Computer program ‘stretches’ lungs to mimic emphysema


Emphysema is a long-term and devastating lung disease. As it progresses, the body’s own inflammatory enzymes slowly digest and destroy the alveoli, the delicate sacs where oxygen from the air is transferred to the bloodstream.

The damaged alveoli form large holes in the lung tissue that impairs gas exchange in the rest of the organ, resulting in shortness of breath, wheezing, chronic coughing, and eventually death.

By observing the disease through the eyes of engineers, researchers have better understood its course. A new study, published in Computational Biology PLOS, suggests how mechanical forces operating on a microscopic scale could help predict survival and quality of life for patients after treatment.

“In the future, you should be able to optimize treatment for a specific patient,” says Béla Suki, professor of biomedical engineering at Boston University. “Very few computer studies have been able to address quality of life.”

Emphysema has no cure, and for many years the last resort treatment for the disease was invasive surgery called lung volume reduction, in which a surgeon opens a patient’s chest and removes diseased parts. and inflamed lungs. The surgery gives the remaining healthy lung tissue room to expand and allows the patient to breathe. But the procedure only works in some people, and the effects vary widely from patient to patient.

Oxygen doesn’t benefit everyone with COPD

In recent years, surgeons have started using a less invasive treatment called bronchoscopic lung volume reduction (bLVR). In this outpatient procedure, a bronchoscope is inserted into a patient’s diseased lung and releases a sealant, or, alternatively, a coil spring, which collapses the diseased tissue, filling in the spaces and giving the remaining healthy lung tissue space. to expand.

Interest in these treatments has increased recently, as the results of clinical trials such as REVOLENS, published in JAMA in 2016, showed significant improvement for some patients six months after surgery. But no research has explained why the procedures work better in some patients than others.

“Even if you stop smoking, emphysema continues to progress, but at a slower rate.”

“There has been a lot of research, clinical trials. But not a lot of investigations into what’s going on on a microscopic scale, ”says Jarred Mondoñedo, medical school candidate at the medical school and lead author of the Computational Biology PLOS to study. “That’s where the direction of this research comes from. We said, “Let’s really see what’s going on. “

Simple computer program

The new research builds on results previously published by Suki, who studied the elastic properties of healthy and diseased lung tissue by stretching samples in the lab. One of Suki’s students discovered, by accident, that the emphysematous tissue ruptured under surprisingly low tension. This led Suki to further study the mechanical forces at work as emphysema progresses.

“Even if you stop smoking, the emphysema continues to progress, albeit at a slower rate,” says Suki. “The reason is that when something ruptures in the lung, the tension that this element carries is going to be distributed. The other elements will start to take a bit more force, so they have a higher risk of failure. And it’s making a gradual comeback.

2 chronic lung diseases share genetic changes

To better understand this process, the researchers built a simple computer program, called an elastic spring network model, to mimic lungs with emphysema.

“It’s not a super complicated model,” says Mondoñedo, who says it represents the connections and tensions between sections of lung tissue as hexagons of interconnected springs. “We can go through and ‘break’ the springs, and we get a new setup that represents the progression of emphysema,” he says.

Mondoñedo and Suki executed the computer model in different ways, allowing the emphysema to progress and then ‘step in’ with various treatments, such as surgery, at different times, then allow the model to progress further and quantify. the results.

“In the computer, you can play God,” says Suki. “We just do the surgery on the computer, then we let it evolve, and now it’s easy for us to compare the speed at which things are happening. “

They measured a factor called “compliance,” which quantifies the elasticity of lung tissue. “And you could say that, well, if the compliance hits this or that value, basically the lung is so destroyed that the person dies. And then we can predict how long it would take, with or without intervention, and also what your lung function is, how easy it is to breathe.

Their computer model suggests that bLVR works as well or better than traditional lung volume reduction surgery, and also suggests a mechanism – the distribution of force and its relationship to lung structure – that explains, for the first time, why this is the case. It also confirms previous findings that the procedures work best for patients who are affected only in specific parts of their lungs, rather than evenly throughout lung tissue.

Scientists express hope that their model can one day help doctors and patients decide which procedure will work best for each individual.

“If you could do a CT scan of a patient and then integrate that data into our network model, you could develop a strategy based on that particular patient, rather than one size fits all,” Mondoñedo explains. “That way I think it could translate into clinics and improve care. “

Source: Boston University


Gordon K. Morehouse