The effect of percutaneous transluminal angioplasty of superficial femoral artery on pulse wave features

We aimed to analyze the effects of percutaneous transluminal angioplasty (PTA) of the superficial femoral artery (SFA) on arterial pulse waves (PWs). Altogether 24 subjects i.e. 48 lower limbs were examined including 26 treated lower limbs having abnormal ankle-to-brachial pressure index (ABI) (ABI1.3) and 22 non-treated lower limbs. The measurements were conducted in pre-, peri- and post-treatment phases as well as in follow-up visit after 1 month. Both ABI and toe pressures measured by standard equipment were used as reference values. PW-derived parameters include ratios of different peaks of the PW and time differences between them as well as aging index. Both treated and non-treated limbs were compared in pre- and post-treatment as well as follow-up visit conditions. The results were evaluated in terms of statistical tests, Bland-Altman-plots, free-marginal multirater κ-analysis and multiple linear regression analysis. PTA was found to cause small changes to the studied PW-derived parameters of the treated limb which were observed immediately after the treatment, but the changes were more pronounced in the follow-up visit. In addition, we observed that the endovascular instrumentation itself does not cause significant changes to the PW-derived parameters. The results show that PW-analysis could be a useful tool for monitoring the treatment-effect of the PTA. However, because the pre-treatment differences of the treated and non-treated limb were small, further studies with subjects having no arterial diseases are required. The study demonstrates the potential of the PW analysis in monitoring vascular abnormalities.acceptedVersionPeer reviewe

Lower limb pulse rise time as a marker of peripheral arterial disease

Abstract Objective: The aim of the study was to show if pulse rise times (PRTs) extracted from photoplethysmographic (PPG) pulse waves (PWs) have an association with peripheral arterial disease (PAD) or its endovascular treatment, percutanoeus transluminal angioplasty (PTA) of the superficial femoral artery. Methods: Lower and upper limb PPG PWs were recorded and analyzed from 24 patients who suffered from PAD. The measurements were conducted before and after the treatment, and one month later by using transmission-mode PPG-probes placed in the index finger and second toe. Ankle-to-brachial pressure index and toe pressures were used as references in clinical patient measurements. PRTs, i.e., the time from the foot point to the peak point of the PW, were extracted from the PWs and compared bilaterally. The results from the PAD patients were also compared with 31 same-aged and 34 younger control subjects. Results: Statistically significant differences were found between the pretreatment PRTs of the treated limb of the PAD patients and the same-aged control subjects (p < 10⁻⁹, Mann–Whitney U-test). The changes in the PRT of the treated lower limb were observed immediately after the PTA (p < 0.001, Student’s t -test), and after one month (p < 0.0005), whereas the PRTs of the non-treated lower limb and upper limb did not indicate changes between different examinations. Conclusion: Results show that a PRT greater than 240 ms indicates PAD-lesions in the lower limb. Significance: This proof-of-concept study suggests that the PRT could be an effective and easy-to-use indicator for PAD and monitoring the effectiveness of its treatment

Stimulation waveform selection to suppress functional electrical stimulation artifact from surface EMG signals

We present a simple method to suppress the artifact that functional electrical stimulation causes to surface electromyography signals. The method is based on selecting a high-frequency sinusoidal wavelet as the stimulation waveform to make the artifact frequencies easily removable from the measured signals, and combining it with simple filters in the hardware and as digital filters. Our theoretical computations demonstrate how the selected stimulus pulses attenuate significantly compared to commonly used square wave pulses already in a first-order low-pass filter used before the measurement amplifier. The experimental results with 8 participants show that the artifacts can be suppressed in our target application: facial pacing for unilateral facial paralysis. The method can be beneficial also for other neuroprosthetic applications that apply functional electrical stimulation in combination with electromyography measurements. More complex artifact suppression methods are unnecessary and the delays of the processing are caused only by the simple filters in the signal processing chain.acceptedVersionPeer reviewe

Combining unobtrusive electrocardiography and ballistography for more accurate monitoring of sleep

acceptedVersionPeer reviewe

Wireless interrogation techniques for sensors utilizing inductively coupled resonance circuits

AbstractThe methods needed to interrogate passive resonance sensors are studied. A portable impedance measurement unit and the methods to extract a coupling coefficient compensated resonance frequency are presented. The interrogation methods are demonstrated with ECG and pressure measurements. The results show that the quality of the ECG signal measured with a flexible textile coil is sufficient to extract the heart rate. In the case of a pressure sensor, the errors caused by the changes in the inductive coupling were satisfactorily removed by the introduced method

Capacitive facial movement detection for human-computer interaction to click by frowning and lifting eyebrows

A capacitive facial movement detection method designed for human-computer interaction is presented. Some point-and-click interfaces use facial electromyography for clicking. The presented method provides a contactless alternative. Electrodes with no galvanic coupling to the face are used to form electric fields. Changes in the electric fields due to facial movements are detected by measuring capacitances between the electrodes. A prototype device for measuring a capacitance signal affected by frowning and lifting eyebrows was constructed. A commercial integrated circuit for capacitive touch sensors is used in the measurement. The applied movement detection algorithm uses an adaptive approach to provide operation capability in noisy and dynamic environments. Experimentation with 10 test subjects proved that under controlled circumstances the movements are detected with good efficiency, but characterizing the movements into frowns and eyebrow lifts is more problematic. Integration with a two-dimensional pointing solution and further experiments are still required.Peer reviewe