Medical & biological engineering & computing
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Med Biol Eng Comput · Feb 2013
Clinical TrialDeformation and pressure propagation in deep tissue during mechanical painful pressure stimulation.
Manual palpation or pressure stimulation is often used for pain sensitivity assessment. The aim of the current study was to define a method for investigating the relation between pressure pain sensitivity and pressure propagation in soft or harder muscles. Three-dimensional finite-element computer-models were developed to simulate the tissue stress and strain distribution during pressure stimulation on the tibialis anterior and gastrocnemius muscles. ⋯ Average pressure pain thresholds were significantly lower for the tibialis anterior compared with the gastrocnemius muscle (319 vs. 432 kPa) These data show different pressure propagation profiles in soft and hard muscle at the same pressure pain sensation level. This new approach is relevant as the clinical routine assesses all muscles equally. This results in a different exposure to pressure in relation to the muscle evaluated which may affect the outcome of the examination.
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A method for deriving respiration from the pulse photoplethysmographic (PPG) signal is presented. This method is based on the pulse width variability (PWV), and it exploits the respiratory information present in the pulse wave velocity and dispersion. It allows to estimate respiration signal from only a pulse oximeter which is a cheap and comfortable sensor. ⋯ For comparison purposes, we have also obtained a respiratory rate estimation from other known methods which involve ECG, BP, or also PPG signals. In addition, we have also combined respiratory information derived from different methods which involve only PPG signal, obtaining a respiratory rate error of -0.17 ± 6.67% (-2.16 ± 12.69 mHz). The presented methods, PWV and combination of PPG derived respiration methods, avoid the need of ECG to derive respiration without degradation of the obtained estimates, so it is possible to have reliable respiration rate estimates from just the PPG signal.