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The duration of a sit-to-stand (SiSt) transfer is a representative measure of a person's status of physical mobility. This paper measured the duration unobtrusively and automatically using a pressure sensor array under a bed mattress and a floor plate beside the bed. Pressure sequences were extracted from frames of sensor data measuring bed and floor pressure over time. The start time was determined by an algorithm based on the motion of the center of pressure (COP) on the mattress toward the front edge of the bed. The end time was determined by modeling the foot pressure exerted on the floor in the wavelet domain as the step response of a third-order transfer function. As expected, young and old healthy adults generated shorter SiSt durations of around 2.31 and 2.88 s, respectively, whereas post-hip fracture and post-stroke adults produced longer SiSt durations of around 3.32 and 5.00 s. The unobtrusive nature of pressure sensing techniques used in this paper provides valuable information that can be used for the ongoing monitoring of patients within extended-care facilities or within the smart home environment.

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Homes could be equipped with unobtrusive pressure sensors to monitor older adults. This paper deals with the processing, analysis and communication of pressure sensor outputs that would enable such monitoring. An example is shown of an adult of 63 years who slept over top of a pressure sensor array. Her nocturnal respiratory rate was monitored via the pressure sensor array. Additionally, her bed time, rise time, and out-of-bed times were accurately recorded using the methods proposed herein. This information was presented through a secure web interface, which would allow a caregiver simple and intuitive access to client data.