Performance of Novel Patient Interface for Electrical Impedance Tomography Applications

Waldmann, Andreas D.; Wodack, Karin; März, Alexander; Ukere, Asi; Trepte, Constantin; Böhm, Stephan H.; Reuter, Daniel A.

doi:10.1007/s40846-017-0264-y

Cited by 19 publications

(19 citation statements)

References 24 publications

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“…An example of such a 3D image is shown in Fig 2b . Then, the 32 electrodes were connected to a slightly modified version of the EIT SensorBelt (Swisstom AG, Landquart, Switzerland) [ 22 ] in combination with the BB 2 EIT device (Swisstom AG, Landquart, Switzerland). To achieve this connection, the conductive textile was disconnected from the active electrodes and instead, commercially available ECG cables were attached and connected to the self-adhesive gel electrodes.…”

Section: Methodsmentioning

confidence: 99%

Accuracy and reliability of noninvasive stroke volume monitoring via ECG-gated 3D electrical impedance tomography in healthy volunteers

et al. 2018

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Cardiac output (CO) and stroke volume (SV) are parameters of key clinical interest. Many techniques exist to measure CO and SV, but are either invasive or insufficiently accurate in clinical settings. Electrical impedance tomography (EIT) has been suggested as a noninvasive measure of SV, but inconsistent results have been reported. Our goal is to determine the accuracy and reliability of EIT-based SV measurements, and whether advanced image reconstruction approaches can help to improve the estimates. Data were collected on ten healthy volunteers undergoing postural changes and exercise. To overcome the sensitivity to heart displacement and thorax morphology reported in previous work, we used a 3D EIT configuration with 2 planes of 16 electrodes and subject-specific reconstruction models. Various EIT-derived SV estimates were compared to reference measurements derived from the oxygen uptake. Results revealed a dramatic impact of posture on the EIT images. Therefore, the analysis was restricted to measurements in supine position under controlled conditions (low noise and stable heart and lung regions). In these measurements, amplitudes of impedance changes in the heart and lung regions could successfully be derived from EIT using ECG gating. However, despite a subject-specific calibration the heart-related estimates showed an error of 0.0 ± 15.2 mL for absolute SV estimation. For trending of relative SV changes, a concordance rate of 80.9% and an angular error of −1.0 ± 23.0˚were obtained. These performances are insufficient for most clinical uses. Similar conclusions were derived from lung-related estimates. Our findings indicate that the key difficulty in EITbased SV monitoring is that purely amplitude-based features are strongly influenced by other factors (such as posture, electrode contact impedance and lung or heart conductivity). All the data of the present study are made publicly available for further investigations.

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Section: Methodsmentioning

confidence: 99%

Accuracy and reliability of noninvasive stroke volume monitoring via ECG-gated 3D electrical impedance tomography in healthy volunteers

et al. 2018

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“…EIT data were measured using the Swisstom BB 2 (Swisstom AG, Landquart, Switzerland). Each patient’s thorax circumference was measured, and the textile electrode belt of appropriate size fastened along the 6th intercostal space [ 37 ]. Fifty cross-sectional impedance images were recorded every second for a period of 10 min under stable conditions.…”

Section: Methodsmentioning

confidence: 99%

Regional expiratory time constants in severe respiratory failure estimated by electrical impedance tomography: a feasibility study

et al. 2018

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BackgroundElectrical impedance tomography (EIT) has been used to guide mechanical ventilation in ICU patients with lung collapse. Its use in patients with obstructive pulmonary diseases has been rare since obstructions could not be monitored on a regional level at the bedside. The current study therefore determines breath-by-breath regional expiratory time constants in intubated patients with chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS).MethodsExpiratory time constants calculated from the global impedance EIT signal were compared to the pneumatic volume signals measured with an electronic pneumotachograph. EIT-derived expiratory time constants were additionally determined on a regional and pixelwise level. However, regional EIT signals on a single pixel level could in principle not be compared with similar pneumatic changes since these measurements cannot be obtained in patients. For this study, EIT measurements were conducted in 14 intubated patients (mean Simplified Acute Physiology Score II (SAPS II) 35 ± 10, mean time on invasive mechanical ventilation 36 ± 26 days) under four different positive end-expiratory pressure (PEEP) levels ranging from 10 to 17 cmH2O. Only patients with moderate-severe ARDS or COPD exacerbation were included into the study, preferentally within the first days following intubation.ResultsSpearman’s correlation coefficient for comparison between EIT-derived time constants and those from flow/volume curves was between 0.78 for tau (τ) calculated from the global impedance signal up to 0.83 for the mean of all pixelwise calculated regional impedance changes over the entire PEEP range. Furthermore, Bland-Altman analysis revealed a corresponding bias of 0.02 and 0.14 s within the limits of agreement ranging from − 0.50 to 0.65 s for the aforementioned calculation methods. In addition, exemplarily in patients with moderate-severe ARDS or COPD exacerbation, different PEEP levels were shown to have an influence on the distribution pattern of regional time constants.ConclusionsEIT-based determination of breath-by-breath regional expiratory time constants is technically feasible, reliable and valid in invasively ventilated patients with severe respiratory failure and provides a promising tool to individually adjust mechanical ventilation in response to the patterns of regional airflow obstruction.Trial registrationGerman Trial Register DRKS 00011650, registered 01/31/17.Electronic supplementary materialThe online version of this article (10.1186/s13054-018-2137-3) contains supplementary material, which is available to authorized users.

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“…For a 32-electrode system, the voltage potential developed on the furthest electrode could be 60-70 dB smaller than the potential at the current drive electrode. The textile electrodes used have a skin-electrode contact impedance ~500 Ω [25]. When injecting a current of 6 mAp-p (which is within the international medical safety standard IEC-60601) it produces ~3 Vp-p at the current drive electrode, and hence a voltage signal at the furthest electrode that is above the fabric-electrode noise level.…”

Section: A Current Stimulation and Contact Impedance Monitoringmentioning

confidence: 99%

“…Although it is demonstrated in an adult system in the form of an active 'wearable belt' its specification technology conforms to the requirements of neonatal applications. The main features of this 32 electrode EIT system (CRADLvision 1.0) are: 1) a high performance ASIC for active electrodes; 2) a high frame rate (107 fps); 3) disposable textile electrode dressing [25]; and 4) multi-sensing functionality (heart rate monitoring, incubator temperature and humidity, and belt orientation and patient torso detection aiding EIT model selection for enhanced image reconstruction). The rest of the paper is organized as follows.…”

Section: Introductionmentioning

confidence: 99%

A High Frame Rate Wearable EIT System Using Active Electrode ASICs for Lung Respiration and Heart Rate Monitoring

Jiang

Bardill

et al. 2018

IEEE Trans. Circuits Syst. I

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Performance of Novel Patient Interface for Electrical Impedance Tomography Applications

Cited by 19 publications

References 24 publications

Accuracy and reliability of noninvasive stroke volume monitoring via ECG-gated 3D electrical impedance tomography in healthy volunteers

Accuracy and reliability of noninvasive stroke volume monitoring via ECG-gated 3D electrical impedance tomography in healthy volunteers

Regional expiratory time constants in severe respiratory failure estimated by electrical impedance tomography: a feasibility study

A High Frame Rate Wearable EIT System Using Active Electrode ASICs for Lung Respiration and Heart Rate Monitoring

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