Electrical impedance tomography reveals pathophysiology of neonatal pneumothorax during NAVA

Electrical impedance tomography in neonates: a review

Appropriate interventions informed by real-time assessment of pulmonary function in mechanically ventilated critically ill neonates can reduce the incidence of bronchopulmonary dysplasia, pneumothorax, intraventricular hemorrhage and other complications of newborn life. The respiratory system in neonates is uniquely different from older children, and its physiological and anatomic attributes increase neonatal vulnerability to respiratory distress and eventual failure. While significant advancements have been made in developing respiratory support for neonates, such support is accompanied by inherent risks to their delicate lungs. Ventilator-associated lung injury poses a critical concern that can be potentially decreased with more precise, non-invasive, non-radiating, bedside methods for assessing neonatal pulmonary function in real time. Electrical impedance tomography (EIT) is one such tool, with immense potential for real-time pulmonary function monitoring in neonates. Still relatively new and in the earliest stages of clinical adoption, EIT use in neonatal critical care has been reported in several studies. This review discusses the basic features of EIT, its distinct advantages over traditional pulmonary function monitoring tools, the scope of its adoption in neonatal clinical practice, challenges associated with clinical adoption, and prospects for future applications. IMPACT: 1. Individualized care assisted by bedside pulmonary function monitoring can positively impact neonatal critical care and outcomes. 2. Electrical impedance tomography (EIT) has the potential to improve neonatal pulmonary function monitoring and treatment outcomes. 3. Electrical impedance tomography can be adopted as a part of routine neonatal respiratory critical care, especially in the population of patients most at risk for bronchopulmonary dysplasia and acute respiratory complications.

Technical Principles and Clinical Applications of Electrical Impedance Tomography in Pulmonary Monitoring

Pulmonary monitoring is crucial for the diagnosis and management of respiratory conditions, especially after the epidemic of coronavirus disease. Electrical impedance tomography (EIT) is an alternative non-radioactive tomographic imaging tool for monitoring pulmonary conditions. This review proffers the current EIT technical principles and applications on pulmonary monitoring, which gives a comprehensive summary of EIT applied on the chest and encourages its extensive usage to clinical physicians. The technical principles involving EIT instrumentations and image reconstruction algorithms are explained in detail, and the conditional selection is recommended based on clinical application scenarios. For applications, specifically, the monitoring of ventilation/perfusion (V/Q) is one of the most developed EIT applications. The matching correlation of V/Q could indicate many pulmonary diseases, e.g., the acute respiratory distress syndrome, pneumothorax, pulmonary embolism, and pulmonary edema. Several recently emerging applications like lung transplantation are also briefly introduced as supplementary applications that have potential and are about to be developed in the future. In addition, the limitations, disadvantages, and developing trends of EIT are discussed, indicating that EIT will still be in a long-term development stage before large-scale clinical applications.

Risk Factors for Pneumothorax and Its Association with Ventilation in Neonates

OBJECTIVE

The mode of ventilation that is implicated in pneumothorax is the one at the time of its diagnosis. Although there is evidence that air leak starts many hours before it is clinically evident, there are no prior studies that have investigated the association of pneumothorax with the mode of ventilation few hours before rather than at the time of its diagnosis.

STUDY DESIGN

A retrospective case-control study was conducted in the neonatal intensive care unit (NICU) between 2006 and 2016 where cases of neonates with pneumothorax were compared with gestational age-matched control neonates without pneumothorax. Respiratory support associated with pneumothorax was classified as the mode of ventilation 6 hours before the clinical diagnosis of pneumothorax. We investigated the factors that were different between cases and controls, and between cases of pneumothorax on bubble continuous positive airway pressure (bCPAP) and invasive mechanical ventilation (IMV).

RESULT

Of the 8,029 neonates admitted in the NICU during the study period, 223 (2.8%) developed pneumothorax. Among these, 127 occurred among 2,980 (4.3%) neonates on bCPAP, 38 among 809 (4.7%) neonates on IMV, and the remaining 58 among 4,240 (1.3%) neonates on room air. Those with pneumothorax were more likely to be male, have higher body weight, require respiratory support and surfactant administration, and have bronchopulmonary dysplasia (BPD). Among those who developed pneumothorax, there were differences in the gestational age, gender, and use of antenatal steroids between those who were on bCPAP as compared to those on IMV. IMV was associated with increased odds of pneumothorax as compared to those on bCPAP in a multivariable regression analysis. Cases on IMV had higher incidence of intraventricular hemorrhage, retinopathy of prematurity, BPD, and necrotizing enterocolitis, as well as longer length of stay as compared to those on bCPAP.

CONCLUSION

Neonates who require any respiratory support have higher incidence of pneumothorax. Among those on respiratory support, those on IMV had higher odds of pneumothorax and worse clinical outcomes as compared to those on bCPAP.

KEY POINTS

· The process of air leak leading to pneumothorax in majority of neonates starts much before it is clinically diagnosed.. · It is possible to detect the air leak early in the process by subtle changes in the signs, symptoms and changes in lung function.. · True association of the ventilation associated with pneumothorax is not at the time of diagnosis of pneumothorax but few hours before it is diagnosed.. · There is higher incidence of pneumothorax in neonates on any respiratory support.. · There is significantly higher incidence of pneumothorax among neonates on invasive ventilations as compared to noninvasive ventilation after correction for all other clinical factors..

Monitoring of spontaneous pneumothorax using electrical impedance tomography: A case report

Pneumothorax is an emergency in thoracic surgeries and respiratory medicine. A technique is warranted for real-time monitoring of pneumothorax at the bedside so that rapid diagnosis and timely intervention can be achieved. We report herein a case in which electrical impedance tomography (EIT) was employed at the bedside to monitor lung ventilation of a patient with spontaneous pneumothorax during treatment. It was found that the affected side/healthy side ventilation ratio and global inhomogeneity were strongly correlated with the severity of pneumothorax. The use of EIT allowed intuitive observation of the effect of pneumothorax on ventilation, which helped the doctors make immediate diagnosis and intervention. After timely and successful treatment, the patient was discharged. This is the first case reporting a complete therapeutic course of spontaneous pneumothorax assessed with EIT. Our case demonstrated that EIT could monitor regional ventilation loss of the affected side of pneumothorax patients at the bedside, and dynamically assess the treatment effect of pneumothorax, which provides an important imaging basis for clinical pneumothorax treatment.

Lung Imaging Acquisition with Electrical Impedance Tomography: Tackling Common Pitfalls

Electrical impedance tomography is a powerful tool for lung imaging that can be employed at the bedside in multiple clinical scenarios. Diagnosing and preventing interpretation pitfalls will ensure reliable data and allow for appropriate clinical decision-making.

A new method of ventilation inhomogeneity assessment based on a simulation study using clinical data on congenital diaphragmatic hernia cases

Congenital Diaphragmatic Hernia (CDH) is a diaphragm defect associated with lung hypoplasia and ventilation inhomogeneity (VI). The affected neonates are usually born with respiratory failure and require mechanical ventilation after birth. However, significant interindividual VI differences make ventilation difficult. So far, there are no clinical methods of VI assessment that could be applied to optimize ventilation at the bedside. A new VI index is a ratio of time constants T₁/T₂ of gas flows in both lungs. Pressure-controlled ventilation simulations were conducted using an infant hybrid (numerical-physical) respiratory simulator connected to a ventilator. The parameters of the respiratory system model and ventilator settings were based on retrospective clinical data taken from three neonates (2, 2.6, 3.6 kg) treated in the Paediatric Teaching Clinical Hospital of the Medical University of Warsaw. We searched for relationships between respiratory system impedance (Z) and ventilation parameters: work of breathing (WOB), peak inspiratory pressure (PIP), and mean airway pressure (MAP). The study showed the increased VI described by the T₁/T₂ index value highly correlated with elevated Z, WOB, PIP and MAP (0.8-0.9, the Spearman correlation coefficients were significant at P < 0.001). It indicates that the T₁/T₂ index may help to improve the ventilation therapy of CDH neonates.

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

PURPOSE

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).

METHODS

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_%.

RESULTS

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.

CONCLUSION

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.

Assessment of Postnatal Pulmonary Adaption in Bovine Neonates Using Electric Impedance Tomography (EIT)

Several aspects of postnatal pulmonary adaption in the bovine neonate remain unclear, particularly the dynamics and regional ventilation of the lungs. We used electric impedance tomography (EIT) to measure changes in ventilation in the first 3 weeks of life in 20 non-sedated neonatal calves born without difficulty in sternal recumbency. Arterial blood gas variables were determined in the first 24 h after birth. Immediately after birth, dorsal parts of the lungs had 4.53% ± 2.82% nondependent silent spaces (NSS), and ventral parts had 5.23% ± 2.66% dependent silent spaces (DSS). The latter increased in the first hour, presumably because of gravity-driven ventral movement of residual amniotic fluid. The remaining lung regions had good ventilation immediately after birth, and the percentage of lung regions with high ventilation increased significantly during the study period. The centre of ventilation was always dorsal to and on the right of the theoretical centre of ventilation. The right lung was responsible for a significantly larger proportion of ventilation (63.84% ± 12.74%, p < 0.00001) compared with the left lung. In the right lung, the centrodorsal lung area was the most ventilated, whereas, in the left lung, it was the centroventral area. Tidal impedance changes, serving as a surrogate for tidal volume, increased in the first 3 weeks of life (p < 0.00001). This study shows the dynamic changes in lung ventilation in the bovine neonate according to EIT measurements. The findings form a basis for the recognition of structural and functional lung disorders in neonatal calves.

Locating Functionalized Gold Nanoparticles Using Electrical Impedance Tomography

OBJECTIVE

An imaging device to locate functionalized nanoparticles, whereby therapeutic agents are transported from the site of administration specifically to diseased tissues, remains a challenge for pharmaceutical research. Here, we show a new method based on electrical impedance tomography (EIT) to provide images of the location of gold nanoparticles (GNPs) and the excitation of GNPs with radio frequencies (RF) to change impedance permitting an estimation of their location in cell models Methods: We have created an imaging system using quantum cluster GNPs as a contrast agent, activated with RF fields to heat the functionalized GNPs, which causes a change in impedance in the surrounding region. This change is then identified with EIT.

RESULTS

Images of impedance changes of around 804% are obtained for a sample of citrate stabilized GNPs in a solution of phosphate-buffered saline. A second quantification was carried out using colorectal cancer cells incubated with culture media, and the internalization of GNPs into the colorectal cancer cells was undertaken to compare them with the EIT images. When the cells were incubated with functionalized GNPs, the change was more apparent, approximately 402%. This change was reflected in the EIT image as the cell area was more clearly identifiable from the rest of the area.

SIGNIFICANCE

EIT can be used as a new method to locate functionalized GNPs in human cells and help in the development of GNP-based drugs in humans to improve their efficacy in the future.

Proportional assist and neurally adjusted ventilation: Clinical knowledge and future trials in newborn infants

Different types of patient triggered ventilator modes have become the mainstay of ventilation in term and preterm newborn infants. Maintaining spontaneous breathing has allowed for earlier weaning and the additive effects of respiratory efforts combined with pre-set mechanical inflations have reduced mean airway pressures, both of which are important components in trying to avoid lung injury and promote normal lung development. New sophisticated modes of assisted ventilation have been developed during the last decades where the control of ventilator support is turned over to the patient. The ventilator detects the respiratory effort and adjusts ventilatory assistance proportionally to each phase of the respiratory cycle, thus enabling the patient to have full control of the start, the duration and the amount of ventilatory assistance. In this paper we will review the literature on the ventilatory modes of proportional assist ventilation and neurally adjusted ventilatory assistance, examine the different ways the signals are analyzed, propose future studies, and suggest ways to apply these modes in the clinical environment.

Thoracic shape changes in newborns due to their position

The highly compliant nature of the neonatal chest wall is known to clinicians. However, its morphological changes have never been characterized and are especially important for a customised monitoring of respiratory diseases. Here, we show that a device applied on newborns can trace their chest boundary without the use of radiation. Such technology, which is easy to sanitise between patients, works like a smart measurement tape drawing also a digital cross section of the chest. We also show that in neonates the supine position generates a significantly different cross section compared to the lateral ones. Lastly, an unprecedented comparison between a premature neonate and a child is reported.