Objectives
Upon successful completion of this guide, the learner will demonstrate knowledge by:

1. Stating normal arterial blood gas values.
2. Stating normal venous blood gas values.
3. Stating the alveolar air equation.
4. Solving problems utilizing the alveolar air equation.
5. Explaining Fick¹s Law.
6. Stating the normal value of hemoglobin for adults.
7. Defining methemoglobin, carboxyhemoglobin, and oxyhemoglobin.
8. Listing the factors affecting gas diffusion.
9. Stating the amount of oxygen one gram of hemoglobin can carry.
10. Computing oxygen content.
11. Explaining why hemoglobin is not normally 100% saturated when breathing room air.
12. Stating the normal saturation of hemoglobin in arterial and venous blood.
13. Stating normal content of oxygen in arterial and venous blood.
14. Calculating problems to solve C (a-v) O2 difference.
15. Explaining the significance of the oxygen dissociation curve.
16. Listing factors that shift the oxygen dissociation curve.
17. Explaining the significance of a shift of the oxygen dissociation curve:
    a. to the right
    b. to the left

Introduction
As a respiratory care practitioner, it will be important for you to understand the concepts of gas transport. This will enable you to:

• Assess patients¹ cardiopulmonary statuses.
• Detect abnormalities.
• Understand the significance of abnormalities.
• Develop care plans to treat the underlying abnormalities.

Included in gas transport is the understanding of gas exchange at the alveolar level. At the alveolus, oxygen (O2) crosses the alveolar-capillary (a­c) membrane to the pulmonary capillary. At the same time, carbon dioxide (CO2) crosses from the capillary to the alveolus where it is then exhaled. Abnormalities at this level may affect arterial blood gas (ABG) values for O2 and CO2. By assessing various parameters such as the PAO2, PaCO2, and the D(A­a)O2 abnormalities at the alveolar level may be detected.

As blood leaves the pulmonary circulation and is pumped by the left heart into the circulatory system, gas exchange occurs at the cellular level. It is here where tissues and organs receive oxygen and give off carbon dioxide. Abnormalities at this level may cause certain tissues or organs to be oxygen deprived. By assessing various parameters such as the CaO2 or the a­v O2 difference abnormalities at the cellular level may be detected.

Gas exchange, both at the alveolar and cellular level, is a complicated process. Many factors may affect the exchange of oxygen and carbon dioxide. This guide will discuss the intricate, but fascinating, process of gas exchange and transport.