ESA astronaut Tim Peake and NASA astronaut Tim Kopra participated in the Airway Monitoring experiment in the Quest airlock this week.
Tim Peake posted this photo on his social media, commenting: "In the airlock at low pressure (517mmHg) to investigate airway inflammation."
Read more about this experiment in the blog: http://blogs.esa.int/tim-peake/2016/02/24/breathe/
More about the Principia mission: http://www.esa.int/Principia