Accuracy of respiratory muscle assessments to predict weaning outcomes: a systematic review and comparative meta-analysis.

BACKGROUND: Several bedside assessments are used to evaluate respiratory muscle function and to predict weaning from mechanical ventilation in patients on the intensive care unit. It remains unclear which assessments perform best in predicting weaning success. The primary aim of this systematic review and meta-analysis was to summarize and compare the accuracy of the following assessments to predict weaning success: maximal inspiratory (PImax) and expiratory pressures, diaphragm thickening fraction and excursion (DTF and DE), end-expiratory (Tdiee) and end-inspiratory (Tdiei) diaphragm thickness, airway occlusion pressure (P0.1), electrical activity of respiratory muscles, and volitional and non-volitional assessments of transdiaphragmatic and airway opening pressures. METHODS: Medline (via Pubmed), EMBASE, Web of Science, Cochrane Library and CINAHL were comprehensively searched from inception to 04/05/2023. Studies including adult mechanically ventilated patients reporting data on predictive accuracy were included. Hierarchical summary receiver operating characteristic (HSROC) models were used to estimate the SROC curves of each assessment method. Meta-regression was used to compare SROC curves. Sensitivity analyses were conducted by excluding studies with high risk of bias, as assessed with QUADAS-2. Direct comparisons were performed using studies comparing each pair of assessments within the same sample of patients. RESULTS: Ninety-four studies were identified of which 88 studies (n = 6296) reporting on either PImax, DTF, DE, Tdiee, Tdiei and P0.1 were included in the meta-analyses. The sensitivity to predict weaning success was 63% (95% CI 47-77%) for PImax, 75% (95% CI 67-82%) for DE, 77% (95% CI 61-87%) for DTF, 74% (95% CI 40-93%) for P0.1, 69% (95% CI 13-97%) for Tdiei, 37% (95% CI 13-70%) for Tdiee, at fixed 80% specificity. Accuracy of DE and DTF to predict weaning success was significantly higher when compared to PImax (p = 0.04 and p < 0.01, respectively). Sensitivity and direct comparisons analyses showed that the accuracy of DTF to predict weaning success was significantly higher when compared to DE (p < 0.01). CONCLUSIONS: DTF and DE are superior to PImax and DTF seems to have the highest accuracy among all included respiratory muscle assessments for predicting weaning success. Further studies aiming at identifying the optimal threshold of DTF to predict weaning success are warranted. TRIAL REGISTRATION: PROSPERO CRD42020209295, October 15, 2020.

Clinical and molecular epidemiological features of critically ill patients with invasive group A Streptococcus infections: a Belgian multicenter case-series.

BACKGROUND: Recent alerts have highlighted an increase in group A streptococcal (GAS) infections since 2022 in Europe and the United States. Streptococcus pyogenes can cause limited skin or mucosal disease, but can also present as severe invasive disease necessitating critical care. We performed a multicenter retrospective study of patients with GAS infections recently admitted to Belgian intensive care units (ICUs) since January 2022. We describe patient characteristics and investigate the molecular epidemiology of the S. pyogenes strains involved. RESULTS: Between January 2022 and May 2023, a total of 86 cases (56 adults, 30 children) with GAS disease were admitted to critical care in the university hospitals of Leuven, Antwerp and Liège. We noted a strikingly high incidence of severe community-acquired pneumonia (sCAP) (45% of adults, 77% of children) complicated with empyema in 45% and 83% of adult and pediatric cases, respectively. Two-thirds of patients with S. pyogenes pneumonia had viral co-infection, with influenza (13 adults, 5 children) predominating. Other disease presentations included necrotizing fasciitis (23% of adults), other severe skin/soft tissue infections (16% of adults, 13% of children) and ear/nose/throat infections (13% of adults, 13% of children). Cardiogenic shock was frequent (36% of adults, 20% of children). Fifty-six patients (65%) had toxic shock syndrome. Organ support requirements were high and included invasive mechanical ventilation (77% of adults, 50% of children), renal replacement therapy (29% of adults, 3% of children) and extracorporeal membrane oxygenation (20% of adults, 7% of children). Mortality was 21% in adults and 3% in children. Genomic analysis of S. pyogenes strains from 55 out of 86 patients showed a predominance of emm1 strains (73%), with a replacement of the M1global lineage by the toxigenic M1UK lineage (83% of emm1 strains were M1UK). CONCLUSIONS: The recent rise of severe GAS infections (2022-23) is associated with introduction of the M1UK lineage in Belgium, but other factors may be at play-including intense circulation of respiratory viruses and potentially an immune debt after the COVID pandemic. Importantly, critical care physicians should include S. pyogenes as causative pathogen in the differential diagnosis of sCAP.

Lower respiratory tract single-cell RNA sequencing and neutrophil extracellular trap profiling of COVID-19-associated pulmonary aspergillosis: a single centre, retrospective, observational study.

BACKGROUND: COVID-19-associated pulmonary aspergillosis (CAPA) is a severe superinfection with the fungus Aspergillus affecting patients who are critically ill with COVID-19. The pathophysiology and the role of neutrophil extracellular traps (NETs) in this infection are largely unknown. We aimed to characterise the immune profile, with a focus on neutrophils and NET concentrations, of critically ill patients with COVID-19, with or without CAPA. METHODS: We conducted a single-centre, retrospective, observational study in two patient cohorts, both recruited at University Hospitals Leuven, Belgium. We included adults aged 18 years or older who were admitted to the intensive care unit because of COVID-19 between March 31, 2020, and May 18, 2021, and who were included in the previous Contagious trial (NCT04327570). We investigated the immune cellular landscape of CAPA versus COVID-19 only by performing single-cell RNA sequencing (scRNA-seq) on bronchoalveolar lavage fluid. Bronchoalveolar lavage immune cell fractions were compared between patients with CAPA and patients with COVID-19 only. Additionally, we determined lower respiratory tract NET concentrations using biochemical assays in patients aged 18 years and older who were admitted to the intensive care unit because of severe COVID-19 between March 15, 2020, and Dec 31, 2021, for whom bronchoalveolar lavage was available in the hospital biobank. Bronchoalveolar lavage NET concentrations were compared between patients with CAPA and patients with COVID-19 only and integrated with existing data on immune mediators in bronchoalveolar lavage and 90-day mortality. FINDINGS: We performed scRNA-seq of bronchoalveolar lavage on 43 samples from 39 patients, of whom 36 patients (30 male and six female; 14 with CAPA) were included in downstream analyses. We performed bronchoalveolar lavage NET analyses in 59 patients (46 male and 13 female), of whom 26 had CAPA. By scRNA-seq, patients with CAPA had significantly lower neutrophil fractions than patients with COVID-19 only (16% vs 33%; p=0·0020). The remaining neutrophils in patients with CAPA preferentially followed a hybrid maturation trajectory characterised by expression of genes linked to antigen presentation, with enhanced transcription of antifungal effector pathways. Patients with CAPA also showed depletion of mucosal-associated invariant T cells, reduced T helper 1 and T helper 17 differentiation, and transcriptional defects in specific aspects of antifungal immunity in macrophages and monocytes. We observed increased formation of NETs in patients with CAPA compared with patients with COVID-19 only (DNA complexed with citrullinated histone H3 median 15 898 ng/mL [IQR 4588-86 419] vs 7062 ng/mL [775-14 088]; p=0·042), thereby explaining decreased neutrophil fractions by scRNA-seq. Low bronchoalveolar lavage NET concentrations were associated with increased 90-day mortality in patients with CAPA. INTERPRETATION: Qualitative and quantitative disturbances in monocyte, macrophage, B-cell, and T-cell populations could predispose patients with severe COVID-19 to develop CAPA. Hybrid neutrophils form a specialised response to CAPA, and an adequate neutrophil response to CAPA is a major determinant for survival in these patients. Therefore, measuring bronchoalveolar lavage NETs could have diagnostic and prognostic value in patients with CAPA. Clinicians should be wary of aspergillosis when using immunomodulatory therapy that might inhibit NETosis to treat patients with severe COVID-19. FUNDING: Research Foundation Flanders, KU Leuven, UZ Leuven, VIB, the Fundação para a Ciência e a Tecnologia, the European Regional Development Fund, la Caixa Foundation, the Flemish Government, and Horizon 2020.

High Burden of COVID-19-Associated Pulmonary Aspergillosis in Severely Immunocompromised Patients Requiring Mechanical Ventilation.

BACKGROUND: Coronavirus disease 2019 (COVID-19)-associated pulmonary aspergillosis (CAPA) is a frequent superinfection in critically ill patients with COVID-19 and is associated with increased mortality rates. The increasing proportion of severely immunocompromised patients with COVID-19 who require mechanical ventilation warrants research into the incidence and impact of CAPA during the vaccination era. METHODS: We performed a retrospective, monocentric, observational study. We collected data from adult patients with severe COVID-19 requiring mechanical ventilation who were admitted to the intensive care unit (ICU) of University Hospitals Leuven, a tertiary referral center, between 1 March 2020 and 14 November 2022. Probable or proven CAPA was diagnosed according to the 2020 European Confederation for Medical Mycology/International Society for Human and Animal Mycology (ECMM/ISHAM) criteria. RESULTS: We included 335 patients. Bronchoalveolar lavage sampling was performed in 300 (90%), and CAPA was diagnosed in 112 (33%). The incidence of CAPA was 62% (50 of 81 patients) in European Organisation for Research and Treatment of Cancer (EORTC)/Mycosis Study Group Education and Research Consortium (MSGERC) host factor-positive patients, compared with 24% (62 of 254) in host factor-negative patients. The incidence of CAPA was significantly higher in the vaccination era, increasing from 24% (57 of 241) in patients admitted to the ICU before October 2021 to 59% (55 of 94) in those admitted since then. Both EORTC/MSGERC host factors and ICU admission in the vaccination era were independently associated with CAPA development. CAPA remained an independent risk factor associated with mortality risk during the vaccination era. CONCLUSIONS: The presence of EORTC/MSGERC host factors for invasive mold disease is associated with increased CAPA incidence and worse outcome parameters, and it is the main driver for the significantly higher incidence of CAPA in the vaccination era. Our findings warrant investigation of antifungal prophylaxis in critically ill patients with COVID-19.

Complications related to extracorporeal life support in lung transplantation: single-center analysis.

Background: Extracorporeal life support (ECLS) is not routinely used at our center during sequential single-lung transplantation (LTx), but is restricted to anticipate and overcome hemodynamic and respiratory problems occurring peri-operatively. In this retrospective descriptive cohort study, we aim to describe our single-center experience with ECLS in LTx, analyzing ECLS-related complications. Methods: All transplantations with peri-operative ECLS use [2010-2020] were retrospectively analyzed. Multi-organ and heart-lung transplantation were excluded. Demographics, support type and indications are described. Complications are categorized according to the underlying nature and type. Data are presented as median [interquartile range (IQR)]. Kaplan-Meier was used for survival analysis. Results: The overall use of ECLS was 22% (156/703 patients) with a mean age of 52 years (IQR, 36-59 years). Transplant indications in ECLS cohort were interstitial lung disease (38%; n=60), chronic obstructive pulmonary disease (COPD) (19%; n=29), cystic fibrosis (17%; n=26) and others (26%; n=41). Per indication, 94% (15/16) of pulmonary arterial hypertension patients required ECLS, whereas only 8% (29/382) of COPD patients did. In 16% (25/156) of supported patients, veno-venous extracorporeal membrane oxygenation was initiated, while 77% (120/156) required veno-arterial support, and 7% (11/156) cardiopulmonary bypass. Thirty-day mortality was 6% (9/156). Sixteen percent (25/156) of patients were bridged to transplantation on ECLS and 24% (37/156) required post-operative support. Main reasons to use ECLS were intra-operative hemodynamic instability (53%; n=82), ventilation/oxygenation problems (22%; n=34) and reperfusion edema (17%; n=26). Overall incidence of patients with at least one ECLS-related complication was 67% (n=104). Most common complications were hemothorax (25%; n=39), need for continuous renal replacement therapy (19%; n=30), and thromboembolism (14%; n=22). Conclusions: ECLS was required in 22% of LTxs, with a reported ECLS-related complication rate of 67%, of which the most common was hemothorax. Larger databases are needed to further analyze complications and develop tailored deployment strategies for ECLS-use in LTx.

Tight Blood-Glucose Control without Early Parenteral Nutrition in the ICU.

BACKGROUND: Randomized, controlled trials have shown both benefit and harm from tight blood-glucose control in patients in the intensive care unit (ICU). Variation in the use of early parenteral nutrition and in insulin-induced severe hypoglycemia might explain this inconsistency. METHODS: We randomly assigned patients, on ICU admission, to liberal glucose control (insulin initiated only when the blood-glucose level was >215 mg per deciliter [>11.9 mmol per liter]) or to tight glucose control (blood-glucose level targeted with the use of the LOGIC-Insulin algorithm at 80 to 110 mg per deciliter [4.4 to 6.1 mmol per liter]); parenteral nutrition was withheld in both groups for 1 week. Protocol adherence was determined according to glucose metrics. The primary outcome was the length of time that ICU care was needed, calculated on the basis of time to discharge alive from the ICU, with death accounted for as a competing risk; 90-day mortality was the safety outcome. RESULTS: Of 9230 patients who underwent randomization, 4622 were assigned to liberal glucose control and 4608 to tight glucose control. The median morning blood-glucose level was 140 mg per deciliter (interquartile range, 122 to 161) with liberal glucose control and 107 mg per deciliter (interquartile range, 98 to 117) with tight glucose control. Severe hypoglycemia occurred in 31 patients (0.7%) in the liberal-control group and 47 patients (1.0%) in the tight-control group. The length of time that ICU care was needed was similar in the two groups (hazard ratio for earlier discharge alive with tight glucose control, 1.00; 95% confidence interval, 0.96 to 1.04; P = 0.94). Mortality at 90 days was also similar (10.1% with liberal glucose control and 10.5% with tight glucose control, P = 0.51). Analyses of eight prespecified secondary outcomes suggested that the incidence of new infections, the duration of respiratory and hemodynamic support, the time to discharge alive from the hospital, and mortality in the ICU and hospital were similar in the two groups, whereas severe acute kidney injury and cholestatic liver dysfunction appeared less prevalent with tight glucose control. CONCLUSIONS: In critically ill patients who were not receiving early parenteral nutrition, tight glucose control did not affect the length of time that ICU care was needed or mortality. (Funded by the Research Foundation-Flanders and others; TGC-Fast ClinicalTrials.gov number, NCT03665207.).

Transfusion of red blood cells in venoarterial extracorporeal membrane oxygenation: A multicenter retrospective observational cohort study.

BACKGROUND: Evidence-based recommendations for transfusion in patients with venoarterial extracorporeal membrane oxygenation (VA ECMO) are scarce. The current literature is limited to single-center studies with small sample sizes, therefore complicating generalizability. This study aims to create an overview of red blood cell (RBC) transfusion in VA ECMO patients. METHODS: This international mixed-method study combined a survey with a retrospective observational study in 16 centers. The survey inventoried local transfusion guidelines. Additionally, retrospective data of all adult patients with a VA ECMO run >24 h (January 2018 until July 2019) was collected of patient, ECMO, outcome, and daily transfusion parameters. All patients that received VA ECMO for primary cardiac support were included, including surgical (i.e., post-cardiotomy) and non-surgical (i.e., myocardial infarction) indications. The primary outcome was the number of RBC transfusions per day and in total. Univariable logistic regressions and a generalized linear mixed model (GLMM) were performed to assess factors associated with RBC transfusion. RESULTS: Out of 419 patients, 374 (89%) received one or more RBC transfusions. During a median ECMO run of 5 days (1st-3rd quartile 3-8), patients received a median total of eight RBC units (1st-3rd quartile 3-17). A lower hemoglobin (Hb) prior to ECMO, longer ECMO-run duration, and hemorrhage were associated with RBC transfusion. After correcting for duration and hemorrhage using a GLMM, a different transfusion trend was found among the regimens. No unadjusted differences were found in overall survival between either transfusion status or the different regimens, which remained after adjustment for potential confounders. CONCLUSION: RBC transfusion in patients on VA ECMO is very common. The sum of RBC transfusions increases rapidly after ECMO initiation, and is dependent on the Hb threshold applied. This study supports the rationale for prospective studies focusing on indications and thresholds for RBC transfusion.

Plasma Transfusion and Procoagulant Product Administration in Extracorporeal Membrane Oxygenation: A Secondary Analysis of an International Observational Study on Current Practices.

OBJECTIVES: To achieve optimal hemostatic balance in patients on extracorporeal membrane oxygenation (ECMO), a liberal transfusion practice is currently applied despite clear evidence. We aimed to give an overview of the current use of plasma, fibrinogen concentrate, tranexamic acid (TXA), and prothrombin complex concentrate (PCC) in patients on ECMO. DESIGN: A prespecified subanalysis of a multicenter retrospective study. Venovenous (VV)-ECMO and venoarterial (VA)-ECMO are analyzed as separate populations, comparing patients with and without bleeding and with and without thrombotic complications. SETTING: Sixteen international ICUs. PATIENTS: Adult patients on VA-ECMO or VV-ECMO. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of 420 VA-ECMO patients, 59% (n = 247) received plasma, 20% (n = 82) received fibrinogen concentrate, 17% (n = 70) received TXA, and 7% of patients (n = 28) received PCC. Fifty percent of patients (n = 208) suffered bleeding complications and 27% (n = 112) suffered thrombotic complications. More patients with bleeding complications than patients without bleeding complications received plasma (77% vs. 41%, p < 0.001), fibrinogen concentrate (28% vs 11%, p < 0.001), and TXA (23% vs 10%, p < 0.001). More patients with than without thrombotic complications received TXA (24% vs 14%, p = 0.02, odds ratio 1.75) in VA-ECMO, where no difference was seen in VV-ECMO. Of 205 VV-ECMO patients, 40% (n = 81) received plasma, 6% (n = 12) fibrinogen concentrate, 7% (n = 14) TXA, and 5% (n = 10) PCC. Thirty-nine percent (n = 80) of VV-ECMO patients suffered bleeding complications and 23% (n = 48) of patients suffered thrombotic complications. More patients with than without bleeding complications received plasma (58% vs 28%, p < 0.001), fibrinogen concentrate (13% vs 2%, p < 0.01), and TXA (11% vs 2%, p < 0.01). CONCLUSIONS: The majority of patients on ECMO receive transfusions of plasma, procoagulant products, or antifibrinolytics. In a significant part of the plasma transfused patients, this was in the absence of bleeding or prolonged international normalized ratio. This poses the question if these plasma transfusions were administered for another indication or could have been avoided.

The interaction of thrombocytopenia, hemorrhage, and platelet transfusion in venoarterial extracorporeal membrane oxygenation: a multicenter observational study.

BACKGROUND: Thrombocytopenia, hemorrhage and platelet transfusion are common in patients supported with venoarterial extracorporeal membrane oxygenation (VA ECMO). However, current literature is limited to small single-center experiences with high degrees of heterogeneity. Therefore, we aimed to ascertain in a multicenter study the course and occurrence rate of thrombocytopenia, and to assess the association between thrombocytopenia, hemorrhage and platelet transfusion during VA ECMO. METHODS: This was a sub-study of a multicenter (N = 16) study on transfusion practices in patients on VA ECMO, in which a retrospective cohort (Jan-2018-Jul-2019) focusing on platelets was selected. The primary outcome was thrombocytopenia during VA ECMO, defined as mild (100-150·109/L), moderate (50-100·109/L) and severe (< 50·109/L). Secondary outcomes included the occurrence rate of platelet transfusion, and the association between thrombocytopenia, hemorrhage and platelet transfusion, assessed through mixed-effect models. RESULTS: Of the 419 patients included, median platelet count at admission was 179·109/L. During VA ECMO, almost all (N = 398, 95%) patients developed a thrombocytopenia, of which a significant part severe (N = 179, 45%). One or more platelet transfusions were administered in 226 patients (54%), whereas 207 patients (49%) suffered a hemorrhagic event during VA ECMO. In non-bleeding patients, still one in three patients received a platelet transfusion. The strongest association to receive a platelet transfusion was found in the presence of severe thrombocytopenia (adjusted OR 31.8, 95% CI 17.9-56.5). After including an interaction term of hemorrhage and thrombocytopenia, this even increased up to an OR of 110 (95% CI 34-360). CONCLUSIONS: Thrombocytopenia has a higher occurrence than is currently recognized. Severe thrombocytopenia is strongly associated with platelet transfusion. Future studies should focus on the etiology of severe thrombocytopenia during ECMO, as well as identifying indications and platelet thresholds for transfusion in the absence of bleeding. TRIAL REGISTRATION: This study was registered at the Netherlands Trial Registry at February 26th, 2020 with number NL8413 and can currently be found at https://trialsearch.who.int/Trial2.aspx?TrialID=NL8413.

Proteolytic inactivation of CXCL12 in the lungs and circulation of COVID-19 patients.

The human chemokine stromal cell-derived factor-1 (SDF-1) or CXCL12 is involved in several homeostatic processes and pathologies through interaction with its cognate G protein-coupled receptor CXCR4. Recent research has shown that CXCL12 is present in the lungs and circulation of patients with coronavirus disease 2019 (COVID-19). However, the question whether the detected CXCL12 is bioactive was not addressed. Indeed, the activity of CXCL12 is regulated by NH2- and COOH-terminal post-translational proteolysis, which significantly impairs its biological activity. The aim of the present study was to characterize proteolytic processing of CXCL12 in broncho-alveolar lavage (BAL) fluid and blood plasma samples from critically ill COVID-19 patients. Therefore, we optimized immunosorbent tandem mass spectrometry proteoform analysis (ISTAMPA) for detection of CXCL12 proteoforms. In patient samples, this approach uncovered that CXCL12 is rapidly processed by site-specific NH2- and COOH-terminal proteolysis and ultimately degraded. This proteolytic inactivation occurred more rapidly in COVID-19 plasma than in COVID-19 BAL fluids, whereas BAL fluid samples from stable lung transplantation patients and the non-affected lung of lung cancer patients (control groups) hardly induced any processing of CXCL12. In COVID-19 BAL fluids with high proteolytic activity, processing occurred exclusively NH2-terminally and was predominantly mediated by neutrophil elastase. In low proteolytic activity BAL fluid and plasma samples, NH2- and COOH-terminal proteolysis by CD26 and carboxypeptidases were observed. Finally, protease inhibitors already approved for clinical use such as sitagliptin and sivelestat prevented CXCL12 processing and may therefore be of pharmacological interest to prolong CXCL12 half-life and biological activity in vivo.

A Pathology-based Case Series of Influenza- and COVID-19-associated Pulmonary Aspergillosis: The Proof Is in the Tissue.

Rationale: Invasive pulmonary aspergillosis has emerged as a frequent coinfection in severe coronavirus disease (COVID-19), similarly to influenza, yet the clinical invasiveness is more debated. Objectives: We investigated the invasive nature of pulmonary aspergillosis in histology specimens of influenza and COVID-19 ICU fatalities in a tertiary care center. Methods: In this monocentric, descriptive, retrospective case series, we included adult ICU patients with PCR-proven influenza/COVID-19 respiratory failure who underwent postmortem examination and/or tracheobronchial biopsy during ICU admission from September 2009 until June 2021. Diagnosis of probable/proven viral-associated pulmonary aspergillosis (VAPA) was made based on the Intensive Care Medicine influenza-associated pulmonary aspergillosis and the European Confederation of Medical Mycology (ECMM) and the International Society for Human and Animal Mycology (ISHAM) COVID-19-associated pulmonary aspergillosis consensus criteria. All respiratory tissues were independently reviewed by two experienced pathologists. Measurements and Main Results: In the 44 patients of the autopsy-verified cohort, 6 proven influenza-associated and 6 proven COVID-19-associated pulmonary aspergillosis diagnoses were identified. Fungal disease was identified as a missed diagnosis upon autopsy in 8% of proven cases (n = 1/12), yet it was most frequently found as confirmation of a probable antemortem diagnosis (n = 11/21, 52%) despite receiving antifungal treatment. Bronchoalveolar lavage galactomannan testing showed the highest sensitivity for VAPA diagnosis. Among both viral entities, an impeded fungal growth was the predominant histologic pattern of pulmonary aspergillosis. Fungal tracheobronchitis was histologically indistinguishable in influenza (n = 3) and COVID-19 (n = 3) cases, yet macroscopically more extensive at bronchoscopy in influenza setting. Conclusions: A proven invasive pulmonary aspergillosis diagnosis was found regularly and with a similar histological pattern in influenza and in COVID-19 ICU case fatalities. Our findings highlight an important need for VAPA awareness, with an emphasis on mycological bronchoscopic work-up.

Diaphragm Neurostimulation Assisted Ventilation in Critically Ill Patients.

Diaphragm neurostimulation consists of placing electrodes directly on or in proximity to the phrenic nerve(s) to elicit diaphragmatic contractions. Since its initial description in the 18th century, indications have shifted from cardiopulmonary resuscitation to long-term ventilatory support. Recently, the technical development of devices for temporary diaphragm neurostimulation has opened up the possibility of a new era for the management of mechanically ventilated patients. Combining positive pressure ventilation with diaphragm neurostimulation offers a potentially promising new approach to the delivery of mechanical ventilation which may benefit multiple organ systems. Maintaining diaphragm contractions during ventilation may attenuate diaphragm atrophy and accelerate weaning from mechanical ventilation. Preventing atelectasis and preserving lung volume can reduce lung stress and strain and improve homogeneity of ventilation, potentially mitigating ventilator-induced lung injury. Furthermore, restoring the thoracoabdominal pressure gradient generated by diaphragm contractions may attenuate the drop in cardiac output induced by positive pressure ventilation. Experimental evidence suggests diaphragm neurostimulation may prevent neuroinflammation associated with mechanical ventilation. This review describes the historical development and evolving approaches to diaphragm neurostimulation during mechanical ventilation and surveys the potential mechanisms of benefit. The review proposes a research agenda and offers perspectives for the future of diaphragm neurostimulation assisted mechanical ventilation for critically ill patients.

Skeletal Muscle Myokine Expression in Critical Illness, Association With Outcome and Impact of Therapeutic Interventions.

Context: Muscle expresses and secretes several myokines that bring about benefits in distant organs. Objective: We investigated the impact of critical illness on muscular expression of irisin, kynurenine aminotransferases, and amylase; association with clinical outcome; and impact of interventions that attenuate muscle wasting/weakness. Methods: We studied critically ill patients who participated in 2 randomized controlled trials (EPaNIC/NESCI) and documented time profiles in critically ill mice. Included in the study were 174 intensive care unit (ICU) patients (day 8 ± 1) vs 19 matched controls, and 60 mice subjected to surgery/sepsis vs 60 pair-fed healthy mice. Interventions studied included 7-day neuromuscular electrical stimulation (NMES), and withholding parenteral nutrition (PN) in the first ICU week (late PN) vs early PN. The main outcome measures were FNDC5 (irisin- precursor), KYAT1, KYAT3, and amylase mRNA expression in skeletal muscle. Results: Critically ill patients showed 34% to 80% lower mRNA expression of FNDC5, KYAT1, and amylases than controls (P < .0001). Critically ill mice showed time-dependent reductions in all mRNAs compared with healthy mice (P ≤ .04). The lower FNDC5 expression in patients was independently associated with a higher ICU mortality (P = .015) and ICU-acquired weakness (P = .012), whereas the lower amylase expression in ICU survivors was independently associated with a longer ICU stay (P = .0060). Lower amylase expression was independently associated with a lower risk of death (P = .048), and lower KYAT1 expression with a lower risk of weakness (P = .022). NMES increased FNDC5 expression compared with unstimulated muscle (P = .016), and late PN patients had a higher KYAT1 expression than early PN patients (P = .022). Conclusion: Expression of the studied myokines was affected by critical illness and associated with clinical outcomes, with limited effects of interventions that attenuate muscle wasting or weakness.

Occurrence Rate and Outcomes of Weaning Groups According to a Refined Weaning Classification: A Retrospective Observational Study.

OBJECTIVES: The weaning according to a new definition (WIND) classification groups mechanically ventilated (MV) patients into "short weaning," "difficult weaning," "prolonged weaning," and "no weaning." The aims of the study were: 1) to describe the weaning group distribution, 2) to evaluate if "short weaning" patients can be divided into groups with distinct characteristics and outcomes depending on the MV duration, and 3) to study 1-year outcomes related to weaning groups. DESIGN: Retrospective observational study. SETTING: Tertiary center with a mixed, mainly surgical ICU population. PATIENTS: MV patients admitted between April 11, 2018, and April 10, 2019. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A refined WIND classification was used, dividing "short weaning" patients into patients MV less than or equal to 24 hours, "short weaning a," and those MV greater than 24 hours, "short weaning b." Data were collected from electronic medical records. Of 1,801 MV patients, 65% were categorized as "short weaning a," 13% "short weaning b," 8% "difficult weaning," 6% "prolonged weaning," and 8% "no weaning." "Short weaning a" patients were older, more frequently male, and had lower disease severity compared with "short weaning b." Weaning duration (days: 0 [0-0] to 14 [10-21]), weaning success rate (99-69%), ICU length of stay (days: 2 [1-4] to 28 [19-48]), ICU mortality (1-37%), and hospital length of stay (days: 10 [7-18] to 48 [27-89]) and hospital mortality (4-42%; all p < 0.01) increasingly worsened from "short weaning a" to "prolonged weaning." One-year mortality increased from "short weaning a" (9%) to "short weaning b" (27%), "difficult weaning" (39%), and "prolonged weaning" (49%). In adjusted analyses, weaning groups remained independently associated with 1-year mortality. CONCLUSIONS: The high proportion of "short weaning" patients in this mainly surgical ICU population could be divided into two groups with distinct characteristics. This refined WIND classification allowed to enhance prognostication, also beyond hospitalization, highlighting the need to further optimize the weaning process.

Comparative outcomes of extracorporeal membrane oxygenation for COVID-19 delivered in experienced European centres during successive SARS-CoV-2 variant outbreaks (ECMO-SURGES): an international, multicentre, retrospective cohort study.

BACKGROUND: To inform future research and practice, we aimed to investigate the outcomes of patients who received extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome (ARDS) due to different variants of SARS-CoV-2. METHODS: This retrospective study included consecutive adult patients with laboratory-confirmed SARS-CoV-2 infection who received ECMO for ARDS in 21 experienced ECMO centres in eight European countries (Austria, Belgium, England, France, Germany, Italy, Portugal, and Spain) between Jan 1, 2020, and Sept 30, 2021. We collected data on patient characteristics, clinical status, and management before and after the initiation of ECMO. Participants were grouped according to SARS-CoV-2 variant (wild type, alpha, delta, or other) and period of the pandemic (first [Jan 1-June 30] and second [July 1-Dec 31] semesters of 2020, and first [Jan 1-June 30] and second [July 1-Sept 30] semesters of 2021). Descriptive statistics and Kaplan-Meier survival curves were used to analyse evolving characteristics, management, and patient outcomes over the first 2 years of the pandemic, and independent risk factors of mortality were determined using multivariable Cox regression models. The primary outcome was mortality 90 days after the initiation of ECMO, with follow-up to Dec 30, 2021. FINDINGS: ECMO was initiated in 1345 patients. Patient characteristics and management were similar for the groups of patients infected with different variants, except that those with the delta variant had a younger median age and less hypertension and diabetes. 90-day mortality was 42% (569 of 1345 patients died) overall, and 43% (297/686) in patients infected with wild-type SARS-CoV-2, 39% (152/391) in those with the alpha variant, 40% (78/195) in those with the delta variant, and 58% (42/73) in patients infected with other variants (mainly beta and gamma). Mortality was 10% higher (50%) in the second semester of 2020, when the wild-type variant was still prevailing, than in other semesters (40%). Independent predictors of mortality were age, immunocompromised status, a longer time from intensive care unit admission to intubation, need for renal replacement therapy, and higher Sequential Organ Failure Assessment haemodynamic component score, partial pressure of arterial carbon dioxide, and lactate concentration before ECMO. After adjusting for these variables, mortality was significantly higher with the delta variant than with the other variants, the wild-type strain being the reference. INTERPRETATION: Although crude mortality did not differ between variants, adjusted risk of death was highest for patients treated with ECMO infected with the delta variant of SARS-CoV-2. The higher virulence and poorer outcomes associated with the delta strain might relate to higher viral load and increased inflammatory response syndrome in infected patients, reinforcing the need for a higher rate of vaccination in the population and updated selection criteria for ECMO, should a new and highly virulent strain of SARS-CoV-2 emerge in the future. Mortality was noticeably lower than in other large, multicentre series of patients who received ECMO for COVID-19, highlighting the need to concentrate resources at experienced centres. FUNDING: None.

Impact of BMI on outcomes in respiratory ECMO: an ELSO registry study.

PURPOSE: The impact of body mass index (BMI) on outcomes in respiratory failure necessitating extracorporeal membrane oxygenation (ECMO) has been poorly described. We aimed to assess: (i) whether adults with class II obesity or more (BMI ≥ 35 kg/m2) have worse outcomes than lean counterparts, (ii) the form of the relationship between BMI and outcomes, (iii) whether a cutoff marking futility can be identified. METHODS: A retrospective analysis of the Extracorporeal Life Support Organization (ELSO) Registry from 1/1/2010 to 31/12/2020 was conducted. Impact of BMI ≥ 35 kg/m2 was assessed with propensity-score (PS) matching, inverse propensity-score weighted (IPSW) and multivariable models (MV), adjusting for a priori identified confounders. Primary outcome was in-hospital mortality. The form of the relationship between BMI and outcomes was studied with generalized additive models. Outcomes across World Health Organisation (WHO)-defined BMI categories were compared. RESULTS: Among 18,529 patients, BMI ≥ 35 kg/m2 was consistently associated with reduced in-hospital mortality [PS-matched: OR: 0.878(95%CI 0.798-0.966), p = 0.008; IPSW: OR: 0.899(95%CI 0.827-0.979), p = 0.014; MV: OR: 0.900(95%CI 0.834-0.971), p = 0.007] and shorter hospital length of stays. In patients with BMI ≥ 35 kg/m2, cardiovascular (17.3% versus 15.3%), renal (37% versus 30%) and device-related complications (25.7% versus 20.6%) increased, whereas pulmonary complications decreased (7.6% versus 9.3%). These findings were independent of confounders throughout PS-matched, IPSW and MV models. The relationship between BMI and outcomes was non-linear and no cutoff for futility was identified. CONCLUSION: Patients with obesity class II or more treated with ECMO for respiratory failure have lower mortality risk and shorter stays, despite increased cardiovascular, device-related, and renal complications. No upper limit of BMI indicating futility of ECMO treatment could be identified. BMI as single parameter should not be a contra-indication for respiratory ECMO.

Do Cerebral Cortex Perfusion, Oxygen Delivery, and Oxygen Saturation Responses Measured by Near-Infrared Spectroscopy Differ Between Patients Who Fail or Succeed in a Spontaneous Breathing Trial? A Prospective Observational Study.

BACKGROUND: Alterations in perfusion to the brain during the transition from mechanical ventilation (MV) to a spontaneous breathing trial (SBT) remain poorly understood. The aim of the study was to determine whether changes in cerebral cortex perfusion, oxygen delivery (DO2), and oxygen saturation (%StiO2) during the transition from MV to an SBT differ between patients who succeed or fail an SBT. METHODS: This was a single-center prospective observational study conducted in a 16-bed medical intensive care unit of the University Hospital Leuven, Belgium. Measurements were performed in 24 patients receiving MV immediately before and at the end of a 30-min SBT. Blood flow index (BFI), DO2, and %StiO2 in the prefrontal cortex, scalene, rectus abdominis, and thenar muscle were simultaneously assessed by near-infrared spectroscopy using the tracer indocyanine green dye. Cardiac output, arterial blood gases, and systemic oxygenation were also recorded. RESULTS: During the SBT, prefrontal cortex BFI and DO2 responses did not differ between SBT-failure and SBT-success groups (p > 0.05). However, prefrontal cortex %StiO2 decreased in six of eight patients (75%) in the SBT-failure group (median [interquartile range 25-75%]: MV = 57.2% [49.1-61.7] vs. SBT = 51.0% [41.5-62.5]) compared to 3 of 16 patients (19%) in the SBT-success group (median [interquartile range 25-75%]: MV = 65.0% [58.6-68.5] vs. SBT = 65.1% [59.5-71.1]), resulting in a significant differential %StiO2 response between groups (p = 0.031). Similarly, a significant differential response in thenar muscle %StiO2 (p = 0.018) was observed between groups. A receiver operating characteristic analysis identified a decrease in prefrontal cortex %StiO2 > 1.6% during the SBT as an optimal cutoff, with a sensitivity of 94% and a specificity of 75% to predict SBT failure and an area under the curve of 0.79 (95% CI: 0.55-1.00). Cardiac output, systemic oxygenation, scalene, and rectus abdominis BFI, DO2, and %StiO2 responses did not differ between groups (p > 0.05); however, during the SBT, a significant positive association in prefrontal cortex BFI and partial pressure of arterial carbon dioxide was observed only in the SBT-success group (SBT success: Spearman's ρ = 0.728, p = 0.002 vs. SBT failure: ρ = 0.048, p = 0.934). CONCLUSIONS: This study demonstrated a reduced differential response in prefrontal cortex %StiO2 in the SBT-failure group compared with the SBT-success group possibly due to the insufficient increase in prefrontal cortex perfusion in SBT-failure patients. A > 1.6% drop in prefrontal cortex %StiO2 during SBT was sensitive in predicting SBT failure. Further research is needed to validate these findings in a larger population and to evaluate whether cerebral cortex %StiO2 measurements by near-infrared spectroscopy can assist in the decision-making process on liberation from MV.

Comparing two types of loading during inspiratory muscle training in patients with weaning difficulties: An exploratory study.

BACKGROUND: Inspiratory muscle training improves respiratory muscle function and may improve weaning outcomes in patients with weaning difficulties. Compared to the commonly used pressure threshold loading, tapered flow resistive loading better accommodates pressure-volume relationships of the respiratory muscles, which might help to facilitate application of external loads and optimise training responses. OBJECTIVE: The objective of this study was to compare acute breathing pattern responses and perceived symptoms during an inspiratory muscle training session performed against identical external loading provided as pressure threshold loading or as tapered flow resistive loading. We hypothesised that for a given loading, tapered flow resistive loading would allow larger volume expansion and higher inspiratory flow responses and consequently higher external work of breathing and power than pressure threshold loading and that subsequently patients perceived fewer symptoms during tapered flow resistive loading than during pressure threshold loading. METHODS: In this exploratory study, 21 patients (maximal inspiratory pressure: 35 ± 14 cmH2O and vital capacity:0.85 L±0.37 L) performed two training sessions against external loads equalling 42 ± 15% of maximal inspiratory pressure provided either as pressure threshold loading or as tapered flow resistive loading. During these training sessions, breath-by-breath data of breathing parameters were collected, and patients rated their perceived breathing effort, dyspnoea, and unpleasantness. RESULTS: Compared to pressure threshold loading, tapered flow resistive loading allowed significantly larger volume expansion (0.53 ± 0.28 L versus 0.41 ± 0.20 L, p < 0.01) and inspiratory flow responses (0.43 ± 0.20 L/s versus 0.33 ± 0.16 L/s, p = 0.01). Tapered flow resistive loading was perceived as less unpleasant (3.1 ± 1.9 versus 3.8 ± 2.4, p = 0.048). No significant differences in breathing effort, dyspnoea, work of breathing, and power were observed. CONCLUSIONS: For a given loading, inspiratory muscle training with tapered flow resistive loading allowed larger volume expansion and higher inspiratory flow responses than pressure threshold loading, which led patients to perceive tapered flow resistive loading as less unpleasant. This might help us to facilitate early implementation of inspiratory muscle training in patients with weaning difficulties. CLINICAL TRIAL REGISTRATION NUMBER: Clinicaltrials.gov identifier: NCT03240263.

Outcomes of Extracorporeal Membrane Oxygenation in COVID-19-Induced Acute Respiratory Distress Syndrome: An Inverse Probability Weighted Analysis.

Although venovenous extracorporeal membrane oxygenation (VV ECMO) has been used in case of COVID-19 induced acute respiratory distress syndrome (ARDS), outcomes and criteria for its application should be evaluated. OBJECTIVES: To describe patient characteristics and outcomes in patients receiving VV ECMO due to COVID-19-induced ARDS and to assess the possible impact of COVID-19 on mortality. DESIGN SETTING AND PARTICIPANTS: Multicenter retrospective study in 15 ICUs worldwide. All adult patients (> 18 yr) were included if they received VV ECMO with ARDS as main indication. Two groups were created: a COVID-19 cohort from March 2020 to December 2020 and a "control" non-COVID ARDS cohort from January 2018 to July 2019. MAIN OUTCOMES AND MEASURES: Collected data consisted of patient demographics, baseline variables, ECMO characteristics, and patient outcomes. The primary outcome was 60-day mortality. Secondary outcomes included patient characteristics, COVID-19-related therapies before and during ECMO and complication rate. To assess the influence of COVID-19 on mortality, inverse probability weighted (IPW) analyses were used to correct for predefined confounding variables. RESULTS: A total of 193 patients with COVID-19 received VV ECMO. The main indication for VV ECMO consisted of refractory hypoxemia, either isolated or combined with refractory hypercapnia. Complications with the highest occurrence rate included hemorrhage, an additional infectious event or acute kidney injury. Mortality was 35% and 45% at 28 and 60 days, respectively. Those mortality rates did not differ between the first and second waves of COVID-19 in 2020. Furthermore, 60-day mortality was equal between patients with COVID-19 and non-COVID-19-associated ARDS receiving VV ECMO (hazard ratio 60-d mortality, 1.27; 95% CI, 0.82-1.98; p = 0.30). CONCLUSIONS AND RELEVANCE: Mortality for patients with COVID-19 who received VV ECMO was similar to that reported in other COVID-19 cohorts, although no differences were found between the first and second waves regarding mortality. In addition, after IPW, mortality was independent of the etiology of ARDS.

Severe COVID-19 patients display hyper-activated NK cells and NK cell-platelet aggregates.

COVID-19 is characterised by a broad spectrum of clinical and pathological features. Natural killer (NK) cells play an important role in innate immune responses to viral infections. Here, we analysed the phenotype and activity of NK cells in the blood of COVID-19 patients using flow cytometry, single-cell RNA-sequencing (scRNA-seq), and a cytotoxic killing assay. In the plasma of patients, we quantified the main cytokines and chemokines. Our cohort comprises COVID-19 patients hospitalised in a low-care ward unit (WARD), patients with severe COVID-19 disease symptoms hospitalised in intensive care units (ICU), and post-COVID-19 patients, who were discharged from hospital six weeks earlier. NK cells from hospitalised COVID-19 patients displayed an activated phenotype with substantial differences between WARD and ICU patients and the timing when samples were taken post-onset of symptoms. While NK cells from COVID-19 patients at an early stage of infection showed increased expression of the cytotoxic molecules perforin and granzyme A and B, NK cells from patients at later stages of COVID-19 presented enhanced levels of IFN-γ and TNF-α which were measured ex vivo in the absence of usual in vitro stimulation. These activated NK cells were phenotyped as CD49a+CD69a+CD107a+ cells, and their emergence in patients correlated to the number of neutrophils, and plasma IL-15, a key cytokine in NK cell activation. Despite lower amounts of cytotoxic molecules in NK cells of patients with severe symptoms, majority of COVID-19 patients displayed a normal cytotoxic killing of Raji tumour target cells. In vitro stimulation of patients blood cells by IL-12+IL-18 revealed a defective IFN-γ production in NK cells of ICU patients only, indicative of an exhausted phenotype. ScRNA-seq revealed, predominantly in patients with severe COVID-19 disease symptoms, the emergence of an NK cell subset with a platelet gene signature that we identified by flow and imaging cytometry as aggregates of NK cells with CD42a+CD62P+ activated platelets. Post-COVID-19 patients show slow recovery of NK cell frequencies and phenotype. Our study points to substantial changes in NK cell phenotype during COVID-19 disease and forms a basis to explore the contribution of platelet-NK cell aggregates to antiviral immunity against SARS-CoV-2 and disease pathology.