Circulation-time models of the uptake of inhaled anaesthetics and data for quantifying them.

Conventional compartmental models of the uptake and distribution of inhaled anaesthetics assume that blood moves from lungs to tissues and from tissues back to lungs in zero time. Three new models which incorporate alternative representations of the finite time actually taken have been constructed in terms of Algol programs for a digital computer. It is shown that the conventional approach causes systematic errors in the computed uptake of low-solubility agents, in the arterial tension of high-solubility agents, and in the tissue tensions of all agents. The errors are important in the first minute or two of administration or recovery. The conventional distribution of blood volume between compartments is shown to be in error and to cause even greater systematic errors in computed results. Three different published distributions of tissue volume and cardiac output give different computed results and a "preferred" distribution is suggested.