Journal of clinical monitoring and computing
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J Clin Monit Comput · Jan 2000
Bispectral index (BIS) and burst suppression: revealing a part of the BIS algorithm.
The bispectral index (BIS) is a complex EEG parameter which integrates several disparate descriptors of the EEG into a single variable. One of the subparameters incorporated in the BIS is the suppression ratio, quantifying the percentage of suppression during burst suppression pattern. The exact algorithm used to synthetize the information to the BIS value is unpublished and still unknown. This study provides insight into the integration of the suppression ratio into the BIS algorithm. ⋯ Suppression ratio values > 40% are linearly correlated with BIS values from 30 to 0. An increasing anesthetic drug effect resulting in an increase of the duration of suppression to a suppression ratio up to 40% is not adequately reflected by the BIS value.
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J Clin Monit Comput · Jan 2000
Atypical "tails-up" capnograph due to breach in the sampling tube of side-stream capnometer.
An atypical "tails-up" capnograph pattern was noticed in a patient during the use of an accidentally crushed sampling tube with a slit-like hole. We investigated the mechanics involved in the observed capnograph pattern. ⋯ During IPPV, pressure in the breathing circuit is lower during exhalation, thus allowing air to enter through the slit-like hole in the sampling tube causing erroneously low ETCO2 and expiratory sevoflurane. With inspiration, positive pressure in the breathing circuit, transmitted to the sampling tube, prevents air admixture and the upsurge in CO2 is displayed giving the capnograph an atypical "tails-up" appearance. During spontaneous breathing, since pressure in the breathing circuit barely becomes positive during exhalation and is negative during inspiration, air mixes with the sampled gas during both phases and so the capnograph shape was normal but with lower values for ETCO2, insp./exp. sevoflurane, and nitrous oxide levels. If undiagnosed, this defect in the sampling tube can lead to significant errors in the measurement of inspired and expired gas concentrations.
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To describe a new pulse oximetry technology and measurement paradigm developed by Masimo Corporation. ⋯ The technological strategies implemented in Masimo SET pulse oximetry effectively permit continuous monitoring of SpO2 during challenging clinical conditions of motion and poor tissue perfusion.
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J Clin Monit Comput · Jan 2000
Warning devices for prevention of dental injury during laryngoscopy. Preliminary report.
The prototypes of two novel warning devices for protection against dental trauma during direct laryngoscopy are described. Either can be attached to a standard laryngoscope blade (e.g., Macintosh). The basic design is that of a switch that is closed by pressure on the maxillary incisors by the laryngoscope blade.
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J Clin Monit Comput · Jan 2000
The effect of single twitch and train-of-four stimulation on twitch forces during stable neuromuscular block.
We investigated whether the response to a single twitch (ST) stimulus or the first response (T1) to a train-of-four (TOF; 4 stimuli at 2 Hz) stimulus following a stimulus interval of 10 s (i.e., the time between two consecutive ST or TOF stimuli) is influenced by the preceding stimulus in the presence of a stable 50% neuromuscular block. In addition, we determined whether ST and TOF stimulation yield different results under these circumstances. ⋯ The ST or T1 force during stimulation with a stimulus interval of 10 s or more during a stable 50% neuromuscular block in the tibialis anterior muscle of the cat is not affected by the preceding stimulus. In addition, ST and T1 forces do not differ when employing a stimulus interval of 10 s or more under these circumstances. Our results thus indicate that the known differences between ST and T1 forces after a bolus injection of a muscle relaxant can not be explained by differences in acetylcholine release when the stimulus interval exceeds 10 s.