Physiological measurements, wearable

Riistama J. 2007. Characterisation of wearable and implantable physiological measurement devices. Automation, Mechanical and Materials Engineering. Tampere, Tampere University of Technology 76. 

The measurement of physiological parameters, or body responses (Table 8.2), is one of the most common functions for wearable sensors. Developments in this area closely follow advances in the medical and telemedicine fields. For sports, the main reason for measuring how the body is performing is to support training and, in particular, fitness development. Among the parameters highlighted in Table 8.2, most have found a way into commercial products (covered in Section 8.5), with the exception of sweat measurement and analysis. 

Capacitive sensors can be used to detect displacement from the fact that capacitance between two parallel metal plates, C = eoEt A/x, where eo = dielectric constant of free space, Cf = relative dielectric constant of media. Displacement can be measured by changing aU these three parameters. A good example is the capacitance microphone that is responding to displacement by sound pressure. Piezoelectric sensors are used to measure physiological displacement and record heart sounds. These sensors are fabricated from piezoelectric ceramics and piezoelectric polymers. For flexible wearable sensors, fiber or film form of polymer piezoelectric materials such as polyvinyli-dene fluoride (PVDF) are desirable. 

Cardiovascular diseases have become one of the leading causes of death worldwide. According to WHO reports, by 2030 more than 23 million people will die annually from cardiovascular diseases (htq> //www.who.mt/cardiovascular diseases/en/). Modem wearable sensors for patients with cardiovascular diseases are able to measure physiological parameters like ECG, heart rate, blood pressure in a real-time manner. 

A list of various wireless wearable devices is given in Table 7.4. Different wireless technologies have been used in different wearable devices. A prototype of advanced care and alert portable telemedical monitor (AMON) wrist-worn unit is shown in Fig. 7.14 [8]. The system has two major parts a wrist-wom unit and a stationary unit at the telemedicine center. The wrist-wom unit measures physiological parameters and transmits through a Global System for Mobile communication (GSM) network to the stationary unit for data collection and processing by trained medical personnel [8]. The stationary unit is composed of a JAVA server platform and a workstation connected to the GSM transceiver. 

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