Automatic “Respirator/Weaning” with Adaptive Support Ventilation: The Effect on Duration of Endotracheal Intubation and Patient Management

Recommendations for fast-track extubation in adult cardiac surgery patients: a consensus statement

INTRODUCTION

Enhanced recovery after cardiac surgery in selected low-risk patients, has the potential to improve outcomes and reduce the burden of healthcare costs. Anesthesia-related challenges play a major role in the successful implementation of Enhanced Recovery After Surgery (ERAS) protocols, with particular emphasis placed on fast-track extubation. Acknowledging the importance of this practice, the Italian Association of Cardiac Anesthesiologists and Intensive Care (ITACTAIC) has advocated for an initiative to establish a consensus offering practical recommendations for fast-track extubation after adult cardiac surgery.

EVIDENCE ACQUISITION

After conducting a systematic review, all randomised control trials (RCTs) published between 2013 and 2023 were meticulously selected and analysed during a consensus meeting that involved statement voting.

EVIDENCE SYNTHESIS

Out of the 2268 publications identified using the search string, 60 RCTs were selected and classified into six groups, each evaluating specific interventions associated with extubation within 6 hours post-surgery. The authors examined 20 RCTs pertaining to loco-regional anesthesia, 19 analysing elements of general anesthesia, 12 focused on surgery-related aspects and techniques, three examining ventilation, two exploring anesthesia depth monitoring, and four addressing miscellaneous aspects. The expert panel approved 16 statements with 15 achieving high agreement and one obtaining moderate agreement. Finally a total of eight interventions were considered associated with fast-track extubation: parasternal block, erector spinae plane block, alpha agonist in the operating room (OR), opioids in the OR, dexmedetomidine in the intensive care unit (ICU), minimal invasive surgical access, anesthesia depth monitoring, adaptative support ventilation.

CONCLUSIONS

In the first consensus document ever published by a scientific society addressing practical recommendations for fast-track extubation post-cardiac surgery, the authors identified sixteen interventions commonly associated with fast-track extubation in selected adult cardiac surgery patients.

Effectiveness of Adaptive Support Ventilation in Facilitating Weaning from Mechanical Ventilation in Postoperative Patients

OBJECTIVE

This meta-analysis aims to evaluate the effectiveness of adaptive support ventilation (ASV) in facilitating postoperative weaning from mechanical ventilation in cardiac surgery patients.

DESIGN

A systematic review and meta-analysis to assess ASV in weaning postoperative cardiac surgery patients. Outcomes included early extubation, reintubation rates, time to extubation, and lengths of intensive care units and hospital stays.

SETTING

We searched electronic databases from inception to March 2023 and included randomized controlled trials that compared ASV with conventional ventilation methods in this population.

PARTICIPANTS

Postoperative cardiac surgery patients.

MEASUREMENTS AND MAIN RESULTS

A random effects model was used for meta-analysis, and trial sequential analysis (TSA) was conducted to assess result robustness. The meta-analysis included 11 randomized controlled trials with a total of 1027 randomized patients. ASV was associated with a shorter time to extubation compared to conventional ventilation (random effects, mean difference -68.30 hours; 95% confidence interval, -115.50 to -21.09) with TSA providing a conclusive finding. While ASV indicated improved early extubation rates, no significant differences were found in reintubation rates or lengths of intensive care unit and hospital stays, with these TSA results being inclusive.

CONCLUSIONS

ASV appears to facilitate a shorter time to extubation in postoperative cardiac surgery patients compared to conventional ventilation, suggesting benefits in accelerating the weaning process and reducing mechanical ventilation duration.

Managing the Chronically Ventilated Critically Ill Population

Advances in intensive care over the past few decades have significantly improved the chances of survival for patients with acute critical illness. However, this progress has also led to a growing population of patients who are dependent on intensive care therapies, including prolonged mechanical ventilation (PMV), after the initial acute period of critical illness. These patients are referred to as the "chronically critically ill" (CCI). CCI is a syndrome characterized by prolonged mechanical ventilation, myoneuropathies, neuroendocrine disorders, nutritional deficiencies, cognitive and psychiatric issues, and increased susceptibility to infections. It is associated with high morbidity and mortality as well as a significant increase in healthcare costs. In this article, we will review disease burden, outcomes, psychiatric effects, nutritional and ventilator weaning strategies as well as the role of palliative care for CCI with a specific focus on those requiring PMV.

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.

Health Technology Assessment of Intensive Care Ventilators for Pediatric Patients

This paper is aimed at addressing all the critical aspects linked to the implementation of intensive care ventilators in a pediatric setting, highlighting the most relevant technical features and describing the methodology to conduct health technology assessment (HTA) for supporting the decision-making process. Four ventilator models were included in the assessment process. A decision-making support tool (DoHTA method) was applied. Twenty-eight Key Performance Indicators (KPIs) were identified, defining the safety, clinical effectiveness, organizational, technical, and economic aspects. The Performance scores of each ventilator have been measured with respect to KPIs integrated with the total cost of ownership analysis, leading to a final rank of the four possible technological solutions. The final technologies' performance scores reflected a deliver valued, contextualized, and shared outputs, detecting the most performant technological solution for the specific hospital context. HTA results had informed and supported the pediatric hospital decision-making process. This study, critically identifying the pros and cons of innovative features of ventilators and the evaluation criteria and aspects to be taken into account during HTA, can be considered as a valuable proof of evidence as well as a reliable and transferable method for conducting decision-making processes in a hospital context.

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).

Relationship between dynamic expiratory time constant tau(edyn) and parameters of breathing cycle in pressure support ventilation mode

Study of the relationship between ventilation parameters: monitored expiratory time constant - tau(edyn) and breathing - trigger frequency (f(trig)) and time of breathing cycle (T(cy)) are main goals of this article. Parameters were analyzed during last 4+/-2 h before weaning from ventilation in 66 patients ventilated in pressure support mode (PSV). We have found out, that there exist mathematical relationships, observed during adequate gas exchange, yet not described. Monitored parameters are represented by tau(edyn), f(trig) and T(cy). The analysis showed close negative correlation between T(cy) and f(trig) (R(2)=0.903). This implies that each increasing of tau(edyn) causes decreasing of f(trig) and vice versa. The calculation of regression equation between tau(edyn) and T(cy) outlined that T(cy) = 5.2625 * tau(edyn) + 0.1242 (R(2)=0.85). Regulation of respiratory cycles by the respiratory center in the brain is probably based on evaluation of tau(edyn) as the tau(edyn) probably represents a regulatory element and T(cy) regulated element. It can be assumed, that respiratory center can optimize the work of breathing in order to minimize energy in system patient + ventilator. The unique relationship, described above could be useful in clinical practice for development of new ventilation modes.

Automation of Mechanical Ventilation

Closed loop control of mechanical ventilation is routine and operates behind the ventilator interface. Reducing caregiver interactions is neither an advantage for the patient or the staff. Automated systems causing lack of situational awareness of the intensive care unit are a concern. Along with autonomous systems must come monitoring and displays that display patients' current condition and response to therapy. Alert notifications for sudden escalation of therapy are required to ensure patient safety. Automated ventilation is useful in remote settings in the absence of experts. Whether automated ventilation will be accepted in large academic medical centers remains to be seen.

Advanced Modes of Mechanical Ventilation: Introduction for the Critical Care Pharmacist

Mechanical ventilation continues to be an evolving modality in the critical care environment. Technological advances in microprocessor-controlled ventilation integrated with the complexity of new ventilator modes has provided the multidisciplinary team opportunities to further improve the care of the critically ill ventilator patients. As members of the critical care multidisciplinary team, pharmacists require a basic understanding of both conventional and advanced modes of mechanical ventilation in order to assist in optimizing medication use and ultimately patient health-care outcomes. Pharmacists have a key responsibility to practice vigilance to maintain safe drug therapy use by preventing drug-drug or drug-disease interactions and optimal dose selection based upon pharmacokinetics and pharmacodynamics principles. Pharmacists also assist in the development of drug utilization guidelines and pharmacological ventilator-weaning protocols based upon evidence-based practice. The result of these responsibilities must include the continued longitudinal assessment and reporting of quality measures to assess ventilator weaning, time to liberation of mechanical ventilation, and length of care in intensive care unit. The purpose of this article is to provide the clinical pharmacist a guide to a basic understanding of advanced modes of mechanical ventilation in adults and to apply the knowledge gained to assist in the care of the critical care patients.

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.

Adaptive Support Ventilation Reduces the Incidence of Atelectasis in Patients Undergoing Coronary Artery Bypass Grafting: A Randomized Clinical Trial

Background

Pulmonary complications are common following cardiac surgery and can lead to increased morbidity, mortality, and healthcare costs. Atelectasis is the most common respiratory complication following cardiac surgery. One of the most important methods for reducing pulmonary complications is supportive care with protective ventilation strategies. In this study, we aimed to assess the effect of adaptive support ventilation (ASV) on atelectasis in patients undergoing cardiac surgery.

Methods

In this single-blind randomized clinical trial, 115 patients, undergoing coronary artery bypass grafting, were randomly allocated into 2 groups: 57 patients in the intervention and 58 patients in the control group. Patients in the intervention group were weaned with ASV, while patients in the control group were managed using synchronized intermittent mandatory ventilation (SIMV) and pressure support. The incidence of atelectasis, duration of mechanical ventilation, manual ventilator setting, arterial blood gas measurements, and length of hospital stay were compared between the groups.

Results

The incidence of atelectasis, number of changes in the manual ventilator setting, number of alarms, and length of hospital stay reduced in the intervention group. However, duration of mechanical ventilation and number of ABG measurements were not significantly different between the groups.

Conclusions

The ASV mode could reduce the incidence of atelectasis and length of hospital stay. However, it did not reduce the duration of mechanical ventilation. It seems that ASV is not a superior mode for faster extubation.

Comparing the Effect of Adaptive Support Ventilation (ASV) and Synchronized Intermittent Mandatory Ventilation (SIMV) on Respiratory Parameters in Neurosurgical ICU Patients

BACKGROUND

Various modes of mechanical ventilation have different effects on respiratory variables. Lack of patients' neuro-ventilatory coordination and increasing the work of breathing are major disadvantages in mechanically ventilated patients.

OBJECTIVES

This study is conducted to compare the respiratory parameters differences in Adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation (SIMV) modes in neurosurgical ICU patients.

METHODS

In a crossover study, patients under mechanical ventilation in neurosurgical ICU were enrolled. The patients alternatively experienced two types of ventilations for 30 minutes (adaptive support ventilation and synchronized intermittent mandatory ventilation). The respiratory parameters (tidal volume, respiratory rate, airway pressure, lung compliance, end-tidal carbon dioxide, peripheral oxygenation and respiratory dead space), hemodynamic variables, every 10 minutes and arterial blood gas analysis at the end of each 30 minutes were recorded. Results were compared and analyzed with SPSS v.19.

RESULTS

Sixty patients were involved in this study. In ASV mode, values including peak airway pressure (P-peak), end-tidal carbon dioxide (EtCO2), tidal volume and respiratory dead space were significantly lower than SIMV mode. Although the mean value for dynamic compliance had no significant difference in the two types of ventilation, it was better in ASV mode.

CONCLUSIONS

ASV mode compared with SIMV mode can lead to improve lung compliance and respiratory dead space.

Comparing the effects of adaptive support ventilation and synchronized intermittent mandatory ventilation on intubation duration and hospital stay after coronary artery bypass graft surgery

Background:

Different modes of mechanical ventilation are used for respiratory support after coronary artery bypass graft (CABG). This study aimed to compare the effect(s) of using adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation (SIMV) on the length of mechanical ventilation (intubation duration) and hospital stay after coronary artery bypass graft surgery.

Materials and Methods:

In a randomized control trial, 64 patients were ventilated with ASV as the experiment group or with SIMV as the control group after CABG surgery in Chamran Hospital of Isfahan University of Medical Sciences. The time of tracheal intubation and the length of hospital stay were compared between the two groups. Data were analyzed and described using statistical analysis (independent t-test).

Results:

The mean time of intubation duration was significantly lower in ASV group compared with SIMV group. (4.83 h vs 6.71 h, P < 0.001). The lengths of hospital stay in the ASV and the SIMV groups were 140.6 h and 145.1 h, respectively. This difference was significant between the two groups (P = 0.006).

Conclusions:

According to the results of this study, using ASV mode for mechanical ventilation after CABG led to a decrease in intubation duration and also hospital stay in comparison with the SIMV group. It is recommended to use ASV mode on ventilators for respiratory support of patients undergoing coronary artery bypass graft surgery.

Advanced pressure control modes of ventilation in cardiac surgery: Scanty evidence or unexplored terrain?

Lung atelectasis resulting after cardiopulmonary bypass (CPB) can result in increased intrapulmonary shunting and consequent hypoxemia. Advanced pressure control modes of ventilation might have at least a theoretical advantage over conventional modes by assuring a minimum target tidal volume delivery at reasonable pressures, thus having potential advantages while ventilating patients with pulmonary atelectasis postcardiac surgery. However, the utility of these modes in the post-CPB setting have not been widely investigated, and their role in cardiac intensive care, therefore, remains quite limited.

A randomized controlled trial of 2 protocols for weaning cardiac surgical patients receiving adaptive support ventilation

PURPOSE

This study aims to compare the effectiveness of weaning with adaptive support ventilation (ASV) incorporating progressively reduced or constant target minute ventilation in the protocol in postoperative care after cardiac surgery.

MATERIAL AND METHODS

A randomized controlled unblinded study of 52 patients after elective coronary artery bypass surgery was carried out to determine whether a protocol incorporating a decremental target minute ventilation (DTMV) results in more rapid weaning of patients ventilated in ASV mode compared to a protocol incorporating a constant target minute ventilation.

RESULTS

Median duration of mechanical ventilation (145 vs 309 minutes; P = .001) and intubation (225 vs 423 minutes; P = .005) were significantly shorter in the DTMV group. There was no difference in adverse effects (42% vs 46%) or mortality (0% vs 0%) between the 2 groups.

CONCLUSIONS

Use of a DTMV protocol for postoperative ventilation of cardiac surgical patients in ASV mode results in a shorter duration of ventilation and intubation without evidence of increased risk of adverse effects.

Effects of adaptive support ventilation and synchronized intermittent mandatory ventilation on peripheral circulation and blood gas markers of COPD patients with respiratory failure

The objective of the study was to investigate the effects of adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation (SIMV) on peripheral circulation of chronic obstructive pulmonary disease (COPD) patients with respiratory failure. 86 COPD patients with respiratory failure were recruited in this study. Self-control method was used to compare the effect of ASV and SIMV on the parameters of ventilation machine, heart rate, blood pressure, central venous pressure (CVP), and blood gas markers. When the patients in ASV and SIMV groups were compared, respiratory rate, tidal volume, and peak airway pressure (PIP) showed significant difference. When minute ventilation (MV) was compared, no significant difference was shown. When peripheral circulation parameters were compared, peripheral circulation heart rate, SBP, DBP, and CVP showed significant difference. Compared with SIMV group, PaO2, pH, and SaO2 values were remarkably increased (P < 0.01) while no significant difference was found for partial pressure of carbon dioxide (pCO2) when two groups were compared. In conclusion, when mechanical ventilation was used in COPD patients with respiratory failure, ASV can significantly improve clinical outcomes.

A randomized controlled trial comparing the ventilation duration between adaptive support ventilation and pressure assist/control ventilation in medical patients in the ICU

BACKGROUND

Adaptive support ventilation (ASV) is a closed loop mode of mechanical ventilation (MV) that provides a target minute ventilation by automatically adapting inspiratory pressure and respiratory rate with the minimum work of breathing on the part of the patient. The aim of this study was to determine the effect of ASV on total MV duration when compared with pressure assist/control ventilation.

METHODS

Adult medical patients intubated and mechanically ventilated for > 24 h in a medical ICU were randomized to either ASV or pressure assist/control ventilation. Sedation and medical treatment were standardized for each group. Primary outcome was the total MV duration. Secondary outcomes were the weaning duration, number of manual settings of the ventilator, and weaning success rates.

RESULTS

Two hundred twenty-nine patients were included. Median MV duration until weaning, weaning duration, and total MV duration were significantly shorter in the ASV group (67 [43-94] h vs 92 [61-165] h, P = .003; 2 [2-2] h vs 2 [2-80] h, P = .001; and 4 [2-6] days vs 4 [3-9] days, P = .016, respectively). Patients in the ASV group required fewer total number of manual settings on the ventilator to reach the desired pH and Paco2 levels (2 [1-2] vs 3 [2-5], P < .001). The number of patients extubated successfully on the first attempt was significantly higher in the ASV group (P = .001). Weaning success and mortality at day 28 were comparable between the two groups.

CONCLUSIONS

In medical patients in the ICU, ASV may shorten the duration of weaning and total MV duration with a fewer number of manual ventilator settings.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01472302; URL: www.clinicaltrials.gov.

Discontinuous versus Continuous Weaning in Stroke Patients

Background: An increasing number of stroke patients have to be supported by mechanical ventilation in intensive care units (ICU), with a relevant proportion of them requiring gradual withdrawal from a respirator. To date, weaning studies have focused merely on mixed patient groups, COPD patients or patients after cardiac surgery. Therefore, the best weaning strategy for stroke patients remains to be determined. Methods: Here, we designed a prospective randomized controlled study comparing adaptive support ventilation (ASV), a continuous weaning strategy, with biphasic positive airway pressure (BIPAP) in combination with spontaneous breathing trials, a discontinuous technique, in the treatment of stroke patients. The primary endpoint was the duration of the weaning process. Results: Only the 40 (out of 54) patients failing in an initial spontaneous breathing trial (T-piece test) were included into the study; the failure proportion is considerably larger compared to previous studies. Eligible patients were pseudo-randomly assigned to one of the two weaning groups. Both groups did not differ regarding age, gender, and severity of stroke. The results showed that the median weaning duration was 10.7 days (±SD 7.0) in the discontinuous weaning group, and 8 days (±SD 4.5) in the continuous weaning group (p < 0.05). Conclusions: To the best of our knowledge, this is the first clinical study to show that continuous weaning is significantly more effective compared to discontinuous weaning in mechanically ventilated stroke patients. We suppose that the reason for the superiority of continuous weaning using ASV as well as the bad performance of our patients in the 2 h T-piece test is caused by the patients' compliance. Compared to patients on surgical and medical ICUs, neurological patients more often suffer from reduced vigilance, lack of adverse-effects reflexes, dysphagia, and cerebral dysfunction. Therefore, stroke patients may profit from a more gradual withdrawal of weaning.

A Randomized Controlled Trial of Adaptive Support Ventilation Mode to Wean Patients after Fast-track Cardiac Valvular Surgery

Background:

Adaptive support ventilation can speed weaning after coronary artery surgery compared with protocolized weaning using other modes. There are no data to support this mode of weaning after cardiac valvular surgery. Furthermore, control group weaning times have been long, suggesting that the results may reflect control group protocols that delay weaning rather than a real advantage of adaptive support ventilation.

Methods:

Randomized (computer-generated sequence and sealed opaque envelopes), parallel-arm, unblinded trial of adaptive support ventilation versus physician-directed weaning after adult fast-track cardiac valvular surgery. The primary outcome was duration of mechanical ventilation. Patients aged 18 to 80 yr without significant renal, liver, or lung disease or severe impairment of left ventricular function undergoing uncomplicated elective valve surgery were eligible. Care was standardized, except postoperative ventilation. In the adaptive support ventilation group, target minute ventilation and inspired oxygen concentration were adjusted according to blood gases. A spontaneous breathing trial was carried out when the total inspiratory pressure of 15 cm H2O or less with positive end-expiratory pressure of 5 cm H2O. In the control group, the duty physician made all ventilatory decisions.

Results:

Median duration of ventilation was statistically significantly shorter (P = 0.013) in the adaptive support ventilation group (205 [141 to 295] min, n = 30) than that in controls (342 [214 to 491] min, n = 31). Manual ventilator changes and alarms were less common in the adaptive support ventilation group, and arterial blood gas estimations were more common.

Conclusion:

Adaptive support ventilation reduces ventilation time by more than 2 h in patients who have undergone fast-track cardiac valvular surgery while reducing the number of manual ventilator changes and alarms.

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.

Adaptive support ventilation versus synchronized intermittent mandatory ventilation with pressure support in weaning patients after orthotopic liver transplantation

BACKGROUND

The extubation phase is an extremely critical moment in patients who have undergone orthotopic liver transplantation, who do not always have the advantage of long-lasting positive-pressure ventilation and positive expiratory end pressure; these factors can lead to splanchnic venous congestion, and this is why a rapid extubation can represent a great benefit for the graft.

METHODS

The aim of this study was to compare the adaptive support ventilation (ASV) mode with the standard mode of weaning in our intensive care unit, synchronized intermittent mandatory ventilation with pressure support (P-SIMV), in patients who received orthotopic liver transplantation. ASV is a positive-pressure mode, in which pressure level and respiratory rate are automatically adjusted according to measured lung dynamics at each breath. Eligible patients were assigned to either ASV or P-SIMV group. The weaning protocol was based on the individual respiratory activity and structured in 4 different phases.

RESULTS

The average length of intubation was significantly shorter in the ASV group than in the P-SIMV group (90±13 vs 153±22 minutes, P=.05). The total modifications to the ventilator settings were significantly larger in the P-SIMV group (1.5±1 vs 6±2; P=.003).

CONCLUSIONS

Our results suggest that although both procedures are safe and easy to apply, ASV is superior in terms of weaning times, and it simplifies respiratory management. The better patient-machine interaction in ASV has been highlighted by other authors for different clusters of patients.

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.

A knowledge- and model-based system for automated weaning from mechanical ventilation: technical description and first clinical application

To describe the principles and the first clinical application of a novel prototype automated weaning system called Evita Weaning System (EWS). EWS allows an automated control of all ventilator settings in pressure controlled and pressure support mode with the aim of decreasing the respiratory load of mechanical ventilation. Respiratory load takes inspired fraction of oxygen, positive end-expiratory pressure, pressure amplitude and spontaneous breathing activity into account. Spontaneous breathing activity is assessed by the number of controlled breaths needed to maintain a predefined respiratory rate. EWS was implemented as a knowledge- and model-based system that autonomously and remotely controlled a mechanical ventilator (Evita 4, Dräger Medical, Lübeck, Germany). In a selected case study (n = 19 patients), ventilator settings chosen by the responsible physician were compared with the settings 10 min after the start of EWS and at the end of the study session. Neither unsafe ventilator settings nor failure of the system occurred. All patients were successfully transferred from controlled ventilation to assisted spontaneous breathing in a mean time of 37 ± 17 min (± SD). Early settings applied by the EWS did not significantly differ from the initial settings, except for the fraction of oxygen in inspired gas. During the later course, EWS significantly modified most of the ventilator settings and reduced the imposed respiratory load. A novel prototype automated weaning system was successfully developed. The first clinical application of EWS revealed that its operation was stable, safe ventilator settings were defined and the respiratory load of mechanical ventilation was decreased.

Adaptive support ventilation: State of the art review

Mechanical ventilation is one of the most commonly applied interventions in intensive care units. Despite its life-saving role, it can be a risky procedure for the patient if not applied appropriately. To decrease risks, new ventilator modes continue to be developed in an attempt to improve patient outcomes. Advances in ventilator modes include closed-loop systems that facilitate ventilator manipulation of variables based on measured respiratory parameters. Adaptive support ventilation (ASV) is a positive pressure mode of mechanical ventilation that is closed-loop controlled, and automatically adjust based on the patient's requirements. In order to deliver safe and appropriate patient care, clinicians need to achieve a thorough understanding of this mode, including its effects on underlying respiratory mechanics. This article will discuss ASV while emphasizing appropriate ventilator settings, their advantages and disadvantages, their particular effects on oxygenation and ventilation, and the monitoring priorities for clinicians.

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 the mechanical support to a patient's ventilatory needs and facilitate systematic and early recognition of their ability to breathe spontaneously and the potential for discontinuation of ventilation.

OBJECTIVES

To compare the duration of weaning from mechanical ventilation for critically ill ventilated adults and children when managed with automated closed loop 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.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2); MEDLINE (OvidSP) (1948 to August 2011); EMBASE (OvidSP) (1980 to August 2011); CINAHL (EBSCOhost) (1982 to August 2011); and the Latin American and Caribbean Health Sciences Literature (LILACS). In addition we received and reviewed auto-alerts for our search strategy in MEDLINE, EMBASE, and CINAHL up to August 2012. 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.

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 intensive care unit (ICU).

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

Pooled data from 15 eligible trials (14 adult, one paediatric) totalling 1173 participants (1143 adults, 30 children) indicated that automated closed loop systems reduced the geometric mean duration of weaning by 32% (95% CI 19% to 46%, P = 0.002), however heterogeneity was substantial (I(2) = 89%, P < 0.00001). Reduced weaning duration was found with mixed or medical ICU populations (43%, 95% CI 8% to 65%, P = 0.02) and Smartcare/PS™ (31%, 95% CI 7% to 49%, P = 0.02) but not in surgical populations or using other systems. Automated closed loop systems reduced the duration of ventilation (17%, 95% CI 8% to 26%) and ICU length of stay (LOS) (11%, 95% CI 0% to 21%). There was no difference in mortality rates or hospital LOS. Overall the quality of 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.

Three short perioperative infusions of n-3 PUFAs reduce systemic inflammation induced by cardiopulmonary bypass surgery: a randomized controlled trial

BACKGROUND

Fish oil (FO) has antiinflammatory effects, which might reduce systemic inflammation induced by a cardiopulmonary bypass (CPB).

OBJECTIVE

We tested whether perioperative infusions of FO modify the cell membrane composition, inflammatory responses, and clinical course of patients undergoing elective coronary artery bypass surgery.

DESIGN

A prospective randomized controlled trial was conducted in cardiac surgery patients who received 3 infusions of 0.2 g/kg FO emulsion or saline (control) 12 and 2 h before and immediately after surgery. Blood samples (7 time points) and an atrial biopsy (during surgery) were obtained to assess the membrane incorporation of PUFAs. Hemodynamic data, catecholamine requirements, and core temperatures were recorded at 10-min intervals; blood triglycerides, nonesterified fatty acids, glucose, lactate, inflammatory cytokines, and carboxyhemoglobin concentrations were measured at selected time points.

RESULTS

Twenty-eight patients, with a mean ± SD age of 65.5 ± 9.9 y, were enrolled with no baseline differences between groups. Significant increases in platelet EPA (+0.86%; P = 0.0001) and DHA (+0.87%; P = 0.019) were observed after FO consumption compared with at baseline. Atrial tissue EPA concentrations were higher after FO than after control treatments (+0.5%; P < 0.0001). FO did not significantly alter core temperature but decreased the postoperative rise in IL-6 (P = 0.018). Plasma triglycerides increased transiently after each FO infusion. Plasma concentrations of glucose, lactate, and blood carboxyhemoglobin were lower in the FO than in the control group on the day after surgery. Arrhythmia incidence was low with no significant difference between groups. No adverse effect of FO was detected.

CONCLUSIONS

Perioperative FO infusions significantly increased PUFA concentrations in platelet and atrial tissue membranes within 12 h of the first FO administration and decreased biological and clinical signs of inflammation. These results suggest that perioperative FO may be beneficial in elective cardiac surgery with CPB.

Weaning from mechanical ventilation: why are we still looking for alternative methods?

Most patients who require mechanical ventilation for longer than 24 hours, and who improve the condition leading to the indication of ventilatory support, can be weaned after passing a first spontaneous breathing test. The challenge is to improve the weaning of patients who fail that first test. We have methods that can be referred to as traditional, such as the T-tube, pressure support or synchronized intermittent mandatory ventilation (SIMV). In recent years, however, new applications of usual techniques as noninvasive ventilation, new ventilation methods such as automatic tube compensation (ATC), mandatory minute ventilation (MMV), adaptive support ventilation or automatic weaning systems based on pressure support have been described. Their possible role in weaning from mechanical ventilation among patients with difficult or prolonged weaning remains to be established.

Human versus Computer Controlled Selection of Ventilator Settings: An Evaluation of Adaptive Support Ventilation and Mid-Frequency Ventilation

Background. There are modes of mechanical ventilation that can select ventilator settings with computer controlled algorithms (targeting schemes). Two examples are adaptive support ventilation (ASV) and mid-frequency ventilation (MFV). We studied how different clinician-chosen ventilator settings are from these computer algorithms under different scenarios. Methods. A survey of critical care clinicians provided reference ventilator settings for a 70 kg paralyzed patient in five clinical/physiological scenarios. The survey-derived values for minute ventilation and minute alveolar ventilation were used as goals for ASV and MFV, respectively. A lung simulator programmed with each scenario's respiratory system characteristics was ventilated using the clinician, ASV, and MFV settings. Results. Tidal volumes ranged from 6.1 to 8.3 mL/kg for the clinician, 6.7 to 11.9 mL/kg for ASV, and 3.5 to 9.9 mL/kg for MFV. Inspiratory pressures were lower for ASV and MFV. Clinician-selected tidal volumes were similar to the ASV settings for all scenarios except for asthma, in which the tidal volumes were larger for ASV and MFV. MFV delivered the same alveolar minute ventilation with higher end expiratory and lower end inspiratory volumes. Conclusions. There are differences and similarities among initial ventilator settings selected by humans and computers for various clinical scenarios. The ventilation outcomes are the result of the lung physiological characteristics and their interaction with the targeting scheme.

Effort-adapted modes of assisted breathing

PURPOSE OF REVIEW

New developments in mechanical ventilation have focused on increasing the patient's control of the ventilator by implementing information on lung mechanics and respiratory drive. Effort-adapted modes of assisted breathing are presented and their potential advantages are discussed.

RECENT FINDINGS

Adaptive support ventilation, proportional assist ventilation with load adjustable gain factors and neurally adjusted ventilatory assist are ventilatory modes that follow the concept of adapting the assist to a defined target, instantaneous changes in respiratory drive or lung mechanics. Improved patient ventilator interaction, sufficient unloading of the respiratory muscles and increased comfort have been recently associated with these ventilator modalities. There are, however, scarce data with regard to outcome improvement, such as length of mechanical ventilation, ICU stay or mortality (commonly accepted targets to demonstrate clinical superiority).

SUMMARY

Within recent years, a major step forward in the evolution of assisted (effort-adapted) modes of mechanical ventilation was accomplished. There is growing evidence that supports the physiological concept of closed-loop effort-adapted assisted modes of mechanical ventilation. However, at present, the translation into a clear outcome benefit remains to be proven. In order to fill the knowledge gap that impedes the broader application, larger randomized controlled trials are urgently needed. However, with clearly proven drawbacks of conventional assisted modes such as pressure support ventilation, it is probably about time to leave these modes introduced decades ago behind.

Decisional responsibility for mechanical ventilation and weaning: an international survey

Introduction

Optimal management of mechanical ventilation and weaning requires dynamic and collaborative decision making to minimize complications and avoid delays in the transition to extubation. In the absence of collaboration, ventilation decision making may be fragmented, inconsistent, and delayed. Our objective was to describe the professional group with responsibility for key ventilation and weaning decisions and to examine organizational characteristics associated with nurse involvement.

Methods

A multi-center, cross-sectional, self-administered survey was sent to nurse managers of adult intensive care units (ICUs) in Denmark, Germany, Greece, Italy, Norway, Switzerland, Netherlands and United Kingdom (UK). We summarized data as proportions (95% confidence intervals (CIs)) and calculated odds ratios (OR) to examine ICU organizational variables associated with collaborative decision making.

Results

Response rates ranged from 39% (UK) to 92% (Switzerland), providing surveys from 586 ICUs. Interprofessional collaboration (nurses and physicians) was the most common approach to initial selection of ventilator settings (63% (95% CI 59 to 66)), determination of extubation readiness (71% (67 to 75)), weaning method (73% (69 to 76)), recognition of weaning failure (84% (81 to 87)) and weaning readiness (85% (82 to 87)), and titration of ventilator settings (88% (86 to 91)). A nurse-to-patient ratio other than 1:1 was associated with decreased interprofessional collaboration during titration of ventilator settings (OR 0.2, 95% CI 0.1 to 0.6), weaning method (0.4 (0.2 to 0.9)), determination of extubation readiness (0.5 (0.2 to 0.9)) and weaning failure (0.4 (0.1 to 1.0)). Use of a weaning protocol was associated with increased collaborative decision making for determining weaning (1.8 (1.0 to 3.3)) and extubation readiness (1.9 (1.2 to 3.0)), and weaning method (1.8 (1.1 to 3.0). Country of ICU location influenced the profile of responsibility for all decisions. Automated weaning modes were used in 55% of ICUs.

Conclusions

Collaborative decision making for ventilation and weaning was employed in most ICUs in all countries although this was influenced by nurse-to-patient ratio, presence of a protocol, and varied across countries. Potential clinical implications of a lack of collaboration include delayed adaptation of ventilation to changing physiological parameters, and delayed recognition of weaning and extubation readiness resulting in unnecessary prolongation of ventilation.

Mechanical ventilation in trauma

PURPOSE OF REVIEW

The purpose of this review is to evaluate new concepts in mechanical ventilation in trauma. We begin with the keystone of physiology prior to embarking on a discussion of several new modes of mechanical ventilation. We will discuss the use of noninvasive ventilation as a mode to prevent intubation and then go on to airway pressure release ventilation, high-frequency oscillatory ventilation, and computer-based, closed loop ventilation.

RECENT FINDINGS

The importance of preventing further injury in mechanical ventilation lies at the heart of the introduction of several new strategies of mechanical ventilation. New modes of ventilation have been developed to provide lung recruitment and alveolar stabilization at the lowest possible pressure.

SUMMARY

The old modes of continuous positive airway pressure and bilevel positive airway pressure have been actively introduced in clinical practice in the case of trauma patients. Used with proper pain management protocols, there has been a decrease in the incidence of intubation in blunt thoracic trauma. Airway pressure release ventilation has been gaining a role in the management of thoracic injury and may lead to less incidence of physiologic trauma to mechanically ventilated patients. High-frequency oscillatory ventilation has been shown to be effective in patient care by its ability to open and recruit the lung in trauma patients and in those with acute respiratory distress syndrome but it may not have a role in patients with inhalational injury. Closed loop ventilation is a technology that may better control major pulmonary parameters and lead to more rapid titration from the ventilator to spontaneous breathing.

Adaptive support ventilation versus conventional ventilation for total ventilatory support in acute respiratory failure

OBJECTIVE

To compare the short-term effects of adaptive support ventilation (ASV), an advanced closed-loop mode, with conventional volume or pressure-control ventilation in patients passively ventilated for acute respiratory failure.

DESIGN

Prospective crossover interventional multicenter trial.

SETTING

Six European academic intensive care units.

PATIENTS

Eighty-eight patients in three groups: patients with no obvious lung disease (n = 22), restrictive lung disease (n = 36) or obstructive lung disease (n = 30).

INTERVENTIONS

After measurements on conventional ventilation (CV) as set by the patients' clinicians, each patient was switched to ASV set to obtain the same minute ventilation as during CV (isoMV condition). If this resulted in a change in PaCO(2), the minute ventilation setting of ASV was readjusted to achieve the same PaCO(2) as in CV (isoCO(2) condition).

MEASUREMENTS AND RESULTS

Compared with CV, PaCO(2) during ASV in isoMV condition and minute ventilation during ASV in isoCO(2) condition were slightly lower, with lower inspiratory work/minute performed by the ventilator (p < 0.01). Oxygenation and hemodynamics were unchanged. During ASV, respiratory rate was slightly lower and tidal volume (Vt) slightly greater (p < 0.01), especially in obstructed patients. During ASV there were different ventilatory patterns in the three groups, with lower Vt in patients with restrictive disease and prolonged expiratory time in obstructed patients, thus mimicking the clinicians' choices for setting CV. In three chronic obstructive pulmonary disease patients the resulting Vt was unacceptably high.

CONCLUSIONS

Comparison between ASV and CV resulted either in similarities or in minor differences. Except for excessive Vt in a few obstructed patients, all differences were in favor of ASV.

Advanced closed loops during mechanical ventilation (PAV, NAVA, ASV, SmartCare)

New modes of mechanical ventilation with advanced closed loops are now available, and in the future these could assume a greater role in supporting critically ill patients in intensive care units (ICUs) for several reasons. Two modes of ventilation--proportional assist ventilation and neurally adjusted ventilatory assist--deliver assisted ventilation proportional to the patient's effort, improving patient-ventilator synchrony. Also, a few systems that automate the medical reasoning with advanced closed-loops, such as SmartCare and adaptive support ventilation, have the potential to improve knowledge transfer by continuously implementing automated protocols. Moreover, they may improve patient-ventilator interactions and outcomes, and provide a partial solution to the forecast clinician shortages by reducing ICU-related costs, time spent on mechanical ventilation, and staff workload. Preliminary studies are promising, and initial systems are currently being refined with increasing clinical experience. A new era of mechanical ventilation should emerge with these systems.

Adaptive support ventilation for gynaecological laparoscopic surgery in Trendelenburg position: bringing ICU modes of mechanical ventilation to the operating room

BACKGROUND AND OBJECTIVE

The aim of the present study was to test the efficacy of adaptive support ventilation (ASV) to automatically adapt the ventilatory settings to the changes in the respiratory mechanics that occur during pneumoperitoneum and Trendelenburg position in gynaecological surgeries.

METHODS

We prospectively studied 22 ASA I women scheduled for gynaecological laparoscopic surgery in the Trendelenburg position. After intravenous induction of general anaesthesia, patients were ventilated with ASV, a closed-loop mode of mechanical ventilation based on the Otis formula, designed to automatically adapt the ventilatory settings to changes in the patient's respiratory system mechanics, while maintaining preset minute ventilation. Respiratory mechanics variables, ventilatory setting parameters and analysis of blood gases were recorded at three time points: 5 min after induction (baseline), 15 min after pneumoperitoneum and Trendelenburg positioning (Pneumo-Trend) and 15 min after pneumoperitoneum withdrawal (final).

RESULTS

A reduction of 44.4% in respiratory compliance and an increase of 29.1% in airway resistance were observed during the Pneumo-Trend period. Despite these changes in respiratory mechanics, minute ventilation was kept constant. ASV adapted the ventilatory settings by automatically increasing inspiratory pressure by 3.2 +/- 0.9 cmH(2)O (+19%), P < 0.01, respiratory rate by 1.3 +/- 0.5 breaths per minute (+9%) and the inspiratory to total time ratio (T(i)/T(tot)) by 43.3%. At final time, these parameters returned towards their baseline values. Adequate gas exchange was maintained throughout all periods. PaCO(2) increased moderately (+13%) from 4.4 +/- 0.6 (baseline) to 5.0 +/- 0.9 kPa (Pneumo-Trend), P < 0.01; and decreased slightly at final time (4.7 +/- 0.8 kPa), P < 0.05. Clinician's intervention was needed in only one patient who showed a moderate hypercapnia (PaCO(2) 6.9 kPa) during pneumoperitoneum.

CONCLUSION

In healthy women undergoing gynaecologic laparoscopy, ASV automatically adapted the ventilatory settings to the changes in the respiratory mechanics, keeping constant the preset minute ventilation, providing an adequate exchange of respiratory gases and obviating clinician's interventions.

Adaptive support ventilation with percutaneous dilatational tracheotomy: a clinical study

We determined the need for changes in minute ventilation with adaptive support ventilation after percutaneous dilatational tracheotomy under endoscopic guidance in 34 intensive care unit patients. During the procedure, minute ventilation was not changed; only maximum pressure limits were adjusted, if necessary. After insertion of the tracheotomy, cannula minute ventilation was adjusted only if Paco(2)-values changed >or=0.5 kPa from baseline. In 74% of patients, adaptive support ventilation was unable to maintain minute ventilation during the use of the endoscope, mandating pressure limitation adjustments. In a minority of patients (26%), minute ventilation had to be adjusted to achieve similar Paco(2) values.

Clinical review: liberation from mechanical ventilation

Mechanical ventilation is the defining event of intensive care unit (ICU) management. Although it is a life saving intervention in patients with acute respiratory failure and other disease entities, a major goal of critical care clinicians should be to liberate patients from mechanical ventilation as early as possible to avoid the multitude of complications and risks associated with prolonged unnecessary mechanical ventilation, including ventilator induced lung injury, ventilator associated pneumonia, increased length of ICU and hospital stay, and increased cost of care delivery. This review highlights the recent developments in assessing and testing for readiness of liberation from mechanical ventilation, the etiology of weaning failure, the value of weaning protocols, and a simple practical approach for liberation from mechanical ventilation.

Automating the weaning process with advanced closed-loop systems

BACKGROUND

Limiting the duration of invasive ventilation is an important goal in caring for critically ill patients. Several clinical trials have shown that compared to traditional care, protocols can reduce the total duration of mechanical ventilation. Computerized or automated weaning has the potential to improve weaning, while decreasing associated workload, and to transfer best evidence into clinical practice by integrating closed-loop technology into protocols that can be operationalized continuously.

DISCUSSION

In this article, we review the principles of automated systems, discuss automated systems that can be used during weaning, and examine the best-current evidence from randomized trials and observational studies supporting their use. We highlight three commercially available systems (Mandatory Minute Ventilation, Adaptive Support Ventilation and SmartCare) that can be used to automate the weaning process. We note advantages and disadvantages associated with individual weaning systems and differences among them.

CONCLUSIONS

We discuss the potential role for automation in complimenting clinical acumen, reducing practice pattern variation and facilitating knowledge translation into clinical practice, and underscore the need for additional high quality investigations to evaluate automated weaning systems in different practice settings and diverse patient populations.