Paper published in Physiological Measurement

Non-contact video-based vital sign monitoring using ambient light and auto-regressive models

It has now been established that it is possible to record the blood volume changes associated with the cardiac cycle remotely from facial images of human subjects with a digital video camera up to 2 m away from the subject, using only ambient light as the light source. This ability to record photoplethysmographic signals remotely opens up the possibility of non-contact vital sign monitoring. Conventional patient monitoring using pulse oximetry to measure heart rate and peripheral arterial oxygen saturation (SpO2) requires a probe to be attached to the patient's ear or ?nger. Long-term monitoring outside the intensive care unit is plagued by motion artefact, leading to frequent false alerts.

While non-contact monitoring will also be affected by motion artefact, the use of a camera indicates when the subject is moving, whereas conventional monitoring provides no information on the cause of the artefact. Additionally, the probes used in conventional monitoring often cause patient discomfort and increase the risk of spreading infection in hospitals. Hence a method for deriving estimates of heart rate and SpO2 with no electrodes or sensors attached to the patient is an attractive proposition, with the cost of digital video cameras continuing to decrease as the technology becomes more ubiquitous. The same non-contact monitoring technology can also be used to obtain estimates of respiratory rate, another parameter of major clinical significance (Cretikos et al 2008).

This paper advances the state-of-the-art in non-contact vital sign monitoring by making a number of significant contributions... To continue reading download your free copy of Physiological Measurement.

Physiol. Meas. 35 (2014) 807-831.