Journal of clinical monitoring and computing
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J Clin Monit Comput · Dec 2021
Non-invasive indirect monitoring of intra-abdominal pressure using microwave reflectometry: system design and proof-of-concept clinical trial.
Monitoring intra-abdominal pressure (IAP) has become a standard in intensive care units. Correlation between the abdominal wall's thickness (AWTh) and IAP has been reported previously. The abdominal wall can be modeled as a compound of parallel dielectric slabs; changes in their width have a direct effect on the reflection coefficient of the abdominal wall at microwave frequencies. ⋯ C95.1-2005 concerning exposure of humans to microwave electromagnetic fields in controlled environments. The results putatively show an inverse correlation between IAP and the reflection coefficient, and a strong dependence on the body mass index. A better understanding of the dynamics in the changes of the AWTh (during intra-abdominal hypertension) will allow further development of a microwave-based technique for the continuous non-invasive indirect monitoring of IAP in critical patients.
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J Clin Monit Comput · Dec 2021
Letter Case ReportsLoss of spectral alpha power during spine surgery: what could be wrong?
The electroencephalographic signatures of anesthetic drugs relate to a specific set of action mechanisms within the neural circuits. During intraoperative care, the recognition and correct interpretation of the EEG spectrogram can be used as a tool to guide anesthetic administration. For example, loss of alpha power during propofol anesthesia may be a sign of lighter level of hypnosis and/or of an increase in nociceptive inputs. We describe a case report of inadvertent interruption of propofol delivery that was first detected by changes in the electroencephalogram spectrogram.
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Awake fibreoptic intubation has always been considered the gold standard for expected difficult airway management. However, the use of fibreoptic intubation was limited because it is time-consuming, requires skillful operators and easily affected by blood or secretions in the oral or nasopharynx. We reported a modified technique of awake fibreoptic nasal intubation with the aid of End-tidal carbon dioxide (ETCO2) monitoring, aiming to improve the efficiency and safety of awake fibreoptic intubation.
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J Clin Monit Comput · Dec 2021
Artifact reduction by using alternating polarity stimulus pairs in intraoperative peripheral nerve action potential recording.
Intraoperative nerve action potential (NAP) recording permits direct study of an injured nerve for functional assessment of lesions in continuity. Stimulus artifact contamination often hampers NAP recording and interferes with its interpretation. In the present study, we evaluated the artifact reduction method using alternating polarity in peripheral nerve recording. ⋯ Finally, we applied the method during nerve inching and demonstrated its usefulness in intraoperative NAP recordings as the method made the recording more resilient to short conduction distances. Thus, our findings demonstrate that this artifact reduction method can be used as a supplemental tool together with our previously described bridge grounding technique or the nonlifting nerve recording configuration to further improve intraoperative peripheral nerve recording. The method can be applied in clinical settings.
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J Clin Monit Comput · Dec 2021
Validation of a new approach for distinguishing anesthetized from awake state in patients using directed transfer function applied to raw EEG.
We test whether a measure based on the directed transfer function (DTF) calculated from short segments of electroencephalography (EEG) time-series can be used to monitor the state of the patients also during sevoflurane anesthesia as it can for patients undergoing propofol anesthesia. We collected and analyzed 25-channel EEG from 7 patients (3 females, ages 41-56 years) undergoing surgical anesthesia with sevoflurane, and quantified the sensor space directed connectivity for every 1-s epoch using DTF. The resulting connectivity parameters were compared to corresponding parameters from our previous study (n = 8, patients anesthetized with propofol and remifentanil, but otherwise using a similar protocol). ⋯ However, the topographies were not significantly different when comparing results computed from sevoflurane and propofol data, neither in the awake nor in anesthetized state. Optimizing the algorithm for simultaneously having high sensitivity and specificity in classification yielded an accuracy of 95.1% (SE = 0.96%), with sensitivity of 98.4% (SE = 0.80%) and specificity of 94.8% (SE = 0.10%). These findings indicate that the DTF changes in a similar manner when humans undergo general anesthesia caused by two distinct anesthetic agents with different molecular mechanisms of action.