Structural priors represented by discrete cosine transform improve EIT functional imaging

Structural prior information can improve electrical impedance tomography (EIT) reconstruction. In this contribution, we introduce a discrete cosine transformation-based (DCT-based) EIT reconstruction algorithm to demonstrate a way to incorporate the structural prior with the EIT reconstruction process. Structural prior information is obtained from other available imaging methods, e.g., thorax-CT. The DCT-based approach creates a functional EIT image of regional lung ventilation while preserving the introduced structural information. This leads to an easier interpretation in clinical settings while maintaining the advantages of EIT in terms of bedside monitoring during mechanical ventilation. Structural priors introduced in the DCT-based approach are of two categories in terms of different levels of information included: a contour prior only differentiates lung and non-lung region, while a detail prior includes information, such as atelectasis, within the lung area. To demonstrate the increased interpretability of the EIT image through structural prior in the DCT-based approach, the DCT-based reconstructions were compared with reconstructions from a widely applied one-step Gauss-Newton solver with background prior and from the advanced GREIT algorithm. The comparisons were conducted both on simulation data and retrospective patient data. In the simulation, we used two sets of forward models to simulate different lung conditions. A contour prior and a detail prior were derived from simulation ground truth. With these two structural priors, the reconstructions from the DCT-based approach were compared with the reconstructions from both the one-step Gauss-Newton solver and the GREIT. The difference between the reconstructions and the simulation ground truth is calculated by the ℓ2-norm image difference. In retrospective patient data analysis, datasets from six lung disease patients were included. For each patient, a detail prior was derived from the patient's CT, respectively. The detail prior was used for the reconstructions using the DCT-based approach, which was compared with the reconstructions from the GREIT. The reconstructions from the DCT-based approach are more comprehensive and interpretable in terms of preserving the structure specified by the priors, both in simulation and retrospective patient data analysis. In simulation analysis, the ℓ2-norm image difference of the DCT-based approach with a contour prior decreased on average by 34% from GREIT and 49% from the Gauss-Newton solver with background prior; for reconstructions of the DCT-based approach with detail prior, on average the ℓ2-norm image difference is 53% less than GREIT and 63% less than the reconstruction with background prior. In retrospective patient data analysis, the reconstructions from both the DCT-based approach and GREIT can indicate the current patient status, but the DCT-based approach yields more interpretable results. However, it is worth noting that the preserved structure in the DCT-based approach is derived from another imaging method, not from the EIT measurement. If the structural prior is outdated or wrong, the result might be misleadingly interpreted, which induces false clinical conclusions. Further research in terms of evaluating the validity of the structural prior and detecting the outdated prior is necessary.

Differentiating Phenotypes of Coronavirus Disease-2019 Pneumonia by Electric Impedance Tomography

Introduction

Coronavirus disease-2019 (COVID-19) pneumonia has different phenotypes. Selecting the patient individualized and optimal respirator settings for the ventilated patient is a challenging process. Electric impedance tomography (EIT) is a real-time, radiation-free functional imaging technique that can aid clinicians in differentiating the “low” (L-) and “high” (H-) phenotypes of COVID-19 pneumonia described previously.

Methods

Two patients (“A” and “B”) underwent a stepwise positive end-expiratory pressure (PEEP) recruitment by 3 cmH₂O of steps from PEEP 10 to 25 and back to 10 cmH₂O during a pressure control ventilation of 15 cmH₂O. Recruitment maneuvers were performed under continuous EIT recording on a daily basis until patients required controlled ventilation mode.

Results

Patients “A” and “B” had a 7- and 12-day long trial, respectively. At the daily baseline, patient “A” had significantly higher compliance: mean ± SD = 53 ± 7 vs. 38 ± 5 ml/cmH₂O (p < 0.001) and a significantly higher physiological dead space according to the Bohr–Enghoff equation than patient “B”: mean ± SD = 52 ± 4 vs. 45 ± 6% (p = 0.018). Following recruitment maneuvers, patient “A” had a significantly higher cumulative collapse ratio detected by EIT than patient “B”: mean ± SD = 0.40 ± 0.08 vs. 0.29 ± 0.08 (p = 0.007). In patient “A,” there was a significant linear regression between the cumulative collapse ratios at the end of the recruitment maneuvers (R² = 0.824, p = 0.005) by moving forward in days, while not for patient “B” (R² = 0.329, p = 0.5).

Conclusion

Patient “B” was recognized as H-phenotype with high elastance, low compliance, higher recruitability, and low ventilation-to-perfusion ratio; meanwhile patient “A” was identified as the L-phenotype with low elastance, high compliance, and lower recruitability. Observation by EIT was not just able to differentiate the two phenotypes, but it also could follow the transition from L- to H-type within patient “A.”

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: NCT04360837.

Detection of Different COVID-19 Pneumonia Phenotypes with Estimated Alveolar Collapse and Overdistention by Bedside Electrical Impedance Tomography

COVID-19 induced acute respiratory distress syndrome (ARDS) could have two different phenotypes, which was reported to have different response and outcome to the typical ARDS positive end-expiration pressure (PEEP) treatment. The identification of the different phenotypes in terms of the recruitability can help improve the patient outcome. In this contribution we conducted alveolar overdistention and collapse analysis with the long term electrical impedance tomography monitoring data on two severe COVID-19 pneumonia patients. The result showed different patient reactions to the PEEP trial, revealed the progressive change in the patient status, and indicted a possible phenotype transition in one patient. It might suggest that EIT can be a practical tool to identify phenotypes and to provide progressive information of COVID-19 pneumonia.

Extracorporeal membrane oxygenation in intensive care unit

Összefoglaló. Az extracorporalis membránoxigenizációt egyre gyakrabban alkalmazzák világszerte refrakter légzési és/vagy keringési elégtelenség kezelésében. Intézetünkben 2015-ben kezdtük meg a program előkészítését és felépítését. Célunk az extracorporalis membránoxigenizációs kezelés élettani alapjainak rövid ismertetése, különös tekintettel a venovenosus konfigurációra, és az eddig kezelt eseteink eredményeinek összefoglalása. Az irodalom szisztematikus áttekintése és a kezelt esetek adatainak retrospektív értékelése voltak a módszereink. 2016 óta összesen 14 beteg esetében használtunk extracorporalis membránoxigenizációt (8 férfi, 6 nő, életkor 51 ± 15 év, APACHE II. score 24 ± 7). Az indikáció 9 esetben súlyos refrakter hypoxaemiás légzési elégtelenség, 1 esetben tracheooesophagealis fistula és légzési elégtelenség, 1 esetben műtét alatti támogatás tervezett trachearekonstrukció során és 3 beteg esetében refrakter cardiogen shock volt. Az extracorporalis membránoxigenizáció 11 betegben a légzés, 3 betegben a keringés támogatását szolgálta, 13 venovenosus, 1 venoarteriosus konfigurációban. Az extracorporalis támogatás ideje légzéstámogatás esetében 14 ± 6 nap, a cardialis támogatások esetében 5 ± 4 nap volt. Az intenzív osztályos ápolási idő 27 ± 13, illetve 21 ± 17 nap volt a két betegcsoportban. 9 beteget jó funkcionális állapotban bocsátottunk el, 5 beteg halt meg osztályunkon, további 3 később a kórházi bennfekvés során. Az extracorporalis membránoxigenizációs program regionális centrumokban Magyarországon is megvalósítható. A nemzetközi ajánlások, oktatási módszerek alkalmazásával a nemzetközi irodalomban közölt túlélési eredményekhez hasonló eredmények érhetők el hazánkban is. Orv Hetil. 2021; 162(11): 425-431. Summary. Extracorporeal membrane oxygenisation is commonly used worldwide for refractory respiratory and circulatory failure. We started to organise the introduction of this therapeutic modality in 2015. Our aim is to give a short review about extracorporeal life support, especially veno-venous extracorporeal membrane oxygenation, and to present our first results. We provide a systematic review of the currently available literature and a summary of our first treatments. As of 2016, we supported 14 patients with extracorporeal membrane oxygenisation (8 men, age 51 ± 15 years, APACHE II score 24 ± 7). The indications were refractory hypoxaemic respiratory failure in 9, tracheo-oesophageal fistula and respiratory failure in 1, support during surgery for planned tracheal reconstruction in 1, and refractory cardiogenic shock in 3 patients. We provided respiratory support in 11, circulatory support in 3 cases, with 13 veno-venous and 1 veno-arterial configuration. The support lasted for 14 ± 6 days in respiratory, and for 5 ± 4 days in cardiac cases. Intensive care length of stay was 27 ± 13 and 21 ± 17 days in the two patient groups. We discharged 9 patients in good functional state, 5 patients died during intensive care and further 3 later, during the hospital stay. Our results show that the implementation of an extracoporeal membrane oxygenation program is feasible in Hungarian tertiary centers. In line with international recommendations and adapting international training courses, the survival is very similar to that reported in the literature. Orv Hetil. 2021; 162(11): 425-431.

EIT based intrathoracic pulsatile impedance measurements during apnea: a case study

Intrathoracic ventilation related and pulsatile (perfusion) impedance changes can be measured by the noninvasive and radiation-free imaging method Electrical Impedance Tomography (EIT). Ventilation monitoring is still the key research area in EIT, whereby perfusion monitoring gain more and more in interest. However, there are still many unknown influencing factors concerning pulsatile impedance measurements which have to be investigated. Hence, in this observational case study the impact of prolonged apnea periods on pulsatile impedance changes was examined in a patient with suspected brain death undergoing several apnea tests. In addition, the correlation between changes in pulsatile impedance and certain blood gas parameters (carbon dioxide partial pressure, pCO2; oxygen partial pressure, pO2; pH; bicarbonate, HCO3 -) were explored. Results show that the pulsatile impedance signal changes over time during apnea. An increase in the area under the curve (Mean AuC) and the maximum amplitude (Mean Max) of heart beat associated impedance signals was observed (Mean AuC: up to 65 %; Mean Max: up to 57 %). Furthermore, a positive correlation between the increase in impedance and pCO2and HCO3 - was assessed (both: up to 0.99), whereas pO2and pH show a negative correlation (both: up to -0.99). These preliminary results indicate that pulsatile EIT monitoring may be applied to get additional information regarding cardio-pulmonary interactions sustaining diagnosis or treatment of lung diseases.

Importance of the imaging techniques in the management of COVID-19-infected patients

Critical-care physicians are facing a challenging process in healthcare due to the overwhelming case number of hypoxic respiratory failure patients. Pneumonia has an utmost importance in the primary pathomechanism of the development of critical illness in the COVID-19 patients. Thus, imaging techniques are situated in the frontline to aim the diagnostic decision-making, to follow up the progress and to evaluate the possible complications. Reviewing the available literature, so far the common chest CT, chest X-ray and chest wall ultrasound features are presented, and recommendations are pronounced for the indications of the different modalities. At the initial phase, the atypical presentations of the virus infection are multiplex, peripheral ground glass opacities situated in the right lower lobe of the lung evolving rapidly into a bilateral involvement of the middle and basal zones. Along with the progression, the ratio of the consolidation is increasing subsequently deteriorating into fibrosis with reticular pattern. Chest ultrasound performed at the bedside has a paramount importance to reduce the possible number of health-care worker contacts in consequence of the strict and special infection control orders established on account of the SARS-CoV-2 pandemia. Orv Hetil. 2020; 161(17): 672–677.

Diagnostic consideration and bedside estimation of the prognosis in COVID-19 patients

In December 2019, a cluster of pneumonia cases of unknown origin occured in Wuhan, China. The identified infective agent is a novel corona virus called “severe acute respiratory syndrome coronavirus 2” (SARS-CoV-2) and the respiratory disease caused by this agent aquired the name “coronavirus disease 2019” (COVID-19). In March 2020, the World Health Organization (WHO) declared the novel coronavirus outbreak a pandemic. We reviewed the international literature regarding the novel coronavirus outbreak. Here below, we focus mainly on the diagnostic issues of COVID-19 and on the estimation of the prognosis. We detail the relevant anamnestic factors and initial examination results which serve as basics for the clinical suspicion of COVID-19. We also focus on the proper method of microbiological sampling and the relevant informations regarding diagnostic tests like the gold standard real-time reverse transcriptase polymerase chain reaction (RT-PCR) for SARS-CoV-2. We also cite the current national epidemiologic regulations of testing for novel coronavirus. In the last section, we emphasize the importance and the potential way of early identification of high-risk patients. The COVID-19 pandemic may cause substantial epidemiological and healthcare burden even in Hungary. In addition to the epidemiologic interventions aiming the deceleration of the outbreak, the early identification and the correct hospital treatment remain key issues since these may influence mortality. The chances of the critically ill patients could be improved solely by a high-quality and careful critical care. It is prudent to meet the experiences of colleagues working hard with these patients in the already heavily infected countries. Orv Hetil. 2020; 161(17): 667–671.

Lung recruitment can improve oxygenation in patients ventilated in continuous positive airway pressure/pressure support mode

Background

Recruitment maneuvers are often used in critical care patients with hypoxemic respiratory failure. Although continuous positive airway pressure/pressure support (CPAP/PS) ventilation is a frequently used approach, but whether lung recruitment also improves oxygenation in spontaneously breathing patients has not been investigated yet. The primary objective was to analyze the effect of recruitment maneuver on oxygenation in patients ventilated in CPAP/PS mode.

Methods

Following baseline measurements PEEP was increased by 5 cmH₂O. Recruitment maneuver was applied for 40 s with 40 cmH₂O of PS. Measurements of the difference in PaO₂/FiO₂ and airway parameters measured by the ventilator were recorded immediately after recruitment then 15 and 30 min later. Thirty patients ventilated in CPAP/PS mode with a PEEP ≥5 cmH₂O were enrolled in this prospective, observational study if their PaO₂/FiO₂ ratio was <300 mmHg or required an FiO₂ >0.5.

Results

Following recruitment maneuver patients were considered as non-responders (NR, n = 15) if difference of PaO₂/FiO₂ <20% and responders (R, n = 15) if difference of PaO₂/FiO₂ ≥20%. In the NR-group, PaO₂/FiO₂ decreased non-significantly from baseline: median [interquartile], PaO₂/FiO₂ = 176 [120–186] vs. after recruitment: 169 [121–182] mmHg, P = 0.307 while in the R-group there was significant improvement: 139 [117–164] vs. 230 [211–323] mmHg, P = 0.01. At the same time points, dead space to tidal volume ratio (Vds/Vte) significantly increased in the NR-group Vds/Vte = 32 [27–37] vs. 36 [25–42]%, P = 0.013 but no significant change was observed in the R-group: 26 [22–34] vs. 27 [24–33]%, P = 0.386.

Conclusion

Recruitment maneuver improved PaO₂/FiO₂ ratio by ≥20% in 50% of patients ventilated in CPAP/PS mode.

T-piece improves arterial and central venous oxygenation in trachestomized patients as compared to continuous positive airway pressure/pressure support ventilation

BACKGROUND

T-piece has been widely used as T-piece trial to identify patients who are ready for extubation but it is seldom used as a weaning tool. Our objective was to investigate the effects of breathing via T-piece on gas exchange as compared to continuous positive airway pressure with pressure support (CPAP+PS) and CPAP with automatic tube compensation (CPAP+ATC) as it has not been evaluated yet.

METHODS

Tracheostomized, "ready to be weaned" critically ill patients were enrolled in this prospective, auto-control clinical trial. Arterial oxygen tension (PaO2) was determined on CPAP+PS (t0), 15 minutes later on CPAP+ATC (t1), then on T-piece at 15, 30 and 60 minutes (t2-4). ScvO2 was measured at t0 and t4. Settings of fraction of inspired oxygen (FiO2) and positive end-expiratory pressure (PEEP) were kept constant throughout the investigation.

RESULTS

Twenty-five patients were enrolled. T-piece trial was interrupted in 4 cases after t2, due to pulmonary oedema, hypertension or fatigue. PaO2/FiO2 was significantly higher on T-piece (t3,4) then on CPAP (t0,1), P<0.05, PaO2/FiO2 did not change significantly on CPAP+PS (t0) vs. CPAP+ATC (t1) modes: median=208 (interquartile range: 175-266) vs. 223 (186-290) mmHg, P=0.102, but significantly increased from t0-t4: 208 (175-266) vs. 249 (215-325) mmHg, P=0.003, respectively. ScvO2 was significantly higher on T-piece at t4: 80% (75-82%) than on CPAP+PS at t0: 73% (71-78%), P<0.001.

CONCLUSION

On the same FiO2 and PEEP setting, breathing via T-piece improved oxygenation and resulted in increased ScvO2 as compared to breathing on CPAP with PS. Our observations suggest a potential role of T-piece during weaning from mechanical ventilation.

Tissue-specific signal(s) activate the promoter of a metallocarboxypeptidase inhibitor gene family in potato tuber and berry

The molecular basis of the differential expression of the GM7-type metallocarboxypeptidase inhibitor (MCPI) genes in tuberizing (StMCPI) and non-tuberizing Solanum species (SbMCPI) was investigated. It was shown that the StMCPI is encoded by a gene family in Solanum tuberosum (potato), but SbMCPI might be a single-copy gene in the non-tuberizing species Solanum brevidens. The StMCPI promoter shows evolutionary relatedness to the S. brevidens-derived SbMCPI and to the fruit-specific tomato promoter 2A11. Both StMCPI and SbMCPI promoter regions were able to confer tuber- and berry-specific expression for the beta-glucuronidase reporter gene in potato suggesting that the difference in MCPI gene expression is in trans regulatory factors between the tuberizing and the non-tuberizing Solanum species. The MCPI promoters did not respond to metabolic, environmental or hormonal signals in leaves. Thus, the MCPI genes are regulated in a different way than the other known tuber-specific genes and potentially are suitable for biotechnological application in potato to provide specific transgene expression in tuber and berry.