall

Answer 7

the PAO2

Question 8

What are the two rates that control arterial CO2?

Answer 8

metabolic production of CO2 (VCO2)
Alveolar ventilation (VA)

Question 9

Buildup of CO2 in the blood is due to failure of some component of the (blank). (not an increase in metabolic CO2 production)

Answer 9

respiratory system

Question 10

As you increase CO2 production, your ventilatory rate will (blank) to maintain your CO2

Answer 10

compensate

Question 11

Alveolar ventilation and CO2 production double during moderate exercise in a 24-year old man. Describe the effect on PaCO2 this will have?

Answer 11

The PaCO2 will not changed

Question 12

The terms hyper- and hypoventilation have nothing to do with patient’s (blank X 3)

Answer 12

respiratory rate, depth, or breathing effort!

Question 13

Whether you are running around or sitting still your ventilatory rate will compensate so you will maintain your (blank) levels

Answer 13

CO2

Question 14

What is the definition of hypercapnia?

Answer 14

greater than 45 mm Hg PaCO2 and you will be in hypoventilation

Question 15

What is the definition of Eucapnia?

Answer 15

35-45 mm Hg and normal ventilation

Question 16

What is the definition of Hypocapnia?

Answer 16

less than 35 mm Hg and hyperventilation

Question 17

(blank) must be measured to assess a patient’s state of alveolar ventilation

Answer 17

PaCO2

Question 18

An important clinical corollary of the PaCO2 equation is that we cannot reliably (blank) the adequacy of alveolar ventilation - and hence PaCO2 - at the bedside.

Answer 18

assess

Question 19

What is the definition of hyperventilation?
What is the definition of hypoventilation?
What is the definition of Eucapnia?

Answer 19

less than 35 mm Hg
greater than 45 mm Hg
35-45 mm Hg

Question 20

As PaCO2 increases pH falls if no compensation is present. As PaCO2 increases, PAO2 and PaO2 (blank), unless inspired O2 is supplemented.

Answer 20

fall

Question 21

(blank) is a sign of advanced organ system impairment and is potentially dangerous. It results due to a failure of a component of the respiratory system.

Answer 21

Hypercapnia

Question 22

The only physiologic reason for elevated PaCO2 is (blank) for the amount of CO2 produced and delivered to the lungs.

Answer 22

inadequate levels of alveolar ventilation

Question 23

The rate of alveolar ventilation refers only to the alive volume of lung, dead spaces do not count, so what is the equation for alveolar ventilation?

Answer 23

VA (alive ventilation)= (VE) Total ventilation- (VD) dead space

Question 24

How do you find total ventilation rate (VE)?

Answer 24

(breaths per min) X (tidal volume)

Question 25

What is the space that is ventilated but not perfused called?

Answer 25

``` dead space (i.e. you will have gas entering and leaving but not blood flow and no gas exchange) ```

Question 26

Alveolar space is called alive space because (blank) occurs here

Answer 26

gas exchange

Question 27

What are the 2 types of dead space?

Answer 27

physiologic dead space and anatomic dead space

Question 28

Alive alveoli that receive air, are perfused, and have gas exchanging, dead alveoli do what?

Answer 28

receive air but do not exchange gas

Question 29

What is this? All the airways that are ventilated but not perfused. Can never take part in gas exchange b/c of normal anatomy, ~150 ml What is this? anatomic + all other dead spaces

Answer 29

anatomic dead space | physiologic dead space (VD)

Question 30

What are the three processes required for gas exchange?

Answer 30

1. gas entering and leaving 2. blood flow= perfusion 3. diffusion of gases across capilllary membrane

Question 31

(blank)= the total amount of air breathed per minute that is exposed to "live" alveoli

Answer 31

alveolar ventilation

Question 32

What happens when you have inadequate total ventilation (VE), or an increase in VD (lots of dead alveoli, or both?

Answer 32

hypercapnic

Question 33

``` What do these do? Massive obesity Respiratory muscle weakness Severe pulmonary fibrosis Central nervous system depression ```

Answer 33

limit the rate or depth of breathing

Question 34

What is the minute ventilation requirement?

Answer 34

the level of VE (total ventilation) needed to keep PaCO2 constant

Question 35

When VD (ventilatory dead space) increases, minute ventilation requirement (blank).

Answer 35

increases | i.e. a rise in VE is needed to keep PaCO2 constant

Question 36

What is the minute ventilation requirement?

Answer 36

the level of VE (total ventilation) needed to keep PaCO2 constant

Question 37

When VD (ventilatory dead space) increases, minute ventilation requirement (blank).

Answer 37

increases | i.e. a rise in VE is needed to keep PaCO2 constant

Question 38

PaCO2 is elevated at (blank) mm Hg

Answer 38

50

Question 39

The PCO2 equation states that the only physiological reason for elevated PaCO2 is a level of (blank) inadequate for the amount of CO2 produced and delivered to the lungs.

Answer 39

inadequate alveolar ventilation

Question 40

(blank) is characterized by destruction of gas-exchanging air spaces, i.e., the respiratory bronchioles, alveolar ducts, and alveoli. Their walls become perforated and later obliterated with coalescence of small distinct air spaces into abnormal and much larger air spaces. V/Q goes (blank) .

Answer 40

Emphysema | up

Question 41

In a normal lung does PAO2 equal the PaO2?

Answer 41

no it does not!

Question 42

How do you find the partial pressure of a gas in air?

Answer 42

multiply the percentage of that gas in the air by the barometric pressure. i.e what is the PO2 of gas at sea level? A: .21 X 760 mm Hg= 159 mm Hg

Question 43

What is the partial pressure of oxygen in reno? How do you find the PIO2?

Answer 43

.21 X 680=143 | (680-47)X.21

Question 44

What are these: Region in which gas phase diffusion is so rapid that the PAO2 and PACO2 are uniform throughout the unit. All alveolar ducts and their alveoli from proximal (first) respiratory bronchiole

Answer 44

Terminal Respiratory unit->physician's working alveolus

Question 45

What is this: Anatomic unit used by pathologists 10 to 12 terminal respiratory units

Answer 45

the acinus

Question 46

in the single alveolus, the PACO2 equals the (Blank) and the PAO2 equals the (blank)

Answer 46

PaCO2 | PaO2

Question 47

In the terminal respiratory unit the Ave PAO2 (blank) the PaO2.

Answer 47

does not equal

Question 48

What does O2 expired equal?

Answer 48

=O2 inspired - O2 consumed by the body

Question 49

Is PAO2 and PIO2 and PaCO2 calculated or measured?

Answer 49

PAO2 and PIO2 is calculated | PaCO2 is measured

Question 50

What does PAO2 depend upon?

Answer 50

specific environmental conditions of the patient (i.e the PIO2)

Question 51

Is PAO2 and PIO2 and PaCO2 calculated or measured?

Answer 51

PAO2 and PIO2 is calculated | PaCO2 is measured

Question 52

Does PAco2 equal PaCO2? | Does PAO2 equal measured PaO2?

Answer 52

Yes | Yes at level of single alveolus, but at the level of the lung, terminal respiratory unit or patient then NO!

Question 53

PAO2 calculated from the alveolar gas equation is (blank) as the measured PaO2 from an ABG even in a healthy individual with no gas exchange problems

Answer 53

not the same

Question 54

PaO2 will always be (blank) than PAO2. What is a normal difference?

Answer 54

less | between 5 and 20 mm Hg

Question 55

What is the equation for normal PaO2?

Answer 55

Normal PaO2=100-(0.4 X age)

Question 56

What is the normal P(A-a)O2 difference?

Answer 56

Normal P(A-a)O2 difference = [Patient age / 4] + 4

Question 57

What is this? Partial pressure of oxygen (PaO2) in the blood < normal for the subject’s age It can also be defined as an oxygen content in the blood < normal for the subject’s age

Answer 57

hypoxemic

Question 58

What is this? Decreased oxygen supply to organs and tissues Oxygen delivery to cells is insufficient for the demand Does not require that the pO2 in the blood is low But, can caused by hypoxemia.

Answer 58

hypoxia

Question 59

``` What are these causes of? Respiratory causes Chronic obstructive pulmonary disease Choking, asphyxiation, smoke inhalation, suffocation, carbon monoxide poisoning Circulatory causes Content of the blood Cyanide toxicity Accumulation of abnormal hemoglobin in blood Anemia Poor Blood Circulation Very low blood pressure Ischemic heart disease Heart failure Shock ```

Answer 59

hypoxia

Question 60

What are the three stages of diffusion of gases?

Answer 60

1) In the lung 2) Across the pulmonary capillary membrane and the RBC membrane 3) RBC interior to the Hb (O2) or from Hb to RBC interior (CO2)

Question 61

During inspiration what is happening in the conducting zone and the respiratory zone?

Answer 61

conducting zone-> gas is flowing | respiratory zone-> gas is diffusing passively

Question 62

What makes diffusion faster?

Answer 62

Large diffusing area (50-100 m) High solubility of gas in barrier and blood Large difference in gas partial pressures -CO2 = 45-40 = 5 -PO2 = 100-40 = 60

Question 63

What makes diffusion slower?

Answer 63

Thicker barrier membrane -Normal is ~ 0.3 µm Gases with higher mass

Question 64

CO2 is (blank) times more soluble than O2

Answer 64

20

Question 65

In a fair fight, CO2 diffuses (blank) times faster than O2 across the alveolar membrane

Answer 65

17

Question 66

RBC capillary transit time is sufficient for (blank) to reach PAO2 under normal conditions

Answer 66

blood

Question 67

capillary transit time is (blank) during exercise

Answer 67

shorter

Question 68

RBC capillary transit time is sufficient for blood to reach (blank) under normal conditions

Answer 68

PACO2

Question 69

Is diffusion limited?

Answer 69

yes

Question 70

Is perfusion limited?

Answer 70

yes

Question 71

Diffusion is (blank) the process that limits the amount of O2 in the end capillary blood. Normally it is (blank) – the amount of gas taken up by the blood is limited by the amount of blood flow (not the rate of diffusion)

Answer 71

not normally | perfusion-limited

Question 72

What are these? Severe exercise- capillary transit time is shortened Pressure differences across membrane are lower (high alt) Combination of the two

Answer 72

challenges to the diffusion of gases systems