Capillary perfusion refers to the flow of blood through the smallest blood vessels, the capillaries, enabling the exchange of oxygen, nutrients, and waste between blood and tissues. It is crucial for maintaining tissue viability and function, as inadequate perfusion can lead to cellular hypoxia and organ dysfunction. Impaired capillary perfusion is a key factor in conditions such as septic shock, where microcirculatory failure contributes to tissue damage despite normal or elevated systemic blood flow.