Blood - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 15

Tabl e 1. 8. Value ranges of arterial blood gas analysis.

Parameter Range

pH 7.35-7.45

H + 35-45 nmol/l

p O 2 9.3-13.3 kPa

p CO 2 4.7-6.0 kPa

HCO3 − 22-26 mmol/l

HPO4 −−

0.8-1.5 mmol/l

1.3.5 Blood Gas

Analysis of arterial blood gas determine the concentrations of carbon dioxide,
oxygen, and bicarbonate, as well as blood pH (Table 1.8 ). One of the main tasks
of the blood circulation is to transport dissolved gas, such as oxygen and carbon
dioxide. Oxygen dissolves less and needs to bind to a suitable transporter in
erythrocytes — hemoglobin. Oxygen-carrying capacity is related to the quantity
of oxygen transported by hemoglobin. Oxygen transport relies on conditions and
rate of its association and dissociation.
Hemoglobin loading and unloading, indeed, happen under different conditions.
The higher the oxygen availability, the greater the quantity of oxygen taken up by
hemoglobin. The lower the local oxygen concentration, the higher the release of
oxygen by hemoglobin. The dissociation curve levels off toward the saturation line
(100% of oxygenated hemoglobin). Almost full loading is ensured at usual oxygen
concentration (97% of oxygenated hemoglobin).
The dissociation curve exhibits 2 main features, a sigmoid shape and a left-right
position with respect to the oxygen concentration. A shift toward the left depicts
an increase in oxygen availability. The higher the carbon dioxide concentration, the
greater the right shift. Consequently, the higher the CO 2 concentration, the greater
the oxygen dissociation and delivery.

1.4 Blood Disorders

Blood disorders include: (1) blood volume loss due to bleeding after injury and
dehydration that reduces water content of the blood; (2) blood circulation dysfunc-
tioning and resulting diminished tissue perfusion caused by abnormal cardiac output
or obstacles in blood vessel lumen (thrombi and emboli); and (3) blood composition
changes that can affect the heart functioning and blood vessel caliber, hence blood
supply to the body's organs.