Module 2: O2 Transport Flashcards
oxygen transport assessment
- 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
what are normal Hgb levels for men and women?
men = 140-180 g/L
women = 120-160 g/L
what forms is O2 transported in the blood?
1) ~97% is bound to Hgb (measured by SpO2 or SaO2)
3) ~3% is dissolved in plasma (measured by PaO2)
SaO2
direct measurement of % of Hgb saturated with O2 obtained from an ABG
how is Hgb’s affinity for O2?
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
what factors can influence the affinity of hemoglobin for oxygen?
level of CO2, pH of blood, presence of other molecules
how does Hgb bind to O2 when affinity is increased?
hemoglobin binds with oxygen readily but is slower to release it
how does Hgb bind to O2 when affinity is decreased?
Hgb does not bind oxygen as readily, but it releases it easily
T or F: oxygen bound to Hgb can be utilized for cellular respiration
F - they must dissociate from each other
what does the efficiency of oxygen transport depend on?
the amount of hemoglobin available to carry oxygen and the affinity between the two
oxyhemoglobin dissociation curve
represents the relationship between hemoglobin and oxygen, i.e., the affinity, and the factors that influence this relationship
describe the Hgb molecule
- 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
tense Hgb molecule
in initial stage where nothing is bound to it
relaxed Hgb molecule
when O2 change in the next subunit; this change increases the affinity of oxygen to bind
cooperativity
increasing/changing affinity
saturated
when all four subunits are bound to O2
what does the x-axis represent? what does the y-axis represent?
partial pressure of O2; % of Hgb saturation
what appearance does the graph have?
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
plateau
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
as Hgb becomes more saturated, affinity to bind to O2 _____
increases (capillaries of alveoli)
as availability of O2 ____, less Hgb is saturated with O2
decreases (capillaries in end tissue)
right shift
- affinity between Hgb and O2
- where
- cues
- 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
left shift
- affinity between Hgb and O2
- where
- cues
- 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
T or F: shifts happen in both directions naturally in the body
True
what else can shift the curve?
diseases and physiologic processes
3 factors to evaluate when determining if oxyhemoglobin dissociation curve has shifted to the left or right
1) pH
2) PaCO2
3) temp
conditions that cause a right shift in curve which decreases affinity
- fever
- acidosis
- increased PaCO2
*reflect increased tissue metabolism and increased cellular need for O2
*Right Release
conditions that cause a left shift in curve which increases affinity
- decreased temp
- alkalosis (increased pH)
- decreased PaCO2
*Left shift has all the L’s: Low temp, aLkalosis, Low PACO2
investigate
hx - factors directly impacting transport include:
- chronic bleeding
-increased RBC distribution
- anemia
- abnormal Hgb
- recent Hgb results and trends
- recent ABG results and trends
observe
sources of acute bleeding, temp
