Ventilatory support after extubation in critically ill patients

The "ZEEP-PEEP test" to evaluate the response to positive end-expiratory pressure delivered by helmet: A prospective physiologic study

Introduction

The improvement in oxygenation after helmet application in hypoxemic patients may be explained by the alveolar recruitment obtained with positive end expiratory pressure (PEEP) or by the administration of a more accurate inspiratory fraction of oxygen (FiO2). We have designed the "ZEEP-PEEP test", capable to distinguish between the FiO2-related or PEEP-related oxygenation improvement. Our primary aim was to describe the use of this test during helmet CPAP to assess the oxygenation improvement attributable to PEEP application.

Material and methods

We performed a prospective physiological study including adult critically ill patients. Respiratory and hemodynamic parameters were recorded before helmet application (PRE step), after helmet application without PEEP (ZEEP step) and after the application of the PEEP valve (PEEP step), while maintaining a constant FiO2. We defined as "PEEP responders" patients showing a PaO2/FiO2 ratio improvement ≥10% after PEEP application.

Results

93 patients were enrolled. Compared to the PRE step, PaO2/FiO2 ratio was significantly improved during helmet CPAP both at ZEEP and PEEP step (189 ± 55, 219 ± 74 and 241 ± 82 mmHg, respectively, p < 0.01). Both PEEP responders (41%) and non-responders showed a significant improvement of PaO2/FiO2 ratio after the application of helmet at ZEEP, PEEP responders also showed a significant improvement of oxygenation after PEEP application (208 ± 70 vs 267 ± 85, p < 0.01).

Conclusions

Helmet CPAP improved oxygenation. This improvement was not only due to the PEEP effect, but also to the increase of the effective inspired FiO2. Performing the ZEEP-PEEP test may help to identify patients who benefit from PEEP.

Spanish Society of Anesthesiology, Reanimation and Pain Therapy (SEDAR) Spanish Society of Emergency and Emergency Medicine (SEMES) and Spanish Society of Otolaryngology, Head and Neck Surgery (SEORL-CCC) Guideline for difficult airway management. Part II

The Airway Management section of the Spanish Society of Anesthesiology, Resuscitation, and Pain Therapy (SEDAR), the Spanish Society of Emergency Medicine (SEMES), and the Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL-CCC) present the Guide for the comprehensive management of difficult airway in adult patients. Its principles are focused on the human factor, cognitive processes for decision-making in critical situations, and optimization in the progression of strategies application to preserve adequate alveolar oxygenation in order to enhance safety and the quality of care. The document provides evidence-based recommendations, theoretical-educational tools, and implementation tools, mainly cognitive aids, applicable to airway management in the fields of anesthesiology, critical care, emergencies, and prehospital medicine. For this purpose, an extensive literature search was conducted following PRISMA-R guidelines and was analyzed using the GRADE methodology. Recommendations were formulated according to the GRADE methodology. Recommendations for sections with low-quality evidence were based on expert opinion through consensus reached via a Delphi questionnaire.

Personalized Noninvasive Respiratory Support in the Perioperative Setting: State of the Art and Future Perspectives

Background: Noninvasive respiratory support (NRS), including high-flow nasal oxygen therapy (HFNOT), noninvasive ventilation (NIV) and continuous positive airway pressure (CPAP), are routinely used in the perioperative period. Objectives: This narrative review provides an overview on the perioperative use of NRS. Preoperative, intraoperative, and postoperative respiratory support is discussed, along with potential future areas of research. Results: During induction of anesthesia, in selected patients at high risk of difficult intubation, NIV is associated with improved gas exchange and reduced risk of postoperative respiratory complications. HFNOT demonstrated an improvement in oxygenation. Evidence on the intraoperative use of NRS is limited. Compared with conventional oxygenation, HFNOT is associated with a reduced risk of hypoxemia during procedural sedation, and recent data indicate a possible role for HFNOT for intraoperative apneic oxygenation in specific surgical contexts. After extubation, "preemptive" NIV and HFNOT in unselected cohorts do not affect clinical outcome. Postoperative "curative" NIV in high-risk patients and among those exhibiting signs of respiratory failure can reduce reintubation rate, especially after abdominal surgery. Data on postoperative "curative" HFNOT are limited. Conclusions: There is increasing evidence on the perioperative use of NRS. Use of NRS should be tailored based on the patient's specific characteristics and type of surgery, aimed at a personalized cost-effective approach.

Effectiveness of Minitracheostomy After Extubation in Patients with Pneumonia at High Risk of Reintubation: A Case Series

Introduction

Minitracheostomy involves the percutaneous insertion of a 4-mm-diameter cricothyroidotomy tube for tracheal suctioning to facilitate the clearance of airway secretions. The advantage of using the minitracheostomy is in the clearance of secretions, however data on their usefulness for respiratory failure after extubation is limited. Aim of the study: We aimed to assess the use of minitracheostomy for patients with challenging extubation caused by significant sputum.

Material and Methods

We conducted a retrospective analysis of consecutive case series. We analyzed the data of 31 patients with pneumonia. After minitracheostomy, the primary endpoints of reintubation within 72 hours and clinical effects, including mortality, length of intensive care unit (ICU), or hospital stay, were assessed. The successful extubation group included patients who did not require reintubation within 72 hours. Conversely, the reintubation group consisted of patients mandating reestablishment of intubation within 72 hours.

Results

Among those who underwent minitracheostomy after extubation, 22 (71%) underwent successful extubation and 9 underwent reintubation (reintubation rate: 29%). The in-hospital mortality rates after 30 days were 18.2% in the successful extubation group and 22.2% in the reintubation group. The ICU and hospital lengths of stay were 11 days (interquartile range: 8-14.3 days) and 23 days (interquartile range: 15.5-41 days), respectively, in the successful extubation group; they were 14 days (interquartile range: 11-18.5 days) and 30 days (interquartile range: 16-45.5 days), respectively, in the reintubation group.

Conclusions

The prophylactic use of minitracheostomy may be an option as a means of reducing reintubation in patients with pneumonia who are at very high risk of reintubation.

Efficacy of two doses of dexmedetomidine on attenuating cardiovascular response and safety of respiratory tract to extubation

Introduction

Extubation can be associated with an adverse hemodynamic or respiratory response, which may be serious in cardiovascular written or in the elderly. The present study was conducted with the aim of investigating the effect of two different doses of dexmedetomidine in the prevention of extubation complications.

Methods

This randomized clinical trial was conducted in Isfahan in 2020-2021 on 174 patients undergoing elective surgery. Patients were randomly divided into 3 groups receiving dexmedetomidine 1 μg/kg (D1), dexmedetomidine 0.5 μg/kg (D2), and normal saline (S). Hemodynamic variables include heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and peripheral blood oxygen saturation (Spo2) was measured and recorded before removing the endotracheal tube and at 1, 3, 5 and 10 minutes after extubation. Also, airway responses to extubation such as cough, hoarseness, and laryngospasm were investigated.

Results

SBP, MAP, and HR in the D1 group were significantly lower than in other groups. In the D2 group, these measurements were lower than the control group at 3, 5, and 10 minutes after extubation (P<0.05 for all). In placebo group, SBP, MAP, and HR increased significantly after extubation (P=0.01). In group D1, cough (P=0.007) and its intensity (P=0.013), nausea and vomiting (P=0.04) and chills (P=0.001) were less than in other groups.

Conclusion

In the D1 group, attenuation of autonomic response to extubation was more than other groups and side effects were less than D2 group, and in both groups, these side effects were less than the saline group.

Prophylactic noninvasive respiratory support in the immediate postoperative period after cardiac surgery - a systematic review and network meta-analysis

BACKGROUND

Noninvasive respiratory support has been increasingly applied in the immediate postoperative period to prevent postoperative pulmonary complications (PPCs). However, the optimal approach remains uncertain. We sought to evaluate the comparative effectiveness of various noninvasive respiratory strategies used in the immediate postoperative period after cardiac surgery.

METHODS

We conducted a frequentist random-effect network meta-analysis (NMA) of randomized controlled trials (RCTs) comparing the prophylactic use of noninvasive ventilation (NIV), continuous positive airway pressure (CPAP), high flow nasal cannula (HFNC), or postoperative usual care (PUC) in the immediate postoperative period after cardiac surgery. Databases were systematically searched through September 28, 2022. Study selection, data extraction, and quality assessment were performed in duplicate. The primary outcome was the incidence of PPCs.

RESULTS

Sixteen RCTs enrolling 3011 patients were included. Compared with PUC, NIV significantly reduced the incidence of PPCs [relative risk (RR) 0.67, 95% confidence interval (CI): 0.49 to 0.93; absolute risk reduction (ARR) 7.6%, 95% CI: 1.6-11.8%; low certainty] and the incidence of atelectasis (RR 0.65, 95% CI: 0.45 to 0.93; ARR 19.3%, 95% CI: 3.9-30.4%; moderate certainty); however, prophylactic NIV was not associated with a decreased reintubation rate (RR 0.82, 95% CI: 0.29 to 2.34; low certainty) or reduced short-term mortality (RR 0.64, 95% CI: 0.16 to 2.52; very low certainty). As compared to PUC, the preventive use of CPAP (RR 0.85, 95% CI: 0.60 to 1.20; very low certainty) or HFNC (RR 0.74, 95% CI: 0.46 to 1.20; low certainty) had no significant beneficial effect on the incidence of PPCs, despite exhibiting a downward trend. Based on the surface under the cumulative ranking curve, the highest-ranked treatment for reducing the incidence of PPCs was NIV (83.0%), followed by HFNC (62.5%), CPAP (44.3%), and PUC (10.2%).

CONCLUSIONS

Current evidence suggest that the prophylactic use of NIV in the immediate postoperative period is probably the most effective noninvasive respiratory approach to prevent PPCs in patients undergoing cardiac surgery. Given the overall low certainty of the evidence, further high-quality research is warranted to better understand the relative benefits of each noninvasive ventilatory support.

CLINICAL TRIAL REGISTRATION

PROSPERO, https://www.crd.york.ac.uk/prospero/ , registry number: CRD42022303904.

The feasibility of using mouthpiece ventilation in the intensive care unit for post-extubation breathing support after acute tetraplegia

STUDY DESIGN

A prospective cohort of patients with acute tetraplegia.

OBJECTIVES

This study aimed to determine the feasibility of using mouthpiece ventilation (MPV) in the intensive care unit (ICU) for patients who are extubated after suffering an acute cervical spinal cord injury (CSCI).

SETTING

ICU, Princess Alexandra Hospital, Brisbane Australia.

METHODS

New admissions to ICU in the 14 months between April 2017 and June 2018 with a CSCI who underwent intubation were assessed for inclusion. MPV was provided to consenting participants (who were deemed likely to be able to maintain ventilation on their own) at the time of extubation and was utilised in addition to standard care while participants were awake. MPV settings, usage, and support hours to educate and facilitate MPV were collected. Feedback from participants and clinical staff was gathered throughout the study. Pre- and post-extubation measures of forced vital capacity (FVC), the frequency of endotracheal suction of sputum, and gas exchange using ventilation-perfusion ratios were recorded along with the incidence of reintubation.

RESULTS

Fourteen participated in utilising MPV with 16 episodes of extubation. The average time per participant to have MPV titrated and bedside data collected was 178 minutes. Data from 16 episodes of extubation have been included. Three of the 14 participants failed initial extubation. Feedback from participants and clinicians has been positive and constructive, enabling MPV settings to be adapted to the person with acute CSCI during this pilot study.

CONCLUSION

MPV is feasible to use post-extubation for people with CSCI in ICU. Pressure control mode MPV was deemed the most suitable for newly extubated acute CSCI patients. Intensive clinical support is required initially to provide education prior to MPV, and at the time of extubation for both patient and treating clinicians. Both report it to be a useful adjunct to ICU treatment.

Effect of non-invasive ventilation after extubation in critically ill patients with obesity in France: a multicentre, unblinded, pragmatic randomised clinical trial

BACKGROUND

Non-invasive ventilation (NIV) and oxygen therapy (high-flow nasal oxygen [HFNO] or standard oxygen) following extubation have never been compared in critically ill patients with obesity. We aimed to compare NIV (alternating with HFNO or standard oxygen) and oxygen therapy (HFNO or standard oxygen) following extubation of critically ill patients with obesity.

METHODS

In this multicentre, parallel group, pragmatic randomised controlled trial, conducted in 39 intensive care units in France, critically ill patients with obesity undergoing extubation were randomly assigned (1:1) to either the NIV group or the oxygen therapy group. Two randomisations were performed: first, randomisation to either NIV or oxygen therapy, and second, randomisation to either HFNO or standard oxygen (also 1:1), which was nested within the first randomisation. Blinding of the randomisation was not possible, but the statistician was masked to group assignment. The primary outcome was treatment failure within 3 days after extubation, a composite of reintubation for mechanical ventilation, switch to the other study treatment, or premature discontinuation of study treatment. The primary outcome was analysed by intention to treat. Effect of medical and surgical status was assessed. The reintubation within 3 days was analysed by intention to treat and after a post-hoc crossover analysis. This study is registered with ClinicalTrials.gov, number NCT04014920.

FINDINGS

From Oct 2, 2019, to July 17, 2021, of the 1650 screened patients, 981 were enrolled. Treatment failure occurred in 66 (13·5%) of 490 patients in the NIV group and in 130 (26·5%) of 491 patients in the oxygen-therapy group (relative risk 0·43; 95% CI 0·31-0·60, p<0·0001). Medical or surgical status did not modify the effect of NIV group on the treatment-failure rate. Reintubation within 3 days after extubation was similar in the non-invasive ventilation group and in the oxygen therapy group in the intention-to-treat analysis (48 (10%) of 490 patients and 59 (12%) of 491 patients, p=0·26) and lower in the NIV group than in the oxygen-therapy group in the post-hoc cross-over (51 (9%) of 560 patients and 56 (13%) of 421 patients, p=0·037) analysis. No severe adverse events were reported.

INTERPRETATION

Among critically ill adults with obesity undergoing extubation, the use of NIV was effective to reduce treatment-failure within 3 days. Our results are relevant to clinical practice, supporting the use of NIV after extubation of critically ill patients with obesity. However, most of the difference in the primary outcome was due to patients in the oxygen therapy group switching to NIV, and more evidence is needed to conclude that an NIV strategy leads to improved patient-centred outcomes.

FUNDING

French Ministry of Health.

Continued enteral nutrition until extubation compared with fasting before extubation in patients in the intensive care unit: an open-label, cluster-randomised, parallel-group, non-inferiority trial

BACKGROUND

Fasting is frequently imposed before extubation in patients in intensive care units, with the aim to reduce risk of aspiration. This unevaluated practice might delay extubation, increase workload, and reduce caloric intake. We aimed to compare continued enteral nutrition until extubation with fasting before extubation in patients in the intensive care unit.

METHODS

We conducted an open-label, cluster-randomised, parallel-group, non-inferiority trial in 22 intensive care units in France. Patients aged 18 years or older were eligible for enrolment if they had received invasive mechanical ventilation for at least 48 h in the intensive care unit and received prepyloric enteral nutrition for at least 24 h at the time of extubation decision. Centres were randomly assigned (1:1) to continued enteral nutrition until extubation or 6-h fasting with concomitant gastric suctioning before extubation, to be applied for all patients within the unit. Masking was not possible because of the nature of the trial. The primary outcome was extubation failure (composite criteria of reintubation or death) within 7 days after extubation, assessed in both the intention-to-treat and per-protocol populations. The non-inferiority margin was set at 10%. Pneumonia within 14 days of extubation was a key secondary endpoint. This trial is now complete and is registered with ClinicalTrials.gov, NCT03335345.

FINDINGS

Between April 1, 2018, and Oct 31, 2019, 7056 patients receiving enteral nutrition and mechanical ventilation were admitted to the intensive care units and 4198 were assessed for eligibility. 1130 patients were enrolled and included in the intention-to-treat population and 1008 were included in the per-protocol population. In the intention-to-treat population, extubation failure occurred in 106 (17·2%) of 617 patients assigned to receive continued enteral nutrition until extubation versus 90 (17·5%) of 513 assigned to fasting, meeting the a priori defined non-inferiority criterion (absolute difference -0·4%, 95% CI -5·2 to 4·5). In the per-protocol population, extubation failure occurred in 101 (17·0%) of 595 patients assigned to receive continued enteral nutrition versus 74 (17·9%) of 413 assigned to fasting (absolute difference -0·9%, 95% CI -5·6 to 3·7). Pneumonia within 14 days of extubation occurred in ten (1·6%) patients assigned to receive continued enteral nutrition and 13 (2·5%) assigned to fasting (rate ratio 0·77, 95% CI 0·22 to 2·69).

INTERPRETATION

Continued enteral nutrition until extubation in critically ill patients in the intensive care unit was non-inferior to a 6-h fasting maximum gastric vacuity strategy comprising continuous gastric tube suctioning, in terms of extubation failure within 7 days (a patient-centred outcome), and thus represents a potential alternative in this population.

FUNDING

French Ministry of Health.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

High-Flow Versus VenturiMask Oxygen Therapy to Prevent Reintubation in Hypoxemic Patients after Extubation: A Multicenter Randomized Clinical Trial

Rationale: When compared with VenturiMask after extubation, high-flow nasal oxygen provides physiological advantages. Objectives: To establish whether high-flow oxygen prevents endotracheal reintubation in hypoxemic patients after extubation, compared with VenturiMask. Methods: In this multicenter randomized trial, 494 patients exhibiting Pa_O2:Fi_O2 ratio ⩽ 300 mm Hg after extubation were randomly assigned to receive high-flow or VenturiMask oxygen, with the possibility to apply rescue noninvasive ventilation before reintubation. High-flow use in the VenturiMask group was not permitted. Measurements and Main Results: The primary outcome was the rate of reintubation within 72 hours according to predefined criteria, which were validated a posteriori by an independent adjudication committee. Main secondary outcomes included reintubation rate at 28 days and the need for rescue noninvasive ventilation according to predefined criteria. After intubation criteria validation (n = 492 patients), 32 patients (13%) in the high-flow group and 27 patients (11%) in the VenturiMask group required reintubation at 72 hours (unadjusted odds ratio, 1.26 [95% confidence interval (CI), 0.70-2.26]; P = 0.49). At 28 days, the rate of reintubation was 21% in the high-flow group and 23% in the VenturiMask group (adjusted hazard ratio, 0.89 [95% CI, 0.60-1.31]; P = 0.55). The need for rescue noninvasive ventilation was significantly lower in the high-flow group than in the VenturiMask group: at 72 hours, 8% versus 17% (adjusted hazard ratio, 0.39 [95% CI, 0.22-0.71]; P = 0.002) and at 28 days, 12% versus 21% (adjusted hazard ratio, 0.52 [95% CI, 0.32-0.83]; P = 0.007). Conclusions: Reintubation rate did not significantly differ between patients treated with VenturiMask or high-flow oxygen after extubation. High-flow oxygen yielded less frequent use of rescue noninvasive ventilation. Clinical trial registered with www.clinicaltrials.gov (NCT02107183).

Efficacy of preventive use of oxygen therapy after planned extubation in high-risk patients with extubation failure: A network meta-analysis of randomized controlled trials

Background

Extubation failure is common in critically ill patients, especially those with high-risk factors, and is associated with poor prognosis. Prophylactic use of oxygen therapy after extubation has been gradually introduced. However, the best respiratory support method is still unclear.

Purpose

This study aimed to evaluate the efficacy of four post-extubation respiratory support approaches in reducing reintubation and respiratory failure in patients at high-risk of extubation failure.

Methods

A comprehensive search was performed in Cochrane Central Register of Controlled Trials, PubMed, EMBASE, and Web of Science from inception to June 2022. Randomized controlled trials (RCTs) comparing post-extubation preventive use of respiratory management strategies, including conventional oxygen therapy (COT), non-invasive ventilation (NIV), and high-flow nasal catheter (HFNC) in high-risk patients with extubation failure were reviewed. Primary outcomes were reintubation rate and respiratory failure. Secondary outcomes included intensive care unit (ICU) mortality, ICU stay and length of hospital stay (LOS).

Results

Seventeen RCTs comprising 2813 participants were enrolled. Compared with COT, the three respiratory support methods (NIV, HFNC, NIV + HFNC) were all effective in preventing reintubation [odds ratio (OR) 0.46, 95% confidence interval (CI) 0.32–0.67; OR 0.26, 95% CI 0.14–0.48; OR 0.62, 95% CI 0.39–0.97, respectively] and respiratory failure (OR 0.23, 95% CI 0.10–0.52; OR 0.15, 95% CI 0.04–0.60; OR 0.26, 95% CI 0.10–0.72, respectively). NIV and NIV + HFNC also reduced ICU mortality (OR 0.40, 95% CI 0.22–0.74; OR 0.32, 95% CI 0.12–0.85). NIV + HFNC ranked best in terms of reintubation rate, respiratory failure and ICU mortality based on the surface under the cumulative ranking curve (SUCRA) (99.3, 87.1, 88.2, respectively). Although there was no significant difference in shortening ICU stay and LOS among the four methods, HFNC ranked first based on the SUCRA.

Conclusion

Preventive use of NIV + HFNC after scheduled extubation is probably the most effective respiratory support method for preventing reintubation, respiratory failure and ICU death in high-risk patients with extubation failure. HFNC alone seems to be the best method to shorten ICU stay and LOS.

Systematic review registration

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42022340623].

High flow nasal cannula for patients undergoing bronchoscopy and gastrointestinal endoscopy: A systematic review and meta-analysis

Background

High flow nasal cannula is gaining increasingly used in patients undergoing endoscopic procedures. We undertook this systematic review and meta-analysis to determine whether high flow nasal cannula (HFNC) could effectively minimize the risk of hypoxemia as compared with conventional oxygen therapy (COT).

Methods

We performed a comprehensive search of Pubmed, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, and Web of Science. Studies involving the application of HFNC during endoscopic procedures were identified.

Results

We included 15 randomized controlled trials (7 bronchoscopy, 8 gastrointestinal endoscopy). Patients receiving HFNC during endoscopic procedures had a significantly lower risk of hypoxemia (defined as SpO2 &lt; 90%) versus COT group (risk ratio = 0.32; 95%CI (0.22–0.47), 13 studies, 4,093 patients, moderate-quality evidence, I2 = 48.82%, P &lt; 0.001). The lowest SpO2 was significantly higher in HFNC group (mean difference = 4.41; 95%CI (2.95–5.86), 9 studies, 1,449 patients, moderate-quality evidence, I2 = 81.17%, P &lt; 0.001) than those receiving COT. No significant difference was detected between groups in end-procedure partial pressure of CO2 (standard mean difference  =  −0.18; 95%CI (−0.52–0.15), 5 studies, 238 patients, moderate-quality evidence, I2 = 42.25%, P = 0.29). Patients receiving HFNC were associated a lower need for airway intervention (risk ratio = 0.45; 95%CI (0.24–0.84), 8 studies, 2,872 patients, moderate-quality evidence, I2 = 85.97%, P = 0.01) and less procedure interruption (risk ratio = 0.36; 95%CI (0.26–0.51), 6 studies, 1,562 patients, moderate-quality evidence, I2 = 0.00%, P &lt; 0.001). The overall intubation rate after endoscopy was 0.20% in both group, with no difference detected (risk ratio = 1.00; 95%CI (0.30–3.35), 7 studies, 2,943 patients, low-quality evidence, I2 = 0.00%, P = 1.00).

Conclusion

This systematic review and meta-analysis found moderate to low evidence that the application of HFNC was associated with improved oxygenation, decreased need for airway intervention, and reduced procedure interruption in patients undergoing endoscopic procedures. Future larger sample and high-quality studies are warranted to confirm our result and further investigate the effectiveness of HFNC in patients at risk.

Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier: CRD42022298032.

The ROX index as a predictor of high-flow nasal cannula outcome in pneumonia patients with acute hypoxemic respiratory failure: a systematic review and meta-analysis

Background

The respiratory rate-oxygenation (ROX) index has been increasingly applied to predict the outcome of high-flow nasal cannula (HFNC) in pneumonia patients with acute hypoxemic respiratory failure (AHRF). However, its diagnostic accuracy for the HFNC outcome has not yet been systematically assessed. This meta-analysis sought to evaluate the predictive performance of the ROC index for the successful weaning from HFNC in pneumonia patients with AHRF.

Methods

A literature search was conducted on electronic databases through February 12, 2022, to retrieve studies that investigated the diagnostic accuracy of the ROC index for the outcome of HFNC application in pneumonia patients with AHRF. The area under the hierarchical summary receiver operating characteristic curve (AUHSROC) was estimated as the primary measure of diagnostic accuracy due to the varied cutoff values of the index. We observed the distribution of the cutoff values and estimated the optimal threshold with corresponding 95% confidential interval (CI).

Results

Thirteen observational studies comprising 1751 patients were included, of whom 1003 (57.3%) successfully weaned from HFNC. The ROC index exhibits good performance for predicting the successful weaning from HFNC in pneumonia patients with AHRF, with an AUHSROC of 0.81 (95% CI 0.77–0.84), a pooled sensitivity of 0.71 (95% CI 0.64–0.78), and a pooled specificity of 0.78 (95% CI 0.70–0.84). The cutoff values of the ROX index were nearly conically symmetrically distributed; most data were centered between 4.5 and 6.0, and the mean and median values were 4.8 (95% CI 4.2–5.4) and 5.3 (95% CI 4.2–5.5), respectively. Moreover, the AUHSROC in the subgroup of measurement within 6 h after commencing HFNC was comparable to that in the subgroup of measurement during 6–12 h. The stratified analyses also suggested that the ROC index was a reliable predictor of HFNC success in pneumonia patients with coronavirus disease 2019.

Conclusions

In pneumonia patients with AHRF, the ROX index measured within 12 h after HFNC initiation is a good predictor of successful weaning from HFNC. The range of 4.2–5.4 may represent the optimal confidence interval for the prediction of HFNC outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01914-2.

Mucus Clearance Strategies in Mechanically Ventilated Patients

The use of airway clearance strategies as supplementary treatment in respiratory disease has been best investigated in patients with cystic fibrosis (CF) and non-cystic fibrosis bronchiectasis (NCFBE), conditions which are traditionally characterized by excessive mucus stasis and mucociliary dysfunction. A variety of airway clearance therapies both pharmacological and non-pharmacological have been shown to ameliorate disease progression in this population and have hence been assimilated into routine respiratory care. This self-propagating cycle of mucus retention and airway damage leading to chronic inflammation and infections can also be applied to patients with respiratory failure requiring mechanical ventilation. Furthermore, excessive trachea-bronchial secretions have been associated with extubation failure presenting an opportunity for intervention. Evidence for the use of adjunctive mucoactive agents and other therapies to facilitate secretion clearance in these patients are not well defined, and this subgroup still remains largely underrepresented in clinical trials. In this review, we discuss the role of mucus clearance techniques with a proven benefit in patients with CF and NCFBE, and their potential role in patients requiring mechanical ventilation while highlighting the need for standardization and adoption of mucus clearance strategies in these patient populations.

ERS Clinical Practice Guidelines: High-flow nasal cannula in acute respiratory failure

BACKGROUND

High-flow nasal cannula (HFNC) has become a frequently used non-invasive form of respiratory support in acute settings, however evidence supporting its use has only recently emerged. These guidelines provide evidence-based recommendations for the use of HFNC alongside other noninvasive forms of respiratory support in adults with acute respiratory failure (ARF).

MATERIALS AND METHODOLOGY

The European Respiratory Society Task Force panel included expert clinicians and methodologists in pulmonology and intensive care medicine. The Task Force used the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) methods to summarize evidence and develop clinical recommendations for the use of HFNC alongside conventional oxygen therapy (COT) and non-invasive ventilation (NIV) for the management of adults in acute settings with ARF.

RESULTS

The Task Force developed 8 conditional recommendations, suggesting using: 1) HFNC over COT in hypoxemic ARF, 2) HFNC over NIV in hypoxemic ARF, 3)HFNC over COT during breaks from NIV, 4) either HFNC or COT in post-operative patients at low risk of pulmonary complications, 5) either HFNC or NIV in post-operative patients at high risk of pulmonary complications, 6) HFNC over COT in non-surgical patients at low risk of extubation failure, 7) NIV over HFNC for patients at high risk of extubation failure unless there are relative or absolute contraindications to NIV, 8) trialling NIV prior to use of HFNC in patients with chronic obstructive pulmonary disease (COPD) and hypercapnic ARF.

CONCLUSIONS

HFNC is a valuable intervention in adults with ARF. These conditional recommendations can assist clinicians in choosing the most appropriate form of non-invasive respiratory support to provide to patients in different acute settings.

Postextubation fluid balance is associated with extubation failure: a cohort study

Objetivo

Avaliar se há associação entre o balanço hídrico nas 48 horas após a extubação e a falha da extubação.

Métodos

Este é um estudo de coorte prospectiva que incluiu os pacientes admitidos à unidade de terapia intensiva de um hospital terciário no sul do Brasil entre março e dezembro de 2019. Incluíram-se os pacientes que necessitaram de ventilação mecânica por pelo menos 24 horas e foram extubados durante o período do estudo. O desfecho primário foi falha da extubação, considerada como necessidade de reintubar dentro das primeiras 72 horas após a extubação. O desfecho secundário foi um desfecho combinado de falha da extubação ou necessidade de ventilação não invasiva terapêutica.

Resultados

Foram incluídos 101 pacientes. Observou-se falha da extubação em 29 (28,7%) deles. Na análise univariada, pacientes com balanço hídrico negativo acima de 1L no período de 48 horas após a extubação tiveram menor taxa de falha da extubação (12,0%), em comparação a pacientes com balanço hídrico negativo nas 48 horas após a extubação menor que 1L (34,2%; p = 0,033). A duração da ventilação mecânica e o balanço hídrico negativo nas 48 horas após a extubação inferior a 1L se associaram com falha da extubação na análise multivariada quando corrigido pelo Simplified Acute Physiology Score 3. Quando avaliou-se o desfecho combinado, apenas o balanço hídrico nas 48 horas pós-extubação inferior a 1L manteve associação, quando corrigido pelo Simplified Acute Physiology Score 3 e duração da ventilação mecânica.

Conclusão

O balanço hídrico nas 48 horas após a extubação se associa com falha da extubação. São necessários mais estudos para avaliar se evitar um balanço hídrico positivo nesse período poderia melhorar os desfechos do desmame.

Noninvasive ventilation versus conventional oxygen therapy after extubation failure in high-risk patients in an intensive care unit: a pragmatic clinical trial

Objetivo

Determinar la efectividad de la ventilación no invasiva frente a oxigenoterapia convencional en pacientes con insuficiencia respiratoria aguda tras fracaso de la extubación.

Métodos

Ensayo clínico pragmático realizado una unidad de cuidados intensivos de marzo de 2009 a septiembre de 2016. Se incluyeron pacientes sometidos a ventilación mecánica > 24 horas, y que desarrollaron insuficiencia respiratoria aguda tras extubación programada, siendo asignados a ventilación no invasiva u oxigenoterapia convencional. El objetivo primario fue reducir la tasa de reintubación. Los objetivos secundarios fueron: mejora de los parámetros respiratorios, reducción de las complicaciones, de la duración de la ventilación mecánica, de la estancia en unidad de cuidados intensivos y hospitalaria, así como de la mortalidad en unidad de cuidados intensivos, hospitalaria y a los 90 días. También se analizaron los factores relacionados con la reintubación.

Resultados

De un total de 2.574 pacientes, se analizaron 77 (38 en el grupo de ventilación no invasiva y 39 en el grupo de oxigenoterapia convencional). La ventilación no invasiva redujo la frecuencia respiratoria y cardíaca más rápidamente que la oxigenoterapia convencional. La reintubación fue menor en el grupo de ventilación no invasiva [12 (32%) versus 22(56%) en grupo oxigenoterapia convencional, RR 0,58 (IC95% 0,34 - 0,97), p = 0,039], el resto de los parámetros no mostró diferencias significativas. En el análisis multivariante, la ventilación no invasiva prevenía la reintubación [OR 0,17 (IC95% 0,05 - 0,56), p = 0,004], mientras que el fracaso hepático previo a la extubación y la incapacidad para mantener vía aérea permeable predisponían a la reintubación.

Conclusión

El empleo de la ventilación no invasiva en pacientes que fracasa la extubación podría ser beneficiosa frente a la oxigenoterapia convencional.

Effects of high-flow nasal oxygen cannula versus other noninvasive ventilation in extubated patients: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

A systematic review and meta-analysis were performed to compare the effects of high-flow nasal oxygen cannula (HFNC) and noninvasive ventilation (NIV) in extubated patients with respiratory insufficiency.

METHODS

The Cochrane Library, PubMed, and ClinicalTrials.gov were searched from inception to 28 February 2021, to identify randomized controlled trials. The primary outcome was reintubation within 24-72 hours after a planned extubation. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated.

RESULTS

Six articles with1746 patients were included. The effect of HFNC on the reintubation rate was noninferior to that of NIV (OR = 1.11, 95% CI: 0.85-1.44). The rate of treatment failure was 20.40% with HFNC versus 20.92% with NIV; this difference was nonsignificant (OR = 0.97, 95% CI: 0.72-1.32, P = 0.85). HFNC reduced the rates of skin lesion occurrence (10.28% versus 23.82%, OR = 0.37, 95% CI: 0.26-0.53, P < 0.00001) and post-extubation respiratory failure (23.76% versus 25.56%, OR = 0.64, 95% CI: 0.46-0.88, P = 0.006), compared with NIV.

CONCLUSIONS

In extubated patients, HFNC was noninferior to NIV in the rate of reintubation and treatment failure. Compared with NIV, HFNC decreased the occurrence of skin lesions and post-extubation respiratory failure.

Cough peak flow to predict extubation outcome: a systematic review and meta-analysis

Objetivo

Avaliar a utilidade do pico de fluxo da tosse para predizer o desfecho da extubação em pacientes que obtiveram sucesso no teste de respiração espontânea.

Métodos

A busca cobriu as bases de dados científicos MEDLINE^®, Lilacs, Ibecs, Cinahl, SciELO, Cochrane, Scopus, Web of Science e literatura cinzenta. Utilizaram-se os critérios Quality Assessment of Diagnostic Accuracy Studies para avaliar a qualidade da metodologia e o risco de viés dos estudos. A heterogeneidade estatística da razão de verossimilhança (LR) e razão de chance diagnóstica (RCD) do diagnóstico foram avaliadas com utilização de gráficos em floresta, teste Q de Cochran e um gráfico crosshair summary Receiver Operating Characteristic, utilizando um modelo com múltiplos pontos de corte.

Resultados

Inicialmente obteve-se, nas bases de dados, um total de 3.522 referências; dentre estas, selecionaram-se para análise qualitativa 12 estudos que incluíram 1.757 participantes. Muitos estudos apresentavam um risco de viés incerto em termos da seleção de pacientes e do fluxo e tempo. Dentre os 12 estudos incluídos, sete tinham alto risco e cinco risco incerto para o item padrão de referência. O desempenho diagnóstico do pico de fluxo da tosse para o resultado da extubação foi baixo a moderado quando se consideram os resultados de todos os estudos incluídos, com +LR de 1,360 (IC95% 1,240 - 1,530), -LR de 0,218 (IC95% 0,159 - 0,293) e razão de chance diagnóstica de 6,450 (IC95% 4,490 - 9,090). Uma análise de subgrupos que incluiu somente estudos com valores de corte entre 55 e 65 L/minuto demonstrou desempenho ligeiramente melhor, porém ainda moderado.

Conclusão

A avaliação do pico de fluxo da tosse, considerando valor de corte entre 55 e 65 L/minuto, pode ser útil como medida complementar antes da extubação. São necessários estudos com melhor delineamento para elucidar o melhor método e equipamento para registrar o pico de fluxo da tosse, assim como o melhor ponto de corte.

Continuous enteral nutrition compared with a maximal gastric vacuity strategy at the time of extubation in the intensive care unit: protocol for a non-inferiority cluster randomised trial (the Ambroisie Project)

INTRODUCTION

Fasting is frequently imposed to patients before extubation in the intensive care unit based on scheduled surgery guidelines. This practice has never been evaluated among critically ill patients and may delay extubation, increase nursing workload and reduce caloric intake. We are hypothesising that continuous enteral nutrition until extubation represents a safe alternative compared with fasting prior to extubation in the intensive care unit.

METHODS AND ANALYSIS

Adult patients ventilated more than 48 hours and receiving pre-pyloric enteral nutrition for more than 24 hours are included in this open-label cluster randomised parallel group non-inferiority trial. The participating centres are randomised allocated to continued enteral nutrition until extubation or 6-hour fasting (with concomitant gastric suctioning when feasible) prior to extubation. The primary outcome is extubation failure (ie, reintubation within 7 days following extubation).

ETHICS AND DISSEMINATION

This study has been approved by the national ethics review board (comité de protection, des personnes Sud Mediterranée III No 2017.10.02 bis) and patients are included after informed consent. Results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT03335345).

Development and Validation of a Risk Score for Respiratory Failure After Cardiac Surgery

BACKGROUND

Postoperative respiratory failure, defined as ventilator dependency for more than 48 hours or unplanned reintubation within 30 days, is a costly complication of cardiac surgery that increases mortality and length of stay. Stratification of patients by risk upon intensive care unit admission could identify cases requiring early measures to prevent respiratory failure. This study aimed to develop and validate a risk score for postoperative respiratory failure after cardiac surgery.

METHODS

This retrospective analysis of 4262 patients admitted to the cardiovascular intensive care unit after major cardiac surgery between 01/2013 and 12/2017, used the Society of Thoracic Surgeons database and ventilator data from the respiratory therapy department. Patients were randomly and equally assigned to development and validation cohorts. Covariates used in the multivariable models were assigned weighted points proportional to their β regression coefficient values to create the risk score, which categorized patients into low, medium, and high risk of postoperative respiratory failure.

RESULTS

In both cohorts, postoperative respiratory failure risk was significantly different between risk categories. Compared to low-risk patients, moderate-risk patients had a two times greater risk, and high-risk patients had a four to seven times greater risk. Body mass index, previous cardiac surgery, cardiopulmonary bypass, cardiogenic shock, pulmonary disease presence, baseline functional status, hemodynamic instability, and number of blood products used intraoperatively were significant predictors of respiratory failure.

CONCLUSIONS

This risk score can stratify patients by risk for developing postoperative respiratory failure after major cardiac surgery, which may help in the development of preventive measures.

Early detection of evolving critical illness myopathy with muscle velocity recovery cycles

OBJECTIVE

To investigate the sensitivity of muscle velocity recovery cycles (MVRCs) for detecting altered membrane properties in critically ill patients, and to compare this to conventional nerve conduction studies (NCS) and quantitative electromyography (qEMG).

METHODS

Twenty-four patients with intensive care unit acquired weakness (ICUAW) and 34 healthy subjects were prospectively recruited. In addition to NCS (median, ulnar, peroneal, tibial and sural nerves) and qEMG (biceps brachii, vastus medialis and anterior tibial muscles), MVRCs with frequency ramp were recorded from anterior tibial muscle.

RESULTS

MVRC and frequency ramp parameters showed abnormal muscle fiber membrane properties with up to 100% sensitivity and specificity. qEMG showed myopathy in 15 patients (63%) while polyneuropathy was seen in 3 (13%). Decreased compound muscle action potential (CMAP) amplitude (up to 58%) and absent F-waves (up to 75%) were frequent, but long duration CMAPs were only seen in one patient with severe myopathy.

CONCLUSIONS

Altered muscle fiber membrane properties can be detected in patients with ICUAW not yet fulfilling diagnostic criteria for critical illness myopathy (CIM). MVRCs may therefore serve as a tool for early detection of evolving CIM.

SIGNIFICANCE

CIM is often under-recognized by intensivists, and large-scale longitudinal studies are needed to determine its incidence and pathogenesis.

Preventive use of respiratory support after scheduled extubation in critically ill medical patients-a network meta-analysis of randomized controlled trials

BACKGROUND

Respiratory support has been increasingly used after extubation for the prevention of re-intubation and improvement of prognosis in critically ill medical patients. However, the optimal respiratory support method is still under debate. This network meta-analysis (NMA) aims to evaluate the comparative effectiveness of various respiratory support methods used for preventive purposes after scheduled extubation in critically ill medical patients.

METHODS

A systematic database search was performed from inception to December 19, 2019, for randomized controlled trials (RCTs) that compared a preventive use of different respiratory support methods, including conventional oxygen therapy (COT), noninvasive ventilation (NIV), high-flow oxygen therapy (HFOT), and combinational use of HFOT and NIV (HFOT+NIV), after planned extubation in adult critically ill medical patients. Study selection, data extraction, and quality assessments were performed in duplicate. The primary outcomes included re-intubation rate and short-term mortality.

RESULTS

Seventeen RCTs comprising 3341 participants with 4 comparisons were included. Compared with COT, NIV significantly reduced the re-intubation rate [risk ratio (RR) 0.55, 95% confidence interval (CI) 0.39 to 0.77; moderate quality of evidence] and short-term mortality (RR 0.66, 95% CI 0.48 to 0.91; moderate quality of evidence). Compared to COT, HFOT had a beneficial effect on the re-intubation rate (RR 0.55, 95% CI 0.35 to 0.86; moderate quality of evidence) but no effect on short-term mortality (RR 0.79, 95% CI 0.56 to 1.12; low quality of evidence). No significant difference in the re-intubation rate or short-term mortality was found among NIV, HFOT, and HFOT+NIV. The treatment rankings based on the surface under the cumulative ranking curve (SUCRA) from best to worst for re-intubation rate were HFOT+NIV (95.1%), NIV (53.4%), HFOT (51.2%), and COT (0.3%), and the rankings for short-term mortality were NIV (91.0%), HFOT (54.3%), HFOT+NIV (43.7%), and COT (11.1%). Sensitivity analyses of trials with a high risk of extubation failure for the primary outcomes indicated that the SUCRA rankings were comparable to those of the primary analysis.

CONCLUSIONS

After scheduled extubation, the preventive use of NIV is probably the most effective respiratory support method for comprehensively preventing re-intubation and short-term death in critically ill medical patients, especially those with a high risk of extubation failure.

Noninvasive respiratory support in the hypoxaemic peri-operative/periprocedural patient: a joint ESA/ESICM guideline

Hypoxaemia is a potential life-threatening yet common complication in the peri-operative and periprocedural patient (e.g. during an invasive procedure at risk of deterioration of gas exchange, such as bronchoscopy). The European Society of Anaesthesiology (ESA) and the European Society of Intensive Care Medicine (ESICM) developed guidelines for the use of noninvasive respiratory support techniques in the hypoxaemic patient in the peri-operative and periprocedural period. The panel outlined five clinical questions regarding treatment with noninvasive respiratory support techniques [conventional oxygen therapy (COT), high flow nasal cannula, noninvasive positive pressure ventilation (NIPPV) and continuous positive airway pressure (CPAP)] for hypoxaemic patients with acute peri-operative/periprocedural respiratory failure. The goal was to assess the available literature on the various noninvasive respiratory support techniques, specifically studies that included adult participants with hypoxaemia in the peri-operative/periprocedural period. The literature search strategy was developed by a Cochrane Anaesthesia and Intensive Care trial search specialist in close collaboration with the panel members and the ESA group methodologist. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system was used to assess the level of evidence and to grade recommendations. The final process was then validated by both ESA and ESICM scientific committees. Among 19 recommendations, the two grade 1B recommendations state that: in the peri-operative/periprocedural hypoxaemic patient, the use of either NIPPV or CPAP (based on local expertise) is preferred to COT for improvement of oxygenation; and that the panel suggests using NIPPV or CPAP immediately post-extubation for hypoxaemic patients at risk of developing acute respiratory failure after abdominal surgery.

ERS International Congress, Madrid, 2019: highlights from the Respiratory Intensive Care Assembly

The Respiratory Intensive Care Assembly of the European Respiratory Society is delighted to present the highlights from the 2019 International Congress in Madrid, Spain. We have selected four sessions that discussed recent advances in a wide range of topics: from acute respiratory failure to cough augmentation in neuromuscular disorders and from extra-corporeal life support to difficult ventilator weaning. The subjects are summarised by early career members in close collaboration with the Assembly leadership. We aim to give the reader an update on the most important developments discussed at the conference. Each session is further summarised into a short list of take-home messages.

Early decongestive therapy versus high-flow nasal cannula for the prevention of adverse clinical events in patients with acute cardiogenic pulmonary edema

Background

Few studies have investigated the role of decongestive therapy and high-flow nasal cannula (HFNC) in preventing reintubation and in-hospital mortality in patients with acute cardiogenic pulmonary edema (ACPE).

Methods

Data from patients with ACPE who were weaned from mechanical ventilation in the cardiac intensive care unit between January 2013 and December 2017 were retrospectively evaluated. All patients were treated with HFNC or conventional oxygen therapy (COT), such as a nasal cannula or venturi mask, immediately after extubation. Decongestive therapy (intravenous furosemide infusion) was administered at the discretion of the attending physician.

Results

Of 212 patients treated during the study period, 47 were excluded due to recent open-heart surgery and two, due to insufficient clinical data. The remaining 163 patients had a mean age of 67.4±14.3 years, and 92 (56.4%) were male; 44 patients received HFNC, and 119 COT. Mean weight loss within 72 hours of extubation was -0.86±2.03 kg. A total of 38 patients (23.3%) required reintubation, 21 of whom (12.9%) required reintubation within 72 hours of extubation. In-hospital mortality occurred in 16 patients (9.8%). Multivariate analysis showed that weight increase within 72 hours of extubation was independent determinants of reintubation (OR =1.7; 95% CI: 1.2-2.2; P<0.001) and in-hospital mortality (OR =1.5; 95% CI: 1.1-2.1; P=0.005). The use of HFNC was not associated with reintubation or in-hospital mortality.

Conclusions

Our findings indicate that early weight loss resulted in reduced reintubation and in-hospital mortality in patients with ACPE. However, HFNC and COT did not differ in the prevention of reintubation and in-hospital mortality. Therefore, aggressive decongestive therapy, rather than HFNC, should be considered early after extubation.

Early nasal high-flow versus Venturi mask oxygen therapy after lung resection: a randomized trial

Background

Data on high-flow nasal oxygen after thoracic surgery are limited and confined to the comparison with low-flow oxygen. Different from low-flow oxygen, Venturi masks provide higher gas flow at a predetermined fraction of inspired oxygen (FiO₂). We conducted a randomized trial to determine whether preemptive high-flow nasal oxygen reduces the incidence of postoperative hypoxemia after lung resection, as compared to Venturi mask oxygen therapy.

Methods

In this single-center, randomized trial conducted in a teaching hospital in Italy, consecutive adult patients undergoing thoracotomic lung resection, who were not on long-term oxygen therapy, were randomly assigned to receive high-flow nasal or Venturi mask oxygen after extubation continuously for two postoperative days. The primary outcome was the incidence of postoperative hypoxemia (i.e., ratio of the partial pressure of arterial oxygen to FiO₂ (PaO₂/FiO₂) lower than 300 mmHg) within four postoperative days.

Results

Between September 2015 and April 2018, 96 patients were enrolled; 95 patients were analyzed (47 in high-flow group and 48 in Venturi mask group). In both groups, 38 patients (81% in the high-flow group and 79% in the Venturi mask group) developed postoperative hypoxemia, with an unadjusted odds ratio (OR) for the high-flow group of 1.11 [95% confidence interval (CI) 0.41–3] (p = 0.84). No inter-group differences were found in the degree of dyspnea nor in the proportion of patients needing oxygen therapy after treatment discontinuation (OR 1.34 [95% CI 0.60–3]), experiencing pulmonary complications (OR 1.29 [95% CI 0.51–3.25]) or requiring ventilatory support (OR 0.67 [95% CI 0.11–4.18]). Post hoc analyses revealed that PaO₂/FiO₂ during the study was not different between groups (p = 0.92), but patients receiving high-flow nasal oxygen had lower arterial pressure of carbon dioxide, with a mean inter-group difference of 2 mmHg [95% CI 0.5–3.4] (p = 0.009), and were burdened by a lower risk of postoperative hypercapnia (adjusted OR 0.18 [95% CI 0.06–0.54], p = 0.002).

Conclusions

When compared to Venturi mask after thoracotomic lung resection, preemptive high-flow nasal oxygen did not reduce the incidence of postoperative hypoxemia nor improved other analyzed outcomes. Further adequately powered investigations in this setting are warranted to establish whether high-flow nasal oxygen may yield clinical benefit on carbon dioxide clearance.

Trial registration

ClinicalTrials.gov, NCT02544477. Registered 9 September 2015.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2361-5) contains supplementary material, which is available to authorized users.