The Physics of Premature Lung: Why Mechan

They have just published the results of their study in the journal Frontiers in Bioengineering and Biotechnology. With normal breathing, the diaphragm descends below the lungs with each breath. This causes the lungs to expand in the chest, creating a negative pressure, or vacuum, in the lungs. To compensate for this negative pressure, air automatically flows into the lungs and the person breathes in. In mechanical ventilation, air is pumped into the lungs through a tube. The lungs then expand due to this excess pressure. “We assume that this overpressure causes a slight compression of the lung tissue, while during normal breathing the lungs are ‘pulled’ from the outside to create the expansion,” explains physicist Professor Mareike Zink, who carried out the interdisciplinary study Physics of Premature Lung together with her colleague Dr. Mandy Laube from the Neonatology Research Laboratory at the Faculty of Medicine.

“In our experiments, we examined fetal lung tissue under tensile and compressive stress in order to investigate differences in tissue mechanics in the premature lung,” reports Mareike Zink. The experiments showed that the lung tissue deforms completely elastically under tension, as occurs during normal breathing. However, when pressure is applied – as with mechanical ventilation – a viscoelastic deformation of the lungs was observed. This means that although the tissue returns to its original state after deformation, there are already structural changes at the molecular level that indicate irreversible tissue damage.

“Furthermore, our results show that the function of the lung cells is impaired under pressure. Even negative pressure, as is common with mechanical ventilation, can lead to structural units on the cell surface, which are important for the transport of molecules and water, for example, no longer being able to fulfill their function,” explains Mandy Laube.

The two scientists draw the following conclusion: For some premature babies, mechanical ventilation is the only treatment that will ensure survival. However, there is a risk of complications due to the altered mechanical properties of preterm infants compared to adults. Future therapeutic strategies should therefore consider the influence of physical forces on tissues and cells and limit increases in pressure in the lungs to minimize the risk of damage. “Since it has also been observed in ventilated Covid-19 patients that mechanical ventilation can lead to further lung damage, we postulate that the damaged lung can also be overstretched more easily by the overpressure and the lung cell function is suspended or changes more quickly under increased pressure ‘ summarizes Mareike Zink.

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