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Sensor measures oxygen content of breath

Sensor measures oxygen content of breath

Technology News |
By Wisse Hettinga



Oxygen saturation in the blood that is either too low or too high can cause lasting physical harm or even death. This is why patients’ oxygen concentrations are monitored continuously in both intensive care and trauma units

Researchers at the Fraunhofer Institute for Physical Measurement Techniques IPM have developed a fluorescence-based sensor that measures the oxygen content of people’s breath directly and in real time in an effort to provide accurate figures in the future. The sensor determines the O2 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.

The human body requires adequate oxygen concentration to function properly. A healthy body regulates blood oxygen concentrations via the respiratory system. If a patient’s values are too low or too high, it means something has gone wrong with their breathing. This makes reliable measurements of blood oxygen concentrations especially crucial in caring for patients with respiratory problems who are receiving artificial respiration. At present, the most common method of determining hypoxia — when oxygen levels are too low — is a non-invasive one known as pulse oximetry. A small device called a pulse oximeter is clipped to the patient’s finger to display the O2 concentration in the blood. The issue is that the measurements are not accurate. The only way to get more reliable values is to take a sample of arterial blood and then perform a blood gas analysis, which is an unpleasant and sometimes even painful procedure for the patient. Fraunhofer IPM in Freiburg has developed a noninvasive sensor in an effort to enable painless and yet ultra-accurate measurements in the future. Attached to a breathing mask or ventilator tube, it will surpass the current state of technological advancement in terms of accuracy and cost-effectiveness, replacing existing measurement systems.

“Our sensor measures the oxygen content in people’s breath, which allows us to extrapolate to the blood oxygen concentration,” says Mahmoud El-Safoury, project manager at Fraunhofer IPM. “We use the quenching effect for the O2 sensor we developed.” In this method, a fluorescent coating deposited on an aluminum substrate is exposed to short-wave light, which causes the layer to glow. The light emitted is longer in wavelength than the light that is “exciting” the fluorescent substance, which means it is lower in energy. Then, when oxygen molecules come into contact with the coating, the fluorescent light is markedly diminished. The weaker the light, the higher the oxygen concentration. “Our measuring method is so fast and precise that we can measure oxygen concentrations down to the level of individual breaths,” El-Safoury explains.

 

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