Electrical Impedance Tomography Examinations Research Articles

Bedside electrical impedance tomography in early diagnosis of pneumothorax in mechanically ventilated ICU patients - a single-center retrospective cohort study.

This study aimed to evaluate the routine use of electrical impedance tomography (EIT) to diagnose pneumothorax (PTX) in mechanically ventilated patients in the intensive care unit (ICU). A retrospective cohort study was conducted including mechanically ventilated supine patients who received EIT examinations. The EIT-based tidal variation was divided into ventral and dorsal regions of interest (ROIs): upper right (UR, ROI1), upper left (UL, ROI2) lower right (LR, ROI3), and lower left (LL, ROI4), and the ventilation defect score (DS) was calculated in each quadrant. Furthermore, horizontal ventral ventilation index (HVVI) was defined as ROI1% / ROI2% in the two ventral quadrants if ROI1% > ROI2%, otherwise HVVI = ROI2% / ROI1%. A total of 203 patients were included, 25 of them with confirmed PTX. In the PTX patients, preceding cardiac surgery was the most common cause of PTX. Compared with the patients without PTX, the PTX patients had a higher DS in the ventral quadrants [median and interquartile range (IQR): 1.00 (0.00, 2.00) vs. 0.00 (0.00, 0.00), P < 0.001] respectively, but similar in the dorsal quadrants [median and IQR: 1.00 (0.00, 1.00) vs. 0.00 (0.00, 1.00), P = 0.722]. Moreover, a higher HVVI was found in the PTX group [median and IQR: 2.51 (1.58, 3.52) vs. 1.36 (1.15, 1.77), P < 0.001]. The area under the receiver operating characteristic curve of the HVVI to differentiate PTX from non-PTX was 0.88, with a sensitivity of 70% and a specificity of 90% when the cut-off value was 2.57. The ventilation defect in the ventral regions and a high HVVI on EIT were observed in mechanically ventilated patients with PTX, which should trigger further diagnostics to confirm it.

Prolonged Continuous Monitoring of Regional Lung Function in Infants with Respiratory Failure.

Rationale: Electrical impedance tomography (EIT) allows instantaneous and continuous visualization of regional ventilation and changes in end-expiratory lung volume at the bedside. There is particular interest in using EIT for monitoring in critically ill neonates and young children with respiratory failure. Previous studies have focused only on short-term monitoring in small populations. The feasibility and safety of prolonged monitoring with EIT in neonates and young children have not been demonstrated yet. Objectives: To evaluate the feasibility and safety of long-term EIT monitoring in a routine clinical setting and to describe changes in ventilation distribution and homogeneity over time and with positioning in a multicenter cohort of neonates and young children with respiratory failure. Methods: At four European University hospitals, we conducted an observational study (NCT02962505) on 200 patients with postmenstrual ages (PMA) between 25 weeks and 36 months, at risk for or suffering from respiratory failure. Continuous EIT data were obtained using a novel textile 32-electrode interface and recorded at 48 images/s for up to 72 hours. Clinicians were blinded to EIT images during the recording. EIT parameters and the effects of body position on ventilation distribution were analyzed offline. Results: The average duration of EIT measurements was 53 ± 20 hours. Skin contact impedance was sufficient to allow image reconstruction for valid ventilation analysis during a median of 92% (interquartile range, 77-98%) of examination time. EIT examinations were well tolerated, with minor skin irritations (temporary redness or imprint) occurring in 10% of patients and no moderate or severe adverse events. Higher ventilation amplitude was found in the dorsal and right lung areas when compared with the ventral and left regions, respectively. Prone positioning resulted in an increase in the ventilation-related EIT signal in the dorsal hemithorax, indicating increased ventilation of the dorsal lung areas. Lateral positioning led to a redistribution of ventilation toward the dependent lung in preterm infants and to the nondependent lung in patients with PMA > 37 weeks. Conclusions: EIT allows continuous long-term monitoring of regional lung function in neonates and young children for up to 72 hours with minimal adverse effects. Our study confirmed the presence of posture-dependent changes in ventilation distribution and their dependency on PMA in a large patient cohort. Clinical trial registered with www.clinicaltrials.gov (NCT02962505).

Chest electrical impedance tomography measures in neonatology and paediatrics—a survey on clinical usefulness

Objective: Chest electrical impedance tomography (EIT) is currently applied in neonatal and paediatric patients, mainly within clinical studies. The findings of these studies imply that lung monitoring using EIT provides valuable information on regional lung ventilation and aeration at the bedside that might improve the therapy and care of this fragile patient population. In view of this postulated future use of EIT in neonatology and paediatrics we have conducted an international survey to assess the perceived usefulness of several measures derived from EIT examinations. Approach: A questionnaire validating the clinical usefulness of 14 previously described EIT measures was designed and sent to 36 clinicians with previous experience with EIT in neonatal and paediatric patients. A numerical rating scale was used to assess the usefulness of each measure. Main results: Thirty-four clinicians from 12 countries responded to the invitation and 32 filled in the questionnaire. The mean clinical and EIT experience (±SD) of the respondents was 19.4 ± 9.1 years and 7.7 ± 5.8 years, respectively. The top-rated measures were the global inhomogeneity index, silent spaces, change in end-expiratory lung impedance and ventrodorsal centre of ventilation. The bottom-rated were the regional respiratory time constant, tidal volume normalised to ml, respiratory rate and heart rate on the last rank. Significance: The survey revealed that EIT measures characterising the ventilation and aeration distribution and the degree of their heterogeneity were deemed particularly useful. Respiratory rate, heart rate and overall tidal volume were considered less useful probably because these parameters are already routinely assessed by other conventional methods.

Detection of pulmonary oedema by electrical impedance tomography: validation of previously proposed approaches in a clinical setting

Objective: The aim of the present study was to evaluate two previously proposed approaches based on electrical impedance tomography (EIT) to assess pulmonary oedema at the bedside. Approach: Fourteen patients with acute respiratory distress syndrome were included and examined prospectively. Patients were rotated laterally along their longitudinal axis from supine to 45-degree left and right tilt to induce a gravity-dependent redistribution of pulmonary oedema. After a 20 min equilibration period at each of the three positions, 2 min EIT data were recorded and analyzed. Left-to-right lung and anterior-to-posterior ventilation ratios were calculated for each posture. The slopes of the regression lines in all three postures were then determined. The same examination was performed on the consecutive day. The EIT-derived parameters were compared with transcardiopulmonary thermodilution measurements. Main results: The correlations between the EIT and transcardiopulmonary thermodilution parameters were low (correlation coefficients r < 0.4) and not significant regardless of the examination days. Significance: Despite previous clinical and experimental observations, left-to-right and anterior-to-posterior ventilation ratios derived from EIT examinations after postural changes did not reflect total extravascular lung water in our study population. Clinical trial registration. NCT02870894 Registered 17 AUG 2016 (https://clinicaltrials.gov).

Clinical performance of a novel textile interface for neonatal chest electrical impedance tomography

Objective: Critically ill neonates and infants might particularly benefit from continuous chest electrical impedance tomography (EIT) monitoring at the bedside. In this study a textile 32-electrode interface for neonatal EIT examination has been developed and tested to validate its clinical performance. The objectives were to assess ease of use in a clinical setting, stability of contact impedance at the electrode–skin interface and possible adverse effects. Approach: Thirty preterm infants (gestational age: 30.3 ± 3.9 week (mean ± SD), postnatal age: 13.8 ± 28.2 d, body weight at inclusion: 1727 ± 869 g) were included in this multicentre study. The electrode–skin contact impedances were measured continuously for up to 3 d and analysed during the initial 20-min phase after fastening the belt and during a 10 h measurement interval without any clinical interventions. The skin condition was assessed by attending clinicians. Main results: Our findings imply that the textile electrode interface is suitable for long-term neonatal chest EIT imaging. It does not cause any distress for the preterm infants or discomfort. Stable contact impedance of about 300 Ohm was observed immediately after fastening the electrode belt and during the subsequent 20 min period. A slight increase in contact impedance was observed over time. Tidal variation of contact impedance was less than 5 Ohm. Significance: The availability of a textile 32-electrode belt for neonatal EIT imaging with simple, fast, accurate and reproducible placement on the chest strengthens the potential of EIT to be used for regional lung monitoring in critically ill neonates and infants.

Chest electrical impedance tomography examination, data analysis, terminology, clinical use and recommendations: consensus statement of the TRanslational EIT developmeNt stuDy group

Electrical impedance tomography (EIT) has undergone 30 years of development. Functional chest examinations with this technology are considered clinically relevant, especially for monitoring regional lung ventilation in mechanically ventilated patients...

Regional lung function determined by electrical impedance tomography during bronchodilator reversibility testing in patients with asthma

The measurement of rapid regional lung volume changes by electrical impedance tomography (EIT) could determine regional lung function in patients with obstructive lung diseases during pulmonary function testing (PFT). EIT examinations carried out before and after bronchodilator reversibility testing could detect the presence of spatial and temporal ventilation heterogeneities and analyse their changes in response to inhaled bronchodilator on the regional level. We examined seven patients suffering from chronic asthma (49 ± 19 years, mean age ± SD) using EIT at a scan rate of 33 images s−1 during tidal breathing and PFT with forced full expiration. The patients were studied before and 5, 10 and 20 min after bronchodilator inhalation. Seven age- and sex-matched human subjects with no lung disease history served as a control study group. The spatial heterogeneity of lung function measures was quantified by the global inhomogeneity indices calculated from the pixel values of tidal volume, forced expiratory volume in one second (FEV1), forced vital capacity (FVC), peak flow and forced expiratory flow between 25% and 75% of FVC as well as histograms of pixel FEV1/FVC values. Temporal heterogeneity was assessed using the pixel values of expiration times needed to exhale 75% and 90% of pixel FVC. Regional lung function was more homogeneous in the healthy subjects than in the patients with asthma. Spatial and temporal ventilation distribution improved in the patients with asthma after the bronchodilator administration as evidenced mainly by the histograms of pixel FEV1/FVC values and pixel expiration times. The examination of regional lung function using EIT enables the assessment of spatial and temporal heterogeneity of ventilation distribution during bronchodilator reversibility testing. EIT may become a new tool in PFT, allowing the estimation of the natural disease progression and therapy effects on the regional and not only global level.

Electrical impedance tomography imaging of the cardiopulmonary system.

This review article summarizes the recent advances in electrical impedance tomography (EIT) related to cardiopulmonary imaging and monitoring on the background of the 30-year development of this technology. EIT is expected to become a bedside tool for monitoring and guiding ventilator therapy. In this context, several studies applied EIT to determine spatial ventilation distribution during different ventilation modes and settings. EIT was increasingly combined with other signals, such as airway pressure, enabling the assessment of regional respiratory system mechanics. EIT was for the first time used prospectively to define ventilator settings in an experimental and a clinical study. Increased neonatal and paediatric use of EIT was noted. Only few studies focused on cardiac function and lung perfusion. Advanced radiological imaging techniques were applied to assess EIT performance in detecting regional lung ventilation. New approaches to improve the quality of thoracic EIT images were proposed. EIT is not routinely used in a clinical setting, but the interest in EIT is evident. The major task for EIT research is to provide the clinicians with guidelines how to conduct, analyse and interpret EIT examinations and combine them with other medical techniques so as to meaningfully impact the clinical decision-making.

Regional ventilation distribution determined by electrical impedance tomography: Reproducibility and effects of posture and chest plane

Reliable assessment of regional lung ventilation and good reproducibility of electrical impedance tomography (EIT) data are the prerequisites for the future application of EIT in a clinical setting. The aims of our study were to determine (i) the reproducibility of repeated EIT measurements and (ii) the effect of the studied transverse chest plane on ventilation distribution in different postures. Ten healthy adult subjects were studied in three postures on two separate days. EIT and spirometric data were obtained during tidal breathing and slow vital capacity (VC) manoeuvres. EIT data were acquired in two chest planes at 13 scans/s. Reproducibility of EIT findings was assessed by Bland-Altman analysis and Pearson correlation in 16 regions of interest in each plane. Regional ventilation distribution during tidal breathing and deep expiration was determined as fractional ventilation in four quadrants of the studied chest cross-sections. Our study showed a good reproducibility of EIT measurements repeated after an average time interval of 8 days. Global tidal volumes and VCs determined by spirometry on separate days were not significantly different. Regional ventilation in chest quadrants assessed by EIT was also unaffected. Posture exerted a significant effect on ventilation distribution among the chest quadrants during spontaneous breathing and deep expiration in both planes. The spatial distribution patterns in the two planes were not identical. We conclude that regional EIT ventilation findings are reproducible and recommend that the EIT examination location on the chest is carefully chosen especially during repeated measurements and follow-up.

Electrical Impedance Tomography in Acute Respiratory Distress Syndrome

Electrical impedance tomography (EIT) is an emerging new imaging modality not yet routinely used in a clinical setting. The generation of EIT scans is based on the non-invasive measurement of electrical properties of tissues which does not require the use of radiation. Thoracic EIT examinations have been shown to track changes in regional lung volumes at scan rates of up to 40-50 scans/s. Experimental and clinical studies indicate the potential of EIT in monitoring regional lung ventilation and aeration at the bedside. Mechanically ventilated patients with acute lung injury and acute respiratory distress syndrome (ARDS) might benefit from possible continuous monitoring of their regional lung function by EIT which could be used to optimise the ventilator settings and minimise the ventilator-induced lung injury. This review explains the measuring principle of EIT and the analysis of regional EIT signals which allow the assessment of regional lung ventilation, aeration and potentially also lung perfusion. Protective lung ventilation using low tidal volumes and adequate positive end-expiratory pressures, recruitment manoeuvres, surfactant administration, prone posture, restricted fluid administration, assisted ventilation allowing spontaneous breathing, partial liquid ventilation, administration of pulmonary vasoactive, anti-inflammatory and antioxidant agents are used or considered in the management of ARDS patients. EIT is capable of monitoring the pulmonary effects of many of these therapeutic procedures. This is documented by examples from experimental and clinical EIT studies and by references to relevant EIT literature. The perspectives and limitations of EIT monitoring are also addressed.