Ultrasounds scans of Inferior Vena Cava in pneumological patients

Pulmonary diseases compromise the lungs function with an impairment of the gas exchange and an alteration of the respiratory mechanic. They are the third leading cause of death after cardiac and neoplastic ones and they have a strongly negative impact on the lifestyle and life expectancy. Inferior vena cava (IVC) ultrasonography (US) can be important in clinical practice to evaluate patients with lungs disorders because IVC reflects changes of intra-thoracic and abdominal pressure and its pulsatility is related to volume status and right atrial pressure. The measures of the diameter of the vein are used to calculate three pulsatility indices: the caval index (CI), the respiratory caval index (RCI) and the cardiac caval index (CCI). However, this estimation is not reliable due to the movements of the IVC during respiration. In order to obtain a more stable measurement of the IVC pulsatility, a new software developed by VIPER srl was employed. It allows to track the edges of the vein and consequently to obtain a reliable measure of different diameters necessary to determine the pulsatility. The aim of this study was to investigate the correlation between CI, CCI and RCI and the category of pulmonary disease in order to find differences between obstructive and restrictive pulmonary disease. For this purpose, several US scans, of both patients with lung disease and healthy subjects, were processed with the software mentioned above both in longitudinal and transversal view and a statistical analysis was conducted. A total of 29 patients was considered, 5 with an obstructive disease, 5 with a restrictive disease and 19 as control group. The median of CCI in longitudinal view was 0.12, 0.13 and 0.15 respectively for restrictive diseases, obstructive diseases and the control group. The median value of RCI was 0.1, 0.2 and 0.18 and that of CI was 0.2, 0.34 and 0.31. In transversal view the median of CCI was 0.19, 0.21 and 0.16 15 respectively for restrictive diseases, obstructive diseases and the control group. The median value of RCI 0.18, 0.31 and 0.17 and that of CI was 0.37, 0.51 and 0.34. Wilcoxon rank sum test was conducted in order to evaluate the presence of statistically significant differences between the three classes: no difference was found. Moreover, a lumped-parameters model of the cardiovascular system was implemented in MATLAB to better understand the influence of the different variables on the value of the most important pressures and volumes, both in physiological and pathological conditions. It is an innovative model based on the integration of different systems of ordinary differential equations that were found in literature; moreover, a description of the IVC was included. The model comprises two closed loops to describe the systemic and the pulmonary circulations and a time-varying elastance simulating the four cardiac chambers with their valves. Model’s parameters were chosen to replicate both physiological conditions and the investigated pathologies. It can be used also to simulate heart failure and pulmonary hypertension that can be present in patients with advanced pulmonary diseases.