‫فيزيولوژي گازهاي خون شرياني‬
Gas Exchange
Partial Pressure •
Each gas in atmosphere contributes to the entire –
atmospheric pressure, denoted as P
Gases in liquid •
Gas enters liquid and dissolves in proportion to its –
partial pressure
O2 and CO2 Exchange by DIFFUSION •
PO2 is 104 mmHg in alveoli and 40 in alveolar –
capillaries
PCO2 is 45 in alveolar capillaries and 40 in alveoli –
Partial Pressures
Oxygen is 21% of atmosphere
760 mmHg x .21 = 160 mmHg PO2
Co2 N2
o2
‫تغييرات فشار گاز اكسيژن‬
‫در طي تنفس‬
‫‪160‬‬
‫‪149‬‬
149
40
104
Haemoglobin
4 x Haem group
+
4 x Polypeptide chain
Adaptation of RBC in transport of
gases
Lack a nucleus
Biconcave disc
Lack a nucleus •
Biconcave disc •
The transport of oxygen in blood
- Haemoglobin
• Hb + 4O2 → Hb(O2)4
• Over 98% of O2 is carried in this way
Oxygen Transport
• Method
Percentage
• Dissolved in Plasma
1.5 %
• Combined with Hemoglobin
98.5 %
Bound to Hgb
Dissolved
‫انتقال اكسيژن از خون به بافتها‬
‫• درصد اشباع هموگلوبين ازاكسيژن‬
‫• هرگرم هموگلوبين مي تواند با ‪ 34/1‬ميلي ليتر اكسيژن تركيب شود‬
‫حال اگر در هر ‪ 100‬س ي س ي خون ‪ 15‬گرم هموگلوبين باشد ‪:‬‬
‫در هر ‪ 100‬ميلي ليتر خون‬
‫‪ 1.34*15=20.1‬اكسيژن خواهيم‬
‫داشت و در صد اشباع اكسيژني برابراست با‪:‬‬
‫حداكثر مقداراكسيژن كه مي تواند وحود داشته باشد ‪/‬مقداراكسيژن موجود در‪ 100‬س ي س ي=‪Saturation‬‬
‫منحني تجزيه اكس ي‬
‫هموگلوبين‬
‫‪artery‬‬
‫‪vein‬‬
FACTORS AFFECTING O2-Hb
DISSOCIATION CURVE
PCO2
TEMPERATURE
2,3 – DIPHOSPHOGLYCERATE
PRESENCE/PERCENTAGE OF FETAL Hb
pH
Partial Pressures
Carbon dioxide is .04% of atmosphere •
760 mmHg x .0004 = .3 mm Hg PCO2 •
This mixes with high CO2 levels from •
residual volume in the alveoli to arrive at
PCO2 of 40 mmHg
‫تغييرات فشار گاز دي اكسيد‬
‫كربن در طي تنفس‬
‫‪03‬‬
‫‪40‬‬
03
45
40
40
Co2 transported as:
80%
70%
60%
50%
40%
70%
30%
20%
23%
10%
0%
7%
CO2
Hg-co2
HCO3
N2
O2
CO2
H2O
What Is An ABG?
pH
[H+]
PCO2 Partial pressure
CO2
PO2
O2
Partial pressure
HCO3 Bicarbonate
SaO2 Oxygen Saturation
What is an ABG?
The Components
pH / PaCO2 / PaO2 / HCO3 / O2sat –
Desired Ranges
pH - 7.35 - 7.45
PaCO2 - 35-45 mmHg
PaO2 - 80-100 mmHg
HCO3 - 21-27
O2sat - 95-100%
–
–
–
–
–
•
•
Acid/Base Relationship
H2O + CO2

H2CO3

HCO3 + H+
PH=6.1 +logHCO3 /.03*PCO2
The Terms
ACIDS
Acidemia –
Acidosis –
Respiratory •
CO2
Metabolic •
HCO3
•
BASES
Alkalemia –
Alkalosis –
Respiratory •
CO2
Metabolic •
HCO3
•