New ear sensor for mobile, continuous and long term pulse oximetry

Abstract

Pulse oximetry is a valuable monitoring technology used at present mainly for immobile patients. The reason for the limitation concerning the user's mobility is due principally to unsuitable sensors and sensor locations. This is particularly the case with finger sensors, which tend to work best in respect to signal quality i.e. modulation depth, but are quite susceptible to motion artifacts. In order to achieve mobility for pulse oximetry monitoring, an ear canal sensor was developed. This area was chosen based on the assumption that intensive movement and acceleration of this part of the body is generally avoided as it produces unpleasant feelings.

Hearables: New Perspectives and Pitfalls of In-Ear Devices for Physiological Monitoring. A Scoping Review

“…In particular, working in reflection mode, in-ear devices may be affected by high shunt light (i.e., the amount of direct light traveling from the LED to the detector without propagation over the pulsing blood in the biological tissue) and to the lower signal amplitude with respect to transmission mode signals (Budidha and Kyriacou, 2014 ; Lemay et al, 2014 ; Parak, 2018 ). To improve PPG signals, optimal designing of sensor geometry and LED-photodetector distance based on the used wavelength is crucial, but also alternative sensor configurations, such as “circummission” mode have been proposed (Buschmann and Huang, 2010 ).…”

A novel wireless ring-shaped multi-site pulse oximeter

“…Studies have been performed to compare these two types of probes and optimize their design to enhance the performance of a pulse oximeter [34], [36]. However, it is known In addition to the mentioned signal acquisition modes, there is another light path which was proposed in [37], [38] that should be used in auditory canal and the expression "Circummission pulse oximetry" was suggested for it. In this method, the optoelectronic components face outside the canal and away from each other, using a semi-circle path for light to travel through the tissue.…”

“…The shunt light level is high in reflection mode and it will be decreased by using the transmission mode. Based on [37], [38], the shunt level is decreased by using the presented method in their papers. Table 1 shows a comparison between the 3 mentioned methods, [37].…”

“…Based on [37], [38], the shunt level is decreased by using the presented method in their papers. Table 1 shows a comparison between the 3 mentioned methods, [37]. As it is shown, the quality of the signal is good in circummission method but the placement of the sensor is limited to the auditory canal and it will make this method not practical for other parts of the body.…”

“…Auditory canal sensor[37]. Retinal Sensors Operation of conventional pulse oximeters is based on measuring pulsatile changes in the amount of light transmitted through a peripheral vascular bed, such as the fingertip or earlobe.…”