Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 2014
Reliable real-time calculation of heart-rate complexity in critically ill patients using multiple noisy waveform sources.
Heart-rate complexity (HRC) has been proposed as a new vital sign for critical care medicine. The purpose of this research was to develop a reliable method for determining HRC continuously in real time in critically ill patients using multiple waveform channels that also compensates for noisy and unreliable data. Using simultaneously acquired electrocardiogram (Leads I, II, V) and arterial blood pressure waveforms sampled at 360 Hz from 250 patients (over 375 h of patient data), we evaluated a new data fusion framework for computing HRC in real time. ⋯ Furthermore, the fusion of waveform sources produced better error density distributions than those derived from individual waveforms. The data fusion framework was shown to provide in real-time a reliable continuously streamed HRC value, derived from multiple waveforms in the presence of noise and artifacts. This approach will be validated and tested for assessment of HRC in critically ill patients.
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J Clin Monit Comput · Apr 2014
Comparative StudyPeripheral tissue oximetry: comparing three commercial near-infrared spectroscopy oximeters on the forearm.
Estimation of regional tissue oxygenation (rStO2) by near infrared spectroscopy enables non-invasive end-organ oxygen balance monitoring and could be a valuable tool in intensive care. However, the diverse absolute values and dynamics of different devices, and overall poor repeatability of measurements are a problem. The aim of the present study is to test the hypothesis that INVOS 5100C, FORE-SIGHT and NONIN EQUANOX 7600 have similar properties concerning absolute values, repeatability, and sensitivity to changes in rStO2. ⋯ Two measures of signal-to-noise were similar among devices. This suggests that good repeatability comes at the expense of low sensitivity to changes in oxygenation. Values of rStO2 on the forearm from INVOS, NONIN and FORE-SIGTH cannot be used interchangeably.
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J Clin Monit Comput · Apr 2014
Comparative StudyElevated preoperative blood pressure predicts the intraoperative loss of SSEP neuromonitoring signals during spinal surgery.
Intraoperative neuromonitoring of somatosensory evoked potentials (SSEPs) can allow identification of evolving neurologic deficit. However, SSEP deterioration is not always associated with postoperative deficit. Transient physiologic changes, including a decrease in blood pressure (BP), can result in signal deterioration, defined as a decrease in waveform amplitude of[50 %seen without neurologic deficit. ⋯ While the presence of preoperative elevated BP predicts SSEP abnormality (p = 0.0039), a diagnosis of hypertension does not. Elevated BP, not a hypertension diagnosis, is associated with intraoperative loss of SSEP signals. This effect of elevated BP on SSEPs may be due to the larger associated intraoperative BP decline.
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J Clin Monit Comput · Apr 2014
Controlled Clinical TrialEnd-tidal versus manually-controlled low-flow anaesthesia.
During low-flow manually-controlled anaesthesia (MCA) the anaesthetist needs constantly adjust end-tidal oxygen (EtO2) and anaesthetic concentrations (EtAA) to assure an adequate and safe anaesthesia. Recently introduced anaesthetic machines can automatically maintain those variables at target values, avoiding the burden on the anaesthetist. End-tidal-controlled anaesthesia (EtCA) and MCA provided by the same anaesthetic machine under the same fresh gas flow were compared. ⋯ In MCA patients the number of manual adjustments to stabilize EtAA and EtO2 were 137 and 107, respectively; no adjustment was required in EtCA. Low-flow anaesthesia delivered with an anaesthetic machine able to automatically control EtAA and EtO2 provided the same clinical stability and avoided the continuous manual adjustment of delivered sevoflurane and oxygen concentrations. Hence, the anaesthetist could dedicate more time to the patient and operating room activities.
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J Clin Monit Comput · Apr 2014
Letter Case ReportsAn abrupt reduction in end-tidal carbon-dioxide during neurosurgery is not always due to venous air embolism: a capnograph artefact.
Venous air embolism (VAE) is a well recognized complication during neurosurgery. Pre-cordial doppler and trans-esophageal echocardiography are sensitive monitors for the detection of VAE. A sudden, abrupt reduction in the end-tidal carbondioxide (ETCO2) pressure with associated hypotension during neurosurgery might suggest VAE, when more sensitive monitors are not available. We describe an unusual cause for sudden reduction in ETCO2 during neurosurgery and discuss the mechanism for such presentation.