In Germany, about 10% of all babies are born before the 37th week of pregnancy and are therefore considered premature. Many of these premature babies need help with breathing due to their underdeveloped lungs. However, clinical practice shows that mechanical ventilation can cause irreversible damage to the lungs, although the exact causes are not yet known. In a multidisciplinary study, physicists and physicians at the University of Leipzig have now shown that increased pressure on lung tissue, due to mechanical ventilation, poses the risk of tissue stretching, even with small amounts of air, and disruption of cell function during gas exchange. .
They have just published the results of their study in the journal Frontiers in Bioengineering and Biotechnology. During normal breathing, the diaphragm descends under the lungs with each breath. This causes the lungs to expand inside the chest, creating negative pressure or a vacuum in the lungs. To compensate for this negative pressure, air automatically flows into the lungs and the person breathes. Mechanical ventilation involves pumping air into the lungs through a tube. Then the lungs expand due to this positive pressure. “We assume that this positive pressure causes a slight pressure on the lung tissue, while during normal breathing the lung is drawn in from the outside in order to induce expansion,” explains physicist Professor Marek Zink, who conducted the multidisciplinary study on early lung physics with colleague Dr. Mandy Loeb from the lab. Neonatology Research in the College of Medicine.
“In our experiments, we studied fetal lung tissue under tensile and compressive stress to explore differences in tissue mechanics in the early lung,” Mareike Zink reports. Experiments have shown that lung tissue is completely deformed under tension, as it does during normal breathing. When subjected to pressure – as with mechanical ventilation – a viscoelastic deformation of the lungs is observed. This means that although tissues return to their original state after deformation, at the molecular level, there are already structural changes that indicate irreversible tissue damage.
“Moreover, our results show that lung cell function is impaired under stress. Even low pressure, as is common in mechanical ventilation, can lead to structural units on the cell surface, which are important in transporting molecules and water, for example, no longer able to do its job,” explains Mandy Loeb.
The two scientists came to the following conclusion: for some premature babies, mechanical ventilation is the only treatment to guarantee survival. However, there is a risk of complications due to the altered mechanical properties of the early lung compared to adults. Therefore, future therapeutic strategies must take into account the effect of physical forces on tissues and cells, and limit the increase in pressure in the lungs to reduce the risk of damage. “Since it has also been observed in ventilated Covid-19 patients, that mechanical ventilation may lead to further lung damage, we hypothesize that here, too, the damaged lung can be more easily exposed to positive stress and that lung cell function stops or changes more rapidly under increasing pressure.