Mathematical Models for Simulating Physiological Responses to Severe military Stress

A previous model of the renal function and compartmented whole body, which incorporated actions of antidiuretic hormone on urine flow and composition, is extended to include the influences of additional phenomena, many exogenous to the kidney. These include the intrinsic-osmotic effect of water; details of the body's antidiuretic hormone cycle; gastrointestinal exchanges; changes in glomerular filtration caused by alternation in blood volume and pressure; and resistance to flow across kidney tubular walls. The responses of the model were validated by comparison with responses of actual subjects, as reported in the literature. The model was exposed to and responded correctly to the following stresses: water loading through ingestion; hypertonic saline infusion; hypertonic urea solution ingestion; antidiuretic hormone dysfunction, as in diabetes insipidus; controlled rehydration after dehydration; and two combined stresses — hypertonic saline solution ingestion followed by water ingestion, and the converse experiment.