Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 2016
Near-infrared spectroscopy determined cerebral oxygenation with eliminated skin blood flow in young males.
We estimated cerebral oxygenation during handgrip exercise and a cognitive task using an algorithm that eliminates the influence of skin blood flow (SkBF) on the near-infrared spectroscopy (NIRS) signal. The algorithm involves a subtraction method to develop a correction factor for each subject. For twelve male volunteers (age 21 ± 1 yrs) +80 mmHg pressure was applied over the left temporal artery for 30 s by a custom-made headband cuff to calculate an individual correction factor. ⋯ With the use of both source-detector distances, handgrip exercise and a cognitive task increased O2Hb (P < 0.01) but O2Hb was reduced when SkBF became eliminated by pressure on the temporal artery for 5 s. However, when the estimation of cerebral oxygenation was based on the algorithm developed when pressure was applied to the temporal artery, estimated O2Hb was not affected by elimination of SkBF during handgrip exercise (P = 0.666) or the cognitive task (P = 0.105). These findings suggest that the algorithm with the individual correction factor allows for evaluation of changes in an accurate cerebral oxygenation without influence of extracranial blood flow by NIRS applied to the forehead.
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J Clin Monit Comput · Apr 2016
Comparative StudyComparison of foot finding methods for deriving instantaneous pulse rates from photoplethysmographic signals.
The suitability of different methods of finding the foot point of a pulse as measured using earlobe photoplethysmography during stationary conditions was investigated. Instantaneous pulse period (PP) values from PPG signals recorded from the ear in healthy volunteer subjects were compared with simultaneous ECG-derived cardiac periods (RR interval). Six methods of deriving pulse period were used, each based on a different method of finding specific landmark points on the PPG waveform. ⋯ No significant differences between PP and RR were seen for all PPG methods, however the PRV variables derived using all methods showed significant differences to HRV, attributable to the sensitivity of PRV parameters to pulse transients and artifacts. The results suggest that the intersecting tangents method shows the most promise for extracting accurate pulse rate variability data from PPG datasets. This work has applications in other areas where pulse arrival time is a key measurement including pulse wave velocity assessment.
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Respiratory rate has been shown to be an important predictor of cardiac arrest, respiratory adverse events and intensive care unit admission and has been designated a vital sign. However it is often inadequately monitored in hospitals. We test the hypothesis that RespiraSense, a piezoelectric-based novel respiratory rate (RR) monitor which measures the differential motion of the chest and abdomen during respiratory effort, is not inferior to commonly used methods of respiratory rate measurement. ⋯ The 95 % confidence interval for the difference in average RR between RespiraSense and ECG was calculated to be [-3.9, 3.1]. The 95 % confidence interval for the difference in average RR between RespiraSense and nurses' evaluation was [-5.5, 4.3]. We demonstrate a clinically relevant agreement between RR monitored by the RespiraSense device with both ECG-derived and manually observed RR in 48 post-surgical patients in a PACU environment.
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J Clin Monit Comput · Apr 2016
Assessment of the time-dependent need for stay in a high dependency unit (HDU) after major surgery by using data from an anesthesia information management system.
Admittance to a high dependency unit (HDU) is expensive. Patients who receive surgical treatment with 'low anterior resection of the rectum' (LAR) or 'abdominoperineal resection of the rectum' (APR) at our hospital are routinely treated in an HDU the first 16-24 h of the postoperative (PO) period. The aim of this study was to describe the extent of HDU-specific interventions given. ⋯ Another one-third of the patients had a need for HDU-specific therapies for more than ten consecutive hours, primarily an infusion of nor-epinephrine. Most patients treated with LAR or APR was in need of an HDU-specific intervention during the first 6 h of the PO-period, with a marked decline after this time period. The applied methodology, using an AIMS, demonstrates that there is great variability in individual patients' postoperative needs after major surgery, and that these needs are dynamic in their nature.
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J Clin Monit Comput · Apr 2016
Case ReportsEndovascular coil detachment causing EMG artefact in BIS: a mechanistic exploration.
Deployment of endovascular coils used in interventional neuroradiology commonly involves electrolytic detachment of the coil from the pusher catheter. This report describes a case of artefactual increase in electromyography (EMG) values of bispectral index (BIS) monitor during coil detachment. An explanation of this event is provided connecting mechanism of coil detachment and derivation of EMG values in a BIS monitor. While rising EMG values are thought to arise from frontalis contraction, they may as well be an unrecognized electrical artefact, especially in context of undistorted electroencephalography waveform.