Hypoxia

The Department of Pathophysiology

Guo lirong

Definition of hypoxia (What is hypoxia?)

Parameters of Blood Oxygen

HypoxiaMain points to study

External respiration

BloodBlood CirculationCirculation

Tissue Tissue cellscells

OxygenOxygen SupplySupply

OxygenOxygenUtilizationUtilization

Hypoxia

Definition

Hypoxia is the commonest pathological process ， which is defined as that cells can not obtain enough oxygen or can not fully utilize oxygen ， thus leading to changes in their metabolism ， function ， or structure.

Hypoxia

1.Partial pressure of oxygen1.Partial pressure of oxygen （（ POPO22

））2.Oxygen binding capacity2.Oxygen binding capacity （（ COCO2 max2 max ））

3.Oxygen content3.Oxygen content （（ COCO22 ））

4.Oxygen saturation4.Oxygen saturation （ （ SOSO22 ））

Parameters of Blood OxygenHypoxia

Partial pressure of oxygen （ PO

2 ）

1.Definition ： the tension produced by oxygen molecules physically dissolved in plasma.

2.Normal value ： PaO2=13.3kPa(100mmHg)

PvO2=5.33kPa(40mmHg)

Hypoxia

Oxygen binding capacity （ CO2ma

x ） 1. Definition ： It is the maximum amount of oxygen that can be combined to hemoglobin in 100 ml of blood.

2.Normal value ： 20ml/dl

Hypoxia

Oxygen content （ CO2 ）

1.Definition ： It is the actual content of oxygen in 100ml blood.

2.Normal value ： CaO2=19ml/dl CvO2=14ml/dl

Hypoxia

Arteriovenous oxygen content (Ca-vO2)

19ml/dl 14ml/dl

5ml/dl

O2O2 O2O2 O2O2 O2O2 O2O2A V

Definition: It is the difference of oxygen content between arterial blood and mixed venous blood.Normal value ： 5ml/dl

Definition: It is the percentage of hemogl

obin present as oxyhemoglobin.

Oxygen saturation (SO2)

Normal value ： SaO2=95%; SvO2=70%

CO2-dissolved O2

CO2max100%

=SO2

Hypoxia

P50

Definition: P50 is a parameter reflecting t

he affinity of Hb to oxygen; it is the O2 p

ressure required to sturate 50% of Hb.

Normal value ： 26~28 mmHg

Dissociation curve of oxyhemoglobinDissociation curve of oxyhemoglobin

20

40

60

80

100

20 40 60 80 100

Hb

Sat

ura

tion

(%

Hb

Sat

ura

tion

(%

))

PaOPaO22 (mmHg) (mmHg)

pH↓pH↓2,3-DPG↑2,3-DPG↑CO2 ↑↑Temperature↑↑

Leftward-shifteLeftward-shifted curve:d curve:

Rightward-shifteRightward-shifted curved curve

Hypoxia