Prospective, randomized, controlled clinical trial comparing traditional versus reduced tidal volume ventilation in acute respiratory distress syndrome patients

ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies

The aim of these guidelines is to update the 2017 clinical practice guideline (CPG) of the European Society of Intensive Care Medicine (ESICM). The scope of this CPG is limited to adult patients and to non-pharmacological respiratory support strategies across different aspects of acute respiratory distress syndrome (ARDS), including ARDS due to coronavirus disease 2019 (COVID-19). These guidelines were formulated by an international panel of clinical experts, one methodologist and patients' representatives on behalf of the ESICM. The review was conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations and the quality of reporting of each study based on the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network guidelines. The CPG addressed 21 questions and formulates 21 recommendations on the following domains: (1) definition; (2) phenotyping, and respiratory support strategies including (3) high-flow nasal cannula oxygen (HFNO); (4) non-invasive ventilation (NIV); (5) tidal volume setting; (6) positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM); (7) prone positioning; (8) neuromuscular blockade, and (9) extracorporeal life support (ECLS). In addition, the CPG includes expert opinion on clinical practice and identifies the areas of future research.

ARDS: hidden perils of an overburdened diagnosis

A diagnosis of ARDS serves as a pretext for several perilous clinical practices. Clinical trials demonstrated that tidal volume 12 ml/kg increases patient mortality, but 6 ml/kg has not proven superior to 11 ml/kg or anything in between. Present guidelines recommend 4 ml/kg, which foments severe air hunger, leading to prescription of hazardous (yet ineffective) sedatives, narcotics and paralytic agents. Inappropriate lowering of tidal volume also fosters double triggering, which promotes alveolar overdistention and lung injury. Successive panels have devoted considerable energy to developing a more precise definition of ARDS to homogenize the recruitment of patients into clinical trials. Each of three pillars of the prevailing Berlin definition is extremely flimsy and the source of confusion and unscientific practices. For doctors at the bedside, none of the revisions have enhanced patient care over that using the original 1967 description of Ashbaugh and colleagues. Bedside doctors are better advised to diagnose ARDS on the basis of pattern recognition and instead concentrate their vigilance on resolving the numerous hidden dangers that follow inevitably once a diagnosis has been made.

Intermediate tidal volume is an acceptable option for ventilated patients with acute respiratory distress syndrome

Objective

Evidence only proves low surpasses high tidal volume (V _T) for acute respiratory distress syndrome (ARDS). Intermediate V _T is a common setting for ARDS patients and has been demonstrated as effective as low V _T in non-ARDS patients. The effectiveness of intermediate V _T in ARDS has not been studied and is the objective of this study.

Design

A retrospective cohort study.

Setting

Five ICUs with their totally 130 beds in Taiwan.

Patients or participants

ARDS patients under invasive ventilation.

Interventions

No.

Main variables of interest

28-D mortality.

Result

Totally 382 patients, with 6958 ventilator settings eligible for lung protection, were classified into low (mean V _T = 6.7 ml/kg), intermediate (mean V _T = 8.9 ml/kg) and high (mean V _T = 11.2 ml/kg) V _T groups. With similar baseline ARDS and ICU severities, intermediate and low V _T groups did not differ in 28-D mortality (47% vs. 63%, P = 0.06) or other outcomes such as 90-D mortality, ventilator-free days, ventilator-dependence rate. Multivariate analysis revealed high V _T was independently associated with 28-D and 90-D mortality, but intermediate V _T was not significantly associated with 28-D mortality (HR 1.34, CI 0.92-1.97, P = 0.13) or 90-D mortality. When the intermediate and low V _T groups were matched in propensity scores (n = 66 for each group), their outcomes were also not significantly different.

Conclusion

Intermediate V _T, with its outcomes similar to small V _T, is an acceptable option for ventilated ARDS patients. This conclusion needs verification through clinical trials.

Through the Looking Glass: The Paradoxical Evolution of Targeted Temperature Management for Comatose Survivors of Cardiac Arrest

For the past two decades, targeted temperature management (TTM) has been a staple in the care of comatose survivors following cardiac arrest. However, recent clinical trials have failed to replicate the benefit seen in earlier studies, bringing into question the very existence of such clinical practice. In this review, we explore clinical scenarios within critical care that appeared to share a similar fate, but in actuality changed the landscape of practice in a modern world. Accordingly, clinicians may apply these lessons to the utilization of TTM among comatose survivors following cardiac arrest, potentially paving way for a re-framing of clinical care amidst an environment where current data appears upside down in comparison to past successes.

COVID-19-Related ARDS: Key Mechanistic Features and Treatments

Acute respiratory distress syndrome (ARDS) is a heterogeneous syndrome historically characterized by the presence of severe hypoxemia, high-permeability pulmonary edema manifesting as diffuse alveolar infiltrate on chest radiograph, and reduced compliance of the integrated respiratory system as a result of widespread compressive atelectasis and fluid-filled alveoli. Coronavirus disease 19 (COVID-19)-associated ARDS (C-ARDS) is a novel etiology caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that may present with distinct clinical features as a result of the viral pathobiology unique to SARS-CoV-2. In particular, severe injury to the pulmonary vascular endothelium, accompanied by the presence of diffuse microthrombi in the pulmonary microcirculation, can lead to a clinical presentation in which the severity of impaired gas exchange becomes uncoupled from lung capacity and respiratory mechanics. The purpose of this review is to highlight the key mechanistic features of C-ARDS and to discuss the implications these features have on its treatment. In some patients with C-ARDS, rigid adherence to guidelines derived from clinical trials in the pre-COVID era may not be appropriate.

Myths and Misconceptions of Airway Pressure Release Ventilation: Getting Past the Noise and on to the Signal

In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): “Scientific orthodoxy kills truth”. In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of “lung protective” ventilation. Unfortunately, inadequacies of the current conceptual model–that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the “baby lung” - is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controversial modes of mechanical ventilation that shows promise in experimental and clinical data. Over the last 3 decades APRV has evolved from a rescue strategy to a preemptive lung injury prevention approach with potential to stabilize the lung and restore alveolar homogeneity. However, several obstacles have so far impeded the evaluation of APRV’s clinical efficacy in large, randomized trials. For instance, there is no universally accepted standardized method of setting APRV and thus, it is not established whether its effects on clinical outcomes are due to the ventilator mode per se or the method applied. In addition, one distinctive issue that hinders proper scientific evaluation of APRV is the ubiquitous presence of myths and misconceptions repeatedly presented in the literature. In this review we discuss some of these misleading notions and present data to advance scientific discourse around the uses and misuses of APRV in the current literature.

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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40560-022-00615-6.

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.

I-SPY COVID adaptive platform trial for COVID-19 acute respiratory failure: rationale, design and operations

INTRODUCTION

The COVID-19 pandemic brought an urgent need to discover novel effective therapeutics for patients hospitalised with severe COVID-19. The Investigation of Serial studies to Predict Your Therapeutic Response with Imaging And moLecular Analysis (ISPY COVID-19 trial) was designed and implemented in early 2020 to evaluate investigational agents rapidly and simultaneously on a phase 2 adaptive platform. This manuscript outlines the design, rationale, implementation and challenges of the ISPY COVID-19 trial during the first phase of trial activity from April 2020 until December 2021.

METHODS AND ANALYSIS

The ISPY COVID-19 Trial is a multicentre open-label phase 2 platform trial in the USA designed to evaluate therapeutics that may have a large effect on improving outcomes from severe COVID-19. The ISPY COVID-19 Trial network includes academic and community hospitals with significant geographical diversity across the country. Enrolled patients are randomised to receive one of up to four investigational agents or a control and are evaluated for a family of two primary outcomes-time to recovery and mortality. The statistical design uses a Bayesian model with 'stopping' and 'graduation' criteria designed to efficiently discard ineffective therapies and graduate promising agents for definitive efficacy trials. Each investigational agent arm enrols to a maximum of 125 patients per arm and is compared with concurrent controls. As of December 2021, 11 investigational agent arms had been activated, and 8 arms were complete. Enrolment and adaptation of the trial design are ongoing.

ETHICS AND DISSEMINATION

ISPY COVID-19 operates under a central institutional review board via Wake Forest School of Medicine IRB00066805. Data generated from this trial will be reported in peer-reviewed medical journals.

TRIAL REGISTRATION NUMBER

NCT04488081.

Usefulness of low tidal volume ventilation strategy for patients with acute respiratory distress syndrome: a systematic review and meta-analysis

The effects of lower tidal volume ventilation (LTV) were controversial for patients with acute respiratory distress syndrome (ARDS). This systematic review and meta-analysis aimed to evaluate the use of LTV strategy in patients with ARDS. We performed a literature search on MEDLINE, CENTRAL, EMBASE, CINAHL, “Igaku-Chuo-Zasshi”, clinical trial registration sites, and the reference of recent guidelines. We included randomized controlled trials (RCTs) to compare the LTV strategy with the higher tidal volume ventilation (HTV) strategy in patients with ARDS. Two authors independently evaluated the eligibility of studies and extracted the data. The primary outcomes were 28-day mortality. We used the GRADE methodology to assess the certainty of evidence. Among the 19,864 records screened, 13 RCTs that recruited 1874 patients were included in our meta-analysis. When comparing LTV (4–8 ml/kg) versus HTV (> 8 ml/kg), the pooled risk ratio for 28-day mortality was 0.79 (11 studies, 95% confidence interval [CI] 0.66–0.94, I² = 43%, n = 1795, moderate certainty of evidence). Subgroup-analysis by combined high positive end-expiratory pressure with LTV showed interaction (P = 0.01). Our study indicated that ventilation with LTV was associated with reduced risk of mortality in patients with ARDS when compared with HTV.

Trial registration: UMIN-CTR (UMIN000041071).

The Impact of Sample Size Misestimations on the Interpretation of ARDS Trials: Systematic Review and Meta-analysis

BACKGROUND

Indeterminate randomized controlled trials (RCTs) in ARDS may arise from sample size misspecification, leading to abandonment of efficacious therapies.

RESEARCH QUESTIONS

If evidence exists for sample size misspecification in ARDS RCTs, has this led to rejection of potentially beneficial therapies? Does evidence exist for prognostic enrichment in RCTs using mortality as a primary outcome?

STUDY DESIGN AND METHODS

We identified 150 ARDS RCTs commencing recruitment after the 1994 American European Consensus Conference ARDS definition and published before October 31, 2020. We examined predicted-observed sample size, predicted-observed control event rate (CER), predicted-observed average treatment effect (ATE), and the relationship between observed CER and observed ATE for RCTs with mortality and nonmortality primary outcome measures. To quantify the strength of evidence, we used Bayesian-averaged meta-analysis, trial sequential analysis, and Bayes factors.

RESULTS

Only 84 of 150 RCTs (56.0%) reported sample size estimations. In RCTs with mortality as the primary outcome, CER was overestimated in 16 of 28 RCTs (57.1%). To achieve predicted ATE, interventions needed to prevent 40.8% of all deaths, compared with the original prediction of 29.3%. Absolute reduction in mortality ≥ 10% was observed in 5 of 28 RCTs (17.9%), but predicted in 21 of 28 RCTs (75%). For RCTs with mortality as the primary outcome, no association was found between observed CER and observed ATE (pooled OR: β = -0.04; 95% credible interval, -0.18 to 0.09). We identified three interventions that are not currently standard of care with a Bayesian-averaged effect size of > 0.20 and moderate strength of existing evidence: corticosteroids, airway pressure release ventilation, and noninvasive ventilation.

INTERPRETATION

Reporting of sample size estimations was inconsistent in ARDS RCTs, and misspecification of CER and ATE was common. Prognostic enrichment strategies in ARDS RCTs based on all-cause mortality are unlikely to be successful. Bayesian methods can be used to prioritize interventions for future effectiveness RCTs.

The role of mechanical ventilation in primary graft dysfunction in the postoperative lung transplant recipient: A single center study and literature review

Background

Primary graft dysfunction (PGD) is still a major complication in patients undergoing lung transplantation (LTx). Much is unknown about the effect of postoperative mechanical ventilation on outcomes, with debate on the best approach to ventilation.

Aim/Purpose

The goal of this study was to generate hypotheses on the association between postoperative mechanical ventilation settings and allograft size matching in PGD development.

Method

This is a retrospective study of LTx patients between September 2011 and September 2018 (n = 116). PGD was assessed according to the International Society of Heart and Lung Transplantation (ISHLT) criteria. Data were collected from medical records, including chest x‐ray assessments, blood gas analysis, mechanical ventilator parameters and spirometry.

Results

Positive end‐expiratory pressures (PEEP) of 5 cm H₂O were correlated with lower rates of grade 3 PGD. Graft size was important as tidal volumes calculated according to the recipient yielded greater rates of PGD when low volumes were used, a correlation that was lost when donor metrics were used.

Conclusion

Our results highlight a need for greater investigation of the role donor characteristics play in determining post‐operative ventilation of a lung transplant recipient. The mechanical ventilation settings on postoperative LTx recipients may have an implication for the development of acute graft dysfunction. Severe PGD was associated with the use of a PEEP higher than 5 and lower tidal volumes and oversized lungs were associated with lower long‐term mortality. Lack of association between ventilatory settings and survival may point to the importance of other variables than ventilation in the development of PGD.

An Exploratory Analysis of the Association between Hypercapnia and Hospital Mortality in Critically Ill Patients with Sepsis

Rationale: Hypercapnia may affect the outcome of sepsis. Very few clinical studies conducted in noncritically ill patients have investigated the effects of hypercapnia and hypercapnic acidemia in the context of sepsis. The effect of hypercapnia in critically ill patients with sepsis remains inadequately studied. Objectives: To investigate the association of hypercapnia with hospital mortality in critically ill patients with sepsis. Methods: This is a retrospective study conducted in three tertiary public hospitals. Critically ill patients with sepsis from three intensive care units between January 2011 and May 2019 were included. Five cohorts (exposure of at least 24, 48, 72, 120, and 168 hours) were created to account for immortal time bias and informative censoring. The association between hypercapnia exposure and hospital mortality was assessed with multivariable models. Subgroup analyses compared ventilated versus nonventilated and pulmonary versus nonpulmonary sepsis patients. Results: We analyzed 84,819 arterial carbon dioxide pressure measurements in 3,153 patients (57.6% male; median age was 62.5 years). After adjustment for key confounders, both in mechanically ventilated and nonventilated patients and in patients with pulmonary or nonpulmonary sepsis, there was no independent association of hypercapnia with hospital mortality. In contrast, in ventilated patients, the presence of prolonged exposure to both hypercapnia and acidemia was associated with increased mortality (highest odds ratio of 16.5 for ⩾120 hours of potential exposure; P = 0.007). Conclusions: After adjustment, isolated hypercapnia was not associated with increased mortality in patients with sepsis, whereas prolonged hypercapnic acidemia was associated with increased risk of mortality. These hypothesis-generating observations suggest that as hypercapnia is not an independent risk factor for mortality, trials of permissive hypercapnia avoiding or minimizing acidemia in sepsis may be safe.

Hypercapnia from Physiology to Practice

Acute hypercapnic ventilatory failure is becoming more frequent in critically ill patients. Hypercapnia is the elevation in the partial pressure of carbon dioxide (PaCO₂) above 45 mmHg in the bloodstream. The pathophysiological mechanisms of hypercapnia include the decrease in minute volume, an increase in dead space, or an increase in carbon dioxide (CO₂) production per sec. They generate a compromise at the cardiovascular, cerebral, metabolic, and respiratory levels with a high burden of morbidity and mortality. It is essential to know the triggers to provide therapy directed at the primary cause and avoid possible complications.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members.As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

The relationship of tidal volume and driving pressure with mortality in hypoxic patients receiving mechanical ventilation

PURPOSE

To determine whether tidal volume/predicted body weight (TV/PBW) or driving pressure (DP) are associated with mortality in a heterogeneous population of hypoxic mechanically ventilated patients.

METHODS

A retrospective cohort study involving 18 intensive care units included consecutive patients ≥18 years old, receiving mechanical ventilation for ≥3 days, with a PaO2/FiO2 ratio ≤300 mmHg, whether or not they met full criteria for ARDS. The main outcome was hospital mortality. Multiple logistic regression (MLR) incorporated TV/PBW, DP, and potential confounders including age, APACHE IVa® predicted hospital mortality, respiratory system compliance (CRS), and PaO2/FiO2. Predetermined strata of TV/PBW were compared using MLR.

RESULTS

Our cohort comprised 5,167 patients with mean age 61.9 years, APACHE IVa® score 79.3, PaO2/FiO2 166 mmHg and CRS 40.5 ml/cm H2O. Regression analysis revealed that patients receiving DP one standard deviation above the mean or higher (≥19 cmH20) had an adjusted odds ratio for mortality (ORmort) = 1.10 (95% CI: 1.06-1.13, p = 0.009). Regression analysis showed a U-shaped relationship between strata of TV/PBW and adjusted mortality. Using TV/PBW 4-6 ml/kg as the referent group, patients receiving >10 ml/kg had similar adjusted ORmort, but those receiving 6-7, 7-8 and 8-10 ml/kg had lower adjusted ORmort (95%CI) of 0.81 (0.65-1.00), 0.78 (0.63-0.97) and 0.80 0.67-1.01) respectively. The adjusted ORmort in patients receiving 4-6 ml/kg was 1.26 (95%CI: 1.04-1.52) compared to patients receiving 6-10 ml/kg.

CONCLUSIONS

Driving pressures ≥19 cmH2O were associated with increased adjusted mortality. TV/PBW 4-6ml/kg were used in less than 15% of patients and associated with increased adjusted mortality compared to TV/PBW 6-10 ml/kg used in 82% of patients. Prospective clinical trials are needed to prove whether limiting DP or the use of TV/PBW 6-10 ml/kg versus 4-6 ml/kg benefits mortality.

Effect of Lowering Vt on Mortality in Acute Respiratory Distress Syndrome Varies with Respiratory System Elastance

Rationale: If the risk of ventilator-induced lung injury in acute respiratory distress syndrome (ARDS) is causally determined by driving pressure rather than by Vt, then the effect of ventilation with lower Vt on mortality would be predicted to vary according to respiratory system elastance (Ers). Objectives: To determine whether the mortality benefit of ventilation with lower Vt varies according to Ers. Methods: In a secondary analysis of patients from five randomized trials of lower- versus higher-Vt ventilation strategies in ARDS and acute hypoxemic respiratory failure, the posterior probability of an interaction between the randomized Vt strategy and Ers on 60-day mortality was computed using Bayesian multivariable logistic regression. Measurements and Main Results: Of 1,096 patients available for analysis, 416 (38%) died by Day 60. The posterior probability that the mortality benefit from lower-Vt ventilation strategies varied with Ers was 93% (posterior median interaction odds ratio, 0.80 per cm H₂O/[ml/kg]; 90% credible interval, 0.63-1.02). Ers was classified as low (<2 cm H₂O/[ml/kg], n = 321, 32%), intermediate (2-3 cm H₂O/[ml/kg], n = 475, 46%), and high (>3 cm H₂O/[ml/kg], n = 224, 22%). In these groups, the posterior probabilities of an absolute risk reduction in mortality ≥ 1% were 55%, 82%, and 92%, respectively. The posterior probabilities of an absolute risk reduction ≥ 5% were 29%, 58%, and 82%, respectively. Conclusions: The mortality benefit of ventilation with lower Vt in ARDS varies according to elastance, suggesting that lung-protective ventilation strategies should primarily target driving pressure rather than Vt.

Comparative Effectiveness of Protective Ventilation Strategies for Moderate and Severe Acute Respiratory Distress Syndrome. A Network Meta-Analysis

Rationale: Choosing the best ventilation strategy for acute respiratory distress syndrome (ARDS) is complex, yet it is highly relevant to clinicians during a respiratory pandemic. Objectives: To compare the effects of low Vt, high Vt, high positive end-expiratory pressure (PEEP), prone ventilation, high-frequency oscillation, and venovenous extracorporeal membrane oxygenation (VV ECMO) on mortality in ARDS. Methods: We performed a network meta-analysis of randomized trials. We applied the Grading of Recommendations Assessment, Development and Evaluation methodology to discern the relative effect of interventions on mortality. Measurements and Main Results: We analyzed 34 trials including 9,085 adults with primarily moderate-to-severe ARDS (median baseline Pa_O2/Fi_O2, 118; interquartile range, 110-143). Prone positioning combined with low Vt was the best strategy (risk ratio [RR], 0.74 [95% confidence interval (CI), 0.60-0.92] vs. low Vt; high certainty). VV ECMO was also rated among the best (RR, 0.78 [95% CI, 0.58-1.05] vs. low Vt; RR, 0.66; [95% CI, 0.49-0.88] vs. high Vt) but was rated with lower certainty because VV ECMO was restricted to very severe ARDS (mean baseline Pa_O2/Fi_O2<75). High PEEP combined with low Vt was rated intermediately (RR, 0.91 [95% CI, 0.81-1.03] vs. low Vt; low certainty; RR, 0.77 [95% CI, 0.65-0.91] vs. high Vt; moderate certainty). High Vt was rated worst (RR, 1.19 [95% CI, 1.02-1.37] vs. low Vt; moderate certainty), and we found no support for high-frequency oscillation or high Vt with prone ventilation. Conclusions: These findings suggest that combining low Vt with prone ventilation is associated with the greatest reduction in mortality for critically ill adults with moderate-to-severe ARDS.

Audit of low tidal volume ventilation in patients with hypoxic respiratory failure in a tertiary Australian intensive care unit

A low tidal volume ventilation (LTVV) strategy improves outcomes in patients with acute respiratory distress syndrome (ARDS). Subsequently, a LTVV strategy has become the standard of care for patients receiving mechanical ventilation. This strategy is poorly adhered to within intensive care units (ICUs). A retrospective analysis was conducted of prescribed tidal volumes in mechanically ventilated patients with hypoxic respiratory failure between April 2013 and March 2017. Data collection included the establishment of a new data-entry box for patient height in March 2016, aimed at assisting the calculation of LTVV. We reviewed 836 ICU admissions, comprising 19,884 hours of ventilation. A total of 92% of admissions lacked patient height recording. When height was recorded, 54% of hours of ventilation were LTVV adherent. Non-LTVV hours for both groups involved higher tidal volumes (38%) rather than lower tidal volumes (8%). Non-LTVV-adherent hours were significantly (P<0.001) more likely to be associated with patient mortality than LTVV-adherent hours were. For all hours of ventilation, mean tidal volume before March 2016 was significantly higher (496 (standard deviation (SD) 101) ml, compared to after March 2016 (451 (SD 107) ml, P<0.001, 95% confidence interval for true difference in means 42 to 48 ml). However, this trend gradually reversed over time. There was a clinician preference for multiples of 50 ml. There was poor adherence to LTVV strategy in patients with hypoxic respiratory failure, which was associated with an increase in patient mortality. An electronic medical record intervention was successful in producing change, but this was not sustainable over time. Clinician ventilation prescribing habits were based on numerical simplicity rather than evidence-based practice.

Bronchopleural Fistula in the Mechanically Ventilated Patient: A Concise Review

OBJECTIVE

To describe the physiology of air leak in bronchopleural fistula in mechanically ventilated patients and how understanding of its physiology drives management of positive-pressure ventilation. To provide guidance of lung isolation, mechanical ventilator, pleural catheter, and endobronchial strategies for the management of bronchopleural fistula on mechanical ventilation.

DATA SOURCES

Online search of PubMed and manual review of articles (laboratory and patient studies) was performed.

STUDY SELECTION

Articles relevant to bronchopleural fistula, mechanical ventilation in patients with bronchopleural fistula, independent lung ventilation, high-flow ventilatory modes, physiology of persistent air leak, extracorporeal membrane oxygenation, fluid dynamics of bronchopleural fistula airflow, and intrapleural catheter management were selected. Randomized trials, observational studies, case reports, and physiologic studies were included.

DATA EXTRACTION

Data from selected studies were qualitatively evaluated for this review. We included data illustrating the physiology of driving pressure across a bronchopleural fistula as well as data, largely from case reports, demonstrating management and outcomes with various ventilator modes, intrapleural catheter techniques, endoscopic placement of occlusion and valve devices, and extracorporeal membrane oxygenation. Themes related to managing persistent air leak with mechanical ventilation were reviewed and extracted.

DATA SYNTHESIS

In case reports that demonstrate different approaches to managing patients with bronchopleural fistula requiring mechanical ventilation, common themes emerge. Strategies aimed at decreasing peak inspiratory pressure, using lower tidal volumes, lowering positive end-expiratory pressure, decreasing the inspiratory time, and decreasing the respiratory rate, while minimizing negative intrapleural pressure decreases airflow across the bronchopleural fistula.

CONCLUSIONS

Mechanical ventilation and intrapleural catheter management must be individualized and aimed at reducing air leak. Clinicians should emphasize reducing peak inspiratory pressures, reducing positive end-expiratory pressure, and limiting negative intrapleural pressure. In refractory cases, clinicians can consider lung isolation, independent lung ventilation, or extracorporeal membrane oxygenation in appropriate patients as well as definitive management with advanced bronchoscopic placement of valves or occlusion devices.

Personalized Positive End-Expiratory Pressure and Tidal Volume in Acute Respiratory Distress Syndrome: Bedside Physiology-Based Approach

OBJECTIVES:

Positive end-expiratory pressure and tidal volume may have a key role for the outcome of patients with acute respiratory distress syndrome. The variety of acute respiratory distress syndrome phenotypes implies personalization of those settings. To guide personalized positive end-expiratory pressure and tidal volume, physicians need to have an in-depth understanding of the physiologic effects and bedside methods to measure the extent of these effects. In the present article, a step-by-step physiologic approach to select personalized positive end-expiratory pressure and tidal volume at the bedside is described.

DATA SOURCES:

The present review is a critical reanalysis of the traditional and latest literature on the topic.

STUDY SELECTION:

Relevant clinical and physiologic studies on positive end-expiratory pressure and tidal volume setting were reviewed.

DATA EXTRACTION:

Reappraisal of the available physiologic and clinical data.

DATA SYNTHESIS:

Positive end-expiratory pressure is aimed at stabilizing alveolar recruitment, thus reducing the risk of volutrauma and atelectrauma. Bedside assessment of the potential for lung recruitment is a preliminary step to recognize patients who benefit from higher positive end-expiratory pressure level. In patients with higher potential for lung recruitment, positive end-expiratory pressure could be selected by physiology-based methods balancing recruitment and overdistension. In patients with lower potential for lung recruitment or in shock, positive end-expiratory pressure could be maintained in the 5–8 cm H₂O range. Tidal volume induces alveolar recruitment and improves gas exchange. After setting personalized positive end-expiratory pressure, tidal volume could be based on lung inflation (collapsed lung size) respecting safety thresholds of static and dynamic lung stress. Positive end-expiratory pressure and tidal volume could be kept stable for some hours in order to allow early recognition of changes in the clinical course of acute respiratory distress syndrome but also frequently reassessed to avoid crossing of safety thresholds.

CONCLUSIONS:

The setting of personalized positive end-expiratory pressure and tidal volume based on sound physiologic bedside measures may represent an effective strategy for treating acute respiratory distress syndrome patients.

Impact of differences in acute respiratory distress syndrome randomised controlled trial inclusion and exclusion criteria: systematic review and meta-analysis

BACKGROUND

Control-arm mortality varies between acute respiratory distress syndrome (ARDS) RCTs.

METHODS

We systematically reviewed ARDS RCTs that commenced recruitment after publication of the American-European Consensus (AECC) definition (MEDLINE, Embase, and Cochrane central register of controlled trials; January 1994 to October 2020). We assessed concordance of RCT inclusion criteria to ARDS consensus definitions and whether exclusion criteria are strongly or poorly justified. We estimated the proportion of between-trial difference in control-arm 28-day mortality explained by the inclusion criteria and RCT design characteristics using meta-regression.

RESULTS

A literature search identified 43 709 records. One hundred and fifty ARDS RCTs were included; 146/150 (97.3%) RCTs defined ARDS inclusion criteria using AECC/Berlin definitions. Deviations from consensus definitions, primarily aimed at improving ARDS diagnostic certainty, frequently related to duration of hypoxaemia (117/146; 80.1%). Exclusion criteria could be grouped by rationale for selection into strongly or poorly justified criteria. Common poorly justified exclusions included pregnancy related, age, and comorbidities (infectious/immunosuppression, hepatic, renal, and human immunodeficiency virus/acquired immunodeficiency syndrome). Control-arm 28-day mortality varied between ARDS RCTs (mean: 29.8% [95% confidence interval: 27.0-32.7%; I²=88.8%; τ²=0.02; P<0.01]), and differed significantly between RCTs with different Pao₂:FiO₂ ratio inclusion thresholds (26.6-39.9 kPa vs <26.6 kPa; P<0.01). In a meta-regression model, inclusion criteria and RCT design characteristics accounted for 30.6% of between-trial difference (P<0.01).

CONCLUSIONS

In most ARDS RCTs, consensus definitions are modified to use as inclusion criteria. Between-RCT mortality differences are mostly explained by the Pao₂:FiO₂ ratio threshold within the consensus definitions. An exclusion criteria framework can be applied when designing and reporting exclusion criteria in future ARDS RCTs.

Clinical Trials for AKI: Lessons Learned From the ARDS Network

The acute respiratory distress syndrome and acute kidney injury are both heterogeneous disease syndromes. A large number of multicenter clinical trials have been conducted focused on the treatment and prevention of the acute respiratory distress syndrome. Here, we focus on potential lessons learned for acute kidney injury clinical trials.

Ventilation management in acute respiratory failure related to COVID-19 versus ARDS from another origin - a descriptive narrative review

Introduction

It is uncertain whether ventilation in patients with acute respiratory failure related to coronavirus disease 2019 (COVID-19) differs from that in patients with acute respiratory distress syndrome (ARDS) from another origin.

Areas covered

We undertook two literature searches in PubMed to identify observational studies reporting on ventilation management––one in patients with acute respiratory failure related to COVID-19, and one in patients with ARDS from another origin. The searches identified 14 studies in patients with acute respiratory failure related to COVID-19, and 8 studies in patients with ARDS from another origin.

Expert opinion

In patients with acute respiratory failure related to COVID-19, ventilation management seems to be similar to that of patients with ARDS from another origin. The future lies in studies focused on personalized treatment of ARDS of all origins, including COVID-19.

Hypercapnia in the critically ill: insights from the bench to the bedside

Carbon dioxide (CO2) has long been considered, at best, a waste by-product of metabolism, and at worst, a toxic molecule with serious health consequences if physiological concentration is dysregulated. However, clinical observations have revealed that 'permissive' hypercapnia, the deliberate allowance of respiratory produced CO2 to remain in the patient, can have anti-inflammatory effects that may be beneficial in certain circumstances. In parallel, studies at the cell level have demonstrated the profound effect of CO2 on multiple diverse signalling pathways, be it the effect from CO2 itself specifically or from the associated acidosis it generates. At the whole organism level, it now appears likely that there are many biological sensing systems designed to respond to CO2 concentration and tailor respiratory and other responses to atmospheric or local levels. Animal models have been widely employed to study the changes in CO2 levels in various disease states and also to what extent permissive or even directly delivered CO2 can affect patient outcome. These findings have been advanced to the bedside at the same time that further clinical observations have been elucidated at the cell and animal level. Here we present a synopsis of the current understanding of how CO2 affects mammalian biological systems, with a particular emphasis on inflammatory pathways and diseases such as lung specific or systemic sepsis. We also explore some future directions and possibilities, such as direct control of blood CO2 levels, that could lead to improved clinical care in the future.

Between-trial heterogeneity in ARDS research

Purpose

Most randomized controlled trials (RCTs) in patients with acute respiratory distress syndrome (ARDS) revealed indeterminate or conflicting study results. We aimed to systematically evaluate between-trial heterogeneity in reporting standards and trial outcome.

Methods

A systematic review of RCTs published between 2000 and 2019 was performed including adult ARDS patients receiving lung-protective ventilation. A random-effects meta-regression model was applied to quantify heterogeneity (non-random variability) and to evaluate trial and patient characteristics as sources of heterogeneity.

Results

In total, 67 RCTs were included. The 28-day control-group mortality rate ranged from 10 to 67% with large non-random heterogeneity (I² = 88%, p < 0.0001). Reported baseline patient characteristics explained some of the outcome heterogeneity, but only six trials (9%) reported all four independently predictive variables (mean age, mean lung injury score, mean plateau pressure and mean arterial pH). The 28-day control group mortality adjusted for patient characteristics (i.e. the residual heterogeneity) ranged from 18 to 45%. Trials with significant benefit in the primary outcome reported a higher control group mortality than trials with an indeterminate outcome or harm (mean 28-day control group mortality: 44% vs. 28%; p = 0.001).

Conclusion

Among ARDS RCTs in the lung-protective ventilation era, there was large variability in the description of baseline characteristics and significant unexplainable heterogeneity in 28-day control group mortality. These findings signify problems with the generalizability of ARDS research and underline the urgent need for standardized reporting of trial and baseline characteristics.

Supplementary Information

The online version of this article (10.1007/s00134-021-06370-w) contains supplementary material, which is available to authorized users.

Non-specialist therapeutic strategies in acute respiratory distress syndrome

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is associated with significant morbidity and mortality. We undertook a meta-analysis of randomized controlled trials (RCTs) to determine the mortality benefit of non-specialist therapeutic interventions for ARDS available to general critical care units.

EVIDENCE ACQUISITION

A systematic search of MEDLINE, Embase, and the Cochrane Central Register for RCTs investigating therapeutic interventions in ARDS including corticosteroids, fluid management strategy, high PEEP, low tidal volume ventilation, neuromuscular blockade, prone position ventilation, or recruitment maneuvers. Data was collected on demographic information, treatment strategy, duration and dose of treatment, and primary (28 or 30-day mortality) and secondary (P<inf>a</inf>O<inf>2</inf>:FiO<inf>2</inf> ratio at 24-48 hours) outcomes.

EVIDENCE SYNTHESIS

No improvement in 28-day mortality could be demonstrated in three RCTs investigating high PEEP (28.0% vs. 30.2% control; risk ratio [confidence interval] 0.93 [0.82-1.06]; eight assessing prone position ventilation (39.3% vs. 44.5%; RR 0.83 [0.68-1.01]; seven investigating neuromuscular blockade (37.8% vs. 42.0%; RR 0.91 [0.81-1.03]); ten investigating recruitment maneuvers (42.4% vs. 42.1%; RR 1.01 [0.91-1.12]); eight investigating steroids (34.8% vs. 41.1%; RR 0.81 [0.59-1.12]); and one investigating conservative fluid strategies (25.4% vs. 28.4%; RR 0.90 [0.73-1.10]). Three studies assessing low tidal volume ventilation (33.1% vs. 41.9%; RR 0.79 (0.68-0.91); P=0.001), and subgroup analyses within studies investigating prone position ventilation greater than 12 hours (33.1% vs. 44.4%; RR 0.75 [0.59-0.95), P=0.02) did reveal outcome benefit.

CONCLUSIONS

Among non-specialist therapeutic strategies available to general critical care units, low tidal volumes and prone position ventilation for greater than 12 hours improve mortality in ARDS.

Optimal Upper Limits of Plateau Pressure for Patients With Acute Respiratory Distress Syndrome During the First Seven Days: A Meta-Regression Analysis

Background

The effects of plateau pressure during the initial days of mechanical ventilation on outcomes for patients with acute respiratory distress syndrome have not been fully examined. We conducted meta-regression analysis of plateau pressure during the first 7 days using randomized control trials to investigate the optimal upper limits of plateau pressure on different days of mechanical ventilation.

Methods

Randomized controlled trials comparing two mechanical ventilation strategies with lower and higher plateau pressures in patients with acute respiratory distress syndrome were included. Meta-regression analysis was performed to determine the association of plateau pressure with mortality on days 1, 3, and 7 of mechanical ventilation.

Results

After evaluation of 2,975 citations from a comprehensive search across electronic databases, 14 studies were included in the final qualitative analysis. A total of 4,984 patients were included in the quantitative analysis. As a result of the pairwise comparison, overall short-term mortality was significantly higher for patients with plateau pressures over 32 cm H₂O during the first 3 days after intensive care unit (ICU) admission (day 1: relative risk (RR), 0.77; 95% confidence interval (CI), 0.66 - 0.89; I² = 0%; day 3: RR, 0.76; 95% CI, 0.64 - 0.90; I² = 0%), but not on day 7 (RR, 0.82; 95% CI, 0.65 - 1.04; I² = 16%). Plateau pressures below 27 cm H₂O and 30 cm H₂O were not associated with an absolute risk reduction of short-term mortality. According to univariable meta-regression analysis, mortality was significantly associated with plateau pressure on day 1 (β = 0.01 (95% CI, 0.002 - 0.024), P = 0.02). On days 3 and 7, however, no significant difference was detected. When the cutoffs were set at 27, 30 and 32 cm H₂O on day 1, which showed a significant difference, plateau pressure tended to be associated with increased mortality at pressures above the cut-off values, and there were no significant differences at pressures below the cut-off values, regardless of the cutoff used.

Conclusions

This study suggests that the optimal cut-off value for plateau pressure may be 27 cm H₂O especially during the initial period of mechanical ventilation, although this association may not continue during the latter period of mechanical ventilation.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members. As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

Current and evolving standards of care for patients with ARDS

Care for patients with acute respiratory distress syndrome (ARDS) has changed considerably over the 50 years since its original description. Indeed, standards of care continue to evolve as does how this clinical entity is defined and how patients are grouped and treated in clinical practice. In this narrative review we discuss current standards – treatments that have a solid evidence base and are well established as targets for usual care – and also evolving standards – treatments that have promise and may become widely adopted in the future. We focus on three broad domains of ventilatory management, ventilation adjuncts, and pharmacotherapy. Current standards for ventilatory management include limitation of tidal volume and airway pressure and standard approaches to setting PEEP, while evolving standards might focus on limitation of driving pressure or mechanical power, individual titration of PEEP, and monitoring efforts during spontaneous breathing. Current standards in ventilation adjuncts include prone positioning in moderate-severe ARDS and veno-venous extracorporeal life support after prone positioning in patients with severe hypoxemia or who are difficult to ventilate. Pharmacotherapy current standards include corticosteroids for patients with ARDS due to COVID-19 and employing a conservative fluid strategy for patients not in shock; evolving standards may include steroids for ARDS not related to COVID-19, or specific biological agents being tested in appropriate sub-phenotypes of ARDS. While much progress has been made, certainly significant work remains to be done and we look forward to these future developments.

Surviving Sepsis Campaign: Guidelines on the Management of Critically Ill Adults with Coronavirus Disease 2019 (COVID-19)

BACKGROUND

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of a rapidly spreading illness, Coronavirus Disease 2019 (COVID-19), affecting thousands of people around the world. Urgent guidance for clinicians caring for the sickest of these patients is needed.

METHODS

We formed a panel of 36 experts from 12 countries. All panel members completed the World Health Organization conflict of interest disclosure form. The panel proposed 53 questions that are relevant to the management of COVID-19 in the ICU. We searched the literature for direct and indirect evidence on the management of COVID-19 in critically ill patients in the ICU. We identified relevant and recent systematic reviews on most questions relating to supportive care. We assessed the certainty in the evidence using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach, then generated recommendations based on the balance between benefit and harm, resource and cost implications, equity, and feasibility. Recommendations were either strong or weak, or in the form of best practice recommendations.

RESULTS

The Surviving Sepsis Campaign COVID-19 panel issued 54 statements, of which four are best practice statements, nine are strong recommendations, and 35 are weak recommendations. No recommendation was provided for six questions. The topics were: 1) infection control, 2) laboratory diagnosis and specimens, 3) hemodynamic support, 4) ventilatory support, and 5) COVID-19 therapy.

CONCLUSION

The Surviving Sepsis Campaign COVID-19 panel issued several recommendations to help support healthcare workers caring for critically ill ICU patients with COVID-19. When available, we will provide new evidence in further releases of these guidelines.

Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19)

Background

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of a rapidly spreading illness, Coronavirus Disease 2019 (COVID-19), affecting thousands of people around the world. Urgent guidance for clinicians caring for the sickest of these patients is needed.

Methods

We formed a panel of 36 experts from 12 countries. All panel members completed the World Health Organization conflict of interest disclosure form. The panel proposed 53 questions that are relevant to the management of COVID-19 in the ICU. We searched the literature for direct and indirect evidence on the management of COVID-19 in critically ill patients in the ICU. We identified relevant and recent systematic reviews on most questions relating to supportive care. We assessed the certainty in the evidence using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach, then generated recommendations based on the balance between benefit and harm, resource and cost implications, equity, and feasibility. Recommendations were either strong or weak, or in the form of best practice recommendations.

Results

The Surviving Sepsis Campaign COVID-19 panel issued 54 statements, of which 4 are best practice statements, 9 are strong recommendations, and 35 are weak recommendations. No recommendation was provided for 6 questions. The topics were: (1) infection control, (2) laboratory diagnosis and specimens, (3) hemodynamic support, (4) ventilatory support, and (5) COVID-19 therapy.

Conclusion

The Surviving Sepsis Campaign COVID-19 panel issued several recommendations to help support healthcare workers caring for critically ill ICU patients with COVID-19. When available, we will provide new recommendations in further releases of these guidelines.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06022-5) contains supplementary material, which is available to authorized users.

A Physiologically Informed Strategy to Effectively Open, Stabilize, and Protect the Acutely Injured Lung

Acute respiratory distress syndrome (ARDS) causes a heterogeneous lung injury and remains a serious medical problem, with one of the only treatments being supportive care in the form of mechanical ventilation. It is very difficult, however, to mechanically ventilate the heterogeneously damaged lung without causing secondary ventilator-induced lung injury (VILI). The acutely injured lung becomes time and pressure dependent, meaning that it takes more time and pressure to open the lung, and it recollapses more quickly and at higher pressure. Current protective ventilation strategies, ARDSnet low tidal volume (LVt) and the open lung approach (OLA), have been unsuccessful at further reducing ARDS mortality. We postulate that this is because the LVt strategy is constrained to ventilating a lung with a heterogeneous mix of normal and focalized injured tissue, and the OLA, although designed to fully open and stabilize the lung, is often unsuccessful at doing so. In this review we analyzed the pathophysiology of ARDS that renders the lung susceptible to VILI. We also analyzed the alterations in alveolar and alveolar duct mechanics that occur in the acutely injured lung and discussed how these alterations are a key mechanism driving VILI. Our analysis suggests that the time component of each mechanical breath, at both inspiration and expiration, is critical to normalize alveolar mechanics and protect the lung from VILI. Animal studies and a meta-analysis have suggested that the time-controlled adaptive ventilation (TCAV) method, using the airway pressure release ventilation mode, eliminates the constraints of ventilating a lung with heterogeneous injury, since it is highly effective at opening and stabilizing the time- and pressure-dependent lung. In animal studies it has been shown that by “casting open” the acutely injured lung with TCAV we can (1) reestablish normal expiratory lung volume as assessed by direct observation of subpleural alveoli; (2) return normal parenchymal microanatomical structural support, known as alveolar interdependence and parenchymal tethering, as assessed by morphometric analysis of lung histology; (3) facilitate regeneration of normal surfactant function measured as increases in surfactant proteins A and B; and (4) significantly increase lung compliance, which reduces the pathologic impact of driving pressure and mechanical power at any given tidal volume.

Temporal Changes in Ventilator Settings in Patients With Uninjured Lungs: A Systematic Review

In patients with uninjured lungs, increasing evidence indicates that tidal volume (VT) reduction improves outcomes in the intensive care unit (ICU) and in the operating room (OR). However, the degree to which this evidence has translated to clinical changes in ventilator settings for patients with uninjured lungs is unknown. To clarify whether ventilator settings have changed, we searched MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for publications on invasive ventilation in ICUs or ORs, excluding those on patients <18 years of age or those with >25% of patients with acute respiratory distress syndrome (ARDS). Our primary end point was temporal change in VT over time. Secondary end points were changes in maximum airway pressure, mean airway pressure, positive end-expiratory pressure, inspiratory oxygen fraction, development of ARDS (ICU studies only), and postoperative pulmonary complications (OR studies only) determined using correlation analysis and linear regression. We identified 96 ICU and 96 OR studies comprising 130,316 patients from 1975 to 2014 and observed that in the ICU, VT size decreased annually by 0.16 mL/kg (-0.19 to -0.12 mL/kg) (P < .001), while positive end-expiratory pressure increased by an average of 0.1 mbar/y (0.02-0.17 mbar/y) (P = .017). In the OR, VT size decreased by 0.09 mL/kg per year (-0.14 to -0.04 mL/kg per year) (P < .001). The change in VTs leveled off in 1995. Other intraoperative ventilator settings did not change in the study period. Incidences of ARDS (ICU studies) and postoperative pulmonary complications (OR studies) also did not change over time. We found that, during a 39-year period, from 1975 to 2014, VTs in clinical studies on mechanical ventilation have decreased significantly in the ICU and in the OR.