Development of a vital signs monitoring ear probe.

[摘要] ENGLISH ABSTRACT: The need exists for a mobile and unobtrusive way to continuously monitor vital signs in everyday life. Wearable devices are rapidly advancing in terms of technology,functionality,andsize,with more real-time applications becoming available everyday. This thesis investigates the external ear as a novel locationfor a wearable device. The ear allows for the monitoring of multiple vital signs from one location, making the device an ideal mobile solution for non-clinical applications, without compromising the quality of life of the wearer.An application example is the monitoring off infants at home for sudden infant death syndrome risk factors. The main purpose of the device is to measure vital signs ,including core temperature ,heart rate, respiratory rate and blood oxygen saturation (SpO2). The device transmits collected data through a wireless connection to a computer for analyses and storage.A proof of concept, called the Ear-monitor, was designed and built. It consists of a silicone ear probe with embedded sensors connected to aheadband containing a micro controller, battery, and Bluetooth modem. A trialwas conducted in which the Ear-Monitor was tested on a group of 16 participants. Measurements were compared to benchmark measurements recorded by commercially available devices.The following results were obtained :core temperature was measured with a mean error of 0.02 ± 0:52 °C through an infrared sensor pointed at the tympanicmembrane. Heart rate was determined through an infrared photoplethysmogrammeasured from the ear canal wall. A beat detection algorithm identifiesheart beats and heart rate was calculated with a mean error of 0.03 ± 0.72 beats per minute. Respiratory rate was determined through analysing respiratory sinus arrhythmia. The respiratory rate was measured with a mean error of-0.56 ±1.41 breathsperminute. Finally,SpO2 was measured through pulse oximetry conducted against the ear canal wall. The different absorptionspectra of oxygenated and deoxygenated blood were used to calculate the percentage oxygen saturation of blood in peripheral blood vessels with a meanerror of-0.22 ±1.50%.All measurements showed statistically significant correlation with the irrespective benchmark measurements (p<0.05), except for SpO2.The latter isdue to the absence of measurable SpO2 variations in healthy individuals during the trial. It is concluded that the external ear is a suitable location for measuring core temperature, heart rate, and respiratory rate. Further testing is needed to evaluate the SpO2 measurement capabilities of the device. This thesis produced valuable insights into the feasibility of measuring multiplevitalsigns through the external ear and lays the foundation towards a commercial version of the Ear-Monitor.

[发布机构] Stellenbosch University