Removal of power-line interference from the ECG: a review of the subtraction procedure

BACKGROUND: Modern biomedical amplifiers have a very high common mode rejection ratio. Nevertheless, recordings are often contaminated by residual power-line interference. Traditional analogue and digital filters are known to suppress ECG components near to the power-line frequency. Different types of digital notch filters are widely used despite their inherent contradiction: tolerable signal distortion needs a narrow frequency band, which leads to ineffective filtering in cases of larger frequency deviation of the interference. Adaptive filtering introduces unacceptable transient response time, especially after steep and large QRS complexes. Other available techniques such as Fourier transform do not work in real time. The subtraction procedure is found to cope better with this problem. METHOD: The subtraction procedure was developed some two decades ago, and almost totally eliminates power-line interference from the ECG signal. This procedure does not affect the signal frequency components around the interfering frequency. Digital filtering is applied on linear segments of the signal to remove the interference components. These interference components are stored and further subtracted from the signal wherever non-linear segments are encountered. RESULTS: Modifications of the subtraction procedure have been used in thousands of ECG instruments and computer-aided systems. Other work has extended this procedure to almost all possible cases of sampling rate and interference frequency variation. Improved structure of the on-line procedure has worked successfully regardless of the multiplicity between the sampling rate and the interference frequency. Such flexibility is due to the use of specific filter modules. CONCLUSION: The subtraction procedure has largely proved advantageous over other methods for power-line interference cancellation in ECG signals

Differences in health information literacy competencies among older adults, elderly and younger citizens

Abstract To address the research gap on age-based differences in health information literacy (HIL), we investigated how younger (born 1960–) and older adults (1946–1960), and elderly citizens (–1945) differed from each other by their HIL competencies. Data were collected with an online survey of patients using the Swedish national electronic health record system. Altogether, 2,587 users responded. One-way ANOVA with post hoc tests revealed several differences between the groups: younger adults were less likely to value health information than older adults; older adults and elderly were least likely to compare information from multiple sources and had trouble in determining health information needs; older adults were most likely to have trouble understanding health terminology and the elderly to have difficulties in understanding medicinal package labels. The study shows that HIL is not necessarily improving or declining but adapting to challenges of advanced age