Ms. Davila and a handful of medical students from Central University of Venezuela organized in 2014 to respond to earlier anti-government demonstrations, where they saw the need for additional volunteers on top of the local ambulance corps.

“A group of friends decided that they wanted to help,” Ms. Davila said. “What better way than just do what we know to do and practice every day?”

She said that the group’s cross was a nod to the well-known symbol for first aid, but that members had chosen “Green” for a name to differentiate themselves from the International Red Cross.

They are organized and methodical when they arrive at each protest, Ms. Davila said, setting up several “zones” where they can assess people in need of care.

“We walk with the protesters accompanying them, we walk all together in one line,” Ms. Davila said. “Each leader of the group has a flag, and we wave it so people can see where we are if they need medical attention.”