Alison Burdett

Assessment of the feasibility of an ultra-low power, wireless digital patch for the continuous ambulatory monitoring of vital signs

Background and objectives Vital signs are usually recorded at 4–8u2005h intervals in hospital patients, and deterioration between measurements can have serious consequences. The primary study objective was to assess agreement between a new ultra-low power, wireless and wearable surveillance system for continuous ambulatory monitoring of vital signs and a widely used clinical vital signs monitor. The secondary objective was to examine the systems ability to automatically identify and reject invalid physiological data. Setting Single hospital centre. Participants Heart and respiratory rate were recorded over 2u2005h in 20 patients undergoing elective surgery and a second group of 41 patients with comorbid conditions, in the general ward. Outcome measures Primary outcome measures were limits of agreement and bias. The secondary outcome measure was proportion of data rejected. Results The digital patch provided reliable heart rate values in the majority of patients (about 80%) with normal sinus rhythm, and in the presence of abnormal ECG recordings (excluding aperiodic arrhythmias such as atrial fibrillation). The mean difference between systems was less than ±1u2005bpm in all patient groups studied. Although respiratory data were more frequently rejected as invalid because of the high sensitivity of impedance pneumography to motion artefacts, valid rates were reported for 50% of recordings with a mean difference of less than ±1u2005brpm compared with the bedside monitor. Correlation between systems was statistically significant (p<0.0001) for heart and respiratory rate, apart from respiratory rate in patients with atrial fibrillation (p=0.02). Conclusions Overall agreement between digital patch and clinical monitor was satisfactory, as was the efficacy of the system for automatic rejection of invalid data. Wireless monitoring technologies, such as the one tested, may offer clinical value when implemented as part of wider hospital systems that integrate and support existing clinical protocols and workflows.

Frequency analysis of wireless accelerometer and EMG sensors data: Towards discrimination of normal and asymmetric walking pattern

This preliminary study reports on the combined use of wireless accelerometers and wireless EMG sensors for monitoring walking patterns. The sensor data was analyzed in frequency domain through FFT, PSD and time-frequency spectrogram analysis. Accelerometer spectra was found to shift towards lower frequencies (<;3 Hz) while EMG spectra of selected muscles shifted towards higher frequencies (>;50 Hz) during asymmetric walking. Median frequency was used to quantify the spectral shifts. The combined wireless accelerometer/EMG system showed potential for discrimination between the normal and asymmetric walking.

INSIGHTS IN LOG-DOMAIN FILTERING

This chapter has elaborated several issues related to log-domain filters beginning with a discussion of the design philosophy behind the various log-domain synthesis techniques. In contrast to more conventional approaches, the increased mathematical complexity associated with the log-domain technique, and stemming from the exploitation of the large-signal device characteristic, was underlined. The effect of important BJT parasitics (e.g. finite current gain, base and emitter resistances) upon both the transfer functions and the output distortion levels was next addressed, while the impact upon linearity when realizing finite transmission zeros by means of floating capacitors was also explained. The effect of input signal modulation index upon the bandwidth of (nonlinear) currents internal to a log-domain topology was elaborated. The chapter concluded with the intriguing properties of noise in log-domain.

Health-care electronics: the market, the challenges, the progress

Exploding health care demands and costs of aging and stressed populations necessitate the use of more in-home monitoring and personalized health care. Electronics hold great promise to improve the quality and reduce the cost of health care. The speakers in this hot topic session will discuss the field of health care electronics from all aspects. First, the market of health care electronics is described, and realities, trends and hypes will be pointed out. The second presentation describes the engineering challenges in ultra low-power disposable electronics for wireless body sensor applications. Both the sensor aspects, the related signal processing, and business models will be discussed. The third presentation talks about embedded bio-stimulation applications in cochlea implants, thereby highlighting the design challenges in terms of power consumption and extreme reliability of these devices. The final presentation discusses the application of brain stimulation and recording with respect to artifact reduction and field steering, and describes aspects of the modeling and design strategy. In this way, this hot-topic session offers the attendees a complete picture of the field of health-care electronics, ranging from the business to the technological and design aspects.

Analog Amplifiers Architectures: Gain Bandwidth Trade-Offs

This chapter has attempted to explore the relationship between open-loop topology and closed-loop bandwidth of analog amplifiers, and to highlight the similarities between early ideal amplifier concepts and many of today’s “new” ideas relating to the comparative merits of current-mode and voltage-mode processing. The early theories of Tellegen and Carlin make no distinction between current-mode and voltage-mode, and the division that exists today is due in part to the widespread dominance of the voltage op-amp. The popularity of this device means that concepts such as the fixed gain-bandwidth product are often assumed to be a general property of all amplifier architectures, when in fact Table 7.4 shows this to be the exception rather than the rule. The implementation of voltage amplifiers using current-mode techniques has resulted in circuits with bandwidth independent of gain, and this is often given as evidence of the superiority of current-mode processing. Table 7.4, however, shows that the bandwidth of a circuit is determined by the chosen implementation, and that certain current-mode circuits exhibit fixed gain-bandwidth products while other circuits based on voltage op-amps achieve a maximum bandwidth for all values of gain.