Histopathologic heterogeneity of acute respiratory distress syndrome revealed by surgical lung biopsy and its clinical implications

Elevated plasma levels of Krebs von den Lungen-6 and geographic appearance on high-resolution computed tomography are associated with diffuse alveolar damage in autopsy cases of acute respiratory distress syndrome: a retrospective study

Background

Although diffuse alveolar damage (DAD) is a histopathological hallmark of acute respiratory distress syndrome (ARDS), its detection without lung biopsy is challenging. In patients with ARDS, the specificity of the Berlin definition to diagnose DAD as a reference standard is not adequately high, making it difficult to adequately diagnose DAD. The purpose of this study was to investigate the relationship between DAD and clinical findings, including KL-6 and geographic appearance, in ARDS patients and to identify more specific diagnostic criteria for DAD.

Methods

Among all adult autopsy cases at a tertiary hospital in Japan between January 2006 and March 2021, patients with ARDS who met the Berlin definition criteria were included. The patients’ conditions were classified according to histopathological patterns as DAD or non-DAD, and clinical characteristics, laboratory data, and high-resolution computed tomography (HRCT) findings were compared between the two groups.

Results

During the study period, 27 met the Berlin definition (median age: 79 years, 19 men), of whom 18 (67%) had DAD and 9 (33%) did not. In the non-DAD group, histopathologic findings revealed organizing pneumonia in seven patients and pulmonary hemorrhage in two patients. On HRCT at onset, patients with DAD had more geographic appearance than those without DAD (89% vs. 44%). In patients with geographic appearance and elevated KL-6 (> 500 U/mL), the sensitivity and specificity for DAD diagnosis were 56% and 100%, respectively. All three patients with no geographic appearance and normal KL-6 did not have DAD.

Conclusions

Geographic appearance on HRCT combined with KL-6 levels may predict the presence of DAD in patients with ARDS.

ARDS Clinical Practice Guideline 2021

BACKGROUND

The joint committee of the Japanese Society of Intensive Care Medicine/Japanese Respiratory Society/Japanese Society of Respiratory Care Medicine on ARDS Clinical Practice Guideline has created and released the ARDS Clinical Practice Guideline 2021.

METHODS

The 2016 edition of the Clinical Practice Guideline covered clinical questions (CQs) that targeted only adults, but the present guideline includes 15 CQs for children in addition to 46 CQs for adults. As with the previous edition, we used a systematic review method with the Grading of Recommendations Assessment Development and Evaluation (GRADE) system as well as a degree of recommendation determination method. We also conducted systematic reviews that used meta-analyses of diagnostic accuracy and network meta-analyses as a new method.

RESULTS

Recommendations for adult patients with ARDS are described: we suggest against using serum C-reactive protein and procalcitonin levels to identify bacterial pneumonia as the underlying disease (GRADE 2D); we recommend limiting tidal volume to 4-8 mL/kg for mechanical ventilation (GRADE 1D); we recommend against managements targeting an excessively low SpO2 (PaO2) (GRADE 2D); we suggest against using transpulmonary pressure as a routine basis in positive end-expiratory pressure settings (GRADE 2B); we suggest implementing extracorporeal membrane oxygenation for those with severe ARDS (GRADE 2B); we suggest against using high-dose steroids (GRADE 2C); and we recommend using low-dose steroids (GRADE 1B). The recommendations for pediatric patients with ARDS are as follows: we suggest against using non-invasive respiratory support (non-invasive positive pressure ventilation/high-flow nasal cannula oxygen therapy) (GRADE 2D), we suggest placing pediatric patients with moderate ARDS in the prone position (GRADE 2D), we suggest against routinely implementing NO inhalation therapy (GRADE 2C), and we suggest against implementing daily sedation interruption for pediatric patients with respiratory failure (GRADE 2D).

CONCLUSIONS

This article is a translated summary of the full version of the ARDS Clinical Practice Guideline 2021 published in Japanese (URL: https://www.jsicm.org/publication/guideline.html ). The original text, which was written for Japanese healthcare professionals, may include different perspectives from healthcare professionals of other countries.

ARDS clinical practice guideline 2021

BACKGROUND

The joint committee of the Japanese Society of Intensive Care Medicine/Japanese Respiratory Society/Japanese Society of Respiratory Care Medicine on ARDS Clinical Practice Guideline has created and released the ARDS Clinical Practice Guideline 2021.

METHODS

The 2016 edition of the Clinical Practice Guideline covered clinical questions (CQs) that targeted only adults, but the present guideline includes 15 CQs for children in addition to 46 CQs for adults. As with the previous edition, we used a systematic review method with the Grading of Recommendations Assessment Development and Evaluation (GRADE) system as well as a degree of recommendation determination method. We also conducted systematic reviews that used meta-analyses of diagnostic accuracy and network meta-analyses as a new method.

RESULTS

Recommendations for adult patients with ARDS are described: we suggest against using serum C-reactive protein and procalcitonin levels to identify bacterial pneumonia as the underlying disease (GRADE 2D); we recommend limiting tidal volume to 4-8 mL/kg for mechanical ventilation (GRADE 1D); we recommend against managements targeting an excessively low SpO₂ (PaO₂) (GRADE 2D); we suggest against using transpulmonary pressure as a routine basis in positive end-expiratory pressure settings (GRADE 2B); we suggest implementing extracorporeal membrane oxygenation for those with severe ARDS (GRADE 2B); we suggest against using high-dose steroids (GRADE 2C); and we recommend using low-dose steroids (GRADE 1B). The recommendations for pediatric patients with ARDS are as follows: we suggest against using non-invasive respiratory support (non-invasive positive pressure ventilation/high-flow nasal cannula oxygen therapy) (GRADE 2D); we suggest placing pediatric patients with moderate ARDS in the prone position (GRADE 2D); we suggest against routinely implementing NO inhalation therapy (GRADE 2C); and we suggest against implementing daily sedation interruption for pediatric patients with respiratory failure (GRADE 2D).

CONCLUSIONS

This article is a translated summary of the full version of the ARDS Clinical Practice Guideline 2021 published in Japanese (URL: https://www.jrs.or.jp/publication/jrs_guidelines/). The original text, which was written for Japanese healthcare professionals, may include different perspectives from healthcare professionals of other countries.

Macrophage-Targeted Nanomedicines for ARDS/ALI: Promise and Potential

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by progressive lung impairment typically triggered by inflammatory processes. The mortality toll for ARDS/ALI yet remains high because of the poor prognosis, lack of disease-specific inflammation management therapies, and prolonged hospitalizations. The urgency for the development of new effective therapeutic strategies has become acutely evident for patients with coronavirus disease 2019 (COVID-19) who are highly susceptible to ARDS/ALI. We propose that the lack of target specificity in ARDS/ALI of current treatments is one of the reasons for poor patient outcomes. Unlike traditional therapeutics, nanomedicine offers precise drug targeting to inflamed tissues, the capacity to surmount pulmonary barriers, enhanced interactions with lung epithelium, and the potential to reduce off-target and systemic adverse effects. In this article, we focus on the key cellular drivers of inflammation in ARDS/ALI: macrophages. We propose that as macrophages are involved in the etiology of ARDS/ALI and regulate inflammatory cascades, they are a promising target for new therapeutic development. In this review, we offer a survey of multiple nanomedicines that are currently being investigated with promising macrophage targeting potential and strategies for pulmonary delivery. Specifically, we will focus on nanomedicines that have shown engagement with proinflammatory macrophage targets and have the potential to reduce inflammation and reverse tissue damage in ARDS/ALI.

Clinical Utility of Surgical Lung Biopsy for Patients with Acute Respiratory Distress Syndrome: A Systematic Review and Meta-Analysis

BACKGROUND

Surgical lung biopsy (SLB) is performed in patients with acute respiratory distress syndrome (ARDS); however, its clinical utility remains unclear.

OBJECTIVES

We categorized the pathological diagnoses and investigated the predictive value for short-term mortality.

METHOD

Three electronic databases (MEDLINE, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov) were searched for the included studies. The QUADAS-2 was used to evaluate the risk of bias and its applicability. The types and populations of pathological diagnoses were investigated. The pooled sensitivity, positive likelihood ratio (LR+), negative likelihood ratio (LR-), and diagnostic odds ratio (DOR) were estimated at a fixed specificity. Hierarchical summary receiver operating characteristic curves were drawn.

RESULTS

A total of 16 studies that enrolled 758 patients were included. The pathological diagnoses were as follows: diffuse alveolar damage (DAD) 29.9%; infection 24.7%; interstitial lung disease 17.2%; malignancy 3.6%; cardiovascular disease 3.6%; drug toxicity 2.3%; connective tissue disease 2.2%; allergic disease 1.1%; and nonspecific diagnosis 15.4%. To predict short-term mortality, 13 studies that enrolled 613 patients used DAD as an index test and recorded a mortality rate of 56.9% (349 of 613 patients). A total of 3 studies that used index tests other than DAD were excluded. The pooled sensitivity, fixed specificity, LR+, LR-, and DOR were 0.46 (95% confidence interval [CI]: 0.29-0.56), 0.69, 1.48 (95% CI: 0.92-1.81), 0.78 (95% CI: 0.63-1.03), and 1.90 (95% CI: 0.89-2.86), respectively.

CONCLUSIONS

SLB is unlikely to provide a specific diagnosis and should not be recommended for confirming DAD or predicting ARDS prognosis.

Lung histopathological findings in COVID-19 disease - a systematic review

Since December 2019, the global burden of the COVID-19 pandemic has increased rapidly and has impacted nearly every country in the world, affecting those who are elderly or with underlying comorbidities or immunocompromised states. Aim of this systematic review is to summarize lung histopathological characteristics of COVID-19, not only for diagnostic purpose but also to evaluate changes that can reflect pathophysiological pathways that can inform clinicians of useful treatment strategies. We identified following histopathological changes among our patients:: hyaline membranes; endothelial cells/ interstitial cells involvement; alveolar cells, type I pneumocytes/ type II pneumocytes involvement; interstitial and/ or alveolar edema; evidence of hemorrhage, of inflammatory cells, evidence of microthrombi; evidence of fibrin deposition and of viral infection in the tissue samples.The scenario with proliferative cell desquamation is typical of Acute Respiratory Distress Syndrome (ARDS) that can be classified as diffuse alveolar damage (DAD) and not DAD-ARDS. The proposed pathological mechanism concerns the role of both innate and adaptive components of the immune system. COVID-19 lethal cases present themselves as a heterogeneous disease, characterized by the different simultaneous presence of different histological findings, which reflect histological phases with corresponding different pathological pathways (epithelial, vascular and fibrotic changes), in the same patient.

Video-Assisted Thoracoscopic Lung Biopsy in Critically Ill Patients With Hematologic Malignancy and Acute Respiratory Distress Syndrome: A Case Series Report

Pulmonary complications are prevalent among patients with hematologic malignancies, who are at high risk of developing acute respiratory distress syndrome (ARDS). Although diffuse alveolar damage is considered the diagnostic hallmark of ARDS, there are plenty of other non-diffuse alveolar damage etiologies that can mimic ARDS and benefit from a specific therapy, therefore correcting the underlying cause. When the etiology remains unclarified despite noninvasive procedures, a surgical lung biopsy (either open via thoracotomy or video-assisted thoracoscopic surgery [VATS]) may be warranted. However, the role of surgical lung biopsy has not been extensively studied in patients with hematologic malignancy and ARDS and so doubt exists about the risk-benefit relationship of such procedures. In this article, we report a series of 8 critically ill patients with hematologic malignancies and ARDS, who underwent VATS lung biopsy, in a specialized institution in Cali, Colombia, from 2015 to 2019, with special emphasis on its diagnostic yield, modifications in treatment protocol, and safety. VATS lung biopsy is a minimally invasive procedure that appears to be a relatively safe with few postoperative complications and minimal perioperative mortality. It has a high diagnostic yield, resulting in a modification of treatment in a nondepreciable percentage of patients. However, this subset of patients was critically ill, with a high risk of mortality, and the lung biopsy did not appear to affect in this aspect. Future randomized controlled trials are needed to further clarify this topic.

Predicting the Impact of Diffuse Alveolar Damage through Open Lung Biopsy in Acute Respiratory Distress Syndrome-The PREDATOR Study

The aim of this retrospective and international study is to identify those clinical variables associated with diffuse alveolar damage (DAD), and to explore the impact of DAD on hospital mortality risk. Inclusion criteria were: adult patients with acute respiratory distress syndrome (ARDS) undergoing open lung biopsy (OLB) during their intensive care unit (ICU) management. The main end-points were: DAD and hospital mortality. In the training (n = 193) and validation cohorts (n = 65), the respiratory rate (odd ratio (OR) 0.956; confidence interval (CI) 95% 0.918; 0.995) and coronary ischemia (OR 5.974; CI95% 1.668; 21.399) on the day of ARDS had an average area under the receiver operating characteristic curve (AUROC) of 0.660 (CI95% 0.585; 0.736) and 0.562 (0.417; 0.706), respectively. PEEP (OR 1.131; CI95% 1.051; 1.218) and coronary ischemia (OR 6.820; CI95% 1.856; 25.061) on the day of OLB had an average AUROC of 0.696 (CI95% 0.621; 0.769) and 0.534 (CI95% 0.391; 0.678), respectively, to predict DAD. DAD (OR 2.296; CI95% 1.228; 4.294), diabetes mellitus requiring insulin (OR 0.081; CI95% 0.009; 0.710) and the respiratory rate (OR 1.045; CI95% 1.001; 1.091) on the day of ARDS had an average AUROC of 0.659 (CI95% 0.583; 0.737) and 0.513 (CI95% 0.361; 0.664) to predict hospital mortality and DAD (OR 2.081; CI95% 1.053; 4.114), diabetes mellitus requiring insulin (OR 0.093; CI95% 0.009; 0.956), PaCO₂ (OR 1.051; CI95% 1.019; 1.084), and platelets count (OR 0.999; CI95% 0.999; 0.999) the day of OLB had an average AUROC of 0.778 (CI95% 0.710; 0.843) and 0.634 (CI95%0.481; 0.787) to predict hospital mortalty in the training and validation cohorts, respectively. In conclusion, DAD could not to be predicted clinically and was significantly associated with hospital mortality.