Sampling and Condensation of Exhaled Breath Air for the Monitoring of Viral Load and Lung Diseases

The pandemic of 2020 caused by the coronavirus Sars-CoV-2 involves problems with the respiratory system and has already caused 2 million deaths worldwide. Respiratory diseases are the third leading cause of death in the world. Lung cancer is the cancer with the highest incidence of death and it is widespread among adults and children. For a successful treatment of lung diseases, it is essential to early diagnose them and follow the patient constantly during the disease progress, however, current diagnostic tools are invasive and lack accuracy and reproducibility. A promising method to diagnose and monitor pulmonary diseases is the Exhaled Breath Condensate (EBC) analysis, which allows to trace exhaled Volatile Organic Compounds (VOCs) considered as biomarkers of those pathologies. The EBC analysis method has lots of positive aspects: it is totally non-invasive, it is easy to perform with patients of all ages and with every respiratory disease, independently of their severity, and it is useful for serial longitudinal and epidemiological studies. Unfortunately, it is not yet widely used in clinical practice due to a lack of agreement on the biomarkers profiles for each disease, related to large uncertainties and a lack of standardization and validation of breath samples collection. Low concentrations of the different biomarkers make this kind of analysis a metrological challenge. Due to the nature of the EBC method, the aerosols and droplets in expired breath are collected and with this liquid also the total viral material expired. This characteristic is important not only for the diagnosis of viral diseases but also for the understanding of the spreading risks associated to expired breath of subjects carrying Sars-Cov-2 and others virus. Thus, the purpose of this thesis is to model a EBC sampler to diagnose lung diseases, using Aspen HYSYS and ANSYS Fluent. Validation of the model was performed against literature data. After the simulations, we focus our attention on how much condensate volume is obtained from a volume of exhaled air in Fluent and Aspen and on the composition of the exhaled breath condensate in Aspen. In particular, the ammonia concentration in exhaled air and in the EBC was analysed through sensitivity analyses. To compare the literature reference value of ammonia molarity in the condensate and the condensate volume with the results obtained from the simulations, an estimation of the uncertainty following the GUM (Guide for the Expression of the Uncertainty in Measurement) was performed. The Computational Fluid Dynamics (CFD) simulation in Fluent was used to evaluate the air condensation in the chosen geometry and the heat exchange areas. From these analyses, it emerges that the condensate volume is in line with the values found in the literature. The concentration of ammonia in the EBC was highly dependent on the model used, although it could be validated since the available data had an already large variability.