Lecture 15 Flashcards
Exam 3
What is the solubility of Oxygen in aqueous solution?
0.003mL of O2/ mmHg
What is the content of O2 dissolved in a dL of blood if PO2 is 100mmHg like in arterial blood?
0.3mL of O2 in each dL of arterial blood
What is the content of O2 dissolved in a dL of blood if PO2 is 40mmHg like in venous blood?
0.003 x 40 mmHg = 0.12 mL of O2 in each dL of venous blood
What is the oxygen carrying capacity of hemoglobin?
1.34 mL of O2 per gram of Hb
What is the Hb value we use for a healthy patient in our class?
15 g/dL
What is the total amount of oxygen we can carry if our patient has a normal Hb of 15 g/dL?
1.34 mL O2/ g x 15 g/dL = 20.1 mL O2 /dL of blood bound to Hb
Describe the structure of fetal Hb…
it has a pair of alpha subunits and a pair of gamma subunits.
Describe the structure of adult Hb…
it has a pair of alpha subunits and a pair of beta subunits.
What is different between adult and fetal Hb w/ regards to oxygen?
Fetal Hb has a higher affinity for O2 than adult Hb, which facilitates the movement of O2 downhill from mom to baby.
Which organ is responsible for making Hb?
the kidneys! They make epoetin which is used to make Hb.
What is myoglobin? Where is it?
It is in the skeletal muscles and has a much higher affinity for O2 compared to adult Hb
What is the total oxygen content in a dL of blood with a PO2 of 100 mmHg?
20.1 mL O2 bound to Hb + 0.3 mL 02 dissolved in the blood
Why is the majority of oxygen bound to Hb versus dissolved?
It is not very soluble
What are the two problems CO causes for O?
it takes up a binding site on Hb, that O2 cannot occupy (cuts down the O2 carrying capacity). It also increases the Hb affinity for O2 (in a bad way) and Hb cannot unload to O2 to the tissues that need it
What does anemia do to the Oxygen carrying capacity?
it decreases O2 carrying capacity even if all the binding sites on Hb are completely occupied
How does CO impact the oxyhemoglobin dissociation curve?
It shifts the curve to the left because CO increases Hb’s affinity for O2
How much O2 is bound to Hb (content) if SaO2 is 100%? How do you calculate this?
~20 mL O2
carrying capacity for O2 x SaO2 = 20.1 mL O2/dL of blood x 100% ~20 mL of O2
How much O2 is bound to Hb if SaO2 is 75%? (venous blood)
20.1 mL O2 /dL x 75% = 15.08 mL (~15mL) O2
Where is the Hb saturation lower than 75%?
In the coronary sinus (Hb sat ~25%). The heart is set up to extract 75% of the O2 off the Hb delivered to the coronaries (efficient, but low margin of error)
In general a leftwards shift in the oxyhemoglobin curve corresponds to a ______ O2 affinity and a rightwards shift corresponds to a _____ O2 affinity
Left= higher affinity for O2
Right= lower affinity for O2
What is the normal oxygen demand at rest per minute?
250 mL of O2 /min is needed by the tissues at rest
If the O2 content in arterial blood ~20 mL of O2 and the O2 content in venous blood is ~15 mL of O2, how much O2 is dropped off to the tissues?
5 mL O2 /dL
demand is 250 mL O2 /min
So CO…. 250 mL/min / 5mL/dL = 50 dL/min or 5L/min (Fick equation!)
What are four things that shift the oxyhemoglobin curve to the left?
alkalosis (higher pH)
lower PCO2
no 2,3-BPG/2,3-DPG (blood products)
lower body temperature
What are four things that shift the oxyhemoglobin curve to the right?
acidosis (low pH)
Higher PCO2
increased 2,3-BPG/2,3-DPG
higher temperature
