Li Yuxian, assistant researcher at the laboratory, said she has been studying with Wu for more than a decade since she joined his team in 2011.

Between 2012 and 2013, she joined an international project in which a hyperbaric chamber simulated conditions at 5,000 meters above sea level, allowing researchers to better study the function of the hearts and lungs.

Despite being in his 70s, Wu was the project leader and helped solve the problems researchers encountered during the experiment.

"His dedication to altitude sickness research really touched me," Li said.

Wu said dealing with a lack of oxygen has become normal.

"The plateau is part of my life. It is the root of my life and my science. I feel no regret for having chosen to stay here," he said. "I am old. My responsibility now is to lead the team and train tomorrow's doctors to ensure the health of people on the plateau gets better and better."