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Lectures on respiratory physiologyLectures on respiratory physiology
Blood gas transportBlood gas transport
PO2 = 0.21 x 760 mm Hg
= 160 mm Hg
As PB = 760 mm Hg
CONCENTRATION AND PARTIAL PRESSURE
[O2] = 21 ml/dl
FO2 = 0.21
DRY AIR: 21% IS OXYGENO2 MOLECULESIN AIR
PO2 = 0.21 x 713 mm Hg
= 150 mm Hg
PB = 760 mm Hg
PDRY = 713 mm Hg
37oCEFFECT OF WATER VAPOR
PH2O = 47 mm Hg
WATER
O2 IN PHYSICAL SOLUTION
AIR: PO2 = 150 mm Hg
37oC
AIR
AFTER EQUILIBRATION,
WATER: PO2 = 150 mm Hg
AIR: [O2] = 21 ml/dl
WATER: [O2] = 0.45 ml/dl
SOLUBILITY = 0.45 / 150 = 0.003 ml/(dl.mmHg)
37oC
TRANSPORT OF O2 IN SOLUTION DURING EXERCISE
Solubility = 0.003 ml/(dl.mmHg)
[O2] = 0.3 ml/dl = 3 ml/liter
PO2 in arterial blood = 100 mm Hg
Cardiac output = 30 liters/min
Maximum O2 available = 90 ml/min
But O2 requirement is 3000 ml/min
Structure of hemoglobin
Normal cells Sickle cells
Oxygen dissociation curve
0 20 40 60 80 1000
20
40
60
80
100
PO2 , mm Hg
O2 - Hemoglobin Dissociation Curve
O2
SA
TU
RA
TIO
N ,
%
ARTERIAL BLOOD
VENOUS BLOOD
P50
27
TOTAL O2 IN BLOOD IS THE SUM
OF Hb-BOUND AND DISSOLVED O2
TOTAL [O2] = 1.39 x [Hb] x % SATURATION/100
+ 0.003 x PO2
TOTAL O2 IN ARTERIAL BLOOD
(1.39 x 15 x 0.97) + (0.003 x 100)
= 20.5 ml/dl
Effects of changing hemoglobin concentration
Shifting the O2 dissociation curve
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
100
110
PARTIAL PRESSURE, mm Hg
CO-Hb DISSOCIATION CURVES
AT
UR
AT
ION
, % CO
O2
Effects of CO on the O2 dissociation curve
Carbon dioxide is carried in the blood in three forms
1. Dissolved
2. As bicarbonate
3. As carbamino compounds
Solubility of Oxygen 0.003 ml/(dl.mmHg)
Solubility of Carbon Dioxide 0.067 ml/(dl.mmHg)
Carriage of CO2 in the blood
CO2 + H2O H2CO3
C.A.
H2CO3 H+ + HCO3-
Formation of bicarbonate
Hb.NH2 + CO2 Hb.NH.COOH
Formation of carbamino compounds
Uptake of CO2 in systemic capillaries
Carriage of CO2 in the blood
CO2 dissociation curves
Comparison of O2 and CO2 dissociation curves