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Impedance Changes (impedance + change)
Selected AbstractsLabel-Free Impedance Biosensors: Opportunities and ChallengesELECTROANALYSIS, Issue 12 2007Jonathan Abstract Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in surface impedance when a target molecule binds to an immobilized probe. The affinity capture step leads to challenges shared by all label-free affinity biosensors; these challenges are discussed along with others unique to impedance readout. Various possible mechanisms for impedance change upon target binding are discussed. We critically summarize accomplishments of past label-free impedance biosensors and identify areas for future research. [source] Regional ventilation distribution in non-sedated spontaneously breathing newborns and adults is not differentPEDIATRIC PULMONOLOGY, Issue 9 2009Andreas Schibler MD Abstract Background: In adults, ventilation is preferentially distributed towards the dependent lung. A reversal of the adult pattern has been observed in infants using radionuclide ventilation scanning. But these results have been obtained in infants and children with lung disease. In this study we investigate whether healthy infants have a similar reverse pattern of ventilation distribution. Study Design: Measurement of regional ventilation distribution in healthy newborn infants during non-REM sleep in comparison to adults. Methods: Twenty-four healthy newborns and 13 adults were investigated with electrical impedance tomography (EIT) in supine and prone position. Regional ventilation distribution was assessed with profiles of relative impedance change. The phase lag between dependent and non-dependent ventilation was calculated as a measure of asynchronous ventilation. Results: In newborns and adults the geometric center of ventilation was centrally located in the lung at 52.2,±,6.2% from anterior to posterior and at 50.5,±,14.7%, respectively. Using impedance profiles, ventilation was equally distributed to the dependent and non-dependent lung regions in newborns. Ventilation distribution in adults was similar. Phase lag characteristics of the impedance signal showed that infants had slower emptying of the dependent lung than adults. Conclusion: The speculated reverse pattern of regional ventilation distribution in healthy infants compared to adults could not be demonstrated. Gravity had little effect on ventilation distribution in both infants and adults measured in supine and prone position. Pediatr Pulmonol. 2009; 44:851,858. © 2009 Wiley-Liss, Inc. [source] Positive end-expiratory pressure optimization using electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgeryACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2006K. Erlandsson Background:, Morbidly obese patients have an increased risk for peri-operative lung complications and develop a decrease in functional residual capacity (FRC). Electric impedance tomography (EIT) can be used for continuous, fast-response measurement of lung volume changes. This method was used to optimize positive end-expiratory pressure (PEEP) to maintain FRC. Methods:, Fifteen patients with a body mass index of 49 ± 8 kg/m2 were studied during anaesthesia for laparoscopic gastric bypass surgery. Before induction, 16 electrodes were placed around the thorax to monitor ventilation-induced impedance changes. Calibration of the electric impedance tomograph against lung volume changes was made by increasing the tidal volume in steps of 200 ml. PEEP was titrated stepwise to maintain a horizontal baseline of the EIT curve, corresponding to a stable FRC. Absolute FRC was measured with a nitrogen wash-out/wash-in technique. Cardiac output was measured with an oesophageal Doppler method. Volume expanders, 1 ± 0.5 l, were given to prevent PEEP-induced haemodynamic impairment. Results:, Impedance changes closely followed tidal volume changes (R2 > 0.95). The optimal PEEP level was 15 ± 1 cmH2O, and FRC at this PEEP level was 1706 ± 447 ml before and 2210 ± 540 ml after surgery (P < 0.01). The cardiac index increased significantly from 2.6 ± 0.5 before to 3.1 ± 0.8 l/min/m2 after surgery, and the alveolar dead space decreased. PaO2/FiO2, shunt and compliance remained unchanged. Conclusion:, EIT enables rapid assessment of lung volume changes in morbidly obese patients, and optimization of PEEP. High PEEP levels need to be used to maintain a normal FRC and to minimize shunt. Volume loading prevents circulatory depression in spite of a high PEEP level. [source] Synthetic diamond films as a platform material for label-free protein sensorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2009Nathalie Bijnens Abstract In the framework of developing a fast and label-free immunosensor for C-reactive protein (CRP) detection, H-terminated nanocrystalline diamond (NCD) was functionalised with anti-CRP antibodies that were physically adsorbed to the surface. Impedance spectroscopy was used to electronically detect real-time CRP recognition. Different impedance behaviours were observed after CRP addition as compared to after FITC-labelled ssDNA addition at low (100 Hz) as well as at high frequencies (1 MHz). Physical interpretations of the observed impedance changes were obtained by fitting the data to an equivalent electrical circuit. Concentrations of 1 ,M CRP were recognised with a reaction time of 30 minutes. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Modulation of gap junctions by nitric oxide contributes to the anti-arrhythmic effect of sodium nitroprusside?BRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2009Márton Gönczi Background and purpose:, Nitric oxide (NO) donors provide a preconditioning-like anti-arrhythmic protection in the anaesthetized dog. As NO may modulate gap junction (GJ) function, the present study investigated whether this anti-arrhythmic effect is due to a modification of GJs by NO, derived from the NO donor sodium nitroprusside (SNP). Experimental approach:, In chloralose-urethane-anaesthetized, open-chest dogs, either saline (controls; n= 11) or SNP (0.2 µg·kg,1·min,1; n= 10) was infused at a rate of 0.5 mL·min,1 by the intracoronary route. The infusions were started 20 min prior to and maintained throughout the entire 60 min occlusion period of the left anterior descending coronary artery. The severity of ischaemia and of arrhythmias, tissue electrical impedance and permeability, as well as the phosphorylation of connexin43, were assessed. Key results:, Compared with the controls, SNP infusion markedly suppressed the total number of ventricular premature beats (666 ± 202 vs. 49 ± 18; P < 0.05), and the number of ventricular tachycardiac episodes (8.1 ± 2.3 vs. 0.2 ± 0.1; P < 0.05) without significantly modifying the incidence of ventricular tachycardia or ventricular fibrillation. The severity of ischaemia (epicardial ST-segment changes, inhomogeneity of electrical activation) and tissue electrical impedance changes were significantly less in the SNP-treated dogs. SNP improved GJ permeability and preserved the phosphorylated form of connexin43. Conclusion and implications:, The anti-arrhythmic protection resulting from SNP infusion in the anaesthethized dog may, in part, be associated with the modulation of gap junctional function by NO. [source] | ||||||||||