Doctors could soon use low-cost cameras to check a patient’s pulse, respiration and blood pressure thanks to scientists in the US.
Software developed at the Massachusetts Institute of Technology (MIT) can measure a person’s heart rate using video from a webcam or a mobile phone, accurate to within three beats per minute.
The non-invasive technique could be particularly useful when physical sensors would be difficult or uncomfortable, such as for burns victims or newborn babies.
It could also allow doctors to conduct initial screening tests or monitor their patients over the internet. A camera could even be built into a bathroom mirror for people who need to check their vital signs on a regular basis.
The system measures slight variations in skin brightness as blood flows through the face to calculate the pulse, according to its inventor, MIT graduate student Ming-Zher Poh.
‘Different skin tones might yield a different baseline level of brightness, but the pulse information is contained within the phasic information,’ he told The Engineer.
The technique has been used before but Poh’s work allows the use of low-resolution cameras to monitor people in ambient lighting and when they are moving. It can also measure heart rates of up to three people at once.
Public-domain software was used to identify and track the position of the face in the image, allowing the digital information to be broken down into separate red, green and blue portions of the video.
Poh then adapted signal-processing techniques originally developed to identify single voices from noisy recordings in order to extract the pulse signal from the ’noise’ of other variations caused by ambient light and movement.
He now hopes to further develop the technique to measure breathing, blood oxygen levels and blood pressure. ‘Heart rate and breathing rate are closely coupled, so information on respiration is also contained within the intensity fluctuations,’ said Poh.
Conventional blood oxygen sensors already work using optical detection, so he will adapt these to ambient lighting. Poh said he couldn’t yet comment on how he would measure blood pressure.
The project won third place and a prize of $50,000 in June in the second annual Primary Healthcare competition run by the Center for Integration of Medicine and Innovative Technology (CIMIT).
Several companies have expressed interest in the system and it could be available within five years, according to Poh. ‘This research is still at an early stage and we’re still working to improve on robustness as well as add to its capabilities,’ he said.