Exogenous pulmonary surfactant for the treatment of adult patients with acute respiratory distress syndrome: results of a meta-analysis

Pirfenidone to prevent fibrosis in acute respiratory distress syndrome: The PIONEER study protocol

BACKGROUND

Pulmonary fibrosis is a major complication of the Acute Respiratory Distress Syndrome (ARDS). Pirfenidone is an approved treatment for idiopathic pulmonary fibrosis. It may attenuate ARDS-related fibrosis and decrease the need for prolonged ventilation. Accordingly, we aimed to evaluate the effect of pirfenidone on ventilator-free days in patients with ARDS.

METHODS

In a multi-center, randomized, double-blind, placebo-controlled trial, we plan to randomly assign 130 adults invasively ventilated for ARDS to receive pirfenidone or placebo for up to 28 days. The primary outcome is days alive and ventilator free at 28 days. Secondary outcomes include ICU-free days, hospital free days all at 28 day, ICU mortality and hospital mortality. We will also assess fibroproliferative changes on high-resolution CT scans at ICU discharge and quality of life. Data analysis will be on an intention-to-treat basis.

DISCUSSION

The trial is ongoing and currently recruiting. It will be the first randomized controlled study to investigate whether, compared to placebo, pirfenidone increases the number of days alive and ventilator-free in patients with ARDS. Its double-blind multicenter design will provide internal validity, minimal bias, and a degree of external validity. If our hypothesis is confirmed, this treatment would justify larger trials of this intervention.

TRIAL REGISTRATION

This trial was registered on ClinicalTrials.gov with the trial identification NCT05075161.

Surfactant additives in water-based metalworking fluids lead to strong biophysical inhibition of pulmonary surfactant film

As a class of very common and important industrial liquid materials, metalworking fluids (MWFs) are easy to be vaporized into the air and cause pulmonary toxic effects. The inhaled MWF aerosols should first interact with the pulmonary surfactant (PS) film that plays an essential role in maintaining the normal respiratory mechanics and pulmonary immunology in a human body. Here, to probe any potential adverse impacts of airborne MWFs on the biophysical and physiological functions of PS film that may help achieve a deep and comprehensive understanding of the pulmonary toxicology of MWFs, a systematic study on the interaction between an animal-derived natural PS (i.e., Calsurf) film and the aerosols of water-based MWFs and their different constituents is conducted using constrained drop surfactometry (CDS) capable of closely simulating normal tidal breathing and lung-related physiological conditions in vitro. It was found that the airborne MWFs can induce strong PS inhibitions once their accumulated amount in the environment attains 0.2 mg/cm3. And their inhibitory effects are demonstrated to mainly originate from the surfactant additives such as polyethylene glycol monooleate (PEGMO) that can desorb PS film from the air/water interface via competitive interfacial adsorption, although it has normally been regarded as an eco-friendly commercial reagent.

Lung Ultrasound in Critical Care: A Narrative Review

Lung ultrasound (LUS) has become a crucial part of the investigative tools available in the management of critically ill patients, both within the intensive care unit setting and in prehospital medicine. The increase in its application, in part driven by the COVID-19 pandemic, along with the easy access and use of mobile and handheld devices, allows for immediate access to information, reducing the need for other radiological investigations. LUS allows for the rapid and accurate diagnosis and grading of respiratory pathology, optimisation of ventilation, assessment of weaning, and monitoring of the efficacy of surfactant therapies. This, however, must occur within the framework of accreditation to ensure patient safety and prevent misinterpretation and misdiagnosis. This narrative review aims to outline the current uses of LUS within the context of published protocols, associated pathologies, LUS scoring systems, and their applications, whilst exploring more novel uses.

Pulmonary drug delivery devices and nanosystems as potential treatment strategies for acute respiratory distress syndrome (ARDS)

Despite advances in drug delivery technologies, treating acute respiratory distress syndrome (ARDS) is challenging due to pathophysiological barriers such as lung injury, oedema fluid build-up, and lung inflammation. Active pharmaceutical ingredients (API) can be delivered directly to the lung site of action with the use of aerosol-based drug delivery devices, and this circumvents the hepatic first-pass effect and improves the bioavailability of drugs. This review discusses the various challenges and barriers for pulmonary drug delivery, current interventions for delivery, considerations for effective drug delivery, and the use of nanoparticle drug delivery carriers as potential strategies for delivering therapeutics in ARDS. Nanosystems have the added benefit of entrapping drugs, increase pulmonary drug bioavailability, and using biocompatible and biodegradable excipients that can facilitate targeted and/or controlled delivery. These systems provide an alternative to existing conventional systems. An effective way to deliver drugs for the treatment of ARDS can be by using colloidal systems that are aerosolized or inhaled. Drug distribution to the deeper pulmonary tissues is necessary due to the significant endothelial cell destruction that is prevalent in ARDS. The particle size of nanoparticles (<0.5 μm) makes them ideal candidates for treating ARDS as they can reach the alveoli. A look into the various potential benefits and limitations of nanosystems used for other lung disorders is also considered to indicate how they may be useful for the potential treatment of ARDS.

Life-saving effect of pulmonary surfactant in premature babies

The discovery and replacement of lung surfactant have helped increase survival rates for neonatal respiratory distress syndrome in extremely premature infants.

Effect of Surfactant Therapy on Clinical Outcomes of COVID-19 Patients With ARDS: A Systematic Review and Meta-Analysis

INTRODUCTION

The COVID-19 pandemic has brought unprecedented challenges, not only in terms of public health but also in the realm of innovative therapeutic approaches to combat the severe respiratory complications associated with the virus. The effect of surfactant therapy on reducing mortality in COVID-19 patients with acute respiratory distress syndrome (ARDS) hasn't been explored before.

METHODS

We conducted a search on PubMed, Scopus, Science Direct, and Clinicaltrials.gov to identify relevant studies, incorporating subject headings and keywords related to "Surfactant Therapy," "COVID-19," and "ARDS." Binary random effects were used to estimate the odds ratio (OR) for 28-day mortality, and continuous random effects were used to estimate the mean difference (MD) for length of hospitalization with their respective 95% confidence interval (CI). Analysis was performed with RevMan Version 5.4.1 (The Cochrane Collaboration, London, GBR).

RESULTS

We included four studies with 126 patients. Patients who received surfactant had lower odds of mortality (OR 0.53, 95% CI (0.23, 1.20), p=0.13) and a shorter duration of hospital stay (MD -5.69, 95% CI [-7.06, -4.30], p <0.00001) compared to patients who did not receive surfactant therapy. However, the findings regarding mortality were not statistically significant.

CONCLUSIONS

The COVID-19 patients with ARDS who received surfactant therapy had lower hospitalization stays and mortality rates, indicating that surfactant therapy may improve clinical outcomes in COVID-19 patients with ARDS. However, the results were not significant, and further research with more prospective studies and randomized clinical trials (RCTs) with larger sample sizes is needed to confirm these findings and assess their practical significance and generalizability.

Surfactant replacement therapy as promising treatment for COVID-19: an updated narrative review

Patients with COVID-19 exhibit similar symptoms to neonatal respiratory distress syndrome. SARS-CoV-2 spike protein has been shown to target alveolar type 2 lung cells which synthesize and secrete endogenous surfactants leading to acute respiratory distress syndrome in some patients. This was proven by post-mortem histopathological findings revealing desquamated alveolar type 2 cells. Surfactant use in patients with COVID-19 respiratory distress syndrome results in marked improvement in respiratory parameters but not mortality which needs further clinical trials comparing surfactant formulas and modes of administration to decrease the mortality. In addition, surfactants could be a promising vehicle for specific drug delivery as a liposomal carrier, which requires more and more challenging efforts. In this review, we highlight the current reviews and two clinical trials on exogenous surfactant therapy in COVID-19-associated respiratory distress in adults, and how surfactant could be a promising drug to help fight the COVID-19 infection.

Pharmacologic therapies of ARDS: From natural herb to nanomedicine

Acute respiratory distress syndrome (ARDS) is a common critical illness in respiratory care units with a huge public health burden. Despite tremendous advances in the prevention and treatment of ARDS, it remains the main cause of intensive care unit (ICU) management, and the mortality rate of ARDS remains unacceptably high. The poor performance of ARDS is closely related to its heterogeneous clinical syndrome caused by complicated pathophysiology. Based on the different pathophysiology phases, drugs, protective mechanical ventilation, conservative fluid therapy, and other treatment have been developed to serve as the ARDS therapeutic methods. In recent years, there has been a rapid development in nanomedicine, in which nanoparticles as drug delivery vehicles have been extensively studied in the treatment of ARDS. This study provides an overview of pharmacologic therapies for ARDS, including conventional drugs, natural medicine therapy, and nanomedicine. Particularly, we discuss the unique mechanism and strength of nanomedicine which may provide great promises in treating ARDS in the future.

Mechanistic Understanding of Lung Inflammation: Recent Advances and Emerging Techniques

Acute respiratory distress syndrome (ARDS) is a life-threatening lung injury characterized by an acute inflammatory response in the lung parenchyma. Hence, it is considered as the most appropriate clinical syndrome to study pathogenic mechanisms of lung inflammation. ARDS is associated with increased morbidity and mortality in the intensive care unit (ICU), while no effective pharmacological treatment exists. It is very important therefore to fully characterize the underlying pathobiology and the related mechanisms, in order to develop novel therapeutic approaches. In vivo and in vitro models are important pre-clinical tools in biological and medical research in the mechanistic and pathological understanding of the majority of diseases. In this review, we will present data from selected experimental models of lung injury/acute lung inflammation, which have been based on clinical disorders that can lead to the development of ARDS and related inflammatory lung processes in humans, including ventilation-induced lung injury (VILI), sepsis, ischemia/reperfusion, smoke, acid aspiration, radiation, transfusion-related acute lung injury (TRALI), influenza, Streptococcus (S.) pneumoniae and coronaviruses infection. Data from the corresponding clinical conditions will also be presented. The mechanisms related to lung inflammation that will be covered are oxidative stress, neutrophil extracellular traps, mitogen-activated protein kinase (MAPK) pathways, surfactant, and water and ion channels. Finally, we will present a brief overview of emerging techniques in the field of omics research that have been applied to ARDS research, encompassing genomics, transcriptomics, proteomics, and metabolomics, which may recognize factors to help stratify ICU patients at risk, predict their prognosis, and possibly, serve as more specific therapeutic targets.

The ultrastructural heterogeneity of lung surfactant revealed by serial section electron tomography: Insights into the 3D architecture of human tubular myelin

Weibel's hypothetical 3D model in 1966 provided first ultrastructural details into tubular myelin (TM), a unique, complex surfactant subtype found in the hypophase of the alveolar lining layer. Although initial descriptions by electron microscopy (EM) were already published in the 1950s, a uniform morphological differentiation from other intraalveolar surfactant subtypes is still missing and potential structure-function relationships remain enigmatic. Technical developments in volume EM methods now allow a more detailed reinvestigation. To address unanswered ultrastructural questions, we analyzed ultrathin sections of humanized SP-A1/SP-A2 co-expressing mouse as well as human lung samples by conventional transmission EM. We combined these 2D information with 3D analysis of single- and dual-axis electron tomography of serial sections for high z-resolution (in a range of a few nm) and extended volumes of up to 1 µm total z-information. This study reveals that TM constitutes a heterogeneous surfactant organization mainly comprised of distorted parallel membrane planes with local intersections, which are distributed all over the TM substructure. These intersecting membrane planes form, among other various polygons, the well-known 2D "lattice", respectively 3D quadratic tubules, which in many analyzed spots of human alveoli appear to be less abundant than also observed non-concentric 3D lamellae. The additional application of serial section electron tomography to conventional transmission EM demonstrates a high heterogeneity of TM membrane networks, which indicates dynamic transformations between its substructures. Our method provides an ideal basis for further in and ex vivo structural analyses of surfactant under various conditions at nanometer scale.

Spontaneous evolution of equilibrium morphology in phospholipid-cholesterol monolayers

Competition between intradomain electrostatic repulsions and interdomain line tension leads to domain shape transitions in phase-separating lipid monolayers. The question remains if these morphologies are energy minima or are kinetically trapped metastable states. We show the reversible evolution of uniform width stripe domains from polydisperse semicircular domains in monolayers of dipalmitoylphosphatidylcholine (DPPC), hexadecanol (HD) or palmitic acid (PA), and dihydrocholesterol (DChol). The initial semicircular domains grow at a fixed 2:1 DPPC:HD (or PA) stoichiometry, depleting the liquid phase of HD, leaving behind a liquid enriched in DPPC and DChol. At higher surface pressures, the remaining DPPC precipitates onto existing domains, decreasing the ratio of line tension to the square of the dipole density difference, λ/μ2. Theory predicts that, as λ/μ2 decreases, circular domains reversibly transform to uniform width stripes as the minimum energy structure. Measuring the stripe width provides the first estimates of λ/μ2 at liquid condensed-liquid expanded phase coexistence.

Surfactant-based therapy against COVID-19: A review

The coronavirus disease 2019 (COVID-19) has led to serious health and economic damage to all over the world, and it still remains unstoppable. The SARS-CoV-2, by using its S-glycoprotein, binds with an angiotensin-converting enzyme 2 receptor, mostly present in alveolar epithelial type II cells. Eventually pulmonary surfactant depletion occurs. The pulmonary surfactant is necessary for maintaining the natural immunity as well as the surface tension reduction within the lung alveoli during the expiration. Its insufficiency results in the reduction of blood oxygenation, poor pulmonary regeneration, lung fibrosis, and finally the respiratory system collapses. Exogenous surfactants have previously shown great promise in the treatment of infant respiratory distress syndrome, and they may also aid in the healing of damaged alveolar cells and the prevention of respiratory failure. Surfactant based therapy has been advised for the prevention of COVID-19, and the trials have begun around the world. Furthermore, greater research on the timing, dose, and the distribution of surfactant to the COVID-19 patients is required before this technique can be implemented in clinical practice.

The Role of Pulmonary Surfactants in the Treatment of Acute Respiratory Distress Syndrome in COVID-19

Lung alveolar type-II (AT-II) cells produce pulmonary surfactant (PS), consisting of proteins and lipids. The lipids in PS are primarily responsible for reducing the air-fluid surface tension inside the alveoli of the lungs and to prevent atelectasis. The proteins are of two types: hydrophilic and hydrophobic. Hydrophilic surfactants are primarily responsible for opsonisation, thereby protecting the lungs from microbial and environmental contaminants. Hydrophobic surfactants are primarily responsible for respiratory function. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) enters the lungs through ACE-2 receptors on lungs and replicates in AT-II cells leading to the etiology of Coronavirus disease - 2019 (COVID-19). The SARS-CoV-2 virus damages the AT-II cells and results in decreased production of PS. The clinical symptoms of acute respiratory distress syndrome (ARDS) in COVID-19 patients are like those of neonatal respiratory distress syndrome (NRDS). The PS treatment is first-line treatment option for NRDS and found to be well tolerated in ARDS patients with inconclusive efficacy. Over the past 70°years, a lot of research is underway to produce natural/synthetic PS and developing systems for delivering PS directly to the lungs, in addition to finding the association between PS levels and respiratory illnesses. In the present COVID-19 pandemic situation, the scientific community all over the world is searching for the effective therapeutic options to improve the clinical outcomes. With a strong scientific and evidence-based background on role of PS in lung homeostasis and infection, few clinical trials were initiated to evaluate the functions of PS in COVID-19. Here, we connect the data on PS with reference to pulmonary physiology and infection with its possible therapeutic benefit in COVID-19 patients.

Emerging Advances of Nanotechnology in Drug and Vaccine Delivery against Viral Associated Respiratory Infectious Diseases (VARID)

Viral-associated respiratory infectious diseases are one of the most prominent subsets of respiratory failures, known as viral respiratory infections (VRI). VRIs are proceeded by an infection caused by viruses infecting the respiratory system. For the past 100 years, viral associated respiratory epidemics have been the most common cause of infectious disease worldwide. Due to several drawbacks of the current anti-viral treatments, such as drug resistance generation and non-targeting of viral proteins, the development of novel nanotherapeutic or nano-vaccine strategies can be considered essential. Due to their specific physical and biological properties, nanoparticles hold promising opportunities for both anti-viral treatments and vaccines against viral infections. Besides the specific physiological properties of the respiratory system, there is a significant demand for utilizing nano-designs in the production of vaccines or antiviral agents for airway-localized administration. SARS-CoV-2, as an immediate example of respiratory viruses, is an enveloped, positive-sense, single-stranded RNA virus belonging to the coronaviridae family. COVID-19 can lead to acute respiratory distress syndrome, similarly to other members of the coronaviridae. Hence, reviewing the current and past emerging nanotechnology-based medications on similar respiratory viral diseases can identify pathways towards generating novel SARS-CoV-2 nanotherapeutics and/or nano-vaccines.

Beneficial effects of inhaled surfactant in patients with COVID-19-associated acute respiratory distress syndrome

Background

We have investigated the use of nebulized surfactant as a potential therapeutic option for the patients with coronavirus disease 2019 (COVID-19)-associated acute respiratory distress syndrome (ARDS) undergoing non-invasive ventilation.

Methods

The patients were divided into 2 groups: surfactant (n = 33) and control (n = 32). The subjects in the surfactant group received the inhaled surfactant at daily dose of 150–300 mg. The oxygenation parameters and several clinical outcomes were analyzed.

Results

On the 5 day of therapy, PaO₂/FiO₂ improved significantly in the surfactant group compared to the control group (184 (155–212) mmHg vs 150 (91–173) mmHg, p = 0.02). The inhaled surfactant significantly reduced the need for transfer of patients to intensive care units (24.2% vs 46.9%, p = 0.05) and invasive mechanical ventilation (18.2% vs 40.6%, p = 0.04). Even more, the nebulized surfactant shortened the length of non-invasive ventilation (7 (3–13) days vs 11 (5–22) days, p = 0.02) and time spent in hospital (18 (16–27) days vs 26 (21–31) days, p = 0.003) in patients suffering from COVID-19-linked ARDS.

Conclusions

Our preliminary data provided indications that inhaled surfactant therapy may represent a promising option for patients with COVID-19-associated ARDS. However, larger clinical trials are crucially needed.

Exogenous pulmonary surfactant: A review focused on adjunctive therapy for severe acute respiratory syndrome coronavirus 2 including SP-A and SP-D as added clinical marker

Type I and type II pneumocytes are two forms of epithelial cells found lining the alveoli in the lungs. Type II pneumocytes exclusively secrete 'pulmonary surfactants,' a lipoprotein complex made up of 90% lipids (mainly phospholipids) and 10% surfactant proteins (SP-A, SP-B, SP-C, and SP-D). Respiratory diseases such as influenza, severe acute respiratory syndrome coronavirus infection, and severe acute respiratory syndrome coronavirus 2 infection are reported to preferentially attack type II pneumocytes of the lungs. After viral invasion, consequent viral propagation and destruction of type II pneumocytes causes altered surfactant production, resulting in dyspnea and acute respiratory distress syndrome in patients with coronavirus disease 2019. Exogenous animal-derived or synthetic pulmonary surfactant therapy has already shown immense success in the treatment of neonatal respiratory distress syndrome and has the potential to contribute efficiently toward repair of damaged alveoli and preventing severe acute respiratory syndrome coronavirus 2-associated respiratory failure. Furthermore, early detection of surfactant collectins (SP-A and SP-D) in the circulatory system can be a significant clinical marker for disease prognosis in the near future.

The Effect of Exogenous Surfactant on Moderate and Severe Stages of COVID-19 Induced ARDS: the Pilot Study of a Clinical Trial

COVID-19 pandemic has created a global health challenge. Many pharmaceuticals have been repurposed as potential treatments, though many have not been promising. Due to the inflammatory and destructive effects of the virus on alveolar cells, the effect of exogenous surfactant was assessed as a potential treatment of lung dysfunction in COVID-19 patients. In this pilot study of the clinical trial, 49 patients aged 35-80 years with COVID-19 admitted in ICU entered the study (22 patients intubated and 23 had face masks; 4 patients in the control arm). The treatment arm patients received two consecutive doses of surfactant. P/F ratio (based on serial blood gas analyses before and 12 hours after 2 doses of surfactant) and also, clinical outcomes were assessed.in COVID-19 adult patients, surfactant significantly improved pulmonary P/F ratio both in intubated and face mask COVID-19 patients (increasing from 119.2 ± 51.7 to 179.4 ± 115.5). The rate of extubation was much better than similar country-wide studies. Surfactant significantly alleviates the respiratory status in moderate to severe COVID-19 ARDS with two consecutive 100 mg doses of surfactant (with 6 hours' interval) though previous studies have been controversial, regarding the effect of surfactant in general forms of ARDS. Higher doses might have better effects, mandating more trials.

Impact of synthetic surfactant CHF5633 with SP-B and SP-C analogues on lung function and inflammation in rabbit model of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is associated with diffuse inflammation, alveolar epithelial damage, and leakage of plasma proteins into the alveolar space, which together contribute to inactivation of pulmonary surfactant and respiratory failure. Exogenous surfactant delivery is therefore considered to hold potential for ARDS treatment, but clinical trials with natural derived surfactant or synthetic surfactant containing a surfactant protein C (SP-C) analogue have been negative. Synthetic surfactant CHF5633, containing analogues of SP-B and SP-C, may be effective against ARDS. The aim here was to compare treatment effects of CHF5633 and animal-derived surfactant poractant alfa in animal model of ARDS. ARDS was induced in adult New Zealand rabbits by mild lung lavages followed by injurious ventilation until respiratory failure (P/F ratio <26.7 kPa). The animals were then treated with intratracheal bolus of 200 mg/kg CHF5633 or poractant alfa (Curosurf® ), or air as control. The animals were subsequently ventilated for an additional 4 hr and respiratory parameters were recorded regularly. Postmortem, histological analysis, degree of lung edema, and levels of the cytokines TNFα, IL-6, and IL-8 in lung homogenates were evaluated. Both surfactant preparations improved lung function, reduced the levels of pro-inflammatory cytokines, and degree of lung edema to very similar degrees versus the controls. No significant differences in any of the analyzed parameters were observed between the CHF5633- and poractant alfa-treated groups. This study indicates that single dose of CHF5633 improves lung function and attenuates inflammation as effectively as poractant alfa in experimental ARDS caused by injurious ventilation.

The COVID-19 pandemic: a target for surfactant therapy?

INTRODUCTION

The dramatic impact of COVID-19 on humans worldwide has initiated an extraordinary search for effective treatment approaches. One of these is the administration of exogenous surfactant, which is being tested in ongoing clinical trials.

AREAS COVERED

Exogenous surfactant is a life-saving treatment for premature infants with neonatal respiratory distress syndrome. This treatment has also been tested for acute respiratory distress syndrome (ARDS) with limited success possibly due to the complexity of that syndrome. The 60-year history of successes and failures associated with surfactant therapy distinguishes it from many other treatments currently being tested for COVID-19 and provides the opportunity to discuss the factors that may influence the success of this therapy.

EXPERT OPINION

Clinical data provide a strong rationale for using exogenous surfactant in COVID-19 patients. Success of this therapy may be influenced by the mechanical ventilation strategy, the timing of treatment, the doses delivered, the method of delivery and the preparations utilized. In addition, future development of enhanced preparations may improve this treatment approach. Overall, results from ongoing trials may not only provide data to indicate if this therapy is effective for COVID-19 patients, but also lead to further scientific understanding and improved treatment strategies.

Co-aerosolized Pulmonary Surfactant and Ambroxol for COVID-19 ARDS Intervention: What Are We Waiting for?

After more than 225 days of the first reports of the novel coronavirus from China, COVID-19 pandemic is still on surge. The search for an effective and efficient therapeutic and pharmaceutical intervention is as important and urgent now as it was on Day 1. Majority of the efforts in this direction are toward finding small molecule interventions via repurposing or redirecting the therapeutic approaches. This hypothesis proposes a physical intervention approach directed toward rescuing the complex lung pathology observed in COVID-19 related acute respiratory distress syndrome (CARDS). The loss of content as well as the synthesis and turnover of the surfactant in ARDS has been termed as a "collateral damage." A synergistic, early stage, cost-effective, pharmaceutically viable, safe, and immediately available solution is hence required. The effectiveness of exogenous surfactant treatment in ARDS has been marred with several limitations as pointed out in various clinical trials and require revised protocols related to surfactant dose and mode of delivery. This hypothesis proposes aerosolized surfactant delivery taking the optimal dosing and coating costs into account along with co-delivery of ambroxol to provide synergistic benefits. Ambroxol is reported to have anti-inflammatory, -oxidant, -viral, and -bacterial activities and has a direct impact on the production and secretion of the surfactant from the alveolar Type 2 cells. If aerosolized, atomized, or nebulized in the form of ambroxol-loaded phospholipid nanovesicles at the early stages of ARDS, depleted surfactant levels may be reinstated and surfactant turnover can be initiated and maintained. The ability to deliver both the components in aerosolized-nebulized form may have a huge impact on alleviating the healthcare burden in low resource settings where the availability of ventilators is limited. In conclusion, the surfactant-ambroxol co-aerosolized intervention approach hypothesized here has implications reaching to clinical and pharmaceutical translation worldwide.

Acute Respiratory Distress Syndrome: Etiology, Pathogenesis, and Summary on Management

The acute respiratory distress syndrome (ARDS) has multiple causes and is characterized by acute lung inflammation and increased pulmonary vascular permeability, leading to hypoxemic respiratory failure and bilateral pulmonary radiographic opacities. The acute respiratory distress syndrome is associated with substantial morbidity and mortality, and effective treatment strategies are limited. This review presents the current state of the literature regarding the etiology, pathogenesis, and management strategies for ARDS.

Angiotensin II type 2 receptor agonist Compound 21 attenuates pulmonary inflammation in a model of acute lung injury

Purpose

Although the role of the angiotensin II type 2 (AT2) receptor in acute lung injury is not yet completely understood, a protective role of this receptor subtype has been suggested. We hypothesized that, in a rodent model of acute lung injury, stimulation of the AT2 receptor with the direct agonist Compound 21 (C21) might have a beneficial effect on pulmonary inflammation and might improve pulmonary gas exchange.

Materials and methods

Male adult rats were divided into a treatment group that received pulmonary lavage followed by mechanical ventilation (LAV, n=9), a group receiving pulmonary lavage, mechanical ventilation, and direct stimulation of the AT2 receptor with C21 (LAV+C21, n=9), and a control group that received mechanical ventilation only (control, n=9). Arterial blood gas analysis was performed every 30 min throughout the 240-min observation period. Lung tissue and plasma samples were obtained at 240 min after the start of mechanical ventilation. Protein content and surface activity of bronchoalveolar lavage fluid were assessed and the wet/dry-weight ratio of lungs was determined. Transcriptional and translational regulation of pro- and antiinflammatory cytokines IL-1β, tumor necrosis factor-alpha, IL-6, IL-10, and IL-4 was determined in lungs and in plasma.

Results

Pulmonary lavage led to a significant impairment of gas exchange, the formation of lung edema, and the induction of pulmonary inflammation. Protein content of lavage fluid was increased and contained washed-out surfactant. Direct AT2 receptor stimulation with C21 led to a significant inhibition of tumor necrosis factor-alpha and IL-6 expressions in the lungs, whereas the expressions of IL-1, IL-10, and IL-4 remained unchanged. During the 240-min observation period, AT2 receptor stimulation did not improve pulmonary gas exchange or lung edema.

Conclusion

In this rodent model of acute lung injury after repeated pulmonary lavage, AT2 receptor stimulation attenuates pulmonary inflammation but does not improve gas exchange.

ARDS: challenges in patient care and frontiers in research

This review discusses the clinical challenges associated with ventilatory support and pharmacological interventions in patients with acute respiratory distress syndrome (ARDS). In addition, it discusses current scientific challenges facing researchers when planning and performing trials of ventilatory support or pharmacological interventions in these patients.

Noninvasive mechanical ventilation is used in some patients with ARDS. When intubated and mechanically ventilated, ARDS patients should be ventilated with low tidal volumes. A plateau pressure <30 cmH₂O is recommended in all patients. It is suggested that a plateau pressure <15 cmH₂O should be considered safe. Patient with moderate and severe ARDS should receive higher levels of positive end-expiratory pressure (PEEP). Rescue therapies include prone position and neuromuscular blocking agents. Extracorporeal support for decapneisation and oxygenation should only be considered when lung-protective ventilation is no longer possible, or in cases of refractory hypoxaemia, respectively. Tracheotomy is only recommended when prolonged mechanical ventilation is expected.

Of all tested pharmacological interventions for ARDS, only treatment with steroids is considered to have benefit.

Proper identification of phenotypes, known to respond differently to specific interventions, is increasingly considered important for clinical trials of interventions for ARDS. Such phenotypes could be defined based on clinical parameters, such as the arterial oxygen tension/inspiratory oxygen fraction ratio, but biological marker profiles could be more promising.

Treatment of ARDS is mainly through the prevention of ventilation-induced lung injuryhttp://ow.ly/DeJC30hGWfi

Multiple Organ Dysfunction: The Defining Syndrome of Sepsis

BACKGROUND

Sepsis as a process has been recognized since the time of the Ancient Greeks. The concept has evolved recently to reflect a disease process of a severe, systemic response to infection. Acute, life-threatening but potentially reversible organ dysfunction is its hallmark, and unresolving organ dysfunction is the dominant cause of death in critical illness. Its evolution, persistence, and resolution reflect a complex interplay of factors originating in the initial inciting insult, the innate immune and metabolic response of the host, and the beneficial and harmful consequences of intensive care unit (ICU) supportive care.

DISCUSSION

We describe the common clinical manifestations of the six prototypic organ system dysfunction syndromes of severe sepsis and review the associated epidemiology and suspected pathophysiology.

Inhalation therapies in acute respiratory distress syndrome

The defining features of acute respiratory distress syndrome (ARDS) are an excessive inflammatory respiratory response associated with high morbidity and mortality. Treatment consists mainly of measures to avoid worsening lung injury and cannot reverse the underlying pathophysiological process. New pharmacological agents have shown promising results in preclinical studies; however, they have not been successfully translated to patients with ARDS. The lack of effective therapeutic interventions has resulted in a recent interest in strategies to prevent ARDS with treatments delivering medications directly to the lungs by inhalation and nebulization, hopefully minimizing systemic adverse events. We analyzed the effect of different aerosolized drugs such as bronchodilators, corticosteroids, pulmonary vasodilators, anticoagulants, mucolytics and surfactant. New therapeutic strategies and ongoing trials using carbon monoxide (CO) and AP301 peptide are also briefly reviewed.

Surfactant inhibits ATP-induced release of interleukin-1β via nicotinic acetylcholine receptors

Interleukin (IL)-1β is a potent pro-inflammatory cytokine of innate immunity involved in host defense. High systemic IL-1β levels, however, cause life-threatening inflammatory diseases, including systemic inflammatory response syndrome. In response to various danger signals, the pro-form of IL-1β is synthesized and stays in the cytoplasm unless a second signal, such as extracellular ATP, activates the inflammasome, which enables processing and release of mature IL-1β. As pulmonary surfactant is known for its anti-inflammatory properties, we hypothesize that surfactant inhibits ATP-induced release of IL-1β. Lipopolysaccharide-primed monocytic U937 cells were stimulated with an ATP analog in the presence of natural or synthetic surfactant composed of recombinant surfactant protein (rSP)-C, palmitoylphosphatidylglycerol, and dipalmitoylphosphatidylcholine (DPPC). Both surfactant preparations dose-dependently inhibited IL-1β release from U937 cells. DPPC was the active constituent of surfactant, whereas rSP-C and palmitoylphosphatidylglycerol were inactive. DPPC was also effective in primary mononuclear leukocytes isolated from human blood. Experiments with nicotinic antagonists, siRNA technology, and patch-clamp experiments suggested that stimulation of nicotinic acetylcholine receptors (nAChRs) containing subunit α9 results in a complete inhibition of the ion channel function of ATP receptor, P2X7. In conclusion, the surfactant constituent, DPPC, efficiently inhibits ATP-induced inflammasome activation and maturation of IL-1β in human monocytes by a mechanism involving nAChRs.

Clinical effects of pulmonary surfactant in combination with nasal continuous positive airway pressure therapy on neonatal respiratory distress syndrome

OBJECTIVE

To analyze the therapeutic effect of pulmonary surfactant (PS) in combination with nasal continuous positive airway pressure (NCPAP) therapy on neonatal respiratory distress syndrome (NRDS).

METHODOLOGY

Forty-nine neonates who were diagnosed as NRDS and admitted in our hospital from May 2014 to June 2015 were selected and divided into an observation group and a control group. The observation group was treated with PS and NCPAP. The control group was treated only with NCPAP. The clinical symptoms, pulmonary X-ray, arterial partial pressure of oxygen (PaO2) and prognosis of the two groups were observed.

RESULTS

Twelve hours after treatment, the partial pressure of carbon dioxide and oxygenation index decreased significantly (P<0.05), and PaO2 and ratio of arterial/pulmonary oxygen partial pressures increased significantly (P<0.05). Pulmonary X-ray examination showed that 78.3% of the observation group and 53.8% of the control group were relieved 12-24 hour after treatment, between which the difference was statistically significant (P<0.05). The improvement rate of the observation group was significantly higher than that of the control group (82.6% vs. 57.7%, P<0.05), the incidence of complications was significantly lower in the observation group (P<0.05), and the average length of stay in the observation group was significantly shorter (P<0.05).

CONCLUSION

Both methods effectively treated NRDS, but PS in combination with NCPAP better improved oxygenation, reduced mortality and incidence of complications.

Restoring pulmonary surfactant membranes and films at the respiratory surface

Pulmonary surfactant is a complex of lipids and proteins assembled and secreted by the alveolar epithelium into the thin layer of fluid coating the respiratory surface of lungs. There, surfactant forms interfacial films at the air-water interface, reducing dramatically surface tension and thus stabilizing the air-exposed interface to prevent alveolar collapse along respiratory mechanics. The absence or deficiency of surfactant produces severe lung pathologies. This review describes some of the most important surfactant-related pathologies, which are a cause of high morbidity and mortality in neonates and adults. The review also updates current therapeutic approaches pursuing restoration of surfactant operative films in diseased lungs, mainly through supplementation with exogenous clinical surfactant preparations. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Fifty Years of Research in ARDS. Is Acute Respiratory Distress Syndrome a Preventable Disease?

Despite significant advances in our understanding and management of patients with acute respiratory distress syndrome (ARDS), the morbidity and mortality from ARDS remains high. Given the limited number of effective treatments for established ARDS, the strategic focus of ARDS research has shifted toward identifying patients with or at high risk of ARDS early in the course of the underlying illness, when strategies to reduce the development and progression of ARDS and associated organ failures can be systematically evaluated. In this review, we summarize the rationale, current evidence, and future directions in ARDS prevention.

Accumulation and cellular localization of nanoparticles in an ex vivo model of acute lung injury

BACKGROUND

The benefit of nanomedicine in mitigating acute lung injury (ALI) is currently unknown. Therefore, we introduced the generation IV polyamidoamine dendrimers with neutral surface property (dendrimer) into our established ex vivo animal model and sought to determine their biodistribution to define their cellular uptake profile and to evaluate their potential as a drug delivery candidate for the treatment of ischemia-reperfusion-induced ALI.

METHODS

Eight rabbit heart-lung blocks were harvested and exposed to 18 h of cold ischemia. The heart-lung blocks were then reperfused with rabbit donor blood. Dendrimer was conjugated to fluorescein isothiocyanate (D-FITC) for localization and quantification studies. D-FITC (30 mg or 150 mg) was injected into the bypass circuit and baseline, 1- and 2-h tissue samples were obtained to determine percent uptake. Low (10×) and high (40×) magnification images were obtained using confocal microscopy to confirm the accumulation and to determine the cellular targets of the dendrimer.

RESULTS

Four heart-lung blocks were exposed to 30 mg and four to 150 mg of D-FITC. After adjusting for dry weight, the mean uptake in the 30 and 150 mg samples after 2 h of reperfusion were 0.79 ± 0.16% and 0.39 ± 0.22% of perfused doses, respectively. Confocal imaging demonstrated dendrimer uptake in epithelial cells and macrophages.

CONCLUSIONS

Fluorescently tagged dendrimers demonstrated injury-dependent tissue accumulation in a variety of different cell types. This unique approach will allow conjugation to and delivery of multiple agents with the potential of mitigating ALI injury while avoiding systemic toxicity.

Failure to Improve the Oxygenation Index Is a Useful Predictor of Therapy Failure in Acute Respiratory Distress Syndrome Clinical Trials

OBJECTIVE

Acute respiratory distress syndrome trials powered for mortality require significant resources, limiting the number of evaluable therapies. Validation of intermediate endpoints would enhance the feasibility of testing novel acute respiratory distress syndrome therapies in pilot studies and potentially reduce the frequency of failed large clinical trials. We sought to determine whether a change in the oxygenation index over the first 7 days of acute respiratory distress syndrome could discriminate between therapies likely or unlikely to show benefit in larger clinical trials.

DESIGN

A derivation cohort from three acute respiratory distress syndrome studies was used to estimate the 7-day change in oxygenation index. Receiver operating characteristic curves were used to calculate optimal thresholds and predictability of the change in oxygenation index for 28-day mortality and ventilator-free days. The thresholds were then validated in two cohorts. Then, for each individual acute respiratory distress syndrome study, the threshold 7-day oxygenation index change was tested as an outcome measure and compared with mortality and ventilator-free days as reported in the original study.

SETTING

Medical ICUs.

PATIENTS

Acute respiratory distress syndrome patients.

INTERVENTIONS

Various.

MEASUREMENTS AND MAIN RESULTS

Change in oxygenation index, 28-day mortality, and ventilator-free days. In the derivation cohort, the mean 7-day oxygenation index improved by 4.2 (± 11.7) in 28-day survivors compared with an increase of 2.4 (± 11.6) in 28-day nonsurvivors (p < 0.001). The mean 7-day oxygenation index decreased by 5.9 (± 8.4) in patients with more than 14 ventilator-free days, compared with a decrease of 1.9 (± 12.4) among those with less than 14 ventilator-free days (p = 0.001). The optimal 7-day oxygenation index threshold for predicting mortality was an increase of 1.71 and for predicting less than 14 ventilator-free days, a decrease of 2.34. When used as a surrogate endpoint, the optimal 7-day oxygenation index change closely approximated mortality and ventilator-free day outcomes in three Acute Respiratory Distress Syndrome Network studies used for the derivation cohort and a distinct study used for validation. The change in oxygenation index was a poor predictor of individual patient outcome.

CONCLUSIONS

Failure to meet a threshold improvement in the oxygenation index over the first 7 days of therapy can be used to identify therapies unlikely to succeed in subsequent trials powered for mortality and ventilator-free days. By reducing trial time and costs, use of the 7-day oxygenation index change as an intermediate endpoint could increase the number of clinical trials of promising therapies for acute respiratory distress syndrome and reduce the number of large-scale trials of therapies unlikely to be of benefit.

The Role of Surfactant in Lung Disease and Host Defense against Pulmonary Infections

Pulmonary surfactant is essential for life as it lines the alveoli to lower surface tension, thereby preventing atelectasis during breathing. Surfactant is enriched with a relatively unique phospholipid, termed dipalmitoylphosphatidylcholine, and four surfactant-associated proteins, SP-A, SP-B, SP-C, and SP-D. The hydrophobic proteins, SP-B and SP-C, together with dipalmitoylphosphatidylcholine, confer surface tension-lowering properties to the material. The more hydrophilic surfactant components, SP-A and SP-D, participate in pulmonary host defense and modify immune responses. Specifically, SP-A and SP-D bind and partake in the clearance of a variety of bacterial, fungal, and viral pathogens and can dampen antigen-induced immune function of effector cells. Emerging data also show immunosuppressive actions of some surfactant-associated lipids, such as phosphatidylglycerol. Conversely, microbial pathogens in preclinical models impair surfactant synthesis and secretion, and microbial proteinases degrade surfactant-associated proteins. Deficiencies of surfactant components are classically observed in the neonatal respiratory distress syndrome, where surfactant replacement therapies have been the mainstay of treatment. However, functional or compositional deficiencies of surfactant are also observed in a variety of acute and chronic lung disorders. Increased surfactant is seen in pulmonary alveolar proteinosis, a disorder characterized by a functional deficiency of the granulocyte-macrophage colony-stimulating factor receptor or development of granulocyte-macrophage colony-stimulating factor antibodies. Genetic polymorphisms of some surfactant proteins such as SP-C are linked to interstitial pulmonary fibrosis. Here, we briefly review the composition, antimicrobial properties, and relevance of pulmonary surfactant to lung disorders and present its therapeutic implications.

Acute respiratory distress syndrome on the intensive care unit

Acute respiratory distress syndrome is a life-threatening condition that is common in critically ill patients. Historically, diagnosis has been difficult and prognosis has been poor, but the Berlin definition and developments in medical therapies provide promise that we can improve outcomes for these patients in the future.

Emerging drugs for acute lung injury

INTRODUCTION

Acute respiratory distress syndromes (ARDS) are devastating disorders of overwhelming pulmonary inflammation and hypoxemia, resulting in high morbidity and mortality.

AREAS COVERED

The main pharmacological treatment strategies have focused on the attempted inhibition of excessive inflammation or the manipulation of the resulting physiological derangement causing respiratory failure. Additionally, such interventions may allow reduced occurence mechanical ventilation injury. Despite promising preclinical and small clinical studies, almost all therapies have been shown to be unsuccessful in large-scale randomized controlled trials. The evidence for pharmacological treatment for ARDS is reviewed. Potential future treatments are also presented.

EXPERT OPINION

We suggest for future clinical trials addressing prevention and early intervention to attenuate lung injury and progression to respiratory failure.

Pharmacological therapies for acute respiratory distress syndrome

PURPOSE OF REVIEW

Despite recent advances in the management of patients with acute respiratory distress syndrome (ARDS) by using protective ventilator strategies, the mortality rate of ARDS remains high. The complexity of the pathogenesis and the heterogeneity of coexisting diseases in patients with ARDS require critical care physicians and researchers to search for multiple therapeutic approaches in order to further improve patient outcome. This review article therefore focuses on the recent studies in the field of pharmacological intervention in ARDS.

RECENT FINDINGS

A number of approaches for pharmacological intervention have been evaluated in patients with ARDS, but most of them failed to reduce mortality or improve outcomes despite some promising observations seen in preclinical studies. Prior methods such as nitric oxide inhalation, neuromuscular blocking agents and corticosteroids may still have a place in the treatment, while novel therapeutic approaches including the use of angiotensin-converting enzyme inhibitors, statins and stem cells are currently under investigation.

SUMMARY

Overall, there is no proven pharmacological therapy in ARDS, but some pharmacological interventions were associated with beneficial effects in certain subgroups of patients depending on the cause, underlying diseases, the concurrent supportive therapies and timing. Further clinical trials are warranted to assess multiple outcome measurement of the promising pharmacological interventions in selected patients with ARDS.

Biomarkers in acute respiratory distress syndrome

PURPOSE OF REVIEW

The article provides an overview of efforts to identify and validate biomarkers in acute respiratory distress syndrome (ARDS) and a discussion of the challenges confronting researchers in this area.

RECENT FINDINGS

Although various putative biomarkers have been investigated in ARDS, the data have been largely disappointing and the 'troponin' of ARDS remains elusive. Establishing a relationship between measurable biological processes and clinical outcomes is vital to advancing clinical trials in ARDS and expanding our arsenal of treatments for this complex syndrome.

SUMMARY

This article summarizes the current status of ARDS biomarker research and provides a framework for future investigation.

Effects of interventions on survival in acute respiratory distress syndrome: an umbrella review of 159 published randomized trials and 29 meta-analyses

PURPOSE

Multiple interventions have been tested in acute respiratory distress syndrome (ARDS). We examined the entire agenda of published randomized controlled trials (RCTs) in ARDS that reported on mortality and of respective meta-analyses.

METHODS

We searched PubMed, the Cochrane Library, and Web of Knowledge until July 2013. We included RCTs in ARDS published in English. We excluded trials of newborns and children; and those on short-term interventions, ARDS prevention, or post-traumatic lung injury. We also reviewed all meta-analyses of RCTs in this field that addressed mortality. Treatment modalities were grouped in five categories: mechanical ventilation strategies and respiratory care, enteral or parenteral therapies, inhaled/intratracheal medications, nutritional support, and hemodynamic monitoring.

RESULTS

We identified 159 published RCTs of which 93 had overall mortality reported (n = 20,671 patients)--44 trials (14,426 patients) reported mortality as a primary outcome. A statistically significant survival benefit was observed in eight trials (seven interventions) and two trials reported an adverse effect on survival. Among RCTs with more than 50 deaths in at least one treatment arm (n = 21), two showed a statistically significant mortality benefit of the intervention (lower tidal volumes and prone positioning), one showed a statistically significant mortality benefit only in adjusted analyses (cisatracurium), and one (high-frequency oscillatory ventilation) showed a significant detrimental effect. Across 29 meta-analyses, the most consistent evidence was seen for low tidal volumes and prone positioning in severe ARDS.

CONCLUSIONS

There is limited supportive evidence that specific interventions can decrease mortality in ARDS. While low tidal volumes and prone positioning in severe ARDS seem effective, most sporadic findings of interventions suggesting reduced mortality are not corroborated consistently in large-scale evidence including meta-analyses.

Aerosolized KL4 surfactant improves short-term survival and gas exchange in spontaneously breathing newborn pigs with hydrochloric acid-induced acute lung injury

BACKGROUND

Surfactant therapy may be beneficial in acute lung injury (ALI). In spontaneously breathing newborn pigs with ALI supported with continuous positive airway pressure (CPAP), we evaluated the hypothesis that aerosolized KL4 surfactant (AERO KL4 S) would provide a similar therapeutic effect as intratracheal KL4 surfactant (ETT KL4 S) when compared to controls.

METHODS

We randomized pigs with HCl-induced ALI to: (1) 175 mg/kg KL4 surfactant via endotracheal tube (ETT); (2) AERO KL4 S (22.5 mg/min phospholipid) for 60 min via continuous positive airway pressure (CPAP); or (3) sham procedure on CPAP. We obtained physiologic data and arterial blood gases throughout the 3-hr study. At study end, lungs were excised for analysis of interleukin-8 (IL-8), myeloperoxidase (MPO) levels and histomorphometric data.

RESULTS

Pigs treated with ETT KL4 S and AERO KL4 S had improved survival and sustained pO2 compared to controls. The AERO KL4 S group had higher pH compared to controls. Lung IL-8 levels were lower in the AERO KL4 S group compared to controls. Histomorphometric analysis showed less hemorrhage in the ETT and AERO KL4 S groups compared to controls. The AERO KL4 S group had more open lung units per fixed-field than the ETT KL4 S or controls.

CONCLUSIONS

AERO KL4 S produced similar improvements in survival, physiology, inflammatory markers, and morphology as ETT KL4 S in an ALI model.

The effects of exogenous surfactant administration on ventilation-induced inflammation in mouse models of lung injury

Background

Mechanical ventilation (MV) is an essential supportive therapy for acute lung injury (ALI); however it can also contribute to systemic inflammation. Since pulmonary surfactant has anti-inflammatory properties, the aim of the study was to investigate the effect of exogenous surfactant administration on ventilation-induced systemic inflammation.

Methods

Mice were randomized to receive an intra-tracheal instillation of a natural exogenous surfactant preparation (bLES, 50 mg/kg) or no treatment as a control. MV was then performed using the isolated and perfused mouse lung (IPML) set up. This model allowed for lung perfusion during MV. In experiment 1, mice were exposed to mechanical ventilation only (tidal volume =20 mL/kg, 2 hours). In experiment 2, hydrochloric acid or air was instilled intra-tracheally four hours before applying exogenous surfactant and ventilation (tidal volume =5 mL/kg, 2 hours).

Results

For both experiments, exogenous surfactant administration led to increased total and functional surfactant in the treated groups compared to the controls. Exogenous surfactant administration in mice exposed to MV only did not affect peak inspiratory pressure (PIP), lung IL-6 levels and the development of perfusate inflammation compared to non-treated controls. Acid injured mice exposed to conventional MV showed elevated PIP, lung IL-6 and protein levels and greater perfusate inflammation compared to air instilled controls. Instillation of exogenous surfactant did not influence the development of lung injury. Moreover, exogenous surfactant was not effective in reducing the concentration of inflammatory cytokines in the perfusate.

Conclusions

The data indicates that exogenous surfactant did not mitigate ventilation-induced systemic inflammation in our models. Future studies will focus on altering surfactant composition to improve its immuno-modulating activity.

Mechanisms of acute respiratory distress syndrome in children and adults: a review and suggestions for future research

OBJECTIVES

To provide a current overview of the epidemiology and pathophysiology of acute respiratory distress syndrome in adults and children, and to identify research questions that will address the differences between adults and children with acute respiratory distress syndrome.

DATA SOURCES

Narrative literature review and author-generated data.

DATA SELECTION

The epidemiology of acute respiratory distress syndrome in adults and children, lung morphogenesis, and postnatal lung growth and development are reviewed. The pathophysiology of acute respiratory distress syndrome is divided into eight categories: alveolar fluid transport, surfactant, innate immunity, apoptosis, coagulation, direct alveolar epithelial injury by bacterial products, ventilator-associated lung injury, and repair.

DATA EXTRACTION AND SYNTHESIS

Epidemiologic data suggest significant differences in the prevalence and mortality of acute respiratory distress syndrome between children and adults. Postnatal lung development continues through attainment of adult height, and there is overlap between the regulation of postnatal lung development and inflammatory, apoptotic, alveolar fluid clearance, and repair mechanisms. Therefore, there is a different biological baseline network of gene and protein expression in children as compared with adults.

CONCLUSIONS

There are significant obstacles to performing research on children with acute respiratory distress syndrome. However, epidemiologic, clinical, and animal studies suggest age-dependent differences in the pathophysiology of acute respiratory distress syndrome. In order to reduce the prevalence and improve the outcome of patients with acute respiratory distress syndrome, translational studies of inflammatory, apoptotic, alveolar fluid clearance, and repair mechanisms are needed. Understanding the differences in pathophysiologic mechanisms in acute respiratory distress syndrome between children and adults should facilitate identification of novel therapeutic interventions to prevent or modulate lung injury and improve lung repair.

Treatment with Fms-like tyrosine kinase 3 ligand reverses lung dendritic cell immunoparalysis and ameliorates zymosan-induced secondary lung injury in mice

Depletion and dysfunction of dendritic cells in the lung can induce local immunoparalysis, which often leads to multiple organ dysfunction syndrome (MODS)-associated mortality. A therapeutic strategy that reverses this immunoparalysis is required. In the present study, we examined the effects of in vivo Fms-like tyrosine kinase 3 ligand (Flt3L) treatment on zymosan (zym)-induced secondary lung injury and dendritic cell (DC) immunoparalysis. BALBc mice were divided randomly into four groups (20/group): (1) sham [intraperitoneal (i.p.) saline] + vehicle [subcutaneous (s.c.) 0·01% mouse serum albumin]; (2) sham + Flt3L (s.c.); (3) zym (i.p.) + vehicle; and (4) zym + Flt3L. Injections were for 9 consecutive days; 12 days later we examined: survival rate (monitored for 12 days); lung tissue histopathology (haematoxylin and eosin staining); plasma indices of lung function (pH, PaO(2) , PaCO(2) , HCO(3) (-) ); DC subsets in lung tissue; and lung DCs production of interleukin (IL)-12p70 and IL-10. Zym administration resulted in increased mortality associated with significant lung histopathological changes and abnormal blood gas indices; however, these pathological changes were ameliorated by Flt3L treatment. Zym injections also resulted in significant reductions in DC subsets recovered from lungs [CD11c(+) major histocompatibility complex (MHC)-II/I-A(d+) , CD11c(+) CD11b(+) and CD11c(+) B220(+) ]. Importantly, in-vivo Flt3L treatment reversed these trends for DC immunoparalysis by increasing the percentages of recovered DC subsets concomitant with increased DC production of IL-12 p70 and decreased IL-10 production. These results suggest that Flt3L may have therapeutic potential for reversing DC immunoparalysis and ameliorating lung injury secondary to MODS.

Pharmacotherapy for acute respiratory distress syndrome

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a continuum of a clinical syndrome of respiratory failure due to refractory hypoxia. Acute respiratory distress syndrome is differentiated from ALI by a greater degree of hypoxemia and is associated with higher morbidity and mortality. The mortality for ARDS ranges from 22-41%, with survivors usually requiring long-term rehabilitation to regain normal physiologic function. Numerous pharmacologic therapies have been studied for prevention and treatment of ARDS; however, studies demonstrating clear clinical benefit for ARDS-related mortality and morbidity are limited. In this focused review, controversial pharmacologic therapies that have demonstrated, at minimum, a modest clinical benefit are discussed. Three pharmacologic treatment strategies are reviewed in detail: corticosteroids, fluid management, and neuromuscular blocking agents. Use of corticosteroids to attenuate inflammation remains controversial. Available evidence does not support early administration of corticosteroids. Additionally, administration after 14 days of disease onset is strongly discouraged. A liberal fluid strategy during the early phase of comorbid septic shock, balanced with a conservative fluid strategy in patients with ALI or ARDS during the postresuscitation phase, is the optimum approach for fluid management. Available evidence supports an early, short course of continuous-infusion cisatracurium in patients presenting with severe ARDS. Evidence of safe and effective pharmacologic therapies for ARDS is limited, and clinicians must be knowledgeable about the areas of controversies to determine application to patient care.

Therapeutic effects of inhaling aerosolized surfactant alone or with dexamethasone generated by a novel noninvasive apparatus on acute lung injury in rats

BACKGROUND

Pulmonary surfactant (PS) administration has been attempted for the treatment of adults with acute lung injury (ALI)/adult respiratory distress syndrome. Aerosolized surfactants inhaled by spontaneous breathing may be an effective method of surfactant-based therapies. Using a noninvasive apparatus, we evaluated the therapeutic effects of aerosolized PS alone or together with dexamethasone (Dex) on a rat model of ALI.

METHODS

Severe ALI was induced by intravenous injection of 20% oleic acid (0.2 mL/kg) into adult Sprague-Dawley rats. Animals were divided into eight groups: sham (n = 10); model (injury only, n = 10); normal saline (NS) aerosol driven by compressed air (air-NS, n = 13); PS aerosol driven by compressed air (air-PS, n = 13); NS aerosol driven by O2 (O2-NS, n = 13); PS aerosol driven by O2 (O2-PS, n = 13); Dex aerosol driven by O2 (O2-Dex, n = 13); and PS and Dex aerosol driven by O2 (O2-PS-Dex, n = 13). Blood gases, breathing rate, lung index, total protein, and proinflammatory cytokines (tumor necrosis factor-α, interleukin 1β, interleukin 6) in the bronchoalveolar lavage fluid (BALF), and lung histology were examined.

RESULTS

Animals treated with air-PS for 20 minutes had significantly improved lung function, reduced pulmonary edema, decreased concentration of total protein and proinflammatory cytokines in BALF, ameliorated lung injury, and improved animal survival. In the O2-PS group, the breathing rates and lung injury scores were significantly lower than that of the air-PS group. In the O2-PS-Dex group, lung edema, total protein, and inflammatory cytokines in BALF were significantly reduced in comparison with the O2-PS group.

CONCLUSION

Inhalation of aerosolized PS generated by the noninvasive apparatus could significantly reduce lung injury, while using oxygen line available in the clinical wards to generate PS aerosol is more convenient and adds further benefits. This method can also be used to deliver Dex and other therapeutic agents to ameliorate lung injury.

Exogenous pulmonary surfactant for acute respiratory distress syndrome in adults: A systematic review and meta-analysis

Acute respiratory distress syndrome (ARDS) is often characterized by reduced lung compliance, which suggests dysfunction of the endogenous surfactant system. The effectiveness of exogenous surfactants as replacements for the endogenous system in the treatment of ARDS in adults was assessed. Randomized controlled trials from Medline (1950–2011), Embase (1989–2011), the Cochrane Database of Systematic Reviews and the Cochrane Central Register of Controlled Trials (1994–2011) were analyzed. Two reviewers identified trials for inclusion and the results of included trials were quantitatively pooled with a fixed-effects model. Seven trials (2,144 patients) with good methodological quality were included in the analysis. Pulmonary surfactant treatment was not associated with reduced mortality [relative risk (RR), 1.00; 95% confidence interval (CI) 0.89–1.12]. Subgroup analysis revealed no reduced mortality for various surfactant types. Heterogeneity was not significant in the primary outcome analysis (I²=0%). There was no evidence of publication bias. Oxygenation, ventilation-free days, duration of ventilation and APACHE II scores did not undergo pooled analysis due to insufficient data. Exogenous surfactant did not reduce mortality in adults with ARDS in our meta-analysis, and we cannot accurately define whether exogenous surfactant has an effect on oxygenation from the included studies.