Wean earlier and automatically with new technology (the WEAN study). A multicenter, pilot randomized controlled trial

Prediction of Spontaneous Breathing Trial Outcome in Critically Ill-Ventilated Patients Using Deep Learning: Development and Verification Study

BACKGROUND

Long-term ventilator-dependent patients often face problems such as decreased quality of life, increased mortality, and increased medical costs. Respiratory therapists must perform complex and time-consuming ventilator weaning assessments, which typically take 48-72 hours. Traditional disengagement methods rely on manual evaluation and are susceptible to subjectivity, human errors, and low efficiency.

OBJECTIVE

This study aims to develop an artificial intelligence-based prediction model to predict whether a patient can successfully pass a spontaneous breathing trial (SBT) using the patient's clinical data collected before SBT initiation. Instead of comparing different SBT strategies or analyzing their impact on extubation success, this study focused on establishing a data-driven approach under a fixed SBT strategy to provide an objective and efficient assessment tool. Through this model, we aim to enhance the accuracy and efficiency of ventilator weaning assessments, reduce unnecessary SBT attempts, optimize intensive care unit resource usage, and ultimately improve the quality of care for ventilator-dependent patients.

METHODS

This study used a retrospective cohort study and developed a novel deep learning architecture, hybrid CNN-MLP (convolutional neural network-multilayer perceptron), for analysis. Unlike the traditional CNN-MLP classification method, hybrid CNN-MLP performs feature learning and fusion by interleaving CNN and MLP layers so that data features can be extracted and integrated at different levels, thereby improving the flexibility and prediction accuracy of the model. The study participants were patients aged 20 years or older hospitalized in the intensive care unit of a medical center in central Taiwan between January 1, 2016, and December 31, 2022. A total of 3686 patients were included in the study, and 6536 pre-SBT clinical records were collected before each SBT of these patients, of which 3268 passed the SBT and 3268 failed.

RESULTS

The model performed well in predicting SBT outcomes. The training dataset's precision is 99.3% (2443/2460 records), recall is 93.5% (2443/2614 records), specificity is 99.3% (2597/2614 records), and F1-score is 0.963. In the test dataset, the model maintains accuracy with a precision of 89.2% (561/629 records), a recall of 85.8% (561/654 records), a specificity of 89.6% (586/654 records), and an F1-score of 0.875. These results confirm the reliability of the model and its potential for clinical application.

CONCLUSIONS

This study successfully developed a deep learning-based SBT prediction model that can be used as an objective and efficient ventilator weaning assessment tool. The model's performance shows that it can be integrated into clinical workflow, improve the quality of patient care, and reduce ventilator dependence, which is an important step in improving the effectiveness of respiratory therapy.

Evaluation of decision support to wean patients from mechanical ventilation in intensive care: a prospective study reporting clinical and physiological outcomes

This study investigated the clinical and physiological response to use of the BEACON Caresystem, a bedside open-loop decision support system providing advice to guide clinicians when weaning patients from invasive mechanical ventilation. Multicenter prospective study conducted in five adult intensive care units in the UK. Following screening and assent, intubated patients mechanically ventilated for > 24 h were randomized to intervention or usual care. Intervention consisted of application of the BEACON Caresystem's advice on tidal volume/inspiratory pressure, inspired oxygen, respiratory rate and PEEP. Usual care was defined as local clinical practice. The primary outcome was duration of mechanical ventilation. Secondary outcomes quantified prolonged intubation and survival; adverse events; ventilator settings and physiological state; time spent in ventilator modes; links to other therapy; the frequency of advice utilization and time spent outside normal physiological limits. The study was terminated early with a total of 112 patients included. Fifty-four were randomised to the intervention arm and fifty-eight to usual care. The study was underpowered and no significant differences were seen in duration of mechanical ventilation (p = 0.773), prolonged intubation or survival. Intervention arm patients had lower rates of adverse events (p = 0.016), including fewer hypoxaemic events (p = 0.008) and lower values of PEEP (p = 0.030) and tidal volume (p = 0.042). Values of peak inspiratory pressure and pressure support were reduced but at the boarder of statistical significance (p = 0.104, p = 0.093, respectively). No differences were seen for time in ventilator mode or other therapy. Advice presented by the decision support system was applied at the beside an average of 88% of occasions, with a significantly increased number of changes only in inspired oxygen fraction. No significant differences were seen in time spent outside physiological limits. This study investigated the use of the BEACON Caresystem, an open loop clinical decision support system providing advice on ventilator settings. It was terminated early, with no significant difference shown in duration of mechanical ventilation, the primary outcome. Application of advice indicated potential for fewer adverse events and improved physiological status. (Trial registration ClinicalTrials.gov under NCT03249623. Registered 22nd June 2017).

Frequency of Screening and Spontaneous Breathing Trial Techniques: A Randomized Clinical Trial

Importance

The optimal screening frequency and spontaneous breathing trial (SBT) technique to liberate adults from ventilators are unknown.

Objective

To compare the effects of screening frequency (once-daily screening vs more frequent screening) and SBT technique (pressure-supported SBT with a pressure support level that was >0-≤8 cm H2O and a positive end-expiratory pressure [PEEP] level that was >0-≤5 cm H2O vs T-piece SBT) on the time to successful extubation.

Design, Setting, and Participants

Randomized clinical trial with a 2 × 2 factorial design including critically ill adults who were receiving invasive mechanical ventilation for at least 24 hours, who were capable of initiating spontaneous breaths or triggering ventilators, and who were receiving a fractional concentration of inspired oxygen that was 70% or less and a PEEP level of 12 cm H2O or less. Recruitment was between January 2018 and February 2022 at 23 intensive care units in North America; last follow-up occurred October 18, 2022.

Interventions

Participants were enrolled early to enable protocolized screening (more frequent vs once daily) to identify the earliest that patients met criteria to undergo pressure-supported or T-piece SBT lasting 30 to 120 minutes.

Main Outcome and Measures

Time to successful extubation (time when unsupported, spontaneous breathing began and was sustained for ≥48 hours after extubation).

Results

Of 797 patients (198 in the once-daily screening and pressure-supported SBT group, 204 in once-daily screening and T-piece SBT, 195 in more frequent screening and pressure-supported SBT, and 200 in more frequent screening and T-piece SBT), the mean age was 62.4 (SD, 18.4) years and 472 (59.2%) were men. There were no statistically significant differences by screening frequency (hazard ratio [HR], 0.88 [95% CI, 0.76-1.03]; P = .12) or by SBT technique (HR, 1.06 [95% CI, 0.91-1.23]; P = .45). The median time to successful extubation was 2.0 days (95% CI, 1.7-2.7) for once-daily screening and pressure-supported SBT, 3.1 days (95% CI, 2.7-4.8) for once-daily screening and T-piece SBT, 3.9 days (95% CI, 2.9-4.7) for more frequent screening and pressure-supported SBT, and 2.9 days (95% CI, 2.0-3.1) for more frequent screening and T-piece SBT. An unexpected interaction between screening frequency and SBT technique required pairwise contrasts that revealed more frequent screening (vs once-daily screening) and pressure-supported SBT increased the time to successful extubation (HR, 0.70 [95% CI, 0.50-0.96]; P = .02). Once-daily screening and pressure-supported SBT (vs T-piece SBT) did not reduce the time to successful extubation (HR, 1.30 [95% CI, 0.98-1.70]; P = .08).

Conclusions and Relevance

Among critically ill adults who received invasive mechanical ventilation for more than 24 hours, screening frequency (once-daily vs more frequent screening) and SBT technique (pressure-supported vs T-piece SBT) did not change the time to successful extubation. However, an unexpected and statistically significant interaction was identified; protocolized more frequent screening combined with pressure-supported SBTs increased the time to first successful extubation.

Trial Registration

ClinicalTrials.gov Identifiers: NCT02399267 and NCT02969226.

A randomized control trial evaluating the advice of a physiological-model/digital twin-based decision support system on mechanical ventilation in patients with acute respiratory distress syndrome

Background

Acute respiratory distress syndrome (ARDS) is highly heterogeneous, both in its clinical presentation and in the patient's physiological responses to changes in mechanical ventilator settings, such as PEEP. This study investigates the clinical efficacy of a physiological model-based ventilatory decision support system (DSS) to personalize ventilator therapy in ARDS patients.

Methods

This international, multicenter, randomized, open-label study enrolled patients with ARDS during the COVID-19 pandemic. Patients were randomized to either receive active advice from the DSS (intervention) or standard care without DSS advice (control). The primary outcome was to detect a reduction in average driving pressure between groups. Secondary outcomes included several clinically relevant measures of respiratory physiology, ventilator-free days, time from control mode to support mode, number of changes in ventilator settings per day, percentage of time in control and support mode ventilation, ventilation- and device-related adverse events, and the number of times the advice was followed.

Results

A total of 95 patients were randomized in this study. The DSS showed no significant effect on average driving pressure between groups. However, patients in the intervention arm had a statistically improved oxygenation index when in support mode ventilation (-1.41, 95% CI: -2.76, -0.08; p = 0.0370). Additionally, the ventilatory ratio significantly improved in the intervention arm for patients in control mode ventilation (-0.63, 95% CI: -1.08, -0.17, p = 0.0068). The application of the DSS led to a significantly increased number of ventilator changes for pressure settings and respiratory frequency.

Conclusion

The use of a physiological model-based decision support system for providing advice on mechanical ventilation in patients with COVID-19 and non-COVID-19 ARDS showed no significant difference in driving pressure as a primary outcome measure. However, the application of approximately 60% of the DSS advice led to improvements in the patient's physiological state.

Clinical trial registration

clinicaltrials.gov, NCT04115709.

Effects of closed loop ventilation on ventilator settings, patient outcomes and ICU staff workloads - a systematic review

BACKGROUND

Lung protective ventilation is considered standard of care in the intensive care unit. However, modifying the ventilator settings can be challenging and is time consuming. Closed loop modes of ventilation are increasingly attractive for use in critically ill patients. With closed loop ventilation, settings that are typically managed by the ICU professionals are under control of the ventilator's algorithms.

OBJECTIVES

To describe the effectiveness, safety, efficacy and workload with currently available closed loop ventilation modes.

DESIGN

Systematic review of randomised clinical trials.

DATA SOURCES

A comprehensive systematic search in PubMed, Embase and the Cochrane Central register of Controlled Trials search was performed in January 2023.

ELIGIBILITY CRITERIA

Randomised clinical trials that compared closed loop ventilation with conventional ventilation modes and reported on effectiveness, safety, efficacy or workload.

RESULTS

The search identified 51 studies that met the inclusion criteria. Closed loop ventilation, when compared with conventional ventilation, demonstrates enhanced management of crucial ventilator variables and parameters essential for lung protection across diverse patient cohorts. Adverse events were seldom reported. Several studies indicate potential improvements in patient outcomes with closed loop ventilation; however, it is worth noting that these studies might have been underpowered to conclusively demonstrate such benefits. Closed loop ventilation resulted in a reduction of various aspects associated with the workload of ICU professionals but there have been no studies that studied workload in sufficient detail.

CONCLUSIONS

Closed loop ventilation modes are at least as effective in choosing correct ventilator settings as ventilation performed by ICU professionals and have the potential to reduce the workload related to ventilation. Nevertheless, there is a lack of sufficient research to comprehensively assess the overall impact of these modes on patient outcomes, and on the workload of ICU staff.

The PROMIZING trial enrollment algorithm for early identification of patients ready for unassisted breathing

Background

Liberating patients from mechanical ventilation (MV) requires a systematic approach. In the context of a clinical trial, we developed a simple algorithm to identify patients who tolerate assisted ventilation but still require ongoing MV to be randomized. We report on the use of this algorithm to screen potential trial participants for enrollment and subsequent randomization in the Proportional Assist Ventilation for Minimizing the Duration of MV (PROMIZING) study.

Methods

The algorithm included five steps: enrollment criteria, pressure support ventilation (PSV) tolerance trial, weaning criteria, continuous positive airway pressure (CPAP) tolerance trial (0 cmH₂O during 2 min) and spontaneous breathing trial (SBT): on fraction of inspired oxygen (F_iO₂) 40% for 30–120 min. Patients who failed the weaning criteria, CPAP Zero trial, or SBT were randomized. We describe the characteristics of patients who were initially enrolled, but passed all steps in the algorithm and consequently were not randomized.

Results

Among the 374 enrolled patients, 93 (25%) patients passed all five steps. At time of enrollment, most patients were on PSV (87%) with a mean (± standard deviation) F_iO₂ of 34 (± 6) %, PSV of 8.7 (± 2.9) cmH₂O, and positive end-expiratory pressure of 6.1 (± 1.6) cmH₂O. Minute ventilation was 9.0 (± 3.1) L/min with a respiratory rate of 17.4 (± 4.4) breaths/min. Patients were liberated from MV with a median [interquartile range] delay between initial screening and extubation of 5 [1–49] hours. Only 7 (8%) patients required reintubation.

Conclusion

The trial algorithm permitted identification of 93 (25%) patients who were ready to extubate, while their clinicians predicted a duration of ventilation higher than 24 h.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04063-4.

Neurally Adjusted Ventilatory Assist in Acute Respiratory Failure-A Narrative Review

Maintaining spontaneous breathing has both potentially beneficial and deleterious consequences in patients with acute respiratory failure, depending on the balance that can be obtained between the protecting and damaging effects on the lungs and the diaphragm. Neurally adjusted ventilatory assist (NAVA) is an assist mode, which supplies the respiratory system with a pressure proportional to the integral of the electrical activity of the diaphragm. This proportional mode of ventilation has the theoretical potential to deliver lung- and respiratory-muscle-protective ventilation by preserving the physiologic defense mechanisms against both lung overdistention and ventilator overassistance, as well as reducing the incidence of diaphragm disuse atrophy while maintaining patient–ventilator synchrony. This narrative review presents an overview of NAVA technology, its basic principles, the different methods to set the assist level and the findings of experimental and clinical studies which focused on lung and diaphragm protection, machine–patient interaction and preservation of breathing pattern variability. A summary of the findings of the available clinical trials which investigate the use of NAVA in acute respiratory failure will also be presented and discussed.

Comparison of advanced closed-loop ventilation modes with pressure support ventilation for weaning from mechanical ventilation in adults: A systematic review and meta-analysis

PURPOSE

To compare neurally adjusted ventilatory assist (NAVA), proportional assist ventilation (PAV), adaptive support ventilation (ASV) and Smartcare pressure support (Smartcare/PS) with standard pressure support ventilation (PSV) regarding their effectiveness for weaning critically ill adults from invasive mechanical ventilation (IMV).

METHODS

Electronic databases were searched to identify parallel-group randomized controlled trials (RCTs) comparing NAVA, PAV, ASV, or Smartcare/PS with PSV, in adult patients under IMV through July 28, 2021. Primary outcome was weaning success. Secondary outcomes included weaning time, total MV duration, reintubation or use of non-invasive MV (NIMV) within 48 h after extubation, in-hospital and intensive care unit (ICU) mortality, in-hospital and ICU length of stay (LOS) (PROSPERO registration No:CRD42021270299).

RESULTS

Twenty RCTs were finally included. Compared to PSV, NAVA was associated with significantly lower risk for in-hospital and ICU death and lower requirements for post-extubation NIMV. Moreover, PAV showed significant advantage over PSV in terms of weaning rates, MV duration and ICU LOS. No significant differences were found between ASV or Smart care/PS and PSV.

CONCLUSIONS

Moderate certainty evidence suggest that PAV increases weaning success rates, shortens MV duration and ICU LOS compared to PSV. It is also noteworthy that NAVA seems to improve in-hospital and ICU survival.

Choosing Wisely For Critical Care: The Next Five

OBJECTIVES

To formulate new "Choosing Wisely" for Critical Care recommendations that identify best practices to avoid waste and promote value while providing critical care.

DATA SOURCES

Semistructured narrative literature review and quantitative survey assessments.

STUDY SELECTION

English language publications that examined critical care practices in relation to reducing cost or waste.

DATA EXTRACTION

Practices assessed to add no value to critical care were grouped by category. Taskforce assessment, modified Delphi consensus building, and quantitative survey analysis identified eight novel recommendations to avoid wasteful critical care practices. These were submitted to the Society of Critical Care Medicine membership for evaluation and ranking.

DATA SYNTHESIS

Results from the quantitative Society of Critical Care Medicine membership survey identified the top scoring five of eight recommendations. These five highest ranked recommendations established Society of Critical Care Medicine's Next Five "Choosing" Wisely for Critical Care practices.

CONCLUSIONS

Five new recommendations to reduce waste and enhance value in the practice of critical care address invasive devices, proactive liberation from mechanical ventilation, antibiotic stewardship, early mobilization, and providing goal-concordant care. These recommendations supplement the initial critical care recommendations from the "Choosing Wisely" campaign.

Prolonged Weaning: S2k Guideline Published by the German Respiratory Society

Mechanical ventilation (MV) is an essential part of modern intensive care medicine. MV is performed in patients with severe respiratory failure caused by respiratory muscle insufficiency and/or lung parenchymal disease; that is, when other treatments such as medication, oxygen administration, secretion management, continuous positive airway pressure (CPAP), or nasal high-flow therapy have failed. MV is required for maintaining gas exchange and allows more time to curatively treat the underlying cause of respiratory failure. In the majority of ventilated patients, liberation or "weaning" from MV is routine, without the occurrence of any major problems. However, approximately 20% of patients require ongoing MV, despite amelioration of the conditions that precipitated the need for it in the first place. Approximately 40-50% of the time spent on MV is required to liberate the patient from the ventilator, a process called "weaning". In addition to acute respiratory failure, numerous factors can influence the duration and success rate of the weaning process; these include age, comorbidities, and conditions and complications acquired during the ICU stay. According to international consensus, "prolonged weaning" is defined as the weaning process in patients who have failed at least 3 weaning attempts, or require more than 7 days of weaning after the first spontaneous breathing trial (SBT). Given that prolonged weaning is a complex process, an interdisciplinary approach is essential for it to be successful. In specialised weaning centres, approximately 50% of patients with initial weaning failure can be liberated from MV after prolonged weaning. However, the heterogeneity of patients undergoing prolonged weaning precludes the direct comparison of individual centres. Patients with persistent weaning failure either die during the weaning process, or are discharged back to their home or to a long-term care facility with ongoing MV. Urged by the growing importance of prolonged weaning, this Sk2 Guideline was first published in 2014 as an initiative of the German Respiratory Society (DGP), in conjunction with other scientific societies involved in prolonged weaning. The emergence of new research, clinical study findings and registry data, as well as the accumulation of experience in daily practice, have made the revision of this guideline necessary. The following topics are dealt with in the present guideline: Definitions, epidemiology, weaning categories, underlying pathophysiology, prevention of prolonged weaning, treatment strategies in prolonged weaning, the weaning unit, discharge from hospital on MV, and recommendations for end-of-life decisions. Special emphasis was placed on the following themes: (1) A new classification of patient sub-groups in prolonged weaning. (2) Important aspects of pulmonary rehabilitation and neurorehabilitation in prolonged weaning. (3) Infrastructure and process organisation in the care of patients in prolonged weaning based on a continuous treatment concept. (4) Changes in therapeutic goals and communication with relatives. Aspects of paediatric weaning are addressed separately within individual chapters. The main aim of the revised guideline was to summarize both current evidence and expert-based knowledge on the topic of "prolonged weaning", and to use this information as a foundation for formulating recommendations related to "prolonged weaning", not only in acute medicine but also in the field of chronic intensive care medicine. The following professionals served as important addressees for this guideline: intensivists, pulmonary medicine specialists, anaesthesiologists, internists, cardiologists, surgeons, neurologists, paediatricians, geriatricians, palliative care clinicians, rehabilitation physicians, intensive/chronic care nurses, physiotherapists, respiratory therapists, speech therapists, medical service of health insurance, and associated ventilator manufacturers.

Automated weaning from mechanical ventilation: Results of a Bayesian network meta-analysis

PURPOSE

Mechanical ventilation (MV) weaning is a crucial step. Automated weaning modes reduce MV duration but the question of the best automated mode remains unanswered. Our objective was to compare the major automated modes for MV weaning in critically ill and post-operative adult patients.

MATERIAL AND METHODS

We conducted a network Bayesian meta-analysis to compare different automated modes. We searched MEDLINE, EMBASE and Cochrane central registry for randomized control trials comparing automated weaning modes either to another automated mode or to standard-of-care. The primary outcome was the duration of MV weaning extracted from the original trials.

RESULTS

663 articles were screened and 26 trials (2097patients) were included in the final analysis. All automated modes included in the study (ASV°, Intellivent ASV, Smartcare, Automode°, PAV° and MRV°) outperformed standard-of-care but no automated mode reduced the duration of mechanical ventilation weaning as compared to others in the network meta-analysis.

CONCLUSION

Compared to standard weaning practice, all automated modes significantly reduced the duration of MV weaning in critically ill and post-operative adult patients. When cross-compared using a network meta-analysis, no specific mode was different in reducing the duration of MV weaning. The study was registered in PROSPERO (CRD42015024742).

Frequency of Screening for Weaning From Mechanical Ventilation: Two Contemporaneous Proof-of-Principle Randomized Controlled Trials

OBJECTIVES

It is unknown whether more frequent screening of invasively ventilated patients, identifies patients earlier for a spontaneous breathing trial, and shortens the duration of ventilation. We assessed the feasibility of conducting a large trial to evaluate screening frequency in critically ill adults in the North American context.

DESIGN

We conducted two contemporaneous, multicenter, pilot, randomized controlled trials (the LibeRation from MEchanicaL VEntilAtion and ScrEening Frequency [RELEASE] and Screening Elderly PatieNts For InclusiOn in a Weaning [SENIOR] trials) to address concerns regarding the potential for higher enrollment, fewer adverse events, and better outcomes in younger patients.

SETTING

Ten and 11 ICUs in Canada, respectively.

PATIENTS

Parallel trials of younger (RELEASE < 65 yr) and older (SENIOR ≥ 65 yr) critically ill adults invasively ventilated for at least 24 hours.

INTERVENTIONS

Each trial compared once daily screening to "at least twice daily" screening led by respiratory therapists.

MEASUREMENTS AND MAIN RESULTS

In both trials, we evaluated recruitment (aim: 1-2 patients/month/ICU) and consent rates, reasons for trial exclusion, protocol adherence (target: ≥ 80%), crossovers (aim: ≤ 10%), and the effect of the alternative screening frequencies on adverse events and clinical outcomes. We included 155 patients (53 patients [23 once daily, 30 at least twice daily] in RELEASE and 102 patients [54 once daily, 48 at least twice daily] in SENIOR). Between trials, we found similar recruitment rates (1.32 and 1.26 patients/month/ICU) and reasons for trial exclusion, high consent and protocol adherence rates (> 92%), infrequent crossovers, and few adverse events. Although underpowered, at least twice daily screening was associated with a nonsignificantly faster time to successful extubation and more successful extubations but significantly increased use of noninvasive ventilation in both trials combined.

CONCLUSIONS

Similar recruitment and consent rates, few adverse events, and comparable outcomes in younger and older patients support conduct of a single large trial in North American ICUs assessing the net clinical benefits associated with more frequent screening.

Frequency of Screening and SBT Technique Trial - North American Weaning Collaboration (FAST-NAWC): a protocol for a multicenter, factorial randomized trial

RATIONALE

In critically ill patients receiving invasive mechanical ventilation (MV), research supports the use of daily screening to identify patients who are ready to undergo a spontaneous breathing trial (SBT) followed by conduct of an SBT. However, once daily (OD) screening is poorly aligned with the continuous care provided in most intensive care units (ICUs) and the best SBT technique for clinicians to use remains controversial.

OBJECTIVES

To identify the optimal screening frequency and SBT technique to wean critically ill adults in the ICU.

METHODS

We aim to conduct a multicenter, factorial design randomized controlled trial with concealed allocation, comparing the effect of both screening frequency (once versus at least twice daily [ALTD]) and SBT technique (Pressure Support [PS] + Positive End-Expiratory Pressure [PEEP] vs T-piece) on the time to successful extubation (primary outcome) in 760 critically ill adults who are invasively ventilated for at least 24 h in 20 North American ICUs. In the OD arm, respiratory therapists (RTs) will screen study patients between 06:00 and 08:00 h. In the ALTD arm, patients will be screened at least twice daily between 06:00 and 08:00 h and between 13:00 and 15:00 h with additional screens permitted at the clinician's discretion. When the SBT screen is passed, an SBT will be conducted using the assigned technique (PS + PEEP or T-piece). We will follow patients until successful extubation, death, ICU discharge, or until day 60 after randomization. We will contact patients or their surrogates six months after randomization to assess health-related quality of life and functional status.

RELEVANCE

The around-the-clock availability of RTs in North American ICUs presents an important opportunity to identify the optimal SBT screening frequency and SBT technique to minimize patients' exposure to invasive ventilation and ventilator-related complications.

TRIAL REGISTRATION

Clinical Trials.gov, NCT02399267 . Registered on Nov 21, 2016 first registered.

An open-loop, physiological model based decision support system can reduce pressure support while acting to preserve respiratory muscle function

PURPOSE

To assess whether a clinical decision support system (CDSS) suggests PS and FIO₂ maintaining appropriate breathing effort, and minimizing FIO₂.

MATERIALS

Prospective, cross-over study in PS ventilated ICU patients. Over support (150% baseline) and under support (50% baseline) were applied by changing PS (15 patients) or PEEP (8 patients). CDSS advice was followed. Tension time index of inspiratory muscles (TTies), respiratory and metabolic variables were measured.

RESULTS

PS over support (median 8.0 to 12.0 cmH₂O) reduced respiratory muscle activity (TTies 0.090 ± 0.028 to 0.049 ± 0.030; p < .01), and tended to increase tidal volume (VT: 8.6 ± 3.0 to 10.1 ± 2.9 ml/kg; p = .08). CDSS advice reduced PS (6.0 cmH₂O, p = .005), increased TTies (0.076 ± 0.038, p < .01), and tended to reduce VT (8.9 ± 2.4 ml/kg, p = .08). PS under support (12.0 to 4.0 cmH₂O) slightly increased respiratory muscle activity, (TTies to 0.120 ± 0.044; p = .007) with no significant CDSS advice. CDSS advice reduced FIO₂ by 12-14% (p = .005), resulting in median SpO₂ = 96% (p < .02). PEEP changes did not result in changes in physiological variables, or CDSS advice.

CONCLUSION

The CDSS advised on low values of PS often not prohibiting extubation, while acting to preserve respiratory muscle function and preventing passive lung inflation. CDSS advice minimized FIO₂ maintaining SpO₂ at safe and beneficial values.

Les systèmes automatisés de sevrage de la ventilation mécanique ont-ils une place en pratique clinique ?

Du fait de la stagnation de l’offre démographique médicale et du vieillissement de la population, les besoins en ventilation mécanique vont croître dans les années à venir. Dans ce contexte, la conduite du sevrage de la ventilation mécanique par des systèmes automatisés est une perspective séduisante, permettant d’épargner du temps médical et infirmier. La gestion du sevrage par des systèmes automatisés repose sur l’utilisation de l’intelligence artificielle incorporée au sein de ventilateurs capables de détecter précocement la sevrabilité des patients puis d’entreprendre le cas échéant une épreuve de ventilation spontanée. Deux systèmes répondant à ce cahier des charges sont actuellement commercialisés. Bien que les données disponibles soient peu nombreuses, celles-ci semblent justifier l’intérêt pour ces systèmes en montrant au pire une équivalence, au mieux une réduction dans la durée du sevrage, lorsqu’ils sont comparés à une démarche de sevrage conventionnelle. Les défis de demain seront de tester la généralisation de ces systèmes dans la pratique clinique et de définir les caractéristiques des populations susceptibles d’en bénéficier le plus.

Trends in mechanical ventilation: are we ventilating our patients in the best possible way?

This review addresses how the combination of physiology, medicine and engineering principles contributed to the development and advancement of mechanical ventilation, emphasising the most urgent needs for improvement and the most promising directions of future development. Several aspects of mechanical ventilation are introduced, highlighting on one side the importance of interdisciplinary research for further development and, on the other, the importance of training physicians sufficiently on the technological aspects of modern devices to exploit properly the great complexity and potentials of this treatment.

EDUCATIONAL AIMS

To learn how mechanical ventilation developed in recent decades and to provide a better understanding of the actual technology and practice.To learn how and why interdisciplinary research and competences are necessary for providing the best ventilation treatment to patients.To understand which are the most relevant technical limitations in modern mechanical ventilators that can affect their performance in delivery of the treatment.To better understand and classify ventilation modes.To learn the classification, benefits, drawbacks and future perspectives of automatic ventilation tailoring algorithms.

Automated control of mechanical ventilation during general anaesthesia: study protocol of a bicentric observational study (AVAS)

INTRODUCTION

Automated control of mechanical ventilation during general anaesthesia is not common. A novel system for automated control of most of the ventilator settings was designed and is available on an anaesthesia machine.

METHODS AND ANALYSIS

The 'Automated control of mechanical ventilation during general anesthesia study' (AVAS) is an international investigator-initiated bicentric observational study designed to examine safety and efficacy of the system during general anaesthesia. The system controls mechanical breathing frequency, inspiratory pressure, pressure support, inspiratory time and trigger sensitivity with the aim to keep a patient stable in user adoptable target zones. Adult patients, who are classified as American Society of Anesthesiologists physical status I, II or III, scheduled for elective surgery of the upper or lower limb or for peripheral vascular surgery in general anaesthesia without any additional regional anaesthesia technique and who gave written consent for study participation are eligible for study inclusion. Primary endpoint of the study is the frequency of specifically defined adverse events. Secondary endpoints are frequency of normoventilation, hypoventilation and hyperventilation, the time period between switch from controlled ventilation to assisted ventilation, achievement of stable assisted ventilation of the patient, proportion of time within the target zone for tidal volume, end-tidal partial pressure of carbon dioxide as individually set up for each patient by the user, frequency of alarms, frequency distribution of tidal volume, inspiratory pressure, inspiration time, expiration time, end-tidal partial pressure of carbon dioxide and the number of re-intubations.

ETHICS AND DISSEMINATION

AVAS will be the first clinical study investigating a novel automated system for the control of mechanical ventilation on an anaesthesia machine. The study was approved by the ethics committees of both participating study sites. In case that safety and efficacy are acceptable, a randomised controlled trial comparing the novel system with the usual practice may be warranted.

TRIAL REGISTRATION

DRKS DRKS00011025, registered 12 October 2016; clinicaltrials.gov ID. NCT02644005, registered 30 December 2015.

The Clinical Impact of Heated Humidified High-Flow Nasal Cannula on Pediatric Respiratory Distress

OBJECTIVES

To assess the impact on a single PICU of introducing high-flow nasal cannula as a management tool for respiratory distress.

DESIGN

Retrospective cohort study, including an interrupted time series analysis with a propensity score adjustment and a matched-pair analysis.

SETTING

A single university-affiliated children's hospital PICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Differences in clinical outcomes when comparing the pre-high-flow nasal cannula era (2004-2008) and the high-flow nasal cannula era (2010-2014), excluding 2009 as a washout period, and clinical impacts of high-flow nasal cannula as an exposure of interest. A total of 1,766 children met the inclusion criteria (pre-high-flow nasal cannula era: 699 patients; high-flow nasal cannula era: 1,067 patients). High-flow nasal cannula was used in 455 patients (42.6%) in the high-flow nasal cannula era. The interrupted time series analysis failed to show a statistically significant difference in PICU length of stay, but the duration of invasive ventilation was shortened by an average of 2.3 days in the high-flow nasal cannula era group (95% CI, 0.2-4.4; p = 0.030). The PICU intubation rate in the high-flow nasal cannula era was 0.72 times that of the pre-high-flow nasal cannula era (95% CI, 0.63-0.84; p < 0.001). A total of 373 pairs were formed for the matched-pair analysis. The odds for being intubated in the PICU for those patients using high-flow nasal cannula was 0.06 (95% CI, 0.02-0.16; p < 0.001) when compared with those who did not use high-flow nasal cannula. The PICU length of stay increased by 2.9 days in those patients in which high-flow nasal cannula was used (95% CI, 1.3-4.4; p < 0.001).

CONCLUSIONS

The introduction of high-flow nasal cannula as a therapy for respiratory distress in the PICU was associated with a significant decrease in the PICU intubation rate with no associated change in mortality.

Nursing Strategies for Effective Weaning of the Critically Ill Mechanically Ventilated Patient

The risks imposed by mechanical ventilation can be mitigated by nurses' use of strategies that promote early but appropriate reduction of ventilatory support and timely extubation. Weaning from mechanical ventilation is confounded by the multiple impacts of critical illness on the body's systems. Effective weaning strategies that combine several interventions that optimize weaning readiness and assess readiness to wean, and use a weaning protocol in association with spontaneous breathing trials, are likely to reduce the requirement for mechanical ventilatory support in a timely manner. Weaning strategies should be reviewed and updated regularly to ensure congruence with the best available evidence.

Discontinuation of ventilatory support: new solutions to old dilemmas

PURPOSE OF REVIEW

Weaning from mechanical ventilation implies two separate but closely related aspects of care, the discontinuation of mechanical ventilation and removal of artificial airway, which implies routine clinical dilemmas. Extubation delay and extubation failure are associated with poor clinical outcomes. We sought to summarize recent evidence on weaning.

RECENT FINDINGS

Tolerance to an unassisted breathing does not require routine use of weaning predictors and can be addressed using weaning protocols or by implementing automatic weaning methods. Spontaneous breathing trial can be performed on low levels of pressure support, continuous positive airway pressure, or T-piece. Echocardiographic tools may help to prevent the failure of extubation. Noninvasive ventilation can prevent respiratory failure after extubation, when used in hypercapnic patients. Recently, sedation protocols and early mobilization in ventilated critically ill patients may decrease weaning period and duration of mechanical ventilation, and prevent extubation failure and complications such as ICU-acquired weakness. New techniques have been performed to identify patients with high risk for extubation failure.

SUMMARY

There is an interesting body of clinical research in the discontinuation of mechanical ventilation. Recent randomized controlled studies provide high-level evidence for the best approaches to weaning, especially in patients who fail the first spontaneous breathing trial or targeted populations.

Smart Care™ versus respiratory physiotherapy-driven manual weaning for critically ill adult patients: a randomized controlled trial

Introduction

A recent meta-analysis showed that weaning with SmartCare™ (Dräger, Lübeck, Germany) significantly decreased weaning time in critically ill patients. However, its utility compared with respiratory physiotherapist–protocolized weaning is still a matter of debate. We hypothesized that weaning with SmartCare™ would be as effective as respiratory physiotherapy–driven weaning in critically ill patients.

Methods

Adult critically ill patients mechanically ventilated for more than 24 hours in the adult intensive care unit of the Albert Einstein Hospital, São Paulo, Brazil, were randomly assigned to be weaned either by progressive discontinuation of pressure support ventilation (PSV) with SmartCare™. Demographic data, respiratory function parameters, level of PSV, tidal volume (VT), positive end-expiratory pressure (PEEP), inspired oxygen fraction (FiO₂), peripheral oxygen saturation (SpO₂), end-tidal carbon dioxide concentration (EtCO₂) and airway occlusion pressure at 0.1 second (P_0.1) were recorded at the beginning of the weaning process and before extubation. Mechanical ventilation time, weaning duration and rate of extubation failure were compared.

Results

Seventy patients were enrolled 35 in each group. There was no difference between the two groups concerning age, sex or diagnosis at study entry. There was no difference in maximal inspiratory pressure, maximal expiratory pressure, forced vital capacity or rapid shallow breathing index at the beginning of the weaning trial. PEEP, VT, FiO₂, SpO₂, respiratory rate, EtCO₂ and P_0.1 were similar between the two groups, but PSV was not (median: 8 vs. 10 cmH₂O; p =0.007). When the patients were ready for extubation, PSV (8 vs. 5 cmH₂O; p =0.015) and PEEP (8 vs. 5 cmH₂O; p <0.001) were significantly higher in the respiratory physiotherapy–driven weaning group. Total duration of mechanical ventilation (3.5 [2.0–7.3] days vs. 4.1 [2.7-7.1] days; p =0.467) and extubation failure (2 vs. 2; p =1.00) were similar between the two groups. Weaning duration was shorter in the respiratory physiotherapy–driven weaning group (60 [50–80] minutes vs. 110 [80–130] minutes; p <0.001).

Conclusion

A respiratory physiotherapy–driven weaning protocol can decrease weaning time compared with an automatic system, as it takes into account individual weaning difficulties.

Trial registration

Clinicaltrials.gov Identifier: NCT02122016. Date of Registration: 27 August 2013.

Classification of patients undergoing weaning from mechanical ventilation using the coherence between heart rate variability and respiratory flow signal

Weaning from mechanical ventilation is still one of the most challenging problems in intensive care. Unnecessary delays in discontinuation and weaning trials that are undertaken too early are both undesirable. This study investigated the contribution of spectral signals of heart rate variability (HRV) and respiratory flow, and their coherence to classifying patients on weaning process from mechanical ventilation. A total of 121 candidates for weaning, undergoing spontaneous breathing tests, were analyzed: 73 were successfully weaned (GSucc), 33 failed to maintain spontaneous breathing so were reconnected (GFail), and 15 were extubated after the test but reintubated within 48 h (GRein). The power spectral density and magnitude squared coherence (MSC) of HRV and respiratory flow signals were estimated. Dimensionality reduction was performed using principal component analysis (PCA) and sequential floating feature selection. The patients were classified using a fuzzy K-nearest neighbour method. PCA of the MSC gave the best classification with the highest accuracy of 92% classifying GSucc versus GFail patients, and 86% classifying GSucc versus GRein patients. PCA of the respiratory flow signal gave the best classification between GFail and GRein patients (79% accuracy). These classifiers showed a good balance between sensitivity and specificity. Besides, the spectral coherence between HRV and the respiratory flow signal, in patients on weaning trial process, can contribute to the extubation decision.

Automated versus non-automated weaning for reducing the duration of mechanical ventilation for critically ill adults and children: a cochrane systematic review and meta-analysis

Introduction

Automated weaning systems may improve adaptation of mechanical support for a patient’s ventilatory needs and facilitate systematic and early recognition of their ability to breathe spontaneously and the potential for discontinuation of ventilation. Our objective was to compare mechanical ventilator weaning duration for critically ill adults and children when managed with automated systems versus non-automated strategies. Secondary objectives were to determine differences in duration of ventilation, intensive care unit (ICU) and hospital length of stay (LOS), mortality, and adverse events.

Methods

Electronic databases were searched to 30 September 2013 without language restrictions. We also searched conference proceedings; trial registration websites; and article reference lists. Two authors independently extracted data and assessed risk of bias. We combined data using random-effects modelling.

Results

We identified 21 eligible trials totalling 1,676 participants. Pooled data from 16 trials indicated that automated systems reduced the geometric mean weaning duration by 30% (95% confidence interval (CI) 13% to 45%), with substantial heterogeneity (I² = 87%, P <0.00001). Reduced weaning duration was found with mixed or medical ICU populations (42%, 95% CI 10% to 63%) and Smartcare/PS™ (28%, 95% CI 7% to 49%) but not with surgical populations or using other systems. Automated systems reduced ventilation duration with no heterogeneity (10%, 95% CI 3% to 16%) and ICU LOS (8%, 95% CI 0% to 15%). There was no strong evidence of effect on mortality, hospital LOS, reintubation, self-extubation and non-invasive ventilation following extubation. Automated systems reduced prolonged mechanical ventilation and tracheostomy. Overall quality of evidence was high.

Conclusions

Automated systems may reduce weaning and ventilation duration and ICU stay. Due to substantial trial heterogeneity an adequately powered, high quality, multi-centre randomized controlled trial is needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0755-6) contains supplementary material, which is available to authorized users.

Power index of the inspiratory flow signal as a predictor of weaning in intensive care units

Disconnection from mechanical ventilation, called the weaning process, is an additional difficulty in the management of patients in intensive care units (ICU). Unnecessary delays in the discontinuation process and a weaning trial that is undertaken too early are undesirable. In this study, we propose an extubation index based on the power of the respiratory flow signal (Pi). A total of 132 patients on weaning trials were studied: 94 patients with successful trials (group S) and 38 patients who failed to maintain spontaneous breathing and were reconnected (group F). The respiratory flow signals were processed considering the following three stages: a) zero crossing detection of the inspiratory phase, b) inflection point detection of the flow curve during the inspiratory phase, and c) calculation of the signal power on the time instant indicated by the inflection point. The zero crossing detection was performed using an algorithm based on thresholds. The inflection points were marked considering the zero crossing of the second derivative. Finally, the inspiratory power was calculated from the energy contained over the finite time interval (between the instant of zero crossing and the inflection point). The performance of this parameter was evaluated using the following classifiers: logistic regression, linear discriminant analysis, the classification and regression tree, Naive Bayes, and the support vector machine. The best results were obtained using the Bayesian classifier, which had an accuracy, sensitivity and specificity of 87%, 90% and 81% respectively.

Default options in the ICU: widely used but insufficiently understood

PURPOSE OF REVIEW

Default options dramatically influence the behavior of decision makers and may serve as effective decision support tools in the ICU. Their use in medicine has increased in an effort to improve efficiency, reduce errors, and harness the potential of healthcare technology.

RECENT FINDINGS

Defaults often fall short of their predicted influence when employed in critical care settings as quality improvement interventions. Investigations reporting the use of defaults are often limited by variations in the relative effect across sites. Preimplementation experiments and long-term monitoring studies are lacking.

SUMMARY

Defaults in the ICU may help or harm patients and clinical efficiency depending on their format and use. When constructing and encountering defaults, providers should be aware of their powerful and complex influences on decision making. Additional evaluations of the appropriate creation of healthcare defaults and their resulting intended and unintended consequences are needed.

Automated weaning and SBT systems versus non-automated weaning strategies for weaning time in invasively ventilated critically ill adults

BACKGROUND

Automated systems use closed-loop control to enable ventilators to perform basic and advanced functions while supporting respiration. SmartCare™ is a unique automated weaning system that measures selected respiratory variables, adapts ventilator output to individual patient needs by operationalizing predetermined algorithms and automatically conducts spontaneous breathing trials (SBTs) when predetermined thresholds are met.

OBJECTIVES

The primary objective of this review was to compare weaning time (time from randomization to extubation as defined by study authors) between invasively ventilated critically ill adults weaned by automated weaning and SBT systems versus non-automated weaning strategies.As secondary objectives, we ascertained differences between effects of alternative weaning strategies on clinical outcomes (time to successful extubation, time to first SBT and first successful SBT, mortality, ventilator-associated pneumonia, total duration of ventilation, lengths of intensive care unit (ICU) and hospital stay, use of non-invasive ventilation (NIV), adverse events and clinician acceptance).The third objective of our review was to use subgroup analyses to explore variations in weaning time, length of ICU stay, mortality, ventilator-associated pneumonia, use of NIV and reintubation according to (1) the type of clinician primarily involved in implementing the automated weaning and SBT strategy, (2) the ICU (as a reflection of the population involved) and (3) the non-automated (control) weaning strategy utilized.We conducted a sensitivity analysis to evaluate variations in weaning time based on (4) the methodological quality (low or unclear versus high risk of bias) of the included studies.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 5; MEDLINE (1966 to 31 May 2013); EMBASE (1988 to 31 May 2013); the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to 31 May 2013), Evidence-Based Medicine Reviews and Ovid HealthSTAR (1999 to 31 May 2013), as well as conference proceedings and trial registration websites; we also contacted study authors and content experts to identify potentially eligible trials.

SELECTION CRITERIA

Randomized and quasi-randomized trials comparing automated weaning and SBT systems versus non-automated weaning strategies in intubated adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and abstracted data according to prespecified criteria. Sensitivity and subgroup analyses were planned to assess the impact on selected outcomes of the following: (1) the type of clinician primarily involved in implementing automated weaning and SBT systems, (2) the ICU (as a reflection of the population involved) and (3) the non-automated (control) weaning strategy utilized.

MAIN RESULTS

We pooled summary estimates from 10 trials evaluating SmartCare™ involving 654 participants. Overall, eight trials were judged to be at low or unclear risk of bias, and two trials were judged to be at high risk of bias. Compared with non-automated strategies, SmartCare™ decreased weaning time (mean difference (MD) -2.68 days, 95% confidence interval (CI) -3.99 to -1.37; P value < 0.0001, seven trials, 495 participants, moderate-quality evidence), time to successful extubation (MD -0.99 days, 95% CI -1.89 to -0.09; P value 0.03, seven trials, 516 participants, low-quality evidence), length of ICU stay (MD -5.70 days, 95% CI -10.54 to -0.85; P value 0.02, six trials, 499 participants, moderate-quality evidence) and proportions of participants receiving ventilation for longer than seven and 21 days (risk ratio (RR) 0.44, 95% CI 0.23 to 0.85; P value 0.01 and RR 0.39, 95% CI 0.18 to 0.86; P value 0.02). SmartCare™ reduced the total duration of ventilation (MD -1.68 days, 95% CI -3.33 to -0.03; P value 0.05, seven trials, 521 participants, low-quality evidence) and the number of participants receiving ventilation for longer than 14 days (RR 0.61, 95% CI 0.37 to 1.00; P value 0.05); however the estimated effects were imprecise. SmartCare™ had no effect on time to first successful SBT, mortality or adverse events, specifically reintubation. Subgroup analysis suggested that trials with protocolized (versus non-protocolized) control weaning strategies reported significantly shorter ICU stays. Sensitivity analysis excluded two trials with high risk of bias and supported a trend toward significant reductions in weaning time favouring SmartCare™.

AUTHORS' CONCLUSIONS

Compared with non-automated weaning strategies, weaning with SmartCare™ significantly decreased weaning time, time to successful extubation, ICU stay and proportions of patients receiving ventilation for longer than seven days and 21 days. It also showed a favourable trend toward fewer patients receiving ventilation for longer than 14 days; however the estimated effect was imprecise. Summary estimates from our review suggest that these benefits may be achieved without increasing the risk of adverse events, especially reintubation; however, the quality of the evidence ranged from low to moderate, and evidence was derived from 10 small randomized controlled trials.

Automated versus non-automated weaning for reducing the duration of mechanical ventilation for critically ill adults and children

BACKGROUND

Automated closed loop systems may improve adaptation of mechanical support for a patient's ventilatory needs and facilitate systematic and early recognition of their ability to breathe spontaneously and the potential for discontinuation of ventilation. This review was originally published in 2013 with an update published in 2014.

OBJECTIVES

The primary objective for this review was to compare the total duration of weaning from mechanical ventilation, defined as the time from study randomization to successful extubation (as defined by study authors), for critically ill ventilated patients managed with an automated weaning system versus no automated weaning system (usual care).Secondary objectives for this review were to determine differences in the duration of ventilation, intensive care unit (ICU) and hospital lengths of stay (LOS), mortality, and adverse events related to early or delayed extubation with the use of automated weaning systems compared to weaning in the absence of an automated weaning system.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 8); MEDLINE (OvidSP) (1948 to September 2013); EMBASE (OvidSP) (1980 to September 2013); CINAHL (EBSCOhost) (1982 to September 2013); and the Latin American and Caribbean Health Sciences Literature (LILACS). Relevant published reviews were sought using the Database of Abstracts of Reviews of Effects (DARE) and the Health Technology Assessment Database (HTA Database). We also searched the Web of Science Proceedings; conference proceedings; trial registration websites; and reference lists of relevant articles. The original search was run in August 2011, with database auto-alerts up to August 2012.

SELECTION CRITERIA

We included randomized controlled trials comparing automated closed loop ventilator applications to non-automated weaning strategies including non-protocolized usual care and protocolized weaning in patients over four weeks of age receiving invasive mechanical ventilation in an ICU.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted study data and assessed risk of bias. We combined data in forest plots using random-effects modelling. Subgroup and sensitivity analyses were conducted according to a priori criteria.

MAIN RESULTS

We included 21 trials (19 adult, two paediatric) totaling 1676 participants (1628 adults, 48 children) in this updated review. Pooled data from 16 eligible trials reporting weaning duration indicated that automated closed loop systems reduced the geometric mean duration of weaning by 30% (95% confidence interval (CI) 13% to 45%), however heterogeneity was substantial (I(2) = 87%, P < 0.00001). Reduced weaning duration was found with mixed or medical ICU populations (42%, 95% CI 10% to 63%) and Smartcare/PS™ (28%, 95% CI 7% to 49%) but not in surgical populations or using other systems. Automated closed loop systems reduced the duration of ventilation (10%, 95% CI 3% to 16%) and ICU LOS (8%, 95% CI 0% to 15%). There was no strong evidence of an effect on mortality rates, hospital LOS, reintubation rates, self-extubation and use of non-invasive ventilation following extubation. Prolonged mechanical ventilation > 21 days and tracheostomy were reduced in favour of automated systems (relative risk (RR) 0.51, 95% CI 0.27 to 0.95 and RR 0.67, 95% CI 0.50 to 0.90 respectively). Overall the quality of the evidence was high with the majority of trials rated as low risk.

AUTHORS' CONCLUSIONS

Automated closed loop systems may result in reduced duration of weaning, ventilation and ICU stay. Reductions are more likely to occur in mixed or medical ICU populations. Due to the lack of, or limited, evidence on automated systems other than Smartcare/PS™ and Adaptive Support Ventilation no conclusions can be drawn regarding their influence on these outcomes. Due to substantial heterogeneity in trials there is a need for an adequately powered, high quality, multi-centre randomized controlled trial in adults that excludes 'simple to wean' patients. There is a pressing need for further technological development and research in the paediatric population.

New modes of assisted mechanical ventilation

Recent major advances in mechanical ventilation have resulted in new exciting modes of assisted ventilation. Compared to traditional ventilation modes such as assisted-controlled ventilation or pressure support ventilation, these new modes offer a number of physiological advantages derived from the improved patient control over the ventilator. By implementing advanced closed-loop control systems and using information on lung mechanics, respiratory muscle function and respiratory drive, these modes are specifically designed to improve patient-ventilator synchrony and reduce the work of breathing. Depending on their specific operational characteristics, these modes can assist spontaneous breathing efforts synchronically in time and magnitude, adapt to changing patient demands, implement automated weaning protocols, and introduce a more physiological variability in the breathing pattern. Clinicians have now the possibility to individualize and optimize ventilatory assistance during the complex transition from fully controlled to spontaneous assisted ventilation. The growing evidence of the physiological and clinical benefits of these new modes is favoring their progressive introduction into clinical practice. Future clinical trials should improve our understanding of these modes and help determine whether the claimed benefits result in better outcomes.

Managing the apparent and hidden difficulties of weaning from mechanical ventilation

BACKGROUND

In anaesthetized patients scheduled for surgery, tracheal intubation is performed with the expectation of subsequent smooth extubation. In critically ill patients, separation from the ventilator is often gradual and the time chosen for extubation may be either delayed or premature. Thus, weaning is challenging, represents a large part of the ventilation period and concerns all mechanically ventilated patients surviving their stay.

DEFINITIONS AND MANAGEMENT

Weaning may be stratified in three groups according to its difficulty and duration. In simple weaning the main issue is to detect the soonest time to start separation from the ventilator; this is frequently impeded by poor sedation management and excessive ventilator assistance. A two-step diagnostic approach is the most efficacious: screening for ascertained readiness to wean is confirmed by a diagnostic test simulating the post-extubation period, best performed by unassisted breathing (no PEEP). In case of test failure (difficult weaning), a structured and thorough diagnostic work-up regarding potentially reversible pathologies is required with a focus on cardiovascular dysfunction or fluid overload at the time of separation from the ventilator, respiratory or global muscle weakness and underlying infection. Prolonged weaning is exceptionally time- and resource-consuming, needs to properly appraise psychological problems, sleep and nutrition, and is probably best performed in specialized units.

CONCLUSIONS

Adequately managing simple and difficult weaning requires one to think about ICU policies in terms of sedation, fluid balance and having a systematic screening strategy; it also needs an individualized approach to understand and treat the failing patients. Prolonged weaning requires a holistic approach.