Oxygen saturation in the blood that is either too low or too high can cause physical harm or even death. This is why patients’ oxygen concentraions are monitored continuously in both intensive care and trauma units. However, the pulse oximeters clipped onto a patient’s fingertip for this purpose can be unreliable. Researchers at the Fraunhofer-Gesellschaft have developed a fluorescence-based sensor that measures the oxygen content of people’s breath directly and in real time. The sensor determines the oxygen concentration in the respiratory gas according to the principle of fluorescence quenching, which allows conclusions to be drawn about the oxygen saturation in the blood.