Waters IV

Question 1

For ideal gas exchange, ventilation should be matched to _____.

Answer 1

perfusion

Question 2

For the whole lung, the ventilation-perfusion ratio is given by:

Answer 2

Va/Q, Where Va= total alveolar ventilation and Q= total pulmonary blood flow (aka cardiac output)

Question 3

Why is there less ventilation at the apical end of the lung compared to the base?

Answer 3

Intrapleural pressure is more negative, so transmural gradient is larger.. Thus, alveoli are larger and less compliant and less ventilation occurs

Question 4

Why is there less perfusion at the apical end of the lung compared to the base?

Answer 4

lower intravascular pressures increase resistance

Question 5

T or F. Blood flow and ventilation decrease moving upward in the lung at the same rate

Answer 5

F. Blood flow decreases faster

Question 6

Where is the Va/Q ratio highest?

Answer 6

At the apex because perfusion drops faster than ventilation

Question 7

Would the Va/Q be increased or decreased in a COPD patient?

Answer 7

increased in some regions and decreased in others

Question 8

What is a normal Va/Q?

Answer 8

0.8

Question 9

How does the Va/Q change in pulmonary embolus?

Answer 9

drastically increased

Question 10

What is a shunt?

Answer 10

A situation where there is plenty of perfusion but an airway obstruction (Va/Q is 0)

Question 11

Where is PaO2 highest in the vertical lung? What is it? What is it at the base?

Answer 11

at the apex - 130 mm Hg

base- 89 mm Hg

Question 12

Where is Paco2 highest in the vertical lung? What is it? What is it at the base?

Answer 12

the base- 42 mm Hg

the apex- 28 mm Hg

Question 13

Where in the vertical lung would ventilation be considered “wasted” in relation to perfusion

Answer 13

the apex

Question 14

What is a pathologic consequence of PaO2 being higher in the apex?

Answer 14

organisms that use O2 as a nutrient source flourish in the apex

Question 15

The A-a gradient is roughly 100:105 mm Hg for Po2

Answer 15

This can change in disease states

Question 16

T or F. The A-a gradient of a shunt can be normalized using 100% O2

Answer 16

F.

Question 17

T or F. The A-a gradient decreases in ventilation-perfusion mismatch

Answer 17

F. It increases (but CAN be normalized with 100% O2)

Question 18

What happens in acute respiratory distress syndrome?

Answer 18

loss of barrier function causes fluid to leak into the air spaces and air diffusion is worse

Question 19

How is pulmonary edema fluid cleared by the body?

Answer 19

edema fluid contains Na+ and type I and II pneumocytes move sodium from the alveoli into themselves via ENaC channels on the apical side and use a NaKATPase on the other side to remove it, and then water follows

Question 20

How is oxygen carried?

Answer 20

• dissolved

- bound to hemoglobin

Question 21

T or F. Pao2 is a measure of O2 bound to hemoglobin

Answer 21

F. It is DISSOLVED O2

Only 1.5% of all O2 in the blood is dissolved, the rest is bound to hemoglobin

Question 22

How many molecules of O2 are bound by hemoglobin?

Answer 22

4

Question 23

What is the O2 content of blood?

Answer 23

amount bound to hemoglobin + amount dissolved

= (O2 binding capacity * %saturation) + dissolved O2

Question 24

Which of the following does decreased Hb affect:

a) O2 content of blood
b) O2 saturation
c) arterial Po2

Answer 24

only A

Question 25

What is the eqn. for O2 delivery to tissues?

Answer 25

(Cardiac Output)* O2 content in blood

Question 26

Where specifically does O2 bind to Hb?

Answer 26

central Fe2+ (ferrous) in each subunit

Question 27

Iron in the ferric (Fe3+) state does not bind O2. What is this called?

Answer 27

Methemoglobin

Question 28

T or F. Fetal hemoglobin (HbF) has a higher affinity for O2

Answer 28

T.

Question 29

Define Co-operativity

Answer 29

the reactions of four the subunits occur sequentially, with each combination facilitating the next binding reaction

Question 30

Oxygen diffusion is governed only by what?

Answer 30

the dissolved portion in blood

Question 31

How does the oxygen gradient that exists from the alveoli to blood maintain itself?

Answer 31

Hemoglobin binds it so the dissolved O2 conc. in blood remains low AF (in the capillaries HB dumps O2 and a new gradient is established that promotes diffusion into tissue)

Question 32

What is %saturation defined as?

Answer 32

O2 bound to Hb/max capacity of Hb to bind O2

Question 33

What things decrease binding affinity for O2 (shift to right)

Answer 33

Increased temp, 2,3-DPG, and Co2 (aka decreased pH)

Question 34

Why would increased co2 decrease Hb binding affinity?

Answer 34

both Co2 and H+ can bind to Hb (this is called the Bohr effect)

Question 35

Why would increased temp decrease binding affinity?

Answer 35

heat changes the structure of Hb

Question 36

What is the role of 2,3-DPG?

Answer 36

it helps oxygen dissociate from Hb (unregulated in hypoxia conditions)

Question 37

What factors affect oxygen content of blood?

Answer 37

• CO poisoning

- Anemia

Question 38

How is Co2 transported?

Answer 38

• dissolved in blood
• can bind to Hb (or any amino group of a protein) (accounts for 10-20% of co2 in blood). Called protein carbamylation
• formation of HCO3- (major form 80-90%)

Question 39

How is Co2 transported out tissue?

Answer 39

mostly transformed to H2CO3 first by carbonic anhydrase (rate limiting) than to HCO3- (and H+) within RBCs

Question 40

What is Hamburger;s phenomenon?

Answer 40

When HCO3- enters back into plasma from the cell it is charge compensated by adding a Cl- into the cell which drags H2O causing the cell to swell

Question 41

The Cl- shift is driven by ____

Answer 41

band 3 protein

Question 42

What happens to the H+ in the RBCs when HCO3- exits?

Answer 42

it remains and is buffered by deoxyhemoglobin to prevent acidification and is carried in venous blood this way

Question 43

What is the Bohr effect?

Answer 43

When CO2 is produced by tissues, HCO3-and H+ are produced in the
blood. Due to H+ production, pH becomes lower. The higher H+ concentration
causes increased binding to Hb causing it to bind O2 with less affinity. The
position of the O2 dissociation curve shifts to the right facilitating O2 unloading.