Evolution of the Krogh Cylinder Model

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Drawings from August Krogh’s work on capillaries that illustrates the concept of perfused capillary density, the Krogh cylinder and the oxygen pressure field.

Krogh realized that capillaries spontaneously opened and closed as the need for oxygen increased or decreased. The pattern of opening and closing was not random, but occurred so that the open capillaries remained equidistant no matter how many were open. He realized that biological systems conserved energy by minimizing perfusion during times of low physiologic demand and maximizing it during periods of high demand. From this concept he was able to derive a math formula to describe how oxygen is distributed throughout the tissues during low and high demands.

Perfusion Theory is an educational platform for the Oxygen Pressure Field Theory (OPFT). August Krogh’s theoretical concept of the oxygen pressure field is explained and then applied to clinical applications in perfusion practice.