Continuous Pulmonary Capillary Blood Flow Estimation from Measurements of Respiratory Anesthetic Gas Concentration

A noninvasive, on-line estimation scheme has been developed for continuous determination of pulmonary capillary blood flow (PCBF) and related cardiopulmonary parameters from measurements of anesthetic gas concentration based on a gas uptake and distribution model of the body and the lungs. Two moving window algorithms, one based on the well-known off-line maximum likelihood algorithm, and the other based on a frequency response technique, have been investigated for this purpose. Special consideration was given to the sensitivity to various error sources that affect each estimation algorithm. Both computer simulations and in vivo experiments demonstrate that the proposed estimation procedures can be used for on-line PCBF determination provided that the nonestimated system parameters can be measured with sufficient accuracy.