Journal of clinical monitoring and computing
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J Clin Monit Comput · Feb 2018
Comparative StudyIn vivo investigation of ear canal pulse oximetry during hypothermia.
Pulse oximeters rely on the technique of photoplethysmography (PPG) to estimate arterial oxygen saturation (SpO[Formula: see text]). In conditions of poor peripheral perfusion such as hypotension, hypothermia, and vasoconstriction, the PPG signals detected are often weak and noisy, or in some cases unobtainable. Hence, pulse oximeters produce erroneous SpO[Formula: see text] readings in these circumstances. ⋯ The SpO[Formula: see text]s estimated from the finger sensor have dropped below 90% in five volunteers (failure) by the end of the cold exposure. The ear canal sensor, on the other hand, had only failed in one volunteer. These results strongly suggest that the ear canal may be used as a suitable alternative site for monitoring PPGs and arterial blood oxygen saturation at times were peripheral perfusion is compromised.
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J Clin Monit Comput · Feb 2018
Assessing nitrous oxide effect using electroencephalographically-based depth of anesthesia measures cortical state and cortical input.
Existing electroencephalography (EEG) based depth of anesthesia monitors cannot reliably track sedative or anesthetic states during n-methyl-D-aspartate (NMDA) receptor antagonist based anesthesia with ketamine or nitrous oxide (N2O). Here, a physiologically-motivated depth of anesthesia monitoring algorithm based on autoregressive-moving-average (ARMA) modeling and derivative measures of interest, Cortical State (CS) and Cortical Input (CI), is retrospectively applied in an exploratory manner to the NMDA receptor antagonist N2O, an adjuvant anesthetic gas used in clinical practice. Composite Cortical State (CCS) and Composite Cortical State distance (CCSd), two new modifications of CS, along with CS and CI were evaluated on electroencephalographic (EEG) data of healthy control individuals undergoing N2O inhalation up to equilibrated peak gas concentrations of 20, 40 or 60% N2O/O2. ⋯ These results indicate that, contrary to previous depth of anesthesia monitoring measures, the CS, CCS, and especially CCSd measures derived from frontal EEG are potentially useful for differentiating gas concentration and responsiveness levels in people under N2O. On the other hand, determining the utility of CI in this regard will require larger sample sizes and potentially higher gas concentrations. Future work will assess the sensitivity of CS-based and CI measures to other anesthetics and their utility in a clinical environment.
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J Clin Monit Comput · Feb 2018
Influences of environmental noise level and respiration rate on the accuracy of acoustic respiration rate monitoring.
We tested the hypothesis that the environmental noise generated by a forced-air warming system reduces the monitoring accuracy of acoustic respiration rate (RRa). Noise levels were adjusted to 45-55, 56-65, 66-75, and 76-85 dB. Healthy participants breathed at set respiration rates (RRset) of 6, 12, and 30/min. ⋯ The RRa of one, nine, and nine participants at 76-85 dB noise agreed with RRset of 6, 12, and 30/min, respectively, which was significantly less than the other noise levels (P < 0.05). Overall, 72.9% of alarm displays highlighted incorrect values of RRa. In a noisy situation involving the operation of a forced-air warming system, the acoustic respiration monitoring should be used carefully especially in patients with a low respiration rate.
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J Clin Monit Comput · Feb 2018
Observational StudyThe effect of mouth prop on endotracheal tube intracuff pressure in children during dental rehabilitation under general anaesthesia.
Although the endotracheal tube (ETT) cuff may be associated with tracheal morbidity, cuffed tubes may reduce the aspiration risk in oral procedures. Dentists must use a mouth prop to facilitate oral visualization and to protect the oral soft tissues during dental rehabilitation under general anaesthesia (DRGA). The aim of this study was to evaluate the effect of mouth prop on endotracheal tube intracuff pressure in children during DRGA. ⋯ No significant differences were observed between the duration of the procedure and intracuff pressure or postoperative complications (P > 0.05). Cough, sore throat and nausea were observed in 4, 1 and 5 patients, respectively. Because a mouth prop may increase the intracuff pressure of ETT, strict measurement and readjustment of cuff pressures should be employed when used in children during DRGA.
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J Clin Monit Comput · Feb 2018
Observational StudyInvestigation of optical neuro-monitoring technique for detection of maintenance and emergence states during general anesthesia.
The American Society of Anesthesiologist recommends peripheral physiological monitoring during general anesthesia, which offers no information regarding the effects of anesthetics on the brain. Since no "gold standard" method exists for this evaluation, such a technique is needed to ensure patient comfort, procedure quality and safety. In this study we investigated functional near infrared spectroscopy (fNIRS) as possible monitor of anesthetic effects on the prefrontal cortex. ⋯ We observed that during maintenance the signal is relatively more stable than during emergence. Maintenance and emergence states were classified with 94.7% accuracy with a non-linear model using the locally derived mean total hemoglobin, standard deviation of HbO2, minimum and range of HbO2 and HHb as features. These features were found to be correlated with the effects of sevoflurane and to carry information that allows real time and automatic classification of the anesthetized state with high accuracy.