Non-invasive Online Research Articles

Online monitoring of fermentation processes via non-invasive low-field NMR.

For the development of biotechnological processes in academia as well as in industry new techniques are required which enable online monitoring for process characterization and control. Nuclear magnetic resonance (NMR) spectroscopy is a promising analytical tool, which has already found broad applications in offline process analysis. The use of online monitoring, however, is oftentimes constrained by high complexity of custom-made NMR bioreactors and considerable costs for high-field NMR instruments (>US$200,000). Therefore, low-field (1) H NMR was investigated in this study in a bypass system for real-time observation of fermentation processes. The new technique was validated with two microbial systems. For the yeast Hansenula polymorpha glycerol consumption could accurately be assessed in spite of the presence of high amounts of complex constituents in the medium. During cultivation of the fungal strain Ustilago maydis, which is accompanied by the formation of several by-products, the concentrations of glucose, itaconic acid, and the relative amount of glycolipids could be quantified. While low-field spectra are characterized by reduced spectral resolution compared to high-field NMR, the compact design combined with the high temporal resolution (15 s-8 min) of spectra acquisition allowed online monitoring of the respective processes. Both applications clearly demonstrate that the investigated technique is well suited for reaction monitoring in opaque media while at the same time it is highly robust and chemically specific. It can thus be concluded that low-field NMR spectroscopy has a great potential for non-invasive online monitoring of biotechnological processes at the research and practical industrial scales.

Two-photon imaging of intact living plants during freezing with a flexible multiphoton tomograph

We describe the combination of a flexible multiphoton tomograph (MPTflex) with a heating and cooling stage. The stage allows temperature control in the range of (−196 °C) (77 K) to +600 °C (873 K) with selectable heating/freezing rates between 0.01 K min−1 and 150 K min−1. To illustrate the imaging capabilities of the combined system, fluorescence intensity and lifetime of intrinsic molecules from a plant leaf were imaged with submicron resolution during freezing in vivo without detaching the leaf from the plant. An increase of fluorescence intensity and decay times with decreasing temperature was observed. The measurements illustrate the usefulness of multiphoton imaging as a non-invasive online tool to investigate temperature-induced effects. The flexible multiphoton tomograph with its adjustable mechano-optical arm and scan head allows imaging at otherwise hardly accessible sample regions.

CEREBRAL AND SOMATIC OXYGEN SATURATION IN PEDIATRIC CARDIAC PATIENTS WITH DELAYED STERNAL CLOSURE

Near-infrared spectroscopy offers non-invasive online monitoring of tissue oxygenation in a wide range of clinical scenarios.

Noninvasive online biomass detector system for cultivation in shake flasks

A novel online sensor system for noninvasive and continuous monitoring of cell growth in shake flasks is described. The measurement principle is based on turbidity measurement by detecting 180°‐scattered light and correlation to OD by nonlinear calibration models. The sensor system was integrated into a commercial shaking tablar to read out turbidity from below the shake flasks bottom. The system was evaluated with two model microorganisms, Escherichia coli K12 as prokaryotic and Saccharomyces cerevisiae as eukaryotic model. The sensor allowed an accurate monitoring of turbidity and correlation with OD600 ≤ 30. The determination of online OD showed relative errors of about 7.5% for E. coli K12 and 12% for S. cerevisiae. This matches the errors of the laborious offline OD and thus facilitates to overcome the drawbacks of the classical method as risk of contamination and decreasing volumes through sampling. One major challenge was to ensure a defined, nonvarying measurement zone as the rotating suspension in the shake flask forms a liquid sickle which circulates round the flasks inner bottom wall. The resulting alteration of liquid height above the sensor could be compensated by integration of an acceleration sensor into the tablar to synchronize the sensor triggering.

L-alpha-glycerylphosphorylcholine reduces the microcirculatory dysfunction and nicotinamide adenine dinucleotide phosphate-oxidase type 4 induction after partial hepatic ischemia in rats

BackgroundWe set out to investigate the microcirculatory consequences of hepatic ischemia–reperfusion (IR) injury and the effects of L-alpha-glycerylphosphorylcholine (GPC), a deacylated phospholipid derivative, on postischemic hepatocellular damage, with special emphasis on the expression of nicotinamide adenine dinucleotide phosphate oxidase type 4 (NOX4), which is predominantly expressed in hepatic microvessels. Materials and methodsAnesthetized male Sprague–Dawley rats were subjected to 60-min ischemia of the left liver lobes and 180-min reperfusion, with or without GPC treatment (50 mg/kg intravenously 5 min before reperfusion, n = 6 each). A third group (n = 6) served as saline-treated control. Noninvasive online examination of the hepatic microcirculation was performed hourly by means of modified spectrometry. Plasma tumor necrosis factor (TNF-α), high-mobility group box 1 protein (HMGB1), plasma aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase levels, tissue xanthine oxidoreductase (XOR) and myeloperoxidase (MPO) activities, and expressions of NOX2 and NOX4 proteins were determined. ResultsLiver IR resulted in significant increases in NOX2 and NOX4 expressions and XOR and MPO activities, and approximately 2-fold increases in the levels of the inflammatory cytokines TNF-α and HMGB1. The microvascular blood flow and tissue oxygen saturation decreased by ∼20% from control values. GPC administration ameliorated the postischemic microcirculatory deterioration and reduced the liver necroenzyme levels significantly; the NOX4 expression, MPO activity, and HMGB1 level were also decreased, whereas the NOX2 expression, TNF-α level, and XOR activity were not influenced by GPC pretreatment. ConclusionsNOX4 activation is a decisive component in the IR-induced microcirculatory dysfunction. Exogenous GPC ameliorates the inflammatory activation, and preserves the postischemic microvascular perfusion and liver functions, these effects being associated with a reduced hepatic expression of NOX4.

Growth kinetics of a Helianthus annuus and a Salvia fruticosa suspension cell line: Shake flask cultivations with online monitoring system

Plants produce a variety of secondary metabolites to defend themselves against herbivores or to attract pollinating insects. Plant cell biotechnology offers excellent opportunities in order to use such secondary plant metabolites to produce goods with consistent quality and quantity throughout the year, and therefore to act independently from biotic and abiotic environmental factors. This article presents results of an extensive study of plant cell in vitro cultivation in a modern shake flask system with noninvasive online respiration activity monitoring unit. Comprehensive screening experiments confirm the successful transfer of a model culture (sunflower suspension) into the shake flask monitoring device and the suitability of this respiration activity monitoring unit as qualified tool for screening of plant in vitro cultures (sunflower and sage suspension). The authors demonstrate deviations between online and offline data due to varying water evaporation from different culture flask types. The influence of evaporation on growth‐specific parameters thereby rises with increasing cultivation time. Furthermore, possibilities to minimize the impact of evaporation, either by adjusting the inlet air moisture or by measuring the evaporation in combination with an appropriate correction of the measured growth values are shown.

Non-invasive online detection of microbial lysine formation in stirred tank bioreactors by using calorespirometry

Non-invasive methods for online monitoring of biotechnological processes without compromising the integrity of the reactor system are very important to generate continuous data. Even though calorimetry has been used in conventional biochemical analysis for decades, it has not yet been specifically applied for online detection of product formation at technical scale. Thus, this article demonstrates a calorespirometric method for online detection of microbial lysine formation in stirred tank bioreactors. The respective heat generation of two bacterial strains, Corynebacterium glutamicum ATCC 13032 (wild-type) and C. glutamicum DM1730 (lysine producer), was compared with the O2 -consumption in order to determine whether lysine was formed. As validation of the proposed calorespirometric method, the online results agreed well with the offline measured data. This study has proven that calorespirometry is a viable non-invasive technique to detect product formation at any time point.

Optimizing the Drying Parameters for Hot-Air–Dried Apples

The aim of the work was to develop an optimized routine for apple drying. The interaction of the drying parameters air temperature (35–85°C), dew point temperature (5–30°C), and air velocity (2.0–4.8 m/s) with drying time, color changes, and shrinkage was determined. Non-invasive online measurement techniques in the form of artificial vision systems in visible and infrared spectrum were developed and applied to guarantee an uninterrupted process. Quantification methods for the determination of color and shape changes of apple slices were established based on the images taken. Results show that digital images are a feasible alternative for the monitoring of the relative changes in L* (R2 = 0.92, p < 0.001), a* (R2 = 0.96, p < 0.001), and b* (R2 = 0.96, p < 0.001) during the drying of apples. It was observed that the color parameters as a function of moisture content follow a third-order development while shrinkage was linear (p < 0.001). The developed models for drying time tdr (R2 = 0.99, p < 0.001), Total Color Difference ΔE (R2 = 0.95, p < 0.001), and shrinkage S (R2 = 0.68, p < 0.05) illustrate high interdependencies of the factors involved for the quality criteria studied. Throughout the parameter space investigated, increasing air velocity was shown to have a positive effect on the quality criteria investigated.

A system of miniaturized stirred bioreactors for parallel continuous cultivation of yeast with online measurement of dissolved oxygen and off‐gas

Chemostat cultivation is a powerful tool for physiological studies of microorganisms. We report the construction and application of a set of eight parallel small-scale bioreactors with a working volume of 10 mL for continuous cultivation. Hungate tubes were used as culture vessels connected to multichannel-peristaltic pumps for feeding fresh media and removal of culture broth and off-gas. Water saturated air is sucked into the bioreactors by applying negative pressure, and small stirrer bars inside the culture vessels allow sufficient mixing and oxygen transfer. Optical sensors are used for non-invasive online measurement of dissolved oxygen, which proved to be a powerful indicator of the physiological state of the cultures, particularly of steady-state conditions. Analysis of culture exhaust-gas by means of mass spectrometry enables balancing of carbon. The capacity of the developed small-scale bioreactor system was validated using the fission yeast Schizosaccharomyces pombe, focusing on the metabolic shift from respiratory to respiro-fermentative metabolism, as well as studies on consumption of different substrates such as glucose, fructose, and gluconate. In all cases, an almost completely closed carbon balance was obtained proving the reliability of the experimental setup.

Monitoring tissue oxygenation by near infrared spectroscopy (NIRS): background and current applications

Conventional cardiovascular monitoring may not detect tissue hypoxia, and conventional cardiovascular support aiming at global hemodynamics may not restore tissue oxygenation. NIRS offers non-invasive online monitoring of tissue oxygenation in a wide range of clinical scenarios. NIRS monitoring is commonly used to measure cerebral oxygenation (rSO2), e.g. during cardiac surgery. In this review, we will show that tissue hypoxia occurs frequently in the perioperative setting, particularly in cardiac surgery. Therefore, measuring and obtaining adequate tissue oxygenation may prevent (postoperative) complications and may thus be cost-effective. NIRS monitoring may also be used to detect tissue hypoxia in (prehospital) emergency settings, where it has prognostic significance and enables monitoring of therapeutic interventions, particularly in patients with trauma. However, optimal therapeutic agents and strategies for augmenting tissue oxygenation have yet to be determined.

Determination of Dialysis Dose: A Clinical Comparison of Methods

Background: Guidelines recommend regular measurements of the delivered hemodialysis dose Kt/V. Nowadays, automatic non-invasive online measurements are available as alternatives to the conventional method with blood sampling, laboratory analysis, and calculation. Methods:In a prospective clinical trial, three different methods determining dialysis dose were simultaneously applied: Kt/V_Dau (conventional method with Daugirdas’ formula), Kt/V_OCM [online clearance measurement (OCM) with urea distribution volume V based on anthropometric estimate], and Kt/V_BCM [OCM measurement with V measured by bioimpedance analysis (Body Composition Monitor)]. Results:1,076 hemodialysis patients were analyzed. The dialysis dose was measured as Kt/V_Dau = 1.74 ± 0.45, Kt/V_OCM = 1.47 ± 0.34, and Kt/V_BCM = 1.65 ± 0.42. The difference between Kt/V_OCM and Kt/V_BCM was due to the difference between anthropometric estimated V_Watson and measured V_BCM. Compared to Kt/V_Dau, Kt/V_OCM was 15% lower and Kt/V_BCM 5% lower. Kt/V_Dau was incidentally prone to falsely high values due to operative errors, whereas in these cases OCM-based measurements Kt/V_OCM and Kt/V_BCM delivered realistic values. Conclusions:The automated OCM Kt/V_OCM with anthropometric estimation of urea distribution volume was the easiest method to use, but Kt/V_BCM with measured urea distribution volume was closer to the conventional method.

In-process distortion measurement during a gas quenching process through digital speckle photography

In this work digital speckle photography is applied to measure changes in length and curvature of a stepped steel shaft during a gas quenching process with sub-pixel accuracy. Changes in the length of the workpiece were measured and compared to the results from a coordinate tactile machine, which were taken at room temperature. Measurements were undertaken in an industrial environment, i.e. without vibration isolation, in order to gain insight on the sensitivity of this method to the vibrations inherent to the process. The motivation behind this study is the measurement of three dimensional deformations of the object in order to facilitate minimization and/or compensation of distortions in steel quenching processes, which is crucial for quality and product assurance. From the preliminary results presented in this work it is clear to see that speckle photography enables a non-invasive, time resolved and accurate online measurement of these defomations. Furthermore, it is apparent that the method is insensitive to different interfering effects, e.g. the gas field and black body radiation of the hot object, within the quenching stand. The well reproducible results attained here will help to better monitor quenching in flexible gas fields and thereby play an important role in facilitating distortionless quenching.

Acoustic emission: Towards a real-time diagnosis technique for Proton Exchange Membrane Fuel Cell operation

This paper deals with one of the needs for PEMFC to be economically reliable: diagnosis tool for water management. This issue is actually a key parameter for both performance and durability improvement. Acoustic emission (AE) technique was employed to survey PEM single cell under various operating conditions. AE events coming from different sources have thus been identified, classified and finally ascribed to different phenomena induced by MEA water uptake and/or biphasic flow in the gas channel thanks to a statistical post-treatment of the acoustic data. Results, although qualitative, seems trusty enough to unravel hidden correlations between AE hits and physicochemical phenomena taking place during the cell operation and open up the way for an innovative and non-invasive online diagnosis tool.

Online assessment of biofilm development, sloughing and forced detachment in tube reactor by means of magnetic resonance microscopy

Magnetic resonance microscopy (MRM) was successfully applied for non-invasive online monitoring of biofilm development, sloughing, and forced detachment. Biofilm cultivation was performed in a tube reactor directly placed in the MRM scanner. Based on the differences in relaxation time of free and bound protons, the distributed water signal was allocated to the bulk and the biofilm phase. The velocity of the flowing water in the tube reactor was measured in all three directions (x, y, and z) at spatial resolutions of 78 microm. From the velocity data, maps of flow gradients (shear rates) were derived. The experiments showed that a more compact biofilm structure is sloughed off in total with nearly no biomass left on the substratum. Continued biofilm cultivation resulted in filamentous biofilm structures, which did not show any sloughing. Experiments at higher Reynolds numbers were performed in order to force biofilm detachment. Continuous measuring of proton velocity and biomass was used to characterize the different stages of biofilm development. The measurements revealed that biofilms are able to resist extremely high local shear stress being raised up to factor of 20 compared to the mean local shear stress acting on the complete biofilm surface. The maximum local shear stress of single biofilm structures exposed to flow was found to be on average seven times higher compared to the mean local shear stress of the entire biofilm surface. MRM was able to visualize and quantify the development of biofilms and interaction of biofilms with the surrounding fluid at the meso-scale. It is suggested that detachment and sloughing depends on both internal and external structural parameters.

Permanent Occlusion of Feeding Arteries and Draining Veins in Solid Mouse Tumors by Vascular Targeted Photodynamic Therapy (VTP) with Tookad

BackgroundAntiangiogenic and anti-vascular therapies present intriguing alternatives to cancer therapy. However, despite promising preclinical results and significant delays in tumor progression, none have demonstrated long-term curative features to date. Here, we show that a single treatment session of Tookad-based vascular targeted photodynamic therapy (VTP) promotes permanent arrest of tumor blood supply by rapid occlusion of the tumor feeding arteries (FA) and draining veins (DV), leading to tumor necrosis and eradication within 24–48 h.Methodology/Principal FindingsA mouse earlobe MADB106 tumor model was subjected to Tookad-VTP and monitored by three complementary, non-invasive online imaging techniques: Fluorescent intravital microscopy, Dynamic Light Scattering Imaging and photosensitized MRI. Tookad-VTP led to prompt tumor FA vasodilatation (a mean volume increase of 70%) with a transient increase (60%) in blood-flow rate. Rapid vasoconstriction, simultaneous blood clotting, vessel permeabilization and a sharp decline in the flow rates then followed, culminating in FA occlusion at 63.2 sec±1.5SEM. This blockage was deemed irreversible after 10 minutes of VTP treatment. A decrease in DV blood flow was demonstrated, with a slight lag from FA response, accompanied by frequent changes in flow direction before reaching a complete standstill. In contrast, neighboring, healthy tissue vessels of similar sizes remained intact and functional after Tookad-VTP.Conclusion/SignificanceTookad-VTP selectively targets the tumor feeding and draining vessels. To the best of our knowledge, this is the first mono-therapeutic modality that primarily aims at the larger tumor vessels and leads to high cure rates, both in the preclinical and clinical arenas.

13CO2 breath tests, a tool to assess intestinal and liver function in the ICU?

CO2 breath tests, based on nondispersive infrared (NDIR) measurement technology, offer the chance for a noninvasive online quantitation of physiological processes. With recent extensions of the NDIR measurement technology breath tests could be used in an ICU setting without any restriction. Since online tools to assess feed intolerance with gastric emptying and to quantify gradual changes in liver function are still missing, this review explores the potential of breath tests to fill this gap. Gastric emptying may be correctly quantified; however, the corresponding tests fail to capture aberrations in nutrient absorption, which appear to be linked to hyperglycemia and insulin resistance and may contribute to feed intolerance. The progression or ameloriation of liver injury could be assessed with breath tests, which cannot, however, distinguish between functional and macrocirculatory or microcirculatory disorders. Breath tests for liver function and gastric emptying taken alone may fail in their ability to specifically quantify the clinical disorders. However, invasive test extensions could help to characterize their validity and thus to identify additional, noninvasive measurements to assure and expand this domain.

Dynamic retinal vessel response to flicker in age-related macular degeneration patients before and after vascular endothelial growth factor inhibitor injection

Retinal vessel responses to flickering light are different in various systemic and ocular diseases and can be improved after successful therapy. We investigated retinal vessel response to flickering light in age-related macular degeneration (AMD) patients before and after treatment with a single intravitreal bevacizumab (Avastin(®) ) injection. In 10 patients with exudative AMD [age: median (1.quartile; 3.quartile) 76.0 (73.5; 80.0) years], retinal vessel reactions were examined by Dynamic Vessel Analyser (DVA) before and 3 months after a single intravitreal application of bevacizumab (1.25 mg). A baseline measurement was followed by three consecutive monochromatic flicker stimulations (530-600 nm, 12.5 Hz, 20 seconds). Temporal retinal vessel reaction was analysed and compared with the reaction in healthy controls. Mean arterial dilation at the end of flicker was not different in all groups. For veins this parameter amounted to: pre-treatment, 2.6 (1.7; 3.9)%; post-treatment, 2.9 (2.4; 4.0)%; control, 4.3 (3.2; 5.7)%; significant: pre-treatment - control (Dunnett's procedure, p < 0.05). Maximal dilation occurred in arteries at: pre-treatment, 17.5 (14.8; 32.5) seconds; post-treatment, 18.0 (16.6; 30.6) seconds; control, 14.5 (10.8; 17.3) seconds. Both AMD groups were slower (p < 0.05): in veins at 17.0 (14.5; 20.0) seconds, 12.8 (8.6; 14.8) seconds and 18.5 (17.1; 19.9) seconds, respectively; significant post-treatment - control (p < 0.05). In the post-treatment AMD group arterial constriction after stimulation occurred more slowly compared with the control group (p < 0.05). Dynamic retinal arterial and venous reactions to flickering light are altered in AMD compared with controls. Three months after a single injection of a vascular endothelial growth factor inhibitor, the investigated retinal dynamic vascular parameters were not altered in our study.

Two-Photon Techniques in Tissue Engineering

NIR radiation in the range of about 800 nm is less absorbed by biological tissues and is suited for triggering photonic effects using femtosecond pulsed Ti:Sa lasers. Especially in the life sciences, two-photon techniques are gaining greater importance. We introduce two laser applications for tissue engineering: the autofluorescent visualization of cells seeded on 3D scaffolds after two-photon excitation; and the manufacturing of 3D-structured hydrogel-like scaffolds by triggering free-radical polymerization processes within polymerizable precursors. Primary bovine chondrocytes were cultivated on collagen I/III scaffolds using a flow chamber system coupled with a two-photon laser scanning microscope (2PLSM). During the incubation the cell population was hydrostatically stimulated. The selective visualization of unlabeled cells and scaffolds was achieved by spectral autofluorescence imaging. To gain some insight into scaffold-mediated effects on cell growth and cell differentiation, hydrogel-like scaffolds with well defined 3D structures were generated by two-photon polymerization (2PP) using methacrylated urethane and polyethyleneglycol diacrylate. We were able to show that spectral autofluorescence imaging provides spatially resolved data for the non-invasive online control of the tissue engineering process as well as the quantification of cell distribution within the scaffold. The fabrication of 3D 2PP scaffolds made from hydrogel-forming monomers and their effect on cell attachment and cell growth were also shown. Two-photon techniques provide powerful tools for both the non-invasive online visualization of 3D cell-scaffold constructs and the structuring of 3D cultivation environments. The application of these techniques is also suitable for integration into micro-systems technology (e.g. BioMEMS, Cells-on-Chip, Lab-on-a Chip).

Comparison of threshold irradiances and online dosimetry for selective retina treatment (SRT) in patients treated with 200 nanoseconds and 1.7 microseconds laser pulses

Selective retina therapy (SRT) solely affecting the RPE while sparing of the photoreceptors is usually performed with a train of repetitive laser pulses of 1.7 microseconds in duration. It was our purpose to evaluate the principle feasibility of SRT with shorter 200 nanoseconds laser pulses in patients. Nineteen patients with macular disorders [diabetic maculopathy (DMP), geographic atrophy (GA), drusen maculopathy and central serous chorioretinopathy (CSR)] were treated with a prototype of a SRT laser (Nd:YLF laser; 527 nm; 1.7 microseconds and 200 nanoseconds pulse duration; 30 pulses at 100 Hz; spot size: 200 microm). Test lesions (n = 175) with increasing energy were applied at the lower arcade to determine the individual angiographic and ophthalmoscopic threshold radiant exposures (therapeutic window) before applying the central treatment lesions within these ranges additionally guided by online optoacoustic measurements. Postoperatively RPE damage was visualized and confirmed by fluorescein angiographic leakage and correlated with optoacoustic results. Additionally ED(50) damage thresholds were calculated by probit analysis. None of the short repetitive 200 nanoseconds laser pulses led to retinal hemorrhages or retinal ruptures. Nearly all of the test- and treatment lesions could be visualized by angiography indicating desired RPE damage but were ophthalmoscopically invisible suggesting intact neurosensory retinal structures. ED(50) cell damage threshold energies were significantly lower using 200 nanoseconds (99.6 microJ; n = 122) instead of 1.7 microseconds (196.3 microJ; n = 53) laser pulses. Optoacoustic and angiographic visibility correlated in 83.7% (200 nanoseconds) and 87.5% (1.7 microseconds). Selective RPE effects can safely be achieved using shorter 200 nanoseconds laser pulses in patients without adverse effects to the neurosensory retina. The required pulse energy compared to the standard 1.7 microseconds regime was reduced by about a factor of 2 suggesting a reduced heat generation and flow into adjacent tissues during the shorter laser impact and thus possibly enhancing selectivity. Optoacoustics also seem to be a viable alternative in 200 nanoseconds treatment for a non-invasive online dosimetry control system.

Electrical impedance tomography to confirm correct placement of double-lumen tube: a feasibility study

BackgroundDouble-lumen tubes (DLTs) are frequently used to establish one-lung ventilation (OLV). Their correct placement is crucial. We hypothesized that electrical impedance tomography (EIT) reliably displays distribution of ventilation between left and right lung and may thus be used to verify correct DLT placement online. MethodsRegional ventilation was studied by EIT in 40 patients requiring insertion of left-sided DLTs for OLV during thoracic surgery. EIT was recorded during two-lung ventilation before induction of anaesthesia and after DLT placement, and during OLV in the supine and subsequently in the lateral position. EIT measurements were made before and after verification of correct DLT placement by fibreoptic bronchoscopy (FOB). ResultsEIT accurately displayed distribution of ventilation between left and right lung online. All cases (n=5) of initially misplaced DLTs in the contralateral right main bronchus were detected by EIT. However, EIT did not allow prediction of FOB-detected endobronchial cuff misplacement requiring DLT repositioning. Furthermore, after DLT repositioning, distribution of ventilation, as assessed by EIT, did not change significantly (all P>0.5). ConclusionsThis study demonstrates that EIT enables accurate display of left and right lung ventilation and, thus, non-invasive online recognition of misplacement of left-sided DLTs in the contralateral main bronchus. However, as distribution of ventilation did not correlate with endobronchial cuff placement, EIT cannot replace FOB in the routine control of DLT position.