Simulation Software Assesses Lung Treatment Method

Computer simulation assesses the flow of 280 milliliters of medication through an adult’s lung. Bubbles represent the medication, red areas have received a high dosage while blue areas represent areas that received low dosage. Image courtesy of James Grotberg, U-M Engineering.

Researchers from the University of Michigan (U-M) have created CFD simulation software to assess the flow of medication through human lungs. The purpose is to assess and compare the treatment of acute respiratory distress syndrome (ARDS) in adults and infants.

ARDS is a condition that reduces the ability of the lungs to inflate and often affects people suffering from sepsis, an infection which causes inflammations over the whole body.

Called surfactant replacement therapy, the procedure spreads medicinal fluid throughout the lungs, allowing them to inflate. Previously, it was not known why the treatment for ARDS was successful in premature infants, but ineffective in treating the 74,000 adults that die of the illness each year in the US.

Simplifying the Simulation Can Save More Lives

The U-M team was able to fully understand and optimize the procedure using simulations. However, they found that a fully detailed simulation, though useful in research, isn’t practical in the life or death world of hospitals.

"We created this model to be simple, so that it can provide results quickly without the need for specialized equipment," said Cheng-Feng Tai who coded the model. "A physician could run it on a standard desktop PC to create a customized simulation for a critically ill patient in about an hour."

Tai explained that a full 3D model of the lung would require days to solve using a typical computer’s processing power. To assess the fluid dynamics on a typical computer, Tai needed to simplify the CFD analysis. This way doctors can assess patients in time to make a difference in their treatment.

Professor James Grotberg, teaching biomedical engineering and surgery, noted that the simulation can also be used to create targeted medication treatments as well as project how animal research can be better projected onto humans.

Without Simulation Conflicting Studies and Unknowns Halt Treatments

Computer simulation assesses the flow of 70 milliliters of medication through an adult’s lung. Bubbles represent the medication, red areas have received a high dosage while blue areas represent areas that received low dosage. Image courtesy of James Grotberg, U-M.

"The medication needs to work its way from the trachea to tiny air sacs deep inside the lungs to be effective," said Grotberg. "This therapy is relatively straightforward in babies, but more complex in adults, mostly because adult lungs are much bigger."

However, the size differential between adults and infants wasn’t the only complication in assessing the treatment.

Three studies looking into surfactant replacement therapy reported conflicting results. In 1997 a study saw a reduction of mortality rate of 40 to 20 percent. However studies in 2004 and 2011 found the treatment had no effect on mortality.

"Everyone walked away from this therapy after the 2011 study failed," lamented Grotberg. "Adult surfactant replacement therapy has been a great disappointment and puzzlement to the community ever since. But now, we think we've discovered why the later studies didn't improve mortality."

Simulation Brings Light to Medical Treatment Blackbox

The confusion as to how the medications affected people differently based on age as well as the differences between the studies was tested in a 3D model of a human lung. The researchers soon found that concentrations of medication played a big role.

"The medication used in the 1997 study delivered the same dose of medication as the later studies, but it was dissolved in up to four times more liquid," explained Grotberg. "The computer simulations showed that this additional liquid helped the medication reach the tiny air sacs in the lungs. So a possible route for success is to go back to the larger volumes used in the successful 1997 study."

Simulation shows that using 70mL of liquid (top video) reached a lot less areas of the lung than when using 280 mL of liquid (bottom video).

In addition to volume, the simulation also determined that the viscosity and flow rate of the liquid, as well as the patient’s position and lung size, also played a role in the treatment. Since surfactants can be produced with varying viscosities and diluted into various volumes doctors can use the simulation to optimize the treatment for a given patient. All that is required is a 3D image of the patient’s lungs.

This medical story only proves that simulations can bring light to unknown processes allowing for informed decisions during the optimization process. Many abandoned this research after 2011 before the technology was truly understood. The Simulation engineers at U-M proved that what doctors thought was a dead-end, was actually only a local minimum.