Transport of O2 in blood:

1. Some dissolved

1.5% at normal atmospheric pressure

2. Most combined with hemoglobin

98.5%

Fe2+

Oxygenation is reversible

ml O

2 /

10

0 m

l blo

od

2

1

• Each gm Hb binds 1.34 ml O2

• Each 100 ml blood has 15 g Hb1

2

Blood nearly fully oxygenated even if PO2 < 100 mmHg

Hemoglobin gives up large volume of O2 for a small drop in PO2 at tissues

Factors which influence O2 binding to HB

O2 affinity for Hb* is decreased by:

PCO2

pH acidosis

temperature

2,3 diphosphoglycerate

* affinity = shift of O2–Hb curve to right

= easier unloading of O2

CO2 (ml•dl–1) SO2 (ml•dl–1)

O2 carrying capacity of Hb at a particular

PO2 is decreased by PCO2 (Bohr effect)

Carbon monoxide CO1. Odourless, colourless, non-irritant, no cyanosis

2. Combines with Hb at O2 binding site

3. CO affinity for Hb is 200 times that of O2 for Hb, so if CO at 0.1% in air and O2 at 21%

1/2 Hb—CO and 1/2 Hb—O2

at CO of 0.2% ~ nearly all Hb—CO

4. Management

~ remove from source CO

~ provide Pure O2 ( relative O2 pressure)

~ stimulate ventilation with some CO2

Oxyhemoglobin Dissociation

Curves

In Training:

Vital Capacity Provision of O2

Hb

Cardiac Output

Muscle capillary density

Red blod cell 2,3-DPG

Mitochondria + oxidative enzymes

O2 carrying capacity

Hypoxia: availability of O2 for use by cells

1. availability O2 2. Pulmonary problems:

i) ventilationii) ventilation / perfusion inequalitiesiii) diffusion

3. Venous arterial shunts4. Inadequate transport and delivery

i) anemia; abnormal Hbii) general circulationiii) local circulationiv) edema ( diffusion)

5. Inadequate ability to use O2

i) poisoning cellular enzymes e.g. cyanideii) oxidative enzyme activity e.g. vit B1 deficiency

O2 Transport Summary

• Forms in which O2 is transported in blood

• Hemoglobin

• Hb—O2 dissociation curve

• Factors affecting affinity of Hb for O2

• Carbon Monoxide

• Effects of training

• Causes of hypoxia