Guardian is a medical alert system in the form of a wearable device that monitors rapid shifts in blood pressure and acceleration to automatically detect when a user has fallen. When a fall is detected, the device will connect to a mobile device to call for emergency help. The focus of the design project is to develop the blood pressure subsystem, which is what differentiates Guardian from existing alert systems for seniors. This subsystem is comprised of two pulse plethysmography units that connect with an ATMega1284P microcontroller to continuously measure user blood pressure based on pulse wave transit time. The microcontroller measures the pulse wave transit time between the two pulse plethysmographs and applies an experimentally-derived regression model to calculate blood pressure. Rapid shifts in pressure indicate shifts in body orientation, suggesting the user has fallen. The goal of this project is to develop this optical blood pressure monitoring system and to see if it is a plausible addition to existing wearable medical alert systems.
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