Electrical impedance tomography for titration of positive end-expiratory pressure in acute respiratory distress syndrome patients with chronic obstructive pulmonary disease

Regional lung function assessment using electrical impedance tomography in COPD, PRISm, and normal spirometry subjects: insights into early diagnostic potential

PURPOSE

This study utilizes electrical impedance tomography (EIT) to explore spatial-temporal heterogeneity in regional lung function among patients with chronic obstructive lung disease (COPD), preserved ratio impaired spirometry (PRISm), and those with normal lung function.

METHODS

Subjects who had pulmonary function test at Sir Run Run Shaw Hospital from 28 December 2023 to 30 March 2024 were screened. Regional lung functions were accessed with EIT regarding spatial distribution, abnormal area size, and expiratory time. The correlations between smoking index, SGRQ score, and EIT-related parameters were also evaluated.

RESULTS

A total of 194 patients were screened and 161 patients were included (56 COPD, 21 PRISm, and 84 normal). Spatial distribution of regional FEV1EIT (P < 0.001), FVCEIT (P = 0.025), FEV1/FVCEIT (P < 0.001), MMEFEIT (P = 0.012), T-75EIT (P < 0.001), and FIVCEIT (P = 0.020) showed significant differences among the three groups. The percentage of abnormal FEV1/FVCEIT areas detected via EIT was 83.40% (25-75% percentiles 52.29%-98.39%) in the COPD group, 25.46% (17.31%-41.31%) in the PRISm group, and 10.37% (3.34%-19.04%) in the normal group. The time constant map revealed that the patients with COPD exhibited the longest exhalation times. Elevated smoking index and SGRQ scores were associated with increased heterogeneity and larger areas of abnormal FEV1/FVCEIT.

CONCLUSION

Through EIT-based pulmonary function assessment, it is possible to sensitively identify the spatio-temporal heterogeneity in COPD and PRISm patients. Regional lung function impairments, particularly in PRISm patients with an FEV1/FVC ratio ≥ 0.7, were detected using EIT, highlighting its potential for early COPD diagnosis.

Electrical impedance tomography for PEEP titration in ARDS patients: a systematic review and meta-analysis

To assess the efficacy of electrical impedance tomography (EIT)-guided positive end-expiratory pressure (PEEP) titration in improving outcomes for patients with acute respiratory distress syndrome (ARDS). A systematic review and meta-analysis was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Randomized controlled trials and observational studies with a control group comparing EIT-guided PEEP titration to other strategies were included. Endpoints analysed included mortality, days of mechanical ventilation (MV), intensive care unit (ICU) length of stay (LOS), weaning success rate, barotrauma, driving pressure (∆P), mechanical power (MP), Sequential Organ Failure Assessment (SOFA) score and adverse events. Pooled results were presented as Risk Ratio (RR) for dichotomous outcomes and standardized difference in means (SMD) for continuous outcomes. A total of 4 studies were identified (3 randomized controlled trials and one observational study). All studies were single-center studies (N total = 271 patients). The main limitations were related to potential bias in selecting reported outcomes. EIT-guided PEEP titration was associated with a significant reduction in mortality among critically ill patients with ARDS (RR = 0.64, 95% CI: 0.45-0.91). No significant differences were found in other outcomes. Our findings suggest that EIT may be a valuable tool for PEEP titration in critically ill patients with ARDS. By optimizing lung mechanics, EIT-guided PEEP titration may potentially reduce mortality rates. While larger, multicenter studies are needed to definitively establish the clinical role of EIT in ARDS management, our results provide promising evidence for its potential clinical impact.

Electrical impedance tomography to set positive end-expiratory pressure

PURPOSE OF REVIEW

To summarize the rationale and concepts for positive end-expiratory pressure (PEEP) setting with electrical impedance tomography (EIT) and the effects of EIT-based PEEP setting on cardiopulmonary function.

RECENT FINDINGS

EIT allows patient-specific and regional assessment of PEEP effects on recruitability and overdistension, including its impact on ventilation-perfusion (V̇/Q) mismatch. The overdistension and collapse (OD-CL) method is the most used EIT-based approach for PEEP setting. In the RECRUIT study of 108 COVID-19 ARDS patients, the PEEP level corresponding to the OD-CL crossing point showed low overdistension and collapse (below 10% and 5%, respectively) regardless of recruitability. In a porcine model of acute respiratory distress syndrome (ARDS), it was shown that at this crossing point, respiratory mechanics (compliance, ΔP) were consistent, with adequate preload, lower right ventricular afterload, normal cardiac output, and sufficient gas exchange. A recent meta-analysis found that EIT based PEEP setting improved lung mechanics and potentially outcomes in ARDS patients. EIT thus provides critical insights beyond respiratory mechanics and oxygenation for individualized PEEP optimization. EIT-based methods for PEEP setting during assisted ventilation have also been proposed.

SUMMARY

EIT is a valuable technique to guide individualized PEEP setting utilizing cardiopulmonary information that is not captured by respiratory mechanics and oxygenation response alone.

Effects of sitting position on ventilation distribution determined by electrical impedance tomography in ventilated ARDS patients

OBJECTIVE

The study aimed to evaluate the improvements in pulmonary ventilation following a sitting position in ventilated ARDS patients using electrical impedance tomography.

METHODOLOGY

A total of 17 patients with ARDS under mechanical ventilation participated in this study, including 8 with moderate ARDS and 9 with severe ARDS. Each patient was initially placed in the supine position (S1), transitioned to sitting position (SP) for 30 min, and then returned to the supine position (S2). Patients were monitored for each period, with parameters recorded.

MAIN OUTCOME MEASURES

The primary outcome included the spatial distribution parameters of EIT, regional of interest (ROI), end-expiratory lung impedance (ΔEELI), and parameters of respiratory mechanics.

RESULTS

Compared to S1, the SP significantly altered the distribution in ROI1 (11.29 ± 4.70 vs 14.88 ± 5.00 %, p = 0.003) and ROI2 (35.59 ± 8.99 vs 44.65 ± 6.97 %, p ＜ 0.001), showing reductions, while ROI3 (39.71 ± 11.49 vs 33.06 ± 6.34 %, p = 0.009), ROI4 (13.35 ± 8.76 vs 7.24 ± 5.23 %, p ＜ 0.001), along with peak inspiratory pressure (29.24 ± 3.96 vs 27.71 ± 4.00 cmH2O, p = 0.036), showed increases. ΔEELI decreased significantly ventrally (168.3 (40.33 - 189.5), p ＜ 0.0001) and increased significantly dorsally (461.7 (297.5 - 683.7), p ＜ 0.0001). The PaO2/FiO2 ratio saw significant improvement in S2 compared to S1 after 30 min in the seated position (108 (73 - 130) vs 96 (57 - 129) mmHg, p = 0.03).

CONCLUSIONS

The sitting position is associated with enhanced compliance, improved oxygenation, and more homogenous ventilation in patients with ventilated ARDS compared to the supine position.

IMPLICATIONS FOR CLINICAL PRACTICE

It is important to know the impact of postural changes on patient pulmonary ventilation in order to standardize safe practices in critically ill patients. It may be helpful in the management among ventilated patients.

Subphenotypic features of patients with sepsis and ARDS: a multicenter cohort study

Objectives

Patients with sepsis are often comorbid with acute respiratory distress syndrome (ARDS), and the phenotypic characteristics of pulmonary and non-pulmonary infections leading to ARDS are still unclear. This study aimed to compare the phenotypic characteristics of ARDS resulting from pulmonary infections and other non-site infections and provide better guidance for clinical treatment.

Methods

We conducted a multicenter cohort analysis using data from the Tianjin Medical University General Hospital, Medical Information Mart for Intensive Care-IV (MIMIC-IV), and the electronic intensive care unit (eICU) databases. The study population consisted of adult patients diagnosed with sepsis and ARDS. The primary objectives were to compare the characteristics and outcomes of patients with pulmonary infection-induced ARDS and those with non-pulmonary infection-induced ARDS using Wilcoxon analysis, Kaplan-Meier curves, correlation analysis, propensity matching scores, and other statistical methods.

Results

Patients with ARDS by pulmonary infection may be more likely to have a history of chronic obstructive pulmonary disease, and abdominal infection was more likely to induce ARDS in sepsis patients with non-pulmonary infection. Pulmonary infections caused by Klebsiella pneumoniae and Acinetobacter baumannii were more likely to induce ARDS. The oxygenation index and prognosis of ARDS patients induced by pulmonary infection were worse than those caused by other infections, with lower PaO2, PaO2/FiO2, and ROX index and longer hospital stay. More ARDS patients with pulmonary infection were given mechanical ventilation therapy, with higher mortality, APACHE II, SOFA, and SAPS II. The further correlation analysis showed that the prognostic scores of ARDS patients were negatively correlated with PaO2/FiO2 and ROX index. The above results were confirmed to varying degrees by propensity matching scores, external cohort validation, and other methods.

Conclusion

Pulmonary infection induces a worse prognosis of ARDS than other site infections in patients with sepsis and ARDS. These patients require heightened vigilance, early intervention, and possibly more aggressive management strategies.

Is EIT-guided positive end-expiratory pressure titration for optimizing PEEP in ARDS the white elephant in the room? A systematic review with meta-analysis and trial sequential analysis

Electrical Impedance Tomography (EIT) is a novel real-time lung imaging technology for personalized ventilation adjustments, indicating promising results in animals and humans. The present study aimed to assess its clinical utility for improved ventilation and oxygenation compared to traditional protocols. Comprehensive electronic database screening was done until 30th November, 2023. Randomized controlled trials, controlled clinical trials, comparative cohort studies, and assessments of EIT-guided PEEP titration and conventional methods in adult ARDS patients regarding outcome, ventilatory parameters, and P/F ratio were included. Our search retrieved five controlled cohort studies and two RCTs with 515 patients and overall reduced risk of mortality [RR = 0.68; 95% CI: 0.49 to 0.95; I2 = 0%], better dynamic compliance [MD = 3.46; 95% CI: 1.59 to 5.34; I2 = 0%] with no significant difference in PaO2/FiO2 ratio [MD = 6.5; 95%CI -13.86 to 26.76; I2 = 74%]. The required information size except PaO2/FiO2 was achieved for a power of 95% based on the 50% reduction in risk of mortality, 10% improved compliance as the cumulative Z-score of the said outcomes crossed the alpha spending boundary and did not dip below the inner wedge of futility. EIT-guided individualized PEEP titration is a novel modality; further well-designed studies are needed to substantiate its utility.

Chronic obstructive pulmonary disease affects outcome in surgical patients with perioperative organ injury: a retrospective cohort study in Germany

BACKGROUND

The impact of chronic obstructive pulmonary disease (COPD) on outcome in perioperative organ injury (POI) has not yet been investigated sufficiently.

METHODS

This retrospective cohort study analysed data of surgical patients with POI, namely delirium, stroke, acute myocardial infarction, acute respiratory distress syndrome, acute liver injury (ALI), or acute kidney injury (AKI), in Germany between 2015 and 2019. We compared in-hospital mortality, hospital length of stay (HLOS) and perioperative ventilation time (VT) in patients with and without COPD.

RESULTS

We analysed the data of 1,642,377 surgical cases with POI of which 10.8% suffered from COPD. In-hospital mortality was higher (20.6% vs. 15.8%, p < 0.001) and HLOS (21 days (IQR, 12-34) vs. 16 days (IQR, 10-28), p < 0.001) and VT (199 h (IQR, 43-547) vs. 125 h (IQR, 32-379), p < 0.001) were longer in COPD patients. Within the POI examined, AKI was the most common POI (57.8%), whereas ALI was associated with the highest mortality (54.2%). Regression analysis revealed that COPD was associated with a slightly higher risk of in-hospital mortality (OR, 1.19; 95% CI:1.18-1.21) in patients with any POI.

CONCLUSIONS

COPD in patients with POI is associated with higher mortality, longer HLOS and longer VT. Especially patients suffering from ALI are susceptible to the detrimental effects of COPD on adverse outcome.

Electrical impedance tomography-guided positive end-expiratory pressure titration in ARDS: a systematic review and meta-analysis

PURPOSE

Assessing efficacy of electrical impedance tomography (EIT) in optimizing positive end-expiratory pressure (PEEP) for acute respiratory distress syndrome (ARDS) patients to enhance respiratory system mechanics and prevent ventilator-induced lung injury (VILI), compared to traditional methods.

METHODS

We carried out a systematic review and meta-analysis, spanning literature from January 2012 to May 2023, sourced from Scopus, PubMed, MEDLINE (Ovid), Cochrane, and LILACS, evaluated EIT-guided PEEP strategies in ARDS versus conventional methods. Thirteen studies (3 randomized, 10 non-randomized) involving 623 ARDS patients were analyzed using random-effects models for primary outcomes (respiratory mechanics and mechanical power) and secondary outcomes (PaO2/FiO2 ratio, mortality, stays in intensive care unit (ICU), ventilator-free days).

RESULTS

EIT-guided PEEP significantly improved lung compliance (n = 941 cases, mean difference (MD) = 4.33, 95% confidence interval (CI) [2.94, 5.71]), reduced mechanical power (n = 148, MD = - 1.99, 95% CI [- 3.51, - 0.47]), and lowered driving pressure (n = 903, MD = - 1.20, 95% CI [- 2.33, - 0.07]) compared to traditional methods. Sensitivity analysis showed consistent positive effect of EIT-guided PEEP on lung compliance in randomized clinical trials vs. non-randomized studies pooled (MD) = 2.43 (95% CI - 0.39 to 5.26), indicating a trend towards improvement. A reduction in mortality rate (259 patients, relative risk (RR) = 0.64, 95% CI [0.45, 0.91]) was associated with modest improvements in compliance and driving pressure in three studies.

CONCLUSIONS

EIT facilitates real-time, individualized PEEP adjustments, improving respiratory system mechanics. Integration of EIT as a guiding tool in mechanical ventilation holds potential benefits in preventing ventilator-induced lung injury. Larger-scale studies are essential to validate and optimize EIT's clinical utility in ARDS management.

Exploring alveolar recruitability using positive end-expiratory pressure in mice overexpressing TGF-β1: a structure-function analysis

Pre-injured lungs are prone to injury progression in response to mechanical ventilation. Heterogeneous ventilation due to (micro)atelectases imparts injurious strains on open alveoli (known as volutrauma). Hence, recruitment of (micro)atelectases by positive end-expiratory pressure (PEEP) is necessary to interrupt this vicious circle of injury but needs to be balanced against acinar overdistension. In this study, the lung-protective potential of alveolar recruitment was investigated and balanced against overdistension in pre-injured lungs. Mice, treated with empty vector (AdCl) or adenoviral active TGF-β1 (AdTGF-β1) were subjected to lung mechanical measurements during descending PEEP ventilation from 12 to 0 cmH2O. At each PEEP level, recruitability tests consisting of two recruitment maneuvers followed by repetitive forced oscillation perturbations to determine tissue elastance (H) and damping (G) were performed. Finally, lungs were fixed by vascular perfusion at end-expiratory airway opening pressures (Pao) of 20, 10, 5 and 2 cmH2O after a recruitment maneuver, and processed for design-based stereology to quantify derecruitment and distension. H and G were significantly elevated in AdTGF-β1 compared to AdCl across PEEP levels. H was minimized at PEEP = 5-8 cmH2O and increased at lower and higher PEEP in both groups. These findings correlated with increasing septal wall folding (= derecruitment) and reduced density of alveolar number and surface area (= distension), respectively. In AdTGF-β1 exposed mice, 27% of alveoli remained derecruited at Pao = 20 cmH2O. A further decrease in Pao down to 2 cmH2O showed derecruitment of an additional 1.1 million alveoli (48%), which was linked with an increase in alveolar size heterogeneity at Pao = 2-5 cmH2O. In AdCl, decreased Pao resulted in septal folding with virtually no alveolar collapse. In essence, in healthy mice alveoli do not derecruit at low PEEP ventilation. The potential of alveolar recruitability in AdTGF-β1 exposed mice is high. H is optimized at PEEP 5-8 cmH2O. Lower PEEP folds and larger PEEP stretches septa which results in higher H and is more pronounced in AdTGF-β1 than in AdCl. The increased alveolar size heterogeneity at Pao = 5 cmH2O argues for the use of PEEP = 8 cmH2O for lung protective mechanical ventilation in this animal model.

Setting positive end-expiratory pressure by using electrical impedance tomography

PURPOSE OF REVIEW

This review presents the principles and possibilities of setting positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT). It summarizes the major findings of recent studies where EIT was applied to monitor the effects of PEEP on regional lung function and to guide the selection of individualized PEEP setting.

RECENT FINDINGS

The most frequent approach of utilizing EIT for the assessment of PEEP effects and the PEEP setting during the time period from January 2022 till June 2023 was based on the analysis of pixel tidal impedance variation, typically acquired during stepwise incremental and/or decremental PEEP variation. The most common EIT parameters were the fraction of ventilation in various regions of interest, global inhomogeneity index, center of ventilation, silent spaces, and regional compliance of the respiratory system. The studies focused mainly on the spatial and less on the temporal distribution of ventilation. Contrast-enhanced EIT was applied in a few studies for the estimation of ventilation/perfusion matching.

SUMMARY

The availability of commercial EIT devices resulted in an increase in clinical studies using this bedside imaging technology in neonatal, pediatric and adult critically ill patients. The clinical interest in EIT became evident but the potential of this method in clinical decision-making still needs to be fully exploited.

Epidemiology, Ventilation Management and Outcomes of COPD Patients Receiving Invasive Ventilation for COVID-19-Insights from PRoVENT-COVID

Chronic obstructive pulmonary disease (COPD) is a risk factor for death in patients admitted to intensive care units (ICUs) for respiratory support. Previous reports suggested higher mortality in COPD patients with COVID-19. It is yet unknown whether patients with COPD were treated differently compared to non-COPD patients. We compared the ventilation management and outcomes of invasive ventilation for COVID-19 in COPD patients versus non-COPD patients. This was a post hoc analysis of a nation-wide, observational study in the Netherlands. COPD patients were compared to non-COPD patients with respect to key ventilation parameters. The secondary endpoints included adjunctive treatments for refractory hypoxemia, and 28-day mortality. Of a total of 1090 patients, 88 (8.1%) were classified as having COPD. The ventilation parameters were not different between COPD patients and non-COPD patients, except for FiO2, which was higher in COPD patients. Prone positioning was applied more often in COPD patients. COPD patients had higher 28-day mortality than non-COPD patients. COPD had an independent association with 28-day mortality. In this cohort of patients who received invasive ventilation for COVID-19, only FiO2 settings and the use of prone positioning were different between COPD patients and non-COPD patients. COPD patients had higher mortality than non-COPD patients.

Benefits of secretion clearance with high frequency percussive ventilation in tracheostomized critically ill patients: a pilot study

Clearance of secretions remains a challenge in ventilated patients. Despite high-frequency percussive ventilation (HFPV) showing benefits in patients with cystic fibrosis and neuromuscular disorders, very little is known about its effects on other patient categories. Therefore, we designed a physiological pilot study investigating the effects on lung aeration and gas exchange of short HFPV cycles in tracheostomized patients undergoing mechanical ventilation. Electrical impedance tomography (EIT) was recorded at baseline (T0) by a belt wrapped around the patient's chest, followed by the HFPV cycle lasting 10 min. EIT data was collected again after the HFPV cycle (T1) as well as after 1 h (T2) and 3 h (T3) from T0. Variation from baseline of end-expiratory lung impedance (∆EELI), tidal variation (TIV) and global inhomogeneity index (GI) were computed. Arterial blood was also taken for gas analysis. HFPV cycle significantly improved the ∆EELI at T1, T2 and T3 when compared to baseline (p < 0.05 for all comparisons). The ratio between arterial partial pressure and inspired fraction of oxygen (PaO₂/FiO₂) also increased after the treatment (p < 0.001 for all comparison) whereas TIV (p = 0.132) and GI (p = 0.114) remained unchanged. Short cycles of HFPV superimposed to mechanical ventilation promoted alveolar recruitment, as suggested by improved ∆EELI, and improved oxygenation in tracheostomized patients with high load of secretion.Trial Registration Prospectively registered on www.clinicaltrials.gov (NCT05200507; dated 6th January 2022).