Higher strain caused by artificial ventilators (left) and less stretch when the same lung is made to breathe naturally. Credit: Mona Eskandari/UCR
Key Points:
- Researchers show in a new study that modern ventilators overstretch lung tissue.
- The findings provide an explanation for the decline in lung health experienced by patients the longer they spend on the machines.
- The team is now looking into how to improve ventilation strategies by emulating natural breathing.
The COVID-19 pandemic saw the highly increased use of ventilators. And while they were critical to survival rate in the early days, a new study shows they also come with unintended consequences—they overstretch lung tissue.
The study, published in the American Journal of Respiratory and Critical Care Medicine demonstrates major differences between how we naturally breathe versus how ventilators make us breathe. The results provide an explanation for the decline in lung health experienced by patients the longer they spend on the machines, especially in the case of disease.
Mona Eskandari, UC Riverside assistant professor of mechanical engineering, and colleagues pioneered a technique to study lungs as they are made to breathe. On a custom-built ventilator designed in their lab, the researchers imitated both natural and artificial breathing. Then, they observed isolated lungs involved in both types of breathing using multiple cameras collecting fast, high-resolution images, a method called digital image correlation.
“Our setup allows us to imitate both physiological and artificial breathing on the same lung with the switch of a button,” said Eskandari. “The unique combination of our ventilator with digital image correlation gives us unprecedented insights into the way specific regions of the lungs work in concert with the whole.”
Using their innovative method to interface the two systems, the researchers collected evidence demonstrating that natural breathing stretches certain parts of the lung as little as 25% while those same regions stretch to as much as 60% when on a ventilator.
Instead of the current thin-walled ventilator model that treats lungs like balloons, the researchers propose a thick-walled model that accounts for the differing levels of stress in airways, resulting from ventilators pushing air in versus natural breathing, which pulls air in. This helps to explain how airways are more engaged and air is more evenly distributed in the lung during physiological breathing.
“Now that we know about excessive strain when air is delivered to the lungs, the question for us becomes about how we can improve ventilation strategies by emulating natural breathing,” Eskandari said.
Information provided by UC Riverside.