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