Diagnosing Early Stages of Brain Disorders by Listening to the Sound of Light

  • By NTU College of Engineering
  • Posted 2 years ago
  • Reading Time : a few minutes

Photoacoustic Oxygen SaTuration sensor (POSTs)

Patients who suffer from stroke, shock and other brain diseases can benefit in the near future from POSTs (Photoacoustic Oxygen SaTuration sensor) – a new invention by researchers from EEE. Led by Professor Zheng Yuanjin, this breakthrough could help doctors diagnose brain disorders in their early stages for better treatment outcomes.

In hospital ERs, OTs and ICUs, it is a matter of life to rapidly and accurately detect the patient who is suffering from shock, and to speedily institute treatment to save their lives. Shock is a state where there is a reduced delivery of blood and oxygen to the tissues to meet metabolic needs. There are typical clinical features of shock, such as fast heart rates, low blood pressures, altered mental status and reduced urine output, but many patients may not exhibit these features. There are also biochemical measures of shock, but they only begin to be raised later in the disease process.

Haemoglobin oxygen saturation of blood in the central veins (SvO2), however, begins to fall early in shock even when blood pressures appear normal. In patients with shock, the SvO2 become lower than normal (< 65%), reflecting a poor delivery of blood to oxygen-starved tissues. On the other hand, abnormally high levels of SvO2 reflect a reduced ability of the tissues to metabolise oxygen. Thus, SvO2 is an invaluable parameter for shock diagnosing.

Conventionally, SvO2 can only be measured invasively using catheters in the right superior vena cava or in the jugular vein. The insertions of such catheters are by themselves risky, and only performed in select patients. As a result, measurements of these values using catheters cannot be performed on patients who are not suitable.

POSTs is a novel iPhone sized sensor that can detect SvO2 accurately in a noninvasive manner. Prof. Zheng explained that POSTs works by shining light of different colours on the patient’s neck and then ‘listening to’ the resultant sound generated by the blood in the central vein to infer the SvO2. “The result is very accurate (~ 2%) since oxygenated and deoxygenated haemoglobin show distinct signatures in absorbing different colours of light and the generated sound waves could be accurately localised (< 1 mm) with high signal to noise ratio. The measurement process is real time and the device is portable, making it suitable for continuous monitoring,” he added.

The results demonstrate that POSTs has great potential in non-invasive SvO2 measurement and could be used in the ICUs in the near future for early detection of shock, which reduces the onus of doctors and the pain of patients.

POSTs is an iPhone sized Photoacoustic Oxygen SaTuration sensor that can measure the haemoglobin oxygen saturation of blood in the central veins (SvO2) non-invasively. This breakthrough could help doctors to diagnose brain disorders in their early stages for better treatment outcomes.

Reproduced with permission from College of Engineering (www.coe.ntu.edu.sg) and School of Electrical and Electronic Engineering (www.eee.ntu.edu.sg), Nanyang Technological University.