Ventilation:The process by which air moves into and out of the lungs, enabling gas exchange with the blood.
Perfusion:The passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, usually referring to the delivery of blood to a capillary bed in tissue.
Gas exchange: The biological process through which gases (mainly oxygen and carbon dioxide) move passively by diffusion across a surface, typically between the alveolar air and blood in the lungs