Development of a portable blood pressure device with wireless communication

Abstract

Cardiovascular diseases are the number one cause of death worldwide. Given the fact that 54% of these deaths are related with high blood pressure, its monitoring is the first step to reduce morbidity. As life quality increases, life expectancy also increases leading to population aging. The expensive treatment costs and limited health infrastructure to meet the needs of this aged population led medical devices sector to develop the so called Ambient Assisted Living (AAL) solutions. These solutions have integrated electronics that allow constant monitoring of vital parameters with the purpose of diagnosing diseases earlier and prevent emergency situations in order to improve life quality in the preferred living environment. This thesis follows the development of a portable blood pressure device with wireless communication of its readings which is included in this AAL area. A linear approximation algorithm was used to treat the data acquired using the oscillometric method. The work includes the design of schematics, a Printed Circuit Board (PCB) which integrates all the selected components for this device and a mobile and desktop interface where the readings are shown. The system was programmed using an Atmel R debugger, AVR Dragon, and Atmel R microcontroller, ATxmega 128A3, for whom all the firmware was developed in C language while the Bluetooth chip used was the RN4020 from Microchip. Some decisions such as the wireless protocol used or the battery charger adapter were made taking into account a future commercial approach. Also, several factors were studied during the hardware and firmware development so it could be optimized for reduced dimensions and power consumption. Benchtests were performed using an interface developed in Matlab R while the blood pressure readings were sent to a mobile interface developed in Android.

As doen¸cas cardiovasculares s˜ao a maior causa de morte a n´ıvel mundial. Estando a hipertens˜ao relacionada com 54% destas mortes, a monitoriza¸c˜ao da press˜ao arterial ´e o primeiro passo para reduzir o impacto destas doen¸cas. O aumento da qualidade de vida, da esperan¸ca m´edia de vida e a baixa natalidade leva a um envelhecimento da popula¸c˜ao. Este facto associado aos custos elevados de tratamento e `a falta de infrastruturas para ir ao encontro das necessidades desta popula¸c˜ao envelhecida levaram o sector dos dispositivos m´edicos a desenvolver solu¸c˜oes com electr´onica integrada que permitem a monitoriza¸c˜ao constante de parˆametros vitais. Estas solu¸c˜oes possibilitam o diagn´ostico precoce de doen¸cas e previne situa¸c˜oes de emergˆencia, melhorando a qualidade de vida. Esta disserta¸c˜ao inclui-se na ´area da Ambient Assisted Living (AAL) e detalha o desenvolvimento de um dispositivo de press˜ao arterial port´atil com comunica¸c˜ao wireless das suas leituras. O algoritmo de aproxima¸c˜ao linear foi implementado para tratar os dados adquiridos atrav´es do m´etodo oscilom´etrico. O trabalho inclui o desenho de esquem´aticos, de Printed Circuit Boards (PCB) que integram todos os componentes seleccionados para este dispositivo e o desenvolvimento de uma interface mobile e uma interface desktop com o utilizador. O sistema foi programado usando um debugger da Atmel R , o AVR Dragon, e um microcontrolador tamb´em da Atmel R , o ATxmega 128A3, para o qual todo o firmware foi desenvolvido em C, enquanto que o m´odulo de bluetooth usado foi o RN4020 da Microchip. Algumas decis˜oes como o protocolo wireless a ser usado ou a forma de carregar o dispositivo foram tomadas tendo em conta um futuro uso comercial desta solu¸c˜ao. O hardware e firmware foi tamb´em optimizado para reduzir as dimens˜oes e o consumo de energia do dispositivo. Os testes do sistema foram feitos usando uma aplica¸c˜ao desenvolvida para desktop em Matlab R , sendo a interface Android usada para mostrar os valores de press˜ao arterial lidos.