‘Sigh’ all you want: It’s a superpower |
The next time someone rolls their eyes because you sighed, ignore them. Because what you have is a superpower. The deep, long breath might do more than just signal relief or frustration.A new research from ETH Zurich found that deep sighing could also be beneficial for your lungs. The findings of the study are published in the journal Science Advances.
Why deep sighs are actually good for us
More than half of all premature babies born before the 28th week of pregnancy develop respiratory distress syndrome shortly after birth. Their lungs are not fully developed, so they produce too little of the seemingly magical fluid that reduces surface tension in the lungs. This causes alveoli to collapse, resulting in the lungs struggling to get enough oxygen. Until 40 years ago, this only resulted in death. However, in the late 1980s, a life-saving procedure was developed. The pediatricians extracted the fluid from animal lungs and injected it into the lungs of premature babies. “This works very well in newborns. The fluid coats the entire surface, making the lungs more deformable or – with a more technical word – compliant, ” Jan Vermant, Professor of Soft Materials at ETH Zurich, said. Lungs can also fail in adults. Around 3,000 people in Switzerland developed acute respiratory distress syndrome during the pandemic. However, injecting the surface-active fluid from animals does not work in adults. “This shows that it’s not just about reducing surface tension. We believe that mechanical stresses within the fluid also play an important role,” Vermant states.
The study
To understand this, scientists from Spain, Belgium, and the USA, teamed up to investigate precisely how lung fluid behaves when it is stretched and recompressed in the laboratory. The fluid in our bodies is also subjected to similar movements when the lungs expand during inhalation and contract again during exhalation.“This surface stress influences how compliant the lungs are,” Vermant explains. The more compliant the lungs are, the less resistance there is to expansion and contraction, and the easier it is to breathe. The researchers found that surface stress decreases significantly after deep breaths. Yes, sighing works. There is definitely a physical explanation for why you feel a relief after a deep sigh. The explanation starts from realizing that the thin film formed by the lung fluid on the surface of the lungs actually consists of several layers.
“Directly at the boundary with the air, there is a slightly stiffer surface layer. Underneath, there are several layers that should be softer than the surface layer,” Maria Novaes-Silva, a doctoral student in Vermant’s research group and first author of the study, adds. This layering returns to equilibrium over time when the fluid is still or moves only slightly during shallow breathing.
Deep breath
The researchers found that a deep breath is needed from time to time to restore this ideal layering. They found that the pronounced stretching and compression of the pulmonary fluid causes the composition of the outer layer to change.” There is an enrichment of saturated lipids, this results in a more densely packed interface,” says Novaes-Silva. Vermant adds: “This is a state outside of the boundaries of the thermodynamic equilibrium that can only be maintained through mechanical work.”
