Wave Propagation in Pulmonary Circulation: Effect of Pulmonary Hypertension due to Sickle Cell Disease

Sickle-cell disease (SCD) is a common disorder, which affects more than two million people worldwide, with approximatively 100000 cases in the United States. One of the main complications of its progression is pulmonary hypertension (PH), a pathological condition highly related to patients’ death, characterized by mean pulmonary artery pressure (mPap) higher than 25 mm Hg at rest. The gold-standard for mPap measurement, thus for PH diagnosis, is right heart catheterization (RHC). RHC is an invasive, technically difficult, and expensive technique, which exposes patients to high risks (infection, bleeding, …). Although non-invasive techniques, such as echocardiography, have been shown to be suitable to obtain diagnostically relevant information, RHC is still mandatory to establish PH diagnosis and gaining insight into the disease progression. Computational hemodynamics models can play a fundamental role in this clinical background, which ranges from monitoring disease progression and/or response to treatment, to planning intervention and integrating experimental data for diagnostic purposes. In this work, the pulmonary circulation has been modeled as a one-dimensional branching waveguide with the purpose of simulating the pressure wave propagation and the effect of SCD and PH. A frequency-domain analytical model has been developed, based on the models proposed by Wiener et al. and Olufsen et al. . Three main parts comprise the present work: 1. A preliminary study, in which the analytical model has been compared to a finite element model; 2. A pulse wave simulation, in which a pressure pulse has been simulated via superposition of different harmonics; 3. Pulmonary hypertension simulation, in which structural and mechanical changes have been introduced in the model with the aim of simulate the effect of the pathology. In the preliminary study, the analytical model has been validated since the comparison with the finite element model showed a good agreement in the results. The pulse wave simulation shows the versatility of the approach chosen for the analytical model. In fact, the frequency-domain analytical model was able to give all pieces of information necessary to reconstruct the arterial pulse wave in the time domain. The results of the pathology simulation have shown changes in pressure distribution along the arterial tree and changes in the phase velocity, which can be relevant from a clinical perspective. The developed model turned out to be a versatile and suitable tool for different application, that can be further developed with the aim of obtaining diagnostically relevant information and a better knowledge of disease processes related to pathologies, such as pulmonary hypertension.