Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 2022
Observational StudyVelocity-pressure loops can estimate intrinsic and pharmacologically induced changes in cardiac afterload during non-cardiac surgery. An observational study.
Continuous measurement of aortic pressure and aortic flow velocity signals in the operating theatre allows us to draw velocity-pressure (Vel-Pre) loops. The global afterload angle (GALA), derived from the Vel-Pre loops, has been linked to cardiac afterload indicators. As age is the major determinant of constitutive arterial stiffness, we aimed to describe (1) the evolution of the GALA according to age in a large cohort of anesthetized patients and (2) GALA variations induced by haemodynamic interventions. ⋯ In non-cardiac surgery, the GALA seems to be associated with both intrinsic rigidity (reflected by age) and pharmacologically induced vasoconstriction changes (by vasopressors). In addition, the GALA can discriminate the differential effects of phenylephrine and noradrenaline. These results should be confirmed in a prospective, ideally randomized, trial.
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The operation of the BIS monitor remains undescribed, despite 20 years of clinical use and 3000 academic articles. The core algorithmic software (the BIS Engine) can be retrieved from the motherboard of the A-2000 monitor in binary form through forensic disassembly using debugging interfaces left in place by the original designers, opening the possibility of executing the BIS algorithms on contemporary computers through emulation. Three steps were required for emulation. ⋯ Additive white noise in the EEG caused a progressive lifting and flattening of BIS values. Emulation replicates BIS Engine behavior, allowing calculation upon existing EEG datasets or signals from other, potentially remote or wireless, devices. Emulation provides advantages for elucidating the mathematical expression of the algorithms, which remain important as practical constraints on any hypothetical mechanism of action of anesthetics.
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J Clin Monit Comput · Apr 2022
Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT).
Electrical impedance tomography (EIT) is used in lung physiology monitoring. There is evidence that EIT is linearly associated with global tidal volume (VT) in clinically healthy patients where no positive end-expiratory pressure (PEEP) is applied. This linearity has not been challenged by altering lung conditions. ⋯ The variance in VTEIT was best described by peak inspiratory pressure (PIP) and PEEP (adjusted R2 0.82) while variance in VTSpiro was best described by PIP and airway deadspace (adjusted R2 0.76). The relationship between VTEIT and VTSpiro remains linear with changes in tidal volume, and stable across altered lung conditions. This may have application for monitoring and assessment in vivo.
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J Clin Monit Comput · Apr 2022
Pupillary unrest, opioid intensity, and the impact of environmental stimulation on respiratory depression.
Opioid-induced respiratory depression (OIRD) confers significant morbidity, but its onset can be challenging to recognize. Pain or stimulation effects of conversation may mask or attenuate common clinical manifestations of OIRD. We asked whether pupillary unrest could provide an objective signal of opioid exposure, and whether this signal would be independent from the confounding influence of extrinsic stimulation. ⋯ PUAL is a consistent indicator of opioid effect, and distinguishes higher opioid concentrations independently of the stimulating effects of conversational interaction. Under equivalent opioid exposure, conversational interaction delayed the onset and minimized the severity of OIRD. Clinical trial registration: NCT04301895.
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J Clin Monit Comput · Apr 2022
LetterUse of flexible video bronchoscope for verification of nasogastric tube position in the intubated patient.
We propose a novel method for verifying the nasogastric tube (NGT) position and tip localization using flexible video bronchoscopy in anesthetized and intubated adult patients. The length of the scope used is 65 cm and can thus, track the NGT up to the pyloric canal. We have used this technique in patients with success. ⋯ The stomach is identified by the red mucosa and random tortuous folds (Fig. 1b). The pyloric canal can be identified by the convergence of gastric mucosal folds leading to the pyloric opening (Fig. 1c). In each case, the subdiaphragmatic position of NGT was verified with radiography, which is a routine practice in our institute.