Sensing vital signs without touch

A method to monitor a person’s vital signs without direct contact with their skin is reported in a paper published online this week as part of the first content in the new journal, Nature Electronics. The technique has the potential to monitor numerous people simultaneously and could provide a cost-effective and unobtrusive approach to monitoring patients in care facilities.

Measuring the vital signs of a patient is important when managing their care, but current approaches typically require direct skin contact, which can be uncomfortable for patients and can restrict their motion.

Xiaonan Hui and Edwin Kan have developed a method that directly modulates the external and internal mechanical motion of a person onto radio-frequency signals. The technique, which is termed near-field coherent sensing, uses radio-frequency identification (RFID) tags integrated with embroidered antennas, which are placed close to the skin, such as in a shirt pocket or a wrist cuff. The phase of the electromagnetic signal is sensitive to the distance between the radio-frequency source and the receiver, and can be used to evaluate external chest movement. The amplitude of the signal is not as sensitive to such variation and can be used to sense movement inside the body.

The researchers show that the technique can be used to monitor heart rate, blood pressure, respiration rate and breathing effort.