597 - 598 - Respiratory Physio

Question 1

Do the lungs intrinsically tend to collapse inward or expand? How about the chest wall?

Answer 1

Lungs - collapse inward

Chest wall - spring outward

Question 2

What forces are balanced at FRC?

Answer 2

1. Inward pull of lung
2. Outward pull of chest wall
   Total pressure of system = atmospheric pressure

Question 3

At FRC, what is the pressure of:

• airways?
• alveoli?
• intrapleural space?

Answer 3

• airways = 0
• alveoli = 0
• intrapleural space = negative to prevent pneumothorax

Question 4

At FRC, describe the PVR (pulmonary vascular resistance).

Answer 4

PVR is at minimum

Question 5

What is lung compliance?

Answer 5

change in lung volume for a given change in pressure

Question 6

Explain how each of the following affect lung compliance:

• pulmonary fibrosis
• emphysema
• pulmonary edema
• normal aging
• pneumonia

Answer 6

• pulmonary fibrosis ↓
• emphysema ↑
• pulmonary edema ↓
• normal aging ↑
• pneumonia ↓

Question 7

What is the basic structure of hemoglobin?

Answer 7

4 polypeptide subunits (2 α and 2 β)

Question 8

What are the two forms of hemoglobin?

Answer 8

T (taut) form with low affinity for O2

R (relaxed) form with high affinity for O2 (300x)

Question 9

Hb exhibits ______ (positive/negative) cooperativity and ______ (positive/negative) allostery.

Answer 9

positive; negative

Question 10

Which factors favor the taut form of Hb?

Answer 10

Increase in:

1. Cl-
2. H+
3. CO2
4. 2,3-BPPG
5. Temperature

Question 11

When Hb transitions to the taut form, what happens to O2?

Answer 11

O2 unloads

“Taut in Tissues, Relaxed in Respiratory tract”

Question 12

What subunits make up fetal Hb?

Answer 12

2 α and 2 γ subunits

Question 13

Does fetal Hb have lower or higher affinity for O2 than adult Hb?

Answer 13

Higher affinity (b/c has lower affinity for 2,3-BPG)

Question 14

Why do hemoglobin modifications lead to tissue hypoxia?

Answer 14

↓ O2 sat and ↓ O2 content

Question 15

What is methemoglobin?

Answer 15

Oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has ↑ affinity for cyanide

Question 16

Is iron in Hb normally in an oxidized or reduced state? What is this form called?

Answer 16

reduced; ferrous (vs. oxidized ferric)

Question 17

How does methemoglobinemia present?

Answer 17

cyanosis and chocolate-colored blood

Question 18

How is methemoglobin involved in the treatment of cyanide poisoning?

Answer 18

Nitrates are used to oxidize Hb to methemoglobin, which binds cyanide (then thiosulfate can be used to bind the cyanide → thiocyanate → renal excretion)

Question 19

How is methemoglobinemia treated?

Answer 19

methylene blue

Question 20

How do nitrates cause poisoning?

Answer 20

oxidizing Fe2+ → Fe 3+ (i.e. Hb → Met Hb → decreased affinity for O2)

Question 21

What is carboxyhemoglobin?

Answer 21

Form of Hb bound to CO in place of O2

Question 22

Why is carboxyhemoglobin no bueno?

Answer 22

Causes ↓ oxygen-binding capacity with a left shift in the oxygen-hemoglobin dissociation curve → ↓ O2 unloading in tissues

Question 23

Compare the affinity of Hb for CO vs. O2:

Answer 23

CO = 200x greater

Question 24

What shape does the oxygen-hemoglobin dissociation curve? Why?

Answer 24

sigmoid due to positive cooperativity (i.e. tetrameric Hb molecule that can bind 4 O2 molecules and has a higher affinity for ea. subsequent O2 molecule bound)

Question 25

What is the shape of the oxygen-myoglobin dissociation curve? Why?

Answer 25

It is a steep curve that quickly flattens without sigmoid curve. Myoglobin is monomeric → does not show positive cooperativity → no sigmoid curve

Question 26

What happens when the O2-Hb dissociation curve shifts to the right?

Answer 26

↓ affinity of Hb for O2 (facilitates unloading in tissues)

Question 27

An increase in which factors cause a right shift in the O2-Hb dissociation curve?

Answer 27

BAT ACE:
BPG (2,3-BPG)
Altitude
Temperature
Acid
CO2
Exercise

Question 28

Is the fetal Hb-O2 dissociation curve shifted to the right or left relative to the adult curve?

Answer 28

Left (has a higher affinity for O2)

Question 29

What is the equation for O2 content of the blood?

Answer 29

O2 content = (O2 binding capacity x % saturation) + dissolved O2

Question 30

In normal conditions, how much O2 (mL) can 1g Hb bind to?

Answer 30

1 g Hg can bind 1.34 mL O2

Question 31

What’s the normal Hb concentration in blood?

Answer 31

15 g/dL

Question 32

At what concentration of deoxygenated Hb does cyanosis occur?

Answer 32

> 5 g/Dl

Question 33

What is a normal O2 binding capacity?

Answer 33

20.1 mL O2/dL

Question 34

When Hb levels in the blood fall, how are the following affected:

• O2 content of arterial blood
• O2 saturation
• arterial PO2

Answer 34

↓ O2 content of arterial blood

No change in O2 saturation or arterial PO2

Question 35

What is the equation for O2 delivery to tissues

Answer 35

O2 delivery to tissues = cardiac output x O2 content of blood

Question 36

In CO poisoning, describe the following:

• Hb level
• % O2 sat of Hb
• Dissolved O2 (PaO2)
• Total O2 content

Answer 36

• Hb level: normal
• % O2 sat of Hb: ↓ (CO competes with O2)
• Dissolved O2 (PaO2): normal
• Total O2 content: ↓

Question 37

In anemia, describe the following:

• Hb level
• % O2 sat of Hb
• Dissolved O2 (PaO2)
• Total O2 content

Answer 37

• Hb level: ↓
• % O2 sat of Hb: normal
• Dissolved O2 (PaO2): normal
• Total O2 content: ↓

Question 38

In polycythemia, describe the following:

• Hb level
• % O2 sat of Hb
• Dissolved O2 (PaO2)
• Total O2 content

Answer 38

• Hb level: ↑
• % O2 sat of Hb: normal
• Dissolved O2 (PaO2): normal
• Total O2 content: ↑