Physiological measurement
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Physiological measurement · Dec 2013
Performance of the Sellick maneuver significantly improves when residents and trained nurses use a visually interactive guidance device in simulation.
We examined the proper performance of the Sellick maneuver, a maneuver used to reduce the risk of aspiration of stomach contents during induction of general anesthesia, using a novel device that measures and visualizes the force applied to the cricoid cartilage using thin-film force sensitive resistors in a form suitable for in vivo use. Performance was tested in three stages with twenty anaesthesiology residents and twenty trained operating room nurses. Firstly, subjects applied force to the cricoid cartilage as was customary to them. ⋯ Overall, the Sellick maneuver was often not applied properly, with large variance between individual subjects. Performance and inter-subject consistency improved to a very highly significant degree when subjects were able to use the device as a visual guide (p < 0.001). Subsequent significant improvements in performances during the last, unguided test demonstrated that the device initiated learning.
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Physiological measurement · Nov 2013
Temperature multiscale entropy analysis: a promising marker for early prediction of mortality in septic patients.
A few studies estimating temperature complexity have found decreased Shannon entropy, during severe stress. In this study, we measured both Shannon and Tsallis entropy of temperature signals in a cohort of critically ill patients and compared these measures with the sequential organ failure assessment (SOFA) score, in terms of intensive care unit (ICU) mortality. Skin temperature was recorded in 21 mechanically ventilated patients, who developed sepsis and septic shock during the first 24 h of an ICU-acquired infection. ⋯ Both entropies exhibited similar prognostic accuracy. Combination of SOFA and entropy presented improved the outcome of univariate models. We suggest that reduced wavelet Shannon and Tsallis entropies of temperature signals may complement SOFA in mortality prediction, during the first 24 h of an ICU-acquired infection.
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Physiological measurement · Oct 2013
Quantification of ventilation distribution in regional lung injury by electrical impedance tomography and xenon computed tomography.
Validation studies of electrical impedance tomography (EIT) based assessment of regional ventilation under pathological conditions are required to prove that EIT can reliably quantify heterogeneous ventilation distribution with sufficient accuracy. The objective of our study was to validate EIT measurements of regional ventilation through a comparison with xenon-multidetector-row computed tomography (XeCT) in an animal model of sub-lobar lung injury. Nine anesthetized mechanically ventilated supine pigs were examined before and after the induction of lung injury in two adjacent sub-lobar segments of the right lung by saline lavage or endotoxin instillation. ⋯ EIT was inferior to clearly separate the exact anatomical location of the regional injuries. Regional ventilation was overestimated (<2%) in the most ventral and dorsal regions and underestimated (2%) in the middle regions by EIT compared to XeCT. This study shows that EIT is able to reliably discern even small ventilation changes on sub-lobar level.
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Physiological measurement · Oct 2013
Ventilation and cardiac related impedance changes in children undergoing corrective open heart surgery.
Electrical impedance tomography (EIT) can determine ventilation and perfusion relationship. Most of the data obtained so far originates from experimental settings and in healthy subjects. The aim of this study was to demonstrate that EIT measures the perioperative changes in pulmonary blood flow after repair of a ventricular septum defect in children with haemodynamic relevant septal defects undergoing open heart surgery. ⋯ We observed a trend towards increased normΔZV in all lung regions, a significantly decreased normΔZQ in the global and anterior, but not the posterior lung region. The normΔZV/normΔZQ was significantly increased in the global and anterior lung region. Our study qualitatively validates our previously published modified EIT filtration technique in the clinical setting of young children with significant left-to-right shunt undergoing corrective open heart surgery, where perioperative assessment of the ventilation perfusion relation is of high clinical relevance.
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Physiological measurement · Sep 2013
The dynamics of carbon dioxide equilibration after alterations in the respiratory rate.
Manual or automated control of mechanical ventilation can be realized as an open or closed-loop system for which the regulation of the ventilation parameters ideally is tuned to the dynamics and equilibration time of the biological system. We investigated the dynamic, transient state and equilibration time (teq) of the CO2 partial pressure (PCO2) after changes in the respiratory rate (RR). ⋯ Extrapolation of the transition between two PCO2 steady-states allowed for the prediction of the new PCO2 steady-state as early as 0.5 teq with an error <4 mmHg. At bedside or in automated ventilation systems, the linear dependencies between ΔRR and ΔPCO2 and between ΔRR and teq as well as early steady-state prediction of PCO2 could be used as a guidance towards a timing and step size regulation of RR that is well adapted to the biological system.