Journal of clinical monitoring and computing
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J Clin Monit Comput · Dec 2017
Comparative StudyComparison of pneumotachography and anemometery for flow measurement during mechanical ventilation with volatile anesthetics.
Volatile anesthetics alter the physical properties of inhaled gases, such as density and viscosity. We hypothesized that the use of these agents during mechanical ventilation would yield systematic biases in estimates of flow ([Formula: see text]) and tidal volume (V T) for two commonly used flowmeters: the pneumotachograph (PNT), which measures a differential pressure across a calibrated resistive element, and the hot-wire anemometer (HWA), which operates based on convective heat transfer from a current-carrying wire to a flowing gas. We measured [Formula: see text] during ventilation of a spring-loaded mechanical test lung, using both the PNT and HWA placed in series at the airway opening. ⋯ A simple compensation factor based on density reduced observed differences between the flowmeters, regardless of the anesthetic or concentration. These data indicate that the choice and concentration of anesthetic agents are primary factors for differences in estimated V T between the PNT and HWA. Such discrepancies may be compensated by accounting for alterations in gas density.
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J Clin Monit Comput · Dec 2017
Prediction of difficult laryngoscopy using spirometry: a pilot study.
Prediction of difficult laryngoscopy is still the uncovered secret of anesthetic practice. This pilot study is aimed to assess the efficacy of spirometry measurements in predicting difficult laryngoscopy compared with conventional airway assessment techniques. We enrolled 202 adults, ages 18-40 years, with an American Society of Anaesthesiologists score of I or II, scheduled for elective surgery and undergoing general anesthesia. ⋯ In a multivariate linear regression model, all spirometry measurements revealed that forced inspiratory vital capacity (β = -2.050, P = 0.022) was the significant predictor for difficult laryngoscopy. The area under the curve for forced inspiratory vital capacity with a cut-off value of 3.1950 L while using thyromental distance as difficult laryngoscopy indicator is 0.754 and forced inspiratory vital capacity showed a sensitivity of 0.718 and specificity of 0.714 with a positive likelihood ratio of 2.5104 and negative likelihood ratio of 0.3949. Forced inspiratory vital capacity showed a close association with the prediction of difficult laryngoscopy.
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J Clin Monit Comput · Dec 2017
Parasympathetic tone variations according to umbilical cord pH at birth: a computerized fetal heart rate variability analysis.
Non-reassuring fetal heart rate tracings reflect an imbalance between the parasympathetic and sympathetic nervous systems. In this situation, fetal asphyxia can be suspected and may be confirmed by metabolic measurements at birth like low pH or high base deficit values. The objective of this study was to determine whether fetal asphyxia during labor is related to parasympathetic nervous system activity. ⋯ FSI was measured during the last 30 min of labor before birth and compared between groups. The minimum value of the FSI during the last 30 min before delivery was significantly lower in the group with the lower umbilical cord arterial pH value. In this pilot study during labor, FSI was lower in the group of infants with low arterial pH at birth.
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J Clin Monit Comput · Dec 2017
A feasability study of color flow doppler vectorization for automated blood flow monitoring.
An ongoing issue in vascular medicine is the measure of the blood flow. Catheterization remains the gold standard measurement method, although non-invasive techniques are an area of intense research. We hereby present a computational method for real-time measurement of the blood flow from color flow Doppler data, with a focus on simplicity and monitoring instead of diagnostics. ⋯ Errors on synthetic images ranged from nonexistent to substantial depending on experimental conditions. Mean errors on measurements from our phantom flow simulation ranged from 1.2 to 40.2% for angle estimation, and from 3.2 to 25.3% for real-time flow estimation. This study is a proof of concept showing that accurate measurement can be done from automated color flow Doppler signal extraction, providing the industry the opportunity for further optimization using raw ultrasound data.
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J Clin Monit Comput · Dec 2017
Comparative StudyComparison of the qCON and qNOX indices for the assessment of unconsciousness level and noxious stimulation response during surgery.
The objective of this work is to compare the performances of two electroencephalogram based indices for detecting loss of consciousness and loss of response to nociceptive stimulation. Specifically, their behaviour after drug induction and during recovery of consciousness was pointed out. Data was recorded from 140 patients scheduled for general anaesthesia with a combination of propofol and remifentanil. ⋯ Furthermore, the qCON showed faster decrease during induction. This behaviour is associated with the hypothesis that the loss of response to stimuli (analgesic effect) might be reached after the loss of consciousness (hypnotic effect). On the contrary, the qNOX showed a faster increase at the end of the surgery, associated with the hypothesis that a higher probability of response to stimuli might be reached before the recovery of consciousness.