New research suggests that more careful selection of patients could help improve the success rate of valves implanted into the lungs of people with emphysema.

The valves aim to improve breathing, allowing patients with the chronic lung disease to be more active and to perhaps survive longer. Previous research into the valves has been mixed, but the new Dutch study found that they work more effectively if physicians are more selective about which patients get them.

“The results are relatively impressive,” said lung physician Dr Gary Hunninghake, an assistant professor at Harvard Medical School in Boston. “These are benefits that physicians would want to get, and patients might feel better. This could result in people being more enthusiastic about this technique.”

However, the valves come with a risk of serious side effects, the study authors noted, and the treatment appears to be expensive. It’s also not clear whether the valves actually extend lives.