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Principles of Gas Exchange

The process in which oxygen and carbon dioxide enter and exit the body is explored in this section.
Oxygen Masks in Operating Room
© Photo by Anna Shvets:
Having examined the anatomical configuration of the respiratory system, breathing mechanics and lung volumes, we will now focus on gas exchange and transport.

Oxygen in the inspired air moves down the conducting airways and into the alveoli. The partial pressure gradient between the alveolus and the pulmonary capillaries is a key determinant in the rate of oxygen diffusion into the blood. 

Oxygen leaves the capillary bed almost exclusively (98%) bound to haemoglobin within the red blood cells. A smaller portion (2%) is dissolved in the plasma. As a rough guide, 100ml of blood will carry about 20ml of oxygen.

© Dr Keith Ip (Clinical Teaching Fellow), The University of Glasgow
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Introduction to Acute Respiratory Failure

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