Module 2: O2 Transport

Question 1

oxygen transport assessment

Answer 1

• main determinants are Hgb level and O2-Hgb affinity
• O2 needs to first attach to Hgb for transport around the body, then dissociate from Hgb into plasma for pickup and use by cells. Relationship between O2 and Hgb = affinity for each other
• multiple observable factors can influence affinity between Hgb and O2 and impact O2 supply

Question 2

what are normal Hgb levels for men and women?

Answer 2

men = 140-180 g/L
women = 120-160 g/L

Question 3

what forms is O2 transported in the blood?

Answer 3

1) ~97% is bound to Hgb (measured by SpO2 or SaO2)
3) ~3% is dissolved in plasma (measured by PaO2)

Question 4

SaO2

Answer 4

direct measurement of % of Hgb saturated with O2 obtained from an ABG

Question 5

how is Hgb’s affinity for O2?

Answer 5

has strong affinity; high tendency to bind with O2 molecules allowing it to carry oxygen from the lungs to the body’s tissues and organs

Question 6

what factors can influence the affinity of hemoglobin for oxygen?

Answer 6

level of CO2, pH of blood, presence of other molecules

Question 7

how does Hgb bind to O2 when affinity is increased?

Answer 7

hemoglobin binds with oxygen readily but is slower to release it

Question 8

how does Hgb bind to O2 when affinity is decreased?

Answer 8

Hgb does not bind oxygen as readily, but it releases it easily

Question 9

T or F: oxygen bound to Hgb can be utilized for cellular respiration

Answer 9

F - they must dissociate from each other

Question 10

what does the efficiency of oxygen transport depend on?

Answer 10

the amount of hemoglobin available to carry oxygen and the affinity between the two

Question 11

oxyhemoglobin dissociation curve

Answer 11

represents the relationship between hemoglobin and oxygen, i.e., the affinity, and the factors that influence this relationship

Question 12

describe the Hgb molecule

Answer 12

• four subunits (two alpha and two beta)
• iron is at the core of each subunit and is the binding site for an oxygen molecule
• each subunit combines with one oxygen molecule, making max 4O2 molecules bound to 1 Hgb molecule

Question 13

tense Hgb molecule

Answer 13

in initial stage where nothing is bound to it

Question 14

relaxed Hgb molecule

Answer 14

when O2 change in the next subunit; this change increases the affinity of oxygen to bind

Question 15

cooperativity

Answer 15

increasing/changing affinity

Question 16

saturated

Answer 16

when all four subunits are bound to O2

Question 17

what does the x-axis represent? what does the y-axis represent?

Answer 17

partial pressure of O2; % of Hgb saturation

Question 18

what appearance does the graph have?

Answer 18

a S shape or sigmoid appearance; represents that for any given availability of oxygen, aka our partial pressure at the bottom, how much hemoglobin is going to be saturated with oxygen

Question 19

plateau

Answer 19

means that at this point as we increase the partial pressure more and more, we really don’t see much of an increase in the saturation

Question 20

as Hgb becomes more saturated, affinity to bind to O2 _____

Answer 20

increases (capillaries of alveoli)

Question 21

as availability of O2 ____, less Hgb is saturated with O2

Answer 21

decreases (capillaries in end tissue)

Question 22

right shift
- affinity between Hgb and O2
- where
- cues

Answer 22

• Hgb has less affinity for O2 and unloads O2 easier
  -muscle, end tissue, placenta
• increased CO2; increased acidosis (decreased pH); increase in 2, 3 DPG; increased temp

Question 23

left shift
- affinity between Hgb and O2
- where
- cues

Answer 23

• Hgb has greater affinity for O2, but not unloaded/released easily
• lungs
• decreased CO2; decreased acidosis (increased pH); decreased 2, 3 DPG; decreased temp; fetal Hgb

Question 24

T or F: shifts happen in both directions naturally in the body

Answer 24

True

Question 25

what else can shift the curve?

Answer 25

diseases and physiologic processes

Question 26

3 factors to evaluate when determining if oxyhemoglobin dissociation curve has shifted to the left or right

Answer 26

1) pH
2) PaCO2
3) temp

Question 27

conditions that cause a right shift in curve which decreases affinity

Answer 27

• fever
• acidosis
• increased PaCO2
  *reflect increased tissue metabolism and increased cellular need for O2
  *Right Release

Question 28

conditions that cause a left shift in curve which increases affinity

Answer 28

• decreased temp
• alkalosis (increased pH)
• decreased PaCO2
  *Left shift has all the L’s: Low temp, aLkalosis, Low PACO2

Question 29

investigate

Answer 29

hx - factors directly impacting transport include:
- chronic bleeding
-increased RBC distribution
- anemia
- abnormal Hgb
- recent Hgb results and trends
- recent ABG results and trends

Question 30

observe

Answer 30

sources of acute bleeding, temp