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Background. Diagnosing and discriminating non-cardiogenic interstitial syndrome (NCIS) and cardiogenic pulmonary edema (CPE) is notoriously difficult in a mixed intensive care unit (ICU) population. We hypothesized that a comprehensive lung ultrasound exam can be used to accurately diagnose interstitial syndrome and can discriminate between NCIS and CPE.Methods. A single center prospective diagnostic accuracy study was used as derivation cohort and a post-hoc analysis of a multi-center prospective observational study as validation cohort. Consecutive adult ICU patients that received a lung ultrasound examination for clinical or study purposes were included. The reference standard was the diagnosis interstitial syndrome (NCIS or CPE) or non-interstitial syndromes (other pulmonary diagnoses and no pulmonary diagnoses) at the moment of examination based on full post-hoc clinical chart review except lung ultrasound. The index test was a comprehensive lung ultrasound examination performed and scored by a researcher blinded to clinical information.Results. 101 patients were included in the derivation and 125 in validation cohort. In the derivation cohort, patients with interstitial syndrome (n=56) were reliably discriminated from other patients based on the presence of a B-pattern (defined as ≥3 B-lines in one frame) with an accuracy of 94.7% (sens 90.9%, spec 91.1%), while specificity was higher for a bilateral B-pattern (accuracy 86.0%; sens 74.5%, spec 100%). For the discrimination of NCIS (n=29) from CPE (n=27), the presence of bilateral pleural line abnormalities had the highest diagnostic accuracy (94.6%; sens 89.3%, spec 100%) followed by consolidation (76.8%; sens 69.0%, spec 85.2%) and subtle lung sliding (67.9%; sens 62.1%, spec 74.1%). A diagnostic algorithm (BLUISH protocol) using B-pattern and bilateral pleural abnormalities had an accuracy of 0.86 (95%CI 0.77-0.95) for diagnosis and discrimination of interstitial syndromes. In the validation cohort, which included 125 patients with interstitial syndrome, pleural line abnormalities discriminated NCIS (n=101) from CPE (n=24) with a sensitivity of 30% (95%CI 21-40%) and a specificity of 100% (95%CI: 86-100%). Conclusions. Lung ultrasound can be used to diagnose and discriminate interstitial syndromes in ICU patients with moderate to good accuracy. Pleural line abnormalities are highly specific for NCIS, but sensitivity is limited.

RationaleThe concentration of octane and acetaldehyde in exhaled breath has good diagnostic accuracy for Acute Respiratory Distress Syndrome (ARDS). We aimed to determine whether breath octane and acetaldehyde are able to distinguish the presence and absence of ARDS in critically ill patients suspected to have ventilator-associated pneumonia (VAP).MethodsThis is a secondary analysis of a prospective observational study into exhaled breath analysis using gas-chromatography-time of flight-mass spectrometry. Difference in the relative abundance of octane and acetaldehyde in exhaled breath was compared between patients with and without ARDS using the Mann-Whitney U-test and the association was quantified using logistic regression. The discriminative accuracy of octane and acetaldehyde, alone or in combination, was calculated using the area under the curve of the ROC (AUROCC).ResultsWe included 98 patients of whom 32 had ARDS and 66 did not. The area under the acetaldehyde peak was higher in patients with ARDS (p=0.03), and associated with the presence of ARDS (OR: 1.06 per 100000 count change (95% CI: 1.02–1.13), p=0.01). A combined model with octane and acetaldehyde showed a high specificity and low sensitivity (respectively, 90% and 40.6%), with a low accuracy (AUROCC: 0.65, 95% CI: 0.53–0.78).ConclusionPatients suspected to have VAP with ARDS had a higher acetaldehyde concentration in exhaled breath than patients suspected to have VAP without ARDS. However, in this patient population, discrimination of these breath biomarkers for ARDS was poor, indicating the difficulty of translating diagnostic tests between clinical settings.

Introduction: The Radiographic Assessment of Lung Edema (RALE) score provides a semi-quantitative measure of pulmonary edema. In patients with acute respiratory distress syndrome (ARDS), the RALE score is associated with mortality. In mechanically ventilated patients in the intensive care unit (ICU) with respiratory failure not due to ARDS, a variable degree of lung edema is observed as well. We aimed to evaluate the prognostic value of RALE in mechanically ventilated ICU patients. Methods: Secondary analysis of patients enrolled in the ‘Diagnosis of Acute Respiratory Distress Syndrome’ (DARTS) project with an available chest X-ray (CXR) at baseline. Where present, additional CXRs at day 1 were analysed. The primary endpoint was 30-day mortality. Outcomes were also stratified for ARDS subgroups (no ARDS, non-COVID-ARDS and COVID-ARDS). Results: 422 patients were included, of which 84 had an additional CXR the following day. Baseline RALE scores were not associated with 30-day mortality in the entire cohort (OR: 1.01, 95% CI: 0.98–1.03, p = 0.66), nor in subgroups of ARDS patients. Early changes in RALE score (baseline to day 1) were only associated with mortality in a subgroup of ARDS patients (OR: 1.21, 95% CI: 1.02–1.51, p = 0.04), after correcting for other known prognostic factors. Conclusions: The prognostic value of the RALE score cannot be extended to mechanically ventilated ICU patients in general. Only in ARDS patients, early changes in RALE score were associated with mortality.

Lung ultrasound (LUS) can be used to assess loss of aeration, which is associated with outcome in patients with coronavirus disease 2019 (COVID-19) presenting to the emergency department. We hypothesized that LUS scores are associated with outcome in critically ill COVID-19 patients receiving invasive ventilation. This retrospective international multicenter study evaluated patients with COVID-19–related acute respiratory distress syndrome (ARDS) with at least one LUS study within 5 days after invasive mechanical ventilation initiation. The global LUS score was calculated by summing the 12 regional scores (range 0–36). Pleural line abnormalities and subpleural consolidations were also scored. The outcomes were successful liberation from the ventilator and intensive care mortality within 28 days, analyzed with multistate, competing risk proportional hazard models. One hundred thirty-seven patients with COVID-19–related ARDS were included in our study. The global LUS score was associated with successful liberation from mechanical ventilation (hazard ratio [HR]: 0.91 95% confidence interval [CI] 0.87–0.96; P = 0.0007) independently of the ARDS severity, but not with 28 days mortality (HR: 1.03; 95% CI 0.97–1.08; P = 0.36). Subpleural consolidation and pleural line abnormalities did not add to the prognostic value of the global LUS score. Examinations within 24 hours of intubation showed no prognostic value. To conclude, a lower global LUS score 24 hours after invasive ventilation initiation is associated with increased probability of liberation from the mechanical ventilator COVID–19 ARDS patients, independently of the ARDS severity.

Background: There is a demand for a non-invasive bedside method to diagnose Acute Respiratory Distress Syndrome (ARDS). Octane was discovered and validated as the most important breath biomarker for diagnosis of ARDS using gas-chromatography and mass-spectrometry (GC-MS). However, GC-MS is unsuitable as a point-of-care (POC) test in the intensive care unit (ICU). Therefore, we determined if a newly developed POC breath test can reliably detect octane in exhaled breath of invasively ventilated ICU patients. Methods: Two developmental steps were taken to design a POC breath test that relies on gas-chromatography using air as carrier gas with a photoionization detector. Calibration measurements were performed with a laboratory prototype in healthy subjects. Subsequently, invasively ventilated patients were included for validation and assessment of repeatability. After evolving to a POC breath test, this device was validated in a second group of invasively ventilated patients. Octane concentration was based on the area under the curve, which was extracted from the chromatogram and compared to known values from calibration measurements. Results: Five healthy subjects and 53 invasively ventilated patients were included. Calibration showed a linear relation (R2 = 1.0) between the octane concentration and the quantified octane peak in the low parts per billion (ppb) range. For the POC breath test the repeatability was excellent (R2 = 0.98, ICC = 0.97 (95% CI 0.94–0.99)). Conclusion: This is the first study to show that a POC breath test can rapidly and reliably detect octane, with excellent repeatability, at clinically relevant levels of low ppb in exhaled breath of ventilated ICU patients. This opens possibilities for targeted exhaled breath analysis to be used as a bedside test and makes it a potential diagnostic tool for the early detection of ARDS.

It is unknown whether and to what extent the penetration depth of lung ultrasound (LUS) influences the accuracy of LUS findings. The current study evaluated and compared the LUS aeration score and two frequently used B-line scores with focal lung aeration assessed by chest computed tomography (CT) at different levels of depth in invasively ventilated intensive care unit (ICU) patients. In this prospective observational study, patients with a clinical indication for chest CT underwent a 12-region LUS examination shortly before CT scanning. LUS images were compared with corresponding regions on the chest CT scan at different subpleural depths. For each LUS image, the LUS aeration score was calculated. LUS images with B-lines were scored as the number of separately spaced B-lines (B-line count score) and the percentage of the screen covered by B-lines divided by 10 (B-line percentage score). The fixed-effect correlation coefficient (β) was presented per 100 Hounsfield units. A total of 40 patients were included, and 372 regions were analyzed. The best association between the LUS aeration score and CT was found at a subpleural depth of 5 cm for all LUS patterns (β = 0.30, p < 0.001), 1 cm for A- and B1-patterns (β = 0.10, p < 0.001), 6 cm for B1- and B2-patterns (β = 0.11, p < 0.001) and 4 cm for B2- and C-patterns (β = 0.07, p = 0.001). The B-line percentage score was associated with CT (β = 0.46, p = 0.001), while the B-line count score was not (β = 0.07, p = 0.305). In conclusion, the subpleural penetration depth of ultrasound increased with decreased aeration reflected by the LUS pattern. The LUS aeration score and the B-line percentage score accurately reflect lung aeration in ICU patients, but should be interpreted while accounting for the subpleural penetration depth of ultrasound.

Background The major complication of COVID-19 is hypoxaemic respiratory failure from capillary leak and alveolar oedema. Experimental and early clinical data suggest that the tyrosine-kinase inhibitor imatinib reverses pulmonary capillary leak. Methods This randomised, double-blind, placebo-controlled, clinical trial was done at 13 academic and non-academic teaching hospitals in the Netherlands. Hospitalised patients (aged ≥18 years) with COVID-19, as confirmed by an RT-PCR test for SARS-CoV-2, requiring supplemental oxygen to maintain a peripheral oxygen saturation of greater than 94% were eligible. Patients were excluded if they had severe pre-existing pulmonary disease, had pre-existing heart failure, had undergone active treatment of a haematological or non-haematological malignancy in the previous 12 months, had cytopenia, or were receiving concomitant treatment with medication known to strongly interact with imatinib. Patients were randomly assigned (1:1) to receive either oral imatinib, given as a loading dose of 800 mg on day 0 followed by 400 mg daily on days 1–9, or placebo. Randomisation was done with a computer-based clinical data management platform with variable block sizes (containing two, four, or six patients), stratified by study site. The primary outcome was time to discontinuation of mechanical ventilation and supplemental oxygen for more than 48 consecutive hours, while being alive during a 28-day period. Secondary outcomes included safety, mortality at 28 days, and the need for invasive mechanical ventilation. All efficacy and safety analyses were done in all randomised patients who had received at least one dose of study medication (modified intention-to-treat population). This study is registered with the EU Clinical Trials Register (EudraCT 2020–001236–10). Findings Between March 31, 2020, and Jan 4, 2021, 805 patients were screened, of whom 400 were eligible and randomly assigned to the imatinib group (n=204) or the placebo group (n=196). A total of 385 (96%) patients (median age 64 years [IQR 56–73]) received at least one dose of study medication and were included in the modified intention-to-treat population. Time to discontinuation of ventilation and supplemental oxygen for more than 48 h was not significantly different between the two groups (unadjusted hazard ratio [HR] 0·95 [95% CI 0·76–1·20]). At day 28, 15 (8%) of 197 patients had died in the imatinib group compared with 27 (14%) of 188 patients in the placebo group (unadjusted HR 0·51 [0·27–0·95]). After adjusting for baseline imbalances between the two groups (sex, obesity, diabetes, and cardiovascular disease) the HR for mortality was 0·52 (95% CI 0·26–1·05). The HR for mechanical ventilation in the imatinib group compared with the placebo group was 1·07 (0·63–1·80; p=0·81). The median duration of invasive mechanical ventilation was 7 days (IQR 3–13) in the imatinib group compared with 12 days (6–20) in the placebo group (p=0·0080). 91 (46%) of 197 patients in the imatinib group and 82 (44%) of 188 patients in the placebo group had at least one grade 3 or higher adverse event. The safety evaluation revealed no imatinib-associated adverse events. Interpretation The study failed to meet its primary outcome, as imatinib did not reduce the time to discontinuation of ventilation and supplemental oxygen for more than 48 consecutive hours in patients with COVID-19 requiring supplemental oxygen. The observed effects on survival (although attenuated after adjustment for baseline imbalances) and duration of mechanical ventilation suggest that imatinib might confer clinical benefit in hospitalised patients with COVID-19, but further studies are required to validate these findings.&nbsp

Background Acute respiratory distress syndrome (ARDS) is currently diagnosed by the Berlin Definition. Diagnosis is subjective and often late. Untargeted metabolomics analysis of exhaled breath with gas chromatography and mass spectrometry (GC-MS) showed that the breath concentration of octane has a high diagnostic accuracy for ARDS. To facilitate rapid bedside measurement of this biomarker, a point-of-care (POC) breath test was developed. A prototype already showed good reproducibility and repeatability for the detection of octane. In this study we aim to measure octane in exhaled breath of invasively ventilated intensive care unit (ICU) patients and validate the diagnostic accuracy of the breath test for the early diagnosis of ARDS. Methods This is a multicentre observational cohort study in patients admitted to the ICU receiving invasive ventilation for at least 24 hours. At least 500 patients in two academic hospitals in The Netherlands will be included. ARDS patients will be compared to patients without ARDS. ARDS diagnosis will be based on the Berlin Definition. Two diagnostic assessments will be performed during the first 72 hours of invasive ventilation, including breath sampling, arterial blood gas analysis and lung ultrasound (LUS). In patients fulfilling the criteria for ARDS, three additional breath samples will be taken to assess resolution. The primary endpoint is the diagnostic accuracy for ARDS, defined by the area under the receiver operating characteristics curve (AUROCC) of octane concentration in exhaled breath. Secondary endpoints are the association between exhaled breath octane and ARDS adjusted for confounders, and the added diagnostic accuracy of the breath test on top of the Lung Injury Prediction Score (LIPS). Discussion This is the first study that validates a metabolic biomarker of ARDS in an adequate sample size. The major novelty is the use of a POC breath test that has been specifically developed for the purpose of diagnosing ARDS. Strengths are; assessment in the early phase, in patients at risk for ARDS, longitudinal sampling and an expert panel to reliably diagnose ARDS. This study will provide a decisive answer on the question if exhaled breath metabolomics can be used to diagnose ARDS. Trial registration The trial is registered at trialregister.nl (ID: NL8226) with the tag "DARTS".

Background: There is a demand for a non-invasive bedside method to diagnose Acute Respiratory Distress Syndrome (ARDS). Octane was discovered and validated as the most important breath biomarker for diagnosis of ARDS using gas-chromatography and mass-spectrometry (GC-MS). However, GC-MS is unsuitable as a point-of-care (POC) test in the intensive care unit (ICU). Therefore, we determined if a newly developed POC breath test can reliably detect octane in exhaled breath of invasively ventilated ICU patients. Methods: Two developmental steps were taken to design a POC breath test that relies on gas-chromatography using air as carrier gas with a photoionization detector. Calibration measurements were performed with a laboratory prototype in healthy subjects. Subsequently, invasively ventilated patients were included for validation and assessment of repeatability. After evolving to a POC breath test, this device was validated in a second group of invasively ventilated patients. Octane concentration was based on the area under the curve, which was extracted from the chromatogram and compared to known values from calibration measurements. Results: Five healthy subjects and 53 invasively ventilated patients were included. Calibration showed a linear relation (R2 = 1.0) between the octane concentration and the quantified octane peak in the low parts per billion (ppb) range. For the POC breath test the repeatability was excellent (R2 = 0.98, ICC = 0.97 (95% CI 0.94–0.99)). Conclusion: This is the first study to show that a POC breath test can rapidly and reliably detect octane, with excellent repeatability, at clinically relevant levels of low ppb in exhaled breath of ventilated ICU patients. This opens possibilities for targeted exhaled breath analysis to be used as a bedside test and makes it a potential diagnostic tool for the early detection of ARDS.

Rationale: Recent studies showed that biological subphenotypes in acute respiratory distress syndrome (ARDS) provide prognostic enrichment and show potential for predictive enrichment. Objectives: To determine whether these subphenotypes and their prognostic and potential for predictive enrichment could be extended to other patients in the ICU, irrespective of fulfilling the definition of ARDS. Methods: This is a secondary analysis of a prospective observational study of adult patients admitted to the ICU. We tested the prognostic enrichment of both cluster-derived and latentclass analysis (LCA)-derived biological ARDS subphenotypes by evaluating the association with clinical outcome (ICU-day, 30-day mortality, and ventilator-free days) using logistic regression and Cox regression analysis. We performed a principal component analysis to compare blood leukocyte gene expression profiles between subphenotypes and the presence of ARDS. Measurements and Main Results: We included 2,499 mechanically ventilated patients (674 with and 1,825 without ARDS). The cluster-derived "reactive"subphenotype was, independently of ARDS, significantly associated with a higher probability of ICU mortality, higher 30-day mortality, and a lower probability of successful extubation while alive compared with the "uninflamed"subphenotype. The blood leukocyte gene expression profiles of individual subphenotypes were similar for patients with and without ARDS. LCA-derived subphenotypes also showed similar profiles. Conclusions: The prognostic and potential for predictive enrichment of biological ARDS subphenotypes may be extended to mechanically ventilated critically ill patients without ARDS. Using the concept of biological subphenotypes for splitting cohorts of critically ill patients could add to improving future precision-based trial strategies and lead to identifying treatable traits for all critically ill patients.

Background: Recruitment maneuvers (RMs) have heterogeneous effects on lung aeration and have adverse side effects. We aimed to identify morphological, anatomical, and functional imaging characteristics that might be used to predict the RMs on lung aeration in invasively ventilated patients. Methods: We performed a systemic review. Studies included invasively ventilated patients who received an RM and in whom re-aeration was examined with chest computed tomography (CT), electrical impedance tomography (EIT), and lung ultrasound (LUS) were included. Results: Twenty studies were identified. Different types of RMs were applied. The amount of re-aerated lung tissue after an RM was highly variable between patients in all studies, irrespective of the used imaging technique and the type of patients (ARDS or non-ARDS). Imaging findings suggesting a non-focal morphology (i.e. radiologic findings consistent with attenuations with diffuse or patchy loss of aeration) were associated with higher likelihood of recruitment and lower chance of overdistention than a focal morphology (i.e. radiological findings suggestive of lobar or segmental loss of aeration). This was independent of the used imaging technique but only observed in patients with ARDS. In patients without ARDS, the results were inconclusive. Conclusions: ARDS patients with imaging findings suggestive of non-focal morphology show most re-aeration of previously consolidated lung tissue after RMs. The role of imaging techniques in predicting the effect of RMs on re-aeration in patients without ARDS remains uncertain., SCOPUS: re.j, info:eu-repo/semantics/published

International audience; Acute respiratory distress syndrome (ARDS) is a devastating critical illness that can be triggered by a wide range of insults and remains associated with a high mortality of around 40%. The search for targeted treatment for ARDS has been disappointing, possibly due to the enormous heterogeneity within the syndrome. In this perspective from the European Respiratory Society research seminar on "Precision medicine in ARDS", we will summarise the current evidence for heterogeneity, explore the evidence in favour of precision medicine and provide a roadmap for further research in ARDS. There is evident variation in the presentation of ARDS on three distinct levels: 1) aetiological; 2) physiological and 3) biological, which leads us to the conclusion that there is no typical ARDS. The lack of a common presentation implies that intervention studies in patients with ARDS need to be phenotype aware and apply a precision medicine approach in order to avoid the lack of success in therapeutic trials that we faced in recent decades. Deeper phenotyping and integrative analysis of the sources of variation might result in identification of additional treatable traits that represent specific pathobiological mechanisms, or so-called endotypes.

Background: Little is known about the practice of ventilation management in patients with COVID-19. We aimed to describe the practice of ventilation management and to establish outcomes in invasively ventilated patients with COVID-19 in a single country during the first month of the outbreak. Methods: PRoVENT-COVID is a national, multicentre, retrospective observational study done at 18 intensive care units (ICUs) in the Netherlands. Consecutive patients aged at least 18 years were eligible for participation if they had received invasive ventilation for COVID-19 at a participating ICU during the first month of the national outbreak in the Netherlands. The primary outcome was a combination of ventilator variables and parameters over the first 4 calendar days of ventilation: tidal volume, positive end-expiratory pressure (PEEP), respiratory system compliance, and driving pressure. Secondary outcomes included the use of adjunctive treatments for refractory hypoxaemia and ICU complications. Patient-centred outcomes were ventilator-free days at day 28, duration of ventilation, duration of ICU and hospital stay, and mortality. PRoVENT-COVID is registered at ClinicalTrials.gov (NCT04346342). Findings: Between March 1 and April 1, 2020, 553 patients were included in the study. Median tidal volume was 6·3 mL/kg predicted bodyweight (IQR 5·7–7·1), PEEP was 14·0 cm H2O (IQR 11·0–15·0), and driving pressure was 14·0 cm H2O (11·2–16·0). Median respiratory system compliance was 31·9 mL/cm H2O (26·0–39·9). Of the adjunctive treatments for refractory hypoxaemia, prone positioning was most often used in the first 4 days of ventilation (283 [53%] of 530 patients). The median number of ventilator-free days at day 28 was 0 (IQR 0–15); 186 (35%) of 530 patients had died by day 28. Predictors of 28-day mortality were gender, age, tidal volume, respiratory system compliance, arterial pH, and heart rate on the first day of invasive ventilation. Interpretation: In patients with COVID-19 who were invasively ventilated during the first month of the outbreak in the Netherlands, lung-protective ventilation with low tidal volume and low driving pressure was broadly applied and prone positioning was often used. The applied PEEP varied widely, despite an invariably low respiratory system compliance. The findings of this national study provide a basis for new hypotheses and sample size calculations for future trials of invasive ventilation for COVID-19. These data could also help in the interpretation of findings from other studies of ventilation practice and outcomes in invasively ventilated patients with COVID-19. Funding: Amsterdam University Medical Centers, location Academic Medical Center.

International guidelines do not recommend a specific probe for assessment of lung aeration using lung ultrasound (LUS). The aim of this study was to assess the concordance between linear and sector array probes of a handheld ultrasound device in assessment of lung aeration in invasively ventilated intensive care unit patients. This study included intensive care unit patients who were expected to be ventilated for longer than 24 h. A 12-region LUS exam was performed with a linear and a sector array probe. In each image, the LUS aeration score and number of B-lines were determined. Adding the LUS aeration scores of all regions resulted in a global LUS aeration score. Agreement between the two probes was calculated using intra-class correlation coefficients (ICCs). A total of 30 LUS exams were performed in 19 patients, resulting in a total of 328 pairs of images. Twenty-nine pairs of images were excluded from analysis because the images from the linear probe could not be scored. ICCs calculated for the remaining images revealed good concordance the LUS aeration scores for individual images (ICC = 0.73, 95% confidence interval 0.67-0.78), number of B-lines (ICC = 0.79, 95% confidence interval 0.72-0.83) and global LUS aeration score (ICC = 0.74, 95% confidence interval 0.52-0.87). In conclusion, there is good concordance between linear and sector array probes of a handheld ultrasound device in assessment of lung aeration patterns in mechanically ventilated intensive care unit patients. However, in roughly 10% of the images acquired using the linear probe, the aeration pattern could not be scored. (E-mail: m.r. smit@amsterdamumc.nl) (C) 2020 World Federation for Ultrasound in Medicine & Biology. All rights reserved.

Lung ultrasound (LUS) is a non-invasive bedside method used to quantify extravascular lung water (EVLW). To evaluate the methodology and diagnostic accuracy of LUS in studies assessing EVLW in intensive care unit patients, PubMed and Embase were searched for studies comparing LUS with imaging modalities. In 14 relevant studies a wide variety of equipment used and training of examiners were noted. Four scoring systems were reported: (i) a binary score (the presence of three or more B-lines); (ii) a categorical score; (iii) a numerical score; (iv) a quantitative LUS score using software. The diagnostic accuracy of LUS varied: sensitivity ranged from 50%–98%, specificity from 76%–100% and r² from 0.20–0.91. Methodology and diagnostic accuracy varies substantially in published reports. Further research is needed to correlate methodological factors with diagnostic accuracy. Hospitals should standardize LUS methodology. Consensus is needed to harmonize LUS methodology for lung water assessment.

Background: The chest X–ray (CXR) is part of the current ARDS definition (JAMA 2012; 307:2526) but detains poor interobserver reliability. The RALE score was recently proposed to evaluate lung edema on CXR in ARDS patients (Thorax 2018; 73: 840; figure 1A). The current study determined its diagnostic accuracy for ARDS in a cohort of ICU patients expected to need invasive ventilation for >24 hours. Methods: The current ARDS definition was used as the gold standard. The RALE score was calculated for the first available CXR. ROC curves were constructed, and the optimal cutoff was used to determine sensitivity, specificity, negative and positive predictive value of the RALE score for ARDS. Results: The study included 144 patients, of whom 33 had ARDS according to the current ARDS definition. A higher RALE score was found in patients with ARDS compared to patients without ARDS (23 [16–33] vs 7 [3–11]; P Conclusions: In this cohort of invasively ventilated ICU patients, the RALE score had an excellent diagnostic accuracy for ARDS, was easy to calculate, feasible and reliable. Additional validation of the cutoff and RALE performance is needed in larger cohorts.

Background: Lung ultrasound (LUS) is a non–invasive imaging technique useful for diagnosing and monitoring pulmonary edema. The Radiographic Assessment for Lung Edema (RALE) score was recently proposed for semi–quantification of pulmonary edema on chest X-rays (CXRs) (Thorax 2018; 73:840). We assessed the correlation between the global LUS score (CCM; 2010; 38:84) and the RALE score in a cohort of ICU patients expected to need invasive mechanical ventilation (MV) for >24 hours. Methods: Global LUS (range 0–36) and RALE scores (range 0–48) were calculated by independent observers from the first available LUS and CXR within the first 48 hours of MV. The Berlin Definition was used for diagnosing ARDS. Linear regression was used to quantify the proportion of variance in RALE (response variable) explained by LUS (explanatory variable). Results: LUS and CXR of 144 patients (33 with ARDS) were analyzed. The correlation between the global LUS and the RALE score was highly significant, with 89% of the variance in the RALE being explained by the global LUS score (Figure). The RALE score could be calculated from the global LUS score, as follows: RALE score = global LUS score * 1.3 – 0.7. Conclusions: The global LUS score explains most of the variance in the RALE score. This information adds to the available evidence that LUS is a potentially radiation–free alternative to the CXR in ventilated ICU patients.

Introduction: Reduced lung aeration is currently semi-quantified at the bedside by visual counting of vertical artifacts called B-lines on lung ultrasound (LUS) images. The accuracy of this method can be debated. We hypothesized that visual estimation of B-line coverage is a more accurate alternative to visual B-line counting in invasively ventilated ICU patients. Method: Invasively ventilated patients who received a clinical chest CT scan were included. A 12-region LUS exam was performed minutes before the CT scan. Lung regions scanned through LUS were compared to corresponding regions on CT. Lung aeration on CT was expressed in Hounsfield Units (HU). LUS images with a B-pattern, were visually scored by (a) estimating B-line coverage, expressed as the percentage of the screen covered by B-lines, and (b) counting the number of separately spaced B-lines. Associations between HU from the CT scan and the two B-line scores were tested with linear mixed effects model analysis. Results: The study included 23 patients, who had 87 LUS images with a B-pattern (median 3 [2-4] per patient). The B-line coverage was associated with the HU value from the CT scan; B-line count was not associated with the HU value. Conclusion: The visual B-line count on LUS images is an inaccurate score for lung aeration. Visual estimation of B-line coverage is a promising alternative for semi-quantification of aeration in LUS images.

Introduction: Differentiating ARDS from other forms of respiratory failure can be difficult. By advancing an optic fiber through a diagnostic bronchoscope, followed by an automatic pullback mechanism, OCT enables real-time 3D imaging of the alveolar compartment and peripheral airways. Aim: To investigate feasibility of bronchoscopic OCT, and to describe different OCT patterns of the alveolar compartment in mechanically ventilated patients. Methods: Observational study of OCT imaging in mechanically ventilated patients for non-resolving acute respiratory failure with an indication for diagnostic bronchoscopy. Results: 9 patients were included with clinical features of acute respiratory failure and bilateral pulmonary infiltrates not fully explained by cardiac failure (ARDS). Dominant CT patterns were ground glass(n=4), consolidation(n=3), reticulation(n=1), other(n=1). Total of 47 pullbacks were obtained without adverse events. Different patterns of the alveolar compartment (normal, alveolar filling, thickening of alveolar septae, loss of normal architecture of alveolar septae) were identified (Figure 1). Conclusions: This is the first study to show feasibility and safety of OCT imaging of alveolar compartment in mechanically ventilated patients. We identified different patterns, which could be helpful in the future to differentiate various causes of respiratory failure.

Introduction: Differentiating ARDS from other causes of respiratory failure can be challenging. CLE is a high resolution optical technique that, combined with conventional bronchoscopy, provides real-time, near-histology information about the alveolar compartment. Aim: To investigate feasibility and safety of CLE, and to describe different CLE characteristics of the alveolar compartment in patients with non-resolving respiratory failure on the ICU. Methods: Observational study of CLE imaging in mechanically ventilated patients with an indication for diagnostic bronchoscopy. Results: 10 patients were included with the clinical features of respiratory failure and bilateral chest opacities not fully explained by cardiac failure (ARDS). Dominant CT patterns were ground glass(n=4), consolidation(n=3), reticulation(n=1), other(n=2). High quality CLE imaging of the alveolar compartment was obtained in all patients without adverse events. 5 different CLE patterns (normal, alveolar filling with either fluid or cells, early and late fibrosis) were identified (Figure 1). Conclusion: This is the first study to show feasibility, safety and CLE characteristics of the alveolar compartment for various causes of respiratory failure in mechanically ventilated patients. CLE imaging has added value to chest CT and has the potential to distinguish between important causes of respiratory failure in critically ill patients at the ICU.

Background Semi-quantification of lung aeration by ultrasound helps to assess presence and extent of pulmonary pathologies, including the acute respiratory distress syndrome (ARDS). It is uncertain which lung regions add most to the diagnostic accuracy for ARDS of the frequently used global lung ultrasound (LUS) score. We aimed to compare the diagnostic accuracy of the global versus those of regional LUS scores in invasively ventilated intensive care unit patients. Methods This was a post-hoc analysis of a single-center observational study in the mixed medical–surgical intensive care unit of a university-affiliated hospital in the Netherlands. Consecutive patients, aged ≥ 18 years, and are expected to receive invasive ventilation for > 24 h underwent a LUS examination within the first 2 days of ventilation. The Berlin Definition was used to diagnose ARDS, and to classify ARDS severity. From the 12-region LUS examinations, the global score (minimum 0 to maximum 36) and 3 regional scores (the ‘anterior,’ ‘lateral,’ and ‘posterior’ score, minimum 0 to maximum 12) were computed. The area under the receiver operating characteristic (AUROC) curve was calculated and the best cutoff for ARDS discrimination was determined for all scores. Results The study enrolled 152 patients; 35 patients had ARDS. The global score was higher in patients with ARDS compared to patients without ARDS (median 19 [15–23] vs. 5 [3–9]; P Conclusions While the posterior score increases with ARDS severity, its diagnostic accuracy for ARDS is hampered due to an unfavorable signal-to-noise ratio. An 8-region ‘anterolateral’ score performs as well as the global score and may prove useful to exclude ARDS in invasively ventilated ICU patients.

Background: Semi–quantification of pulmonary aeration by lung ultrasound (LUS) can be expressed in a ‘global LUS score’ [Anesthesiology 2015; 122:437]. The importance of ‘regional LUS scores’ is unknown. We hypothesized that regional scores have discriminating capacities with regard to ARDS. Methods: This was a secondary analysis of an observational study that ran in a mixed ICU [ICM 2018; doi:10.1007/s00134-018-5048-5]. We included consecutive patients with expected ventilation for > 24 hours. The primary endpoint was ARDS, classified in mild, moderate or severe. LUS was performed in 12 lung fields scored from 0 (normal aeration) to 3 (consolidation), yielding a global LUS score from 0 to 36. Regional scores were derived from the sum of anterior, lateral or posterior regions. Results: Patients without ARDS had a significant lower global LUS score than patients with ARDS (5 [3–9] versus 19 [15–23]; P Conclusions: Both global and regional LUS scores discriminate well for ARDS in patients with invasive ventilation. Decreasing anterior LUS scores with increasing ARDS severity may point at overdistension.