Assessing Pulmonary Capillary Pressure Using Pulmonary Arterial Occlusion Data: Master's Thesis

Pulmonary capillary pressure is the blood pressure in the smallest vessels of pulmonary circulation. This pressure is one major factor of pulmonary edema. Pulmonary edema is a life-threatening state, often seen in critically ill patients. Pulmonary capillary pressure should be known to avoid pulmonary edema, e.g., in connection with fluid therapy. Currently, there are no methods for directly assessing the pulmonary capillary pressure. The aim of this work is to find a method for automatic estimation of pulmonary capillary pressure and implement it using digital signal processing. In this study, the pulmonary capillary pressure is estimated from the data obtained in connection with right heart catheterization. The pulmonary capillary pressure is obtained by analyzing the pressure transient following balloon occlusion. The signal was measured from intact lungs without stopping the mechanical ventilation. The pulmonary capillary pressure was obtained by fitting a single exponential curve to the pressure decay following the balloon occlusion and by extrapolating back to the time of occlusion. The results were compared with visual estimates, individually done by three clinicians. The results show that the methods successfully used by other research groups in animal tests are not directly applicable to intact lungs and clinical practice. The computer estimates differ about 3 mmHg from the mean of visual estimates. The results are, however, so promising that future plans have been made to verify the developed methods with a new data library.