Journal of clinical monitoring and computing
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J Clin Monit Comput · Aug 2021
Heart-rate tuned comb filters for processing photoplethysmogram (PPG) signals in pulse oximetry.
Calculation of peripheral capillary oxygen saturation [Formula: see text] levels in humans is often made with a pulse oximeter, using photoplethysmography (PPG) waveforms. However, measurements of PPG waveforms are susceptible to motion noise due to subject and sensor movements. In this study, we compare two [Formula: see text]-level calculation techniques, and measure the effect of pre-filtering by a heart-rate tuned comb peak filter on their performance. ⋯ Our main conclusion is that if an uninterrupted high-quality heart rate measurement is available, then the "Red over Infrared" approach preceded by a heart-rate tuned comb filter provides the preferred trade-off between [Formula: see text]-level accuracy and computational complexity. A modest improvement in [Formula: see text] estimate accuracy at very low SNR environments may be achieved by switching to the pre-filtered DST-based algorithm (up to 6% improvement in [Formula: see text] level accuracy at -10 dB over unfiltered DST algorithm and the filtered "Red over Infrared" approach). However, this improvement comes at a significant computational cost.
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J Clin Monit Comput · Aug 2021
Non-invasive assessment of respiratory muscle activity during pressure support ventilation: accuracy of end-inspiration occlusion and least square fitting methods.
Pressure support ventilation (PSV) should be titrated considering the pressure developed by the respiratory muscles (Pmusc) to prevent under- and over-assistance. The esophageal pressure (Pes) is the clinical gold standard for Pmusc assessment, but its use is limited by alleged invasiveness and complexity. The least square fitting method and the end-inspiratory occlusion method have been proposed as non-invasive alternatives for Pmusc assessment. ⋯ Both Pmusc,lsf ≤ 4 cmH2O and Pmusc,index ≤ 1 cmH2O had excellent negative predictive value [0.98 (95% CI 0.94-1) and 0.96 (95% CI 0.91-0.99), respectively)] to identify over-assistance. The inspiratory effort during PSV could not be accurately estimated by the least square fitting or end-inspiratory occlusion method because the limits of agreement were far above the signal size. These non-invasive approaches, however, could be used to screen patients at risk for absent or minimal respiratory muscles activation to prevent the ventilator-induced diaphragmatic dysfunction.
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J Clin Monit Comput · Aug 2021
Evaluation of a new wireless technique for continuous electroencephalography monitoring in neurological intensive care patients.
A novel wireless eight-channel electroencephalography (EEG) headset specially developed for ICUs was tested in regard of comparability with standard 10/20 EEG systems. The continuous EEG (cEEG) derivations via CerebAir EEG headset (Nihon Kohden Europe, Rosbach, Germany) and internationally standardized 10/20 reference EEGs as the diagnostic standard were performed in a mixed collective on a neurointensive care unit (neuro-ICU). The derivations were verified for comparability in detection of EEG background activity, epileptiform discharges, and seizure patterns. ⋯ Overall, in 89% of the patients, cEEG detected the same or additional ICU-relevant EEG patterns. The tested wireless cEEG headset is a useful monitoring tool in patients with consciousness disorders. The present study indicates that long-term measurements with the wireless eight-channel cEEG lead to a higher seizure and epileptiform discharge detection compared to intermittent 10/20 EEG derivations in the ICU setting.
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J Clin Monit Comput · Aug 2021
A modified method of measuring plasma volume with indocyanine green: reducing the frequency of blood sampling while maintaining accuracy.
Among various methods for measuring the plasma volume (PV), the indocyanine green (ICG) dilution technique is a relatively less invasive method. However, the ICG method is rather cumbersome because 10 blood samples need to be obtained within a short time after ICG administration. Thus, reducing the frequency of blood sampling while maintaining the accuracy would facilitate plasma volume measurement in clinical situations. ⋯ Five out of the 10 blood samples (order: 1st, 2nd, 3rd, 9th, and 10th) showed similar accuracies with the plasma volume obtained by the original method (original: 2.72 ± 0.64 l, modified: 2.72 ± 0.65 l). This modified method may be able to aptly replace the original method and lead to a wider clinical application of the ICG dilution technique. Further validation is needed to determine if the results of this study may be applied in other populations.