Optimization of the oxygen transport system.

Emphasizing the over-all performance of the O(2) transport system, as well as the interactions between its various subsystems, a method for a parametric performance analysis has been developed. The purpose of such an analysis is three-fold: 1. It permits an evaluation of those parameters which are critical for the performance of the system under conditions of stress. 2. It leads to an assessment of the ranking of individual members within the hierarchy of biological control systems. 3. It permits an objective assessment of the severity and prognosis of cardiovascular and respiratory diseases and of the degree of disability resulting therefrom. Starting with the principle of conservation of mass, two equations are derived which express the balance of oxygen in terms of supply, consumption, and waste. These equations are then developed in terms of the parameters of the system; namely, ventilation, inspired O(2) concentration, cardiac output, O(2) capacity of the blood, energy requirements of the two pumps, fractional extraction of O(2) from alveolar air (ventilation-perfusion ratio), and the oxygen utilization fraction in the periphery. The results indicate that the normal system attempts to maximize the oxygen utilization fraction while minimizing ventilatory and cardiac energy requirements. Changes in the ventilation-perfusion ratio are relatively less important. Possible extensions of the model are discussed.