Oxyhemoglobin (HbO2) Dissociation Curve
Also known as HbO2 equilibrium curve
Part of nomogram that graphically illustrates percentage of hemoglobin chemically bound to oxygen at each oxygen pressure
Clinical Significance of the Flat Portion of the Curve
The flat portion means that the increasing PO2 is beyond the 100 torr adds additional oxygen to the blood. 70 to 100 torr
Clinical significance of the steep portion of the curve
Steep portion shows that the hemoglobin moves through the capillaries if the tissue cells. A large amount of oxygen is released from the hemoglobin for only a small decrease in Po2 . Is between 10 to 60 torr
P50
Point of reference on oxyhemoglobin dissociation curve
Represents partial pressure at which hemoglobin is 50 percent saturated with oxygen
Normally, approximately 27 torr
When oxyhemoglobin dissociation curve shifts to left,
P50 decreases
When oxyhemoglobin dissociation curve shifts to right
P50 increases
Factors that Shift Oxygen Dissociation Curve
pH( blood hydrogen ion increases decreased ph )
Temperature (when increases moves to the right, decreases moves to the left)
Carbon dioxide(if it increases the oxyhemoglobin saturation decreases)
2,3-bisphosphoglycerate (BPG)(hemoglobin affinity for oxyge
right shift
oxygen decreases ( affinity decreases gives off oxygen more easily)
ph decreased
P50 increased
PCO2 increased
temp increased
2,3 DPG increased
left shift
oxygen increases ( affinity holds on to the O2)
ph increased
P50 decreased
PCO2 decreased
temp decreased
BPG decreased
COHB
HBf
Total oxygen delivery
Total amount of oxygen delivered or transported to the peripheral tissues
DO2 = QT X (CaO2 X10)
arterial venous oxygen content difference
C(a-v)=CaO2-CVO2
normal value is about 5%
Factors that decrease C(a-v)O2
Increased cardiac output
Skeletal muscle relaxation
Peripheral shunting
Certain posions
Hypothermia
Factors that increase C(a-v)O2
Decreased cardiac output
periods of increased oxygen consumption
Exercise
Seizures
Shivering
Hyperthermia
oxygen consumption VO2
Amount of oxygen extracted by peripheral tissues during period of one minute
Also known as oxygen uptake (VO2)
VO2= QT [C (a-v)o2�10]
It's the difference between cao2 - cvo2 � 10 .then you multiply it by the Qt(cardiac output
Factors that increase VO2
Exercise
Seizures
Shivering
Hyperthermia
factors that decrease VO2
Skeletal muscle relaxation
Peripheral shunting
Certain posions
Hypothermia
Pulmonary Shunting
Portion of cardiac output that moves from right side to left side of heart without being exposed to alveolar oxygen (PAO2)
Clinically, can be subdivided into:
Absolute shuntAlso known as true shunt
Relative shuntAlso known as shunt-like effects
Quantity of O2 BOUND TO HEMOGLOBIN
1.34x HB
For ex 15 �1.34
20.1 vol%O2.
Add saturation to give quantity amount
Ex 20.1 x .97 = 19.5 vol %O2
Clinical Significance of Pulmonary Shunting
10 percent (Normal status)
10 to 20 percent (Indicates intrapulmonary abnormality)
20 to 30 percent (Significant intrapulmonary diseases)
> 30 (Potentially life-threatening
CaO2: content of arterial blood
(Hb�1.34 �SaO2) +(PaO2�0.003)
Oxygen content of mixed venous blood CVO2
(Hb�1.34�SVO2)+ (PVO2�0.003)
CcO2: oxygen content of pulmonary capillary blood
(HB�1.34)+( PAO2�0.003)
Shunt equation
Qs/Qt = CCo2- Cao2/ CCo2- CVo2
*remember in order to find the cco2 must find the PAO2
PAO2
[PB-PH20)(FIO2)- Paco2(1.25)
Dissolved plasma
(PO2� 0.003)
On the dissociation curve if the P50 goes from 27 to 40 what kind of shift is it ?
Right shift
On the dissociation curve if the P50 goes from 27 to 22 what kind of shift is it?
Left shift
Normal hemoglobin for a male
14 to 16
Normal hemoglobin for a female
12 to 15
Secondary poltcythemia
Chronically low arterial blood oxygen levels .