Journal of clinical monitoring and computing
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J Clin Monit Comput · Feb 2014
Randomized Controlled TrialAutomated titration of propofol and remifentanil decreases the anesthesiologist's workload during vascular or thoracic surgery: a randomized prospective study.
Closed loop target-control infusion systems using a Bispectral (BIS) signal as an input (TCI Loop) can automatically maintain intravenous anesthesia in a BIS range of 40-60 %. Our purpose was to assess to what extent such a system could decrease anesthesia workload in comparison to the use of a stand alone TCI system manually adjusted to fit the same BIS range of 40-60 % (TCI Manual). Patients scheduled for elective vascular or thoracic surgery were randomized to the TCI Loop or TCI Manual method for administering propofol and remifentanil during both induction and maintenance of general anesthesia. ⋯ Mean arterial pressure was lower with TCI Manual (78 ± 6 vs. 88 ± 13 mmHg, p < 0.001). The number of times the anesthesiologist watched the controller or BIS monitor (p < 0.05) and the number of manual adjustments (p < 0.001) performed in each group was lower with TCI Loop group during induction and maintenance of anesthesia. An automated controller strikingly frees the anesthesiologist from manual intervention to adjust drug delivery.
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J Clin Monit Comput · Feb 2014
Comparative StudyDetection of changes in muscle oxygen saturation in the human leg: a comparison of two near-infrared spectroscopy devices.
The purpose of this study was first to evaluate the near infrared spectroscopy (NIRS) device, INVOS 4100 as a method of measuring exercise and arterial occlusion induced muscle ischemia in human leg, by comparison with InSpectra tissue spectrometer Model 325, and secondly to determine the influence of skin and subcutaneous thickness on the NIRS measurements. Twenty healthy subjects (43 ± 8 years) volunteered for the study. Tissue oxygen saturation (StO2) in the anterior tibial muscle was measured simultaneously with InSpectra Model 325 in one leg and INVOS 4100 in the contralateral leg during an exercise test until muscle exhaustion and arterial occlusion with and without exercise. ⋯ There was a significant inverse correlation between skin and subcutaneous thickness and baseline StO2 (r = -0.78, p < 0.01) as well as change in StO2 during exercise (r = -0.65, p = 0.002) for InSpectra, which was not apparent for INVOS. The results demonstrate that the cerebral/somatic oxygenation monitor (INVOS) is able to detect experimentally induced skeletal muscle ischemia in the human leg as well as the peripheral tissue spectrometer (InSpectra). Muscle oxygen saturation measurement by INVOS is less affected by skin and subcutaneous thickness than measured by InSpectra.
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J Clin Monit Comput · Feb 2014
A pilot study quantifying the shape of tidal breathing waveforms using centroids in health and COPD.
During resting tidal breathing the shape of the expiratory airflow waveform differs with age and respiratory disease. While most studies quantifying these changes report time or volume specific metrics, few have concentrated on waveform shape or area parameters. The aim of this study was to derive and compare the centroid co-ordinates (the geometric centre) of inspiratory and expiratory flow-time and flow-volume waveforms collected from participants with or without COPD. ⋯ A comparison of airflow waveforms show that in COPD, the breathing rate is faster (17 ± 4 vs 14 ± 3 min(-1)) and the time to reach peak expiratory flow shorter (0.6 ± 0.2 and 1.0 ± 0.4 s). The expiratory flow-time and flow-volume centroid is left-shifted with the increasing asymmetry of the expired airflow pattern induced by airway obstruction. This study shows that the degree of skew in expiratory airflow waveforms can be quantified using centroids.
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To control the three components of general anesthesia (hypnosis, analgesia, and neuromuscular blockade), an automated closed-loop, anesthesia-drug delivery system (McSleepy) was developed. Bispectral index was used as the control variable for hypnosis, the analgoscore for analgesia, and phonomyography for neuromuscular blockade. McSleepy can be used to control the induction, maintenance and emergence from general anesthesia. ⋯ Preliminary results of 15 patients are presented in this paper. Evaluation of McSleepy was done through an assessment of its clinical performance and using Varvel's performance indices. The system was found to be clinically useful by providing good precision in drug administration and reliable results for the duration of a general anesthesia.