The lungs ensure that our blood is supplied with oxygen from breathing air and that carbon dioxide is removed. "While the functioning of the lungs is well known, the vital organ itself is sort of a black box. Important values such as oxygen concentration can only be accurately measured before inhalation or in the blood. How exactly oxygen is distributed on its way through the lungs and what that means for intensive care ventilation has not yet been studied," says Prof. Rüdiger Schwarze. The expert in the field of fluid mechanics at TU Bergakademie Freiberg researches how fluids behave physically.
As part of a project funded by the German Research Foundation (DFG) from 2015 to 2020 (grant number: 257981040, total funding: 440,000 euros), the researchers have developed simplified model lungs made of transparent acrylic glass: "Thanks to the model, we can shed light on the black box and visualize the process of gas exchange from the trachea to the upper bronchial tree. In the study, we examined oxygen transport during so-called liquid ventilation," explains Dr. Katrin Bauer, research associate and author of the article in the journal Scientific Reports. With this method of ventilation, oxygen is supplied by the oxygen-containing liquid Perflourcarbon instead of directly by air. So far, this method has been used in clinical studies for acute lung failure and for a more protective ventilation of premature infants.
Via the model lungs, the researchers are able to visualize the oxygen in the model fluid using an oxygen-sensitive and fluorescent dye, allowing them to accurately analyse how oxygen is distributed from the trachea to the upper bronchi during a simulated breathing cycle. "Specifically, we measured the dissolved oxygen concentration distribution during the flow and compared it to those velocity fields known from previous work," co-author Thomas Janke explains.
Since oxygen transport in the lungs in the upper bronchial tree is dominated by convection and not diffusion – meaning that the transport of oxygen is driven by the flow – the results can in principle be transferred from liquid ventilation to ventilation with air. "With the help of the lung model, we were able to understand how exactly the transport of oxygen in the upper branches of the lungs with the supply of fresh air, as well as the removal of used, oxygen-depleted air takes place," Thomas Janke clarifies. "The higher the tidal volume, which is the volume which is breathed in and out, the faster the oxygen is distributed and the faster a higher oxygen concentration can be achieved. However, an increased breathing rate has no influence on the oxygen concentration in the lower airways. So if you breathe faster, you don't achieve a higher oxygen concentration," Dr. Katrin Bauer summarizes the results.
In order to further validate the results of the basic research conducted by the engineering scientists at TU Bergakademie Freiberg for ventilation in intensive care units, preclinical studies would have to follow in further steps. "However, we currently have not found possible partners for a cooperation," says Prof. Rüdiger Schwarze.
MEDICA-tradefair.com; source: TU Bergakademie Freiberg
