TRANPORT OF OXYGEN

DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
TRANSPORT OF
OXYGEN.

OBJECTIVES.
 Uptake of oxygen by pulmonary blood.
 Transport of oxygen in arterial blood.
 Release of oxygen in tissue.
 Vehicle for transport of oxygen.
Saturday, December 10, 2016

INTRODUCTION
 Transport of gases occurs along
the conc gradient.
 Alveolar air PO2 : 104 mm Hg.
 Arterial blood PO2 :95 mm Hg
 Venous blood PO2: 40 mm Hg.
 Tissue interstitial fluid: 40
mm Hg.

UPTAKE OF OXYGEN BY
PULMONARY BLOOD.
 Alveolar PO2 -104
mm Hg.
 Arterial blood po2 40
mm Hg.
 Conc gradient of 64
mm Hg, transport is
rapid.

TRANSPORT OF OXYGEN IN
ARTERIAL BLOOD.
 PO2 in pulmonary veins
104 mm Hg & in aorta
100 mm Hg.
 Due to venous
admixture
 Bronchial veins mix with
pulmonary capillaries
 Coronary blood through
Thebesian Veins.

TRANSPORT OF OXYGEN IN
ARTERIAL BLOOD.
 Dissolved form
 In combination with
haemoglobin.
 Oxygen in Arterial blood –
20ml/100 ml, in venous
blood 15ml/100ml
 So 5ml/100 ml
transported from lungs to
tissue.

DISSOLVED FORM
 Out of 5 ml transported 0.3 ml
in dissolved form & rest with
Hb.
 As per Henry’s law dissolved gas
is proportional to Po2, so there
is NO LIMIT for this transport as
long as Po2 is high.
 So dissolved O2 at high Po2
( Hyperbaric Oxygen) is used
for oxygenation in certain
poisoning (CO)where Hb is
denatured.

IN COMBINATION WITH
HAEMOGLOBIN.
 Oxygenation of haemoglobin
 Oxygen carrying capacity of haemoglobin
 O2-Hb dissociation curve.
 Shifts in O2-Hb dissociation curve.
 Concept of P50 & its significance.
 O2-Hb dissociation curve of Hb-F
 Effect of carbon monoxide on tranport of O2
 Oxygen dissociation curve for myoglobin.

OXYGENATION OF
HAEMOGLOBIN
 Oxygen combine with
Hb to form loose &
reversible bond, this is
oxygenation & Not
Oxidation, convert
Deoxyhaemoglobin
into Oxyhaemoglobin.
 Time taken 0.1 sec.

OXYGEN CARRYING CAPACITY
OF HAEMOGLOBIN
 1 gm of Hb bind with
1.34ml of O2
 100 ml blood containing Hb
15gm% (15Χ 1.34) bind
20.1 ml of O2
 But due to different shunts
decreases to 19.8 ml out of
which 0.3 ml in dissolved
form & 19.5 ml as
Oxyhemoglobin.

DISADVANTAGE
 Only Disadvantage
with this method is
there is Ceiling with
this transport due to Hb
saturation.
 % Saturation is Avg
saturation of entire Hb
molecule in the blood.

O2-HB DISSOCIATION CURVE.
 When relation between
PO2 & % of Hb saturation
is plotted on graph we get
OXYGEN-HAEMOGLOBIN
DISSOCIATION CURVE.
 It shows that % of Hb
saturation increases with
increase in PO2, but this
relationship is not linear

SIGMOID SHAPED CURVE -
CAUSE
 When 1 molecule of O2
combines with Hb ,
affinity of Hb increases
& so on
 This is called Co-
operative binding
Kinetics.
 Due to this O2-Hb
dissociation curve is
Sigmoid.

Advantage
 Loading Zone – Related
to process of O2 uptake
in lungs.
 Even Po2 falls below 60
mmHg saturation is still
90%, so loading zone
provide margin of safety.

Advantage
 Unloading zone –
related to O2 delivery in
tissue, steep portion
below Po2 60mmHg.
 So that relatively large
Oxygen is liberated at
minor fall in o2 tension.
( Buffering Effect)

SHIFTS IN O2-HB
DISSOCIATION CURVE.
 Shift to Right
-Decreased affinity of
Hb for O2.
 Causes
 PCO2 & pH – Increase in
Pco2 shift curve to
Right – Bohr’s effect.

SHIFTS IN O2-HB
DISSOCIATION CURVE.
 Temperature – increase
temperature is due to increase
heat production, increased
PCo2 due to rapid metabolism,
decreased PO2 due to rapid
consumption & decreased pH
due to lactic acid accumulation.
 2,3-Diphosphoglycerate –
formed during Glycolysis via
EMBEDEN-MEYERHOF
pathway.

SHIFTS IN O2-HB
DISSOCIATION CURVE.
 Shift to left – increase
affinity of haemoglobin
for oxygen.
 Causes –
 Pco2
 H + ion conc
 Temperature
 Fetal haemoglobin

CONCEPT OF P50 & ITS
SIGNIFICANCE.
 P50 – partial pressure of oxygen that produces 50%
of saturation
 Normal P50 – 25-27 mmHg.
 Significance – Hb affinity inversely proportional to
P50 value.
 Decreased p50 – Hb gets saturated at low po2, i.e shift to
left
 Increased p50 - Hb gets saturated at high po2, i.e shift to
right.

O2-HB DISSOCIATION CURVE
OF HB-F
 O2-Hb dissociation
curve shifted to Left
 As its affinity for 2,3-
DPG is less than HbA
 So its affinity to
combine with oxygen
is more than HbA.

EFFECT OF CARBON MONOXIDE
ON TRANSPORT OF O2
 CO has 200 more
affinity for Hb.
 Combines with Hb
forms-
Carboxyhaemoglobin
 Decreases functional Hb
conc.
 And decreases O2
tension & O2 transport.

OXYGEN DISSOCIATION CURVE
FOR MYOGLOBIN.
 Present in Muscle specialised
for sustained contraction
 Dissociation curve is
Rectangular Hyperbola – as
it takes O2 at low pressure
readily
 It does not show Bohr’s effect
 At po2 40 mm Hg it is 95%
saturated & Hb 75%
 Act as temporary store house
of Oxygen

RELEASE OF OXYGEN IN
TISSUE.
 O2 release at Rest
 O2 release during
exercise.

O2 RELEASE AT REST
 Oxygen Delivery – Normal o2 delivery is 1L/min
 Oxygen Consumption – 5ml/100ml/min, so total
is 250 ml/min
 Utilization Coefficient - % of O2 consumed out of
oxygen delivered to tissue.
 250/1000 × 100 = 25%

O2 RELEASE DURING
EXERCISE.
 Depend on Severity of
exercise
 Delivery of oxygen –
increased by
 Increase blood flow due to
increase cardiac output, local
arteriole dilatation, increase
in open capillaries.
 Increase RBC count due to
splenic contraction
 Release of oxygen – by
right sift of curve.

VEHICLE FOR TRANSPORT OF
OXYGEN.
 At PO2 100 mm Hg
 Whole blood – 19.8ml
 Hb soln – 19.5 ml
 plasma soln – 0.3 ml
 At PO2 40 mm Hg
 Whole blood – 5 ml
 Hb soln – 1.5 ml
 plasma soln – 0.18 ml

TRANPORT OF OXYGEN

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TRANPORT OF OXYGEN