Diffusion of Gas

–       Diffusion of a gas occurs when there is a net movement of molecules from an area in which that particular gas exerts a high partial pressure to an area in which it exerts a lower partial pressure.

Fick’s Laws of Diffusion

–       Fick’s laws of diffusion describe diffusion and were derived by Adolf Fick in 1856. They can be used to solve for the diffusion coefficient, D. Fick’s first law can be used to derive his second law which in turn is identical to the diffusion equation.

Kinetic Theory of Gases

–       The kinetic theory of gases describes a gas as a large number of submicroscopic particles (atoms or molecules), all of which are in constant, rapid, random motion. The randomness arises from the particles’ many collisions with each other and with the walls of the container.

Perfusion-limited Gas Exchange

–       Perfusion-limited Gas Exchange describes the scenario in which the rate at which gas is transported away from functioning alveoli and into tissues is principally limited by the rate of blood flow through the pulmonary capillaries and thus across the alveolar membrane.

Diffusion-limited Gas Exchange

–       Because the rate of CO diffusion across the membrane is the principal factor limiting further blood transport of carbon monoxide away from the lungs, pulmonary exchange of carbon monoxide is referred to as “Diffusion-limited”.

Diffusing Capacity

–       Diffusing capacity of the lung measures the transfer of gas from air in the lung, to the red blood cells in lung blood vessels. It is part of a comprehensive series of pulmonary function tests to determine the overall ability of the lung to transport gas into and out of the blood.

Dead Space

–       Dead space is the volume of air that is inhaled that does not take part in the gas exchange, because it either remains in the conducting airways or reaches alveoli that are not perfused or poorly perfused. In other words, not all the air in each breath is available for the exchange of oxygen and carbon dioxide.

Alveoli Wall

–       Each alveolus is cup-shaped with very thin walls. It’s surrounded by networks of blood vessels called capillaries that also have thin walls. The oxygen you breathe in diffuses through the alveoli and the capillaries into the blood.