Umbilical cord-derived CD362+ mesenchymal stromal cells for E. coli pneumonia: impact of dose regimen, passage, cryopreservation, and antibiotic therapy

Background

Mesenchymal stromal cells (MSCs) demonstrate considerable promise for acute respiratory distress syndrome (ARDS) and sepsis. However, standard approaches to MSC isolation generate highly heterogeneous cell populations, while bone marrow (BM) constitutes a limited and difficult to access MSC source. Furthermore, a range of cell manufacturing considerations and clinical setting practicalities remain to be explored.

Methods

Adult male rats were subject to E. coli-induced pneumonia and administered CD362⁺ umbilical cord (UC)-hMSCs using a variety of cell production and clinical relevance considerations. In series 1, animals were instilled with E. coli and randomized to receive heterogeneous BM or UC-hMSCs or CD362⁺ UC-hMSCs. Subsequent series examined the impact of concomitant antibiotic therapy, MSC therapeutic cryopreservation (cryopreserved vs fresh CD362⁺ UC-hMSCs), impact of cell passage on efficacy (passages 3 vs 5 vs 7 vs 10), and delay of administration of cell therapy (0 h vs 6 h post-injury vs 6 h + 12 h) following E. coli installation.

Results

CD362⁺ UC-hMSCs were as effective as heterogonous MSCs in reducing E. coli-induced acute lung injury, improving oxygenation, decreasing bacterial load, reducing histologic injury, and ameliorating inflammatory marker levels. Cryopreserved CD362⁺ UC-hMSCs recapitulated this efficacy, attenuating E. coli-induced injury, but therapeutic relevance did not extend beyond passage 3 for all indices. CD362⁺ UC-hMSCs maintained efficacy in the presence of antibiotic therapy and rescued the animal from E. coli injury when delivered at 6 h + 12 h, following E. coli instillation.

Conclusions

These translational studies demonstrated the efficacy of CD362⁺ UC-hMSCs, where they decreased the severity of E. coli-induced pneumonia, maintained efficacy following cryopreservation, were more effective at early passage, were effective in the presence of antibiotic therapy, and could continue to provide benefit at later time points following E. coli injury.

Is Activity Tracker-Measured Ambulation an Accurate and Reliable Determinant of Postoperative Quality of Recovery? A Prospective Cohort Validation Study

BACKGROUND

Quality of recovery (QOR) instruments measure patients' ability to return to baseline health status after surgery. Whether, and the extent to which, postoperative ambulation contributes to QOR is unclear, in part due to the lack of valid tools to measure ambulation in clinical settings. This cohort study of the cesarean delivery surgical model examines the accuracy and reliability of activity trackers in quantifying early postoperative ambulation and investigates the correlation between ambulation and QOR.

METHODS

A prospective cohort of 200 parturients undergoing cesarean delivery between July 2015 and June 2017 was fitted with wrist-worn activity trackers immediately postpartum. The trackers were collected 24 hours later, along with QOR assessments (QoR-15 scale). The relationship between QOR and various covariates, including ambulation, was explored using multivariable linear regression and Spearman correlation (ρ). Forty-eight parturients fitted with 2 trackers also completed a walk exercise accompanied by a step-counting assessor, to evaluate accuracy, inter-, and intradevice reliability using interclass correlation (ICC).

RESULTS

Compared to step counting, activity trackers had high accuracy (ICC = 0.93) and excellent inter- and intradevice reliability (ICC = 0.98 and 0.96, respectively). Correlation analysis suggested that early ambulation is moderately correlated with postcesarean QoR-15 scores, with a ρ (95% confidence interval) equivalent to 0.56 (0.328-0.728). Regression analysis suggested that ambulation is a determinant of postcesarean QoR-15 scores, with an effect estimate (95% confidence interval) equivalent to 0.002 (0.001-0.003). Ambulation was also associated with all QoR-15 domains, except psychological support. The patient's acceptable symptom state (subjective threshold for good ambulation) in the first 24 hours was 287 steps.

CONCLUSIONS

This study demonstrated the accuracy and reliability of activity trackers in measuring ambulation in clinical settings and suggested that postoperative ambulation is a determinant of postoperative QOR. A hypothetical implication of our findings is that interventions that improve ambulation may also help to enhance QOR, but further research is needed to establish a causal relationship.

Cytokine pre-activation of cryopreserved xenogeneic-free human mesenchymal stromal cells enhances resolution and repair following ventilator-induced lung injury potentially via a KGF-dependent mechanism

BACKGROUND

Human mesenchymal stem/stromal cells (hMSCs) represent a promising therapeutic strategy for ventilator-induced lung injury (VILI) and acute respiratory distress syndrome. Translational challenges include restoring hMSC efficacy following cryopreservation, developing effective xenogeneic-free (XF) hMSCs and establishing true therapeutic potential at a clinically relevant time point of administration. We wished to determine whether cytokine pre-activation of cryopreserved, bone marrow-derived XF-hMSCs would enhance their capacity to facilitate injury resolution following VILI and elucidate mechanisms of action.

METHODS

Initially, in vitro studies examined the potential for the secretome from cytokine pre-activated XF-hMSCs to attenuate pulmonary epithelial injury induced by cyclic mechanical stretch. Later, anaesthetised rats underwent VILI and, 6 h following injury, were randomized to receive 1 × 107 XF-hMSC/kg that were (i) naive fresh, (ii) naive cryopreserved, (iii) cytokine pre-activated fresh or (iv) cytokine pre-activated cryopreserved, while control animals received (v) vehicle. The extent of injury resolution was measured at 24 h after injury. Finally, the role of keratinocyte growth factor (KGF) in mediating the effect of pre-activated XF-hMSCs was determined in a pulmonary epithelial wound repair model.

RESULTS

Pre-activation enhanced the capacity of the XF-hMSC secretome to decrease stretch-induced pulmonary epithelial inflammation and injury. Both pre-activated fresh and cryopreserved XF-hMSCs enhanced resolution of injury following VILI, restoring oxygenation, improving lung compliance, reducing lung leak and improving resolution of lung structural injury. Finally, the secretome of pre-activated XF-hMSCs enhanced epithelial wound repair, in part via a KGF-dependent mechanism.

CONCLUSIONS

Cytokine pre-activation enhanced the capacity of cryopreserved, XF-hMSCs to promote injury resolution following VILI, potentially via a KGF-dependent mechanism.

Accuracy of pediatric cricothyroid membrane identification by digital palpation and implications for emergency front of neck access

BACKGROUND

Emergency front of neck access in a "can't intubate can't oxygenate" scenario in pediatrics is rare. Ideally airway rescue would involve the presence of an ear, nose, and throat surgeon. If unavailable however, responsibility lies with the anesthesiologist and accurate identification of anterior neck structures is essential for success.

AIM

We assessed anesthesiologists' accuracy in identification of the pediatric cricothyroid membrane by digital palpation in three predefined age groups (37 weeks to <1 year old, 1-8 years old, and 9-16 years old) and whether accuracy improved with repetition. We also investigated a novel hypothetical vertical skin incision strategy to successfully expose the cricothyroid membrane.

METHODS

We asked anesthesiologists to identify the location of the cricothyroid membrane of anesthetized children in the extended neck position. Accuracy was defined as a mark made within the margins of the cricothyroid membrane using ultrasound as a reference standard. The position of the cricothyroid membrane relative to the neck midpoint, between the suprasternal notch and mentum, was defined for each child. Using this neck midpoint, we determined the hypothetical vertical skin incision lengths required to successfully expose the cricothyroid membrane ("midpoint incision").

RESULTS

Ninety-seven patients were included in this study. There were 14, 58, and 25 patients recruited across the three predefined groups. Accurate anesthesiologist identification of the location of the cricothyroid membrane occurred in 29.4%, 28.6%, and 38.2% of attempts, respectively. The majority of inaccurate assessments (64.1%) were below the cricothyroid membrane. There was no improvement in accuracy with repetition. Hypothetical "midpoint incision" lengths of 20, 30, and 35 mm were required.

CONCLUSION

Significant anesthesiologist inaccuracy exists in locating the cricothyroid membrane in children of all ages. This has implications for the technical approach to emergency front of neck access and how we teach the management of "can't intubate can't oxygenate" in pediatric practice.

Nebulized Mesenchymal Stem Cell Derived Conditioned Medium Retains Antibacterial Properties Against Clinical Pathogen Isolates

Background: Mesenchymal stem/stromal cells (MSCs) have demonstrated promise in pathogenic acute respiratory distress syndrome models and are advancing to clinical efficacy testing. Besides immunomodulatory effects, MSC derived conditioned medium (CM) has direct antibacterial effects, possibly through LL-37 and related secreted peptide activity. We investigated MSC-CM compatibility with vibrating mesh technology, allowing direct delivery to the infected lung. Methods: MSC-CM from bone marrow (BM) and umbilical cord (UC) MSCs were passed through the commercially available Aerogen Solo nebulizer. Known colony forming units of Escherichia coli, Staphylococcus aureus, and multidrug resistant Klebsiella pneumoniae clinical isolates were added to MSC-CM in an orbital shaker and antibacterial capacity assessed through OD600 spectrophotometry. To exclude the possible effects of medium depletion on bacteria proliferation, MSC-CM was concentrated with a 3000 Da cutoff filter, diluted with fresh media, and retested against inoculum. Enzyme-linked immunosorbent assay was used to quantify levels of antimicrobial peptides (AMPs) and IL-8 present at pre- and postnebulization. Results: Both BM and UC MSC-CM inhibited proliferation of all pathogens, and this ability was retained after nebulization. Concentrating and reconstituting CM did not affect antibacterial properties. Interestingly, LL-37 protein did not appear to survive nebulization, although other secreted AMPs and an unrelated protein, IL-8, were largely intact. Conclusion: MSC-CM is a potent antimicrobial agent and is compatible with vibrating mesh nebulization delivery. The mechanism is through a secreted factor that is over 3000 Da in size, although it does not appear to rely solely on previously identified peptides such as LL-37, hepcidin, or lipocalin-2.

Modulating the distribution and fate of exogenously delivered MSCs to enhance therapeutic potential: knowns and unknowns

Mesenchymal stem/stromal cells (MSCs) are undergoing intensive translational research for several debilitating conditions, including critical illnesses such as ARDS and sepsis. MSCs exert diverse biologic effects via their interaction with host tissues, via mechanisms that require the MSC to be in close proximity to the area of injury. Fully harnessing the therapeutic potential of advanced medicinal therapeutic products such as MSCs and their successful translation to clinical use requires a detailed understanding of MSC distribution and persistence in the injured tissues.

Key aspects include understanding MSC distribution within the body, the response of the host to MSC administration, and the ultimate fate of exogenously administered MSCs within the host. Factors affecting this interaction include the MSC tissue source, the in vitro MSC culture conditions, the route of MSC administration and the specific issues relating to the target disease state, each of which remains to be fully characterised. Understanding these factors may generate strategies to modify MSC distribution and fate that may enhance their therapeutic effect.

This review will examine our understanding of the mechanisms of action of MSCs, the early and late phase distribution kinetics of MSCs following in vivo administration, the ultimate fate of MSCs following administration and the potential importance of these MSC properties to their therapeutic effects. We will critique current cellular imaging and tracking methodologies used to track exogenous MSCs and their suitability for use in patients, discuss the insights they provide into the distribution and fate of MSCs after administration, and suggest strategies by which MSC biodistribution and fate may be modulated for therapeutic effect and clinical use.

In conclusion, a better understanding of patterns of biodistribution and of the fate of MSCs will add important additional safety data regarding MSCs, address regulatory requirements, and may uncover strategies to increase the distribution and/or persistence of MSC at the sites of injury, potentially increasing their therapeutic potential for multiple disorders.

Demographics, management and outcome of females and males with acute respiratory distress syndrome in the LUNG SAFE prospective cohort study

Rationale

We wished to determine the influence of sex on the management and outcomes in acute respiratory distress syndrome (ARDS) patients in the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE).

Methods

We assessed the effect of sex on mortality, intensive care unit and hospital length of stay, and duration of invasive mechanical ventilation (IMV) in patients with ARDS who underwent IMV, adjusting for plausible clinical and geographic confounders.

Findings

Of 2377 patients with ARDS, 905 (38%) were female and 1472 (62%) were male. There were no sex differences in clinician recognition of ARDS or critical illness severity profile. Females received higher tidal volumes (8.2±2.1 versus 7.2±1.6 mL·kg−1; p<0.0001) and higher plateau and driving pressures compared with males. Lower tidal volume ventilation was received by 50% of females compared with 74% of males (p<0.0001). In shorter patients (height ≤1.69 m), females were significantly less likely to receive lower tidal volumes. Surviving females had a shorter duration of IMV and reduced length of stay compared with males. Overall hospital mortality was similar in females (40.2%) versus males (40.2%). However, female sex was associated with higher mortality in patients with severe confirmed ARDS (OR for sex (male versus female) 0.35, 95% CI 0.14–0.83).

Conclusions

Shorter females with ARDS are less likely to receive lower tidal volume ventilation, while females with severe confirmed ARDS have a higher mortality risk. These data highlight the need for better ventilatory management in females to improve their outcomes from ARDS.

Overexpression of IL-10 Enhances the Efficacy of Human Umbilical-Cord-Derived Mesenchymal Stromal Cells in E. coli Pneumosepsis

Enhancing the immunomodulatory effects of mesenchymal stromal cells (MSCs) may increase their effects in sepsis. We tested the potential for overexpression of Interleukin-10 (IL-10) in human umbilical cord (UC) MSCs to increase MSC efficacy in Escherichia coli (E. coli) pneumosepsis and to enhance human macrophage function. Pneumonia was induced in rats by intratracheal instillation of E. coli ((2.0–3.0) × 10⁹ Colony forming units (CFU)/kg). One hour later, animals were randomized to receive (a) vehicle; (b) naïve UC-MSCs; or (c) IL-10 overexpressing UC-MSCs (1 × 10⁷ cells/kg). Lung injury severity, cellular infiltration, and E. coli colony counts were assessed after 48 h. The effects and mechanisms of action of IL-10 UC-MSCs on macrophage function in septic rodents and in humans were subsequently assessed. Survival increased with IL-10 (9/11 (82%)) and naïve (11/12 (91%)) UC-MSCs compared to vehicle (9/15 (60%, p = 0.03). IL-10 UC-MSCs—but not naïve UC-MSCs—significantly decreased the alveolar arterial gradient (455 ± 93 and 520 ± 81, mmHg, respectively) compared to that of vehicle animals (544 ± 52, p = 0.02). Lung tissue bacterial counts were significantly increased in vehicle- and naïve-UC-MSC-treated animals but were not different from sham animals in those treated with IL-10 overexpressing UC-MSCs. IL-10 (but not naïve) UC-MSCs decreased alveolar neutrophils and increased alveolar macrophage percentages compared to vehicle. IL-10 UC-MSCs decreased structural lung injury compared to naïve UC-MSC or vehicle therapy. Alveolar macrophages from IL-10-UC-MSC-treated rats and from human volunteers demonstrated enhanced phagocytic capacity. This was mediated via increased macrophage hemeoxygenase-1, an effect blocked by prostaglandin E2 and lipoxygenase A4 blockade. IL-10 overexpression in UC-MSCs enhanced their effects in E. coli pneumosepsis and increased macrophage function. IL-10 UC-MSCs similarly enhanced human macrophage function, illustrating their therapeutic potential for infection-induced acute respiratory distress syndrome (ARDS).

Declining Mortality in Patients With Acute Respiratory Distress Syndrome: An Analysis of the Acute Respiratory Distress Syndrome Network Trials

OBJECTIVES

There has been multiple advances in the management of acute respiratory distress syndrome, but the temporal trends in acute respiratory distress syndrome-related mortality are not well known. This study aimed to investigate the trends in mortality in acute respiratory distress syndrome patients over time and to explore the roles of daily fluid balance and ventilation variables in those patients.

DESIGN

Secondary analysis of randomized controlled trials conducted by the Acute Respiratory Distress Syndrome Network from 1996 to 2013.

SETTING

Multicenter study involving Acute Respiratory Distress Syndrome Network trials.

PATIENTS

Patients with acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASURES AND MAIN RESULTS

Individual patient data from 5,159 acute respiratory distress syndrome patients (excluding the Late Steroid Rescue Study trial) were enrolled in this study. The crude mortality rate decreased from 35.4% (95% CI, 29.9-40.8%) in 1996 to 28.3% (95% CI, 22.0-34.7%) in 2013. By adjusting for the baseline Acute Physiology and Chronic Health Evaluation III, age, ICU type, and admission resource, patients enrolled from 2005 to 2010 (odds ratio, 0.61; 95% CI, 0.50-0.74) and those enrolled after 2010 (odds ratio, 0.73; 95% CI, 0.58-0.92) were associated with lower risk of death as compared to those enrolled before 2000. The effect of year on mortality decline disappeared after adjustment for daily fluid balance, positive end-expiratory pressure, tidal volume, and plateau pressure. There were significant trends of declines in daily fluid balance, tidal volume, and plateau pressure and an increase in positive end-expiratory pressure over the 17 years.

CONCLUSIONS

Our study shows an improvement in the acute respiratory distress syndrome-related mortality rate in the critically ill patients enrolled in the Acute Respiratory Distress Syndrome Network trials. The effect was probably mediated via decreased tidal volume, plateau pressure, and daily fluid balance and increased positive end-expiratory pressure.

Identifying associations between diabetes and acute respiratory distress syndrome in patients with acute hypoxemic respiratory failure: an analysis of the LUNG SAFE database

BACKGROUND

Diabetes mellitus is a common co-existing disease in the critically ill. Diabetes mellitus may reduce the risk of acute respiratory distress syndrome (ARDS), but data from previous studies are conflicting. The objective of this study was to evaluate associations between pre-existing diabetes mellitus and ARDS in critically ill patients with acute hypoxemic respiratory failure (AHRF).

METHODS

An ancillary analysis of a global, multi-centre prospective observational study (LUNG SAFE) was undertaken. LUNG SAFE evaluated all patients admitted to an intensive care unit (ICU) over a 4-week period, that required mechanical ventilation and met AHRF criteria. Patients who had their AHRF fully explained by cardiac failure were excluded. Important clinical characteristics were included in a stepwise selection approach (forward and backward selection combined with a significance level of 0.05) to identify a set of independent variables associated with having ARDS at any time, developing ARDS (defined as ARDS occurring after day 2 from meeting AHRF criteria) and with hospital mortality. Furthermore, propensity score analysis was undertaken to account for the differences in baseline characteristics between patients with and without diabetes mellitus, and the association between diabetes mellitus and outcomes of interest was assessed on matched samples.

RESULTS

Of the 4107 patients with AHRF included in this study, 3022 (73.6%) patients fulfilled ARDS criteria at admission or developed ARDS during their ICU stay. Diabetes mellitus was a pre-existing co-morbidity in 913 patients (22.2% of patients with AHRF). In multivariable analysis, there was no association between diabetes mellitus and having ARDS (OR 0.93 (0.78-1.11); p = 0.39), developing ARDS late (OR 0.79 (0.54-1.15); p = 0.22), or hospital mortality in patients with ARDS (1.15 (0.93-1.42); p = 0.19). In a matched sample of patients, there was no association between diabetes mellitus and outcomes of interest.

CONCLUSIONS

In a large, global observational study of patients with AHRF, no association was found between diabetes mellitus and having ARDS, developing ARDS, or outcomes from ARDS.

TRIAL REGISTRATION

NCT02010073 . Registered on 12 December 2013.

Lessons to learn from epidemiologic studies in ARDS

PURPOSE OF REVIEW

Recent advances in our understanding of the epidemiology of ARDS has generated key insights into the incidence, risk factors, demographics, management and outcomes from this devastating clinical syndrome.

RECENT FINDINGS

ARDS occurs in 10% of all ICU patients, in 23% of all mechanically ventilated patients, with 5.5 cases per ICU bed each year. Although some regional variation exists regarding ARDS incidence, this may be less than previously thought. Subphenotypes are increasingly identified within the ARDS cohort, with studies identifying a 'hyperinflammatory' or 'reactive' subgroup that has a higher mortality, and may respond differently to therapeutic interventions. Demographic factors, such as race, may also affect the therapeutic response. Although mortality in ARDS is decreasing in clinical trials, it remains unchanged at approximately 40% in major observational studies. Modifiable ventilatory management factors, including PEEP, airway pressures, and respiratory rate are associated with mortality in ARDS. Hospital and ICU organizational factors play a role in outcome, whereas socioeconomic status is independently associated with survival in patients with ARDS. The Kigali adaptation of the Berlin ARDS definition may provide useful insights into the burden of ARDS in the developing world.

SUMMARY

ARDS exerts a substantial disease burden, with 40% of patients dying in hospital. Diverse factors, including patient-related factors such as age and illness severity, country level socioeconomic status, and ventilator management and ICU organizational factors each contribute to outcome from ARDS. Addressing these issues provides opportunities to improve outcome in patients with ARDS.

Cell therapy in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is driven by a severe pro-inflammatory response resulting in lung damage, impaired gas exchange and severe respiratory failure. There is no specific treatment that effectively improves outcome in ARDS. However, in recent years, cell therapy has shown great promise in preclinical ARDS studies. A wide range of cells have been identified as potential candidates for use, among these are mesenchymal stromal cells (MSCs), which are adult multi-lineage cells that can modulate the immune response and enhance repair of damaged tissue. The therapeutic potential of MSC therapy for sepsis and ARDS has been demonstrated in multiple in vivo models. The therapeutic effect of these cells seems to be due to two different mechanisms; direct cellular interaction, and paracrine release of different soluble products such as extracellular vesicles (EVs)/exosomes. Different approaches have also been studied to enhance the therapeutic effect of these cells, such as the over-expression of anti-inflammatory or pro-reparative molecules. Several clinical trials (phase I and II) have already shown safety of MSCs in ARDS and other diseases. However, several translational issues still need to be addressed, such as the large-scale production of cells, and their potentiality and variability, before the therapeutic potential of stem cells therapies can be realized.

Epidemiology and patterns of tracheostomy practice in patients with acute respiratory distress syndrome in ICUs across 50 countries

Background

To better understand the epidemiology and patterns of tracheostomy practice for patients with acute respiratory distress syndrome (ARDS), we investigated the current usage of tracheostomy in patients with ARDS recruited into the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG-SAFE) study.

Methods

This is a secondary analysis of LUNG-SAFE, an international, multicenter, prospective cohort study of patients receiving invasive or noninvasive ventilation in 50 countries spanning 5 continents. The study was carried out over 4 weeks consecutively in the winter of 2014, and 459 ICUs participated. We evaluated the clinical characteristics, management and outcomes of patients that received tracheostomy, in the cohort of patients that developed ARDS on day 1–2 of acute hypoxemic respiratory failure, and in a subsequent propensity-matched cohort.

Results

Of the 2377 patients with ARDS that fulfilled the inclusion criteria, 309 (13.0%) underwent tracheostomy during their ICU stay. Patients from high-income European countries (n = 198/1263) more frequently underwent tracheostomy compared to patients from non-European high-income countries (n = 63/649) or patients from middle-income countries (n = 48/465). Only 86/309 (27.8%) underwent tracheostomy on or before day 7, while the median timing of tracheostomy was 14 (Q1–Q3, 7–21) days after onset of ARDS. In the subsample matched by propensity score, ICU and hospital stay were longer in patients with tracheostomy. While patients with tracheostomy had the highest survival probability, there was no difference in 60-day or 90-day mortality in either the patient subgroup that survived for at least 5 days in ICU, or in the propensity-matched subsample.

Conclusions

Most patients that receive tracheostomy do so after the first week of critical illness. Tracheostomy may prolong patient survival but does not reduce 60-day or 90-day mortality.

Trial registration

ClinicalTrials.gov, NCT02010073. Registered on 12 December 2013.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2126-6) contains supplementary material, which is available to authorized users.

Acute respiratory distress syndrome subphenotypes and differential response to simvastatin: secondary analysis of a randomised controlled trial

BACKGROUND

Precision medicine approaches that target patients on the basis of disease subtype have transformed treatment approaches to cancer, asthma, and other heterogeneous syndromes. Two distinct subphenotypes of acute respiratory distress syndrome (ARDS) have been identified in three US-based clinical trials, and these subphenotypes respond differently to positive end-expiratory pressure and fluid management. We aimed to investigate whether these subphenotypes exist in non-US patient populations and respond differently to pharmacotherapies.

METHODS

HARP-2 was a multicentre, randomised controlled trial of simvastatin (80 mg) versus placebo done in general intensive care units (ICUs) at 40 hospitals in the UK and Ireland within 48 h of onset of ARDS. The primary outcome was ventilator-free days, and secondary outcomes included non-pulmonary organ failure-free days and mortality. In a secondary analysis of HARP-2, we applied latent class analysis to baseline data without consideration of outcomes to identify subphenotypes, and we compared clinical outcomes across subphenotypes and treatment groups.

FINDINGS

540 patients were recruited to HARP-2. One patient withdrew consent for the use of their data, so data from 539 patients were analysed. In our secondary analysis, a two-class (two subphenotype) model was an improvement over a one-class model (p<0·0001), with 353 (65%) patients in the hypoinflammatory subphenotype group and 186 (35%) in the hyperinflammatory subphenotype group. Additional classes did not improve model fit. Clinical and biological characteristics of the two subphenotypes were similar to previous studies. Patients with the hyperinflammatory subphenotype had fewer ventilator-free days (median 2 days [IQR 0-17] vs 18 [IQR 0-23]; p<0·0001), fewer non-pulmonary organ failure-free days (15 [0-25] vs 27 [21-28]; p<0·0001), and higher 28-day mortality (73 [39%] vs 59 [17%]; p<0·0001) than did those with the hypoinflammatory subphenotype. Although HARP-2 found no difference in 28-day survival between placebo and simvastatin, significantly different survival was identified across patients stratified by treatment and subphenotype (p<0·0001). Specifically, within the hyperinflammatory subphenotype, patients treated with simvastatin had significantly higher 28-day survival than did those given placebo (p=0·008). A similar pattern was observed for 90-day survival.

INTERPRETATION

Two subphenotypes of ARDS were identified in the HARP-2 cohort, with distinct clinical and biological features and disparate clinical outcomes. The hyperinflammatory subphenotype had improved survival with simvastatin compared with placebo. These findings support further pursuit of predictive enrichment strategies in critical care clinical trials.

FUNDING

UK Efficacy and Mechanism Evaluation Programme and National Institutes of Health.

Immunocompromised patients with acute respiratory distress syndrome: secondary analysis of the LUNG SAFE database

Background

The aim of this study was to describe data on epidemiology, ventilatory management, and outcome of acute respiratory distress syndrome (ARDS) in immunocompromised patients.

Methods

We performed a post hoc analysis on the cohort of immunocompromised patients enrolled in the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE) study. The LUNG SAFE study was an international, prospective study including hypoxemic patients in 459 ICUs from 50 countries across 5 continents.

Results

Of 2813 patients with ARDS, 584 (20.8%) were immunocompromised, 38.9% of whom had an unspecified cause. Pneumonia, nonpulmonary sepsis, and noncardiogenic shock were their most common risk factors for ARDS. Hospital mortality was higher in immunocompromised than in immunocompetent patients (52.4% vs 36.2%; p < 0.0001), despite similar severity of ARDS. Decisions regarding limiting life-sustaining measures were significantly more frequent in immunocompromised patients (27.1% vs 18.6%; p < 0.0001). Use of noninvasive ventilation (NIV) as first-line treatment was higher in immunocompromised patients (20.9% vs 15.9%; p = 0.0048), and immunodeficiency remained independently associated with the use of NIV after adjustment for confounders. Forty-eight percent of the patients treated with NIV were intubated, and their mortality was not different from that of the patients invasively ventilated ab initio.

Conclusions

Immunosuppression is frequent in patients with ARDS, and infections are the main risk factors for ARDS in these immunocompromised patients. Their management differs from that of immunocompetent patients, particularly the greater use of NIV as first-line ventilation strategy. Compared with immunocompetent subjects, they have higher mortality regardless of ARDS severity as well as a higher frequency of limitation of life-sustaining measures. Nonetheless, nearly half of these patients survive to hospital discharge.

Trial registration

ClinicalTrials.gov, NCT02010073. Registered on 12 December 2013.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2079-9) contains supplementary material, which is available to authorized users.

Mesenchymal stem cells enhance NOX2-dependent reactive oxygen species production and bacterial killing in macrophages during sepsis

Human mesenchymal stem/stromal cells (MSCs) have been reported to produce an M2-like, alternatively activated phenotype in macrophages. In addition, MSCs mediate effective bacterial clearance in pre-clinical sepsis models. Thus, MSCs have a paradoxical antimicrobial and anti-inflammatory response that is not understood.Here, we studied the phenotypic and functional response of monocyte-derived human macrophages to MSC exposure in vitroMSCs induced two distinct, coexistent phenotypes: M2-like macrophages (generally elongated morphology, CD163⁺, acute phagosomal acidification, low NOX2 expression and limited phagosomal superoxide production) and M1-like macrophages characterised by high levels of phagosomal superoxide production. Enhanced phagosomal reactive oxygen species production was also observed in alveolar macrophages from a rodent model of pneumonia-induced sepsis. The production of M1-like macrophages was dependent on prostaglandin E₂ and phosphatidylinositol 3-kinase. MSCs enhanced human macrophage phagocytosis of unopsonised bacteria and enhanced bacterial killing compared with untreated macrophages. Bacterial killing was significantly reduced by blockade of NOX2 using diphenyleneiodonium, suggesting that M1-like cells are primarily responsible for this effect. MSCs also enhanced phagocytosis and polarisation of M1-like macrophages derived from patients with severe sepsis.The enhanced antimicrobial capacity (M1-like) and inflammation resolving phenotype (M2-like) may account for the paradoxical effect of these cells in sepsis in vivo.

Noninvasive mechanical ventilation in early acute respiratory distress syndrome

Noninvasive ventilation (NIV) has a well-‑established role in the treatment of acute-‑on-‑chronic respiratory failure and cardiogenic pulmonary edema. Its role in acute hypoxemic respiratory failure has been increasingly investigated, but its impact on the management and outcome of the subset of patients with acute respiratory distress syndrome (ARDS) is still to be determined. ARDS could be a risk factor for NIV failure, and in these patients, delayed endotracheal intubation can lead to an increased mortality. On the other hand, in a subset of patients with ARDS, endotracheal intubation can be avoided when NIV is applied. This review summarizes the current practice of NIV use in patients with ARDS and underlines the importance of proper patient selection before an NIV trial as well as criteria that should be used to predict failure early enough. A brief overview of high-‑flow nasal cannula is also provided. The use of NIV in ARDS is still debated, and it is important to be aware of the potential limitations and pitfalls of this treatment, which, when properly applied, could reduce the incidence of endotracheal intubation.

Fifty Years of Research in ARDS. Cell-based Therapy for Acute Respiratory Distress Syndrome. Biology and Potential Therapeutic Value

On the basis of several preclinical studies, cell-based therapy has emerged as a potential new therapeutic for acute respiratory distress syndrome (ARDS). Of the various cell-based therapy options, mesenchymal stem/stromal cells (MSCs) from bone marrow, adipose tissue, and umbilical cord have the most experimental data to support their potential efficacy for lung injury from both infectious and noninfectious causes. Mechanistically, MSCs exert their beneficial effects by release of paracrine factors, microvesicles, and transfer of mitochondria, all of which have antiinflammatory and pro-resolving effects on injured lung endothelium and alveolar epithelium, including enhancing the resolution of pulmonary edema by up-regulating sodium-dependent alveolar fluid clearance. MSCs also have antimicrobial effects mediated by release of antimicrobial factors and by up-regulating monocyte/macrophage phagocytosis. Phase 2a clinical trials to establish safety in ARDS are in progress, and two phase 1 trials did not report any serious adverse events. Several issues need further study, including: determining the optimal methods for large-scale production, reconstitution of cryopreserved cells for clinical use, defining cell potency assays, and determining the therapeutic potential of conditioned media derived from MSCs. Because ARDS is a heterogeneous syndrome, targeting MSCs to patients with ARDS with a more hyperinflammatory endotype may further enhance their potential for efficacy.

The intensive care medicine research agenda for airways, invasive and noninvasive mechanical ventilation

In an important sense, support of the respiratory system has been a defining characteristic of intensive care since its inception. The pace of basic and clinical research in this field has escalated over the past two decades, resulting in palpable improvement at the bedside as measured by both efficacy and outcome. As in all medical research, however, novel ideas built upon observations are continually proposed, tested, and either retained or discarded on the basis of the persuasiveness of the evidence. What follows are concise descriptions of the current standards of management practice in respiratory support, the areas of present-day uncertainty, and our suggested agenda for the near future of research aimed at testing current assumptions, probing uncertainties, and solidifying the foundation on which to base our progress to the next level.