Gas Exchange & Transport
Start with the big picture
Alveolar oxygen and carbon dioxide partial pressures establish gradients that drive diffusion. Fick’s law relates transfer to surface area and pressure difference, and inversely to membrane thickness; exchange may be limited by diffusion or perfusion. Oxygen transport involves hemoglobin binding, whose affinity changes with conditions such as pH, carbon dioxide, temperature, and 2,3-BPG. The Bohr and Haldane effects describe linked changes in oxygen unloading and carbon dioxide carriage. Carbon dioxide travels mainly as bicarbonate, while the alveolar gas equation, A–a gradient, and V/Q relationships help organize the assessment of gas exchange. The topic also introduces dyshemoglobinemias, pulse oximetry limitations, and the distinction between oxygen saturation and oxygen content.
What you'll learn
- Explain how alveolar partial-pressure gradients drive oxygen and carbon dioxide diffusion.
- Describe how Fick’s law and perfusion influence gas exchange.
- Relate hemoglobin affinity shifts and the Bohr and Haldane effects to gas transport.
- Summarize carbon dioxide carriage and the roles of the alveolar gas equation and A–a gradient.
- Recognize how V/Q relationships and dyshemoglobinemias affect interpretation of oxygenation.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
