Oxyhemoglobin Dissociation curve

Question 1

what is the P50

Answer 1

P50 is the partial pressure of O2 at which hemoglobin is 50% saturated by O2

Question 2

what is the normal value for P50?

Answer 2

26-28mmHg

Question 3

what SO2 corresponds to PO2 of 40 and 60

Answer 3

SPO2 90 = PaO2 60

SPO2 70 = PaO2 40

(start at SpO2 90 and PaO2 60 then go down by 10’s 80 is 50, 70 is 40, 60 is 30 so on)

Question 4

is the following normal for a mixed venous blood gas?

PO2 40mmHg and O2 sat 70%

Answer 4

yes

Question 5

ODC Graph:

just look and see it

Answer 5

Question 6

ODC Graph:

what part of the graph is the loading region? mark w/ blue

Answer 6

Question 7

ODC Graph:

what part of the graph is the unloading region? mark with yellow

Answer 7

Question 8

ODC Graph:

point out the P50

Answer 8

Question 9

ODC Graph:

show the PO2 if the O2 sat in 90 and 70

Answer 9

90 = 60

70 = 40

Question 10

what is the significance of the flat portion of the ODC?

Answer 10

it facilitates the loading of O2 by the blood, bc in the flat portion of this curve, large changes in the partial pressure of O2 in artial blood (PaO2) produce only small changes in Oxygen saturation (SaO2)

Question 11

what is the significance of the steep portion of the ODC?

Answer 11

it facilitates unloading of O2 at tissues b/c large amounts of O2 are unloaded from Hgb (large decrease in O2 sat) in response to small chages in the partial presuure of oxygen

Question 12

Shifts in the OCD:

where do you look to see if a shift occured?

Answer 12

P50 normal 26-28

Question 13

Shifts in the OCD:

is this a right or left shift

Answer 13

Left shift

Question 14

Shifts in the OCD:

is this a right or left shift

Answer 14

right shift

Question 15

Shifts in the OCD:

does the left or right shift havea GREATER affinity (hold on to) for oxygen?

Answer 15

Left shift

Question 16

Shifts in the OCD:

does a right or left shift have a lesser affinity ( give off) to oxygen

Answer 16

right shift

Question 17

Shifts in the OCD:

a P50 of what indicates left shift?

Question 18

Shifts in the OCD:

A P50 of what indocates a right shift?

Answer 18

P50 > 28 mmHg

Question 19

Shifts in the OCD:

what factors cause a left shift?

Answer 19

• Decreased temp
• Increased pH (alkolosis/ decreased H+ concentration)
• Decreased PcO2
• Decreased concentration of 2,3-DPG
• Fetal Hemoglobin (HbF)
• Carboxyhemoglobin (200xs affinity than O2)
• Methemoglobin

Question 20

Shifts in the OCD:

in general is a left shift increased or decreased metabolism

Answer 20

Decreased metabolism

Question 21

Shifts in the OCD:

what factors cause a right shift?

Answer 21

• Increased temp
• Decreased pH (acidosis, increased H+ concentration)
• Increased PcO2
• Increased 2,3-DPG
• Maternal Hb
• Sickle cell (Hbs)

Question 22

Shifts in the OCD:

is a right shift considered an increase or decrease in metabolism?

Answer 22

Increased

Question 23

Shifts in the OCD:

mneumonic for right shift

Answer 23

R- rightward shift

I- Increased PcO2

increased 2,3-DPG- G

H- hydrogen ions increased

T- temp increased

S- sickle cell

Question 24

what is the Bohr Effect

Answer 24

dr. bohr studied factors that shifted the OCD curve

Specifically Bohr assessed how CO2 shifts the OCD

so the Bohr effect refers to the shift in the OCD in response to increase ir decrease in PCO2

Question 25

Shifts in the OCD:

Administration of opioids shift the OCD curve in which direction? why?

Answer 25

opioids produce respiratory depression, so CO2 accumulates and the OCD curve shifts to the right

Question 26

Shifts in the OCD:

when there is a _____ shift in the OCD curve the amount of O2 carried by Hgb increases (loading of O2 is facilitated)

Answer 26

Leftward

Question 27

Shifts in the OCD:

when there is a _____ shift in the OCD curve the amount of O2 carried by Hgb is reduced (unloading of O2 is facilitated)

Answer 27

rightward

Question 28

is the Oxygen release from Hgb to the tissue increased or decreased by acidosis? alkolosis? explain.

Answer 28

• Acidosis there is a right shift, which facilitates the unloading of O2 at the tissues, therby increasing O2 delivery.
• Alkalosis there is a left shift, which diminishes unloading of O2 at the tissues, so O2 delivery is decreased