ESTIMATION OF PULMONARY DIFFUSION RESISTANCE AND SHUNT IN AN OXYGEN STATUS MODEL

A compartment model of the transport of oxygen from the alveoli to the tissues is described. In patients with both pulmonary shunt and alveo lar resistance to diffusion of oxygen, the model is used to simulate t heir response to variations in the inspired oxygen fraction. These sim ulation results are compared to the responses from a patient with resp iratory malfunction, indicating that the method can identify patients where not only a pulmonary shunt but also a high alveolar resistance t o diffusion of oxygen is clinically significant. Estimation of pulmona ry shunt and oxygen diffusion resistance can be done in two different implementations of the model. In the first implementation the estimate s are generated by numerical solution of the equations of the compartm ent model. In the second implementation the equations have been used t o construct a causal probabilistic net where biological uncertainties and uncertainties in the measurements can be represented.