Lung-protective Mechanical Ventilation Strategies Research Articles

Incidence of mortality and morbidity related to postoperative lung injury in patients who have undergone abdominal or thoracic surgery: a systematic review and meta-analysis

Lung injury is a serious complication of surgery. We did a systematic review and meta-analysis to assess whether incidence, morbidity, and in-hospital mortality associated with postoperative lung injury are affected by type of surgery and whether outcomes are dependent on type of ventilation. We searched MEDLINE, CINAHL, Web of Science, and Cochrane Central Register of Controlled Trials for observational studies and randomised controlled trials published up to April, 2014, comparing lung-protective mechanical ventilation with conventional mechanical ventilation during abdominal or thoracic surgery in adults. Individual patients' data were assessed. Attributable mortality was calculated by subtracting the in-hospital mortality of patients without postoperative lung injury from that of patients with postoperative lung injury. We identified 12 investigations involving 3365 patients. The total incidence of postoperative lung injury was similar for abdominal and thoracic surgery (3·4% vs 4·3%, p=0·198). Patients who developed postoperative lung injury were older, had higher American Society of Anesthesiology scores and prevalence of sepsis or pneumonia, more frequently had received blood transfusions during surgery, and received ventilation with higher tidal volumes, lower positive end-expiratory pressure levels, or both, than patients who did not. Patients with postoperative lung injury spent longer in intensive care (8·0 [SD 12·4] vs 1·1 [3·7] days, p<0·0001) and hospital (20·9 [18·1] vs 14·7 [14·3] days, p<0·0001) and had higher in-hospital mortality (20·3% vs 1·4% p<0·0001) than those without injury. Overall attributable mortality for postoperative lung injury was 19% (95% CI 18-19), and differed significantly between abdominal and thoracic surgery patients (12·2%, 95% CI 12·0-12·6 vs 26·5%, 26·2-27·0, p=0·0008). The risk of in-hospital mortality was independent of ventilation strategy (adjusted HR 0·71, 95% CI 0·41-1·22). Postoperative lung injury is associated with increases in in-hospital mortality and durations of stay in intensive care and hospital. Attributable mortality due to postoperative lung injury is higher after thoracic surgery than after abdominal surgery. Lung-protective mechanical ventilation strategies reduce incidence of postoperative lung injury but does not improve mortality. None.

Matrix Metalloproteinases and Protein Tyrosine Kinases: Potential Novel Targets in Acute Lung Injury and ARDS

Acute lung injury (ALI) and ARDS fall within a spectrum of pulmonary disease that is characterized by hypoxemia, noncardiogenic pulmonary edema, and dysregulated and excessive inflammation. While mortality rates have improved with the advent of specialized ICUs and lung protective mechanical ventilation strategies, few other therapies have proven effective in the management of ARDS, which remains a significant clinical problem. Further development of biomarkers of disease severity, response to therapy, and prognosis is urgently needed. Several novel pathways have been identified and studied with respect to the pathogenesis of ALI and ARDS that show promise in bridging some of these gaps. This review will focus on the roles of matrix metalloproteinases and protein tyrosine kinases in the pathobiology of ALI in humans, and in animal models and in vitro studies. These molecules can act independently, as well as coordinately, in a feed-forward manner via activation of tyrosine kinase-regulated pathways that are pivotal in the development of ARDS. Specific signaling events involving proteolytic processing by matrix metalloproteinases that contribute to ALI, including cytokine and chemokine activation and release, neutrophil recruitment, transmigration and activation, and disruption of the intact alveolar-capillary barrier, will be explored in the context of these novel molecular pathways.

Extracorporeal carbon dioxide removal for patients with acute respiratory failure secondary to the acute respiratory distress syndrome: a systematic review.

Acute respiratory distress syndrome (ARDS) continues to have significant mortality and morbidity. The only intervention proven to reduce mortality is the use of lung-protective mechanical ventilation strategies, although such a strategy may lead to problematic hypercapnia. Extracorporeal carbon dioxide removal (ECCO2R) devices allow uncoupling of ventilation from oxygenation, thereby removing carbon dioxide and facilitating lower tidal volume ventilation. We performed a systematic review to assess efficacy, complication rates, and utility of ECCO2R devices. We included randomised controlled trials (RCTs), case–control studies and case series with 10 or more patients. We searched MEDLINE, Embase, LILACS (Literatura Latino Americana em Ciências da Saúde), and ISI Web of Science, in addition to grey literature and clinical trials registries. Data were independently extracted by two reviewers against predefined criteria and agreement was reached by consensus. Outcomes of interest included mortality, intensive care and hospital lengths of stay, respiratory parameters and complications. The review included 14 studies with 495 patients (two RCTs and 12 observational studies). Arteriovenous ECCO2R was used in seven studies, and venovenous ECCO2R in seven studies. Available evidence suggests no mortality benefit to ECCO2R, although post hoc analysis of data from the most recent RCT showed an improvement in ventilator-free days in more severe ARDS. Organ failure-free days or ICU stay have not been shown to decrease with ECCO2R. Carbon dioxide removal was widely demonstrated as feasible, facilitating the use of lower tidal volume ventilation. Complication rates varied greatly across the included studies, representing technological advances. There was a general paucity of high-quality data and significant variation in both practice and technology used among studies, which confounded analysis. ECCO2R is a rapidly evolving technology and is an efficacious treatment to enable protective lung ventilation. Evidence for a positive effect on mortality and other important clinical outcomes is lacking. Rapid technological advances have led to major changes in these devices and together with variation in study design have limited applicability of analysis. Further well-designed adequately powered RCTs are needed.

Initial ventilator settings for critically ill patients

The lung-protective mechanical ventilation strategy has been standard practice for management of acute respiratory distress syndrome (ARDS) for more than a decade. Observational data, small randomized studies and two recent systematic reviews suggest that lung protective ventilation is both safe and potentially beneficial in patients who do not have ARDS at the onset of mechanical ventilation. Principles of lung-protective ventilation include: a) prevention of volutrauma (tidal volume 4 to 8 ml/kg predicted body weight with plateau pressure <30 cmH2O); b) prevention of atelectasis (positive end-expiratory pressure ≥5 cmH2O, as needed recruitment maneuvers); c) adequate ventilation (respiratory rate 20 to 35 breaths per minute); and d) prevention of hyperoxia (titrate inspired oxygen concentration to peripheral oxygen saturation (SpO2) levels of 88 to 95%). Most patients tolerate lung protective mechanical ventilation well without the need for excessive sedation. Patients with a stiff chest wall may tolerate higher plateau pressure targets (approximately 35 cmH2O) while those with severe ARDS and ventilator asynchrony may require a short-term neuromuscular blockade. Given the difficulty in timely identification of patients with or at risk of ARDS and both the safety and potential benefit in patients without ARDS, lung-protective mechanical ventilation is recommended as an initial approach to mechanical ventilation in both perioperative and critical care settings.

ARDS: Who Needs to be Pronated?

Acute Distress Respiratory Syndrome (ARDS) is defined as a severe respiratory failure characterized by marked hypoxemia, bilateral infiltrates on the chest X-ray and the absence of signs of cardiogenic pulmonary edema. ARDS treatment remains primarily supportive and the use of mechanical ventilation with positive and expiratory pressure is required to maintain adequate gas exchange. Lung-protective mechanical ventilation strategy decreases mortality and increases ventilator free days. Prone positioning is considered a rescue therapy despite it improves gas exchange through resolution of dorsal atelectases with lung recruitment, better distribution of pulmonary perfusion and reduction of lung stress and strain. Nevertheless, several randomized controlled trials failed to demonstrate a reduction in mortality in pronated ARDS patients. Recent meta-analysis instead demonstrated a significant reduction of mortality in patients with most severe ARDS (PaO2/FiO2 ratio < 200) ventilated in prone position. These data were confirmed by the results of the PROSEVA study, published in June 2013 that reports a 16% reduction of mortality rate. The results of several meta-analysis and this large clinical trial suggest that prone positioning is a useful strategy that saves lives in more severely ill ARDS patients, when applied earlier and for at least 16 hours/day.

Inhaled nitric oxide in patients with the acute respiratory distress syndrome secondary to the 2009 influenza A (H1N1) infection in Canada

H1N1 had a self-limited respiratory illness; however, if hospitalization was required, 20-36% of patients required admission to the intensive care unit (ICU), and 80% of those patients required invasive mechanical ventilation. The case mortality ranged from 17-40%. In many of these patients, conventional mechanical ventilation strategies were not adequate to reverse their severe oxygenation defects. Adjunctive therapies in addition to lung protective mechanical ventilation strategies are often trialed in patients with oxygenation failure (defined as PaO2 60 mmHg despite FIO2 of 1.0 and optimal positive endexpiratory pressure [PEEP]). Inhaled nitric oxide (iNO) is one such therapy that has shown an improvement in oxygenation in patients with acute respiratory distress syndrome (ARDS). 2,3 In this report, we describe the epidemiologic characteristics, clinical features, treatment, and outcome in the cohort of patients who had ARDS due to H1N1 and were treated with iNO, and we compare their results with those of patients who did not receive iNO. Following approval by the University of Manitoba Biomedical Research Ethics Board, we conducted a retrospective chart review of all patients who presented with confirmed H1N1 and were treated with iNO in the teaching intensive care units at the University of Manitoba’s two adult medical intensive care units. Baseline demographic and clinical data of patients are shown in the Table. After administration of iNO, there was a significant and sustained improvement in the PaO2 and PaO2 /F IO2 ratio at 24 hr, and this improvement persisted throughout the study period (seven days). Three patients in the iNO group eventually required extracorporeal membrane oxygenation due to their profound ARDS. There were two deaths in the iNO group (n = 9) vs ten deaths in the control group (n = 94), 22% and 11%, respectively. Previous work has shown only a transient improvement in these parameters that, in many cases, did not persist past 24 hr. This result is significant as it shows a sustained improvement in oxygenation in these patients with viral pneumonia.

Host response to mechanical ventilation for viral respiratory tract infection

Respiratory syncytial virus (RSV) bronchiolitis causes severe respiratory tract infection in infants, frequently necessitating mechanical ventilatory support. However, life-saving, mechanical ventilation aggravates lung inflammation. We set up a model to dissect the host molecular response to mechanical ventilation in RSV infection. Furthermore, the response to induced hypercapnic acidosis, reported to dampen the inflammatory response to mechanical ventilation in non-infectious models, was assessed. BALB/c mice were inoculated with RSV or mock-suspension and ventilated for 5 h on day 5 post inoculation. Mechanical ventilation of infected mice resulted in enhanced cellular influx and increased concentrations of pro-inflammatory cytokines in the bronchoalveolar space. Microarray analysis showed that enhanced inflammation was associated with a molecular signature of a stress response to mechanical ventilation with little effect on the virus-induced innate immune response. Hypercapnic acidosis during mechanical ventilation of infected mice did not change host transcript profiles. We conclude that mechanical ventilation during RSV infection adds a robust but distinct molecular stress response to virus-induced innate immunity activation, emphasising the importance of lung-protective mechanical ventilation strategies. Induced hypercapnic acidosis has no major effect on host transcription profiles during mechanical ventilation for RSV infection, suggesting that this is a safe approach to minimise ventilator-induced lung injury.

Lung recruitment in ARDS: We are still confused, but on a higher PEEP level

Recruitment maneuvers and the application of high levels of positive end-expiratory pressure combined with lung protective mechanical ventilation strategies have been proposed to improve pulmonary function in patients with severe acute respiratory distress syndrome. However, the optimal way to achieve and maintain alveolar recruitment is still under debate.

Lung Protective Mechanical Ventilation Strategies in a Case of Mitral Valve Replacement Due to Thrombosis and Simultaneous Cesarean Section

Lung Protective Mechanical Ventilation Strategies in a Case of Mitral Valve Replacement Due to Thrombosis and Simultaneous Cesarean Section

Ventilator-induced lung injury in elderly patients and the research progress in the application of lung-protective mechanical ventilation strategies during surgery under general anesthesia

Mechanical ventilation may cause ventilator-induced lung injury (VILI). Because elderly patients always have the respiratory insufficiency,they are more Vulnerable to VILI during general anesthesia. This paper reviews the mechanism of ventilatorinduced lung injury in elderly patients during general anesthesia and the research progress in the application of lung-protective mechanical ventilation strategies. Key words: General anesthesia; Elderly patients; Mechanical ventilation; Lung injury; Lung-protective mechanical ventilation

The Effects of Repetitive Alveolar Recruitment on Oxygenation and Compliance in ARDS Patients

Background: If the effects of alveolar recruitment are beneficial, but of short duration, repetitive recruitment maneuvers (RMs) will be necessary to maintain oxygenation. This study was performed to assess the effect of repetitive alveolar recruitment, with high-sustained inflation pressure on oxygenation and compliance of the respiratory system, in patients with acute respiratory distress syndrome. Methods: Ten adult patients on ventilator support, with controlled mechanical ventilation, received three repetitive RMs with a high-sustained inflation pressure. The time intervals from the first to second RM and from the second to third RM were 8.42 ± 0.56 hours and 12.43 ± 1.45 hours, respectively. Recruitment was conducted by setting the ventilator mode to a continuous positive airway pressure of 40 cmH2O for 40 seconds. After each alveolar recruitment, the previous ventilator settings in the pressure control mode were re-established with a high positive end expiratory pressure. The FIO2, PaO2/FIO2 and lung compliance (tidal volume/[plateau pressure - PEEP]) were recorded with reference to the arterial blood gas analysis at both 30 minutes pre and post recruitment. Results: The FIO2 was able to be decreased from 0.9 to 0.5 while maintaining the PaO2 at higher than 80 mmHg after three recruitments. The PaO2/FIO2 improved from 98 to 288 and the compliance of the respiratory system improved from 26 to 41 ml/cmH2O after three recruitments. Conclusions: Our results suggest that repetitive recruitment can be used to maintain the beneficial effects of alveolar recruitment in patients with acute respiratory distress syndrome when supported using a lung protective mechanical ventilation strategy.

Lung-protective mechanical ventilation strategy for acute lung injury and acute respiratory distress syndrome

Mechanical ventilation (MV) is critical for survival of many patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS). However, MV can also cause ventilator-induced lung injury (VILI) which may delay or prevent recovery of some patients. Experimental models demonstrated that VILI could be reduced by modifying traditional MV approaches. Some clinical trials demonstrated improved clinical outcomes in patients who received lower tidal volumes and inspiratory airway pressures to prevent VILI from overdistention. Experimental models suggest that VILI may occur from cyclic opening and closing of small bronchioles and alveoli, and that this can be reduced by applying positive end-expiratory pressure (PEEP). Some clinical studies suggested that clinical outcomes may be improved with the use higher levels of PEEP than are used with traditional MV strategies. However, in these studies higher PEEP was combined with lower tidal volumes and inspiratory airway pressures. It is not yet clear th...

Tidal Volume Reduction in Patients with Acute Lung Injury When Plateau Pressures Are Not High

Use of a volume- and pressure-limited mechanical ventilation strategy improves clinical outcomes of patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS). However, the extent to which tidal volumes and inspiratory airway pressures should be reduced to optimize clinical outcomes is a controversial topic. This article addresses the question, "Is there a safe upper limit to inspiratory plateau pressure in patients with ALI/ARDS?" We reviewed data from animal models with and without preexisting lung injury, studies of normal human respiratory system mechanics, and the results of five clinical trials of lung-protective mechanical ventilation strategies. We also present an original analysis of data from the largest of the five clinical trials. The available data from each of these assessments do not support the commonly held view that inspiratory plateau pressures of 30 to 35 cm H2O are safe. We could not identify a safe upper limit for plateau pressures in patients with ALI/ARDS.

Lung-protective ventilation strategies in acute lung injury.

To review the challenges of providing mechanical ventilatory support for respiratory failure while avoiding ventilator-associated lung injury in patients with acute lung injury. To review the results of several randomized clinical trials of lung-protective ventilation strategies using conventional mechanical ventilators. Published reports of clinical trials comparing clinical outcomes of patients with acute lung injury, randomized to mechanical ventilation with either a lung-protective or a control, conventional, standard, or traditional approach. Lung-protective mechanical ventilation strategies are designed to prevent injury from overdistention by using lower tidal volumes and lower inspiratory pressures (volume- and pressure-limited ventilation) or injury from ventilation with atelectasis and alveolar flooding at end-expiration (open-lung ventilation). In one trial, clinical outcomes were better in the study group that received combined volume- and pressure-limited and open-lung strategies compared with the study group that received a conventional approach. Of four trials focusing on volume- and pressure-limited ventilation alone, three did not demonstrate improvements in clinical outcomes, whereas one demonstrated a substantial reduction in mortality and an increase in ventilator-free days. The different results in these four trials may be attributable to differences in tidal volumes between the study groups, chance variation, or differences in the management of respiratory acidosis. Evidence supports the use of a volume- and pressure-limited approach to mechanical ventilation in patients with acute lung injury. It is not yet clear whether the open-lung approach will further reduce mortality in patients receiving volume- and pressure-limited ventilation support.

Effect of cimetidine on upper gastrointestinal bleeding after renal transplantation.

<h3>BACKGROUND:</h3> A lung-protective mechanical ventilation strategy has become the hallmark of ventilation management for patients with acute respiratory failure. However, some patients progress to more severe forms of acute respiratory failure with refractory hypoxemia. In such circumstances, individualized titration of mechanical ventilation according to the patient9s specific respiratory and cardiovascular pathophysiology is desirable. A lung rescue team (LRT) was recently established at our institution to improve the medical care of patients with acute respiratory failure when conventional treatment fails. The aim of this report is to describe the consultation processes, the cardiopulmonary assessment, and the procedures of the LRT. <h3>METHODS:</h3> This was a retrospective review of the LRT management of patients with acute respiratory failure and refractory hypoxemia at Massachusetts General Hospital in Boston, Massachusetts. The LRT is composed of a critical care physician, the ICU respiratory therapist on duty, the ICU nurse on duty, and 2 critical care fellows. In the LRT approach, respiratory mechanics are evaluated through lung recruitment maneuvers and decremental PEEP trials by means of 3 tools: esophageal manometry, echocardiography, and electrical impedance tomography lung imaging. <h3>RESULTS:</h3> The LRT was consulted 89 times from 2014 to 2019 for evaluation and management of severely critically ill patients with acute respiratory failure and refractory hypoxemia on mechanical ventilation. The LRT was requested a median of 2 (interquartile range 1–6) d after intubation to optimize mechanical ventilation and to titrate PEEP in 77 (86%) subjects, to manage ventilation in 8 (9%) subjects on extracorporeal membrane oxygenation (ECMO), and to manage weaning strategy from mechanical ventilation in 4 (5%) subjects. The LRT found consolidations with atelectasis responsive to recruitment maneuvers in 79% (<i>n</i> = 70) of consultations. The LRT findings translated into a change of care in 81% (<i>n</i> = 72) of subjects. <h3>CONCLUSIONS:</h3> The LRT individualized the management of severe acute respiratory failure. The LRT consultations were shown to be effective, safe, and efficient, with an impact on decision-making in the ICU.