Simulation study for noninvasive measurement of mean systemic transit time

The total body blood volume can be calculated by the product of mean systemic transit time (t) and cardiac output. This study has developed the mathematical procedures that, based on feedback analysis of linear time invariant systems for extracting mean systemic transit time from [18]O[2] and inert gas profiles, determined the accuracy of the mean systemic transit time calculating algorithms under simulated conditions which model pulmonary states from normal to severely abnormal. These states are used to test the hypothesis that the mean [18]O[2] systemic transit time can be determined to within 15% with model simulating patients have lungs with ventilation-perfusion ratio distributions in nonuniformity from normal to severely nonuniform [as in patients with severe chronic obstructive pulmonary disease (COPD)]. Literature ventilation-perfusion ration distribution data for normal, restrictive lung disease (RLD), and COPD subjects (from Wagner) have been used in the simulation study. The reliability of this measurement has been tested when different types of random noise have been added into the measured signals.