Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury

Lung and Diaphragm Protection During Mechanical Ventilation in Patients with Acute Respiratory Distress Syndrome

Patients with acute respiratory distress syndrome often require mechanical ventilation to maintain adequate gas exchange and to reduce the workload of the respiratory muscles. Although lifesaving, positive pressure mechanical ventilation can potentially injure the lungs and diaphragm, further worsening patient outcomes. While the effect of mechanical ventilation on the risk of developing lung injury is widely appreciated, its potentially deleterious effects on the diaphragm have only recently come to be considered by the broader intensive care unit community. Importantly, both ventilator-induced lung injury and ventilator-induced diaphragm dysfunction are associated with worse patient-centered outcomes.

High versus low positive end-expiratory pressure setting in patients receiving veno-venous extracorporeal membrane oxygenation support for severe acute respiratory distress syndrome: study protocol for the multicentre, randomised ExPress SAVER Trial

INTRODUCTION

While limiting the tidal volume to 6 mL/kg during veno-venous extracorporeal membrane oxygenation (V-V ECMO) to ameliorate lung injury in patients with acute respiratory distress syndrome (ARDS) is widely accepted, the best setting for positive end-expiratory pressure (PEEP) is still controversial. This study is being conducted to investigate whether a higher PEEP setting (15 cmH2O) during V-V ECMO can decrease the duration of ECMO support needed in patients with severe ARDS, as compared with a lower PEEP setting.

METHODS AND ANALYSIS

The study is an investigator-initiated, multicentre, open-label, two-arm, randomised controlled trial conducted with the participation of 20 intensive care units (ICUs) at academic as well as non-academic hospitals in Japan. The subjects of the study are patients with severe ARDS who require V-V ECMO support. Eligible patients will be randomised equally to the high PEEP group or low PEEP group. Recruitment to the study will continue until a total of 210 patients with ARDS requiring V-V ECMO support have been randomised. In the high PEEP group, PEEP will be set at 15 cmH2O from the start of V-V ECMO until the trials for liberation from V-V ECMO (or until day 28 after the allocation), while in the low PEEP group, the PEEP will be set at 5 cmH2O. Other treatments will be the same in the two groups. The primary endpoint of the study is the number of ECMO-free days until day 28, defined as the length of time (in days) from successful libration from V-V ECMO to day 28. The secondary endpoints are mortality on day 28, in-hospital mortality on day 60, ventilator-free days during the first 60 days and length of ICU stay.

ETHICS AND DISSEMINATION

Ethics approval for the trial at all the participating hospitals was obtained on 27 September 2022, by central ethics approval (IRB at Hiroshima University Hospital, C2022-0006). The results of this study will be presented at domestic and international medical congresses, and also published in scientific journals.

TRIAL REGISTRATION NUMBER

The Japan Registry of Clinical Trials jRCT1062220062. Registered on 28 September 2022.

PROTOCOL VERSION

28 March 2023, version 4.0.

Effect of Sivelestat in the Treatment of Acute Lung Injury and Acute Respiratory Distress Syndrome: A Systematic Review and Meta-Analysis

Background

The efficacy of neutrophil elastase inhibitor sivelestat in the treatment of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) remains controversial. A systematic review and meta-analysis were performed in accordance with the PRISMA guidelines assess the effect of sivelestat on ALI/ARDS patients, different studies were included.

Methods

Electronic databases, National Knowledge Infrastructure (CNKI), Wan fang data, VIP, PubMed, Embase, Springer, Ovid and the Cochrane Library were searched using the following key words: ("Sivelestat" OR "Elaspol") AND ("ARDS" OR "adult respiratory distress syndrome" OR "acute lung injury"). All databases published from January 2000 to August 2022. The treatment group was treated with sivelestat and the control group was given normal saline. The outcome measurements include the mortality of 28-30 days, mechanical ventilation time, ventilation free days, intensive care unit (ICU) stays, oxygenation index (PaO2/FiO2) on day 3, the incidence of adverse events. The literature search was conducted independently by 2 researchers using standardized methods. We used the Cochrane risk-of-bias tool to assess the quality of the included studies. Mean difference (MD), Standardized mean difference (SMD) and relative risk (RR) were calculated using random effects model or fixed effects model. All statistical analyses were performed using RevMan software 5.4.

Results

A total of 2050 patients were enrolled in 15 studies, including 1069 patients in treatment group and 981 patients in the control group. The results of the meta-analysis showed that: compared with the control group, sivelestat can reduce the mortality of 28-30 days (RR = 0.81, 95% CI = 0.66-0.98, p = 0.03) and the incidence of adverse events (RR = 0.91, 95% CI = 0.85-0.98, p = 0.01), shortened mechanical ventilation time (SMD = - 0.32, 95% CI = - 0.60 to - 0.04, p = 0.02) and ICU stays (SMD = - 0.72, 95% CI = - 0.92 to - 0.52, p < 0.00001), increased the ventilation free days (MD = 3.57, 95% CI = 3.42-3.73, p < 0.00001) and improve oxygenation index (PaO2/FiO2) on day 3 (SMD = 0.88, 95% CI = 0.39-1.36, p = 0.0004).

Conclusions

Sivelestat can not only reduce the mortality of ALI/ARDS patients within 28-30 days and the incidence of adverse events, shorten the mechanical ventilation time and ICU stays, increase ventilation free days, but also improve the oxygenation index of patients on days 3, which has a good effect on the treatment of ALI/ARDS. These findings need to be verified in large-scale trials.

Bioactive fraction from Plumeria obtusa L. attenuates LPS-induced acute lung injury in mice and inflammation in RAW 264.7 macrophages: LC/QToF-MS and molecular docking

In this study, the anti-inflammatory effects of the methanolic extract (TE) of Plumeria obtusa L. (aerial parts) and its fractions were evaluated in vitro, and active fraction was evaluated in vivo. Among tested extracts, dichloromethane fraction (DCM-F) exhibited the strongest inhibition of lipopolysaccharide (LPS)-induced nitric oxide (NO) in RAW 264.7 macrophages. The effect of DCM-F on LPS-induced acute lung injury (ALI) in mice was studied. The animals were divided into five groups (n = 7) randomly; Gp I: negative control, GP II: positive control (LPS group), GP III: standard (dexamethasone, 2 mg/kg b.wt), GP IV and V: DCM-F (100 mg/kg), and DEM-F (200 mg/kg), respectively. DCM-F at a dose of 200 mg/kg suppressed the ability of LPS to increase the levels of nitric oxide synthase (iNOS), NO, tumor necrosis factor-α (TNF-α), and interleukin 6 (IL-6), as measured by ELISA. In addition, the expression of cyclooxygenase-2 (COX-2) was reduced (determined by immunohistochemistry) and the level of malondialdehyde (MDA) was decreased while that of catalase was restored to the normal values. Furthermore, the histopathological scores of inflammation induced by LPS were reduced. Twenty-two compounds were tentatively identified in DCM-F using LC/ESI-QToF with iridoids, phenolic derivatives and flavonoids as major constituents. Identified compounds were subjected to two different molecular docking processes against iNOS and prostaglandin E synthase-1 target receptors. Notably, protoplumericin A and 13-O-coumaroyl plumeride were the most promising members compared to the co-crystallized inhibitor in each case. These findings suggested that DCM-F attenuates the LPS-induced ALI in experimental animals through its anti-inflammatory and antioxidant potential.

Strategies for lung- and diaphragm-protective ventilation in acute hypoxemic respiratory failure: a physiological trial

BACKGROUND

Insufficient or excessive respiratory effort during acute hypoxemic respiratory failure (AHRF) increases the risk of lung and diaphragm injury. We sought to establish whether respiratory effort can be optimized to achieve lung- and diaphragm-protective (LDP) targets (esophageal pressure swing - 3 to - 8 cm H2O; dynamic transpulmonary driving pressure ≤ 15 cm H2O) during AHRF.

METHODS

In patients with early AHRF, spontaneous breathing was initiated as soon as passive ventilation was not deemed mandatory. Inspiratory pressure, sedation, positive end-expiratory pressure (PEEP), and sweep gas flow (in patients receiving veno-venous extracorporeal membrane oxygenation (VV-ECMO)) were systematically titrated to achieve LDP targets. Additionally, partial neuromuscular blockade (pNMBA) was administered in patients with refractory excessive respiratory effort.

RESULTS

Of 30 patients enrolled, most had severe AHRF; 16 required VV-ECMO. Respiratory effort was absent in all at enrolment. After initiating spontaneous breathing, most exhibited high respiratory effort and only 6/30 met LDP targets. After titrating ventilation, sedation, and sweep gas flow, LDP targets were achieved in 20/30. LDP targets were more likely to be achieved in patients on VV-ECMO (median OR 10, 95% CrI 2, 81) and at the PEEP level associated with improved dynamic compliance (median OR 33, 95% CrI 5, 898). Administration of pNMBA to patients with refractory excessive effort was well-tolerated and effectively achieved LDP targets.

CONCLUSION

Respiratory effort is frequently absent  under deep sedation but becomes excessive when spontaneous breathing is permitted in patients with moderate or severe AHRF. Systematically titrating ventilation and sedation can optimize respiratory effort for lung and diaphragm protection in most patients. VV-ECMO can greatly facilitate the delivery of a LDP strategy.

TRIAL REGISTRATION

This trial was registered in Clinicaltrials.gov in August 2018 (NCT03612583).

Development of a Pleural Pressure Catheter via Continuous Fiberoptic Esophageal Pressure Measurements

There is growing research showing the importance of measuring esophageal pressure as a surrogate for pleural pressure for patients on mechanical ventilators. The most common measurement method uses a balloon catheter, whose accuracy can vary based on patient anatomy, balloon position, balloon inflation, and the presence of other tubes in the esophagus. The authors present the development and initial testing results of a new combination catheter, utilizing fiberoptic pressure sensing to provide more accurate esophageal pressure measurements and allowing for the incorporation of a feeding tube and temperature sensor.

Outcomes and Predictors of Severe Hyperoxemia in Patients Receiving Mechanical Ventilation: A Single-Center Cohort Study

RATIONALE

Supplemental oxygen is among the most commonly administered therapies in intensive care units. High supplemental oxygen exposure has been associated with harm in observational human studies and animal models. Yet no consensus exists regarding which dose and duration of high oxygen constitutes harmful hyperoxemia, and little is known regarding the clinical factors that predict potentially injurious exposure.

OBJECTIVES

To determine the level and duration of arterial oxygen (PaO2) associated with mortality among mechanically ventilated patients, and to identify the clinical factors that predict this exposure.

METHODS

We performed a retrospective cohort study of patients who received invasive mechanical ventilation at a single academic institution in 2017 and 2018. We used a generalized additive model to visualize the relationship between the measured PaO2 via arterial blood gases (ABGs) and 30-day mortality. We used multivariable logistic regression to identify patient- and hospital-level factors that predict exposure to harmful hyperoxemia.

RESULTS

We analyzed 2,133 patients with 33,310 ABGs obtained during mechanical ventilation. We identified a U-shaped relationship between PaO2 and mortality, where PaO2 was positively correlated with mortality above a threshold of 200 mmHg. 1,184 patients (55.5%) had at least one PaO2 level above this threshold. If patients spent an entire day exposed to PaO2 > 200 mmHg, they had 2.19 (95% CI 1.33 - 3.60, p = 0.002) greater odds of 30-day mortality in an adjusted analysis. Any exposure to severe hyperoxemia (PaO2 > 200 mmHg), was associated with mortality (OR 1.29, 95% CI 1.04 - 1.59, p = 0.021). The strongest clinical predictor of severe hyperoxemia exposure was the identity of the ICU in which mechanical ventilation was delivered.

CONCLUSIONS

Exposure to high arterial oxygen concentrations is common among mechanically ventilated patients, and the dose and duration of PaO2 ≥ 200 mmHg is associated with mortality. Severe hyperoxemia is highly variable across ICUs, and is far more common in clinical practice than in recent randomized trials of oxygen targeting strategies. Efforts to minimize this common and injurious exposure level are needed.

Glycyrrhizic Acid Alleviates Lipopolysaccharide (LPS)-Induced Acute Lung Injury by Regulating Angiotensin-Converting Enzyme-2 (ACE2) and Caveolin-1 Signaling Pathway

Acute lung injury (ALI) is mainly caused by severe infection, shock, trauma, and burn, which causes the extensive release of inflammatory factors and other mediators. As a major bioactive constituent of traditional Chinese herb licorice, glycyrrhizic acid (GA) plays an important effect on inflammatory regulation. Nevertheless, the exact mechanism of this effect remains unclear. The present study aims to explore the potential protective effect of GA on LPS-induced ALI. Our results showed that GA significantly attenuated LPS-induced ALI and decreased the production of inflammatory factors, including IL-1β, MCP-1, COX2, HMGB1, and adhesion molecules, such as E-selectin, VCAM-1, and modulated expression of angiotensin-converting enzyme 2 (ACE2). Moreover, treatment of ACE2 inhibitor (MLN-4760) reversed the effects of GA on the secretion of pro-inflammatory factors in ALI. Additionally, GA exerts its protective effect by regulating the ACE2 and caveolin-1/NF-κB signaling pathway. In conclusion, this study showed that GA alleviated LPS-induced ALI by upregulating ACE2 and inhibiting the caveolin-1/NF-κB signaling pathway.

Characterization of the strain-rate-dependent mechanical response of single cell-cell junctions

Cell-cell adhesions are often subjected to mechanical strains of different rates and magnitudes in normal tissue function. However, the rate-dependent mechanical behavior of individual cell-cell adhesions has not been fully characterized due to the lack of proper experimental techniques and therefore remains elusive. This is particularly true under large strain conditions, which may potentially lead to cell-cell adhesion dissociation and ultimately tissue fracture. In this study, we designed and fabricated a single-cell adhesion micro tensile tester (SCAµTT) using two-photon polymerization and performed displacement-controlled tensile tests of individual pairs of adherent epithelial cells with a mature cell-cell adhesion. Straining the cytoskeleton-cell adhesion complex system reveals a passive shear-thinning viscoelastic behavior and a rate-dependent active stress-relaxation mechanism mediated by cytoskeleton growth. Under low strain rates, stress relaxation mediated by the cytoskeleton can effectively relax junctional stress buildup and prevent adhesion bond rupture. Cadherin bond dissociation also exhibits rate-dependent strengthening, in which increased strain rate results in elevated stress levels at which cadherin bonds fail. This bond dissociation becomes a synchronized catastrophic event that leads to junction fracture at high strain rates. Even at high strain rates, a single cell-cell junction displays a remarkable tensile strength to sustain a strain as much as 200% before complete junction rupture. Collectively, the platform and the biophysical understandings in this study are expected to build a foundation for the mechanistic investigation of the adaptive viscoelasticity of the cell-cell junction.

Timing of Intubation in Coronavirus Disease 2019: A Study of Ventilator Mechanics, Imaging, Findings, and Outcomes

Objectives

Determine the variation in outcomes and respiratory mechanics between the subjects who are intubated earlier versus later in their coronavirus disease 2019 course.

Design

Retrospective cohort study.

Setting

Northwestern Memorial Hospital ICUs.

Patients

All patients intubated for coronavirus disease 2019 between March 2020 and June 2020.

Interventions

Patients were stratified by time to intubation: 30 subjects were intubated 4-24 hours after presentation and 24 subjects were intubated 5-10 days after presentation. Baseline characteristics, hospitalization, ventilator mechanics, and outcomes were extracted and analyzed. Ten clinically available CT scans were manually reviewed to identify evidence of pulmonary vascular thrombosis and intussusceptive angiogenesis.

Measurements and Main Results

Median time from symptom onset to intubation was significantly different between the early and late intubation cohorts, with the latter being intubated later in the course of their illness (7.9 vs 11.8 d; p = 0.04). The early intubation cohort had a lower mortality rate than the late intubation cohort (6% vs 30%, p < 0.001) without significantly different respiratory mechanics at the time of intubation. The late intubation cohort was noted to have higher dead space ratio (0.40 vs 0.52; p = 0.03). On review of CT scans, the late intubation cohort also had more dilated peripheral segments on imaging (two segments vs five segments).

Conclusions

The question as to whether delaying intubation is beneficial or harmful for patients with coronavirus disease 2019-induced hypoxemic respiratory failure has yet to be answered. As our approaches to coronavirus disease 2019 continue to evolve, the decision of timing of intubation remains paramount. Although noninvasive ventilation may allow for delaying intubation, it is possible that there are downstream effects of delayed intubation that should be considered, including the potential for pulmonary vascular thrombosis and intussusceptive angiogenesis with delayed intubation.

Decreased mortality in acute respiratory distress syndrome patients treated with corticosteroids: an updated meta-analysis of randomized clinical trials with trial sequential analysis

BACKGROUND

The possible benefits associated with corticosteroid treatment in acute respiratory distress syndrome (ARDS) patients are not fully known. We conducted an updated meta-analysis to assess the effect of corticosteroids in the treatment of patients with ARDS.

METHODS

We systematically searched MEDLINE, Embase, and the Cochrane Library from inception to January 2021 via Ovid to identify randomized controlled trials evaluating the efficacy of glucocorticoids in the treatment of patients with ARDS. The primary outcome was hospital mortality. Secondary outcomes included the number of ventilator-free days at day 28, oxygenation improvement (PaO2/FIO2 ratios), and adverse events.

RESULTS

Nine studies with 1371 participants were analyzed. The pooled analysis revealed that glucocorticoid use was associated with reduced mortality [relative risk (RR), 0.83; 95% confidence interval (CI) 0.74-0.93; P < 0.01; I2 = 37], and the statistical power was confirmed by trial sequential analysis. Glucocorticoids might also significantly increase the number of ventilator-free days at day 28 (mean deviation 3.66 days, 95% CI 2.64-4.68; P < 0.01) and improve oxygenation (standardized mean difference 4.17; 95% CI 2.32-6.02; P < 0.01). In addition, glucocorticoid use was not associated with increased risks of new infection (RR 0.84; 95% CI 0.70-1.01; P = 0.07) and hyperglycemia (RR 1.11; 95% CI 0.99-1.23; P = 0.06).

CONCLUSIONS

The use of glucocorticoids might result in reduced mortality in patients with ARDS. Glucocorticoids might be recommended as an adjunct to standard care for ARDS; however, the optimal dose and duration of steroid therapy remains unknown and further studies are needed.

Persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a significant clinical problem characterized by refractory and severe hypoxemia secondary to elevated pulmonary vascular resistance resulting in right-to-left extrapulmonary shunting of deoxygenated blood. PPHN is associated with diverse cardiopulmonary disorders and a high early mortality rate for infants with severe PPHN. Surviving infants with PPHN have an increased risk of long-term morbidities. PPHN physiology can be categorized by (1) maladaptation: pulmonary vessels have normal structure and number but have abnormal vasoreactivity; (2) excessive muscularization: increased smooth muscle cell thickness and increased distal extension of muscle to vessels that are usually not muscularized; and (3) underdevelopment: lung hypoplasia associated with decreased pulmonary artery number. Treatment involves adequate lung recruitment, optimization of cardiac output and left ventricular function, and pulmonary vasodilators such as inhaled nitric oxide. Infants who fail to respond to conventional therapy should be evaluated for lethal lung disorders including alveolar-capillary dysplasia, T-box transcription factor 4 gene, thyroid transcription factor-1, ATP-binding cassette A3 gene, and surfactant protein diseases.

Disease Mechanisms of Perioperative Organ Injury

Despite substantial advances in anesthesia safety within the past decades, perioperative mortality remains a prevalent problem and can be considered among the top causes of death worldwide. Acute organ failure is a major risk factor of morbidity and mortality in surgical patients and develops primarily as a consequence of a dysregulated inflammatory response and insufficient tissue perfusion. Neurological dysfunction, myocardial ischemia, acute kidney injury, respiratory failure, intestinal dysfunction, and hepatic impairment are among the most serious complications impacting patient outcome and recovery. Pre-, intra-, and postoperative arrangements, such as enhanced recovery after surgery programs, can contribute to lowering the occurrence of organ dysfunction, and mortality rates have improved with the advent of specialized intensive care units and advances in procedures relating to extracorporeal organ support. However, no specific pharmacological therapies have proven effective in the prevention or reversal of perioperative organ injury. Therefore, understanding the underlying mechanisms of organ dysfunction is essential to identify novel treatment strategies to improve perioperative care and outcomes for surgical patients. This review focuses on recent knowledge of pathophysiological and molecular pathways leading to perioperative organ injury. Additionally, we highlight potential therapeutic targets relevant to the network of events that occur in clinical settings with organ failure.

An Intensive Care Unit Outbreak of Acute Respiratory Distress Syndrome due to Human Metapneumo Virus Infection

Human metapneumo virus is an emerging cause of upper and lower respiratory tract illness with increasing reports of a varied spectrum of disease over all age groups. We report an outbreak of 6 cases of human metapneumo virus infection in the intensive care unit of a metropolitan tertiary care center over 6 weeks, leading to severe acute respiratory distress syndrome. We report the subsequent favorable outcomes due to the institution of extracorporeal membrane oxygenation.

Inhaled TRIM72 Protein Protects Ventilation Injury to the Lung through Injury-guided Cell Repair

Studies showed that TRIM72 is essential for repair of alveolar cell membrane disruptions, and exogenous recombinant human TRIM72 protein (rhT72) demonstrated tissue-mending properties in animal models of tissue injury. Here we examine the mechanisms of rhT72-mediated lung cell protection in vitro and test the efficacy of inhaled rhT72 in reducing tissue pathology in a mouse model of ventilator-induced lung injury. In vitro lung cell injury was induced by glass beads and stretching. Ventilator-induced lung injury was modeled by injurious ventilation at 30 ml/kg tidal volume. Affinity-purified rhT72 or control proteins were added into culture medium or applied through nebulization. Cellular uptake and in vivo distribution of rhT72 were detected by imaging and immunostaining. Exogenous rhT72 maintains membrane integrity of alveolar epithelial cells subjected to glass bead injury in a dose-dependent manner. Inhaled rhT72 decreases the number of fatally injured alveolar cells, and ameliorates tissue-damaging indicators and cell injury markers after injurious ventilation. Using in vitro stretching assays, we reveal that rhT72 improves both cellular resilience to membrane wounding and membrane repair after injury. Image analysis detected rhT72 uptake by rat alveolar epithelial cells, which can be inhibited by a cholesterol-disrupting agent. In addition, inhaled rhT72 distributes to the distal lungs, where it colocalizes with phosphatidylserine detection on nonpermeabilized lung slices to label wounded cells. In conclusion, our study showed that inhaled rhT72 accumulates in injured lungs and protects lung tissue from ventilator injury, the mechanisms of which include improving cell resilience to membrane wounding, localizing to injured membrane, and augmenting membrane repair.

Variable effectiveness of stepwise implementation of nudge-type interventions to improve provider compliance with intraoperative low tidal volume ventilation

BACKGROUND

Identifying mechanisms to improve provider compliance with quality metrics is a common goal across medical disciplines. Nudge interventions are minimally invasive strategies that can influence behavioural changes and are increasingly used within healthcare settings. We hypothesised that nudge interventions may improve provider compliance with lung-protective ventilation (LPV) strategies during general anaesthesia.

METHODS

We developed an audit and feedback dashboard that included information on both provider-level and department-level compliance with LPV strategies in two academic hospitals, two non-academic hospitals and two academic surgery centres affiliated with a single healthcare system. Dashboards were emailed to providers four times over the course of the 9-month study. Additionally, the default setting on anaesthesia machines for tidal volume was decreased from 700 mL to 400 mL. Data on surgical cases performed between 1 September 2016 and 31 May 2017 were examined for compliance with LPV. The impact of the interventions was assessed via pairwise logistic regression analysis corrected for multiple comparisons.

RESULTS

A total of 14 793 anaesthesia records were analysed. Absolute compliance rates increased from 59.3% to 87.8%preintervention to postintervention. Introduction of attending physician dashboards resulted in a 41% increase in the odds of compliance (OR 1.41, 95% CI 1.17 to 1.69, p=0.002). Subsequently, the addition of advanced practice provider and resident dashboards lead to an additional 93% increase in the odds of compliance (OR 1.93, 95% CI 1.52 to 2.46, p<0.001). Lastly, modifying ventilator defaults led to a 376% increase in the odds of compliance (OR 3.76, 95% CI 3.1 to 4.57, p<0.001).

CONCLUSION

Audit and feedback tools in conjunction with default changes improve provider compliance.

Alveolar Fluid Clearance in Pathologically Relevant Conditions: In Vitro and In Vivo Models of Acute Respiratory Distress Syndrome

Critically ill patients with respiratory failure from acute respiratory distress syndrome (ARDS) have reduced ability to clear alveolar edema fluid. This reduction in alveolar fluid clearance (AFC) contributes to the morbidity and mortality in ARDS. Thus, it is important to understand why AFC is reduced in ARDS in order to design targeted therapies. In this review, we highlight experiments that have advanced our understanding of ARDS pathogenesis, with particular reference to the alveolar epithelium. First, we review how vectorial ion transport drives the clearance of alveolar edema fluid in the uninjured lung. Next, we describe how alveolar edema fluid is less effectively cleared in lungs affected by ARDS and describe selected in vitro and in vivo experiments that have elucidated some of the molecular mechanisms responsible for the reduced AFC. Finally, we describe one potential therapy that targets this pathway: bone marrow-derived mesenchymal stem (stromal) cells (MSCs). Based on preclinical studies, MSCs enhance AFC and promote the resolution of pulmonary edema and thus may offer a promising cell-based therapy for ARDS.

The Effect of Positive End-Expiratory Pressure on Intracranial Pressure and Cerebral Hemodynamics

BACKGROUND

Lung protective ventilation has not been evaluated in patients with brain injury. It is unclear whether applying positive end-expiratory pressure (PEEP) adversely affects intracranial pressure (ICP) and cerebral perfusion pressure (CPP). We aimed to evaluate the effect of PEEP on ICP and CPP in a large population of patients with acute brain injury and varying categories of acute lung injury, defined by PaO2/FiO2.

METHOD

Retrospective data were collected from 341 patients with severe acute brain injury admitted to the ICU between 2008 and 2015. These patients experienced a total of 28,644 paired PEEP and ICP observations. Demographic, hemodynamic, physiologic, and ventilator data at the time of the paired PEEP and ICP observations were recorded.

RESULTS

In the adjusted analysis, a statistically significant relationship between PEEP and ICP and PEEP and CPP was found only among observations occurring during periods of severe lung injury. For every centimeter H2O increase in PEEP, there was a 0.31 mmHg increase in ICP (p = 0.04; 95 % CI [0.07, 0.54]) and a 0.85 mmHg decrease in CPP (p = 0.02; 95 % CI [-1.48, -0.22]).

CONCLUSION

Our results suggest that PEEP can be applied safely in patients with acute brain injury as it does not have a clinically significant effect on ICP or CPP. Further prospective studies are required to assess the safety of applying a lung protective ventilation strategy in brain-injured patients with lung injury.

Why is prone positioning so unpopular?

Recent studies have shown acute respiratory distress syndrome (ARDS) to be underdiagnosed and inadequately treated, as evidenced by underutilization of low-tidal volume ventilation. Despite a proven survival benefit in patients with severe ARDS, studies have also shown underutilization of prone positioning. Many questions persist as to the reasons for prone positioning's unpopularity. Additional studies are required to uncover the causes of this prone positioning underutilization phenomenon.

The impact of inspiratory pressure on stroke volume variation and the evaluation of indexing stroke volume variation to inspiratory pressure under various preload conditions in experimental animals

PURPOSE

Stroke volume variation (SVV) measures fluid responsiveness, enabling optimal fluid management under positive pressure ventilation. We aimed to investigate the effect of peak inspiratory pressure (PIP) on SVV under various preload conditions in experimental animals and to ascertain whether SVV indexed to PIP decreases the effect.

METHODS

Mild and moderate hemorrhage models were created in nine anesthetized, mechanically ventilated beagle dogs by sequentially removing 10 and then an additional 10 ml/kg of blood, respectively. In all the animals, PIP was incrementally increased by 4 cmH2O, from 5 to 21 cmH2O. SVV was measured by arterial pulse contour analysis. Stroke volume was derived using a thermodilution method, and central venous pressure and mean arterial pressure were also measured.

RESULTS

SVV increased according to PIP with significant correlation at baseline, with mild hemorrhage and moderate hemorrhage. PIP regression coefficients at baseline and in the mild and moderate hemorrhage models were 0.59, 0.86, and 1.4, respectively. Two-way repeated-measures analysis of variance showed that PIP and the degree of hemorrhage had a significant interaction effect on SVV (p = 0.0016). SVV indexed to PIP reflected the hemorrhage status regardless of PIP changes ≥9 cmH2O.

CONCLUSIONS

PIP is significantly correlated with SVV, even under hypovolemia, and the effect is enhanced with decreasing preload volumes. Compared with SVV, the indexed SVV was less susceptible to higher inspiratory pressures.

Reduced length of stay in radical cystectomy patients with oral versus parenteral post-operative nutrition protocol

BACKGROUND

In Europe, parenteral nutrition is often used after radical cystectomy to avoid postoperative malnourishment. To the best of our knowledge, however, there is a paucity of data to conclude on the best modality for delivering nutritional support to this patient group.

OBJECTIVE

The parenteral nutrition policy was reconsidered and an oral nutrition protocol was implemented by the clinical pharmacist and evaluated in terms of length of stay, number and type of postoperative complications and parenteral nutrition avoided costs.

SETTING

A prospective interventional non-randomized before-after study was conducted. Regular radical cystectomy patients presenting without preoperative contra-indications for enteral nutrition were eligible.

METHODS

Postoperatively, in the control group, the parenteral nutrition policy from the ward was applied. Parenteral nutrition was initiated systematically and continued until the patient was able to tolerate solid food. In the interventional group, an oral nutrition protocol was implemented. Parenteral nutrition could be initiated if oral intake remained insufficient after 5 days. Main outcome measure The primary end point was postoperative length of stay. Secondary endpoints included the number of patients in whom the oral nutrition protocol was implemented successfully, as well as the number and type of postoperative complications.

RESULTS

A total of 94 eligible patients was assigned consecutively to the control (n = 48) and to the interventional group (n = 46). Baseline demographics were comparable. A significant reduction in median length of stay was associated with the oral nutrition protocol [18 days (IQR 15-22) in the control group vs. 14 days (IQR 13-18) in the interventional group (p < 0.001)]. In 40 out of 46 patients from the interventional group, the oral nutrition protocol was implemented successfully. The number and type of postoperative complications did not differ significantly. Implementing the oral nutrition protocol resulted in a direct parenteral nutrition infusion bag cost saving of approximately €512 and a reduction in hospitalization cost of €2,608 per patient.

CONCLUSION

The findings of our study showed that an oral nutrition protocol, when compared to the systematic postoperative use of parenteral nutrition, was associated with a decreased length of stay and costs in a regular radical cystectomy patient population.

GADD45a promoter regulation by a functional genetic variant associated with acute lung injury

Rationale

Growth arrest DNA damage inducible alpha (GADD45a) is a stress-induced gene we have shown to participate in the pathophysiology of ventilator-induced lung injury (VILI) via regulation of mechanical stress-induced Akt ubiquitination and phosphorylation. The regulation of GADD45a expression by mechanical stress and its relationship with acute lung injury (ALI) susceptibility and severity, however, remains unknown.

Objectives

We examined mechanical stress-dependent regulatory elements (MSRE) in the GADD45a promoter and the contribution of promoter polymorphisms in GADD45a expression and ALI susceptibility.

Methods and Results

Initial studies in GADD45a knockout and heterozygous mice confirmed the relationship of GADD45a gene dose to VILI severity. Human lung endothelial cells (EC) transfected with a luciferase vector containing the full length GADD45a promoter sequence (−771 to +223) demonstrated a >4 fold increase in GADD45a expression in response to 18% cyclic stretch (CS, 4 h) compared to static controls while specific promoter regions harboring CS-dependent MSRE were identified using vectors containing serial deletion constructs of the GADD45a promoter. In silico analyses of GADD45a promoter region (−371 to −133) revealed a potential binding site for specificity protein 1 (SP1), a finding supported by confirmed SP1 binding with the GADD45a promoter and by the significant attenuation of CS-dependent GADD45a promoter activity in response to SP1 silencing. Separately, case-control association studies revealed a significant association of a GADD45a promoter SNP at −589 (rs581000, G>C) with reduced ALI susceptibility. Subsequently, we found allelic variation of this SNP is associated with both differential GADD45a expression in mechanically stressed EC (18% CS, 4 h) and differential binding site of interferon regulatory factor 7 (IRF7) at this site.

Conclusion

These results strongly support a functional role for GADD45a in ALI/VILI and identify a specific gene variant that confers risk for ALI.

[Ages of sitting up and walking in preterm newborns less than 1,500 G with bronchopulmonary dysplasia]

INTRODUCTION

Adverse neurological events in very low birth weight (VLBW) children with bronchopulmonary dysplasia (BPD) are more frequent than in children without. An understanding of the ages when preterm infants acquire certain motor skills will give parents more appropriate information on motor development. The objective of the present study is to estimate the influence between BPD and the age of acquisition of sitting unsupported and independent walking in VLBW children with normal neurological examination at 2 years of corrected age.

PATIENTS AND METHODS

A longitudinal study was conducted on a cohort of 885 children with VLBW, admitted to the Hospital "12 de Octubre" between January 1991 and December 2003. Age for both skills was established by interview with parents. Means were compared with t-test and Bonferroni adjustment where appropriate.

RESULTS

Both motor skills were acquired later in the group with BPD (7.8±2m vs. 7.1±1.3m for sitting unsupported and 14.5±3.8m vs. 13.4±2.5m for walking) (P<.001). BPD was associated with delayed acquisition (above p90) of these skills, OR=2.6 (1.6-4.1) for sitting and OR=2.8 (1.6-4.8) for walking. Association was found after adjusting for gestational age (GA) and weight.

CONCLUSION

BPD was associated with delayed acquisition of both skills in VLBW children with normal neurological examination at 2 years.

Role of non-invasive ventilation in managing life-threatening acute exacerbation of interstitial pneumonia

INTRODUCTION

Invasive mechanical ventilation (IMV) is not effective for acute exacerbation of interstitial pneumonia (AE-IP); however, the role of non-invasive ventilation (NIV) for this condition remains unknown.

METHODS

Comparisons were made for two periods: before (October 2001 - September 2003) and after (October 2004 - September 2006) the introduction of NIV as the primary method of mechanical ventilation for AE-IP. We retrospectively screened emergent admissions and enrolled consecutively those patients with AE-IP who had acutely worsening hypoxemia with new infiltrates, background chronic interstitial CT changes, and no findings suggestive of other diseases. The two periods were compared primarily for 60-day survival and secondarily for other outcomes associated with mechanical ventilation.

RESULTS

Medical records were retrieved for 11 episodes in 11 patients identified from 485 pre-NIV records and 27 episodes in 22 patients from 859 post-NIV records. Five patients required IMV in the earlier cohort and 9 patients received NIV in the later cohort. Although there was no difference in the PaO(2)/FiO(2) ratio on admission (167 vs. 139), the 60-day survival rate for all episodes in the later cohort was better than in the earlier cohort (27% vs. 65%, p=0.02). Moreover, the NIV-administered group had a better 60-day survival rate (0% vs. 44%, p=0.03), shorter high-care unit stay (17 vs. 6 days, p=0.03) and better-preserved verbal communication (0 vs., 89%) than the IMV-administered group.

CONCLUSION

Use of NIV in place of IMV for the management of life-threatening AE-IP appears to result in a better 60-day survival rate, lower high-care unit use and better patient tolerability.

Extrapulmonary ventilation for unresponsive severe acute respiratory distress syndrome after pulmonary resection

BACKGROUND

The purpose of this study was to evaluate the feasibility of integrating an artificial, pumpless extracorporeal membrane ventilator (Novalung) to near static mechanical ventilation and its efficacy in patients with severe postresectional acute respiratory distress syndrome (ARDS) unresponsive to optimal conventional treatment.

METHODS

Indications were severe postresectional and unresponsive acute respiratory distress syndrome, hemodynamic stability, and no significant peripheral arterial occlusive disease or heparin-induced thrombocytopenia. Management included placement of the arteriovenous femoral transcutaneous interventional lung-assist membrane ventilator, lung rest at minimal mechanical ventilator settings, and optimization of systemic oxygen consumption and delivery.

RESULTS

Among 239 pulmonary resections performed between 2005 and 2006, 7 patients (2.9%) experienced, 4 +/- 0.8 days after 5 pneumonectomies and 2 lobectomies, a severe (Murray score, 2.9 +/- 0.3) acute respiratory distress syndrome unresponsive to 4 +/- 2 days of conventional therapy. The interventional lung-assist membrane ventilator was left in place 4.3 +/- 2.5 days, and replaced only once for massive clotting. During this time, 29% +/- 0.3% or 1.4 +/- 0.36 L/min of the cardiac output perfused the device, without hemodynamic impairment. Using a sweep gas flow of 10.7 +/- 3.8 L/min, the device allowed an extracorporeal carbon dioxide removal of 255 +/- 31 mL/min, lung(s) rest (tidal volume, 2.7 +/- 0.8 mL/kg; respiratory rate, 6 +/- 2 beats/min; fraction of inspired oxygen, 0.5 +/- 0.1), early (<24 hours) significant improvement of respiratory function, and reduction of plasmatic interleukin-6 levels (p < 0.001) and Murray score (1.25 +/- 0.1; p < 0.003). All but 1 patient (14%) who died of multiorgan failure were weaned from mechanical ventilation 8 +/- 3 days after removal of the interventional lung-assist membrane ventilator, and all of them were discharged from the hospital.

CONCLUSIONS

The integration of this device to near static mechanical ventilation of the residual native lung(s) is feasible and highly effective in patients with severe and unresponsive acute respiratory distress syndrome after pulmonary resection.

Centromere DNA, proteins and kinetochore assembly in vertebrate cells

The centromere is a specialized region of the chromosome that is essential for faithful chromosome segregation during mitosis and meiosis in eukaryotic cells. It is the site at which the kinetochore, the functional nucleoprotein complex responsible for microtubule binding and chromosome movement, is assembled through complex molecular mechanisms. Herein, I review recent advances in our understanding of centromeric DNAs as sites for kinetochore assembly and the mechanisms underlying kinetochore assembly in vertebrate cells.

Meta-analysis of controlled trials of ventilator therapy in acute lung injury and acute respiratory distress syndrome: an alternative perspective

OBJECTIVE

The role of protective ventilation in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) is controversial. Evidence was sought from published randomised trials for a consistent treatment effect of protective ventilation and any covariate modification.

DESIGN

Meta-analysis of protective ventilation trials in ALI/ARDS and meta-regression of covariates on treatment effect (log odds ratio), with respect to 28-day mortality. Heterogeneity impact on the meta-analysis was assessed by the H statistic (substantial impact, >1.5) and graphical analysis. Five trials with a total of 1,202 patients were considered.

MEASUREMENTS AND RESULTS

Average 28-day mortality was 0.40 in the treatment group (protective ventilation, n=605) vs. 0.46 in the control group (control ventilation, n=597). The treatment effect (odds ratio) was: fixed-effects, 0.71 (95% CI 0.56-0.91, p=0.006; heterogeneity, p=0.06) and random effects: 0.80 (95% CI 0.49-1.31, p=0.37). Heterogeneity impact (H statistic=1.50) was adjudged as modest. The treatment effect was significant and (a) favoured protective ventilation for a tidal volume less than 7.7 ml/kg predicted (treatment group) and a mean plateau pressure of 30 cmH(2)O or higher (control group) but was not influenced by plateau pressure 21-30 cmH(2)O (treatment group) and (b) depended upon plateau pressure difference greater than 5-7 cmH(2)O between protective ventilation and standard ventilation.

CONCLUSIONS

Overall treatment effect estimate favoured protective ventilation but did not achieve statistical significance. Protective ventilation depended upon threshold levels of tidal volume, plateau pressure, and plateau pressure difference.

Bench-to-bedside review: Permissive hypercapnia

Current protective lung ventilation strategies commonly involve hypercapnia. This approach has resulted in an increase in the clinical acceptability of elevated carbon dioxide tension, with hypoventilation and hypercapnia 'permitted' in order to avoid the deleterious effects of high lung stretch. Advances in our understanding of the biology of hypercapnia have prompted consideration of the potential for hypercapnia to play an active role in the pathogenesis of inflammation and tissue injury. In fact, hypercapnia may protect against lung and systemic organ injury independently of ventilator strategy. However, there are no clinical data evaluating the direct effects of hypercapnia per se in acute lung injury. This article reviews the current clinical status of permissive hypercapnia, discusses insights gained to date from basic scientific studies of hypercapnia and acidosis, identifies key unresolved concerns regarding hypercapnia, and considers the potential clinical implications for the management of patients with acute lung injury.

Permissive hypercapnia--role in protective lung ventilatory strategies

"Permissive hypercapnia" is an inherent element of accepted protective lung ventilation. However, there are no clinical data evaluating the efficacy of hypercapnia per se, independent of ventilator strategy. In the absence of such data, it is necessary to determine whether the potential exists for an active role for hypercapnia, distinct from the demonstrated benefits of reduced lung stretch. In this review, we consider four key issues. First, we consider the evidence that protective lung ventilatory strategies improve survival and we explore current paradigms regarding the mechanisms underlying these effects. Second, we examine whether hypercapnic acidosis may have effects that are additive to the effects of protective ventilation. Third, we consider whether direct elevation of CO(2), in the absence of protective ventilation, is beneficial or deleterious. Fourth, we address the current evidence regarding the buffering of hypercapnic acidosis in ARDS. These perspectives reveal that the potential exists for hypercapnia to exert beneficial effects in the clinical context. Direct administration of CO(2) is protective in multiple models of acute lung and systemic injury. Nevertheless, several specific concerns remain regarding the safety of hypercapnia. At present, protective ventilatory strategies that involve hypercapnia are clinically acceptable, provided the clinician is primarily targeting reduced tidal stretch. There are insufficient clinical data to suggest that hypercapnia per se should be independently induced, nor do outcome data exist to support the practice of buffering hypercapnic acidosis. Rapidly advancing basic scientific investigations should better delineate the advantages, disadvantages, and optimal use of hypercapnia in ARDS.

Effect of poly(ADP ribose) synthetase inhibition on burn and smoke inhalation injury in sheep

We investigated the role of the nuclear enzyme poly (ADP ribose) synthetase (PARS) in the pathogenesis of combined burn and smoke inhalation (burn/smoke) injury in an ovine model. Eighteen sheep were operatively prepared for chronic study. PARS inhibition was achieved by treatment with a novel and selective PARS inhibitor INO-1001. The PARS inhibitor attenuated 1) lung edema formation, 2) deterioration of gas exchange, 3) changes in airway blood flow, 4) changes in airway pressure, 5) lung histological injury, and 6) systemic vascular leakage. Lipid oxidation and plasma nitrite/nitrate (stable breakdown products of nitric oxide) levels were suppressed with the use of INO-1001. We conclude that PARS inhibition attenuates various aspects of the pathophysiological response in a clinically relevant experimental model of burn/smoke inhalation injury.

Artificial lungs: a new inspiration

An estimated 16 million Americans are afflicted with some degree of chronic obstructive pulmonary disease (COPD), accounting for 100,000 deaths per year. The only current treatment for chronic irreversible pulmonary failure is lung transplantation. Since the widespread success of single and double lung transplantation in the early 1990s, demand for donor lungs has steadily outgrown the supply. Unlike dialysis, which functions as a bridge to renal transplantation, or a ventricular assist device (VAD), which serves as a bridge to cardiac transplantation, no suitable bridge to lung transplantation exists. The current methods for supporting patients with lung disease, however, are not adequate or efficient enough to act as a bridge to transplantation. Although occasionally successful as a bridge to transplant, ECMO requires multiple transfusions and is complex, labor-intensive, time-limited, costly, non-ambulatory and prone to infection. Intravenacaval devices, such as the intravascular oxygenator (IVOX) and the intravenous membrane oxygenator (IMO), are surface area limited and currently provide inadequate gas exchange to function as a bridge-to-recovery or transplant. A successful artificial lung could realize a substantial clinical impact as a bridge to lung transplantation, a support device immediately post-lung transplant, and as rescue and/or supplement to mechanical ventilation during the treatment of severe respiratory failure.

Extracorporeal membrane oxygenation for severe respiratory failure

The use of extracorporeal technology to accomplish gas exchange with or without cardiac support is based on the premise that "lung rest" facilitates repair and avoids the baso- or volutrauma of mechanical ventilator management. Extracorporeal membrane oxygenation (ECMO), a modified form of cardiopulmonary bypass, has been shown to decrease mortality of neonatal, pediatric and adult respiratory failure and is capable of total gas exchange. In neonates, over 20,638 patients have been treated with an overall survival of 77% in a population thought to have 78% mortality.